[Establishment and Preliminary Analysis of Lung Cancer Cell Line A549 with Stable 4 4 Knockdown].

Objective: To analyze the effect of knocking down 4 4 expression on the proliferation and migration of cancer cells, and to explore its underlining molecular mechanisms.

Methods: A stable knockdown 4 4 cell line was constructed and the subcellular localization of the cells was determined with immunofluorescence, cell proliferation assay and cell migration assay. In addition, the effects of down-regulated 4 4 expression were analyzed by examining the difference between the proliferation and migration of cancer cells in the knockdown group and those of the control group.

Results: 4 4 was localized in focal adhesion and cell edges in A549 cells. Stable knockdown of 4 4 expression induced cancer cells to grow in clusters and arrested the progression of the cell cycle and cell migration. Further analysis found that knocking down 4 4 expression in A549 cells induced the accumulation of epithelial cell marker E-cadherin, and subsequently, the down-regulation of N-cadherin, a mesenchymal cell marker, thereby disrupting the "cadherin switch" and the epithelial-mesenchymal conversion. Then, the control group and the knockdown group both received the combined treatment of cisplatin at a final concentration of 5 μmol/L and paclitaxel at a final concentration of 20 nmol/L. The stably knocked down 4 4 expressing cells showed significantly enhanced toxicity of chemotherapeutic drugs to cancer cells.

Conclusion: The study shows that 4 4 regulates the malignant phenotypes of cancer cells and chemoresistance by regulating "cadherin switch" to promote epithelial-mesenchymal transition in A549 cells.