Low Frequency Magnetic Fields Enhance Antitumor Immune Response against Mouse H22 Hepatocellular Carcinoma

OBJECTIVE Many studies have shown that magnetic fields (MF) inhibit tumor growth and influence the function of immune system. However, the effect of MF on mechanism of immunological function in tumor-bearing mice is still unclear. METHODS In this study, tumor-bearing mice were prepared by subcutaneously inoculating Balb/c mice with hepatocarcinoma cell line H22. The mice were then exposed to a low frequency MF (0.4 T, 7.5 Hz) for 30 days. Survival rate, tumor growth and the innate and adaptive immune parameters were measured. RESULTS MF treatment could prolong survival time (n = 28, p<0.05) and inhibit tumor growth (n = 9, p<0.01) in tumor-bearing mice. Moreover, this MF suppressed tumor-induced production of cytokines including interleukin-6 (IL-6), granulocyte colony- stimulating factor (G-CSF) and keratinocyte-derived chemokine (KC) (n = 9-10, p<0.05 or 0.01). Furthermore, MF exposure was associated with activation of macrophages and dendritic cells, enhanced profiles of CD4(+) T and CD8(+) T lymphocytes, the balance of Th17/Treg and reduced inhibitory function of Treg cells (n = 9-10, p<0.05 or 0.01) in the mice model. CONCLUSION The inhibitory effect of MF on tumor growth was related to the improvement of immune function in the tumor-bearing mice.