Long form collapsin response mediator protein-1 (LCRMP-1) expression is associated with clinical outcome and lymph node metastasis in non-small cell lung cancer patients

Collapsin response mediator protein (CRMP) family proteins are cytosolic phosphoproteins involved in semaphorin 3A-mediated neuronal cell growth cone collapse and cancer invasion. We identified a novel human isoform of CRMP family proteins named long form CRMP-1 (LCRMP-1), which was different from the known invasion suppressor, CRMP-1, in its molecular weight and the N-terminal exon-1. This study was aimed to elucidate the clinical significance of LCRMP-1 in non-small cell lung cancer (NSCLC) patients. Full-length human LCRMP-1 was cloned from lung adenocarcinoma based on the Expressed Sequence Tags (EST) database. We generated LCRMP-1 specific antibody and subsequent in vitro and in vivo invasion assays showed positive correlations between LCRMP-1 expression and lung cancer cell invasiveness. We further demonstrated that high LCRMP-1 mRNA expressions were associated with poor overall and disease-free survivals (P = 0.004 and 0.006, respectively, log-rank test) in 72 NSCLC patients. The results were confirmed in an independent cohort of 54 NSCLC patients by immunohistochemistry (P = 0.032, log-rank test). The metastatic lymph nodes showed higher LCRMP-1 expressions as compared with the paired primary lung tumors (P = 0.012, McNemar's test). In conclusion, LCRMP-1 was a cancer invasion enhancer that could be a novel prognostic biomarker in NSCLC.