Implication of integrin α5β1 in senescence of SK-Mel-147 human melanoma cells.

Downregulation of α5β1 integrin in the SK-Mel-147 human melanoma culture model sharply inhibits the phenotypic manifestations of tumor progression: cell proliferation and clonal activity. This was accompanied by a 2-3-fold increase in the content of SA-β-Gal positive cells thus indicating an increase in the cellular senescence phenotype. These changes were accompanied by a significant increase in the activity of p53 and p21 tumor suppressors and components of the PI3K/Akt/mTOR/p70 signaling pathway. Pharmacological inhibition of mTORC1 reduced the content of SA-β-Gal positive cells in the population of α5β1-deficient SK-Mel-147 cells. A similar effect was observed with pharmacological and genetic inhibition of the activity of Akt1, one of the three Akt protein kinase isoenzymes; suppression of other Akt isozymes did not affect melanoma cell senescence. The results presented in this work and previously obtained indicate that α5β1 shares with other integrins of the β1 family the function of cell protection from senescence. This function is realized via regulation of the PI3K/Akt1/mTOR signaling pathway, in which Akt1 exhibits a non-canonical activity.