Molecular profiling of small cell lung cancer in a Japanese cohort

Advances in the molecular profiling of lung adenocarcinoma over the past decade have led to a paradigm shift in its diagnosis and treatment. However, there are very few reports on the molecular profiles of small cell lung cancers (SCLCs). We therefore conducted the present Shizuoka Lung Cancer Mutation Study to analyze genomic aberrations in patients with thoracic malignancies.

We collected samples of SCLC from a biobank system and analyzed their molecular profiles. We assessed 23 mutations in nine genes (EGFR, KRAS, BRAF, PIK3CA, NRAS, MEK1, AKT1, PTEN, and HER2) using pyrosequencing plus capillary electrophoresis. We also amplified EGFR, MET, PIK3CA, FGFR1, and FGFR2 using quantitative real-time polymerase chain reaction (PCR) and the fusion genes ALK, ROS1, and RET using reverse transcription PCR.

Between July 2011 and January 2013, 60 SCLC patients were enrolled in the study. Samples included eight surgically resected snap-frozen samples, 50 formalin-fixed paraffin-embedded samples, and seven pleural effusion samples. We detected 13 genomic aberrations in nine cases (15%), including an EGFR mutation (n=1, G719A), a KRAS mutation (n=1, G12D), PIK3CA mutations (n=3, E542K, E545K, E545Q), an AKT1 mutation (n=1, E17K), a MET amplification (n=1), and PIK3CA amplifications (n=6). EGFR and KRAS mutations were found in patients with combined SCLC and adenocarcinoma. No significant differences were detected in the characteristics of patients with and without genomic aberrations. However, serum neuron-specific enolase and progastrin-releasing peptide levels were significantly higher in patients without genomic aberrations than in those with aberrations (p=0.01 and 0.04, respectively).

Genomic aberrations were found in 15% SCLC patients, with PIK3CA amplifications most frequently observed. To further our understanding of the molecular profiles of SCLC, comprehensive mutational analyses should be conducted using massive parallel sequencing.