Antineoplastic effect of ERK 1/2 and Akt inhibition by VDR agonists in vGPCR endothelial cells

Abstract

The Kaposi‘s Sarcoma-associated Herpes virus G Protein-Coupled Receptor (vGPCR) is a key molecule in the pathogenesis of Kaposi Sarcoma. In the present work, we studied the role of ERK1/2 and Akt regulation by VDR agonists, 1α,25(OH)2D3 and TX 527, of antiproliferative actions in vGPCR cells.The results showed that incubation with the MEK inhibitor PD98059 (10 µM) or Akt inhibitor, Inhibitor IV (2.5 µM) decreased cell number after 72 h treatment. Western blot analysis of time (24-48 h) and dose response studies (0.1- 100 nM) showed that 1α,25(OH)2D3 or TX527 (10 nM) decreased ERK1/2 and Akt protein phosphorylation. MKP-3, a specific phosphatase that attenuate ERK1/2 signaling, was found increased in western blot and qRT-PCR time response studies after 1α,25(OH)2D3 or TX527 treatment. This was correlated with p-ERK1/2 inhibition. ERK and Akt antineoplastic participation was evaluated using pharmacological inhibition. qRT-PCR studies (24h) revealed that 1α,25(OH)2D3, TX 527 (both 10nM) and PD (10 μM) treatment decreased IL-6, A20 and NF-κB gene expression while the opposite effect was observed for Bim. However, all genes studied exhibited an mRNA increased in cells incubated with Inhibitor IV (2.5 μM). All together, these results suggest that 1α,25(OH)2D3 and TX 527 inhibit proliferation involving ERK and Akt inhibition as part of an anti-angiogenic and anti-inflammatory mechanism^.