MTHFR and lung cancer: Here, we report the impact of polymorphic variation within the folate metabolism pathway genes MTHFR, methionine synthase (MTR), methionine synthase reductase (MTRR), DNA methyltransferase (DNMT2), methylenetetrahydrofolate dehydrogenase (MTHFD1) and methenyltetrahydrofolate synthetase (MTHFS) on lung cancer prognosis in 619 patients.