LAUSR

ABSTRACT Metastasis of breast cancer cells to distant organs is responsible for ∼50% of breast cancer-related deaths in women worldwide. SHIP2 (also known as INPPL1) is a phosphoinositide 5-phosphatase for phosphatidylinositol (3,4,5)-trisphosphate [PI(3,4,5)P3] and phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2]. Here we show, through depletion of SHIP2 in triple negative MDA-MB-231 cells and the use of SHIP2 inhibitors, that cell migration appears to be positively controlled by SHIP2. The effect of SHIP2 on migration, as observed in MDA-MB-231 cells, appears to be mediated by PI(3,4)P2. Adhesion on fibronectin is always increased in SHIP2-depleted cells. Apoptosis measured in MDA-MB-231 cells is also increased in SHIP2-depleted cells as compared to control cells. In xenograft mice, SHIP2-depleted MDA-MB-231 cells form significantly smaller tumors than those formed by control cells and less metastasis is detected in lung sections. Our data reveal a general role for SHIP2 in the control of cell migration in breast cancer cells and a second messenger role for PI(3,4)P2 in the migration mechanism. In MDA-MB-231 cells, SHIP2 has a function in apoptosis in cells incubated in vitro and in mouse tumor-derived cells, which could account for its role on tumor growth determined in vivo. Summary: There is a general role for SHIP2 in the control of cell migration in breast cancer cells, and this protein acts through a mechanism that involves PI(3,4)P2 as a secondary messenger.