One of the most commonly used cytotoxic chemotherapeutic agents for the treatment of non-small cell lung carcinoma (NSCLC) and mesothelioma is pemetrexed, an antifolate that inhibits three enzymes used in purine and pyrimidine synthesis, thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), consequently suppressing DNA and RNA synthesis4,5. The gene discussed is GART; the disease is non-small cell lung carcinoma.