Hotsuliak N. The role of mTOR signaling network in the regulation of locomotor properties of tumor cells under the influence of the microenvironment

The dissertation is devoted to the identification, differentiation and characterization of the functions of p85S6K1, p70S6K1 and p60S6K1 isoforms of S6K1 kinase, as elements of the mTOR signaling network, in the process of perception of signals generated by the tumor microenvironment and their transformation in regulation of cell motility. The ability of the mTOR/S6K1 signaling link in breast cancer cells to perceive and mediate the effect of molecules of paracrine signaling of fibroblasts has been shown. The ability of dermal fibroblasts to enhance in paracrine manner the activity of breast cancer cell migration in two-dimensional and three-dimensional models under unilateral exposure or bilateral interaction, as well as involvement of mTOR/S6K1 signaling in the regulation of such activation has been demonstrated. The ability of dermal fibroblasts to restrict the migration activity of breast cancer cells under direct physical interaction in three-dimensional conditions has been demonstrated. The involvement of p85S6K1, p70S6K1 and p60S6K1 isoforms of S6K1 kinase in a number of cell processes and the differences in their roles in the latter are established, in particular: in regulation of cell motility under the influence of paracrine signaling of fibroblasts; maintaining the normal morphology of breast cancer cells; ability to self-organize in space in the form of multicellular spheroids and the implementation of cell migration strategies; regulation of the activity of elements of the PI3K/AKT/mTOR signaling pathway ‒ AKT, GSK-3β and eEF2K kinases; regulation of the degree of phosphorylation of S6, RAPTOR proteins and AKT kinase target proteins; expression of cell adhesion proteins ‒ CD326, CD227 and CD66e; expression of cell adhesion proteins with mechanoreception functions ‒ CD29 and CD44; activity of the regulator of restructuring of adhesive contacts ‒ FAK kinase; activity of expression of cytoskeleton proteins ‒ β-actin and histospecific ones ‒ cytokeratins and vimentin; expression of tight junction protein ‒ ZO-1. A modification of the "wound surface" model has been developed and adapted, which makes it possible to measure the migratory activity of cells under conditions of co-cultivation.