Methylation of kruppel-like factor 2 (KLF2) associates with its expression and non-small cell lung cancer progression

Kruppel-like factor 2 (KLF2) is a putative tumor suppressor gene. This study investigated its role and epigenetic mechanisms in human non-small cell lung cancer (NSCLC) in ex vivo and in vitro. A total of 47 paired NSCLC and normal tissues and six cell lines were analyzed using qRT-PCR for KLF2 expression. KLF2 methylation was assessed using the methylation specific PCR (MSP) or bisulfite sequencing PCR (BSP). Functional KLF2 region 4 (+567 to +906) was confirmed using the dual-luciferase reporter assay, while CCK-8 cell viability and flow cytometric assays were used to assess changes in cell viability, cell cycle distribution, and apoptosis after knockdown or re-expression of KLF2. Western blot was performed to analyze the effects of KLF2 shRNA on knockdown of KLF2 expression and p15 and p21 expression in cells. We found that KLF2 expression was significantly reduced in NSCLC cells and tissues via KLF2 methylation. Reduction of KLF2 expression was associated with KLF2 region 4 hypermethylation in 27 of 47 (57.45%) NSCLC tissues. Furthermore, methylation at KLF2 region 4 was significantly associated with lymph node metastasis and advanced TNM stage. Re-expression of KLF2 suppressed NSCLC cell viability, arrested cells at G0/G1 cell cycle by induction of p15 and p21 expression, and promoted apoptosis, whereas knockdown of KLF2 expression had the opposite effects on cells. Taken together, KLF2 possesses tumor suppressor functions in NSCLC and detection of KLF2 methylation should be further evaluated as a tumor or prognostic biomarker for NSCLC.