Effects of progesterone and selective ligands of membrane progesterone receptors in HepG2 cells of human hepatocellular carcinoma

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Progesterone exerts multiple effects in different tissues through nuclear receptors (nPRs) and through membrane receptors of the adiponectin and progestin receptor (mPRs) family. The effect of progesterone on cells through different types of receptors can vary significantly. At the same time, it affects the processes of proliferation and apoptosis in normal and tumor tissues in a dual way, stimulating proliferation and carcinogenesis in some tissues, suppressing them and stimulating cell death in others. In this study, we have shown the presence of a high level of mRNA and mPRβ protein in HepG2 tumor cells of human hepatocellular carcinoma. Expression of other membrane and classical nuclear receptors was not detected. May be mPRβ has an important function in HepG2 cells. The main goal of the work was to study the function of this protein and the mechanisms of its action in human hepatocellular carcinoma cells. Previously, we have identified selective mPRs ligands, compounds LS-01 and LS-02, which do not interact with nuclear receptors. Their employment allows differentiating the effects of progestins mediated by different types of receptors. The work studied the effects of progesterone, LS-01 and LS-02 on the proliferation and death of HepG2 cells, as well as the activating phosphorylation of two kinases, p38 MAPK and JNK, under the action of three steroids. It was shown that all three progestins after 72 hours of incubation with cells suppressed their viability and stimulated the appearance of phosphatidylserine on the outer surface of membranes, which was detected by binding to V-FITC annexin, but they did not affect DNA fragmentation of cell nuclei. Progesterone significantly reduced the expression of proliferation marker genes and stimulated the expression of the p21 protein gene, but had a suppressive effect on the expression of some proapoptotic factor genes. All three steroids activated JNK in these cells, but had no effect on p38 MAPK activity. The effects of progesterone and selective mPRs ligands in HepG2 cells were the same in terms of suppression of proliferation and stimulation of apoptotic changes in outer membranes, therefore, they were mediated through interaction with mPRβ. JNK is a member of the signaling cascade activated in these cells by the studied steroids.