TRANSFORMING GROWTH-FACTOR-ALPHA AND ENDOCRINE SENSITIVITY IN BREAST-CANCER

The expression of transforming growth factor-alpha (TGF-alpha) has bee n evaluated in 51 breast cancers of known responsiveness to endocrine therapy using immunohistochemistry. High levels of TGF-alpha were obse rved in 65% of tumors and showed no relationship with tumor estrogen r eceptor or epidermal growth factor receptor status or Ki67 immunostain ing. TGF-alpha levels did, however, relate to the endocrine sensitivit y of the disease, with unresponsive tumors frequently showing high lev els of TGF-alpha immunoreactivity. This relationship was observed in e strogen receptor-positive disease and was independent of the epidermal growth factor receptor status of the tumor. No quantitative associati on between TGF-alpha and Ki67 immunostaining was observed in any of th e subcategories of tumors. These data infer a role for TGF-alpha in th e development of endocrine insensitivity in estrogen receptor-positive breast cancer by mechanisms which appear independent of tumor growth fraction, as determined by Ki67 immunostaining.