PBA2, a novel compound, enhances radiosensitivity in various carcinoma cells by activating the p53 pathway in vitro...

Radiotherapy is the main method used to treat human carcinoma; however, certain types of carcinomas are radiation-insensitive. The present study aimed to explore whether a novel compound, PBA2, could enhance the radiosensitivity of various carcinoma cells in vitro and in vivo, and investigate its underlying mechanism. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to assess the cytotoxicity of PBA2. Colony formation assays were used to observe the radiosensitivity effect of PBA2 in vitro. Cell cycle distributions and cell apoptosis were estimated using flow cytometry. Comet assays and Immunofluorescence assays were used to analyze DNA damage. The intracellular RNA was extracted and analyzed by sequencing. Western blotting was used to determine protein levels. A stable cell line with TP53 (encoding p53) knockdown was constructed by cell transfection. A mouse xenograft model was used to assess the radiosensitivity effect of PBA2 in vivo. We found that PBA2 at a low concentration (0.1 μM) enhanced radiosensitivity in various carcinoma cells, including CNE1, MG63, KB, HEP2, GLC82, and SMMC7221, in vitro. Combined with PBA2, radiation induced significant cell apoptosis in CNE1 and MG63 cells, accompanied by increased DNA damage, but did not affect cell cycle arrest. Mechanistically, PBA2 promoted p53 expression significantly; however, when p53 was mutated, functionally impaired, or knocked down, PBA2 could not enhance the radiosensitivity of these cells. Additionally, the combination of PBA2 and radiation reduced the tumor volume and tumor weight in CNE1 xenograft models significantly, without obvious toxicities. Our results demonstrated that PBA2 enhanced the radiosensitivity of various carcinoma cells in vitro and in vivo. The underlying mechanism might involve increasing DNA damage and cell apoptosis via activating the p53 pathway.