Pleiotrophin transforms NIH 3T3 cells and induces tumors in nude mice

The pleiotrophin (PTN) gene (Ptn) encodes an 18-kDa protein that is highly conserved among mammalian species and that functions as a weak mitogen and promotes neurite-outgrowth activity in vitro. To further investigate the role PTN plays in regulating cell growth, we overexpressed the bovine PTN cDNA and now show that PTN phenotypically transforms NIH 3T3 cells, as evidenced by increased cell number at confluence, focus formation, anchorage-independent growth, and tumor formation in the nude mouse. The results demonstrate that the Ptn gene has the potential to regulate NIH 3T3 cell growth and suggest that PTN may influence abnormal cell growth in vivo.