Objective: Dexamethasone (DEX) is a glucocorticoid that is commonly used in clinics. Previously, DEX has been shown to inhibit the function of immune system; however, DEX is often used to treat side reactions, such as nausea and vomiting caused by chemotherapy in clinics. Therefore, it is necessary to study the role of DEX in the treatment of cancer.
Methods: The effects of DEX on HepG2 were studied in vitro by Cell Counting Kit-8 method, cell cycle, and scratch test. The transplanted tumor model of HepG2 was established in nude mice to study the anti-tumor effect of DEX in vivo. In addition, in order to study the effect of DEX on the immune system, we also established a transplanted tumor model of 4T1 in normal immunized mice to study treatment effect and mechanism of DEX in mice of normal immune function.
Results: The results showed that DEX inhibited the proliferation of HepG2 in vitro and in vivo, affecting the cycle and migration of HepG2 cells, and the expression of c-Myc and the activation of mTOR signaling pathway were inhibited. The expression of key enzymes related to glucose metabolism is altered, especially that of phosphoenolpyruvate carboxykinase2 (PCK2). In normal immunized mice, DEX also inhibits the proliferation of tumor cells 4T1, while the proportion of CD4+CD45+T cells and CD8+CD45+ T cells in CD45+ cells in the lymph nodes upregulated, the proportion of Treg cells in CD4+ T cells downregulated in lymph nodes, and the proportion of MDSCs in tumor tissues downregulated.
Conclusion: DEX can inhibit tumor cells in vitro and in vivo. The mechanism is to inhibit the activation of mTOR signaling pathway by inhibiting the expression of c-Myc, further affecting the expression of key enzymes involved in glucose metabolism, especially PCK2.In addition, DEX has an inhibitory effect on the immune system, which may be the reason why DEX still has anti-tumor effect in normal mice.
Keywords: dexamethasone, glycolysis, Warburg effect, HepG2, 4T1, immune cells, immune system