eIF4G-1 belongs to the family of translational initiation factors and is recognized as the central organizing protein in recruitment of mRNA during translational initiation. Previously published studies have provided some evidence that overexpression of translational factors is a general event in the process of carcinogenesis. We have characterized the expression of the eIF4G-1 protein in 33 squamous cell carcinoma (SCC) of the lung by Western blotting. Overexpression of the eIF4G-1 protein was detected in 61% of the tumors compared to the respective normal lung tissue. In addition, we analyzed the expression of this protein by immunohistochemistry in 138 SCC of the lung using a newly generated antibody that is specific for eIF4G-1 as determined by Western blotting. This anti-eIF4G-1 antibody was suitable for the immunohistochemistry of paraffin-embedded tissues. There is a strong cytoplasmic staining detected in the tumor areas that is consistent with the cytoplasmic localization of the translation factor eIF4G-1. In 72% of the examined tissue sections of SCCs of the lung, we detected an overexpression of the eIF4G-1 protein compared to the surrounding connective tissue. Two tumors that were analyzed by both methods showed an overexpression of eIF4G-1 both with Western blot analysis and immunohistochemical staining. Overexpression of eIF4G-1 may result in an increased amount of the translation initiation complex eIF4F, which in turn may activate the translation of the same target mRNAs as eIF4E.
Copyright 2001 Wiley-Liss, Inc.