C-KIT PROTOONCOGENE IS MORE LIKELY TO LOSE EXPRESSION IN DIFFERENTIATED THYROID-CARCINOMA THAN 3 THYROID-SPECIFIC GENES - THYROID PEROXIDASE, THYROGLOBULIN, AND THYROID-STIMULATING HORMONE-RECEPTOR

Although c-kit proto-oncogene product is known to be weakly expressed on normal thyrocytes, its function is unclear. In order to investigate the significance of thyroid c-kit, c-kit gene expression in 37 variou s thyroid tissues was analyzed by comparing c-kit gene expression with the mRNA expression of three thyroid-specific genes: thyroid peroxida se, thyroglobulin, and thyroid stimulating hormone receptor. c-kit mRN A was hardly detected by the usual northern blot method in 2 of 7 foll icular carcinomas, 11 of 12 papillary carcinomas, and a medullary carc inoma. On the other hand, a high level of c-kit mRNA expression was fo und in all 17 benign thyroid tissues (4 normal thyroid tissues, 4 Grav es' disease, 2 adenomatous goiters, and 7 follicular adenomas). This s tudy found that c-kif proto-oncogene is more likely to lose expression in differentiated thyroid carcinoma than any thyroid-specific gene. D ecreased c-kit gene expression may serve as an indicator for the de-di fferentiation of thyrocytes.