Proteomic analysis reveals important role of 14‐3‐3σ in anoikis resistance of cholangiocarcinoma cells

Cholangiocarcinoma (CCA), a high‐prevalence cancer in Thailand, is highly metastatic and has high mortality rates. Anoikis resistance or the ability of cells to survive after detachment from extracellular matrix is a necessary property of metastatic cancer. Here, we report differential protein expression of an anoikis‐resistant CCA cell line culture, under attachment conditions compared to nonattachment conditions, studied using 2DE coupled with protein identification by LC‐MS/MS. Our data reveal the deregulation of proteins involved in stress response, cytoskeleton rearrangement, proapoptosis, cell proliferation, and glycolysis. Interestingly, 14‐3‐3σ (14‐3‐3 sigma) protein was intensely upregulated in detached CCA cells. Real‐time RT‐PCR analysis confirmed that only the sigma isotype was the most abundant transcript among 14‐3‐3 genes in CCA cells. Furthermore, silencing 14‐3‐3σ expression by small interfering RNA in CCA cells resulted in significantly increased percentage of cell death in detached culture. Our findings provide the first evidence showing that 14‐3‐3σ protein plays a crucial role in anoikis resistance of CCA cells. Therefore, 14‐3‐3σ might be a potential target in CCA therapy.