Identification of predictive and surrogate molecular markers for dasatinib in prostate cancer: Rationale for patient selection and efficacy monitoring

Abstract

3579 Background: Dasatinib is a potent, multi-targeted kinase inhibitor that was recently approved for treatment of chronic myelogenous leukemia resistant to imatinib. To aid its clinical development in prostate cancer, we used a panel of prostate cancer cell lines to identify molecular markers that could be used to predict sensitivity to dasatinib and to monitor its activity. Methods: Baseline gene expression profiles of 16 cell lines were used to identify predictive biomarkers based on the correlation of gene expression with in vitro sensitivity of cells to dasatinib. Selected cell lines were treated with dasatinib to identify surrogate biomarkers based upon changes in gene expression following dasatinib treatment. Results: We identified 174 genes whose baseline expression levels were highly correlated with sensitivity or resistance to dasatinib. These include cell lineage markers cytokeratin 5 (CK5), androgen receptor (AR), and prostate specific antigen (PSA). Our results indicate that “basal type” cell lines (those with high expression of CK5 and low expression of AR and PSA) are sensitive to dasatinib. Dasatinib treatment studies further identified genes whose expression levels were significantly modulated by the drug. Ten genes, including urokinase-type plasminogen activator (uPA), were not only significantly correlated with sensitivity to dasatinib but also reduced in their expression upon drug treatment. In addition, the down-regulation of uPA was specific to dasatinib and the effect was not seen in taxol-treated cells. The extent of down-regulation was correlated with the sensitivity of cell lines to dasatinib. EphA2, a specific kinase target of dasatinib, was identified as a biomarker common to prostate and breast cancers. Finally, the expression of 5 genes including CK5, AR, PSA, uPA and EphA2 in prostate tumors was examined and the dasatinib sensitivity signature was validated using a published data set derived from a clinical population. Conclusions: Candidate markers correlated with dasatinib sensitivity were identified. A five-gene model consisting of predictive markers as well as potential surrogate markers has been formulated and will be evaluated in ongoing dasatinib prostate cancer trials. No significant financial relationships to disclose.