La pourpre de Méditerranée, une source inattendue d’inhibiteurs de GSK-3

A novel 7-bromoindirubin with potent anticancer activity suppresses survival of human melanoma cells associated with inhibition of STAT3 and Akt signaling

STAT3 and Akt signaling have been validated as potential molecular targets for treatment of cancers including melanoma. These small molecule inhibitors of STAT3 or Akt signaling are promising for developing anti-melanoma therapeutic agents. MLS-2438, a novel 7-bromoindirubin, a derivative of the natural product indirubin, was synthesized with a bromo-group at the 7-position on one indole ring and a hydrophilic group at the 3'-position on the other indole ring. We tested the anticancer activity of MLS-2438 and investigated its mechanism of action in human melanoma cell lines. Here, we show that MLS-2438 inhibits viability and induces apoptosis of human melanoma cells associated with inhibition of STAT3 and Akt signaling. Several pro-apoptotic Bcl-2 family proteins are involved in the MLS-2438 mediated apoptosis. MLS-2438 inhibits Src kinase activity in vitro and phosphorylation of JAK2, Src, STAT3 and Akt in cultured cancer cells. In contrast to the decreased phosphorylation levels of JAK2, Src, STAT3 and Akt, phosphorylation levels of the MAPK (Erk1/2) signaling protein were not reduced in cells treated with MLS-2438. These results demonstrate that MLS-2438, a novel natural product derivative, is a Src inhibitor and potentially regulates kinase activity of JAK2 and Akt in cancer cells. Importantly, MLS-2438 suppressed tumor growth with low toxicity in a mouse xenograft model of human melanoma. Our findings support further development of MLS-2438 as a potential small-molecule therapeutic agent that targets both STAT3 and Akt signaling in human melanoma cells.

[Cell cycle and molecular targets: CDK inhibition]

Protein phosphorylation is a fundamental post-translational modification. It regulates a large number of critical cellular processes (differentiation, division, proliferation, apoptosis). Cell division is a process including a series of phases by which a parent cell divides into two daughter cells. The cells enter these stages then progress within the cell division under an accurate control by many proteins. These proteins are activated by phosphorylation. Cyclin-dependent kinases are responsible for this phosphorylation and therefore represent potential therapeutic targets especially in oncology.