Effflelct of placenta growth factor-1 on proliferation and release of nitric oxide, cyclic AMP and cyclic GMP in human epithelial cells expressing the FLT-1 receptor

We investigated the effect of placenta growth factor-1 (PIGF-1) on cell growth and on the release of nitric oxide (NO), cyclic AMP (cAMP) and cyclic GMP (cGMP) in human malignant epithelial cells. A noteworthy increase in proliferation was induced in choriocarcinoma cells (BeWo) by PIGF-1 treatment, while breast cancer cells (CG-5) were minimally affected. Western blotting and immunocytochemistry demonstrated the expression of the PIGF-1 receptor fms-like tyrosine kinase-1 (Flt-1) in these models. NO was released in the BeWo culture medium as a result of PIGF-1 treatment, with maximal induction occurring after 6 h. Enhanced cAMP levels were observed after 80 min- 6 h, while the amounts of cGMP produced were undetectable. In summary, lGF-1 stimulates the proliferation of cell types that express Flt-1, other than endothelial cells. In BeWo cells, this effect is preceded by the induction of NO and cAMP as probable downstream effectors of Flt-1 activation.