Implication of integrin α2β1 in senescence of SK-Mel-147 human melanoma cells

Involvement of Matricellular Proteins in Cellular Senescence: Potential Therapeutic Targets for Age-Related Diseases

Senescence is a physiological and pathological cellular program triggered by various types of cellular stress. Senescent cells exhibit multiple characteristic changes. Among them, the characteristic flattened and enlarged morphology exhibited in senescent cells is observed regardless of the stimuli causing the senescence. Several studies have provided important insights into pro-adhesive properties of cellular senescence, suggesting that cell adhesion to the extracellular matrix (ECM), which is involved in characteristic morphological changes, may play pivotal roles in cellular senescence. Matricellular proteins, a group of structurally unrelated ECM molecules that are secreted into the extracellular environment, have the unique ability to control cell adhesion to the ECM by binding to cell adhesion receptors, including integrins. Recent reports have certified that matricellular proteins are closely involved in cellular senescence. Through this biological function, matricellular proteins are thought to play important roles in the pathogenesis of age-related diseases, including fibrosis, osteoarthritis, intervertebral disc degeneration, atherosclerosis, and cancer. This review outlines recent studies on the role of matricellular proteins in inducing cellular senescence. We highlight the role of integrin-mediated signaling in inducing cellular senescence and provide new therapeutic options for age-related diseases targeting matricellular proteins and integrins.

The characteristics and the multiple functions of integrin β1 in human cancers

Integrins, which consist of two non-covalently linked α and β subunits, play a crucial role in cell-cell adhesion and cell-extracellular matrix (ECM) interactions. Among them, integrin β1 is the most common subunit and has emerged as a key mediator in cancer, influencing various aspects of cancer progression, including cell motility, adhesion, migration, proliferation, differentiation and chemotherapy resistance. However, given the complexity and sometimes contradictory characteristics, targeting integrin β1 for therapeutics has been a challenge. The emerging understanding of the mechanisms regulating by integrin β1 may guide the development of new strategies for anti-cancer therapy. In this review, we summarize the multiple functions of integrin β1 and signaling pathways which underlie the involvement of integrin β1 in several malignant cancers. Our review suggests the possibility of using integrin β1 as a therapeutic target and highlights the need for patient stratification based on expression of different integrin receptors in future clinical studies.

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.

Snake venom, a potential treatment for melanoma. A systematic review

Despite advances in treating patients with melanoma, there are still many treatment challenges to overcome. Studies with snake venom-derived proteins/peptides describe their binding potential, and inhibition of some proliferative mechanisms in melanoma. The combined use of these compounds with current therapies could be the strategic gap that will help us discover more effective treatments for melanoma. The present study aimed to carry out a systematic review identifying snake venom proteins and peptides described in the literature with antitumor, antimetastatic, or antiangiogenic effects on melanoma and determine the mechanisms of action that lead to these anti-tumor effects. Snake venoms contain proteins and peptides which are antiaggregant, antimetastatic, and antiangiogenic. The in vivo results are encouraging, considering the reduction of metastases and tumor size after treatment. In addition to these results, it was reported that these venom compounds could act in combination with chemotherapeutics (Acurhagin-C; Macrovipecetin), sensitizing and preparing tumor cells for treatment. There is a consensus that snake venom is a promising strategy for the improvement of antimelanoma therapies, but it has been little explored in the current context, combined with inhibitors, immunotherapy or tumor microenvironment, for example. We suggest Lebein as a candidate for combination therapy with BRAF inhibitors.

[Integrin α3β1 signaling in regulation of the SK-Mel-147 melanoma cell senescence]

Using a model of the human SK-Mel-147 melanoma cell line, it was shown that blocking the expression of integrin α3β1 by transduction of cells with α3-specific shRNA did not affect their proliferation, but sharply increased the proportion of SA-β-Gal-positive cells, a phenotypic feature of cell senescence. These findings were accompanied by a significant increase in the activity of the Akt and mTOR protein kinases and the expression of p53 and p21 oncosupressors. Pharmacological inhibition of mTORC1 reduced the number SA-β-Gal-positive cells in the SK-Mel-147 cell population depleted of α3β1. Based on our recent data on a non-canonical function of Akt isomers in the regulation of SK-Mel-147 cell senescence caused by deficiency of α2β1 receptor, we investigated the role of Akt isomers in senescence induced by the α3β1 knockdown. It appeared that in the cell population with downregulated α3β1, inhibition of Akt1 reduced the number SA-β-Gal positive cells to the level of control cell population, while inhibition of Akt2 had no visible effect. Our results demonstrate that the laminin-specific integrin α3β1, like the collagen-specific receptor α2β1, is involved in tumor cell protection from senescence, and senescence induced by α3β1 depletion, like that caused by α2β1 deficiency, is based on a signaling mechanism employing a non-canonical function of the Akt1 isoform.