Breast Cancer Cell Xenografts Research Articles

Abstract PS15-02: A Phase Ⅰb Study of D-0502 as Monotherapy for Advanced or Metastatic ER-Positive and HER2-Negative Breast Cancer: Results from the Dose-Expansion Stage

Abstract Background: Endocrine therapy is the mainstay treatment for estrogen receptor (ER)-positive advanced breast cancer (BC). D-0502, an orally bioavailable selective estrogen receptor degrader (SERD), has previously demonstrated antitumor activity in various ER-positive (ER+) and human epidermal growth factor receptor 2 negative (HER2-) breast cancer cell lines and xenograft models. The phase Ⅰ open-label study (NCT03471663) evaluated the safety, tolerability, pharmacokinetics (PK) and efficacy of D-0502 as monotherapy and in combination with palbociclib in female patients with ER+ and HER2- breast cancer. The dose escalation part of D-0502 monotherapy (phase Ⅰa) has been presented before (SABCS 2021, PS11-26 Abstract #1348). Here, we present the results of D-0502 monotherapy from the dose-expansion stage in phase Ⅰb study. Methods: In the single-agent dose-expansion stage of phase Ⅰb study, patients (n=60) received D-0502 (400 mg QD) in 28-day cycles. Eligible patients included females with confirmed ER+, HER2- locally advanced, or metastatic BC; ECOG 0-1; measurable disease (RECIST v1.1); premenopausal or postmenopausal status; adequate hematologic, hepatic and renal functions. The primary objectives are to characterize the safety of D-0502. The secondary objectives are to evaluate the preliminary anti-tumor activity and the PK characteristic. Results: As of April 07, 2023, 60 female patients were enrolled and treated with 400mg single-agent D-0502. Median age was 57 (range: 32-82) years, 55.0% had an ECOG PS of 1. Disease progression resulting in treatment discontinuation occurred in 66.7% (40/60) of patients, and 6.7% (4/60) of patients discontinued treatment because of AEs. Treatment-related adverse events (TRAEs) were reported in 57 pts (95.0%), most of which were grade 1-2. No grade 4/5 TRAE has been reported. The incidence of serious adverse events was 6.7% (4/60). The most common (≥ 15%) TRAEs included vomiting, dizziness, nausea, increased aspartate aminotransferase and alanine aminotransferase, anaemia, decreased appetite, diarrhoea, and malaise. In the 51 efficacy evaluable patients, 8 patients had partial response (PR) and 27 had stable disease (SD); objective response rate (ORR) and disease control rate (DCR) were 15.7% (8/51) and 68.6% (35/51), respectively. The clinical benefit rate (CBR: CR + PR + SD ≥24 weeks) was 47.1% (24/51). The median PFS was 5.6 months (95% Cl: 2.0, 10.0). Conclusion: D-0502 monotherapy showed promising antitumor activity and tolerable toxicity in female patients with ER+ and HER2- locally advanced or metastatic BC. Currently this treatment is being evaluated in a phase Ⅲ study for patients with ER+ and HER2- locally advanced or metastatic BC in China. Citation Format: Jiayu Wang, Tao Sun, Qingyuan Zhang, Yanxia Shi, Xu Wang, Yiding Chen, Quchang Ouyang, Kunyan Li, Manojkumar Bupathi, w. Jeffery Edenfield, Andrea L.M. Silber, Hong Zong, Erika Hamilton, Dejan Juric, Kate Lathrop, Yihong Zhang, Kathryn Stazzone, Zhe Shi, Yaolin Wang, Ling Zhang, Binghe Xu. A Phase Ⅰb Study of D-0502 as Monotherapy for Advanced or Metastatic ER-Positive and HER2-Negative Breast Cancer: Results from the Dose-Expansion Stage [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 PS15-02.

Impact of NDUFAF6 on breast cancer prognosis: linking mitochondrial regulation to immune response and PD-L1 expression

BackgroundBreast cancer is a major global health concern, and there is a continuous search for novel biomarkers to predict its prognosis. The mitochondrial protein NDUFAF6, previously studied in liver cancer, is now being investigated for its role in breast cancer. This study aims to explore the expression and functional significance of NDUFAF6 in breast cancer using various databases and experimental models.MethodsWe analyzed breast cancer samples from The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and Human Protein Atlas (HPA) databases, supplemented with immunohistochemistry (IHC) staining to assess NDUFAF6 expression. A breast cancer cell xenograft mouse model was used to evaluate tumor growth, apoptosis, and NDUFAF6 expression. Survival probabilities were estimated through Kaplan–Meier plots and Cox regression analysis. A Protein–Protein Interaction (PPI) network was constructed, and differentially expressed genes related to NDUFAF6 were analyzed using GO, KEGG, and GSEA. The relationship between NDUFAF6 expression, immune checkpoints, and immune infiltration was also evaluated.ResultsNDUFAF6 was found to be overexpressed in breast cancer patients and in the xenograft mouse model. Its expression correlated with worse clinical features and prognosis. NDUFAF6 expression was an independent predictor of breast cancer outcomes in both univariate and multivariate analyses. Functionally, NDUFAF6 is implicated in several immune-related pathways. Crucially, NDUFAF6 expression correlated with various immune infiltrating cells and checkpoints, particularly promoting PD-L1 expression by inhibiting the NRF2 signaling pathway.ConclusionThe study establishes NDUFAF6 as a potential prognostic biomarker in breast cancer. Its mechanism of action, involving the inhibition of NRF2 to upregulate PD-L1, highlights its significance in the disease's progression and potential as a target for immunotherapy.

Hsa-miR-148a-3p promotes malignant behavior of breast cancer cells by downregulating DUSP1

To investigate the role of Hsa-miR-148a-3p in regulating biological behaviors of breast cancer cells and explore the mechanism. TCGA database was used to identify the differential miRNAs and mRNAs in breast cancer, and the protein-protein interaction (PPI) network was constructed using String and Cytoscape to screen the top 10 hub genes and construct the miRNA-TOP10hub network. RT-qPCR was used to detect the expressions of Hsa-miR-148a-3p and DUSP1 in breast cancer tissues and cell lines. The effects of Hsa-miR-148a-3p mimic and inhibitor on proliferation, migration, invasion and apoptosis of MCF-7 cells were analyzed, and luciferase reporter gene experiment was performed to verify the binding of Hsa-miR-148a-3p to DUSP1. The effect of Hsa-miR-148a-3p overexpression on breast cancer cell xenograft growth was evaluated in nude mice. Kaplan-Meier survival curve analysis was used to analyze the survival of the tumor-bearing mice, and the expression level of DUSP1 in the xenografts was detected using immunohistochemistry. A total of 54 differential miRNAs and 799 differential mRNAs were identified in breast cancer; 3716 target genes were intersected with the differential mRNA, resulting in 150 intersected genes. The top 10 hub genes were downregulated in breast cancer tissues in the PPI network. Double luciferase reporter gene experiment confirmed that Hsa-miR-148a-3p was capable of binding to DUSP1. Hsa-miR-148a-3p was up-regulated and DUSP1 was down-regulated significantly in breast cancer tissues and cells (P<0.01). In breast cancer cells, Hsa-miR-148a-3p mimic strongly promoted cell proliferation, migration and invasion and inhibited cell apoptosis (P<0.01). Hsa-miR-148a-3p overexpression obviously promoted xenograft growth in nude mice (P<0.01), shortened survival time of the mice (P<0.01), and reduced the expression of DUSP1 in the xenografts (P<0.01). Hsa-miR-148a-3p promotes malignant behavior of breast cancer cells by inhibiting the expression of DUSP1.

Non-POU Domain-Containing Octomer-Binding (NONO) protein expression and stability promotes the tumorigenicity and activation of Akt/MAPK/β-catenin pathways in human breast cancer cells

Breast cancer is one of the most common cancers with a high mortality rate, underscoring the need to identify new therapeutic targets. Here we report that non-POU domain-containing octamer-binding (NONO) protein is overexpressed in breast cancer and validated the interaction of the WW domain of PIN1 with c-terminal threonine-proline (thr-pro) motifs of NONO. The interaction of NONO with PIN1 increases the stability of NONO by inhibiting its proteasomal degradation, and this identifies PIN1 as a positive regulator of NONO in promoting breast tumor development. Functionally, silencing of NONO inhibits the growth, survival, migration, invasion, epithelial to mesenchymal transition (EMT), and stemness of breast cancer cells in vitro. A human metastatic breast cancer cell xenograft was established in transparent zebrafish (Danio rerio) embryos to study the metastatic inability of NONO-silenced breast cancer cells in vivo. Mechanistically, NONO depletion promotes the expression of the PDL1 cell-surface protein in breast cancer cells. The identification of novel interactions of NONO with c-Jun and β-catenin proteins and activation of the Akt/MAPK/β-catenin signaling suggests that NONO is a novel regulator of Akt/MAPK/β-catenin signaling pathways. Taken together, our results indicated an essential role of NONO in the tumorigenicity of breast cancer and could be a potential target for anti-cancerous drugs.C-mep14XPctyTeLC54ZqwrVideo

CYD0281, a Bcl-2 BH4 domain antagonist, inhibits tumor angiogenesis and breast cancer tumor growth

BackgroundB-cell lymphoma 2 (Bcl-2) family proteins are key regulators of apoptosis, which possess four conserved Bcl-2 homologies (BH) domains. Among the BH domains, the BH3 domain is considered as a potent ‘death domain’ while the BH4 domain is required for anti-apoptotic activity. Bcl-2 can be converted to a pro-apoptotic molecule through the removal or mutation of the BH4 domain. Bcl-2 is considered as an inducer of angiogenesis, which can promote tumor vascular network formation and further afford nutrients and oxygen to promote tumor progression. However, whether disrupting the function of the BH4 domain to convert Bcl-2 into a pro-apoptotic molecule could make Bcl-2 possess the potential for anti-angiogenic therapy remains to be defined.MethodsCYD0281 was designed and synthesized according to the lead structure of BDA-366, and its function on inducing a conformational change of Bcl-2 was further evaluated via immunoprecipitation (IP) and immunofluorescence (IF) assays. Moreover, the function of CYD0281 on apoptosis of endothelial cells was analyzed via cell viability, flow cytometry, and western blotting assays. Additionally, the role of CYD0281 on angiogenesis in vitro was determined via endothelial cell migration and tube formation assays and rat aortic ring assay. Chick embryo chorioallantoic membrane (CAM) and yolk sac membrane (YSM) models, breast cancer cell xenograft tumor on CAM and in mouse models as well as the Matrigel plug angiogenesis assay were used to explore the effects of CYD0281 on angiogenesis in vivo.ResultsWe identified a novel potent small-molecule Bcl-2-BH4 domain antagonist, CYD0281, which exhibited significant anti-angiogenic effects both in vitro and in vivo, and further inhibited breast cancer tumor growth. CYD0281 was found to induce conformational changes in Bcl-2 through the exposure of the BH3 domain and convert Bcl-2 from an anti-apoptotic molecule into a cell death inducer, thereby resulting in the apoptosis of vascular endothelial cells.ConclusionsThis study has revealed CYD0281 as a novel Bcl-2-BH4 antagonist that induces conformational changes of Bcl-2 to convert to a pro-apoptotic molecule. Our findings indicate that CYD0281 plays a crucial role in anti-angiogenesis and may be further developed as a potential anti-tumor drug candidate for breast cancer. This work also provides a potential anti-angiogenic strategy for breast cancer treatment.

Abstract 2785: Carbidopa/α-methyltryptophan as an ideal combination therapy for breast cancer

Abstract Background/Hypothesis: The amino acid transporter SLC6A14 is upregulated in estrogen receptor (ER)-positive breast cancer, a subtype that represents 75-80% of all breast cancers. Obesity/overweight increases the risk of breast cancer due to estrogen generated from fat cells that fuel the growth of the ER-positive breast cancer. Previous studies from our lab have demonstrated that blockade of the amino acid transporter SLC6A14 by the small molecule α-methyltryptophan reduces the growth of ER-positive breast cancer in mouse xenografts of human breast cancer cells and in a spontaneous mouse model of ER-positive breast cancer. We have also discovered that α-methyltryptophan functions as a potent weight-loss agent. We believe that this compound would be effective for the treatment of ER-positive breast cancer, especially in obese/overweight women. α-methyltryptophan is metabolized by aromatic amino acid decarboxylase. Therefore, combination of this compound with carbidopa, a well-known inhibitor of this enzyme, might potentiate the anticancer efficacy of α-methyltryptophan. We tested this idea in the present study using a syngeneic mouse model of ER-positive breast cancer using the mouse breast cancer cell line AT3. Results: A syngeneic tumor-cell transplant mouse model was used for ER-positive breast cancer. AT3 cells were injected into the mammary fat pad of C57BL/6 mice. This allows to monitor the growth of AT3 tumor growth in an immunologically competent mammary tissue environment. Drug treatment in drinking water was started after tumor growth was noticeable (100 mm3). There were four groups: (i) control; (ii) α-methyltryptophan at 0.5 mg/ml; (iii) carbidopa at 0.25 mg/ml; (iv) α-methyltryptophan at 0.5 mg/ml + carbidopa at 0.25 mg/ml. Tumor growth was monitored every three days. The mice were killed after 4 weeks of treatment. Tumors were excised and weighed. These studies showed that α-methyltryptophan and carbidopa were independently effective in reducing the tumor (48% reduction, p&amp;lt;0.05 for α-methyltryptophan; 50% reduction, p&amp;lt;0.05 for carbidopa), but the combination was the most effective (92% reduction, p&amp;lt;0.01). These effects were evident irrespective of whether the monitored parameter was tumor weight or tumor volume. Conclusion: The combination treatment significantly decreased the tumor size and volume compared to carbidopa and α-methyltryptophan alone. We do not know yet if the improved efficacy of the combination of the two drugs is due to a simple additive effect or due to a synergistic effect. Studies have shown that carbidopa promotes degradation of ER, indicating that carbidopa has its own independent anticancer effect that is relevant to ER-positive breast cancer. Further studies are needed to differentiate between the effect of carbidopa as an independent anticancer agent and its ability to potentiate the anticancer efficacy of α-methyltryptophan by preventing its metabolic degradation. Citation Format: Sirin Falconi, Sabarish Ramachandran, Vadivel Ganapathy. Carbidopa/α-methyltryptophan as an ideal combination therapy for breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2785.

RETRACTED ARTICLE: LncRNA BCAR4 promotes migration, invasion, and chemo-resistance by inhibiting miR-644a in breast cancer

BackgroundMetastasis and drug resistance of breast cancer have become a barrier to treating patients successfully. Long noncoding RNAs (lncRNAs) are known as vital players in cancer development and progression. MethodsThe RT-qPCR were used to detect the gene expression. Colony formation assay, would healing assay, and transwell assay were performed to investigate oncogenic functions of cells. CCK8 assay was used to detect the cell viability. Western blot was applied to detect the protein level. Dual-luciferase reporter assay was used to determine the relationship between molecules. Mouse orthotopic xenograft tumor models were established to evaluate the effects of BCAR4 on tumor growth and metastasis in vivo. ResultsLncRNA BCAR4 was significantly increased in breast cancer patients’ tissues and plasma and upregulated in breast cancer cell lines. BCAR4 upregulation was correlated with the TNM stages and decreased after surgical removal of breast tumors. Silencing of BCAR4 suppressed breast cancer cell colony formation, migration, invasion, and xenograft tumor growth and promoted chemo-sensitivity. Mechanistically, BCAR4 facilitates breast cancer migration and invasion via the miR-644a-CCR7 axis of the MAPK pathway. BCAR4 promotes ABCB1 expression indirectly by binding to and down-regulating miR-644a to induce chemo-resistance in breast cancer.ConclusionsOur findings provide insights into the oncogenic role of BCAR4 and implicate BCAR4 as a potential diagnostic biomarker and a promising therapeutic agent to suppress metastasis and inhibit chemo-resistance of breast cancer.

Abstract 6228: APR-246, which restores p53 function, is highly active against alternative lengthening of telomere (ALT) cell lines and PDXs

Abstract Introduction: Most cancers proliferate by activating telomerase (TA+) while 10% of cancers utilize alternate lengthening of telomeres (ALT). ALT has been associated with resistance to DNA damaging agents, p53 loss-of-function (p53LOF), ATRX mutations, and very poor survival. ATM kinase, which activates functional p53, is constitutively activated in ALT cancers (Science Translational Medicine 18:eabd5750, 2021). We hypothesized that the constitutive activation of ATM kinase in ALT cancers would confer high sensitivity to pharmacological reactivation of p53 function. Methods: We used patient-derived ALT (telomeric DNA C-circle positive) and TA+ neuroblastoma, sarcoma, colorectal, and breast cancer cell lines and xenografts treated with the clinical-stage p53 reactivator eprenetapopt (APR-246) and irinotecan. In vitro cytotoxicity was assayed by DIMSCAN digital imaging microscopy, ATM activation by immunofluorescence microscopy, and protein expression by western blotting. Results: ALT p53LOF cell lines were significantly (p&amp;lt;0.05) less sensitive to DNA-damaging agents relative to TA+ p53LOF comparators. Constitutive phosphorylation (activation) of ATM kinase and the DNA damage marker 53BP1 were observed at telomeres in ALT but not TA+ cell lines. APR-246 induced p53 targets p21 and NOXA and was significantly more cytotoxic (p&amp;lt;0.001) for ALT relative to TA+ cell lines, regardless of TP53 status. Overexpression of p53 in a TP53-null ALT cell line increased sensitivity (p&amp;lt;0.0001) to APR-246. Knockdown of p53 or ATM kinase in ALT TP53 mutated and wild-type cell lines antagonized (p&amp;lt;0.0001) APR-246 activity. Induction of telomere dysfunction in a TA+ p53LOF neuroblastoma cell line using dominant-negative TRF2 (a shelterin protein that blocks ATM activation at telomeres) activated ATM and sensitized cells to APR-246 (p&amp;lt;0.01). APR-246 enhanced the cytotoxicity of irinotecan (as SN38) in ALT cell lines in vitro to a higher degree than in TA+ p53LOF cell lines (p&amp;lt;0.05). Single-agent APR-246 significantly (p&amp;lt;0.0001) increased event-free survival (EFS) of mice with ALT xenografts relative to controls. APR-246 enhanced (p&amp;lt;0.0001) the activity of irinotecan in 3 neuroblastoma, 2 rhabdomyosarcoma, 1 colorectal, and 1 triple-negative breast ALT xenograft models with most mice (47/56) achieving complete responses and an EFS of &amp;gt;100 days (45/56) compared to no complete responses (median EFS ~ 34 days) in mice treated with only irinotecan (p&amp;lt;0.0001). APR-246 + irinotecan had no significant effect relative to irinotecan alone (p=0.08) on EFS of mice with TA+ p53LOF xenografts (median EFS ~ 40 days). Conclusion: ALT cancers of a variety of histologies are highly resistant to DNA damaging agents, have p53LOF, and constitutive activation of ATM kinase, which confers high sensitivity to p53 reactivation by APR-246. APR-246 warrants clinical testing in patients with ALT cancers. Citation Format: Shawn J. Macha, Balakrishna Koneru, Trevor Burrow, Charles Zhu, Dzmitry Savitski, Jonas Nance, Kristyn McCoy, Cody Eslinger, C Patrick Reynolds. APR-246, which restores p53 function, is highly active against alternative lengthening of telomere (ALT) cell lines and PDXs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6228.

Oncohistone Mutations Occur at Functional Sites of Regulatory ADP-Ribosylation.

This study identifies cancer-driving mutations in histones as sites of PARP1-mediated ADP-ribosylation in breast and ovarian cancers, providing a molecular pathway by which cancers may subvert the growth-regulating effects of PARP1.

Accumulation of amyloid beta (Aβ) and amyloid precursor protein (APP) in tumors formed by a mouse xenograft model of inflammatory breast cancer.

Accumulation of amyloid in breast cancer is a well‐known phenomenon, but only immunoglobulin light‐chain amyloidosis (AL) or transthyretin (TTR) amyloid had been detected in human breast tumor samples previously. We recently reported that another amyloidogenic peptide, amyloid beta (Aβ), is present in an aggregated form in animal and human high‐grade gliomas and suggested that it originates systemically from the blood, possibly generated by platelets. To study whether breast cancers are also associated with these Aβ peptides and in what form, we used a nude mouse model inoculated with triple‐negative inflammatory breast cancer cell (SUM‐149) xenografts, which develop noticeable tumors. Immunostaining with two types of specific antibodies for Aβ identified the clear presence of Aβ peptides associated with (a) carcinoma cells and (b) extracellular aggregated amyloid (also revealed by Congo red and thioflavin S staining). Aβ peptides, in both cells and in aggregated amyloid, were distributed in clear gradients, with maximum levels near blood vessels. We detected significant presence of amyloid precursor protein (APP) in the walls of blood vessels of tumor samples, as well as in carcinoma cells. Finally, we used ELISA to confirm the presence of elevated levels of mouse‐generated Aβ40 in tumors. We conclude that Aβ in inflammatory breast cancer tumors, at least in a mouse model, is always present and is concentrated near blood vessels. We also discuss here the possible pathways of Aβ accumulation in tumors and whether this phenomenon could represent the specific signature of high‐grade cancers.

Blocking Estrogen Synthesis Leads to Different Hormonal Responses in Canine and Human Triple Negative Inflammatory Breast Cancer.

Simple SummaryEstrogen is responsible for tumor progression, and blocking its synthesis is effective in certain breast cancers. Therefore, the aim of this study is to determine the effect of letrozole (anti-aromatase) and STX-64 (anti-sulfatase) in canine and human inflammatory breast cancer cell lines and xenografts. The results reveal that letrozole blocks estrogen synthesis, reducing tumor progression. However, STX-64 increases estradiol synthesis, increasing tumor progression. In summary, letrozole may be an effective treatment for canine and human inflammatory breast cancer.Blocking estrogen synthesis by inhibitors of estrogen synthesis is a widely used therapy against estrogen receptor-positive tumors. However, these therapies are less effective in negative expression tumors. Therefore, this study determined the effectiveness of anti-aromatase and anti-sulfatase therapies in canine and human inflammatory breast cancer. Cell cultures and xenografts from IPC-366 and SUM149 were treated with different doses of letrozole (anti-aromatase) and STX-64 (anti-sulfatase), in order to observe their effectiveness in terms of cell proliferation, tumor progression, and the appearance of metastases and hormonal profiles. The results revealed that both treatments are effective in vitro since they reduce cell proliferation and decrease the secreted estrogen levels. In xenograft mice, while treatment with letrozole reduces tumor progression by 30–40%, STX-64 increases tumor progression by 20%. The hormonal results obtained determined that STX-64 produced an increase in circulating and intratumoral levels of estradiol, which led to an increase in tumor progression. However, letrozole was able to block estrogen synthesis by decreasing the levels of circulating and intratumoral estrogen and thus slowing down tumor progression. In conclusion, letrozole can be an effective treatment for canine and human inflammatory breast cancer. The knowledge of the hormonal profile of breast tumors reflects useful information on the effectiveness of different endocrine treatments.

Cellular dormancy in minimal residual disease following targeted therapy

BackgroundBreast cancer mortality is principally due to tumor recurrence, which can occur following extended periods of clinical remission that may last decades. While clinical latency has been postulated to reflect the ability of residual tumor cells to persist in a dormant state, this hypothesis remains unproven since little is known about the biology of these cells. Consequently, defining the properties of residual tumor cells is an essential goal with important clinical implications for preventing recurrence and improving cancer outcomes.MethodsTo identify conserved features of residual tumor cells, we modeled minimal residual disease using inducible transgenic mouse models for HER2/neu and Wnt1-driven tumorigenesis that recapitulate cardinal features of human breast cancer progression, as well as human breast cancer cell xenografts subjected to targeted therapy. Fluorescence-activated cell sorting was used to isolate tumor cells from primary tumors, residual lesions following oncogene blockade, and recurrent tumors to analyze gene expression signatures and evaluate tumor-initiating cell properties.ResultsWe demonstrate that residual tumor cells surviving oncogenic pathway inhibition at both local and distant sites exist in a state of cellular dormancy, despite adequate vascularization and the absence of adaptive immunity, and retain the ability to re-enter the cell cycle and give rise to recurrent tumors after extended latency periods. Compared to primary or recurrent tumor cells, dormant residual tumor cells possess unique features that are conserved across mouse models for human breast cancer driven by different oncogenes, and express a gene signature that is strongly associated with recurrence-free survival in breast cancer patients and similar to that of tumor cells in which dormancy is induced by the microenvironment. Although residual tumor cells in both the HER2/neu and Wnt1 models are enriched for phenotypic features associated with tumor-initiating cells, limiting dilution experiments revealed that residual tumor cells are not enriched for cells capable of giving rise to primary tumors, but are enriched for cells capable of giving rise to recurrent tumors, suggesting that tumor-initiating populations underlying primary tumorigenesis may be distinct from those that give rise to recurrence following therapy.ConclusionsResidual cancer cells surviving targeted therapy reside in a well-vascularized, desmoplastic microenvironment at both local and distant sites. These cells exist in a state of cellular dormancy that bears little resemblance to primary or recurrent tumor cells, but shares similarities with cells in which dormancy is induced by microenvironmental cues. Our observations suggest that dormancy may be a conserved response to targeted therapy independent of the oncogenic pathway inhibited or properties of the primary tumor, that the mechanisms underlying dormancy at local and distant sites may be related, and that the dormant state represents a potential therapeutic target for preventing cancer recurrence.

Abstract PS11-26: A phase 1 study of D-0502, an orally bioavailable SERD, for advanced or metastatic HR-positive and HER2-negative breast cancer

Abstract Background: Targeting the estrogen receptor (ER) has proven to be one of the most successful strategies in treating HR+ (ER+ and PR+) and HER2- breast cancer. Selective estrogen receptor degraders (SERD) can be used as single agents or in combination with CDK4/6 inhibitors such as palbociclib. Fulvestrant is currently the only approved agent in its class and is limited by poor oral bioavailability necessitating monthly intramuscular injections. D-0502 is an orally bioavailable SERD with potent activity in various HR+ and HER2- breast cancer cell lines and xenograft models. Its combination with palbociclib in both MCF-7 xenograft models and ESR-1 mutated (Y537S) patient derived breast cancer xenograft models resulted in further tumor growth inhibition or regression. Drug metabolism and pharmacokinetic studies both in vitro and in vivo demonstrated that D-0502 exhibits favorable PK profiles suitable for clinical development. Methods: A first-in-human phase 1 study was conducted to evaluate D-0502 in women with advanced or metastatic HR+, HER2- breast cancer (MBC) (NCT03471663). The primary objective is to characterize the safety and tolerability of D-0502 and D-0502 in combination with palbociclib, to identify an MTD and/or RP2D. The secondary objectives are to evaluate the PK properties and the preliminary anti-tumor activities. Patients received D-0502 orally once daily in 28-day cycles. The study has completed dose escalation (phase 1a), and dose expansion and combination studies (phase 1b) are ongoing. In phase Ia, patients were enrolled and evaluated using conventional 3+3 dose-escalation to identify the MTD of D-0502 as a single agent. The phase 1b was divided into 2 stages. In Stage 1, D-0502 was evaluated with palbociclib at a dose below the MTD first before escalating to the MTD. Stage 1 also included patients in China treated at a dose below and at the MTD as single agent as well as in combination with palbociclib. Stage 2 will further evaluate the MTD for both single agent and combination of D-0502 with palbociclib. Results: At the time of this abstract submission, phase 1a dose escalation is completed, R2PD has been identified, and no DLTs were observed. PK analysis of D-0502 indicates a dose proportional increase in exposure as the dose increases, and the exposure has exceeded the potential therapeutic exposure level based on preclinical studies. The Phase Ib Stage 1 portion has also completed enrollment and the study is currently enrolling patients into phase Ib Stage 2. D-0502 as a single agent or in combination has been well tolerated with radiological tumor response and clinical benefit response (CBR) observed. Safety, PK and preliminary efficacy data will be reported at the meeting presentation. Conclusion: A first-in-human phase 1 study of D-0502 has been initiated in women with advanced or metastatic HR-positive and HER2-negative breast cancer. D-0502 has been well tolerated and achieved significant exposure and preliminary clinical activity in patients. Further results will be presented at the meeting. Citation Format: Cynthia Osborne, Donald A Richards, Sharon T Wilks, Sami Diab, Dejan Juric, Kate Lathrop, Andrea Silber, William Edenfield, Amardeep Aulakh, Ben Cho, Binghe Xu, Tao Sun, Quchang Ouyang, Yanxia Shi, Kathryn Stazzone, Zhe Shi, Ling Zhang, Yaolin Wang, Erika P Hamilton. A phase 1 study of D-0502, an orally bioavailable SERD, for advanced or metastatic HR-positive and HER2-negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS11-26.

SIRT6 enhances oxidative phosphorylation in breast cancer and promotes mammary tumorigenesis in mice

BackgroundSirtuin 6 (SIRT6) is a NAD+-dependent deacetylase with key roles in cell metabolism. High SIRT6 expression is associated with adverse prognosis in breast cancer (BC) patients. However, the mechanisms through which SIRT6 exerts its pro-oncogenic effects in BC remain unclear. Here, we sought to define the role of SIRT6 in BC cell metabolism and in mouse polyoma middle T antigen (PyMT)-driven mammary tumors.MethodsWe evaluated the effect of a heterozygous deletion of Sirt6 on tumor latency and survival of mouse mammary tumor virus (MMTV)-PyMT mice. The effect of SIRT6 silencing on human BC cell growth was assessed in MDA-MB-231 xenografts. We also analyzed the effect of Sirt6 heterozygous deletion, of SIRT6 silencing, and of the overexpression of either wild-type (WT) or catalytically inactive (H133Y) SIRT6 on BC cell pyruvate dehydrogenase (PDH) expression and activity and oxidative phosphorylation (OXPHOS), including respiratory complex activity, ATP/AMP ratio, AMPK activation, and intracellular calcium concentration.ResultsThe heterozygous Sirt6 deletion extended tumor latency and mouse survival in the MMTV-PyMT mouse BC model, while SIRT6 silencing slowed the growth of MDA-MB-231 BC cell xenografts. WT, but not catalytically inactive, SIRT6 enhanced PDH expression and activity, OXPHOS, and ATP/AMP ratio in MDA-MB-231 and MCF7 BC cells. Opposite effects were obtained by SIRT6 silencing, which also blunted the expression of genes encoding for respiratory chain proteins, such as UQCRFS1, COX5B, NDUFB8, and UQCRC2, and increased AMPK activation in BC cells. In addition, SIRT6 overexpression increased, while SIRT6 silencing reduced, intracellular calcium concentration in MDA-MB-231 cells. Consistent with these findings, the heterozygous Sirt6 deletion reduced the expression of OXPHOS-related genes, the activity of respiratory complexes, and the ATP/AMP ratio in tumors isolated from MMTV-PyMT mice.ConclusionsVia its enzymatic activity, SIRT6 enhances PDH expression and activity, OXPHOS, ATP/AMP ratio, and intracellular calcium concentration, while reducing AMPK activation, in BC cells. Thus, overall, SIRT6 inhibition appears as a viable strategy for preventing or treating BC.

Sodium propionate exerts anticancer effect in mice bearing breast cancer cell xenograft by regulating JAK2/STAT3/ROS/p38 MAPK signaling.

Propionate is a short-chain fatty acid (SCFA) mainly produced from carbohydrates by gut microbiota. Sodium propionate (SP) has shown to suppress the invasion in G protein-coupled receptor 41 (GPR41) and GPR43-overexpressing breast cancer cells. In this study we investigated the effects of SP on the proliferation, apoptosis, autophagy, and antioxidant production of breast cancer cells. We showed that SP (5-20 mM) dose-dependently inhibited proliferation and induced apoptosis in breast cancer cell lines JIMT-1 (ER-negative and HER2-expressing) and MCF7 (ER-positive type), and this effect was not affected by PTX, thus not mediated by the GPR41 or GPR43 SCFA receptors. Meanwhile, we demonstrated that SP treatment increased autophagic and antioxidant activity in JIMT-1 and MCF7 breast cancer cells, which might be a compensatory mechanism to overcome SP-induced apoptosis, but were not sufficient to overcome SP-mediated suppression of proliferation and induction of apoptosis. We revealed that the anticancer effect of SP was mediated by inhibiting JAK2/STAT3 signaling which led to cell-cycle arrest at G0/G1 phase, and increasing levels of ROS and phosphorylation of p38 MAPK which induced apoptosis. In nude mice bearing JIMT-1 and MCF7 cells xenograft, administration of SP (20 mg/mL in drinking water) significantly suppressed tumor growth by regulating STAT3 and p38 in tumor tissues. These results suggest that SP suppresses proliferation and induces apoptosis in breast cancer cells by inhibiting STAT3, increasing the ROS level and activating p38. Therefore, SP is a candidate therapeutic agent for breast cancer.

GDC-0941 and CXCL8 (3-72) K11R/G31P combination therapy confers enhanced efficacy against breast cancer.

Aim: Herein is presented the combined effect of PI3K inhibitor (GDC-0941) and CXCR1/2 analogue (G31P) in breast cancer. Materials & methods: Breast cancer cell lines and xenograft model were employed to test the efficacy of the combination therapy. Results: GDC-0941+G31P treatment substantially inhibited multiplication of all the breast cancer cell lines used in this study (BT474, HCC1954 and 4T1). Even though single therapies caused a meaningful S-phase cell cycle arrest, the inhibition effect was more potent with the combined treatment. Similarly, enhanced apoptosis accompanied GDC-0941+G31P treatment. Furthermore, the migration ability of the breast cancer cell lines were significantly curtailed by the combination therapy compared with the single treatments. Conclusion: The findings suggest that combination treatment involving PI3K inhibitor and CXCR1/2 analogue (G31P) could be a potent therapeutic option for breast cancer treatment.

A Graphene‐Based Flexible Device as a Specific Far‐Infrared Emitter for Noninvasive Tumor Therapy

AbstractNoninvasive treatments are emerging as a promising strategy not only due to their non‐invasive nature, but also due to their additive effects to traditional radiotherapy and chemotherapy. Herein, specific far‐infrared rays generated from single‐layer, graphene‐based devices are applied to tumors as a novel noninvasive therapeutic strategy. In MDA‐MB‐231 breast cancer cell xenograft and metastasis models, irradiation generated from this flexible device reduces the rate of tumor growth and the number of metastatic nodules per lung by 42% and 55%, respectively. This result might be induced by the similarity between the emission spectra of the device and the absorption spectra of the living tissue. With its high energy conversion and safety, the graphene‐based device can serve as an adjuvant therapeutic instrument for combined tumor treatment.

Dietary Antioxidant Trans-Cinnamaldehyde Reduced Visfatin-Induced Breast Cancer Progression: In Vivo and In Vitro Study.

Excessive growth of cancer cells is the main cause of cancer mortality. Therefore, discovering how to inhibit cancer growth is an important research topic. Recently, the newly discovered adipokine, known as nicotinamide phosphoribosyl transferase (NAMPT, visfatin), which has been associated with metabolic syndrome and obesity, has also been found to be a major cause of cancer proliferation. Therefore, inhibition of NAMPT and reduction of Nicotinamide adenine dinucleotide (NAD) synthesis is one strategy for cancer therapy. Cinnamaldehyde (CA), as an antioxidant and anticancer natural compound, may have the ability to inhibit visfatin. The breast cancer cell line and xenograft animal models were treated under different dosages of visfatin combined with CA and FK866 (a visfatin inhibitor) to test for cell toxicity, as well as inhibition of tumor-related proliferation of protein expression. In the breast cancer cell and the xenograft animal model, visfatin significantly increased proliferation-related protein expression, but combination with CA or FK866 significantly reduced visfatin-induced carcinogenic effects. For the first time, a natural compound inhibiting extracellular and intracellular NAMPT has been demonstrated. We hope that, in the future, this can be used as a potential anticancer compound and provide further directions for research.

Effect of Bifidobacterium-induced changes in tumor tissue acoustic properties on efficacy of high-intensity focused ultrasound ablation

To investigate the effects of Bifidobacterium on the acoustic characteristics of tumor tissue and how such acoustic changes affect the efficacy of high-intensity focused ultrasound (HIFU) ablation in nude mice. Forty mice bearing human breast cancer cell (MDA-MB-231) xenograft were randomized into experimental group (n=20) and control group (n=20) for intravenous injection of Bifidobacterium suspension (200 μL, 4 × 108 cfu/mL) and PBS (200 μL) for 3 consecutive days, respectively. Before and at 3 and 7 days after the first injection, shear wave elastography was used to evaluate the hardness of the tumor tissue. On day 7 after the first injection, 10 mice from each group were sacrificed and the sound velocity and sound attenuation of the tumor tissues were measured. The changes in the collagen fibers in the tumors were evaluated using Masson staining, and neovascularization in the tumor was assessed with immunohistochemistry for platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31). The remaining 10 tumor-bearing mice in each group were subjected to HIFU ablation, and the ablation efficiency was evaluated by assessing the changes in irradiation gray values, coagulative necrosis volume, energy efficiency factor (EEF) and irradiation area and by pathological examination with HE staining. In the experimental group, the collagen fibers in the tumor tissues were strong and densely aligned, and the tumors contained fewer new blood vessels showing strip-or spot-like morphologies. In the control group, the collagen fibers in the tumors were thin and loosely arranged, and the tumors showed abundant elongated or round new blood vessels. Bifidobacterium colonized in the tumor 7 days after the injection, and the tumor hardness was significantly greater in the experimental group than in the control group (P=0.01); the acoustic velocity (P=0.001) and the acoustic attenuation (P=0.000) of the tumor tissues were also greater in the experimental group. HIFU irradiation resulted in significantly greater changes in the gray scale of tumor (P=0.0006) and larger coagulative necrosis volume (P=0.0045) in the experimental group than in the control group, and the EEF was significantly smaller in the experimental group (P=0.0134). Bifidobacterium can cause changes in collagen fiber content, acoustic velocity and attenuation in the tumor tissue and reduce the EEF of HIFU irradiation, thereby improving the efficacy of HIFU irradiation.

Abstract 3871: A novel TACC3 inhibitor as an anti-cancer agent in breast cancer

Abstract Transforming Acidic Coiled-Coil Containing Protein 3 (TACC3) is a microtubule-associated protein that is localized on mitotic spindles and ensures proper chromosomal segregation and microtubule stability. TACC3 is frequently amplified or mutated, and was demonstrated to be a prognostic factor in a broad spectrum of cancers which makes it a highly attractive therapeutic target. TACC3 knockdown was demonstrated to cause mitotic spindle defects and prevent proper mitotic progression causing apoptotic cell death. Inhibition of TACC3 with the currently available small molecule inhibitors, KHS101 and SPL-B, has been shown to reduce the growth of glioblastoma xenografts, and suppress tumor growth in ovarian cancer xenografts, respectively. However, none of these TACC3 inhibitors is being tested in clinics potentially due to low systemic stability or high IC50 (inhibitory concentration 50) values. Here, by combining rational drug design and screening approaches, we aimed to identify a novel and more potent TACC3 inhibitor that is effective in in vitro and in vivo systems and that can be used as a mitotic blocker in breast cancer (BC). A library of test compounds was generated by replacing certain functional groups of already available TACC3 inhibitors with their isosteric equivalents to improve potency and drug-like properties. Then, the generated compounds were tested in vitro in terms of growth inhibition in a panel of breast cancer cell lines of different breast cancer subtypes. The compounds were also compared based on their effect on the cellular processes that TACC3 is involved in, and were further compared with genomic TACC3 inhibition by siRNAs. Finally, the most promising agent was tested in vivo in terms of its anti-tumorigenic effects. BO-264 was identified as the most potent TACC3 inhibitor that effectively kills breast cancer cells of different subtypes when administered at nanomolar dose. Moreover, it demonstrated superior inhibitory effects on mitotic progression, DNA repair, and cellular viability as compared to currently available inhibitors. Oral administration of BO-264 suppressed tumor growth in breast cancer xenografts at a dose that caused no apparent toxicity. Specificity of BO-264 to TACC3 protein was tested by kinome profiling and further validated by state-of-art binding assays. Currently, we are testing the pharmacokinetics and pharmacodynamics properties and organ toxicity of our inhibitor and performing the detailed molecular characterization of BO-264-mediated anti-tumor effects. Overall, our preclinical findings suggest that our novel compound (BO-264) is potentially a specific TACC3 inhibitor, causing growth inhibition in breast cancer cell lines and xenograft models by inducing mitotic arrest, DNA damage and apoptosis. Considering the critical importance of TACC3 as a cancer biomarker and driver of disease progression, BO-264 has great potential to be used as a novel therapeutic strategy in BC. Citation Format: Ozge Akbulut, Deniz Lengerli, Ozge Saatci, Elif Duman, Urartu Seker, Burcu Caliskan, Erden Banoglu, Ozgur Sahin. A novel TACC3 inhibitor as an anti-cancer agent in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3871.