Generation of α-EPCR monoclonal antibodies and their use in the development of an antibody-based targeting therapy of invasive prostate cancer

Background: Despite androgen deprivation treatment, hormone-relapsed prostate cancer (HRPC) typically progresses to metastasis - metastatic prostate cancer remains incurable and there is a clear unmet clinical need to identify new therapeutic approaches. A previous study carried out by our team demonstrated that the expression of the human Endothelial Protein C Receptor (EPCR, CD201) in prostate cancer cells in vitro is associated with Epithelial to Mesenchymal Transition (EMT), a key element of the metastatic pathway. Hypothesis: That targeting of prostate cancer cells expressing EPCR using a monoclonal antibody (mAb) has therapeutic potential against aggressive, metastatic prostate cancer. Aims of the Study: To develop mAbs against the human EPCR and evaluate their therapeutic potential by assessing their capacity to target and kill invasive prostate cancer cells in vitro and in vivo. Experimental Approach: Functional analysis of prostate cancer cell lines expressing a construct for knock down of EPCR were performed in order to validate EPCR as a valid target for immunotherapeutic treatment of aggressive prostate cancer. Four murine mAbs against EPCR were generated, the hybridomas sequenced and recombinant mAbs produced. The specificity of the purified mAbs was confirmed using flow cytometry, immunofluorescence, ELISA and immunoblotting assays. An in vitro antibody-dependent cell-mediated cytotoxicity (ADCC) reporter assay demonstrated the ability of the recombinant mAbs to mediate ADCC against human prostate cancer cell lines (DU145, PC3). These results were further investigated in vivo using a CB17/SCID mouse xenograft tumour model. Recombinant mAbs did not produce any significant effect on tumour growth rate or metastasis formation in vivo. Summary and Impact: We have generated a new panel of mAbs against EPCR/CD201 which have the potential to form the basis of new therapeutic approaches for treating aggressive, metastatic prostate cancer based on the triggering of ADCC or the delivery of Antibody-Drug Conjugates (ADCs). This project also opens the way to the development of therapies based on EPCR chimeric antigen receptor (CAR) T cells and bispecific antibodies