Abstract P5-05-05: Patient-derived triple negative breast cancer xenografts as a translational model to screen for novel kinase pathways

Abstract

Abstract Overall, triple negative breast cancers (TNBCs) constitute 12% of all breast cancers, and is approximately twice more prevalent in African-American populations. Louisiana has a high proportion of African-American residents (32.5% in 2015), and thus hosts a higher population of TNBC patients. TNBCs have an aggressive phenotype that is elusive to the targeted therapeutics used to treat other breast cancer subtypes. Certain kinase families have been extensively studied as regulators of epithelial-mesenchymal transition (EMT), a process involved in the initiation of cancer metastasis. Discovery of novel kinase targets within the subset of uncharacterized kinases could provide important insight into future targeted therapies. However, current models utilized in target discovery research are limited by the inability to accurately recapitulate the complex stromal architecture and heterogenous genetic and molecular composition of breast cancer. Furthermore, immortalized cell lines are limited to a 2D environment and over time acquire mutations that may not reflect the primary tumor. Recently, our laboratory has successfully established two TNBC patient-derived xenograft (PDX) models derived from African-American patients, and generated cell lines (TU-BCx-2K1, TU-BCx-2O0) and mammospheres. One of these models, 2O0, presents tumor architecture, cellular composition, genomic (qRT-PCR) and protein (western blot) expressions that are concordant with a claudin-low subtype, which has higher rates of metastasis and recurrence. Furthermore, we show that both TNBC models metastasize to the lungs, and exhibit molecular characteristics consistent with mesenchymal phenotypes. We utilized these translational PDX models to screen a library of small molecule inhibitors that represent a variety of kinase pathways to identify novel therapeutic targets and/or pathways that are specific to TNBC subtypes. We found in a preliminary cell morphology screen using three TNBC cell lines (MDA-MB-231, BT549, MDA-MB-157), two small molecule inhibitors that increased epithelial marker (CDH1) gene expression, suppressed mesenchymal (VIM, c-FOS, SNAI1, ZEB1) expression and/or suppressed cellular motility in transwell migration assays. We observed after ex vivo treatments with our PDX tumors the two compounds increase the epithelial marker CDH1 expression, and suppress mesenchymal markers (VIM, MMP2, c-FOS, SNAI1, ZEB1) expressions. We confirm these findings in the TU-BCx-2K1 cell line. Kinase array data revealed candidate kinases responsible for the observed EMT changes in the two compounds of interest (NEK5, NEK9, NEK1 potentially affect cell motility; SRC-family kinases, TAOK2, STK10 potentially affect EMT gene changes); we plan to utilize the PDX cell lines to characterize these kinases in EMT. We aim to ultimately discover novel therapeutic targets specific to different TNBC molecular subtypes. Citation Format: Matossian M, Burks H, Bowles A, Sabol R, Hoang V, Elliott S, Bunnell B, Zuercher W, Drewry D, Wells C, Alfortish A, Lee S, Hartono A, Jones S, Moroz K, Zea A, Burow M, Collins-Burow B. Patient-derived triple negative breast cancer xenografts as a translational model to screen for novel kinase pathways [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 P5-05-05.