The proto-oncogene/translation factor eIF4E: a survey of its expression in breast carcinomas

The eukaryotic translation initiation factor eIF-4E binds to the cap structure of mRNAs as one component of the eIF-4 translation initiation complex, which mediates the recruitment of mRNA to the ribosomes. Overexpression of eIF-4E can result in oncogenic transformation and uncontrolled growth of mammalian cells, presumably by facilitating the expression of growth-control gene products which are normally translationally repressed. Whereas the mechanism of eIF-4E-mediated transformation is being actively pursued, clinical investigations into the expression of eIF-4E in prevalent human cancers are lacking. We have recently initiated a screen of breast carcinomas by probing with eIF-4E antiserum. Using Western blots, we have analyzed the level of eIF-4E in 38 carcinomas, 7 normal samples and 3 fibroadenomas. We found that eIF-4E was elevated 3- to 10-fold in virtually all the carcinomas we analyzed, but not in fibroadenomas. This analysis was also confirmed by immunohistological staining in situ, showing that overexpression of eIF-4E can be readily identified at the single-cell level. Our results suggest that an elevation of eIF-4E may be an essential component in the development of breast cancer.