Deciphering the Molecular Basis of Breast Cancer Behavior using Proteomics and Genomics: STUDY 1 (Hameed): Quantification of Estrogen and Progestin Receptor Proteins as well as HER2/neu Oncoprotein Improves Discrimination of Breast Carcinoma Behavior

Immunohistochemical (IHC) analyses of ER, PR and HER2 proteins are used as clinical biomarkers for breast cancer management. However, IHC only gives semi-quantitative results due to variation in methods and interpretation which often complicate their use. We examined ER and PR in 1059 breast carcinomas quantified by radio-ligand binding and/or enzyme immunoassay (EIA) and measured HER2 oncoprotein by EIA to assess relationships between biomarker profiles. Disease-free (DFS) and overall survival (OS) were assessed for 123 patients. ER and PR were expressed as fmol/mg cytosol protein while HER-2 was expressed as HNU/mg membrane protein. Generalized pairs plots of biomarkers only indicated a relationship between ER and PR. Of 8 possible combinations of the three biomarkers, 46% of 123 cancers expressed ER+/PR+/HER2+ and exhibited good prognosis and survival by Cox regression and Kaplan-Meier plots using R software. Biopsies with profiles of ER+/PR-/HER2+ (11%) or ER+/PR+/HER2- (11%) exhibited poor prognosis and survival. Also biopsies exhibiting ER-/PR-/HER2- (Triple negative breast cancer, TNBC) were associated with decreased DFS and OS, as reported using IHC. When comparing biopsies expressing ER+/PR-/HER2+ (n=13) against the 7 other combinations (n=106), hazard ratios \u3e1 were observed, predicting poor prognosis and survival. Pre-menopausal patients (n=643) exhibited ER+/PR+/HER2- in 13% of cancers compared to 27% in post-menopausal patients (n=404). TNBC were observed in 10% of pre-menopausal patients and 3% of postmenopausal patients suggesting influence of endocrine status on biomarker profiles. Boxplots comparing the 8 biomarker profiles indicted two combinations with elevated ER/PR exhibited the best prognosis. Cox regressions determined that patients with similar ER status, gave significant hazard ratios of 0.30 (DFS) & 0.18 (OS) also indicating much better prognosis. Results reinforce the importance of assessing levels of the three biomarkers in a quantified fashion to enhance their use in breast cancer management and prediction of risk of recurrence