Chemotoxicity Induced Exosomal LncFERO Regulates Ferroptosis And Stemness In Gastric Cancer Stem Cells

Background: Cancer stem cells are an important cause of tumor recurrence and drug resistance.The chemosensitivity of cancers,including gastric cancer,is usually decreased due to the overexpression of "apoptosis inhibitors".In this sense,targeting non-apoptotic forms of cell death may have therapeutic benefits for cancer cells with apoptotic defects,particularly CSCs with natural apoptotic resistance.Ferroptosis,as a new type of cell death which relies on iron ions and is strictly regulated by intracellular and extracellular signals,has been identified as an important role in mediating tumor development and drug resistance in a variety of cancers,including gastric cancer,in recent studies,but the specific molecular mechanism remains unclear.The role of ferroptosis in cancer stem cells deserves extensive attention.Methods: Mass spectrum was applied to screen for ferroptosis-related proteins in gastric cancer(GC).Sphere formation assay was used to estimate the stemness of gastric cancer stem cells(GCSCs).Exosomal lnc RNA(exo-lnc FERO)was isolated by ultra-centrifugation.Ferroptosis was induced by erastin and was assessed by detecting lipid-ROS,mitochondrial membrane potential and cell death.Further,a series of functional in vitro and in vivo experiments were conducted to evaluate the effects of lnc FERO on regulating ferroptosis,stemness and chemosensitivity in GCSCs.Results:1)SCD1 protein was upregulated and closely related to both lipid metabolism and ferroptosis in GC.2)Exo-lnc FERO had a positive correlation with SCD1 protein expression.3)Exo-lnc FERO derived from GC cells inhibited ferroptosis and enhanced stemness in GCSCs.4)GC cells promoted SCD1 translation through the exo-lnc FERO/hn RNPA1/SCD1 axis to regulate ferroptosis and stemness in GCSCs.5)Chemotoxicity promoted exo-lnc FERO secretion from GC cells through the USP7/hn RNPA1 axis.6)Validation of the exo-lnc FERO’s role in regulating ferroptosis,stemness and chemosensitivity by using tumor-implanted mice.Here,we showed that Stearyl coenzyme A desaturatase 1(SCD1)inhibited the accumulation of lipid peroxides by changing the ratio between polyunsaturated and monounsaturated fatty acids,leading to suppressed ferroptosis and advanced stemness in GCSCs.Exo-lnc FERO derived from gastric cancer cells(GCCs)could be ingested by GCSCs to promote the translation of SCD1 by binding to the 5’UTR of SCD1 m RNA and recruiting heterogeneous nuclear ribonucleoprotein A1(hn RNPA1).Importantly,we found that hn RNPA1,stabilized by ubiquitin-specific protease 7(USP7),played a key role in mediating lnc FERO packing into exosomes.Furthermore,chemotoxicity could promote the secretion of exo-lnc FERO through the USP7/hn RNPA1 axis,and finally decreased chemosensitivity of gastric tumors through the exo-lnc FERO/hn RNPA1/SCD1 axis.Conclusions: Our study proved that gastric cancer cells could promote the release of exo-lnc FERO through the USP7/hn RNPA1 axis to regulate SCD1 protein expression with the assistance of hn RNPA1,resulting in decreased content of polyunsaturated fatty acids,suppressed ferroptosis and advanced stemness in GCSCs.The novel intercellular pathway contributed to chemoresistance.Our study suggested that targeting the exosome-mediated crosstalk between CSCs and cancer cells serves as an efficient method for the prevention of chemoresistance as well as gastric cancer recurrence.