Effect of millimeter wave radiation on the expression of proliferating cell nuclear antigen, CDK4 and P16 in rat hepatocellular carcinoma

Abstract

OBJECTIVE: To study the effects of millimeter wave (MMW) radiation on rat hepatocellular carcinoma.METHODS: Forty male Wistar rats were randomly divided into four groups, and the liver region of the rats was directly radiated by MMW (35.8 GHz, 100 mW/cm2) for 20 min twice per week. Rats in groups 1 to 3 were fed with diethlnitrosamine (DEN). Group 1 was a tumor control group with sham radiation. Group 2 was given radiation for 10 weeks starting from week 5 and group 3 was radiated for 5 weeks starting from week 10. Group 4 was a normal control group radiated for 5 weeks and given distilled water. At week 14, all rats were sacrificed. A serological test for γ‐glutamyltransferase (γ‐GT) and immunohistochemical staining of proliferating cell nuclear antigen (PCNA), CDK4 and P16 in liver tissue were performed.RESULTS: The serum level of γ‐GT in group 1 (18.44 ± 4.88 U/L) was higher than that in group 2 (13.75 ± 2.41 U/L, P < 0.05), and the level of γ‐GT in group 3 (16.43 ± 2.12 U/L) was lower than that in group 1, but the difference was not significant. Based on histological examination of the livers, adenocarcinoma only developed in group 1. In the other DEN‐induced tumor groups, only eosinophilic and basophilic nodules were formed in the liver; no carcinoma cells were found. Expression of proliferating cell nuclear antigen (PCNA) and CDK4 staining in liver tissue in groups 2 and 3 were significantly lower than those in group 1, but the expression of P16 in the former was higher than that in the latter.CONCLUSIONS: Millimeter wave radiation partially inhibits cell proliferation and suppresses DEN‐induced hepatocellular carcinoma in rats.