Expression of insulin-like growth factor-I and -II genes in rat medullary thyroid carcinoma

Several types of cancer cells produce polypeptide growth factors and often the same cells have functional receptors for the released growth factor (autocrine secretion). We have studied expression of genes encoding somatomedin-C/insulin-like growth factor-I (Sm-C/IGF-I) and IGF-II, in rat medullary thyroid carcinomas (MTCs) in different stages of tumour differentiation. RNAs hybridizing specifically to an IGF-I cDNA probe were detected in 6 out of 7 differentiated MTCs and IGF-II related RNAs were demonstrated in 5 out of these 7 differentiated MTCs. In 5 anaplastic MTCs no IGF RNAs were detected, except for a small amount of IGF-II related RNA in one tumour.