Treatment Of Resistant Breast Cancer Research Articles

Abstract PO5-10-08: Clinical Value of Molecular Targets and Genome-Targeted Cancer Therapies Recommended by the National Comprehensive Cancer Network for Advanced Breast Cancer

Abstract Background: Genomic testing has expanded the possibilities of precision cancer medicine, particularly for advanced, treatment-resistant breast cancer cases. However, the clinical significance of most genetic alterations remains uncertain, potentially overestimating tailored therapies. The National Comprehensive Cancer Network (NCCN) guidelines are evidence-based cancer-specific recommendations used in clinical practice and that are often determinative for insurance coverage. In this study, we assessed the validity of the targets and the clinical benefit of genome-targeted cancer drugs recommended in the NCCN guidelines for metastatic breast cancer. Methods: We identified genome-targeted oncology therapies supporting advanced breast cancer recommendations in the most recent NCCN breast cancer guideline (version 4.2023). Genome-targeted drugs were defined as involving use of a genomic test in which the drug targeted a genomic alteration. We analyzed data from trials supporting advanced genome-targeted breast cancer drugs recommendations. When multiple (or overlapping) articles for the same study were identified, the most recent publication was included. We extracted key details of each trial, including trial design, blinding, phase of clinical trial and primary efficacy end points. We cross-referenced the FDA-approved indications as of 30 June 2023 with the NCCN recommendations for each drug. Strength of evidence supporting molecular targetability was evaluated using the European Society for Medical Oncology (ESMO) Scale for Clinical Actionability of molecular Targets (ESCAT). Clinical benefit for genome-targeted oncology therapies was assessed using the ESMO-Magnitude of Clinical Benefit Scale (ESMO-MCBS). We considered a substantial clinical benefit as a grade of 4 or 5. Molecular targets qualifying for ESCAT category level I-A and I-B associated with substantial clinical benefit by ESMO-MCBS were rated as high-benefit genomic-targeted breast cancer treatments. Results: We identified 47 recommendations supporting 17 genome-targeted drugs, which targeted 11 driver alterations. Out of these recommendations, 29 (62%) aligned with the FDA indications. We associated 47 trials with these recommendations, most randomized (24, 51%), phase 3 (23, 49%) and open-label (42, 89%). The most common primary endpoint (22, 47%) was overall response rate, followed by progression-free survival/time to progression (21, 45%). Twenty-four trials (51%) had a I-A ESCAT targetability, 7 (15%) had a I-B targetability, 6 (13%) had a I-C targetability score and 10 (21%) were categorized as II-B. ERBB2 amplification, germline BRCA1/2 mutations, PIK3CA mutations, and ESR1 mutation were mainly classified as tier I-A based on randomized trials demonstrating the effectiveness of approved targeted therapies in patients with these alterations. By contrast, RET fusions, NTRK fusions, high-tumor mutational burden and microsatellite instability were ranked as tier I-C and somatic BRCA mutations, germline PALB2 mutations and HER-2 mutations as II-B. Six trials (14%, 6/42) supporting drug approval demonstrated substantial ESMO-MCBS clinical benefit. Overall, 6 recommendations (14%) had high-benefit genomic-based cancer treatments. Conclusions: Fewer than one-fifth of molecular-targeted cancer therapies recommended in NCCN guidelines for metastatic breast cancer demonstrated substantial patient benefits. Value frameworks like ESCAT and ESMO-MCBS can help stakeholders identify therapies with the greatest potential. Citation Format: Ariadna Tibau, Thomas J. Hwang, Jerry Avorn, Aaron Kesselheim. Clinical Value of Molecular Targets and Genome-Targeted Cancer Therapies Recommended by the National Comprehensive Cancer Network for Advanced 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 PO5-10-08.

Oleic acid inhibits the migration and invasion of breast cancer cells with stemness characteristics through oxidative stress-mediated attenuation of the FAK/AKT/NF-κB pathway

Oleic acid, found in a variety of food sources, is beneficial to health. However, studies on its anticancer effects on cancer stem cells resistant to conventional treatments and on the mechanisms underlying such effects are scarce. Here, we evaluated the anticancer effects of oleic acid against breast cancer cells with stemness characteristics. Oleic acid inhibited the proliferation of breast cancer stem-like cells more significantly than that of their respective parental cells, and reduced the expression of stem cell markers and migration and invasion propensity. It also repressed the phosphorylation of FAK, AKT, and NF-κB, proteins involved in cell migration and invasion. Oleic acid-induced increase in reactive oxygen species levels mediated the inhibition of the FAK/AKT/NF-κB signaling axis. Our study demonstrates that oleic acid-induced oxidative stress plays an important role in inhibiting the metastatic behavior of breast cancer cells with stemness characteristics and is relevant for management of treatment-resistant breast cancer.

Centrosomes and associated proteins in pathogenesis and treatment of breast cancer.

Breast cancer is the most prevalent malignancy among women worldwide. Despite significant advances in treatment, it remains one of the leading causes of female mortality. The inability to effectively treat advanced and/or treatment-resistant breast cancer demonstrates the need to develop novel treatment strategies and targeted therapies. Centrosomes and their associated proteins have been shown to play key roles in the pathogenesis of breast cancer and thus represent promising targets for drug and biomarker development. Centrosomes are fundamental cellular structures in the mammalian cell that are responsible for error-free execution of cell division. Centrosome amplification and aberrant expression of its associated proteins such as Polo-like kinases (PLKs), Aurora kinases (AURKs) and Cyclin-dependent kinases (CDKs) have been observed in various cancers, including breast cancer. These aberrations in breast cancer are thought to cause improper chromosomal segregation during mitosis, leading to chromosomal instability and uncontrolled cell division, allowing cancer cells to acquire new genetic changes that result in evasion of cell death and the promotion of tumor formation. Various chemical compounds developed against PLKs and AURKs have shown meaningful antitumorigenic effects in breast cancer cells in vitro and in vivo. The mechanism of action of these inhibitors is likely related to exacerbation of numerical genomic instability, such as aneuploidy or polyploidy. Furthermore, growing evidence demonstrates enhanced antitumorigenic effects when inhibitors specific to centrosome-associated proteins are used in combination with either radiation or chemotherapy drugs in breast cancer. This review focuses on the current knowledge regarding the roles of centrosome and centrosome-associated proteins in breast cancer pathogenesis and their utility as novel targets for breast cancer treatment.

Research progress of exosomes in drug resistance of breast cancer.

Since breast cancer is a heterogeneous disease, there are currently a variety of treatment methods available, including chemotherapy, endocrine therapy, molecular targeted therapy, immunotherapy, radiation therapy, etc. Breast cancer recurrence and metastasis, despite many treatment modalities, constitute a considerable threat to patients' survival time and pose a clinical challenge that is difficult to tackle precisely. Exosomes have a very special and crucial role in the treatment of drug resistance in breast cancer as a carrier of intercellular communication in the tumor microenvironment. Exosomes and breast cancer treatment resistance have been linked in a growing number of clinical investigations in recent years. This paper covers the status of research on exosomes in the treatment of breast cancer drug resistance and offers theoretical guidance for investigating new strategies to treat breast cancer drug resistance.

Targeting NANOG and FAK via Cx26-derived Cell-penetrating Peptides in Triple-negative Breast Cancer.

Triple-negative breast cancer (TNBC) represents the most lethal and treatment-resistant breast cancer subtype with limited treatment options. We previously identified a protein complex unique to TNBC composed of the gap junction protein connexin 26 (Cx26), the pluripotency transcription factor NANOG, and focal adhesion kinase (FAK). We sought to determine whether a peptide mimetic of the interaction region of Cx26 attenuated tumor growth in preclinical models. We designed peptides based on Cx26 juxtamembrane domains and performed binding experiments with NANOG and FAK using surface plasmon resonance. Binding studies revealed that the Cx26 C-terminal tail and intracellular loop bound to NANOG and FAK with submicromolar-to-micromolar affinity and that a 5-amino acid sequence in the C-terminal tail of Cx26 (RYCSG) was sufficient for binding. Peptides with high affinity were engineered with a cell-penetrating antennapedia sequence and assessed in functional assays including cell proliferation, tumorsphere formation, and in vivo tumor growth, and downstream signaling changes were measured. The cell-penetrating Cx26 peptide (aCx26-pep) disrupted self-renewal while reducing nuclear FAK and NANOG and inhibiting NANOG target gene expression in TNBC cells but not luminal mammary epithelial cells. In vivo, aCx26-pep reduced tumor growth and proliferation and induced cell death. Here, we provide proof-of-concept that a Cx26 peptide-based strategy inhibits growth and alters NANOG activity specifically in TNBC, indicating the therapeutic potential of this targeting approach.

Harnessing the value of TCTP in breast cancer treatment resistance: an opportunity for personalized therapy.

Early identification of breast cancer (BC) patients at a high risk of progression may aid in therapeutic and prognostic aims. This is especially true for metastatic disease, which is responsible for most cancer-related deaths. Growing evidence indicates that the translationally controlled tumor protein (TCTP) may be a clinically relevant marker for identifying poorly differentiated aggressive BC tumors. TCTP is an intriguing protein with pleiotropic functions, which is involved in multiple signaling pathways. TCTP may also be involved in stress response, cell growth and proliferation-related processes, underlying its potential role in the initiation of metastatic growth. Thus, TCTP marks specific cancer cell sub-populations with pronounced stress adaptation, stem-like and immune-evasive properties. Therefore, we have shown that in vivo phospho-TCTP levels correlate with the response of BC cells to anti-HER2 agents. In this review, we discuss the clinical relevance of TCTP for personalized therapy, specific TCTP-targeting strategies, and currently available therapeutic agents. We propose TCTP as an actionable clinically relevant target that could potentially improve patient outcomes.

Obesity Is Associated with Immunometabolic Changes in Adipose Tissue That May Drive Treatment Resistance in Breast Cancer: Immune-Metabolic Reprogramming and Novel Therapeutic Strategies.

White adipose tissue (WAT) represents an endocrinologically and immunologically active tissue whose primary role is energy storage and homeostasis. Breast WAT is involved in the secretion of hormones and proinflammatory molecules that are associated with breast cancer development and progression. The role of adiposity and systemic inflammation in immune responses and resistance to anti-cancer treatment in breast cancer (BC) patients is still not clear. Metformin has demonstrated antitumorigenic properties both in pre-clinical and clinical studies. Nevertheless, its immunomodulating properties in BC are largely unknown. This review aims to evaluate the emerging evidence on the crosstalk between adiposity and the immune-tumour microenvironment in BC, its progression and treatment resistance, and the immunometabolic role of metformin in BC. Adiposity, and by extension subclinical inflammation, are associated with metabolic dysfunction and changes in the immune-tumour microenvironment in BC. In oestrogen receptor positive (ER+) breast tumours, it is proposed that these changes are mediated via a paracrine interaction between macrophages and preadipocytes, leading to elevated aromatase expression and secretion of pro-inflammatory cytokines and adipokines in the breast tissue in patients who are obese or overweight. In HER2+ breast tumours, WAT inflammation has been shown to be associated with resistance to trastuzumab mediated via MAPK or PI3K pathways. Furthermore, adipose tissue in patients with obesity is associated with upregulation of immune checkpoints on T-cells that is partially mediated via immunomodulatory effects of leptin and has been paradoxically associated with improved responses to immunotherapy in several cancers. Metformin may play a role in the metabolic reprogramming of tumour-infiltrating immune cells that are dysregulated by systemic inflammation. In conclusion, evidence suggests that body composition and metabolic status are associated with patient outcomes. To optimise patient stratification and personalisation of treatment, prospective studies are required to evaluate the role of body composition and metabolic parameters in metabolic immune reprogramming with and without immunotherapy in patients with BC.

Molecular mechanisms of drug resistance in breast cancer and potential strategies for overcoming resistance

Breast cancer is the most common cause of death from cancer in the world, and drug resistance is one of the most significant barriers to successful therapy for the disease. It is critical to have a solid understanding of the molecular processes driving treatment resistance in breast cancer to design targeted therapies with the potential to overcome this resistance. These complex and multifaceted mechanisms include the activation of signaling pathways that promote cell survival and proliferation, the upregulation of drug efflux pumps, the emergence of cancer stem cells, and genetic and epigenetic changes. This literature review provides an overview of these mechanisms. It discusses potential strategies for overcoming drug resistance in breast cancer, including targeted therapies that specifically target the pathways and mechanisms involved in drug resistance. The review also highlights the need for further research to identify effective strategies for overcoming drug resistance and improving treatment outcomes in breast cancer patients.

Abstract 6088: Charting new cancer dependencies with patient derived organoids

Abstract The number of patients benefiting from precision cancer medicine (PCM) is very limited. The Cancer Dependency Map Initiative aims to dramatically accelerate PCM by systematically identifying the landscape of cancer vulnerabilities across all tumors. Genome-wide knockout screens have been performed in over 1000 cancer cell lines, but these have been sourced from historically derived models, leaving many cancers underrepresented. Advances have been made in model derivation by growing cells in 3D formats, such as organoids or spheroids. These models present an opportunity to screen new cancer types, but come with challenges that require a new pipeline. Here, we present a set of screens using a genome wide CAS12 library in organoid tumor models representing novel subtypes of pancreatic, esophageal, and gastric cancer, along with treatment-resistant breast, ovarian, and prostate cancer organoids. We show that genome-wide screening of these models is feasible and can be achieved with quality comparable to 2D cell lines. Our work uncovered a set of novel dependencies associated with cell-ECM interactions that have not previously been identified in 2D models. Our methods provide a framework for screening future patient derived 3D culture models and discovering vulnerabilities in new tumor types. Citation Format: James V. Neiswender, Lisa Brenan, Tate Bertea, Jimmy Guo, Ashley Anderson, Megan Wong, Zoe Posner, Kevin Kapner, Connor Hennessey, Sarah Wie, Isabella Boyle, Barbara De Kegel, Joshua Dempster, Yuen-Yi (Moony) Tseng, David Root, Andrew Aguirre, Francisca Vazquez. Charting new cancer dependencies with patient derived organoids [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 6088.

Updated nanoscale tweezers for single-cell biopsies applied to pre-adapted dormant breast cancer cells.

The nanotweezers are a spatially controlled minimally invasive nanoscale tweezer that can extract biomolecules with single-molecule precision from individual living cells, using dielectrophoresis (DEP) to trap molecules by subjecting them to a non-uniform electric field. Our system avoids aspirating cytoplasmic fluid, allowing for the preconcentration of the analyte in real time. The aim was to create a step changing technology for the next generation of minimally invasive biopsy tools for high throughput RNA sampling and sequencing whilst keeping the cell alive. In theme with keeping the system as minimally invasive as possible, and since the electrochemical conditions could not be altered without causing unwanted electrothermal heating, the surface glass on the nanotweezers were modified to contain a poly-Thymine oligomer (Poly T). Poly T was chosen to act as a broad-spectrum tool to enhance the overall trapping capacity per biopsy. The modification was successful and significantly increased the trapping capacity per biopsy. Therefore, the updated nanotweezers were used to acquire insight into the transcriptional changes that occur in treatment resistant luminal breast cancer cells. These cells have a higher probability to survive exposure to endocrine therapies, surgical resection, and start of adjuvant treatment. Of these cells, only a handful of plastic cells survive and become enriched with the transcriptional signature of pre-adaptation previously identified in our group. These cells can then accumulate genetic changes and further transcriptional re-wiring seen in completely treatment resistant cells, eventually leading to metastasis. The updated nanotweezers were used to give a continuous transcriptional dataset for 10 of those cells over a period of 28-days observing 7 genes of interest. We propose our modified nanotweezers as a novel system extracting cytoplasmic mRNA for continuous live single-cell RNA sequencing of luminal breast cancer cells.

Enhanced Anti-cancer Potency Using a Combination of Oleanolic Acid and Maslinic Acid to Control Treatment Resistance in Breast Cancer.

The phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/ mTOR) pathway is a complex intracellular metabolic pathway that leads to cell growth and tumor proliferation and plays a key role in drug resistance in breast cancer. Therefore, the anti-cancer effects of oleanolic acid (OA), maslinic acid (MA), and their combination were investigated to improve the performance of the treatment strategy. We investigated the effect of OA and MA on cell viability using the WST-1 method. The synergistic effect of the combination was analyzed by isobologram analysis. In addition, the effects of the two compounds, individually and in combination, on apoptosis, autophagy, and the cell cycle were investigated in MCF7 cells. In addition, changes in the expression of PI3K/AKT/mTOR genes involved in apoptosis, cell cycle and metabolism were determined by quantitative RT-PCR. MA, OA, and a combination of both caused G0/G1 arrest. Apoptosis also increased in all treated groups. The autophagosomal LC3-II formation was induced 1.74-fold in the MA-treated group and 3.25-fold in the MA-OA-treated group. The combination treatment resulted in increased expression of genes such as GSK3B, PTEN, CDKN1B and FOXO3 and decreased expression of IGF1, PRKCB and AKT3 genes. The results showed that the combination of these two substances showed the highest synergistic effect at the lowest dose and using MA-OA caused cancer cells to undergo apoptosis. The use of combination drugs may reduce the resistance of cancer cells to treatment.

Association of change in health-related quality of life and treatment discontinuation in metastatic breast cancer: a post hoc, exploratory analysis of two randomized clinical trials.

PurposeIdentifying factors associated with treatment alteration (treatment discontinuation and dose reduction) may help to attain the treatment goals for metastatic breast cancer. The value of changes in the quality of life (QOL) in predicting treatment alteration remained unclear. This study aimed to examine the relationship between changes in the QOL and treatment alteration of first-line chemotherapy for metastatic breast cancer.MethodsWe merged data from two randomized clinical trials in Japan, conducted from 2006 to 2017, that included patients who were diagnosed with human epidermal growth factor receptor 2-negative and endocrine treatment-resistant breast cancer, with metastatic disease at presentation or recurrence after surgery. The European Organisation for the Research and Treatment of Cancer Quality of Life Questionnaire Core 30 was used to assess QOL. The association between change in time-dependent QOL (worsening by 10-point or not) and time to treatment alteration was assessed using the Cox regression models controlling for patient characteristics (age, liver metastasis, hormone status, and treatment regimen) and baseline QOL.ResultsWorsening physical functioning, global health status, and dyspnea were significantly associated with treatment discontinuation. Worsening role functioning, global health status, and fatigue were significantly associated with dose reduction. The threshold for defining worsening did not have a significant impact on the relationship.ConclusionChanges in QOL are associated with the probability of treatment alteration among metastatic breast cancer patients. Physical functioning, role functioning, global health status, dyspnea, and fatigue should be prioritized for symptom management in patients with metastatic breast cancer.Supplementary informationThe online version contains supplementary material available at 10.1007/s00520-022-07283-0.

Anti-cancer potential of cannabis terpenes in a Taxol-resistant model of breast cancer.

Chemotherapeutic resistance can limit breast cancer outcomes; therefore, the exploration of novel therapeutic options is warranted. Isolated compounds found in cannabis have previously been shown to exhibit anti-cancer effects, but little is known about their effects in resistant breast cancer. Our study aimed to evaluate the effects of terpenes found in cannabis in in vitro chemotherapy-resistant model of breast cancer. We aimed to identify whether five terpenes found in cannabis produced anti-cancer effects, and whether their effects were improved upon co-treatment with cannabinoids and flavonoids also found in cannabis. Nerolidol and β-caryophyllene produced the greatest cytotoxic effects, activated the apoptotic cascade, and reduced cellular invasion. Combinations with the flavonoid kaempferol potentiated the cytotoxic effects of ocimene, terpinolene, and β-myrcene. Combinations of nerolidol and Δ9-tetrahydrocannabinol or cannabidiol produced variable responses ranging from antagonism and additivity to synergy, depending on concentrations used. Our results indicate that cannabis terpenes, alone or combined with cannabinoids and flavonoids, produced anti-cancer effects in chemotherapy-resistant breast cancer cell lines. This study is a first step in the identification of compounds that could have therapeutic potential in the treatment of resistant breast cancer.

Neoadjuvant ipilimumab and nivolumab in combination with paclitaxel following anthracycline-based chemotherapy in patients with treatment resistant early-stage triple-negative breast cancer (TNBC): A single-arm phase 2 trial.

602 Background: We examined the efficacy and safety of neoadjuvant ipilimumab and nivolumab combined with paclitaxel following suboptimal response to anthracycline-based chemotherapy in patients with early-stage TNBC. Methods: This single arm multicentre phase 2 study enrolled 34 patients in 8 sites. Patients were aged ≥18 years with previously untreated stage 3 TNBC and were required to have ≥15mm of tumor remaining or 10mm of tumor with one positive lymph node after 4 cycles of anthracycline-based therapy. A suboptimal response subset at baseline was defined as < 50% reduction in tumor volume after initial anthracycline-based chemotherapy. Patients received neoadjuvant ipilimumab 1mg/kg IV 6 weekly for 2 doses and nivolumab 240mg every 2 weeks for 6 doses, with weekly paclitaxel at 80mg/m2 for 12 weeks, followed by surgery. Nivolumab (480mg 4-weekly) continued post operatively for further 9 months. Primary endpoint was pathological complete response (pCR) in breast and axilla, with secondary endpoints pCR in the suboptimal responders, pCR in PD-L1 positive patients (≥1% by SP142 assay), clinical response in the breast (ORR by RECIST), event-free (EFS) and overall survival (OS). Results: Between December 2018 and April 2020, 34 patients were enrolled, 33 were evaluable for the primary endpoint. Median age was 46.6yrs. At diagnosis, all patients were clinical stage III (AJCC v8), 16/34 (47%) were node positive, 8/31 (26%) were PD-L1 positive. At study entry (following anthracycline-based chemo), the median tumor size by ultrasound was 28mm (12-62). 16/33 (48%) were considered suboptimal responders. The pCR rate (ypT0ypN0) was 24.2% (95% CI, 11.09-42.26) in all evaluable, 37.5% [3/11] in PD-L1+ and 23% [5/22] in PD-L1- patients. In patients with suboptimal anthracycline response (< 50% tumor reduction), the pCR rate was 18.8% (95% CI, 8.52-75.51) (3/16). ORR in the breast was 57.6% (19/33) in all evaluable patients and 43.7% (8/20) in the suboptimal responders. The number of patients with residual cancer burden (RCB) class 0,1,2,3 was 8 (24%), 1 (3%), 19 (57.5%) and 5 (15%) respectively. With 14 months median follow up, 12-months EFS was estimated at 85% and OS 94%. For patients with pCR vs non-pCR, the hazard ratio (HR) for EFS was 0.62, 12 mo EFS was 100% vs 75%. In the neoadjuvant phase, 15/33 (45%) patients experienced at least one grade 3-4 adverse event. Most common immune-related event was grade 1 or 2 pneumonitis 9/33 (27%), which generally occurred with fever after the first dose of ipilimumab, and resolved. There was one case of grade 3 colitis. Conclusions: In these high risk patients, the addition of ipilimumab and nivolumab to neoadjuvant paclitaxel resulted in promising ORR and pCR rates, regardless of PD-L1 status. Rates of low grade pneumonitis were high. Follow up continues. Clinical trial information: ACTRN12617000651381.

Tackling heterogeneity in treatment-resistant breast cancer using a broad-spectrum therapeutic approach.

Tumor heterogeneity can contribute to the development of therapeutic resistance in cancer, including advanced breast cancers. The object of the Halifax project was to identify new treatments that would address mechanisms of therapeutic resistance through tumor heterogeneity by uncovering combinations of therapeutics that could target the hallmarks of cancer rather than focusing on individual gene products. A taskforce of 180 cancer researchers, used molecular profiling to highlight key targets responsible for each of the hallmarks of cancer and then find existing therapeutic agents that could be used to reach those targets with limited toxicity. In many cases, natural health products and re-purposed pharmaceuticals were identified as potential agents. Hence, by combining the molecular profiling of tumors with therapeutics that target the hallmark features of cancer, the heterogeneity of advanced-stage breast cancers can be addressed.

Dynamic Landscape of Extracellular Vesicle-Associated Proteins Is Related to Treatment Response of Patients with Metastatic Breast Cancer.

Breast cancer is the leading cause of cancer death in women. The majority of these deaths are due to disease metastasis, in which cancer cells disseminate to multiple organs and disrupt vital physiological functions. It is widely accepted that breast cancer cells secrete extracellular vesicles (EVs), which contain dynamic molecular cargo that act as versatile mediators of intercellular communication. Therefore, Evs. secreted by breast cancer cells could be involved in the development of metastatic disease and resistance to treatment. Moreover, changes in EV cargo could reflect the effects of therapy on their parent tumor cells. The aim of this feasibility study was to quantitatively profile the proteomes of Evs. isolated from blood samples taken from treatment sensitive and resistant metastatic breast cancer patients to identify proteins associated with responses. Three serial blood samples were collected from three patients with metastatic breast cancer receiving systemic therapy including a responder, a non-responder, and a mixed-responder. Evs. were isolated from plasma using size exclusion chromatography and their protein cargo was prepared for tandem mass tag (TMT)-labelling and quantitative analyses using two-dimensional high-performance liquid chromatography followed by tandem mass spectrometry. After filtering, we quantitatively identified 286 proteins with high confidence using a q value of 0.05. Of these, 149 were classified as EV associated candidate proteins and 137 as classical, high abundant plasma proteins. After comparing EV protein abundance between the responder and non-responder, we identified 35 proteins with unique de-regulated abundance patterns that was conserved at multiple time points. We propose that this proof-of-concept approach can be used to identify proteins which have potential as predictors of metastatic breast cancer response to treatment.

O76: SERUM JAM-A AS A PREDICTOR OF TREATMENT RESISTANCE IN BREAST CANCER PATIENTS

Abstract Introduction Junctional Adhesion Molecule-A (JAM-A) has important physiological functions in epithelial and endothelial barriers, but its overexpression has also been linked with tumour progression and poor prognosis in various malignancies. Since JAM-A can be enzymatically cleaved (cJAM-A) and has been detected in the bloodstream, we hypothesized that cJAM-A shed from tumours overexpressing JAM-A may represent a possible predictor of treatment resistance in breast cancer. Method An assay was optimised to detect cJAM-A in serum/plasma. Samples were obtained from HER2-positive breast cancer patients (n=20) in Beaumont Hospital. Independently, serial samples were obtained from a Canadian cohort of locally advanced breast cancer (LABC) patients (n=53). Result Serum cJAM-A levels in therapy-resistant patients was significantly higher than those in treatment-sensitive patients (p<0.05) in an Irish cohort of HER2 positive patients. In a diverse international cohort of LABC patients, the development of metastatic disease was associated with higher levels of cJAM-A (p<0.05) as well as shorter time to progression (p<0.05). Conclusion Our data suggest that cJAM-A merits further investigation as a novel biomarker enabling prospective identification of patients at greatest risk of developing therapeutic resistance. Take-home message Our data suggest that cJAM-A merits further investigation as a novel biomarker enabling prospective identification of patients at greatest risk of developing therapeutic resistance.

Potential Mechanism Underlying the Role of Mitochondria in Breast Cancer Drug Resistance and Its Related Treatment Prospects.

Breast cancer incidence and mortality rates have been consistently high among women. The use of diverse therapeutic strategies, including chemotherapy, endocrine therapy, targeted therapy, and immunotherapy, has improved breast cancer prognosis. However, drug resistance has become a tremendous obstacle in overcoming breast cancer recurrence and metastasis. It is known that mitochondria play an important role in carcinoma cell growth, invasion and apoptosis. Recent studies have explored the involvement of mitochondrial metabolism in breast cancer prognosis. Here, we will provide an overview of studies that investigated mitochondrial metabolism pathways in breast cancer treatment resistance, and discuss the application prospects of agents targeting mitochondrial pathways against drug-resistant breast cancer.

Abstract PS18-17: Mdm2 inhibition synergises with endocrine therapy or cdk4/6 inhibition for the treatment of estrogen receptor-positive breast cancer

Abstract Background: Resistance to endocrine therapy is a major clinical challenge in the management of estrogen receptor (ER)-positive breast cancer. In this setting p53 is frequently wildtype and its activity may be suppressed via upregulation of its key regulator MDM2. This underlies our rationale to evaluate MDM2 inhibition as a therapeutic strategy in treatment resistant ER-positive breast cancer. Methods: We used the MDM2 inhibitor NVP-CGM097 to treat in vitro and in vivo models alone and in combination with fulvestrant or palbociclib. We perform cell viability, cell cycle, apoptosis and senescence assays to evaluate antitumor effects in p53 wildtype and p53 mutant ER positive cell lines (MCF-7, ZR75-1, T-47D) and MCF-7 lines resistant to endocrine therapy and to CDK4/6 inhibition. We further assess the drug effects in patient-derived xenograft (PDX) models of endocrine-sensitive and -resistant ER positive breast cancer. Results: We demonstrate that MDM2 inhibition results in cell cycle arrest and increased apoptosis in p53-wildtype in vitro and in vivo breast cancer models, leading to potent anti-tumour activity. We find that endocrine therapy or CDK4/6 inhibition synergises with MDM2 inhibition but does not further enhance apoptosis. Instead, combination treatments result in profound regulation of cell cycle-related transcriptional programmes, with synergy achieved through increased antagonism of cell cycle progression. Combination therapy pushes cell lines resistant to fulvestrant or palbociclib to become senescent and significantly reduces tumour growth in a fulvestrant resistant patient derived xenograft model. Conclusions: We conclude that MDM2 inhibitors in combination with ER degraders or CDK4/6 inhibitors represent a rational strategy for treating advanced, endocrine resistant ER-positive breast cancer, operating through synergistic activation of cell cycle co-regulatory programs. Citation Format: Neil Portman, Heloisa Milioli, Sarah Alexandrou, Rhiannon Coulson, Aliza Yong, Kristine Fernandez, KeeMing Chia, Ensar Halilovic, Davendra Segara, Andrew Parker, Sue Haupt, Ygal Haupt, Wayne Tilley, Alex Swarbrick, Liz Caldon, Elgene Lim. Mdm2 inhibition synergises with endocrine therapy or cdk4/6 inhibition for the treatment of estrogen receptor-positive 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 PS18-17.

Nanostructure of Functional Larotaxel Liposomes Decorated with Guanine-Rich Quadruplex Nucleotide-Lipid Derivative for Treatment of Resistant Breast Cancer.

Breast cancer is the most common malignant disease in women all over the world and its chemotherapy outcome is restricted by multidrug resistance. Here, a nanostructure by functional larotaxel liposomes decorated with guanine-rich quadruplex nucleotide-lipid derivative for treatment of resistant breast cancer is developed. The studies are performed on the resistant breast cancer cells and the cancer-bearing mice. The nucleotide-lipid derivative (DSPE-PEG2000 -C6 -GT28nt) is synthesized by introducing a hydrophobic hexyl linkage between GT-28nt(containing 17 guanines and 11 thymidines) and DSPE-PEG2000 -NHS, and is incorporated on the functional larotaxel liposomes for specific binding with nucleolin receptor on the resistant cancer cells. The studies demonstrate that the liposomes had long circulatory effect, targeted capability, and significant anticancer efficacy in resistant cancer-bearing mice. The studies further reveal their action mechanism, consisting of blocking depolymerization of microtubules, arresting cell cycle, blocking JAK-STAT signaling pathway, and inhibiting activity of antiapoptotic proteins. In conclusion, the functional larotaxel liposomes can be used for effective treatment of drug-resistant breast cancer, and this study also offers a novel targeted nanomedicine based on nucleotide-lipid derivative.