TRANSFORMATION OF THYROID EPITHELIUM IS ASSOCIATED WITH LOSS OF C-KITRECEPTOR

The receptor for the stem cell factor encoded by the c-kit proto-oncog ene is expressed by a number of epithelial cells including thyrocytes. Since malignant transformation may be associated with loss of this re ceptor (melanoma and breast cancer), we have analyzed its expression i n benign (38 cases) and malignant (31 cases) thyroid lesions. While lo w levels of c-kit are expressed in normal thyroids and in 60% of benig n lesions, the receptor is undetectable in 60 and 90% of the follicula r and papillary carcinomas, respectively. Northern blot analysis from surgical specimens of carcinomas and from carcinoma cell lines has dem onstrated a lack of specific c-kit transcripts. These findings indicat e that the c-kit receptor may be involved in the growth control of thy roid epithelium and that this function may be lost following malignant transformation.