Insulin-like growth factor II-messenger RNA-binding protein-3 and lung cancer

Insulin-like growth factor II-messenger RNA-binding protein 3 (IMP3) is an oncofetal RNA-binding protein that promotes tumor cell proliferation by enhancing IGF-II protein synthesis and inducing cell adhesion and invasion by stabilizing CD44 mRNA. IMP3 expression has been studied in many human neoplasms with growing evidence that IMP3 is a biomarker of enhanced tumor aggressiveness. IMP3 expression has been correlated with a poorer phenotypic profile including increased risk of metastases and decreased survival. Only a few studies have examined IMP3 expression in lung cancers. We review here the literature concerning IMP3 expression in lung neoplasms, specifically adenocarcinoma, squamous cell carcinoma, and neuroendocrine tumors of the lung. IMP3 immunohistochemical expression was reported in 27-55% of cases of primary pulmonary adenocarcinoma and in 75-90% of cases of squamous cell carcinoma of the lung. In adenocarcinoma, IMP3 expression was reported to be correlated with more poorly differentiated histological grade, advanced stage of disease and lymph node metastases. IMP3 expression also may be a marker of high grade pre-invasive squamous lesions including high grade dysplasia and carcinoma in situ. In neuroendocrine tumors of the lung, IMP3 expression was expressed in all reported cases of large cell neuroendocrine carcinoma and small cell lung carcinoma, but expression was limited in carcinoid tumors. Overall, IMP3 appears to be a useful diagnostic marker for lung cancer pathology including for discriminating high grade neuroendocrine tumors and low grade carcinoids and for identifying high grade pre-invasive squamous lesions.