Non-small-cell lung cancer (NSCLC) is one of the leading causes of cancer-related death worldwide. Although epigenetic deregulation is known to be important for tumor progression, the molecular mechanisms in NSCLC remain unclear. Here, we found that G9A (known as EHMT2), a histone methyltransferase responsible for mono- or di-methylation of histone 3 (H3) lysine 9 (K9), is significantly upregulated in NSCLC. Knocking down G9A or pharmacological inhibition of its activity suppressed tumor cell growth, colony formation, invasion and migration. Furthermore, G9A exerts these functions by repressing CASP1 expression. Knocking down CASP1 in G9A-deficient cell restored capacities of tumor cell invasion and migration. Mechanistically, G9A silences the CASP1 promoter activity by increasing H3K9me2 around its promoter. Finally, high expression of G9A or low expression of CASP1 is correlated with poor overall survival in lung adenocarcinoma. Overall, our study uncovers a novel mechanism of G9A promoting tumor cell growth and invasion by silencing CASP1, and implies that G9A may serve as a therapeutic target in treating NSCLC.

Epigenetic regulation plays an important role in tumor metastasis. KDM1A is a histone demethylase specific for H3K4me2/me1 demethylation, and has been found to be overexpressed in many cancers, including non-small cell lung cancer (NSCLC). However, the role of KDM1A in lung cancer remains unclear. Here, we show that KDM1A promotes cancer metastasis in NSCLC cells by repressing TIMP3 (tissue inhibitor of metalloproteinase 3) expression. Consistently with this, overexpression of TIMP3 inhibited MMP2 expression and JNK phosphorylation, both of which are known to be important for cell invasion and migration. Importantly, knockdown of TIMP3 in KDM1A-deficient cells rescued the metastatic capability of NSCLC cells. These findings were also confirmed by pharmacological inhibition assays. We further demonstrate that KDM1A removes H3K4me2 at the promoter of TIMP3, thus repressing the transcription of TIMP3. Finally, high expression of KDM1A and low expression of TIMP3 significantly correlate with a poor prognosis in NSCLC patients. This study establishes a mechanism by which KDM1A promotes cancer metastasis in NSCLC cells, and we suggest that KDM1A may be a potential therapeutic target for NSCLC treatment.