Gene expression profiling in immunophenotypic triple negative breast carcinomas harboring HER-2 amplification identifies tumors with distinct molecular signatures and increased ERBB2 gene expression

Introduction: Breast carcinomas can be classified by hormone receptors and human epidermal growth factor receptor-2 (HER-2) status. HER-2 status is assessed using immunohistochemistry (IHC) and/or fluorescent in situ hybridization (FISH). Immunophenotypic triple negative breast cancers (iTNBC) may harbor an amplification of HER-2 detected by FISH (iTNBC-FISHAmp) or may be negative by FISH (iTNBC-FISHNeg). The discrepancy between protein expression and gene amplification in these tumors poses relevant questions on tumor biology and for treatment implications. Here we investigate iTNBC-FISHAmp and iTNBC-FISHNeg by gene expression profile. Methods: A total of 40 iTNBC were selected. HER-2 IHC scores (0 or 1+) were annotated. All the tumors were tested by FISH showing 20 iTNBC-FISHAmp and 20 iTNBC-FISHNeg. The tumor morphology was reviewed by 2 pathologists, and stromal tumor infiltrating lymphocytes (sTILs) were estimated as high (H-sTILs) or low (L-sTILs). The areas of tumor with best cellularity were selected for RNA extraction. Gene expression profiling using a panel of 776 genes across 33 biological signatures was performed using Nanostring technology. Results: ERBB2 gene expression was significantly higher in iTNBC-FISHAmp when compared to iTNBC-FISHNeg tumors (p Citation Format: Paolo Cotzia, Theodore Vougiouklakis, Ursula Andreo, George Jour, Christopher Schwartz, Maryann Kwa, Sylvia Adams, Francisco Esteva, Deborah Axelrod, Freya Schnabel, Matija Snuderl, Farbod Darvishian. Gene expression profiling in immunophenotypic triple negative breast carcinomas harboring HER-2 amplification identifies tumors with distinct molecular signatures and increased ERBB2 gene expression [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-07-10.