In vitro activity: 3α-Aminocholestane (also known as 3AC) is a potent and selective SH2 domain-containing inositol-5′-phosphatase 1 (SHIP1) inhibitor with an IC50 of ~2.5 μM. It shows no inhibition on SHIP2 or PTEN. Many tumors present with increased activation of the phosphatidylinositol 3-kinase (PI3K)-PtdIns(3,4,5)P(3)-protein kinase B (PKB/Akt) signaling pathway. It has long been thought that the lipid phosphatases SH2 domain-containing inositol-5'-phosphatase 1 (SHIP1) and SHIP2 act as tumor suppressors by counteracting with the survival signal induced by this pathway through hydrolysis or PtdIns(3,4,5)P(3) to PtdIns(3,4)P(2). However, a growing body of evidence suggests that PtdInd(3,4)P(2) is capable of, and essential for, Akt activation, thus suggesting a potential role for SHIP1/2 enzymes as proto-oncogenes. 3AC is capable of killing malignant hematologic cells. In vivo growth of MM cells is blocked by treatment of mice with the SHIP1 inhibitor 3AC.

Kinase Assay: 3α-Aminocholestane (also known as 3AC) is a potent and selective SH2 domain-containing inositol-5′-phosphatase 1 (SHIP1) inhibitor with an IC50 of ~2.5 μM. It shows no inhibition on SHIP2 or PTEN.

Cell Assay: We recently described a novel SHIP1-selective chemical inhibitor (3α-aminocholestane [3AC]) that is capable of killing malignant hematologic cells. In this study, we further investigate the biochemical consequences of 3AC treatment in multiple myeloma (MM) and demonstrate that SHIP1 inhibition arrests MM cell lines in either G0/G1 or G2/M stages of the cell cycle, leading to caspase activation and apoptosis. In addition, we show that in vivo growth of MM cells is blocked by treatment of mice with the SHIP1 inhibitor 3AC. Furthermore, we identify three novel pan-SHIP1/2 inhibitors that efficiently kill MM cells through G2/M arrest, caspase activation and apoptosis induction. Interestingly, in SHIP2-expressing breast cancer cells that lack SHIP1 expression, pan-SHIP1/2 inhibition also reduces viable cell numbers, which can be rescued by addition of exogenous PtdIns(3,4)P(2). In conclusion, this study shows that inhibition of SHIP1 and SHIP2 may have broad clinical application in the treatment of multiple tumor types.