Abstract B13: Predictive biomarkers for FAK inhibitor sensitivity in ovarian cancer
Authors: Shapiro Irina M. , Vidal Christian M. , Kolev Vihren N. , Weaver David T. , Pachter Jonathan A. 
Published: August 2014

Ovarian cancer is the fifth leading cause of cancer related death among women in the US and has the highest mortality rate among all gynecologic malignancies. Approximately 80% of patients diagnosed with ovarian epithelial cancer will relapse after first-line chemotherapy. Although targeted therapies tailored to specific genetic lesions have been developed for lung cancer, melanoma and CML, the molecular heterogeneity of the ovarian cancer genome has made it challenging to couple patient stratification markers with targeted agents.

Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that plays important roles in proliferation, cell survival, migration, invasion and cancer stem cell (CSC) renewal. FAK amplification and overexpression in ovarian cancer have been correlated with poor clinical outcome. In addition, high levels of phosphorylated FAK (pFAK) have been linked to poor prognosis and high ovarian tumor grade. Anti-tumor activity of the FAK inhibitors VS-6063 and VS-4718 has been previously demonstrated in preclinical models including ovarian cancer xenograft models (1,2).

We have aimed to identify molecular markers predictive of ovarian cancer sensitivity to FAK inhibitors. Human ovarian cancer cell lines were analyzed for FAK inhibitor sensitivity in 3D Matrigel culture that mimics the ovarian tumor microenvironment. We then performed gene expression analysis of ovarian cancer cell lines most sensitive or least sensitive to FAK inhibitor treatment and identified a 64 gene signature that unambiguously clustered cell lines into sensitive and resistant subgroups (fold change &gt;2, AUC &gt;0.85). The gene signature associated with increased sensitivity to VS-4718 contained 27 genes with elevated expression, such as SLIT2, and 37 genes with decreased expression, such as LPNH2. Gene expression data were validated using qPCR as well as Western blot analysis to assess corresponding protein expression levels. As these genes may be important predictive biomarkers for patient selection or stratification, the variability of gene expression across human ovarian tumors was investigated using RNA microarray data of 733 patient tumor specimens derived from 5 study groups. As desired, SLIT2, LPNH2, and other genes in the signature exhibited a broad range of expression in ovarian tumor samples. Seven genes encoded for secreted proteins which could enable development of detection assays in blood. To assess regional expression of some of the above biomarkers within the tumor, we used immunohistochemistry analysis of a human ovarian Tissue MicroArray (TMA).

Potential biomarkers were then evaluated in an independent test set of ovarian cancer samples. We first analyzed expression of the 64-gene signature in RNA microarray datasets from 6 ovarian patient-derived xenograft (PDX) models to predict their response to FAK inhibitor treatment. Then, an ex vivo clonogenic 3D assay was used to assess cell viability of ovarian PDX samples treated with FAK inhibitor. Interestingly, expression of several markers correlated with sensitivity to FAK inhibitor. In a similar fashion, we analyzed cell viability of ovarian cancer surgical samples from patients following ex vivo treatment with the FAK inhibitor. Tumors that expressed high levels of a number of genes from the 64 gene signature were especially sensitive to FAK inhibitor ex vivo.

Our data identify biomarkers predictive of response to FAK inhibition in ovarian cancer models and provide a rationale for validation of these markers in a clinical trial of a FAK inhibitor in patients with ovarian cancer.

References:

1) Yu K. et al, (JNCI, in press).

2) Ward K.K. et al, Clin Exp Metastasis. 2013 Jun; 30(5):579-94.

Citation Format: Irina M. Shapiro, Christian M. Vidal, Vihren N. Kolev, David T. Weaver, Jonathan A. Pachter. Predictive biomarkers for FAK inhibitor sensitivity in ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr B13.