Effect Of FTY720 On Autophagy And Possible Mechanisms In Colorectal Cancer

Background:FTY720, also known as fingolimod, is a widely used immunomodulator in multiple sclerosis and multiple organ transplantation. It is also an important protein phosphatase 2A (PP2A) activator. Based on this, a number of studies have recently demonstrated the cytotoxic effect of FTY720 in various cancers. Yet in colorectal cancer (CRC), the underlying mechanisms of FTY720 cytotoxicity remain less clear, especially the relationship between a drug and autophagy.Objective:To explore the effects of FTY720 on autophagy and its possible mechanism in CRC.Methods:The effects of FTY720 on the physiological function of CRC were detected by CCK-8, Colony formation assay, Flow cytometric analysis of apoptosis, Western blot analysis and Cell cycle analysis.. Using transmission electron microscopy, confocal scanning electron microscopy, and Western blot analysis to verify the effect of FTY720 on autophagy in CRC. Using 3-MA to inhibit autophagy and to observe the activity of cells in order to determine whether autophagy is a protective or cytotoxic effect. Using si-RNA interference CIP2A then observe the expression level of LC3 to determine whether CIP2A is involved in the process of FTY720 promoted autophagy.Results:FTY720 promotes the appearance of autophagic hallmarks such as autophagosome formation and light chain 3 (LC3)-Ⅱ accumulation, indicating the participation of autophagy in FTY720 cytotoxicity on CRC. Moreover, inhibition of autophagy using 3-methyladenine (3-MA), a specific inhibitor of autophagy, enhanced FTY720 cytotoxicity, indicating the protective role of autophagy against the drug’s own cytotoxic effect. The protective autophagy was likely affected by cancerous inhibitor of PP2A (CIP2A), an endogenous PP2A inhibitor that is closely related with poor prognosis and drug resistance.Conclusion:FTY720 has a significant cytotoxic effect on CRC. However, protective autophagy is a risk factor for FTY720 resistance. Yet, CIP2A, which is highly expressed and closely related to drug resistance, can block FTY720-induced autophagy so that it improves FTY720 sensitivity. This provides a new strategy for treating CRC, especially in cases resistant to conventional chemotherapies because of high CIP2A levels...