O⁶-methyl-guanine-DNA methyltransferase methylation and IDH1/2 mutation in small cell lung cancer

Small cell lung cancer (SCLC) is sensitive to first-line chemotherapy and radiotherapy, but frequently recurs. Temozolomide is a chemotherapeutic drug suitable for the treatment of relapsed SCLC, particularly when brain metastases are present. The response of SCLC to temozolomide may be associated with the methylation status of O⁶-methyl-guanine-DNA methyltransferase (MGMT). Isocitrate dehydrogenase (IDH) mutation is an independent prognostic factor of good outcome in gliomas and appears to be a significant marker of positive chemosensitivity in secondary glioblastoma. In order to identify the status of MGMT promoter methylation and IDH1/2 mutation of SCLC in China, 33 SCLC specimens from patients that underwent surgery were retrospectively collected in Zhejiang Cancer Hospital (Hangzhou, China) between 2008 and 2014. High-resolution melting analysis and methylation-specific polymerase chain reaction were used to detect MGMT promoter methylation, and polymerase chain reaction amplification and Sanger sequencing were utilized to detect IDH1/2 mutation. Of the 33 examined SCLC specimens, MGMT promoter methylation was detected in 17 patients (51.5%), and no IDH1/2 mutations were detected in the analyzed samples. These findings indicate that the IDH1/2 mutation may not be an ideal marker in SCLC patients treated with temozolomide. Future studies on the predictive and prognostic value of MGMT promoter methylation are urgently required for patients with relapsed SCLC treated with temozolomide in China.