Objective: To assess the changes about numbers and immune functions of splenic DC (dendritic cell) after a combined therapy of cryoablation and GM-CSF (granulocyte macrophage-colony stimulating factor) for prostate cancer.
Methods: Murine model of prostate cancer was established. And the tumor-bearing mice were divided into 4 groups: control group (Group A), GM-CSF treatment (Group B), cryoablation treatment (Group C) and a combined therapy of cryoablation and GM-CSF (Group D). Spleens were sampled before and 7, 14, 21 days after treatment. Immunohistochemistry of DC was performed. And splenic lymphocytes were isolated and their activated percents analyzed by flow cytometry. The tumor-specific cytolytic activity of cytotoxic T lymphocyte (CTL) was measured by LDH (lactate dehydrogenase) assay. And the lung metastasis rates were calculated.
Results: At Day 7 post-treatment, the number of DC per high-power field was 26.4 ± 1.1, 36.6 ± 2.1, 25.8 ± 1.3 and 58.2 ± 1.9 (P < 0.05); the activated percent of DC 13.60% ± 1.67%, 9.50% ± 0.21%, 14.40% ± 1.14% and 32.80% ± 2.39% (P < 0.05); cytolytic activity of CTL against prostate cancer cells 7.76% ± 0.11%, 8.10% ± 0.92%, 9.38% ± 0.45% and 41.68% ± 0.82% in Groups A, B and C respectively (P < 0.05). At Day 21 post-treatment, the rate of lung metastasis was 5/5, 4/5, 4/5 and 1/5 respectively.
Conclusion: A combined therapy of cryoablation and GM-CSF may increase the number and activated percent of DC in spleen, enhance the tumor-specific immune responses and decrease lung metastasis rate.