Background: Recently, pemetrexed (PEM), a new generation antifolate, has been used for the treatment of patients with advanced non-squamous cell carcinoma (SQ) of non-small cell lung cancer (NSCLC) and malignant pleural mesothelioma (MPM). However, no useful markers for selecting appropriate candidates exist at present.
Materials and methods: Tumor specimens were collected from 5 lung non-SQ and 8 MPM patients who underwent surgery and received PEM. Real-time PCR and immunohistochemical (IHC) staining of the primary tumor were used to analyze the mRNA and protein expressions of thymidylate synthase (TS)/dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT), and to compare the expression status and clinical outcomes.
Results: TS, DHFR, and GARFT mRNA levels had a median value of 2.39, 1.70, and 1.40 in non-SQ samples of NSCLC patients. The TS and DHFR protein levels had a mean total score of 2 and 4 in non-SQ of NSCLC patients. TS, DHFR, and GARFT mRNA levels had a median value of 5.55, 3.73, and 3.52 in MPM patients. TS and DHFR protein levels had a mean total expression score of 1 and 3 in MPM patients. No significant correlation was identified between the expression levels of TS/DPD/GARFT mRNA and clinical response for the non-SQ of NSCLC and MPM patients treated with PEM.
Conclusion: TS, DHFR, and GARFT mRNA and protein expression may not be useful markers for predicting clinical response in Japanese patients with non-SQ of NSCLC and MPM. Further investigations are necessary in order to develop biomarkers to determine the clinical benefits of PEM treatment.