Biological effects of nonthermal plasma combined with X-ray irradiation on human hepatocellular carcinoma in nude mice

Abstract

Objective To investigate the biological effects of nonthermal plasma (NTP) combined with X-ray irradiation on human hepatocellular carcinoma in nude mice. Methods By subcutaneous inoculation, tumor models of human hepatocellular carcinoma HepG2 in nude mice were established, and these mice were divided into control group, NTP treatment group, X-ray irradiation group, combined treatment group. The changes of tumor microenvironment were observed using hematoxylin-eosin (HE) staining. The terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) was used to determine the level of neuronal apoptosis in tumor tissues. The expression of metal matrix proteinase-2 (MMP-2) was detected by immunohistochemical assay. Transmission electron microscope was used to observe cell structure changes. Results The final tumor volumes of control group, NTP treatment group, X-ray irradiation group, combined treatment group were (543.96±108.45), (436.54±65.49), (351.66±56.68), (281.97±35.60)mm3, with a statistically significant difference (F=9.63, P=0.01), and the difference between X-ray radiation group and the combination treatment group was significant (P=0.05). HE staining showed that there was a larger area of necrosis in the combined treatment group compared with the other groups. TUNEL showed that the apoptotic indexes were (0.95±0.13)%, (5.82±0.26)%, (7.53±0.43)%, (11.07±0.35)% respectively, with a statistically significant difference (F=547.76, P=0.00), and the difference between X-ray radiation group and the combination treatment group was statistically significant (P=0.00). The immune scores of each group were 12, 9, 9, 2. Electron microscopic observation showed that there were more apoptotic bodies in the combined treatment group than those in the other groups, accompanied by mitochondrial edema. Conclusion NTP and X-ray irradiation therapy in the treatment of human hepatocellular carcinoma in nude mice model has a synergistic effect. Probably, it can be a new type of treatment in curing cancers. Key words: Radiotherapy; Liver neoplasms; Nonthermal plasma