Abstract
To delineate distinctive role of the components of α5β1 integrin-EGFR axis in control of epidermoid carcinoma cell proliferation, we performed individual inhibition of α5β1 and EGFR via genetic and phamacological methods, respectively. We demonstrated that pharmacological inhibition of epidermal growth factor receptor (EGFR) significantly affected proliferation of A431 human cells by inducing the G0/G1 cell cycle arrest, whereas shRNA-mediated depletion of α5 subunit of α5β1 integrin led to a similar type of cell cycle arrest followed by significant apoptosis. Both treatments resulted in suppression of activated (phosphorylated) forms of focal adhesion kinase (FAK) and Erk. However, unlike EGFR inhibition, depletion of α5 led to substantial suppression of AKT activity. Accordingly, pharmacological inhibition of EGFR and AKT recapitulated detrimental effects caused by shRNA-mediated depletion of α5. Moreover, depletion of α5 led to a severe drop in the amounts of active EGFR. Thus, for the first time, we demonstrated that α5β1 integrin simultaneously maintains pro-survival signaling via continuous activation of AKT and up-regulates proliferation via activation of EGFR.
Highlights
Cell proliferation is controlled by cytokines including growth factors and the components of extracellular matrix
For the first time, we demonstrated that α5β1 integrin simultaneously maintains pro‐survival signaling via continuous activation of AKT and up‐regulates proliferation via activation of epidermal growth factor receptor (EGFR)
In human epidermoid carcinoma HEp3 cells, α5 integrin binding to the epidermal growth factor receptor, EGFR, enhanced proliferation [10] while in Caco-2 and HT-29 colorectal carcinoma cells, α5/EGFR binding resulted in EGFR lysosomal degradation followed by proliferation arrest [ 6]
Summary
Cell proliferation is controlled by cytokines including growth factors and the components of extracellular matrix. Both types of proteins initiate signal transduction through growth factor specific receptors and matrix-specific receptors integrins, and their disbalance may lead to the uncontrolled proliferation and carcinogenesis [1,2,3,4]. The mechanisms underlying the regulation of cell proliferation by integrins have not been completely characterized. One such mechanism includes interaction between integrins and growth factor receptors, GFR, with subsequent modification of GFR activity [2,11]. In human epidermoid carcinoma HEp3 cells, α5 integrin binding to the epidermal growth factor receptor, EGFR, enhanced proliferation [10] while in Caco-2 and HT-29 colorectal carcinoma cells, α5/EGFR binding resulted in EGFR lysosomal degradation followed by proliferation arrest [ 6]
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