Cell Plasticity Associated to Taxane-Resistance in Preclinical Cell Models and in Circulating Tumor Cells from Metastatic Castration-Resistant Prostate Cancer Patients.

238 Background: Treatment resistance is associated with tumor cells molecular plasticity. In metastatic castration resistant prostate cancer (mCRPC), alterations in androgen receptor (AR) have been described as predictors of shorter response to hormonal treatments. Previously, we associated epithelial to mesenchymal transition (EMT) phenotype with chemotherapy resistance. However, other molecular changes responsible of such resistance should be elucidated. Here, we investigate the effect of taxanes on cell plasticity through in vitro models and in circulating tumor cells (CTCs) from mCRPC patients. Methods: Molecular differences due to taxane-exposure were evaluated in cell models of mCRPC (PC-3 and DU-145 resistant to taxanes). Global gene expression (GE) analysis was performed using Affimetrix GeneChip Human Gene 2.0 arrays. GE related with AR axis, EMT and neuroendocrine (NE) phenotypes was validated by quantitative (qRT-PCR). Clinical validation was performed in CTCs from 24 mCRPC patients collected prior and post taxane-treatment. CTCs enrichment was achieved by Isoflux technology through a personalized combination of EpCAM, CDH2 and PSCA antibodies. Results: GE analysis revealed a different deregulation pattern related to the EMT, NE and AR-related phenotypes in resistant CRPC-cells compared to parental cells. Docetaxel resistance was more associated to an EMT phenotype while cabazitaxel resistance to NE patterns. GE patterns in CTCs at post taxane-treatment showed a common upregulation of AR-related genes compared to pre-treatment collected samples. Moreover, most patients experienced upregulation of EMT and NE markers after treatment, which was more pronounced after docetaxel than cabazitaxel therapy. Conclusions: GE changes related to taxane-resistance observed in pre-clinical models also occur in CTCs. This supports the great value of CTCs to evaluate cell plasticity due to taxanes treatment. Further investigation is ongoing to better characterize cellular plasticity and to improve personalized therapeutic strategies that would enhance better clinical outcomes in mCRPC.