Mechanisms Of SOX4 In The Stemness Maintenance Of Cancer Stem Cells Via Regulating HDAC1

Background and objective: Cancer stem cells(CSCs)are a small subpopulation of cancer cells within the tumor tissue with stem cell-like properties.Cancer stem cells are the main cause of cancer recurrence and metastasis because of their high abilities of self-renewal,invasion,migration and drug resistance.Thus,cancer stem cells are the main target of cancer therapy.However,the mechanisms underlying stemness maintenance of cancer stem cells have remained elusive.The objective of this study is to investigate the novel mechanisms underlying cancer stemness maintenance and to identify potential drug target for eradicating cancer stem cells.SOX(SRY-related HMG-box genes)family members are a group of transcription factors,which plays important roles in organ development and cell fate decision.Studies have shown that one of the important SOX family members,SOX4,is involved in cancer cell proliferation,cell cycle,migration,invasion and drug resistance.While,whether SOX4 plays a key role in stemness maintenance of cancer stem cells have remained elusive.Thus,the second level of the objective of the study is to investigated the role of SOX4 in cancer stem cells.In addition,as a transcription factor,it is difficult to develop inhibitors specifically inhibit SOX4.The alternative strategy is to block to downstream pathways necessary for SOX4 driving cancer stemness.Thus,the third level of the study is to identify downstream pathways necessary for SOX4 driving cancer stemness.Methods: HCT-116 and HT-29 were used as cell model in this study and the stem cells were isolated by suspension culture.The characteristics of stemness were assessed by examination of sphere formation capacity,multi-generational sphere formation capacity,the frequency of sphere-forming cells and markers expression.The genetic manipulation was performed by lentivirus-based technologies.The differentiated expressed proteins in SOX4-overexpressing cells were identified by LC-MS-MS combined with bioinformatic methods.The mechanisms underlying SOX4 transcriptionally activates HDAC1 were identified by luciferase reporter assay and Ch IP assay.Results: SOX4 increased the stemness of colorectal cancer cells reflected by enhanced sphere formation,multi-generational sphere formation capacities and the frequency of sphere-forming cells and the expression levels of stem cell markers.Proteomic studies revealed that upregulation of HDAC1 is the potential mechanism underlying SOX4 promoting cancer stemness.HDAC1 increased the stemness of colorectal cancer cells and predicts poor prognosis of patients.Knockdown of HDAC1 abolished the effect of SOX4 on the stemness of colorectal cancer cells.SOX4 bound to the promoter of HDAC1 directly and transcriptionally activates HDAC1.SOX4 directly bound to HDAC1 promoter and activated HDAC1 transcription in multiple types of cancer cells.Conclusions: SOX4 directly binds to the promoter of HDAC1 and activates HDAC1 transcription to supports the stemness of cancer stem cells.SOX4-HDAC1 axis is conserved in multiple types of cancer cells.This result indicated that SOX4 is a drug target of cancer stem cells and HDAC1 inhibitor could be used for eradicating SOX4-drived cancer stem cells.