Overexpression of insulin-like growth factor-binding protein-2 results in increased tumorigenic potential in Y-1 adrenocortical tumor cells

Increased concentrations of insulin-like growth factor-binding protein-2 (I GFBP-2) have been observed in human malignancies including adrenocortical c arcinomas. To elucidate the functional consequences of IGFBP-2 overexpressi on, we have stably transfected the cDNA of murine IGFBP-2 in mouse adrenoco rtical tumor cells (Y-1). Long-term overexpression of IGFBP-2 was associate d with significant morphological alterations, enhanced cell proliferation, and increased cloning efficiency as compared with mock transfected control cells, The enhanced proliferation of IGFBP-2 secreting clones was independe nt of exogenous insulin-like growth factors (IGFs), These data suggest that elevated Levels of IGFBP-2 may contribute to the highly malignant phenotyp e of adrenocortical cancer by a thus far unknown, presumably IGF-independen t, mechanism.