Abstract 3457: Gender-associated expression of tumor markers and a small gene set in breast carcinoma.

Abstract

Abstract In 2011, carcinoma of the breast in men accounted for ∼1% of all breast cancers in the US, and approximately 450 male patients died from this disease. Although breast carcinomas in both genders share certain pathological features, notable differences have been observed regarding incidence, prognosis and survival. Results from microarray analyses in our studies and those of other reports were used to select 33 candidate genes to investigate in male breast carcinomas. Tumor marker results for 99 male breast cancers and ∼18,000 female breast carcinomas were extracted from our IRB-approved comprehensive database. Estrogen receptor (ER) and progestin receptor (PR) levels were determined by either radio-ligand binding (NEN/DuPont) or enzyme immunoassay (Abbott Labs). HER-2/neu levels were determined by either ELISA (Oncogene Science) or EIA (Triton Biosciences), and epidermal growth factor receptor (EGFR) levels were determined by an in-house radio-ligand competition assay. RNA was isolated from tissue sections of de-identified frozen biopsies from 12 male patients and 233 female patients using the RNeasy Mini kit (Qiagen) and analyzed for quality and quantity (Agilent Bioanalyzer). cDNA for qPCR measurements was prepared in Tris-HCl buffer with KCl, MgCl2, DTT (Invitrogen), dNTPs (Invitrogen), RNasin (Promega) and Superscript RT III (Invitrogen). qPCR reactions were performed using Power Sybr Green PCR Master Mix (Applied Biosystems), forward/reverse primers and cDNA obtained from the reverse transcription reaction. Relative gene expression was calculated by the ddCt method using β-actin as a reference and Universal Human Reference RNA (Stratagene) as a calibrator. Among 99 male breast cancers, 82 were ER positive and 78 exhibited PR. Levels of ER (P = 0.013) and PR (P < 0.001) protein were greater in male breast cancers compared to biopsies from female patients, although no difference was observed in the expression of ESR1 and PGR genes that encode these receptors. In contrast, no differences were observed in either of the other conventional breast cancer biomarkers, HER-2/neu or EGFR protein, nor in patient age at diagnosis. However, there was a difference in the binding affinities (Kd value) of PR (P = 0.004) between the genders, which was not observed in ER between male and female breast cancer tissues. Furthermore, expression levels of six genes (NAT1, TBC1D9, IL6ST, RABEP1, PLK1 and LRBA) that we and others have suggested serve as indicators of risk of recurrence, were elevated in male breast cancer biopsies compared to those from female patients (P < 0.05). Preliminary results suggest that over-expression of the protein product of one or more of the genes identified represents a molecular target that warrants further exploration for development of a gender specific therapeutic and companion diagnostic. Supported in part by a grant from Phi Beta Psi Charity Trust and a CTSP Award from the Commonwealth of Kentucky. Citation Format: Sarah A. Andres, Irina A. Smolenkova, James L. Wittliff. Gender-associated expression of tumor markers and a small gene set in breast carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3457. doi:10.1158/1538-7445.AM2013-3457