HER2 Breast Research Articles

Gasdermin B over-expression modulates HER2-targeted therapy resistance by inducing protective autophagy through Rab7 activation.

BackgroundGasdermin B (GSDMB) over-expression promotes poor prognosis and aggressive behavior in HER2 breast cancer by increasing resistance to therapy. Decoding the molecular mechanism of GSDMB-mediated drug resistance is crucial to identify novel effective targeted treatments for HER2/GSDMB aggressive tumors.MethodsDifferent in vitro approaches (immunoblot, qRT-PCR, flow cytometry, proteomic analysis, immunoprecipitation, and confocal/electron microscopy) were performed in HER2 breast and gastroesophageal carcinoma cell models. Results were then validated using in vivo preclinical animal models and analyzing human breast and gastric cancer samples.ResultsGSDMB up-regulation renders HER2 cancer cells more resistant to anti-HER2 agents by promoting protective autophagy. Accordingly, the combination of lapatinib with the autophagy inhibitor chloroquine increases the therapeutic response of GSDMB-positive cancers in vitro and in zebrafish and mice tumor xenograft in vivo models. Mechanistically, GSDMB N-terminal domain interacts with the key components of the autophagy machinery LC3B and Rab7, facilitating the Rab7 activation during pro-survival autophagy in response to anti-HER2 therapies. Finally, we validated these results in clinical samples where GSDMB/Rab7/LC3B co-expression associates significantly with relapse in HER2 breast and gastric cancers.ConclusionOur findings uncover for the first time a functional link between GSDMB over-expression and protective autophagy in response to HER2-targeted therapies. GSDMB behaves like an autophagy adaptor and plays a pivotal role in modulating autophagosome maturation through Rab7 activation. Finally, our results provide a new and accessible therapeutic approach for HER2/GSDMB + cancers with adverse clinical outcome.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13046-022-02497-w.

Targeting HER2-positive metastatic breast cancer with ARX788, a novel anti-HER2 antibody-drug conjugate in patients whose disease is resistant or refractory to T-DM1, and/or T-DXd, and/or tucatinib-containing regimens.

TPS1112 Background: The overexpression and/or amplification of human epidermal growth factor receptor 2 (HER2) occurs in approximately 20% of breast cancers (BC) and is a major driver of tumor development and progression. This HER2 subtype confers aggressive tumor behavior and the HER2 receptor remains a valuable target for antibodies, bi-specifics, and antibody drug conjugates (ADC). With advances in targeted therapy, patients with HER2-positive breast cancer (HER2+ BC) may experience an improved prognosis, including survival. Novel HER2-targeted therapies are being investigated to overcome drug resistance and to help mitigate adverse events (e.g., cardiotoxicity). ARX788 is a next-generation ADC using a technology platform whereby a HER2 specific monoclonal antibody is conjugated with Amberstatin269 (AS269), a potent cytotoxic tubulin inhibitor. Site-specificity, high homogeneity, and stable covalent conjugation of ARX788 leads to its slow release and prolonged peak of serum pAF-AS269, which may contribute to the lower systemic toxicity and increased targeted delivery of payload to tumor cells at a lower effective dose compared to other HER2 ADCs. Clinical activity has been seen in Phase I HER2 breast and pan-tumor studies. Methods: Trial Design: ACE-Breast-03 (NCT04829604) is a global, phase 2 study designed to assess anticancer activity and safety of ARX788 in patients with metastatic HER2 positive breast cancer. Patients whose disease is resistant or refractory to T-DM1, and/or T-DXd, and/or tucatinib-containing regimens are eligible. Patients must have adequate organ function. Any brain metastases must be radiographically stable without steroid dependence. Efficacy will be assessed using Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 by imaging every 6 weeks on study. Endpoints include objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), best overall response (BOR), duration of response (DOR), and time to response (TTR). The safety and tolerability profile will be evaluated. Blood samples will be collected at specified time points to determine serum concentrations of ARX788, total antibody, and metabolite pAF-AS269. Potential predictive and/or prognostic biomarkers at baseline and on-treatment will be analyzed for exploratory purposes. Descriptive statistics will be used to evaluate anticancer activity, safety, and tolerability. The study is currently recruiting patients. Please contact breast03trialinquiry@ambrx.com for additional information. Clinical trial information: NCT04829604.

Abstract P2-12-06: Pathological response-guided postoperative treatment strategy for positive HR/negative HER2 and positive lymphnodes breast cancer patients with non-responsive pathological results to neoadjuvant chemotherapy

Abstract Objective: No consensus up to date suggesting whether patients with positive HR/negative HER-2 and positive lymph nodes breast cancer should receive additional adjuvant chemotherapy following a poor response to neoadjuvant chemotherapy to acquire a better DDFS. The main aim of this trial is to compare the 5-year DDFS between additional adjuvant chemotherapy plus endocrine therapy group and endocrine alone group following 4 cycles neoadjuvant chemotherapy. Method: A multicenter, open-label, randomized, controlled, phase 3 trial was conducted. All patients enrolled in the study were HR+ HER2- LN+ breast cancer patients completing four cycles neoadjuvant chemotherapy, with a non-responsive pathological result to neoadjuvant chemotherapy. The non-responsive criterion was defined as Miller and Payne staging grade1 to grade 3, or any grade of Miller and Payne staging but residual positive lymph nodes were found in surgical specimen. All enrolled patients were randomly assigned to receive four cycles non-cross resistant regimen plus endocrine therapy, or endocrine therapy alone. The primary endpoint was DDFS, and the secondary endpoint was iDFS and OS. Result: From October 2010 to September 2018, a total of 391 patients were enrolled for eligibility. The final ITT analysis compromised 379 patients (187 in adjuvant chemotherapy plus endocrine therapy group, and 192 in endocrine therapy alone group). After a median follow-up of 72.4 months, the 5-year distant disease free survival estimate was 92% (95% CI 88-96) in the adjuvant chemotherapy group and 90% (86-94) in the endocrine therapy alone group (HR 0.79, 95% CI 0.45-1.37) (P=0.401). In the prespecified CEF subgroup, the 5-year DDFS was 94% (95% CI 90-98) in adjuvant chemotherapy group, and 91% (95% CI 87-94) in endocrine group (HR 0.68, 95% CI 0.36-1.30) (P=0.249). In the exploratory analysis, we found a better 5-year DDFS trend in adjuvant chemotherapy group in ypN+ patients in CEF subgroup (P=0.196). Conclusion: A better 5-year DDFS trend in additional adjuvant chemotherapy plus endocrine therapy can be found for patients with positive HR/negative HER-2 and positive lymph nodes following a poor response to neoadjuvant chemotherapy. Citation Format: Yang Yang, Xue Chen, Zhaoqing Fan, Yingjian He, Yuntao Xie, Jinfeng Li, Tianfeng Wang, Tao Ouyang. Pathological response-guided postoperative treatment strategy for positive HR/negative HER2 and positive lymphnodes breast cancer patients with non-responsive pathological results to neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-12-06.

Abstract P5-08-09: Characterization of the Rac/Cdc42 inhibitor MBQ-168 as an anti-cancer compound

Abstract Metastasis continues to be the primary cause of cancer-related death in women with breast cancer, needing targeted therapies to inhibit this process. Therefore, we developed inhibitors targeting the homologous Rho GTPases Rac1 and Cdc42, which direct the actin cytoskeletal changes required for cell migration/invasion; and thus, metastasis. We characterized the potent inhibitor, MBQ-167 that blocks both Rac1 and Cdc42 at IC50s 103 nM and 78 nM, respectively, in human HER2 (+) and triple-negative breast cancer (TNBC) cells. Consequently, MBQ-167 inhibits tumor growth and metastasis by ~90% in pre-clinical mouse models of breast cancer (Humphries-Bickley, et al., 2017). To improve the activity and solubility of MBQ-167, we synthesized a panel of derivatives, maintaining the 9-ethyl-3-(1H-1,2,3-triazol-1-yl)-9H-carbazole as the core for each derivative. Of the derivatives tested, MBQ-168 demonstrated improved solubility and comparable efficacy. Similar to MBQ-167, MBQ-168 induced actin cytoskeletal disintegration, cell rounding, and detachment to ultimately undergo anoikis. In 120hrs, MBQ-168 significantly inhibited the viability of MDA-MB-231 at a GI50 of 228nM and HER2+ MDA-MB-435 cells with a GI50 of 137 nM, without affecting the viability of Human Mammary Epithelial Cells (HMEC). In apoptosis assays, MBQ-168 treatment, at 500nM for 48 hrs, demonstrated a similar response to MBQ-167 by >4-fold increase in Caspase 3/7 activity in HER2 (+), and MDA-MB-231 and MDA-MB-468 TNBC cells. In wound healing assays, MBQ-168 also responded similar to MBQ-167 by a ~80% inhibition of breast cancer cell migration at 250nM and 500nM for 24hrs. Moreover, as quantified from Rac1.GTP pulldown assays, following 250nM treatment for 24hrs, MBQ-168 inhibited Rac1 activation in the attached cell population by ~70%, and in the detached cell population by ~100%, demonstrating a potent inhibition of Rac1 activation. In a preliminary study for relative efficacy in mice, MBQ-168 significantly reduced HER2+ MDA-MB-435 mammary tumor growth (~90%) at 5mg/kg BW via IP administration. In conclusion, MBQ-168 is an effective Rac inhibitor that reduces breast cancer cell viability, induces apoptosis, and inhibits breast cancer cell migration, actin cytoskeletal extensions, and Rac1 activation to result in a drastic reduction in mammary tumor growth in mice. We predict that the increased solubility of MBQ-168 will make it more bioavailable than MBQ-167. Thus, we have demonstrated that small structural modifications of MBQ-167 can affect the cytotoxic activity of carbazole derivatives with potential as anti-cancer drugs, and as tools to block Rac/Cdc42 activities in biological systems. Citation Format: Julia Medina, Tatiana Matos, Luis Velazquez, Michael Rivera, Ailed Cruz-Collazo, Eliud Hernandez, Cornelis Vlaar, Suranganie Dharmawardhane. Characterization of the Rac/Cdc42 inhibitor MBQ-168 as an anti-cancer compound [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-08-09.

Abstract P2-08-22: Correlation of ER (ESR1), PR (PGR), and HER2 (ERBB2) at protein and mRNA levels in operable breast cancer

Abstract Background:. We aimed to analyze the concordance between ER (ESR1), PR (PGR), and HER2 (ERBB2) levels and breast cancer subtyping results obtained by using the immunohistochemistry (IHC) and reverse transcriptase-polymerase chain reaction (RT-PCR) methods and to assess recurrence-free survival (RFS) between subtypes as determined by the two methods. Patients and Methods:. We included a total of 441 operable breast cancer patients, consisting of the training (n = 116), testing (n = 56) and validation (n = 269) cohorts in this study. Protein levels of estrogen receptor (ER) and progesterone receptor (PR) were obtained by using the IHC and that of human epidermal growth factor receptor 2 (HER2) by the IHC/FISH methods. Expression (mRNA) levels of the corresponding genes, ESR1, PGR, and ERBB2, respectively, were determined by the RT-PCR method. We then compared the status of ER (ESR1), PR (PGR), and HER2 (ERBB2) in the training, testing and validation cohorts. We categorized all validation cases into luminal (ER/PR-positive and HER2-negative), HER2 (HER2-positive regardless of ER/PR status), and triple negative (TN: ER-, PR-, and HER2-negative) subtypes accordingly. The concordance of the two methods and RFS estimated by the Kaplan-Meier methods of the three different subtypes were revealed to evaluate the clinical performance. Results:. The concordance rates between the two methods in the validation cohort were 95.1% (Kappa = 0.74) for ER (ESR1), 91.1% (Kappa = 0.67) for PR (PGR), and 93.6% (Kappa = 0.59) for HER2 (ERBB2). Kappa statistic was 0.66 for the resulting luminal, HER2 and TN subtypes. The 5-year RFS was 83.3% for luminal vs. 73.9% for HER2 vs. 48.4% for TN subtypes as determined by the IHC (p = 0.019), and 84.3% vs. 66.3% vs. 54.4% by the RT-PCR method (p = 0.016). Conclusions:. Whereas discordance existed for some cases between the IHC and RT-PCR methods for determination of the ER (ESR1), PR (PGR), and HER2 (ERBB2) status and the resulting subtypes; both the methods showed values in RFS prognosis of the population studied. It is arguable that supplementing the conventional IHC with the molecular method for subtyping of breast cancer may have beneficial clinical implications. Citation Format: Lei Lei, Xiaojia Wang, Skye Hung-Chun Cheng. Correlation of ER (ESR1), PR (PGR), and HER2 (ERBB2) at protein and mRNA levels in operable breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-08-22.

Correlation of ER, PR, and HER2 at the protein and mRNA levels in Asian patients with operable breast cancer.

Breast cancer is the most common cancer and the leading cause of cancer-related deaths in women. The estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) are the important biomarkers in the prognosis of breast cancer, and their expression is used to categorize breast cancer into subtypes. We aimed to analyze the concordance among ER, PR, and HER2 expression levels and breast cancer subtyping results obtained by immunohistochemistry (IHC, for protein) and reverse transcriptase-polymerase chain reaction (RT-PCR, for mRNA) and to assess the recurrence-free survival (RFS) of the different subtypes as determined by the two methods. We compared biomarker expression by IHC and RT-PCR in 397 operable breast cancer patients and categorized all patients into luminal, HER2, and triple-negative (TN) subtypes. The concordance of biomarker expression between the two methods was 81.6% (κ = 0.4075) for ER, 87.2% (κ = 0.5647) for PR, and 79.1% (κ = 0.2767) for HER2. The κ-statistic was 0.3624 for the resulting luminal, HER2, and TN subtypes. The probability of 5-year RFS was 0.78 for the luminal subtype versus 0.77 for HER2 and 0.51 for TN, when determined by IHC (P=0.007); and 0.80, 0.71, and 0.61, respectively, when determined by the RT-PCR method (P=0.008). Based on the current evidence, subtyping by RT-PCR performs similar to conventional IHC with regard to the 5-year prognosis. The PCR method may thus provide a complementary means of subtyping when IHC results are ambiguous.

Targeting prooxidant MnSOD effect inhibits triple-negative breast cancer (TNBC) progression and M2 macrophage functions under the oncogenic stress

Triple-negative breast cancer (TNBC) has been shown with high mitochondrial oxidative phosphorylation and production of reactive oxygen species (ROS). MnSOD (SOD2) is a mitochondrial antioxidant defense that has been implicated in inhibition of human malignancies. However, the impact of MnSOD on immunosuppressive macrophage functions and TNBC aggressiveness has never been explored. We found here that SOD2high is primarily observed in the aggressive subtypes of HER2(+) breast cancers and TNBCs patients. Further analyses demonstrated that the oncoprotein multiple copies in T-cell malignancy-1 (MCT-1 or MCTS1) induces mitochondrial superoxide dismutase (MnSOD) in TNBC cells by stabilizing the transcription factor Nrf2. SOD2high/MCTS1high expression correlates with a poor prognosis in breast cancer patients. MnSOD in TNBC cells functions as a prooxidant peroxidase that increases mitochondrial ROS (mROS) and adaptation to oxidative stress under the oncogenic effect. Interleukin-6 (IL-6) in the MCT-1 pathway elevates Nrf2/MnSOD and mROS levels. Knockdown of MnSOD inhibits TNBC cell invasion, breast cancer stem cells (BCSCs), mROS, and IL-6 excretion promoted by MCT-1. TNBC cells deficient in MnSOD prevent the polarization and chemotaxis of M2 macrophages but improve the ability of M1 macrophages to engulf cancer cells. Quenching mROS with MitoQ, a mitochondria-targeted non-metal-based antioxidant MnSOD mimics, effectively suppresses BCSCs and M2 macrophage invasion exacerbated by MnSOD and MCT-1. Consistently, silencing MnSOD impedes TNBC progression and intratumoral M2 macrophage infiltration. We revealed a novel stratagem for TNBC management involving targeting the MCT-1 oncogene-induced mitochondrial prooxidant MnSOD pathway, which prevents the development of an immunosuppressive tumor microenvironment.

Relationship between tumor size and metastatic site in patients with stage IV breast cancer: A large SEER-based study.

e13065 Background: To analyze the correlation between tumor size and metastatic site in first-diagnosed stage IV breast cancer patients. Methods: Stage IV breast cancer patients diagnosed from 2010 to 2015 were screened by the Surveillance, Epidemiology, and End Results (SEER) database. The characteristics of clinical variables were represented by a frequency table, and the Chi-square test was used for comparison. At the same time, the Chi-square test was used to analyze the relationship between tumor size and organ metastasis. Correlation between tumor size and the prognosis of patients was contributed by KM curve and Log-rank test. Results: Regardless of tumor size, the proportion of bone metastasis was higher and brain metastasis was lower in breast cancer patients. There were significant differences in the site of metastases based on different subtype. Luminal A and Luminal B breast cancer had the highest proportion of bone metastases; brain metastasis accounted for the highest proportion in triple-negative breast cancer (TNBC); while the incidence of liver metastasis was the highest in Her-2(+) breast cancer. At the same time, the results indicated that Luminal A breast cancer with a tumor size > 5 cm was more likely to develop multi-site metastasis and lung metastasis, while Luminal B breast cancer with a tumor size ≤ 5 cm was more likely to develop liver metastasis. The results also revealed that TNBC patients with a tumor size of 0 - 2cm were more likely to develop bone metastasis than those with a tumor size > 5 cm, and the incidence of lung metastasis in triple-negative patients showed an increasing trend with the increase of tumor size. Conclusions: Based on subtype, we found that there was a significant difference between tumor size and metastatic site in patients with stage IV breast cancer, and the difference was statistically significant. This study provided evidence-based basis for decision-making of stage IV breast cancer treatment.

BCL-2 (-938C>A), BAX (-248G>A), and HER2 Ile655Val Polymorphisms and Breast Cancer Risk in Indian Population.

Breast cancer is the most common carcinoma in women worldwide. The present case-control study was aimed to examine the association of BCL-2 (-938C> A), BAX (-248G > A), and HER2 (I655V i.e. A > G) polymorphisms with breast cancer risk in Indian population. This study enrolled 117 breast cancer cases and 104 controls. BCL-2 (-938C > A), BAX (-248G > A), and HER2 Ile655Val polymorphisms were screened by PCR-RFLP method. There was no significance difference in the allelic and genotype frequency of the BCL-2 (-938C > A) and BAX (-248G > A) polymorphisms between cases and controls. In relation to HER2 Ile655Val polymorphism, the statistical analysis of observed genotypic frequencies showed significant association (p-0.0059). Compared to Ile/Ile (A/A) genotype, frequency of Ile/Val (A/G) genotype was significantly higher among cases than in control group and observed to increase the breast cancer risk (OR, 2.43; 95%CI, 1.32–4.46; p-0.004). The frequency of Val (G) allele was significantly higher in cases as compared to controls (6.83% vs 2.88%, resp.). Compared to Ile (A) allele, significant increase in the risk of breast cancer was observed with Val (G) allele (OR, 2.21; 95% CI, 1.35–3.63; p-0.0016). We observed significant association between HER2 Ile655Val polymorphism and breast cancer risk under the dominant (OR = 2.52; 95% CI: 1.41–4.51; p-0.001) and codominant (OR, 2.24; 95% CI: 1.23–4.09; p-0.008) model. In our study, BCL-2 (-938C > A) and BAX (-248G > A) polymorphism were not found to be associated with breast cancer risk. This present study for the first time shows significant association of HER2 Ile655Val polymorphism with risk of breast cancer in Indian population. Therefore, we suggest that each population need to evaluate its own genetic profile for breast cancer risk that may be helpful for better understanding the racial and geographic differences reported for breast cancer incidence and mortality.

Abstract 720: Analysis of circulating tumor DNA after neoadjuvant therapy to predict disease relapse in patients with stage II-III breast cancer

Abstract The therapeutic efficacy of neoadjuvant chemotherapy for patients with breast cancer is usually assessed by the reduction of tumor size and lymph nodes. The pathologic complete response (pCR) is considered as a marker related to good prognosis. However, patients who can achieve pCR is a minor population, and pCR may be not a robust marker predicting prognosis in patients with ER-positive breast cancer. Additional markers allowing the assessment of prognosis is needed. Circulating tumor DNA (ctDNA) has been proved as a marker to detect disease progression in metastatic breast cancer and predict relapse in patients after resection of breast cancer. Therefore, we would like to assess the value of ctDNA in breast cancer patients receiving neoadjuvant therapy. The ctDNA was collected before and after completion of the neoadjuvant chemotherapy (Tend). The presence of ctDNA was detected by ultra-deep targeted next-generation sequencing. We enrolled 82 patients and 62 patients were found to have ctDNA as the biomarkers. The presence of ctDNA included nonsynonymous variants and copy number variations in TP53, PIK3CA, HER2, CDH1, PTEN, S100A, CCND1 and c-MYC. Among the 62 patients, there were 24 patients with hormone receptor (+)/Her2(-), 20 with Her2(+) and 18 with triple-negative breast cancer (TNBC). Pathologic complete response (pCR) occurred in 9 patients, partial response in 32 patients and stable/progression in 21 patients, according to the RECIST 1.1 criteria. Univariate analysis showed tumor reduction>50% (p=0.032), number of metastatic lymph node (p=0.039), and status of ctDNA at Tend (p<0.001) were significantly associated with disease-free survival (DFS). The 5-year DFS of patients with undetectable ctDNA at Tend (74.0%, 95% confidence interval (CI) range 98%-50%) was significantly superior to those with detected ctDNA (16.8%, 95% CI range 36.1%-0%). Multivariate analysis revealed that status of ctDNA at Tend was the only one independent factor predicting relapse (hazard ratio 7.74, 95% CI 2.81-21.35). Two patients had pCR and were found to have alterations of ctDNA at Tend; one with TNBC had distant metastases at 6 months after mastectomy and the other with Her2 (+) breast cancer had brain metastasis at the end of adjuvant trastuzumab treatment. Therefore, we concluded that the presence of ctDNA at the end of the neoadjuvant chemotherapy was a poor prognostic factor predicting relapse in patients with stage II-III breast cancer. Citation Format: Po-Han Lin, Sung-Sheng Kuo, Chiun-Sheng Huang. Analysis of circulating tumor DNA after neoadjuvant therapy to predict disease relapse in patients with stage II-III breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 720.

E2F cell cycle pathway score as a predictive biomarker of ER+/HER2- breast cancer response to neoadjuvant chemotherapy.

e12593 Background: Although the survival rate of patients diagnosed with breast cancer has greatly improved over the last decades, the metastatic stage of the disease remains incurable. Estrogen receptor positive (ER+)/human receptor 2 negative (HER2-) breast cancers accounts for approximately 70% of metastatic breast cancers and, it is responsible for most of the deaths from the disease. Another issue of ER+/HER2- breast cancer is its poor response to neoadjuvant chemotherapy (NAC). Recently, several clinical trials have shown that endocrine therapy plus FDA-approved cyclin-dependent kinases (CDK) 4/6 inhibitors have improved the treatment response to patients with advanced ER+/HER2 breast. The CDK 4/6 is an important E2F-related factor. Therefore, we hypothesized that E2F pathway is predictive biomarker for treatment response of ER+/HER2- breast cancer. Methods: METABRIC dataset was used for training cohort. And TCGA breast cancer as well as four neoadjuvant therapeutic cohorts were used as validation cohort. The E2F pathway score was calculated by Gene Set Variant Analysis (GSVA). Results: Tumors with high E2F pathway score enriched cell proliferation and cell cycle pathway related gene sets (G2M, MYC v1, and v2, MITOTIC, MTORC1, PI3K AKT MTOR, and DNA repair; FDR < 0.001). The high E2F pathway score was significantly associated with TNBC and HER2+ (p < 0.001), which are known to be clinically aggressive, and advanced stage (p < 0.001) and high grade (p < 0.001). The score also correlated with copy mutation (r = 0.605, p < 0.01). The patients, who had early recurrence before 5 years, had significantly high score rather than non-recurrence patients (p < 0.001). Moreover, these results were validated in TCGA cohort. The high E2F pathway score group had a higher pCR rate than the low score group with ER+/HER2- breast cancer (p < 0.001). Interestingly, the tumors in high score group expressed higher CDK pathway related molecules compared to low score group. Conclusions: The E2F pathway score was found to be a predictive biomarker for neoadjuvant chemotherapy in ER+/HER2- breast cancer patients.

THE IMPACT OF CARDIOTOXICITY AND TRASTUZUMAB INTERRUPTION ON BREAST CANCER OUTCOMES

Trastuzumab (T) improves outcomes in patients (pts) with HER2 (+) breast cancer (BCA) but is associated with risk of cardiotoxicity (CTOX). CTOX is the most common reason for early T interruption, but the impact of this practice on BCA outcomes is unknown. All pts with stage I-III HER2 (+) BCA

Abstract P3-08-68: Application of 21-gene recurrence score in patients with T1-2, N0-1 ER-positive/HER2 negative breast cancer: Survival analysis in relation to clinical risk score

Abstract Background: Incorporating 21-gene recurrence score (RS) into daily practice have saved chemotherapy in about more than two-third of ER(+)/HER2(-) patients. In those with node-positive disease, 21-gene RS showed a clinically meaningful benefit in terms of reducing chemotherapy. We investigated the rate of chemotherapy and a short-term clinical outcome in patients with T1-2, N0-1 ER(+)/HER2(-) breast cancer after we actively applied 21-gene RS in our daily practice. Method: We identified T1-2, N0-1, ER(+)/HER2(-) breast cancer patients who underwent breast surgery followed by adjuvant treatment from January 2014 to December 2018. The clinical risk score (CRS) was defined as low and high based on histologic grade, tumor size, and nodal status as used in MINDACT trial. The rate of chemotherapy and survival outcomes were analyzed according to CRS and whether 21-gene RS was performed or not. Also, the patients were classified into 3 groups: Group A, endocrine alone without 21-gene RS; Group B, endocrine or chemo-endocrine guided by 21-gene RS; Group C, chemo-endo without 21-gene RS. In the patients between 2014 and 2016, we investigated the recurrence-free survival (RFS). Results: In a total of 1,008 patients, there were 446 (44.2%) for group A, 352 (34.9%) for group B, and 210 (20.8%) for group C, showing that 21-gene RS was done in about one-third of all. The rate of high CRS was 18.2% (81 of 446) in the group A, 42.3% (149 of 352) in the group B, and 71.0% (149 of 210) in the group C (P<0.001). In the low-CRS group, 36 (17.7%) of 203 patients with 21-gene RS received chemotherapy and 61 (14.3%) of 365 patients without 21-gene RS received chemotherapy (P=0.268). However, in the high-CRS group, 46 (30.9%) of 149 patients with 21-gene RS received chemotherapy although 149 (64.8%) of 230 patients without 21-gene RS received chemotherapy (P<0.001). In the patients eligible for survival analyses, a median follow-up was 36 months. In women treated with endocrine alone, there were no difference of RFS between the patients with or without 21-gene RS (P=0.147). Also, the RFS did not differ between two groups with or without 21-gene RS, regardless of CRS (log-rank test, P=0.657 in the high-CRS group, and P=0.803 in the low-CRS group, respectively). Conclusions: These results supported that the application of 21-gene RS reduced the rate of chemotherapy in N0-1 patients with high CRS. Further study with a long-term follow up is needed to clarify an oncologic safety of a reduced the chemo-endocrine rate brought by 21-gene RS in terms of survival outcomes. Key words: breast neoplasm, adjuvant treatment, 21-gene recurrence score, chemotherapy Citation Format: Soong June Bae, Sung Gwe Ahn, Soeun Park, Chi Hwan Cha, Dooreh Kim, Janghee Lee, Joon Jeong. Application of 21-gene recurrence score in patients with T1-2, N0-1 ER-positive/HER2 negative breast cancer: Survival analysis in relation to clinical risk score [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-08-68.

Abstract P5-02-08: Androgen receptor pathway activity and the ratio between androgen and estrogen receptor pathway activity in breast cancer subtypes

Abstract Background: Androgen receptor (AR) immunohistochemistry staining in breast cancer has revealed frequent AR expression in all breast cancer subtypes. Activity of the AR signaling pathway can be either tumor suppressive or tumor promoting, depending on tumor context (Pharmacol Ther., In press, https://doi.org/10.1016/j.pharmthera.2019.05.005). For this reason, in an individual patient, AR phenotypic activity needs to be defined in order to choose the proper AR targeted therapy. The AR/ER protein ratio has been suggested as a biomarker to define this AR function and enable the appropriate therapy choice, i.e. androgen therapy in case of a low AR/ER protein expression ratio, and anti-androgen therapy in case of a high ratio. However, AR and ER expression are not necessarily associated with an active signaling pathway. Therefore we investigated the ratio between functional AR and ER pathway activities as this may have an advantage in guiding therapy choice. Methods: AR and ER pathway activity and AR/ER pathway activity ratio were determined on public Affymetrix HG-U133 Plus 2.0 gene expression microarray data of clinical breast cancer studies (available in the GEO database: GSE12276, GSE21653, GSE20685, GSE42568, GSE6532, GSE9195, GSE45827, GSE7307, GSE10780, GSE17907, GSE21422, GSE5764, GSE31192, GSE54002 and Array Express: E-MTAB-365; total n=2090). For this, we used previously described tests that enable quantification of functional pathway activity, based on Bayesian computational model inference of pathway activity from measurements of mRNA levels of target genes of the ER and AR transcription factor (Cancer Res., 2014, vol. 74, no. 11, pp. 2936-2945; Sci Rep., 2019, vol. 9, no. 1, p. 1603). Intrinsic subtyping of all samples has been done using the same methodology as described elsewhere (Am J Pathol, 2018, vol. 188, no. 9, pp 1956-1972).Results: AR pathway activity was increased in all breast cancer subtypes compared to normal breast tissue (p<0.0001); highest AR activity scores were observed in the HER2-enriched subtype. As shown before, ER activity scores were highest in luminal A and B subtypes. The AR/ER pathway activity ratio was low in luminal A and B, and comparable with normal tissue, but high in HER2 and basal breast cancer subtypes (p<0.0001). Discussion: Results are compatible with currently available evidence and show that the AR pathway can be activated in all breast cancer subtypes. We hypothesize that its function depends on the level of co-existent ER pathway activity, i.e. a tumor suppressive function in ER pathway active breast cancer, and a tumor promoting function in ER pathway inactive breast cancer. Upon future clinical conformation, the AR/ER pathway activity ratio as determined on an individual patient tissue sample may be an improved biomarker to guide the choice of (complementary) AR pathway targeted therapy in breast cancer, i.e. androgen receptor pathway inhibitors in case of a high ratio and potential use of androgen receptor modulators in case of a low ratio. Citation Format: Anja van de Stolpe, Yvonne Wesseling-Rozendaal, Marcia Alves de Inda, Henk van Ooijen, Wim Verhaegh. Androgen receptor pathway activity and the ratio between androgen and estrogen receptor pathway activity in breast cancer subtypes [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-02-08.

Association between ESR1, ESR2, HER2, UGT1A4, and UGT2B7 polymorphisms and breast Cancer in Jordan: a case-control study

BackgroundBreast cancer risk, development, and treatment are influenced by genetic variation in certain genes, namely those involved in cell proliferation, tumor suppression, and drug metabolism. In turn, the relevance of the aforementioned genetic variation to cancer depends on the ethnic group in question, highlighting the need for population-specific association studies. Therefore, the objective of the present study was to investigate the association between certain ESR1, ESR2, HER2, UGT1A4, and UGT2B7 single nucleotide polymorphisms and breast cancer.MethodsBlood samples were collected from 437 Jordanian-Arab breast cancer patients and healthy volunteers and subject to genotyping using the Sequenom MassARRAY® system (iPLEX GOLD).ResultsOur findings show a significant association between breast cancer and the allelic (P = 0.02486879) and genotypic (P = 0.04793066) frequencies of the ESR1 polymorphism rs3798577, a result which was confirmed in different genetic models. No other investigated polymorphism showed a significant association with breast cancer itself in Jordanian Arabs, but the Rare Hz (GG) vs Het (AG) genetic model revealed an association of the disease with the ESR1 polymorphism rs3798577. However, several associations were found between certain polymorphisms and breast cancer’s prognostic factors.ConclusionThis study suggests that certain polymorphisms may increase the risk of breast cancer in the Jordanian-Arab population. Future research and clinical translation could incorporate the current results in preventative breast cancer approaches tailored for Jordanian-Arab patients.

Omega-3 fatty acids and ERPR(-) and HER2/neu(+/-) breast cancer prevention.

TPS1589 Background: The most aggressive breast cancer subtypes tend to be estrogen and progesterone receptor negative (ERPR(-)) and human epidermal growth factor receptor type 2 positive (HER2(+)). Women with these breast cancer subtypes (triple negative, ERPR(-)HER2(+)) tend to experience worse clinical outcomes and have a relatively higher risk of recurrence. Our previous research demonstrated that dietary omega-3 (n-3) fatty acids can significantly inhibit ERPR(-) HER2(+) tumorigenesis in MMTV-HER2/neu transgenic mice fed fish oil vs corn oil-based diets. The fish oil diet group developed 30% fewer breast tumors, had lower Ki67 expression, and experienced less mammary atypia relative to the corn oil diet group. Other studies involving diet, nutrition and breast cancer point to the potentially protective effect of an anti-inflammatory diet on the risk of developing ER(-) and HER2(+) breast cancer, further supporting the evidence that the ERPR(-), HER2(±) subtypes may be highly responsive to this bioactive nutrient. Methods: This is a double-blinded, randomized clinical trial of high dose (~5.4 g EPA+DHA) vs low dose (~0.9 g EPA+DHA in fatty acid mix of the typical American diet) of n-3 fatty acids in breast cancer survivors of ERPR(-), HER2(±) breast cancer. Eligible participants will take 5 capsules/day for 12 months, with cellular samples of breast epithelial and/or adipose tissue obtained by fine needle aspirations of the contralateral breast. The study aims to determine whether n-3 fatty acid supplementation will modify fatty acid metabolite content in breast adipose tissue, modulate cytomorphology and/or cell proliferation in breast epithelial cells, affect DNA methylation patterns, and modulate pro- vs anti-inflammatory gene expression patterns in breast adipose tissue. Correlative aims will evaluate possible associations between factors such as breast adipose tissue, red cell membrane fatty acid profiles, BMI, and reported dietary intake. Sample size of 40 participants per arm was calculated to provide at least 80% power to detect a statistically significant difference for each primary endpoint. This study focuses on women survivors of high risk breast cancer subtypes, specifically triple negative or ERPR(-)HER2(+) disease, who are currently without long term adjuvant options. Eligibility criteria include prior diagnosis of ERPR(-) stage 0 to III breast cancer, ≤5 years from completion of standard therapy.The study was closed to accrual in November 2018; less than 9 months of follow-up remain for active study participants. Clinical trial information: NCT02295059.

Abstract P6-21-14: Targeting Rac/Cdc42 in human epidermal growth factor receptor 2 (HER2)-positive breast cancer

Abstract Breast cancer metastasis, when cancer cells move and establish tumors in distant organs, confounds treatment options. Therefore, there is an unmet need for targeted therapeutics to address metastasis, especially in the intractable HER2 positive (+) breast cancer type. HER2 (+) breast cancer is treated with the monoclonal HER2 antibody trastuzumab and the HER2/EGFR targeting small molecule lapatinib. However, ˜20% of early stage breast cancer patients and ˜70% of patients with metastatic disease are resistant to trastuzumab. Trastuzumab-resistant breast cancers circumvent HER2 inhibition via bypass signaling, which includes the PI3-K/Akt/mTOR pathway. HER2/EGFR and PI-3K/Akt signaling activate the Rho GTPases Rac and Cdc42, and overexpression of Rac or its downstream effector p21-activated kinase (PAK) significantly diminishes response to anti HER2 therapy and patient survival. Therefore, targeting Rac and Cdc42, pivotal regulators of cancer cell migration/invasion, and thus, metastasis, is a viable option to overcome HER2/EGFR therapy resistance. First, we designed and developed the Rac inhibitor Ehop-016 (US patents 8,884,006 B2, 9,278,956B1), which inhibits Rac activation with an IC50 of 1 μM and reduces breast cancer growth and metastasis in mouse models of trastuzumab resistant HER2 (+) breast cancer. A more potent dual Rac and Cdc42 inhibitor, MBQ-167 (US Patent 9,981,980 B2), inhibits Rac and Cdc42 activation with IC50s of 103 nM and 78 nM, respectively. In vivo, MBQ-167 inhibits trastuzumab resistant HER2 (+) mammary tumor growth and metastasis by ˜90-100% (Humphries-Bickley et al. 2017, Mol Cancer Therap). Therefore, Rac/Cdc42 inhibition blocks cell proliferation, cell cycle progression, migration, and induces apoptosis to ultimately impede tumor growth and metastasis in trastuzumab resistant HER2 (+) breast cancer models. To further investigate the role of Rac/Cdc42 inhibitors in overcoming HER2 therapy resistance, we developed a lapatinib resistant variant of the SKBR3 HER2 (+) breast cancer cell line and found that Rac was overexpressed and over activated in the therapy resistant variant compared to the parental cells. Accordingly, the Rac/Cdc42 inhibitors overcame lapatinib resistance by decreasing cell viability and inducing apoptosis in parental and SKBR3 therapy resistant variants. Pharmacokinetic analysis in mouse plasma demonstrated that the bioavailability of EHop-016 and MBQ-167 is ˜30% with a half-life of 3-4 h. Therefore, to increase the bioavailability of Rac/Cdc42 inhibitors and to facilitate sensitization of trastuzumab therapy, we designed and developed novel nanoliposomal formulations containing Rac/Cdc42 inhibitors with trastuzumab on the outer surface to target HER2 (+) breast cancer cells. This data demonstrates the utility of developing Rac/Cdc42 inhibitors as mono or combined therapy with current targeted therapeutics for HER2 (+) breast cancer. Citation Format: Rivera-Robles MJ, Medina-Vlazquez JI, Borrero-Garcia LD, Velazquez-Vega LE, Maldonado MdM, Ruiz-Calderon J, Castillo-Pichardo L, Vivas-Mejia P, Dharmawardhane S. Targeting Rac/Cdc42 in human epidermal growth factor receptor 2 (HER2)-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-21-14.

Abstract P1-06-02: Mismatch repair protein loss in breast cancer: Clinicopathological associations in a large British Columbia cohort

Abstract Background: Alterations to mismatched repair (MMR) pathways are a known cause of cancer (particularly colorectal and endometrial). Recently, the FDA approved pembrolizumab for use in MMR-deficient (MMRD) cancers of any type, and the diagnosis can be made by immunohistochemistry (IHC) or genomic methods. In breast cancer, mutational process analyses indicate MMRD occurs in about 2% of breast cancer (Cancer Res; 77; 4755-62, 2017) and recent functional studies have shown associations with resistance to endocrine therapy and sensitivity to CDK4/6 inhibitors (Cancer Discov; 7; 1168-83, 2017). To date, insufficient cases have been assembled to power meaningful associative or survival studies. Herein, the strong correlation between IHC-determined loss of MLH1, PMS2, MSH2 or MSH6 and genomic evidence allowed the assessment of MMRD on a large tissue microarray (TMA) series linked to detailed biomarkers and long-term outcome data. Methods: IHC markers MLH1, PMS2, MSH2 and MSH6 were optimized on the Ventana automated stainer for application to breast cancer TMAs. The patient cohort consists of females from British Columbia diagnosed with primary invasive breast carcinoma in 1986-1992, referred to the British Columbia Cancer Agency for treatment and follow-up. TMA blocks were sectioned and stained. Slides were scored by a pathologist and only nuclear positivity was evaluated positive. Loss of nuclear positivity for any one of the four tested marker defined MMRD. Clinicopathological associations were tested by Chi-square, and survival by Kaplan-Meier plot with log rank test. Result: 1635 cases were interpretable for all MMR markers. 31 cases (1.9%) met criteria for MMRD. 6 cases had paired losses (4 MLH1-PMS2 loss, 2 MSH2-MSH6 loss) and the remaining 25 cases had singular MMR loss (11 PMS2 loss, 10 MLH1 loss, 3 MSH6 loss, 1 MSH2 loss). Deficiency of the the MutL complex (MLH1/PMS2) predominated over the MutS complex (MSH2/MSH6). Among the demographic and pathological variables assessed – age, grade, tumour size, lymphovascular invasion, nodal and menstrual status – high grade is associated with MMRD (p=0.014). In terms of biomarker, MMRD is significantly associated with PR negativity (p=0.003) and PD-L1 expression (p=0.049), but not with ER, Her2, Ki67, or basal breast cancer IHC markers, nor does MMRD significantly correlate with any of the established major intrinsic subtypes of breast cancer. Tumor infiltrating lymphocyte (TIL) counts are higher in MMRD cases (p=0.009). Although statistically not significant (small numbers), Kaplan-Meier plots of survival analysis demonstrated a trend for MMR loss to be associated with decreased breast cancer disease-specific and overall survival. Conclusion: This large series assessed by IHC corroborates findings from smaller genomic series that MMRD is present in about 2% of breast cancers. MMRD tumors are more likely to be high grade, low PR and immunologically active (higher PD-L1 expression and TIL counts). MMR deficiency is present across all major molecular subtypes (luminal, HER2, basal). Given the efficacy of PD1/PDL1 targeting agents in MMR deficient tumors of other types, evidence for the activity of these agents in MMR deficient breast cancers should be actively sought. Citation Format: Cheng AS, Leung SC, Gao D, Anurag M, Nielsen T, Ellis MJ. Mismatch repair protein loss in breast cancer: Clinicopathological associations in a large British Columbia cohort [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-06-02.

Predictive value of in vitro methyl thiazolyl tetrazolium assay chemosensitivity test of cytotoxic drug activity in breast cancer

Objective To investigate the value of methyl thiazolyl tetrazolium assay (MTT) in predicting drug sensitivity of breast cancer cells in vitro. Methods From January 2010 to July 2016, one hundred and ninety-two patients with breast cancer who underwent modified radical mastectomy or breast conserving surgery (no preoperative radiotherapy or chemotherapy) in the Shanghai Fengxian District Central Hospital were selected.MTT method was used to determine the inhibitory level and sensitivity of 12 drugs and 3 chemotherapy regimens to primary cultured cancer cells of 192 patients with breast cancer. Results (1)The sensitivity of breast cancer cells to 12 drugs were in sequence from high to low as follows: Paclitaxel (PTX) > Epirubicin (EPI) > Cisplatin (DDP) > 5-Fluorouracil (5-FU) > Mitoxantrone (MIT) >Vincristine (VCR) > Pirarubicin (THP) > Isosophosphamide (IFO) > Carboplatin (CBP) >Cyclophosphamide (CTX) > Methotrexate (MTX) > Changchun Rui bin (NVB). The sensitivity of chemotherapy regimens in the three groups from high to low was docetaxel/doxorubicin/cyclophosphamide (TAC)>cyclophosphamide/epirubicin/fluorouracil (CEF)>cyclophosphamide/methotrexate/fluorouracil (CMF). The sensitivity rates of PTX, EPI and DDP were 54% (104/192), 42% (81/192) and 37% (71/192) respectively.(2) The average inhibitory rates of DDP, CBP and MIT in stage III breast cancer was higher than those in stage I and II breast cancer, and the differences were statistically significant (F=11.14, 4.303, 3.182, P<0.05). (3) HR-breast cancer is more sensitive than HR+ breast cancer, PTX, EPI, THP, MIT in HER-2(+ ) breast cancer is more sensitive than in HER-2(-)breast cancer. Conclusion As a widely used drug sensitivity test method, MTT assay has a certain reference value for screening sensitive drugs and selecting clinical chemotherapy regimens in neoadjuvant chemotherapy of breast cancer.PTX, EPI and DDP are more sensitive to other breast cancer cells than other drugs.Chemotherapy based on in vitro susceptibility results improves the efficiency of chemotherapy and decreases the proportion of changes in chemotherapy schemes due to inefficiency. Key words: MTT assay; Breast cancer; Cell; Chemosensitivity test

Abstract 3971: Combination of neratinib and enzalutamide is an effective treatment for HER2-positive breast cancer metastasis to the brain

Abstract An estimated 10% to 30% of all breast cancer patients eventually develop brain metastases. Up to half of the patients with epidermal growth factor receptor 2 (HER2)-positive breast cancer will develop brain metastasis. Treatment options for patients with breast cancer brain metastases are limited to surgical resection and radiotherapy with dismal median survivals of 2 to 24 months. Efforts to identify clinically relevant targeted therapeutics have been limited by the lack of molecularly characterized model systems. We have developed a patient derived xenograft (PDX) model of a HER2-positive breast cancer brain metastasis and have genomically characterized the PDX and its -matched tumor. Whole exome and RNA sequencing data revealed high fidelity of the PDX tumor with its corresponding patient-matched tumor and confirmed retention of driver gene alterations such as the amplification and overexpression of HER2. Additionally, immunohistochemistry of the patient tumor revealed overexpression of the Androgen receptor (AR) (IHC Score 2+), which was also confirmed in the PDX. Given the importance of both HER2 and AR in aggressive tumor behavior, we developed a preclinical study to inhibit both targets. Neratinib and enzalutamide were selected because of their known blood brain barrier penetration properties. As proof of concept we first tested the combination strategy in the flank of NOG mice (n = 10 animals/group). Tumors were allowed to grow to ~250 mm3 in size and animals were subsequently treated with either vehicle control, neratinib (40 mg/Kg) alone, enzalutamide (30 mg/Kg) alone, or combination for 2 weeks. Neratinib alone and thecombination with enzalutamide demonstrated exceptional efficacy in suppressing tumor growth as compared to either the vehicle control or Enzalutamide alone (5 fold reduction in tumor size, p &amp;lt; 0.001). Interestingly, when the treatments were stopped, tumors treated with Neratinib alone grew significantly faster compared to tumor growth with the combination treatment (p &amp;lt; 0.05), suggesting more effective and sustained tumor suppression by the addition of Enzalutamide. Studies in an orthotopic setting and molecular profiling of treated and non-treated tumors are ongoing. In summary, our results demonstrated that Neratinib in combination with Enzalutamide could potentially be developed for patients with HER2 and AR-positive breast cancer metastasis to the brain and warrants further preclinical testing. Citation Format: Harshil D. Dhruv, Lauren Hartman, Chris Gooden, George Reid, Christophe Legendre, George Snipes, Cynthia Osborne, Joyce O'Shaughnessy, Bodour Salhia. Combination of neratinib and enzalutamide is an effective treatment for HER2-positive breast cancer metastasis to the brain [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3971.