SignificanceMass spectrometry-based proteogenomics of patient-derived xenografts (PDXs) identified dihydropyrimidinase-like-3 (DPYSL3) as a multilevel (RNA/protein/phosphoprotein) expression outlier specific to a claudin-low (CLOW) PDX. DPYSL3 has established functions in neural cell migration and axon outgrowth but is understudied in breast cancer. Here, we demonstrate that loss of DPYSL3 promotes cell-cycle arrest, multinucleation, and collapse of the vimentin microfilament network associated with increased phospho-vimentin. DPYSL3 is also a negative regulator of p21-activated kinase (PAK) and suppresses epithelial-to-mesenchymal transition (EMT). In turn, EMT regulators induce DPYSL3, suggesting that DPYSL3 provides negative feedback on EMT. DPYSL3 therefore serves as a biomarker for CLOW tumors that exhibit PAK-dependent motility and EMT and is also susceptible to therapeutic approaches that promote vimentin phosphorylation during mitosis.

Male breast cancer (MBC) is now considered molecularly different from female breast cancer (FBC). Evidence from studies indicates that common genetic and epigenetic features of FBC are not shared with those diagnosed in men. Genetic predisposition is likely to play a significant role in the tumorigenesis of this rare disease. Inherited germline variants in BRCA1 and BRCA2 account for around 2% and 10% of MBC cases, respectively, and the lifetime risk of breast cancer for men harboring BRCA1 and BRCA2 mutations is 1.2% and 6.8%. As for FBC, pathogenic mutations in other breast cancer genes have also been recently associated with an increased risk of MBC, such as PALB2 and CHEK2 mutations. However, while multigene germline panels have been extensively performed for BC female patients, the rarity of MBC has resulted in limited data to allow the understanding of the magnitude of risk and the contribution of recently identified moderate penetrance genes of FBC for MBC predisposition. This review gathers available data about the germline genetic landscape of men affected by breast cancer, estimated risk associated with these genetic variants, and current guidelines for clinical management.

Objective To identify the biomarkers of response to neoadjuvant chemotherapy in early luminal breast cancer. Methods A cross-sectional study that included all patients with early or locally-advanced luminal breast cancer submitted to neoadjuvant chemotherapy between 2013 and 2014. Demographic, clinic and pathologic data were retrieved from patient records. The expressions of the estrogen receptor (ER), the progesterone receptor (PR), and Ki67 were analyzed by immunohistochemistry (IHC). The status of the human epidermal growth factor receptor 2 (HER2) was evaluated by IHC and fluorescent in situ hybridization (FISH). Independent predictors of clinic and pathologic response were evaluated by stepwise logistic regression models and receiver operating characteristic (ROC) curve analysis. Results Out of 298 patients identified, 115 were included in the analysis. Clinical complete response (cCR) was observed in 43.4% of the patients (49/113), and pathologic complete response (pCR) was observed in 7.1% (8/115) of the patients. The independent predictors of cCR were premenopausal status (p < 0.001), low PR expression (≤ 50% versus > 50%; p = 0.048), and Ki67 expression ≥ 14% (versus < 14%; p = 0.01). Patients with cCR were more commonly submitted to breast conserving surgery (34.7% versus 7.8%; p < 0.001). Increasing cut-off points for Ki67 expression were associated with an increase in specificity and a decrease in sensitivity to identify patients with cCR. Conclusion Premenopausal status, lower PR expression and higher Ki67 expression were associated with a higher rate of cCR to neoadjuvant chemotherapy in luminal breast cancer.