Abstract PD8-02: Mechanisms of recurrence: Paired analysis of primary and metastatic triple negative breast cancer

Abstract

Abstract Background: Triple negative breast cancer (TNBC) is the most aggressive subtype of invasive breast cancer that lacks ER, PR, and HER2 expression. It is a heterogeneous disease with several molecular subtypes: basal-like1 (BL-1), basal-like 2 (BL-2), mesenchymal (M), and luminal androgen receptor (LAR). Treatment for TNBC is normally limited to chemotherapy, and relapse is common. Here we report molecular alterations associated with TNBC metastasis by analyzing the genomic profiles of paired primary and metastatic TNBCs. Methods:50 paired TNBCs were identified through an IRB-approved protocol via the City of Hope (COH) Biospecimen Repository. DNA mutation and mRNA expression profiles of 10 paired primary and metastatic TNBCs were analyzed. DNA mutations were identified using exome sequencing by FoundationOne®. Affymetrix Human Genechip 2.0 was used for mRNA expression profiling. Raw data were normalized and processed using Expression Console, and linear regression was performed using Limma to identify the differentially expressed genes between primary and metastatic TNBCs. Results: DNA mutation profiling showed that multiple mutations occurred within genes covering pathways of PI3K/AKT/mTOR, DNA repair, RAS/MAPK, cell cycle, and growth factor receptor signaling, reconfirming genomic heterogeneity of TNBCs. Gene expression profiles were analyzed for Lehmann's TNBC molecular subtypes (BL-1, BL-2, M, and LAR). Six of ten TNBCs showed phenotype shift between the primary and metastatic TNBCs. Several unique gene expression patterns were identified by comparing the paired TNBCs. CCNE1 and TPX2 were co-overexpressed in metastatic TNBCs compared to paired primaries. This mirrored prior studies in ovarian cancer, where co-overexpression of CCNE1 and TPX2 were found related to clonal resistance against chemotherapy. Splicing factors TRA2B and SRSF7 were also over-expressed in metastatic TNBCs compared with primaries. The analysis studying the association of CCNE1 and TPX2 with overall survival is ongoing using TCGA. Conclusion: Overall, these results show the comparative changes between primary and relapsed TNBCs and indicate the heterogeneity of molecular mechanisms of recurrence. CNNE1 and TPX2 may represent important genes involved in TNBC metastasis. Further analyses including a total of 50 paired TNBCs are currently underway. Study Contact: Yuan Yuan MD PhD, City of Hope Comprehensive Cancer Center; Duarte, CA 91030; Email: yuyuan@coh.org Citation Format: Zhao Z-M, Yost S, Yuan Y-C, Warden C, Chuang J, Yuan Y. Mechanisms of recurrence: Paired analysis of primary and metastatic triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD8-02.