Purpose: Lung adenocarcinoma is one of the common causes of cancer-related deaths worldwide. AHNAKs  are giant proteins, which are correlated with cell structure and migration, cardiac calcium channel signaling, and other processes. Current studies identified AHNAK2  as a novel oncogene in some cancers; however, studies on its function in lung cancers are limited.
Materials and Methods: The expression of AHNAK2  was analyzed in normal lung tissues, lung adenocarcinoma tissues, and paracancerous tissues using the Oncomine database. It was further verified in relative cell lines by real-time quantitative polymerase chain reaction and Western blotting (WB). Adenocarcinoma cell lines were transfected with si-NC and si-AHNAK2  by lipofectamine 3000 and treated with or without TGF-β 1, and cell migration and invasion were detected by wound-healing and transwell assays. The expression of epithelial-mesenchymal transition (EMT) markers was detected by WB, as well as that of phosphorylated-Smad3 (p-Smad3) and Smad3 levels. After Smad3 phosphorylation inhibitor was added to the adenocarcinoma cell lines, migration and invasion were detected by wound-healing and transwell assays, and the expression of EMT markers was detected by WB when the cells were transfected with si-NC and si-AHNAK2  and treated with or without TGF-β 1.
Results: We found higher expression of AHNAK2  in lung adenocarcinoma tissues through the Oncomine database and further verified its high expression in relative cell lines. When the cells were stimulated with TGF-β 1, knockdown of AHNAK2  suppressed cell migration, invasion, and EMT, and inhibited TGF-β–induced Smad3 signaling. When p-Smad3 was inhibited, knockdown of AHNAK2  had no effect on the two cell lines investigated when treated with or without TGF-β 1.
Conclusion: AHNAK2  acts as an oncogenic protein and promotes migration, invasion, and EMT in lung adenocarcinoma cells via the TGF-β/Smad3 pathway. Thus, it may be a novel target for lung adenocarcinoma therapy.
Keywords: epithelial-mesenchymal transition, lung adenocarcinoma, AHNAK2 , transforming growth factor-beta 1, Smad