Apoptosis and injuries of heavy ion beam and x-ray radiation on malignant melanoma cell.

This study aims to investigate the influence of high linear energy transfer (LET) heavy ion (12C6+) and low LET X-ray radiation on apoptosis and related proteins of malignant melanoma on tumor-bearing mice under the same physical dosage. C57BL/6 J mice were burdened by tumors and randomized into three groups. These mice received heavy ion (12C6+) and X-ray radiation under the same physical dosage, respectively; their weight and tumor volumes were measured every three days post-radiation. After 30 days, these mice were sacrificed. Then, median survival time was calculated and tumors on mice were proliferated. In addition, immunohistochemistry was carried out for apoptosis-related proteins to reflect the expression level. After tumor-bearing mice were radiated to heavy ion, median survival time improved and tumor volume significantly decreased in conjunction with the upregulated expression of pro-apoptosis factors, Bax and cytochrome C, and the downregulated expression of apoptosis-profilin (Bcl-2, Survivin) and proliferation-related proteins (proliferating cell nuclear antigen). The results indicated that radiation can promote the apoptosis of malignant melanoma cells and inhibit their proliferation. This case was more suitable for heavy ion (12C6+). High LET heavy ion (12C6+) radiation could significantly improve the killing ability for malignant melanoma cells by inducing apoptosis in tumor cells and inhibiting their proliferation. These results demonstrated that heavy ion (12C6+) presented special advantages in terms of treating malignant melanoma. Impact statement Malignant melanoma is a malignant skin tumor derived from melanin cells, which has a high malignant degree and high fatality rate. In this study, proliferating cell nuclear antigen (PCNA) can induce the apoptosis of malignant melanoma cells and inhibit its proliferation, and its induction effect on apoptosis is significantly higher than low LET X-ray; hence, it is expected to overcome its lower sensitivity to radiation. This study can provide theoretical basis for clinical trials, in which malignant melanoma is treated by heavy ion (12C6+), in order to accurately determine the clinical efficacy of heavy ion therapy. Clinical applications has revealed that local tumor control rate is high when heavy ion is used to treat malignant melanoma, indicating that heavy ion is an important direction in treating melanoma in the future.