MTHFR and squamous cell carcinoma: In LUAD and squamous cell carcinomas, the frequency of p16, MGMT, RASSF1, death‐associated protein kinase (DAPK), methylenetetrahydrofolate reductase (MTHFR), adenomatous polyposis coli (ACP), glutathione S‐transferase pi gene (GSTP1), Cadherin 1 (CDH1), and PTEN promoter methylation was significantly higher among smokers than never‐smokers.84, 85