| Summary: | 碩士 === 國立成功大學 === 環境醫學研究所 === 98 === Prostate cancer is a leading cause of illness and death among men in the United States and Western Europe. In recent years, the morbidity of prostate cancer in other Asian countries has been also steadily rising. Radiotherapy is one of the treatment for prostate cancer. Many studies indicated that arsenic trioxide (ATO) could enhance the anti-tumor effect of radiotherapy and reduce radiation dosage. The aim of this study was to investigate the anticancer effect of ionizing radiation (IR) combined with arsenic trioxide (ATO) and their underlying mechanisms on prostate cancer LNCaP (wild-type p53) and PC-3 (p53 null) cells. In in vitro study, cell viability was detected by trypan blue. Cell cycle distribution and early apoptosis with annexin V-FITC apoptosis detection kit were analyzed by flow cytometry. In order to observe the expression of acidic vesicular organelle which is characteristic of autophagy, cells were stained with acridine orange. Ultrastructure of PC-3 cells was analyzed by electron microscopy. Western blotting was used to determine apoptosis- and autophagy-associated proteins expression. A nude mice xenograft model was used to investigate the effects of IR combined ATO treatment in vivo. The results indicated that the effect of combined treatment is more significant than IR or ATO alone in LNCaP and PC-3 cells. The combined treatment increased the percentage of apoptosis in LNCaP cells, but did not increase the percentage of apoptosis in PC-3 cells. On the contrary, combined treatment caused cell cycle G2/M arrest in PC-3 cells and increased the percentage of autophagy in both LNCaP and PC-3 cells compared to ATO and IR alone. Furthermore, the expression of LC3Ⅱ and P62/SQSTM1 increased in LNCaP and PC-3 cells treated with combined treatment. The Akt/mTOR pathway was inhibited by combined treatment compared with those subjected to individual treatment. In addition, pretreated with 3-MA, a specific inhibitor of autophagy, decreased the combination-induced autophagy and increased cell viability. Whereas pretreated with LY294002, a specific inhibitor of PI3K/Akt, further enhanced the combination-induced autophagy and decreased cell viability. In in vivo studies, the combination of IR and ATO significantly reduced the tumor volume in nude mice that had received a subcutaneous injection of PC-3 cells. Moreover, the expression of LC3Ⅱand Atg5-Atg12 increased in PC-3 xenograft tumor treated with IR combined with ATO. These results show that combined treatment may increase therapeutic efficacy of prostate cancer cell lines. Moreover, combined treatment induced autophagic cell death through inhibition of Akt/mTOR signaling pathway in LNCaP and PC-3 cells.
|
|---|
