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

To assess the anti-tumor immune response of cryoablation for prostate cancer.

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 Blood samples were withdrawn before and at Days 7, 14, 21 post-treatment.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.

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%.

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.