Purpose: The insulin-like growth factor 1 receptor (IGF1R) is widely expressed in normal tissues and many malignancies in humans. We investigated the clinical significance of the expression of the IGF1R gene in human lung adenocarcinoma.
Methods: A total of 238 patients with lung adenocarcinoma were investigated. Quantitative real-time reverse-transcription polymerase chain reaction (RT-PCR) assays were performed to evaluate the gene expression of IGF1R, and immunohistochemical staining was done to evaluate the protein expression of IGF1R.
Results: Among the 238 patients with lung adenocarcinoma, 107 tumors (45.0%) were IGF1R-low and 131 tumors (55.0%) were IGF1R-high. The IGF1R gene expression ratio was significantly lower in moderately to poorly differentiated adenocarcinomas than in well-differentiated adenocarcinomas (P = 0.0388). Gene expression of IGF1R was significantly correlated with protein expression of IGF1R (r = 0.7163, P < 0.0001). Regarding patient survival, overall survival was significantly lower in patients with IGF1R-low tumors than in those with IGF1R-high tumors (63.2% versus 76.1% 5-year survival, P = 0.0188). Multivariate analysis using a Cox proportional-hazards model demonstrated that IGF1R gene status was a significant prognostic factor predicting overall survival of patients with lung adenocarcinoma (hazard ratio 1.800; P = 0.0321). Moreover, the disease-free survival rate was significantly lower in patients with IGF1R-low tumors than in those with IGF1R-high tumors (49.2% versus 64.6% 5-year survival, P = 0.0084).
Conclusion: The present study suggests the level of IGF1R expression to be a useful prognostic marker for patients with dedifferentiated lung adenocarcinoma.