This proposal explores the relationship between the levels of free functional eIF-4E (the mRNA cap binding protein) and the tumorigenic and metastatic properties of human breast cancer cell lines. Previous studies have shown that eIF-4E is elevated in human breast carcinomas as well as in established breast carcinoma cell lines when compared to normal or benign disease controls. EIF-4E is considered the rate limiting factor in the formation of the eIF-4E initiation complex, the rate-limiting factor in the translation of messenger RNAs. Increased eIF-4E levels have profound influences on the efficiency of translation of certain mRNAs which have long 5'-untranslated leader sequences, high GC content, and upstream in-frame initiation condons. This mRNA group includes many oncogenes (transcription and growth factors) as well as potent angiogenesis factors such as bFGF and VEFG. EIF-4E is also regulated by a binding protein (4EBP-PHAS-1) which can form complexes with eIF-r# in a non-phosphorylated state. This proposal examines the effects of reducing eIF-4E, increasing PHAS-1, or modifying the activities of complexes and the resultant effect on the level of eIF-4E which can participate in mRNA translation. The effect of these interactions on the expression of translationally regulated bFGF and VEGF are studied in comparison to non-translationally regulated B-actin and ras. Additionally, the effect of these interactions on the initiation and growth of breast cancer tumors will be investigated. Tissue samples from established tumors will be examined for the interaction between eIF-4E and 4EBP/PHAS-1 and resultant effect on expression of translationally and nontranslationally regulated molecules. These samples will be taken to monitor the effects of the treatment of the tumors with genes or drugs that affect eIF-4E function.
