Yoneda, et al. 1 Overexpression of SOCS3 mediated by adenovirus vector in mouse and human castration resistant prostate cancer cells increases the sensitivity to NK cells in vitro and in vivo.

Recently, the US FDA approved sipuleucel-T, which is composed of autologous DCs stimulated with a recombinant fusion protein of prostatic acid phosphatase (PAP) and granulocyte-macrophage colony-stimulating factor (GM-CSF), as the first immunotherapeutic agent for metastatic castration resistant prostate cancer (mCRPC). However, sipuleucel-T demonstrated only modest efficacy in mCPRC patients. Researchers are now investigating the potential of p53 protein as a tumor-associated antigen (TAA) loaded in DC-based cancer vaccine. Approximately half of all tumors overexpress p53, and up to 20% of prostate cancer cells overexpresses p53. In this study, we evaluated the feasibility of combining p53-DC vaccine and rAd-p53 gene therapy, using the p53-overexpressing and non-expressing prostate cancer cells in vitro. We successfully generated the p53-DC vaccine by culturing autologous DCs infected with rAd-p53. This p53-DC vaccine can differentiate CTLs specifically cytotoxic to p53-overexpressing prostate cancer cells. In addition, rAd-p53 infection can induce overexpression of p53 and thus the cytotoxicity of CTLs differentiated by the p53-DC vaccine in p53 non-expressing prostate cancer cells. These findings suggest that this combination therapy using p53-DC vaccine and rAd-p53 gene therapy together may represent a new paradigm for the treatment of mCRPC.