DHFR and non-small cell lung carcinoma: The analysis of the expression of dihydrofolate reductase (DHFR) and glycinamide ribonucleotide formyl-transferase (GARFT) genes in NSCLC cells after the treatment with SFRE indicated the downregulation of both genes (Figure 8B), which may explain, at least partially, the observed synergism between SFRE and pemetrexed in the inhibition of cell proliferation.