Insulin-like growth factor II (IGF-II) mRNA was increased in two of eight neuroblastomas and in eight of eight pheochromocytomas, tumors of the adrenal medulla that occur in childhood and adulthood, respectively. RNA encoding the type I IGF receptor, the receptor thought to mediate the mitogenic effects of IGF-I and IGF-II, also was uniformly expressed in these cells. To assess the role of IGF-II in the growth of these tumor cells, we have used the SK-N-AS cultured neuroblastoma cell line, which can be continuously propagated in mitogen-free medium, as a model system. Our results strongly suggest that IGF-II, synthesized by SK-N-AS cells and acting through type

Neuroblastoma is an embryonal tumor that typically arises in cells of the developing adrenal medulla. IGF-II mRNA is expressed at high levels in the adrenal cortex before birth but it is not detectable until after birth in the adrenal medulla. Neuroblastoma cell lines corresponding to early adrenal medullary precursors did not express IGF-II, although all three cell lines we tested were growth stimulated by IGF-II. Cell lines corresponding to more mature adrenal medullary cells expressed IGF-II, and one, SK-N-AS, grows by an IGF-II autocrine mechanism (J. Clin. Invest. 84:829-839) El-Badry, Romanus, Helman, Cooper, Rechler, and Israel. 1989. An examination of human neuroblastoma tumor tissues for IGF-II gene expression using in situ hybridization histochemistry revealed that IGF-II is expressed by tumor cells in only 5 of 21 neuroblastomas, but is detectable in cells of nonmalignant tissues including adrenal cortical cells, stromal fibroblasts, and eosinophils in all 21 tumors. These findings indicate that IGF-II may function as an autocrine growth factor for some neuroblastomas and as a paracrine growth factor for others. They suggest that the growth regulatory pathways utilized by neuroblastoma mimic those used in the precursor cell type from which individual tumors arise. (J. Clin. Invest. 1991. 87:648-657.)

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