OBJECTIVETo explore the effects of radiofrequency ablation(RFA) on immune system and lung metastasis in a mouse model of triple negative breast cancer 4T1.

METHODSMouse breast cancer 4T1 cells were injected into the right hind limb of female Bal B/c mice. When the tumor size was 6-8 mm in diameter, RFA was used to treat the transplanted breast cancer in mice. We examined the splenic lymphocyte subsets by flow cytometry at different time points after RFA. Fourteen days after treatment, we sacrificed the mice of both control and treatment groups, counted the number of lung metastatic nodules, and detected the changes of splenic lymphocyte subsets by flow cytometry.

RESULTSRFA basically eliminated the orthotopic carcinoma with a low local recurrence rate. After the RFA treatment, the amount of spleic CD4⁺ T cells, CD8⁺ T cells, B cells, NK and NKT cells was increased. Fourteen days after the RFA treatment, all mice were sacrificed, and the lung metastatic nodules were 24 ± 18 in the control group and 81 ± 35 in the RFA-treated group (P = 0.012). The mechanism of suppression of metastatic lung cancers was related to the increase of splenic CD4⁺ T cells, CD8⁺ T cells, B cells and NK cells, and the decrease of myeloid-derived suppressor cells.

CONCLUSIONSRFA can enhance the anti-tumor immunity and effectively inhibit lung metastasis of 4T1 cell-induced breast cancer, and has a good potential effect in the treatment of triple-negative breast cancer and the control of distant metastasis.