ABSTRACT
Objective To investigate the impacts of pyruvate kinase M2 isoform (PKM2) silencing on the radiosensitivity of lung adenocarcinoma cell line (A549 cells) and the radiation synergy of xenografts, and to explore their mechanisms. Methods Plasmid pshRNA?PKM2 for interference with PKM2 expression was transfected into A549 cells, and empty vector?transfected cells and untransfected cells were set as con?trols. The silencing efficiency of pshRNA?PKM2 and the expression level of microtubule?associated protein 1 light chain 3(LC3) were measured by Western blot assay. The radiosensitizing effects in A549 cells and xen?ografts after PKM2 silencing were determined by colony?forming assay and xenografts growth curves. Autoph?agy formation in A549 cells and xenografts was analyzed by transmission electron microscopy, and the ex?pression level of PKM2 in xenografts was measured by immunohistochemistry. Comparison between groups was made by Student′s t?test, and the body weights of nude mice and xenograft volumes were subjected to a?nalysis of variance for continuous variables. Results Stable A549 cell lines transfected with pshRNA?PKM2 were successfully produced. Transfection with pshRNA?PKM2 significantly down?regulated PKM2 expression in A549 cells and xenografts (P= 0?? 001;P= 0?? 000). The sensitizer enhancement ratios for A549 cells and xenografts were 1?? 47 and 2?? 00, respectively. Interference with PKM2 expression enhanced radiation?in duced autophagy formation and significantly increased the ratio of LC 3 ? II / I ( P= 0.000 1 ) . Conclusions Silencing of PKM2 expression may enhance the radiosensitivity of A549 cells and xenografts by regulation of autophagy, which holds promise for becoming an effective radiosensitizing target for non?small cell lung canc?er, but still needs to be confirmed by further studies.
ABSTRACT
Objective:To investigate the effects and underlying mechanisms of XRCC3 on esophageal squamous-cell carcinoma (ESCC) radiotherapy response. Methods:Expression levels of XRCC3 were detected by reverse transcription PCR, Western blot, and immunohistochemistry. We knocked down XRCC3 with lentiviral infection in ESCC cells. Cell apoptosis was examined by flow cytom-etry. DNA damage and telomere dysfunction-induced foci were determined by immunofluorescence. Results:The expression levels of XRCC3 in ESCC cells and tissues were higher than those in normal esophageal epithelial cells and corresponding adjacent noncancer-ous esophageal tissues. Knockdown of XRCC3 in ESCC cells substantially increased the therapeutic efficacy of radiation. We demon-strated that the radiation resistance of XRCC3 was attributed to the XRCC3-maintaining telomere stability, which reduced ESCC cell death through radiation-induced apoptosis. Conclusion: Our data suggested that XRCC3 protects ESCC cells from ionizing radia-tion-induced DNA damage and death by enhancing telomere stability. Thus, XRCC3 can be used as a promising therapeutic target for ESCCs.