第二型轉麩胺酶在肺癌細胞中的角色

文獻指出許多癌細胞的transglutaminase 2 (TG2)表達量高，且TG2是最廣泛、多樣化的TG酵素家族成員，與許多細胞功能有關。而103年國人十大死因當中以氣管、支氣管和肺癌為首位，因此想探討TG2在A549和H1299肺癌細胞中對藥物感受性、細胞轉移和細胞存活的角色。以即時聚合酶鏈鎖反應、酵素連結免疫分析和西方墨點法比較肺癌細胞株的TG2表現量，轉染siTG2 RNA來分析A549及H1299細胞的細胞存活相關機制。在A549、H1299、H1355和H460的TG2表達量以A549細胞最高。A549細胞以RNA 干擾技術抑制TG2會造成細胞群落形成能力降低；以流式細胞儀分析，降低了TG2表達會造成細胞凋亡以及細胞自噬比例上升，其中，自噬作用可能與AKT路徑相關。另外，轉染siTG2 RNA至H1299細胞，以西方墨點法分析細胞凋亡及細胞自噬作用，結果顯示，抑制TG2表現持續48至72小時，細胞凋亡標記蛋白c-PARP及自噬作用標記蛋白LC3A-Ⅱ上升，然而，不同於A549細胞的是其下游蛋白p-AKT，並未看到變化。由數據顯示，TG2在A549細胞可能扮演著保護癌細胞的作用，未來，需更進一步探討自噬作用和細胞凋亡的重要性以及相互關係，才能釐清TG2在肺癌細胞中的角色。

Previously studies have shown that high expression levels of transglutaminase 2 (TG2) were detected in several types of cancers. Moreover, the most universal and diverse member of the TG family is the TG2, a multifunctional protein. Since the leading cause of deaths in Taiwan (2014) were trachea, bronchus and lung cancers, we aim to investigate the role of TG2 in lung cancer cell lines (A549 and H1299 cells) to uncover its significance. The expression of TG2 in lung cancer cell lines was detected by real-time PCR, ELISA and western blotting. Down-regulation of TG2 in A549 and H1299 cells were achieved by transfecting cells with siNC or siTG2 RNA, and its effect on cell survival was evaluated. Our results showed that A549 cell has the highest expression level of TG2 as compared with H1299, H1355 and H460 cells. Inhibition of TG2 in A549 by RNA interference reduced colony formation and induced apoptosis and autophagy. Regulation of autophagy may be related to the AKT pathway. In addition, down-regulation of TG2 for 48 h and 72 h by siRNA in H1299 cell showed increased expression of the apoptosis marker, c-PARP and the autophagy marker, LC3A-Ⅱ by western blotting. Interestingly, H1299 cell transfected with siTG2 RNA failed to reduce levels of p-AKT. These results suggest that TG2 may play a protective role in A549 cell. In order to clarify the role of TG2 in lung cancer cell lines, the relationship between autophagy and apoptosis need to be further investigated in the future.