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Abstract Drugs targeting the DNA damage response (DDR) are widely used in cancer therapy, but resistance to these drugs remains a major clinical challenge. Here, we show that SYCP2, a meiotic protein in the synaptonemal complex, is aberrantly and commonly expressed in breast and ovarian cancers and associated with broad resistance to DDR drugs. Mechanistically, SYCP2 enhances the repair of DNA double-strand breaks (DSBs) through transcription-coupled homologous recombination (TC-HR). SYCP2 promotes R-loop formation at DSBs and facilitates RAD51 recruitment independently of BRCA1. SYCP2 loss impairs RAD51 localization, reduces TC-HR, and renders tumors sensitive to PARP and topoisomerase I (TOP1) inhibitors. Furthermore, our studies of two clinical cohorts find that SYCP2 overexpression correlates with breast cancer resistance to antibody-conjugated TOP1 inhibitor and ovarian cancer resistance to platinum treatment. Collectively, our data suggest that SYCP2 confers cancer cell resistance to DNA-damaging agents by stimulating R-loop-mediated DSB repair, offering opportunities to improve DDR therapy.

Triple negative breast cancer (TNBC) is a heterogenous subtype of breast cancer often associated with an aggressive phenotype and poor prognosis. Antibody–drug conjugate (ADC), comprising of a monoclonal antibody linked to a cytotoxic payload by a linker, is gaining increasing traction as an anti-cancer therapeutic. Emerging ADC drugs such as sacituzumab govitecan (IMMU-132) and trastuzumab deruxtecan (DS-8201a) are in late stages of clinical development for patients with metastatic breast cancer, including TNBC. In this article, we review and discuss the development and clinical application of ADCs in patients with advanced TNBC.

Abstract Background Eribulin mesylate is currently indicated as a sequential monotherapy to be administered after two chemotherapeutic regimens, including anthracycline and taxane treatments, for treatment of metastatic breast cancer. This open-label, multicenter phase II study was designed to evaluate the efficacy and safety of eribulin as a first- or second-line treatment for patients with metastatic breast cancer. Methods The primary objective was to determine the overall response rate. Secondary objectives were to evaluate progression-free survival and the safety profile. Patients were scheduled to receive eribulin mesylate 1.4 mg/m2 intravenously on days 1 and 8 of a 21-day cycle. Patients received the study treatment unless disease progression, unacceptable toxicity, or a request to discontinue from the patient and/or investigator eventuated. Results Between December 2012 and September 2015, 32 patients with metastatic breast cancer were enrolled at 10 participating clinical institutions in Japan, and toxicity and response rates were evaluated. The overall response rate was 43.8% (95% confidence interval [CI] 26.5–61.0). The clinical benefit and tumor control rates were 56.3% (95% CI 39.0–73.5) and 78.1% (95% CI 63.8–92.5), respectively. Median progression-free survival was 8.3 months (95% CI 7.1–9.4). A subgroup analysis did not identify any factors affecting the efficacy of eribulin. The most common adverse events were neutropenia (71.9%), alopecia (68.7%), and peripheral neuropathy (46.9%). As a first- or second-line therapy, eribulin showed sufficient efficacy for metastatic breast cancer compared with taxane and capecitabine treatment in previous clinical trials. The safety profile of eribulin was acceptable. Conclusions Eribulin may be another option for first-line chemotherapeutic regimens for metastatic breast cancer. Trial registrations This trial was retrospectively registered at the University Hospital Medical Information Network (UMIN) Clinical Trial Registry (ID number: UMIN000010334). Date of trial registration: April 1st, 2013.

The response of triple-negative breast cancer (TNBC) to chemotherapy is heterogeneous; particular subtype classifications based on mRNA gene expression analysis have been demonstrated to be associated with a pathological complete response (pCR). The aim of the present study was to investigate additional clinical and pathological characteristics associated with pCR status. The pathological and clinical characteristics of 40 TNBC patients who underwent neoadjuvant chemotherapy followed by surgery were retrospectively analyzed by dividing the cases into two groups according to the response to treatment: pCR (n=12) and non-pCR (n=28). Clinically, patients in the pCR group presented tumors with a significantly less advanced Tumor-Node-Metastasis stage (P=0.030) and mammographic calcification was less common (17 vs. 58%; P=0.034). Pathologically, whereas all cases in the pCR group (12/12, 100%) were of the histological type 'invasive ductal carcinoma, not otherwise specified' (IDC-NOS), the non-pCR group consisted of a lower proportion of IDC-NOS cases (20/28, 71%) and more cases of special histological types, including mucinous, metaplastic, medullary and apocrine carcinomas (P=0.079). The positive rates of androgen receptor (AR) and forkhead-box A1 (FOXA1) tended to be lower in the pCR group (AR, 0 vs. 29%, P=0.079; FOXA1, 8 vs. 29%, P=0.233). The Ki-67 score was significantly higher in the pCR group than in the non-pCR group (P=0.041). The results suggest that patients with TNBC who present with clinically less advanced tumors and less frequent mammographic calcification are more likely to respond to chemotherapy. From a pathological standpoint, IDC-NOS type, negative AR status and higher Ki-67 scores may be associated with chemotherapy sensitivity. [ABSTRACT FROM AUTHOR]

The article presents a response from the authors regarding their study of network meta-analysis of neoadjuvant therapy for human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Topics discussed include the addition of lapatinib (lpnb) to chemotherapy (CT) with trastuzumab (tzmb); the use of lpnb as a partner agent for dual HER2 blockade; and network meta-analysis.