Taku Kato

Perforin secreted from cytotoxic lymphocytes plays a critical role in cancer immunosurveillance. The aim of this study was to investigate the therapeutic potential of liposomes containing perforin expression vector driven by the promotor of prostate-specific antigen (PSA). The anti-tumor effect of perforin was analyzed using prostate cancer (PC) PC-3 cells in which perforin expression was controlled by Tet-on system (PC-3PRF cells). Liposomes encapsulating PSA promoter-driven perforin expression vector (pLipo) were constructed for its specific expression in PC. The anti-tumor effect of pLipo was evaluated in vitro using docetaxel-resistant PC 22Rv1 PC cell line, 22Rv1DR, and PC-3 cells in the presence of human peripheral blood mono nuclear cells (PBMCs) and also in vivo using male nude mice bearing 22Rv1DR cell-derived tumor xenograft. Induction of perforin significantly inhibited growth of PC-3PRF cells. Treatment with pLipo induced perforin expression in 22Rv1DR cells expressing PSA but not in PC-3 cells lacking it. Treatment with pLipo at a low concentration was prone to inhibit growth of both cell lines and significantly inhibited growth of 22Rv1DR cells when co-incubated with PBMCs. The combined use of pLipo at a high concentration with PBMCs showed nearly complete inhibition of 22Rv1DR cell growth. Intravenous administration of pLipo via tail vein increased the level of perforin in tumor and serum and significantly decreased the tumor volume. Our results suggest that liposome-mediated PC-specific expression of perforin could be a novel therapy for advanced PC.

BACKGROUND/AIM: De-differentiation is a key step for the progression of cancer cells. This study investigated the anti-tumor effect of kartogenin (KGN), which has the ability to differentiate cells, on prostate cancer (PC) cells. MATERIALS AND METHODS: The effects of KGN on androgen receptor (AR) nuclear localization, prostate-specific antigen (PSA) expression, and Smad2 activation as well as the growth of PC cell lines (LNCaP, 22Rv1 and PC-3) were analyzed. RESULTS: KGN significantly inhibited growth of AR-expressing LNCaP and 22Rv1 cells but not of AR-lacking PC-3 cells. KGN decreased AR nuclear localization and PSA expression, but did not enhance the anti-tumor effect of bicalutamide in LNCaP cells. KGN activated Smad2 both in the absence and presence of TGF-β1. KGN also inhibited growth of docetaxel-resistant PC cells, 22Rv1DR, and re-sensitized them to the agent. CONCLUSION: KGN has a potential as a novel therapeutic for PC patients after treatment failure.