Abstract 1994: Defining peritumoral and tumoral stromal gene signatures associated with response to neoadjuvant chemotherapy in breast cancer

Abstract

Abstract Neoadjuvant chemotherapy (NACT) is used in breast cancer to decrease tumor and lymph node burden and the extent of surgery. However, response is variable and prediction poor. Stromal cells are involved in breast cancer progression and drug resistance although very little is known about the mechanisms. Our research aims to characterize breast cancer-associated fibroblasts (CAFs) and peritumoral fibroblasts (PTFs) that predict response to NACT and could be used to influence treatment choices. Pre-NACT core biopsies from cancer-associated and peritumoral tissues were collected under ultrasound guidance. To date, mRNAs from early passage (passage ≤ 5) fibroblasts isolated from cores of 23 matched pairs (CAFs and PTFs) (8 triple-negative (TNBC), 7 ER+Her2+ and 8 ER+Her2- tumors) and an additional 8 PT samples (4 TNBC, 1 ER+Her2+ and 3 ER+Her2-) have been analysed by whole-genome expression array (Illumina beadchip HT12v4). Data were analysed with Partek® Genome SuiteTM 6.6 and Pathway softwares (Partek Inc., St. Louis, MO, USA). Differentially expressed genes (DEGs) were identified (t-test, p-value ≤ 0.05, fold-change (FC) ≥ 1.3) between CAFs and PTFs and between NACT responders (Residual Cancer Burden (RCB) 0/1) and non-responders (RCB 2/3). No significant difference between CAFs and PTFs was seen by principal component analysis and t-test. PTFs showed similar mRNA levels of major myofibroblast markers (e.g. FAP, ASMA) with only FSP1 being lower in PTFs compared to CAFs (FC = -1.4, p-value = 0.023), suggesting that PTFs, like CAFs, are activated myofibroblasts. We then tried to identify a gene signature in CAFs or PTFs that could predict response to NACT. Comparing RCB 0/1 vs RCB 2/3 resulted in very few DEGs due to cancer subtype variation in both CAFs and PTFs. Similar to other studies, only 2/19 patients in our cohort with ER+ tumours achieved RCB 0/1, preventing analysis of these samples. However, 45% (5/11) TNBC responded to NACT and we identified 566 DEGs between RCB 0/1 and RCB 2/3 CAFs, with changes in metabolism, Pi3K/AKT pathway, proteoglycan synthesis or ECM-receptor interaction. For PTFs, 186 DEGs were identified, with changes in Wnt signalling and ECM-receptor pathways. Microarray data from our uniquely large sample set of 23 pairs of CAFs and PTFs from breast cancer patients suggest that PTFs have a similar gene expression profile to CAFs. Although others have demonstrated that CAF phenotype is breast cancer subtype dependent, we are the first to show similar observations in PTFs. Finally, we identified gene signatures from both CAFs and PTFs that relate to NACT response in TNBC. We are currently in the process of confirming the most highly dysregulated genes by qPCR and/or immunohistochemistry analysis. Citation Format: Celine Pourreyron, Violet Warwick, Patsy Whelehan, Philip Coates, Lee Jordan, Colin Purdie, Sarah Vinnicombe, Alastair Thompson, Andrew Evans, Frances Fuller-Pace. Defining peritumoral and tumoral stromal gene signatures associated with response to neoadjuvant chemotherapy in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1994. doi:10.1158/1538-7445.AM2017-1994