EXPRESSION OF A 32-KDA PROTEIN IN RAT MAMMARY-TUMORS INDUCED BY ANTI-BENZO[C]PHENANTHRENE-3,4-DIOL-1,2-EPOXIDE

Racemic anti-benzo[c]phenanthrene-3,4-diol-1,2-epoxide (BcPDE) is a po werful rat mammary carcinogen and a metabolite of benzo[c]phenanthrene , a polynuclear aromatic hydrocarbon found in the environment. In eluc idating potential molecular mechanisms that may play a role in the dev elopment of BcPDE-induced rat mammary tumors, we have identified a 32 kDa protein in 16 of 26 tumors analyzed but in only 1 of the 15 normal mammary tissues that were examined. The 32 kDa protein was identified with antibodies to Ets, which also recognized the 55 kDa Ets-l protei n that was expressed at similar levels in normal mammary tissues. The expression of the 32 kDa protein was also observed in mammary tumor-de rived cell lines of both rat and human origin and in human melanoma, b ut not in normal human keratinocytes or rat fibroblast cell lines. Fur ther characterization via 2D gels revealed that the protein exhibits a PI of 5.5. Southwestern analysis using Ets-l target sequence revealed binding of the 55 kDa Ets-l but not of the newly identified 32 kDa pr otein. Overall, the preferential expression of the 32 kDa protein in m ammary tumor tissues may serve as a biomarker to follow the developmen t of this tumor type. (C) 1996 Wiley-Liss, Inc.