Expression of protein elongation factor eEF1A2 predicts favorable outcome in breast cancer.

Breast cancer is the most common malignancy among North American women. The identification of factors that predict outcome is key to individualized disease management and to our understanding of breast oncogenesis. We have analyzed mRNA expression of protein elongation factor eEF1A2 in two independent breast tumor populations of size n = 345 and n = 88, respectively. We find that eEF1A2 mRNA is expressed at a low level in normal breast epithelium but is detectably expressed in approximately 50-60% of primary human breast tumors. We have derived an eEF1A2-specific antibody and measured eEF1A2 protein expression in a sample of 438 primary breast tumors annotated with 20-year survival data. We find that high levels of eEF1A2 protein are detected in 60% of primary breast tumors independent of HER-2 protein expression, tumor size, lymph node status, and estrogen receptor (ER) expression. Importantly, we find that high eEF1A2 is a significant predictor of outcome. Women whose tumor has high eEF1A2 protein expression have an increased probability of 20-year survival compared to those women whose tumor does not express substantial eEF1A2. In addition, eEF1A2 protein expression predicts increased survival probability in those breast cancer patients whose tumor is HER-2 negative or who have lymph node involvement.