DHFR and lung carcinoma: The anticancer activity tested in colon and lung cancer cells suggests the effectiveness of drug-conjugated AuNPs, enhancing the therapeutic effect by inducing apoptosis and decreasing the effective doses by half of MTX in the colon cancer cell line, with folate receptor, confirming the MTX mechanism of internalization, linking to dihydrofolate reductase (DHFR) and interrupting the folic acid cycle, which is usually overexpressed in cancer cells.