Distinct immunoreactions after microwave ablation of primary tumor with different heating parameters in VX2 tumor model

Abstract

AbstractBackground Thermal ablations of solid tumors in situ can activate the immune system and produce a specific immune response against tumor. Microwave ablation (MWA) with different parameters can ablate tumors with similar sizes and cause different local inflammatory effects. Our aim was to determine whether MWA of primary tumor in different energy modes can induce different immunological effects. Methods Seventy rabbits with VX2 tumors implanted subcutaneously underneath the right second nipple were treated with high-power MWA (40W×1 minute), low-power MWA (20W×2 minutes), surgical resection, or left without treatment as control. Survival time was evaluated by log-rank test. On day 14 after ablation, immunohistochemistry and flow cytometry were used to evaluate the T-cell immune responses. Besides, the cytokine patterns were also identified from enzyme-linked immunosorbent assay. Results Tumor eradication was achieved completely in MWA groups as proven by nicotinamide adenine dinucleotide diapforase (NADH-diaphorase) staining. The rabbits in the control group showed significantly more pulmonary metastases and poorer survival than the three treatment groups; however, no significant difference was observed among three treatment groups. MWA groups induced more intratumoral and systemic CD4+and CD8+T cells than the control group. MWA caused more systemic CD4+T cells than operation. High-power MWA induced more intratumoral CD4+and CD8+T cells and systemic CD4+T cells than low-power MWA. MWA induced increased levels of IL-2, IL-12 and decreased levels of IL-4, IL-6, IL-10 compared with control group. Importantly, a significant higher level of serum IL-12 was found in high-power MWA than that in low-power MWA group. Conclusions High-power MWA induced enhanced Th1-type immune response in comparison to low-power MWA. High-power MWA may be selected for the treatment of solid tumors, although future studies are still needed to confirm our results.