[Experimental study of anti-tumor immunologic response induced by cryoablation for prostate cancer].

ABSTRACT

OBJECTIVE: To assess the anti-tumor immune response of cryoablation for prostate cancer. METHODS: Mouse model of prostate cancer was established. And the tumor-bearing mice were divided into three groups control group (Group A), surgery group (Group B) and cryoablation group (Group C). Blood samples were withdrawn before and at Days 7, 14, 21 post-treatment. IFN-gamma and IL-4 were analyzed by enzyme-linked immunosorbent assay (ELISA). Th1/Th2 ratio was estimated from the IFN-gamma/IL-4 ratio. Lymphocytes of draining lymph node (DLN) and spleen were isolated. And the post-therapeutical number of tumor-specific IFN-gamma+CD4+ Th cells was measured by the method of enzyme link immunological spot (ELISPOT). And tumor-specific cytolytic activity of CD8+ cytotoxic T lymphocyte (CTL) was measured by LDH assay. The rate of metastasis was assessed. RESULTS: At Day 7 post-treatment in Groups A, B and C, Th1/Th2 ratio was 4.97+/-0.31, 10.07+/-0.62 and 13.71+/-0.57 respectively (P<0.05); the number of IFN-gamma+ cells every 10(6) CD4+ Th cells in DLN 22.3+/-1.0, 24.0+/-1.2 and 243.4+/-46.2 respectively; cytolytic activity of cytotoxic T lymphocyte against prostate cancer cells (14.6+/-1.1)%, (15.2+/-0.8)% and (62.6+/-2.3)% respectively (P<0.05). But for T cells derived from spleen, there were no difference in IFN-gamma+CD4+ Th cells or cytolytic activity of CTL among the groups. At Day 28 post-treatment, the rate of DLN metastasis was 100%, 80% and 40% respectively. And the rates of lung metastasis were all 100%. CONCLUSION: Cryoablation for prostate cancer can induce the Th1 advantage of anti-tumor immunity and generate the tumor-specific immune response in DLN. But the response remains limited. Further studies are warranted.