Therapy For Triple-negative Breast Cancer Research Articles

Abstract PO1-17-02: Real-world outcomes of systemic therapy for advanced triple-negative breast cancer: a tertiary centre experience

Abstract Background Despite recent therapeutic developments for advanced triple-negative breast cancer (aTNBC), outcomes are still suboptimal for a significant proportion of patients. Clinical trials focus on a single line of therapy and do not examine outcomes across the whole treatment pathway involving multiple lines of therapy and may not be representative of outcomes in the real world. We evaluated the efficacy of sequential lines of systemic therapies (SACT) in patients with aTNBC treated at our Institution. Methods We conducted a retrospective analysis of patients with aTNBC who commenced SACT at our Institution between 1/12/2011 and 31/12/2020. Patients’ demographics and tumour characteristics were recorded, along with SACT regime used and treatment outcomes. Median overall survival (mOS) was calculated, as was overall response rate (ORR), median progression survival (mPFS) for each line of therapy. Results In total, 239 patients were eligible for inclusion, with a median age of 55 years at diagnosis of aTNBC (range 26-91). Of these, 65 (27.2%) were ≥65. Two hundred and eleven patients (88.3%) had ECOG performance status (PS) 0 or 1 at first-line SACT initiation. Thirty-two (13.4%) had de-novo aTNBC. Of those with recurrent disease (N=207), 110 (53.1%) received neoadjuvant treatment in the early disease setting. Of these, only 8 (7.3%) achieved pathological complete response. In the recurrent disease cohort, 75 (36.2%) had a disease-free interval (DFI) ≤12 months. There was visceral involvement in 144 (60.2%) patients and 10 (4.2%) had bone only disease. The most common histology was invasive ductal (n=142, 59.4%) at metastatic biopsy and 30 (12.6%) were germline BRCA 1/2 mutation carriers. Number of SACT lines ranged from 1 to 8, with most patients (n=140, 58.6%) receiving 1 to 2 lines of treatment only; with 99 (41.4%) receiving ≥3 lines, 60 (25.1%) ≥4 lines and 36 (15.1%) ≥5 lines. Fluoropyrimidines was most commonly used drug class in 1st and in 2nd lines (40.6% and 32.7%, respectively). Eribulin was the most common choice in 3rd line and 4th lines (37.4% and 30%, respectively). Check-point inhibitor-based therapy was used in 6.3% of patients in 1st line, 2.5% in 2nd line and 3.0% in 3rd line. Overall, 25.5% (n=61) of patients were enrolled onto clinical trials. Clinical trial enrolment was most common in third-line (12.1%, n=12). ORR and mPFS were 42.2% (95% CI 35.7-49) and 3.7 months (95% CI 3.0-5.0) respectively in 1st line, 38.5% (95% CI 30.8-46.6) and 3.5 months (95% CI 2.8-4.0) in 2nd line, 30.2% (95% CI 21.3-40.4) and 2.5 months (95% CI 2.1-3.0) in 3rd line, 23.7% (95% CI 13.6-36.6) and 2.1 months (95% CI 2.0-2.8) in 4th line Patients with a DFI >12 months had a longer mPFS compared to patient with DFI ≤12 months at 5.4 (95% CI 3.7– 6.4) and 2.75 (95% CI 2.2– 3.6) months, respectively (P=0.009). At the censor date 18 patients (7.5%) were still alive and mOS was 11.8 months. Conclusions Our real-world data shows that over half of patients only receive one or two lines of systemic therapy for aTNBC, emphasising the importance of therapy choice in the early line setting for aTNBC. These data are important to inform decision-making, discussions with patients and considerations of clinical trials. Table 1. ORR and PFS to First, second, third and fourth-line systemic treatment. Citation Format: Shuai Zhang, Matilde Coriano, Colm Mac Eochagain, Dorothy Yang, Daniel Yiu, Alistair Ring, Nicolo M.L. Battisti. Real-world outcomes of systemic therapy for advanced triple-negative breast cancer: a tertiary centre experience [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-17-02.

Abstract PO3-06-13: A novel stable 6-aryl-2-benzoyl-pyridine colchicine-binding site inhibitor targeting microtubules (60c) is effective against taxane-resistant, metastatic breast cancer

Abstract Background: Improving survival for patients diagnosed with metastatic disease and treating spontaneous chemoresistance remain major clinical challenges in treating breast cancer. Triple negative breast cancer (TNBC), characterized by a lack of therapeutically targetable receptors (ER/PR/HER2), is an aggressive subtype of breast cancer. TNBC therapy relies on a combination of systemically administered chemotherapies, including microtubule-targeting agents (MTAs) like paclitaxel (taxane class) or eribulin (vinca class); however, there are currently no FDA approved MTAs that bind to the colchicine-binding site. Approximately 70% of patients who initially respond to paclitaxel, a first-line MTA, will develop taxane resistance (TxR) within 6 months. We have previously reported that an orally bioavailable colchicine-binding site inhibitor (CBSI), sabizabulin (formerly known as Veru-111), not only inhibits TNBC tumor progression but also treats pre-established metastatic disease in a taxane-refractory PDX model, HCI-10-Luc2. Sabizabulin is currently in phase II/III trials for advanced prostate cancer. To further improve potency and metabolic stability, we created next-generation derivatives of the sabizabulin scaffold, including 60c. Results: 60c shows improved potency compared to sabizabulin against taxane-sensitive and TxR TNBC models, inhibiting proliferation and clonogenicity at low nanomolar concentrations, and inducing apoptosis in a dose-dependent manner. In vivo, 60c therapy significantly suppressed primary tumor growth and lung metastasis in an orthotopic MDA-MB-231-TxR xenograft model without gross toxicity, and with equivalent efficacy to combrestatin A4 phosphate (CA-4P), another CBSI in clinical trials. In the taxane-refractory HCI-10-Luc2 PDX model, 60c significantly suppressed both the growth of the primary tumor (by ~3.5 fold) and the expansion of pre-established axillary metastases (by ~26 fold) whereas paclitaxel had no effect. Analysis of total photon flux of organs excised at study endpoint showed that 60c had distinct anti-metastatic tropism as compared to sabizabulin. Whereas 60c completely suppressed metastases to the spleen (0/9 mice had signal), and significantly reduced metastatic burden in the leg bones (only 3/9 mice had signal) and in the kidney (only 2/9 mice had signal), 60c had no statistically significant effect on liver metastases. In contrast, we had previously reported that sabizabulin strongly repressed liver metastases in the same PDX model (0 mice with detectable liver metastases), with less potent effects on bone. Unlike 60c, sabizabulin showed no improvement relative to the vehicle control for spleen and kidney metastases. Together, our data positions 60c as a promising candidate for TNBC therapy, particularly for patients with TxR disease. Our results also suggest that different CBSI scaffolds may preferentially inhibit metastasis to specific organs, which requires further investigation. Citation Format: Damilola Oluwalana, Kelli Hartman, Raisa Krutilina, Hao Chen, Hilaire Playa, Shanshan Deng, Deanna Parke, Duane Miller, Tiffany Seagroves, Wei Li. A novel stable 6-aryl-2-benzoyl-pyridine colchicine-binding site inhibitor targeting microtubules (60c) is effective against taxane-resistant, metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-06-13.

Abstract PO3-25-10: Selective and Effective Targeting of Triple-Negative Breast Cancer by CMPD1: Inhibition of MAP kinase-activated protein kinase 2 and Microtubule Dynamics

Abstract Background: Microtubule-targeting agents (MTAs) have been widely utilized in cancer treatment, but the development of novel MTAs has faced limitations. CMPD1, a highly selective inhibitor of MAP kinase-activated protein kinase 2 (MK2) with dual functions as a microtubule inhibitor, shows promise as a targeted therapy for triple-negative breast cancer (TNBC). This study aimed to investigate the effects of CMPD1, targeting MK2 and acting as a microtubule inhibitor, on cell cycle progression, microtubule dynamics, and TNBC-related processes. Methods: CMPD1 was evaluated in non-transformed retinal pigment epithelial cells (RPE1) and TNBC cell lines, including MDA-MB-231 and MDA-MB-468 cells. Time-lapse microscopy and immunofluorescence staining were employed to observe the effects of CMPD1 on mitotic progression, cellular morphology, activation of the spindle assembly checkpoint (SAC), and microtubule dynamics. Anchorage-independent growth assays and in vivo studies using a TNBC xenograft model were performed to assess the impact of CMPD1 on colony formation, tumor growth, and metastasis. Results: CMPD1 treatment induced prometaphase arrest and mitotic slippage in both non-transformed and TNBC cells. This arrest was associated with SAC activation, evidenced by increased levels of Mad1 at kinetochores. CMPD1 exhibited robust microtubule depolymerization, primarily targeting microtubule plus-ends and inhibiting microtubule polymerization in vitro. Furthermore, CMPD1 disrupted the organization of the microtubule network in interphase cells and perturbed the mitotic spindle during mitosis. Additionally, CMPD1 treatment resulted in the formation of cytoplasmic protrusions, membrane deformations, and dynamic movement of clustered mitotic chromosomes. These morphological alterations were indicative of the impact of CMPD1 on cellular structures and processes during mitosis. Notably, CMPD1 demonstrated significant efficacy in inhibiting anchorage-independent growth in TNBC cells, highlighting its potential as an anti-TNBC agent. In the TNBC xenograft model, CMPD1 exhibited superior anti-tumor activity compared to the standard chemotherapeutic agent Taxol. Tumor growth was markedly suppressed, and the formation of metastatic lesions was significantly reduced upon CMPD1 treatment. Furthermore, CMPD1 treatment effectively inhibited TNBC cell migration and invasion, likely through its modulation of microtubule dynamics. The disruption of microtubule dynamics by CMPD1 impaired the ability of TNBC cells to migrate and invade surrounding tissues, which are crucial processes in cancer metastasis. Importantly, CMPD1 showed high selectivity for TNBC cells, exerting minimal cytotoxic effects on normal cells, and could be efficiently washed out. This selectivity and washout ability enhance its potential as a targeted therapeutic agent for TNBC treatment. Conclusions: CMPD1, a highly selective MK2 inhibitor and microtubule inhibitor, exerts profound effects on cell cycle progression, microtubule dynamics, and TNBC-related processes. It induces prometaphase arrest, mitotic slippage, and microtubule depolymerization, resulting in altered cellular morphology. CMPD1 displays high selectivity for TNBC cells, while sparing normal cells and allowing efficient washout, making it a promising therapeutic agent for TNBC treatment. Its inhibition of anchorage-independent growth, suppression of tumor growth in vivo, and ability to impair TNBC cell migration and invasion further underscore its potential as a targeted anti-TNBC therapy. Citation Format: Mamoru Takada, Yu-Chia Chen, Yu Muhan, Hideyuki Yamada, Junta Sakakibara, Hiroshi Fujimoto, Takeshi Nagashima, Masayuki Otsuka, Motoki Takaku, Aussie Suzuki. Selective and Effective Targeting of Triple-Negative Breast Cancer by CMPD1: Inhibition of MAP kinase-activated protein kinase 2 and Microtubule Dynamics [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-25-10.

Abstract PO2-15-07: HER2DX genomic assay in triple-negative breast cancer (TNBC) patients treated with 12-weeks of neoadjuvant chemotherapy: a correlative analysis from WSG-ADAPT-TN phase II trial

Abstract HER2DX genomic assay in triple-negative breast cancer (TNBC) patients treated with 12-weeks of neoadjuvant chemotherapy: a correlative analysis from WSG-ADAPT-TN phase II trial Background: Biomarkers for de-escalation and escalation of systemic therapy in early-stage TNBC are needed. HER2DX is a standardized prognostic (risk-score) and predictive (pathological complete response [pCR]-score) assay based on clinical and gene expression-based data. Here we aimed to test the value of HER2DX assay in early TNBC. Methods: Standardized HER2DX was evaluated centrally using RNA from baseline FFPE tumor biopsies from the WSG-ADAPT-TN study (NCT01815242), a multicenter phase II trial that randomized 336 patients with stage I–III early TNBC to 12-weeks of nab-paclitaxel 125 mg/m2 plus gemcitabine 1000 mg/m2 d1,8 every 3 weeks (arm A) versus nab-paclitaxel 125 mg/m2 plus carboplatin AUC2 day 1,8 every 3 weeks (arm B). The primary aim was to test the ability of HER2DX pCR and risk-score models to predict pCR (ypT0/isN0) and survival endpoints, respectively, such as invasive disease-free survival (iDFS), distant disease-free survival (DDFS) and overall survival (OS). Secondary objectives were to assess the association of the i) HER2DX immune signature score and ii) percentage (%) of stromal tumor infiltrating lymphocytes (sTILs) with efficacy endpoints. Uni- and multi-variable logistic regression and Cox models tested the association of each variable with each endpoint. Results: HER2DX was evaluated in 126 (37.5%) baseline pre-treatment tumors. Mean age was 52.1 (range 26-76). cT1 represented 40.5% of cases and 72.2% were cN0. Overall, pCR rate was 34.1% (95%CI 26.1 – 43.2) and median follow-up was 5.0 years. Median sTILs at baseline was 31.6% (range 0-90) and moderately correlated with the IGG signature (coefficient=0.57). The % of HER2DX high-, medium- and low-pCR groups was 41.3%, 47.6% and 11.1%, respectively. HER2DX pCR score (as a continuous variable) was significantly associated with pCR in univariate (odds ratio [OR per 10-unit increase]=1.31, 1.06-1.64, p=0.016) and after adjusting by treatment arm (OR=1.31, 1.06-1.65, p=0.015). Overall, the pCR rates in HER2DX pCR-high, -medium and -low groups were 46.2%, 26.7% and 21.4%, respectively (high vs medium/low OR=2.48, 1.17-5.34, p=0.018). In arm B (n=51), the pCR rates in HER2DX pCR-high, -medium and -low groups were 47.8%, 25.0% and 0.0% respectively (high vs medium/low OR=3.36, 1.02-12.0, p=0.051). In terms of the risk-score, the % of HER2DX low-risk and high-risk groups was 60.3% and 39.7%, respectively. HER2DX risk score as a continuous variable was significantly associated with iDFS, DDFS and OS (p< 0.001 in all univariate analysis), and after adjusting by variables such as arm and pCR status (all p< 0.05). sTILs were not associated with any survival endpoint (all p >0.35). The HER2DX immune signature was significantly associated with iDFS (p=0.012), DDFS (p=0.022) and OS (p=0.012). Conclusion: The HER2DX genomic test in TNBC provides valuable insights into the response and survival following neoadjuvant taxane-based chemotherapy in the absence of immunotherapy. The development of a tailored genomic assay for TNBC is currently in progress. Citation Format: Oleg Gluz, Fara Brasó-Maristany, Ulrike Nitz, Laia Paré, Matthias Christgen, Guillermo Villacampa, Benedetta Conte, Sherko Kuemmel, Ronald Kates, Cornelia Kolberg-Liedtke, Eva-Maria Grischke, Helmut Forstbauer, Michael Braun, Mathias Warm, John Hackmann, Christoph Uleer, Bahriye Aktas, Claudia Schumacher, Ana Vivancos, Rachel Wuerstlein, Joel S. Parker, Monika Graeser, Charles M. Perou, Christine zu Eulenburg, Patricia Villagrasa, Hans-Heinrich Kreipe, Aleix Prat, Nadia Harbeck. HER2DX genomic assay in triple-negative breast cancer (TNBC) patients treated with 12-weeks of neoadjuvant chemotherapy: a correlative analysis from WSG-ADAPT-TN phase II trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-15-07.

Abstract PO2-15-08: Exploring Essential Immune Genes Linked to Pathological Complete Response and Survival in Early-Stage Triple-Negative Breast Cancer (TNBC) after Chemotherapy Treatment

Abstract Background: De-escalation and escalation of systemic therapy in early-stage TNBC will require the implementation of biomarkers to guide therapy. To date, high expression of a variety of immune genes has been associated with higher pathological complete response (pCR) rates following neoadjuvant chemotherapy or with improved survival, or both, in early-stage TNBC. However, it is currently unknown which are the key genes influencing survival (i.e., the Core Immune Genes [CIG]) and if combinations of these genes can improve their association with both clinical endpoints. Methods: The expression of up to 185 genes was evaluated on pre-treatment tumor biopsies from 3 independent publicly available datasets of early-stage TNBC: CALGB40603 (n=388) (NCT00861705), BrighTNess (n=482) (NCT02032277), and SCAN-B (n=498). Patients in CALGB40603 and BrighTNess were treated with neoadjuvant chemotherapy-based therapy and had response data. Patients in CALGB40603 and SCAN-B had survival outcome data (event-free survival [EFS] or relapse-free interval [RFi]). Each individual gene was associated with each clinical endpoint within each dataset using Cox model and logistic regression analyses, adjusting for treatment arm. Genes found in common across datasets were selected as CIG, except for PDCD1, which was not available in BrighTNess. Using the CIGs, we evaluated whether combinations of 2 genes enhance their association with each clinical endpoint using different methods: adding, subtracting, multiplying, and ratio. Likelihood ratio testing was used to evaluate the added contribution of each gene in 2 combined cohorts evaluating pCR (i.e., CALGB40603 and BrighTNess) and survival (i.e., CALGB40603 and SCAN-B). Results: 10 CIGs related to B-cells and T-cells (i.e., IRF4, LAX1, POU2AF1, CD274, CD79A, TNFRSF17, PIM2, PDCD1, CXCR6, and SLAMF1) were associated with higher pCR rates and improved survival outcome across datasets. Of note, 5 (50%) genes are known components of the 14-gene immunoglobulin/B-cell (IGG) signature. The correlation coefficient among the 10 CIG genes was 0.63 (moderate). In general, the sum of 2 CIGs provided more prognostic information than a single gene (p< 0.001). Specifically, the sum of 2 CIGs provides more prognostic information than a single gene in 30 of 45 (66.6%) cases. Two-gene subtraction, multiplication or ratio decreased the amount of prognostic information (p< 0.001). The top 10 2-gene CIGs associated with prognosis (p< 0.001) were CD274_TNFRSF17, IRF4_CD274, PDCD1_TNFRSF17, CD79A_CD274, CD274_POU2AF1, CXCR6_TNFRSF17, LAX1_TNFRSF17, SLAMF1_TNFRSF17, CD274_LAX1 and CD79A_CXCR6. In general, the sum of 2 CIGs provided more information about pCR than a single gene (p< 0.001). Specifically, the sum of 2 CIGs provided numerically more information about pCR than 1 gene in 17 of 36 (47.2%) cases. Two-gene subtraction, multiplication or ratio decreased the amount of information about pCR (p< 0.001). The top 10 2-gene CIGs associated with pCR were CD274_PIM2, CD274_POU2AF1, CXCR6_PIM2, CD274_CXCR6, IRF4_CD274, CXCR6_POU2AF1, CD274_LAX1, IRF4_CXCR6, CXCR6_LAX1, and POU2AF1_SLAMF1. Conclusion: The expression of CIGs associated with B-cell and T-cell adaptive immune response is closely linked to pCR and survival outcomes following (neo)adjuvant chemotherapy. When combining the expression of 2 specific CIGs through addition, we found that this method provides more informative insights into pCR and survival outcomes compared to other combination methods. This approach enhances the predictive power of CIGs, enabling a better understanding of treatment response and patient prognosis, ultimately contributing to improved clinical decision-making and patient outcomes. Citation Format: Fara Brasó-Maristany, Laia Paré, Benedetta Conte, Laura Angelats, Ana Vivancos, Joel S Parker, Charles M. Perou, Patricia Villagrasa, Aleix Prat. Exploring Essential Immune Genes Linked to Pathological Complete Response and Survival in Early-Stage Triple-Negative Breast Cancer (TNBC) after Chemotherapy Treatment [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-15-08.

Abstract PO3-26-10: Small molecule inhibitor of PELP1 exhibit cytotoxic effects on breast cancer cells by blocking ribosome biogenesis

Abstract Introduction: Breast cancer (BC) is the second-leading cause of cancer-related deaths in women. Despite responsive to endocrine therapy, a sizeable portion of estrogen receptor positive (ER+) BC goes on to develop therapy-resistant breast cancer (TR-BC). Furthermore, triple-negative breast cancer (TNBC) has a more aggressive clinical course with fewer targeted therapeutic options. The development of more effective therapies for TR-BC or TNBC represent an unmet need. Excessive ribosome biogenesis has recently been linked to BC progression, and resistance to therapy. Oncogene PELP1, which is required for ribosome biogenesis, is frequently dysregulated in BC and serves as a prognostic factor for poor BC survival and therapy resistance. We recently identified SMIP34 as a PELP1 small molecule inhibitor of its kind and it is effective against both TR-BC and TNBC. The objective of this study is to determine the mechanisms by which SMIP34 exhibit cytotoxic effects on BC cells. Methods: We have used multiple ER+, therapy resistant and TNBC models in cell viability, and apoptosis assays. Modelling studies were done based on Cryo-EM structure of the WDR18/PELP1 Rix1 complex (PDB code 7UWF). Biochemical assays include immune precipitation, reporter assays, GST pulldown, and Western Blotting. SMIP34 effect on protein synthesis was measured by using Western blot of puromycin treated total lysates for puromycinylated protein content. SMIP34 effect on protein synthesis assessed using Cayman’s Protein Synthesis Assay Kit. Ribosome biogenesis in SMIP34 treated cells was monitored using confocal microscopy using rpS6 antibody. Results: In in vitro cell based assays, SMIP34 was highly effective in reducing the cell viability, reducing colony formation and inducing apoptosis of ER+, endocrine therapy resistant, and TNBC model cells. PELP1 homodimer has recently been predicated to act as the core of the WDR18/PELP1 assembly. Our biochemical assay results suggest that SMIP34 binds to the same region involved in the PELP1 homodimerization and disrupts the formation of PELP1 homodimer and subsequently blocks the formation of WDR18/PELP1 Rix1 complex. Modeling studies predicted that altering the conformation of PELP1 aa 696-720 loop by SMIP34 binding may influence the conformation of the following C-terminal region, which may disturb the interaction of other PELP1 partners such as SENP3 and TEX10. Accordingly, the results from immunoprecipitation experiments demonstrated decreased association of Rix1 complex proteins WDR18, TEX10, and SENP3 with PELP1 under conditions of SMIP34 treatment. Further, Western blotting analysis confirmed that SMIP34 treatment decreased levels of PELP1 and its complex proteins, such as WDR18, TEX10, LAS1L, and SENP3. SMIP34 significantly reduced ribosomal biogenesis in a dose dependent manner. Additionally, puromycin labelling experiments confirmed a dose dependent decrease in new protein synthesis upon SMIP34 administration. Data from the DepMap database analysis revealed that PELP1 is required for cancer cell survival. Additionally, analysis of TCGA breast cancer datasets revealed that PELP1 expression is positively correlated with WDR18, TEX10, LAS1L, and SENP3. In in vivo xenograft assays and ex vivo explant assays using tumor tissue, SMIP34 strongly inhibited the growth of ER+, endocrine treatment resistant, and TNBC model cells. Conclusion: These findings provide solid evidence that the Rix1 complex, which is required for ribosomes production, is disturbed by SMIP34 binding to PELP1. SMIP34 represents a new therapeutic for the treatment of both ER+ and TNBC breast cancer. Supported by VA grant 1 I01 BX004545-01A1. Citation Format: Xue Yang, Khaled Mohamed Nassar, Uday Pratap, Rahul Gopalam, Behnam Ebrahimi, Durga Meenakshi Panneerdoss, Xiaonan Li, Yaxia Yuan, Daohong Zhou, Gangadhara R. Sareddy, Rajeshwar R. Tekmal, Manjeet Rao, Suryavathi Viswanadhapalli, Ratna Vadlamudi. Small molecule inhibitor of PELP1 exhibit cytotoxic effects on breast cancer cells by blocking ribosome biogenesis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-26-10.

Abstract PS12-06: A phase 2 study of abemaciclib monotherapy for patients with retinoblastoma-positive (Rb+), triple-negative metastatic breast cancer

Abstract Background: Cyclin-dependent kinase (CDK) 4/6 inhibitors can significantly extend survival when given in combination with endocrine therapy as treatment for hormone receptor-positive metastatic breast cancer. Preclinical studies suggest CDK4/6 inhibitor monotherapy might also be effective in a subset of triple-negative breast cancers (TNBCs), including those that express a functional retinoblastoma (RB) protein and/or those of the Luminal Androgen Receptor (LAR) subtype. Currently, the clinical activity of CDK4/6 inhibitor therapy in TNBC has not been reported. Methods: We conducted a single-arm phase II study of abemaciclib monotherapy in patients with locally advanced or metastatic TNBC. Key eligibility criteria included: (i) Measurable disease by RECIST 1.1; (ii) Between 1-3 prior lines of systemic therapy for advanced TNBC; (iii) RB-positive tumor (defined as ≥ 50% of tumor cells staining positive for RB by immunohistochemistry [archival or fresh sample] on central testing); (iv) ECOG PS 0/1. Patients were treated with abemaciclib 200 mg orally (28-day cycles) twice daily until disease progression, unacceptable toxicity, withdrawal of consent, or death. Tumor biopsies were mandatory at baseline and C2D1 if tumor tissue was safely accessible. The primary outcome was objective response rate (ORR). Key secondary endpoints included progression-free survival (PFS), overall survival (OS), clinical benefit rate (CBR: CR + PR + SD ≥ 24 weeks), and safety and tolerability. The study had a two-stage design. Thirteen patients were enrolled in the first stage, with the plan to enrol a further 25 patients if at least one objective response was observed. Results: One unconfirmed partial response was observed in stage 1, and a total of 27 patients were enrolled before the trial was closed early due to slow accrual. The median age was 61 years and patients had received a median of 2 prior lines of systemic therapy for metastatic disease. Twelve patients had received prior immunotherapy. After a median follow-up of 28.5 months, the confirmed ORR was 0% and the CBR was 15%, with 4 of 27 patients experiencing stable disease for ≥ 24 weeks. The median PFS was 1.94 months (95% CI: 1.8 – 11.5 months), and the median OS was 8.44 months (95% CI: 4.6 – 15.6 months). There was no significant difference in PFS or OS between patients with PD-L1-positive versus PD-L1-negative disease, or Androgen Receptor (AR) positive versus negative tumors by immunohistochemistry. The most common adverse events of grade 2 or higher were diarrhea (41%), neutropenia (41%), anemia (30%), and nausea (30%). RNA-sequencing of baseline biopsies has been performed to identify biomarkers associated with clinical benefit, and results will be presented at the meeting. Conclusions: Abemaciclib monotherapy did not show clinical activity in patients with Rb+ metastatic TNBC. This finding suggests that future trials of CDK4/6 inhibition as monotherapy in TNBC are not warranted. Citation Format: Shom Goel, Bojana Jovanović, Xiangying Chu, Melissa Hughes, Ayesha Mohammed-Abreu, Julie Kasparian, Timothy Erick, Molly DiLullo, Eileen Wrabel, Rinath Jeselsohn, Nabihah Tayob, Stuart Schnitt, Nancy Lin, Sara Tolaney. A phase 2 study of abemaciclib monotherapy for patients with retinoblastoma-positive (Rb+), triple-negative metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS12-06.

Abstract PO3-06-11: Undated analyses from a Phase Ib open-label study of Pucotenlimab (HX008) in combination with gemcitabine and cisplatin as first-line treatment of metastatic triple-negative breast cancer

Abstract Background: Gemcitabine plus cisplatin (GP) therapy war preferred in China as the first-line therapy for metastatic triple-negative breast cancer (mTNBC), with a median progression-free survival (PFS) of 7.73 months, and a median overall survival (OS) of 19.37 months [1]. Pucotenlimab (HX008) is a novel humanized IgG4 anti-PD-1 monoclonal antibody with an engineered Fc domain. Preliminary results from the phase 1b trial [2] have shown that HX008 combined with GP has a manageable safety profile and demonstrates promising antitumor activity in patients (pts) with mTNBC. Here, we present the updated results from the long-term survival analysis. Methods: Eligible subjects were those who were treatment-naïve mTNBC patients and had measurable lesion. Participants received HX008 at a dose of 3 mg/kg every 3 weeks in combination with chemotherapy (gemcitabine + cisplatin) for 6 cycles and maintained with HX008 until disease progression or unacceptable toxicity occurred. The primary endpoints included overall response rate (ORR) and safety, and the secondary endpoints included duration of response (DoR), PFS, and OS. Results: Between July 2019 and March 2020, a total of 31 pts were enrolled in this study. The median age of patients was 50 years (range 29–69). By the cut-off date (April 24th, 2023), the median follow-up period was 20.7 m (IQR: 12.2, 25.6). The confirmed ORR was consistent with the previously reported data and remains at 74.2% (95% CI: 55.4%, 88.1%). The median PFS was 9.0 months (95% CI, 7.3, 9.3). The median DoR was 7.3 months (95% CI, 5.0, 9.8). The OS was immature, with the result of 23.1 months (95% CI, 13.4, NE), while the 12-m, 24-m and 36-m OS rate was 77.4% (95%CI: 64.0%, 93.6%), 42.7% (95%CI: 28.0%, 65.3%), and 24.4% (95%CI: 11.3%, 52.7%), respectively. The most common grade 3 or 4 treatment-related adverse events included neutropenia (71.0%), leukopenia (45.2%), anemia (38.7%), and thrombocytopenia (32.3%). There was no treatment-related death and no new safety signals were identified. Conclusion: The combination therapy of HX008 plus GP demonstrates favorable clinical efficacy with a manageable safety profile in pts with mTNBC. The combination therapy led to a longer PFS and OS than GP therapy reported previously, regardless of PD-L1 status. The safety profile was consistent with the known toxic effects of each agent. In this updated analysis, no new safety signals were identified. Clinical trial information: NCT04750382

Abstract PO1-16-04: Targeting PKMYT1 Kinase as a Therapeutic Strategy for Treatment of Triple Negative Breast Cancer with Low Molecular Weight Cyclin E (LMW-E) Expression

Abstract Purpose: Low molecular weight isoforms of cyclin E (LMW-E) have been implicated in various human cancers, including triple negative breast cancer (TNBC), and are associated with a poor prognosis. However, targeted therapies for TNBC based on biomarkers are currently lacking. This study aims to investigate LMW-E as a potential therapeutic target in TNBC and evaluate the efficacy of RP-6306, a selective inhibitor of the Protein Kinase, Membrane Associated Tyrosine/Threonine 1 (PKMYT1), in LMW-E-positive breast tumors. Experimental Design: Immunohistochemical (IHC) analysis was performed on pre-treatment tumor specimens from TNBC patients (n=36) to assess the correlation between LMW-E expression, CDK1 phosphorylation at Threonine 14 (pT14), and pathologic complete response to neoadjuvant chemotherapy. LMW-E inducible human mammary epithelial cells (hMEC) and breast cancer cell lines were used to investigate the regulatory effect of LMW-E on PKMYT1, the kinase responsible for CDK1 phosphorylation at T14, and the response to RP-6306, a first in-class and selective inhibitor of PKMYT1. Patient-derived xenograft (PDX) models and transgenic mouse mammary tumor virus (MMTV) models of TNBC expressing human LMW-E (hLMW-E) were also utilized to assess LMW-E as a biomarker for predicting response to RP-6306. Results. Analysis of TNBC tumor biopsies revealed a significant positive correlation between LMW-E expression and CDK1 pT14, and both biomarkers were associated with a lack of pathological complete response to neoadjuvant chemotherapy. In vitro results using LMW-E inducible hMECs and breast cancer cell lines demonstrated that LMW-E up-regulates PKMYT1 and CDK1 pT14, acting as a PKMYT1 binding protein and enhancing PKMYT1 protein stability. High LMW-E protein levels predicted a favorable response to RP-6306, resulting in the accumulation of sub-G1 and polyploid cells, decreased tolerance to replication stress, increased DNA damage, chromosomal breakage, and apoptosis. In vivo treatment of TNBC PDX models and hLMW-E transgenic tumors with RP-6306 resulted in a significant reduction in tumor volume only in mice harboring high LMW-E tumors, while low cyclin E models showed no response. Immunohistochemical analysis confirmed increased γ-H2AX and decreased CDK1-pT14 and Ki67 levels, indicating the efficacy of RP-6306 in both PDX and transgenic models. Conclusion: This study highlights the regulatory axis from LMW-E to PKMYT1 and its predictive value for pathological complete response in TNBC patients receiving neoadjuvant chemotherapy. The selective PKMYT1 kinase inhibitor RP-6306 consistently induced DNA damage and inhibited tumor growth in in vitro and in vivo pre-clinical breast tumor models. Co-expression of LMW-E and CDK1-pT14 in TNBC can be used to stratify patients whose tumors are likely to respond to RP-6306, emphasizing its therapeutic significance. Citation Format: Mi Li, Amriti Lulla, Cansu Karakas, Spiridon Tsavaschidis, Yan Wang, Tuyen Nguyun, Tuyen Bui, Gary Marshall, Kelly Hunt, Khandan Keyomarsi. Targeting PKMYT1 Kinase as a Therapeutic Strategy for Treatment of Triple Negative Breast Cancer with Low Molecular Weight Cyclin E (LMW-E) Expression [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-16-04.

Abstract PO1-15-08: Genomic characterization of triple-negative breast cancer metastases reveals PKD1 as a novel biomarker for immunotherapy

Abstract Background: While primary triple-negative breast cancer (TNBC) garners significant research attention, the genomic alterations that occur in metastasis remain insufficiently understood, especially within Asian populations. Furthermore, the genomic information obtained from the primary tumor inadequately guides metastatic cancer treatment, highlighting the critical need for in-depth investigations into metastatic TNBC. Methods: We constructed the largest cohort of TNBC metastases (n = 296) among advanced TNBC patients treated at Fudan University Shanghai Cancer Center (FUSCC) between October 2018 and December 2020. Comprehensive DNA sequencing was conducted on the collected metastatic samples to analyze genomic alterations associated with treatment response. The underlying mechanisms of specific biomarkers were also explored. Results: We presented the genomic landscape of 296 TNBC metastases, encompassing mutant genes, mutation sites and copy number variations. Through multidimensional analysis, significant disparities in TNBC were observed between Western and Asian populations, primary and metastatic tumors, as well as different metastatic sites. Notably, our findings underscore the importance of sequencing TNBC metastases to guide precision therapy, which was associated with longer progression-free survival compared to physician-chosen treatments, shedding light on the pivotal clinical value of genomic studies in metastatic settings. Furthermore, efficacy analysis suggested that PKD1 mutations enriched in metastases mediated resistance to immunotherapy. These findings were further validated through three clinical trials (NCT03805399, NCT04129996, and NCT04395989). Mechanistic studies unveiled the involvement of PKD1 in TNBC immune evasion by upregulating CCL2, thereby facilitating the recruitment of M2-type tumor-associated macrophages. Conclusion: Our study emphasizes the critical significance and necessity of genomic profiling of metastases in guiding precision therapy for TNBC. Moreover, our findings reveal PKD1 as a novel and promising biomarker for immunotherapy. Citation Format: Xiu-Zhi Zhu, Yi-Fan Zhou, Yun-Yi Wang, Xiao-Hong Ding, Xi Jin, Zhi-Ming Shao, Yi-Zhou Jiang, Zhong-Hua Wang. Genomic characterization of triple-negative breast cancer metastases reveals PKD1 as a novel biomarker for immunotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-15-08.

Abstract PO2-22-10: Surgical outcomes after neoadjuvant chemotherapy with and without immunotherapy in patients with triple negative breast cancer

Abstract Background: The KEYNOTE-522 trial demonstrated that the addition of neoadjuvant pembrolizumab to neoadjuvant chemotherapy (NAC) for the treatment of early-stage triple negative breast cancer (TNBC) significantly improves rates of both pathologic complete response (pCR) and event-free survival. The impact of adding immunotherapy to NAC on surgical outcomes, however, is unknown. The purpose of this study is to compare 90-day surgical complication rates and timing to subsequent adjuvant therapy of patients undergoing neoadjuvant chemotherapy for stage I-III TNBC with and without immunotherapy. Methods: Patients treated at University of California, Los Angeles with neoadjuvant therapy for TNBC between 2018-2022 were identified retrospectively. Patient comorbidities, tumor characteristics, type of surgery, 90-day postoperative minor and major complications, timing to adjuvant therapy, and oncologic outcomes were reviewed and analyzed. Major complications were defined as those requiring reoperation or hospitalization. Results: A total of 44 patients were included, 15 patients received neoadjuvant chemotherapy with immunotherapy (NAC-I) and 29 patients received neoadjuvant chemotherapy alone (NAC). There was no difference in patient comorbidities between the groups. Compared to the NAC group, significantly more patients in the NAC-I group had stage II or III tumors (58.6% vs. 86.7%, respectively, p=0.028). 73% of patients in the NAC-I group underwent mastectomy compared to only 44% of patients in the NAC group (p=0.111). In total, 23 patients underwent reconstruction with mastectomy, 6 patients underwent immediate DIEP flap (4 in NAC-I group and 2 in NAC group) and 17 underwent immediate tissue expander (7 in NAC-I and 10 in NAC group). 80% of patients in the NAC-I experienced a pCR compared to only 44% in the NAC group (p=0.026). A total of 15 patients (34.1%) experienced surgical complications and there was no significant difference in the complication rate between the groups (p= 0.552). Five patients (33%) in the NAC-I group experienced minor complications of seroma requiring aspiration (n=4), cellulitis requiring antibiotics (n=1), or wound dehiscence requiring local wound care (n=2). No patients in the NAC-I group had major complications. Ten patients (33%) in the NAC group experienced complications, including 6 minor complications and 4 major complications including postoperative bleeding or flap necrosis requiring unplanned return to surgery or hyperbaric oxygen treatment. On multivariable regression analysis, controlling for patient characteristics, tumor stage, and preoperative immunotherapy, only younger age was a statistically significant variable associated with increased risk of surgical complications (p=0.012). Median time to adjuvant therapy, including radiation and/or systemic therapy, was similar between NAC-I and NAC groups, at 32 and 36 days, respectively (p=0.37). In the NAC-I group, 14 patients (93.3%) had adjuvant systemic therapy including pembrolizumab alone (n=12), pembrolizumab with olaparib (n=1) or capecitabine alone (n=1). In the NAC group, 11 patients (37.9%) underwent adjuvant systemic treatment including chemotherapy with either capecitabine (n=1), pembrolizumab (n=1), or olaparib (n=2); or single agent capecitabine (n=6) or olaparib (n=1). Conclusions: Despite patients in the NAC-I group having more advanced stage tumors and undergoing more extensive surgery and reconstruction compared to those in the NAC alone group, a significantly higher rate of surgical complications was not observed in the NAC-I group and there was no significant difference in time to adjuvant therapy between the two groups. Similar to results from the KEYNOTE-522 trial, more patients in the NAC-I group experienced a pCR compared to NAC alone. Larger studies are needed to continue to assess and optimize the surgical safety of neoadjuvant immunotherapy with chemotherapy in patients with TNBC. Citation Format: Anouchka Coste Holt, Maurice Berkowitz, Nicholas McAndrew, Courtney Smith, Jennifer Baker, Nimmi Kapoor. Surgical outcomes after neoadjuvant chemotherapy with and without immunotherapy in patients with triple negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-22-10.

Abstract PS16-01: Comparison of an Atezolizumab monotherapy window followed by Atezolizumab and chemotherapy vs. Atezolizumab and chemotherapy alone in triple negative breast cancer (TNBC) – final analysis of the neoadjuvant neoMono trial

Abstract Background: Improvement of systemic therapy of TNBC still is a medical need. Exploratory data from the neoadjuvant GeparNuevo trial suggested a benefit from an immune checkpoint inhibitor (ICI) monotherapy window in TNBC. The neoMono trial prospectively analyzed whether the addition of a preceding Atezolizumab monotherapy window prior to Atezolizumab and chemotherapy (CTX) improves pCR rates among patients (pts) with early TNBC. In an interim analysis after 100 pCR events, patients with unselected TNBC did not show a significant benefit from an Atezolizumab monotherapy window, while an exploratory analysis suggested a highly clinically relevant benefit among pts with PD-L1 positive TNBC. Here we present the final primary endpoint analysis. Methods: NeoMono is a phase 2 randomized multicenter trial that was planned to recruit a maximum of 458 female and male pts with primary TNBC (defined as ER/PR < 10% and HER2 negative) with tumor stages cT1c – cT4d (cN0 and cN+). As the protocol mandated termination of trial recruitment based on the results of the interim analysis, the final ITT population was limited to 359 pts. PD-L1 status had to be identifiable by central pathology by means of the VENTANA PD-L1 (SP142) assay and was defined by PD-L1 expression on immune cells (IC). Neoadjuvant treatment in both study arms consisted of Atezolizumab 1200 mg every 3 weeks in addition to neoadjuvant CTX (12 x Carboplatin/Paclitaxel q1w followed by 4x Epirubicin/Cyclophosphamide q3w). Combination therapy in arm A was preceded by an Atezolizumab monotherapy window of 840 mg once two weeks prior to initiation of combination therapy, while patients in arm B received no immune monotherapy window. Study goals are to compare the efficacy of neoadjuvant CTX + Atezolizumab with versus without a two-week atezolizumab monotherapy window preceding CTX + ICI (primary endpoint: pCR) and to identify biomarkers for response and resistance through analysis of sequential tissue and liquid biopsies. The neoMono statistical design uses Bayesian posterior probabilities (uniform prior distribution) and logistic regression to analyze the primary endpoint. Results: 180 pts in arm A and 179 in arm B from 34 study sites were included in the final primary endpoint analysis. Demographics and baseline characteristics as well as drug exposure were well-balanced in both arms. Posterior mean pCR rates in the ITT population in study arms A and B were 65.7% (95% high posterior density interval (HPDI): 58.5%, 72.5%) and 69% (62.2%, 75.9%), respectively. In an exploratory analysis stratified by PD-L1 IC status (negative: < 1% versus positive: ≥ 1%), pCR rates in arm A were 91.5% in the PD-L1 IC-positive group and 56.1% in the PD-L1 IC-negative group, the corresponding pCR rates in arm B were 82.2% and 64.5%, respectively. In a multivariate analysis of the ITT population including tumor size, nodal status, tumor grade, age and PD-L1 status, the odds ratio for achieving a pCR was 4.77 (p < 0.001) for PD-L1-positive and 2.36 (p=0.023) for grade 3 tumors. In an exploratory analysis including HER2 status, odds for achieving a pCR were significantly higher for patients with HER2-negative (IHC 0) vs. HER2-low tumors (OR 1.73, p=0.036). No new safety signals were observed. Conclusion: The final primary endpoint analysis of the neoMono trial demonstrated the highest pCR rates ever reported in a phase II/III trial in TNBC. While a significant impact of an ICI monotherapy window on the pCR rate after combination of CTX + ICI in an unselected ITT population could not be demonstrated, neoMono indicates for the first time in a randomized prospective setting that patients with immune active TNBC might derive particular benefit from a preceding ICI monotherapy window. The results of the neoMono trial are mainly justifying the conduction of a confirmative trial in immune active TNBC. However, our results underscore the potential role of pre-therapeutic ICI monotherapy window as part of future therapeutic concepts in TNBC. Citation Format: Hans-Christian Kolberg, Johannes Schumacher, Ramona Erber, Michael Braun, Peter A. Fasching, Eva-Maria Grischke, Christian Schem, Michael P. Lux, Mustafa Deryal, Oliver Hoffmann, Bernhard Heinrich, Georg Kunz, Kristina Lübbe, Petra Krabisch, Arndt Hartmann, Philip Raeth, Sabine Kasimir-Bauer, Cornelia Kolberg-Liedtke. Comparison of an Atezolizumab monotherapy window followed by Atezolizumab and chemotherapy vs. Atezolizumab and chemotherapy alone in triple negative breast cancer (TNBC) – final analysis of the neoadjuvant neoMono trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS16-01.

Quercetin exerts anti-tumor immune mechanism by regulating IL-6/JAK2/STAT3 signaling pathway to deplete Treg cells

Breast cancer is still the leading cause of death among women worldwide. Due to the lack of effective drug targets, triple-negative breast cancer has a worse prognosis and higher mortality compared with other types of breast cancer, and chemotherapy is still the main treatment for triple-negative breast cancer at present. Quercetin (QUE) is a flavonoid compound found in a variety of fruits and vegetables. The mechanism of QUE has been extensively studied, such as prostate cancer, colon cancer, ovarian cancer, etc. However, the anti-tumor immune mechanism of QUE in triple-negative breast cancer remains unclear. Therefore, we assessed the anti-tumor immune effects of QUE on triple-negative breast cancer using both 4T1 cells and a xenograft mouse model of 4T1 cells. In vitro, we examined the inhibitory effects of QUE on 4T1 cells and its molecular mechanisms through MTT, Transwell, ELISA, and Western blotting. In vivo, by establishing a xenograft mouse model, we utilized flow cytometry, immunohistochemistry, ELISA, and Western blotting to evaluate the anti-tumor immune effects of QUE on triple-negative breast cancer. The results indicate that QUE inhibits the proliferation, migration, and invasion of 4T1 cells, concurrently significantly suppressing the IL-6/JAK2/STAT3 signaling pathway. Furthermore, it depletes Treg cell content in 4T1 xenograft mice, thereby improving the tumor immune microenvironment and promoting the cytotoxicity of relevant tumor immune cells. These findings suggest that QUE may serve as a potential adjuvant for immune therapy in triple-negative breast cancer.

H3K27ac-induced RHOXF2 activates Wnt2/β-catenin pathway by binding to HOXC13 to aggravate the malignant progression of triple negative breast cancer

Triple negative breast cancer (TNBC) is insensitive to conventional targeted therapy and endocrine therapy, and is characterized by high invasiveness and high recurrence rate. This study aimed to explore the role and mechanism of RHOXF2 and HOXC13 on the malignant progression of TNBC. RT-qPCR and western blot were used to detect RHOXF2 and HOXC13 expression in TNBC cells. The proliferation, colony formation, invasion, migration, apoptosis and cell cycle of TNBC cells after transfection were analyzed by CCK-8 assay, colony formation assay, transwell assay, wound healing assay and flow cytometry analysis. Co-Immunoprecipitation and GST pull-down assays were used to analyze the combination between RHOXF2 and HOXC13. ChIP-PCR and luciferase reporter gene assay were used to examine the regulation of H3K27ac on RHOXF2. Besides, the expression of Ki67 and cleaved Caspase3 in tumor tissues of nude mice was determined by immunofluorescence. Results revealed that RHOXF2 and HOXC13 expression was increased in TNBC cells. RHOXF2 knockdown suppressed the proliferation, invasion and migration, as well as induced G0/G1 cell cycle arrest and apoptosis of TNBC cells. Besides, RHOXF2 could bind to HOXC13 and RHOXF2 knockdown suppressed HOXC13 expression in TNBC cells. Furthermore, HOXC13 overexpression reversed the impacts of RHOXF2 downregulation on the proliferation, invasion, migration, G0/G1 cell cycle arrest and apoptosis of TNBC cells. In addition, RHOXF2 silencing limited the tumor volume in nude mice, which was reversed by HOXC13 overexpression. Moreover, RHOXF2 knockdown interfered with Wnt2/β-catenin pathway in vitro and in vivo by binding to HOXC13. Importantly, H3K27ac acetylation could activate the expression of RHOXF2 promoter region. In conclusion, RHOXF2 activated by H3K27ac functioned as a tumor promoter in TNBC via mediating Wnt2/β-catenin pathway by binding to HOXC13, which provided promising insight into exploration on TNBC therapy.

Biotin-stapled mixed micelles of lapatinib: Unleashing apoptosis power in triple-negative breast cancer

The treatment options currently offered for triple-negative breast cancer (TNBC) encounter numerous obstacles, including disappointing overall survival rates, unavoidable side effects, and the development of drug resistance. Additionally, there is a growing need for nutrients, like vitamins (e.g., biotin), to sustain the unregulated growth of TNBC cells. Hence, targeted therapy (LPT B-MM) for enhancing the treatment of TNBC was explored which encompassed hydrophobized [using α-TOS (α-Tocopheryl succinate] Pluronic-based mixed micelles having inherent sodium-dependent multivitamin transporter (SMVT) targeting (biotin-stapled) ability. LPT B-MM had optimal size (210.72± 25.88 nm), PDI (0.272± 0.023), and enhanced drug loading capacity (∼13.31± 2.12%). Transmission electron microscopy validated the spherical shape of these micelles. In vitro release studies demonstrated drug release in a sustained manner without the risk of hemolysis. Importantly, LPT B-MM displayed heightened cellular uptake, increased cytotoxicity, a lower IC50 value, elevated reactive oxygen species, induced mitochondrial membrane depolarization, and a greater apoptosis index in TNBC cell lines compared to free LPT. This study highlights the considerable potential of LPT B-MM to induce apoptosis, showcasing its promise in enhancing payload capabilities and enabling SMVT specific targeting within the context of TNBC. LPT B-MM demonstrated the synergistic effects of LPT and α-TOS in inducing apoptosis in TNBC cells, leading to enhanced therapeutic efficacy. This novel combination therapy offers a promising strategy for improving treatment outcomes in TNBC patients and represents a significant advancement in the field of TNBC therapy.

The therapeutic potential of circular RNA in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is among the most aggressive subtypes of the disease that does not express estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Circular RNAs (circRNAs) are a type of non-coding RNA with a circular shape formed by non-standard splicing or reverse splicing. Numerous circRNAs exhibit abnormal expression in various malignancies, showing their critical role in the emergence and growth of tumors. Recent studies have shown evidence supporting the idea that certain circRNAs regulate the proliferation and metastasis of TNBC. In addition, circRNAs alter metabolism and the immune microenvironment to promote or inhibit the development of TNBC. Notably, circRNAs may affect the efficacy of clinical drug therapy, serve as therapeutic targets, and be used as molecular biomarkers in the future. Herein, we will first summarize the biogenesis and function of circRNAs. Then, we will explain current research on circRNAs related to TNBC and their potential to serve as therapeutic targets or biomarkers for future drug development, providing a new direction and idea for TNBC therapy.

Platelet Membrane Coated Cu9S8-SNAP for Targeting NIR-II Mild Photothermal Enhanced Chemodynamic/Gas Therapy of Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a highly aggressive and uncommon subtype of breast cancer with a poor prognosis. It is crucial to prioritise the creation of a nanotherapeutic method that is highly selective and actively targeting TNBC. This study explores a new nanosystem, Cu9S8-SNAP@PM (C-S@P), composed of Cu9S8-SNAP coated with a platelet membrane (PM). The purpose of this nanosystem is to cure TNBC using multimodal therapy. The utilisation of PM-coated nanoparticles (NPs) enables active targeting, leading to the efficient accumulation of C-S@P within the tumour. The Cu9S8 component within these NPs serves the potential to exert photothermal therapy (PTT) and chemodynamic therapy (CDT). Simultaneously, the S-Nitroso-N-Acetylvanicillamine (SNAP) component enables nitric oxide (NO) gas therapy (GT). Furthermore, when exposed to NIR-II laser light, Cu9S8 not only increases the temperature of the tumour area for PTT, but also boosts CDT and stimulates the release of NO through thermal reactions to improve the effectiveness of GT. Both in vitro and in vivo experimental results validate that C-S@P exhibits minimal side effects and represents a multifunctional nano-drug targeted at tumors for efficient treatment. This approach promises significant potential for TNBC therapy and broader applications in oncology.

Abstract P49: PROTAC A1874: A Potential Targeted Therapy for Breast Cancer

Abstract Background PROteolysis TArgeting Chimera (PROTAC) A1874 is a heterobifunctional structured compound consisting of a BRD4-recognizing ligand and an MDM2-recognizing ligand that functions to degrade BRD4 via the ubiquitin-proteasome system. A1874 also plays a dual role in downregulating downstream BRD4 regulator, MYC, and stabilizing p53 within nanomolar concentrations. This PROTAC thus presents itself as a potential therapy for both estrogen-receptor positive (ER+) and triple-negative breast cancer (TNBC) subtypes, which typically harbors wild-type p53 and are associated with MYC overexpression respectively. Thus, this study aims to 1) investigate the anti-oncogenic effects and mechanism of A1874 and 2) its effect in combination with existing therapies in several breast cancer (BC) cell lines. Methods A panel of BC cell lines harboring different p53 status were tested for their sensitivity to A1874. Several functional assays were conducted to determine the anti-oncogenic effects of A1874. Bliss scores were calculated using SynergyFinder to determine the interaction of drugs in combination with A1874. Results BC cell lines with p53 WT status showed significantly lower IC50 sensitivity to A1874 in the nanomolar range compared to those with p53 mutation, which exhibited sensitivity in the micromolar range regardless of subtypes. Moreover, it is effective in Tam-resistant ER+, p53 WT cells. A1874 exclusively degrades BRD4 in p53 WT cells and causes G1 arrest, inhibition of colony formation, proliferation, and migration. Knockdown of MDM2 or TP53, and lentiviral transduction of p53 mutant plasmid resulted in significant reduction in sensitivity to A1874 in p53 WT cell lines and abrogate its BRD4-degrading effect. Combination of A1874 with the mutant p53 reactivating drug, PRIMA-1, synergistically resensitize mutant p53 cells to the cytotoxic effect of A1874 across subtypes. Conclusions Our results highlight a promising potential of PROTAC A1874 as a therapeutic drug in breast cancer, specifically the ER+ subtype which typically retains its p53 WT status. Citation Format: Charlie Marvalim, Arpita Datta, Serena Bee Kee Seah, Edward Kai-Hua Chow, Soo Chin Lee. PROTAC A1874: A Potential Targeted Therapy for Breast Cancer [abstract]. In: Proceedings of Frontiers in Cancer Science; 2023 Nov 6-8; Singapore. Philadelphia (PA): AACR; Cancer Res 2024;84(8_Suppl):Abstract nr P49.

CAR-based immunotherapy for breast cancer: peculiarities, ongoing investigations, and future strategies.

Surgery, chemotherapy, and endocrine therapy have improved the overall survival and postoperative recurrence rates of Luminal A, Luminal B, and HER2-positive breast cancers but treatment modalities for triple-negative breast cancer (TNBC) with poor prognosis remain limited. The effective application of the rapidly developing chimeric antigen receptor (CAR)-T cell therapy in hematological tumors provides new ideas for the treatment of breast cancer. Choosing suitable and specific targets is crucial for applying CAR-T therapy for breast cancer treatment. In this paper, we summarize CAR-T therapy's effective targets and potential targets in different subtypes based on the existing research progress, especially for TNBC. CAR-based immunotherapy has resulted in advancements in the treatment of breast cancer. CAR-macrophages, CAR-NK cells, and CAR-mesenchymal stem cells (MSCs) may be more effective and safer for treating solid tumors, such as breast cancer. However, the tumor microenvironment (TME) of breast tumors and the side effects of CAR-T therapy pose challenges to CAR-based immunotherapy. CAR-T cells and CAR-NK cells-derived exosomes are advantageous in tumor therapy. Exosomes carrying CAR for breast cancer immunotherapy are of immense research value and may provide a treatment modality with good treatment effects. In this review, we provide an overview of the development and challenges of CAR-based immunotherapy in treating different subtypes of breast cancer and discuss the progress of CAR-expressing exosomes for breast cancer treatment. We elaborate on the development of CAR-T cells in TNBC therapy and the prospects of using CAR-macrophages, CAR-NK cells, and CAR-MSCs for treating breast cancer.

Long-term survival after neoadjuvant therapy for triple-negative breast cancer under different treatment regimens: a systematic review and network meta-analysis

BackgroundTriple-negative breast cancer (TNBC) is a life-threatening subtype of breast cancer with limited treatment options. Therefore, this network meta-analysis (NMA) aimed to evaluate and compare the effect of various neoadjuvant chemotherapy (NCT) options on the long-term survival of patients with TNBC.MethodsPubMed, Embase, Medline, Cochrane Library, Web of Science, and major international conference databases were systematically searched for randomized controlled trials (RCTs) on the efficacy of various NCT options in patients with TNBC. Searches were performed from January 2000 to June 2023. Study heterogeneity was assessed using the I2 statistic. Hazard ratios (HRs) and 95% confidence intervals (CIs) were used to evaluate disease-free survival (DFS) and overall survival (OS). Odds ratios (ORs) and 95% CIs were used to evaluate the pathologic complete response (pCR). The primary outcome was DFS.ResultsWe conducted an NMA of 21 RCTs involving 8873 patients with TNBC. Our study defined the combination of anthracyclines and taxanes as the preferred treatment option. On this basis, the addition of any of the following new drugs is considered a new treatment option: bevacizumab (B), platinum (P), poly-ADP-ribose polymerase inhibitors (PARPi), and immune checkpoint inhibitor (ICI). Based on the surface under the cumulative ranking curve (SUCRA) values, the top three SUCRA area values of DFS were taxanes, anthracycline, and cyclophosphamide (TAC; 89.23%); CT (84.53%); and B (81.06%). The top three SUCRA area values of OS were CT (83.70%), TAC (62.02%), and B-containing regimens (60.06%). The top three SUCRA area values of pCR were B + P-containing regimens (82.7%), ICI + P-containing regimens (80.2%), and ICI-containing regimens (61.8%).ConclusionsThis NMA showed that standard chemotherapy is a good choice with respect to long-term survival. Moreover, B associated with P-containing regimens is likely to be the optimal treatment option for neoadjuvant TNBC in terms of pCR.