Anti-ERBB3 monoclonal antibody, clone F297

Breast cancer is the leading cause of cancer related deaths in women worldwide and is classified into subtypes based on the cancer's receptor status. Of these subtypes, those expressing the human epidermal growth factor receptor 2 (HER2) receptor were traditionally associated with poor prognosis. Several advances have been made in the treatment of HER2-positive breast cancer, yet issues of resistance and poor response to therapy remains prevalent. In this study we explored the impact of HER-family and homologous recombination deficiency SNPs on response to patients who received TCH-based (docetaxel (T), carboplatin (C), and trastuzumab (H)) treatment versus those who received other treatment regimens. Using Cox regression analysis, we identified 6 SNPs that correlate with recurrence free survival in our patients and supported our findings using support vector machines. We also used reverse phase protein array analysis to examine the impact ERBB3 SNPs may have on both the PI3K/AKT and MAPK/ERK signaling pathways. Finally, using cell line models, we correlated SNP status with sensitivity to platinum based drugs and docetaxel. We found that patients on a TCH based regimen with the minor allele of the ERBB3 (rs2229046 and rs773123) and BARD1 (rs2070096) SNPs, were significantly more likely to relapse than those women who were not. Additionally, we observed that patients with these ERBB3 SNPs had shown elevated protein expression/phosphorylation of Src kinase, c-MET (Y1234/1235), GSK-3p (S9) and p27, indicating that these SNPs are associated with non-PI3K/AKT signaling. Finally, using cell line models, we demonstrate that the BARD1 SNP (rs2229571) is associated with greater sensitivity to both carboplatin and cisplatin. The BARD1 and ERBB3 SNPs can potentially be used to determine those patients that will have a worse response to TCH based treatment, an effect that may arise from the SNPs impact on altered cellular signaling.

Purpose: Preclinical data identified the cyclin-dependent kinase 4/6 (CDK4/6) inhibitor palbociclib as synergistic with antiestrogens in inhibiting growth of hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) human breast cancer models. This observation was validated clinically in the randomized, placebo-controlled, phase III PALOMA-2 study. Experimental Design: To determine markers of sensitivity and resistance to palbociclib plus letrozole, we performed comprehensive biomarker analyses, investigating the correlation with progression-free survival (PFS), on baseline tumor tissues from PALOMA-2. Results: Despite a broad biomarker search, palbociclib plus letrozole demonstrated consistent PFS gains versus placebo plus letrozole, with no single biomarker or cassette of markers associated with lack of benefit from combination treatment. Palbociclib plus letrozole confers efficacy on both luminal A and B patients. Higher CDK4 levels were associated with endocrine resistance which was mitigated by the addition of palbociclib, whereas lower PD-1 levels were associated with greater palbociclib plus letrozole benefit. Tumors with more active growth factor signaling, as exemplified by increased expression of FGFR2 and ERBB3 mRNA, appeared to be associated with greater PFS gain from the addition of palbociclib. Conclusions: These data underscore the importance of CDK4/6 signaling in HR+/HER2- breast cancer and suggest that the interplay between steroid hormone and peptide growth factor signaling could drive dependence on CDK4/6 signaling.