The Role And Mechanism Of SMLR1 In The Development And Progression Of Colorectal Cancer Liver Metastases

BackgroundColorectal cancer(CRC)is one of the most common malignant tumors in the world,tumor distant metastasis is the leading cause of mortality in patients with CRC,and colorectal cancer liver metastasis(CRLM)is the most common and deadly distant metastasis in CRC patients.Tumor distant metastasis is a multi-step,selective and complex process.Generally metastatic tumor cells are similar to primary tumor cells interms of genomics.However,due to the influence of different tumor microenvironments(TME),metastatic tumor cells will adapt to the new microenvironment through genetic changes.Liver TME and colorectal TME have significant differences in cellular composition and molecular characteristics.After CRC tumor cells migrate and colonize the liver through the circulatory system,what mechanism they will use to ensure their own survival,growth,and proliferation in liver.Thereby promot the occurrence and development of CRLM,the mechanism is currently still unclear.However,current research on CRC mainly focuses on primary tumors,and little is known about the mechanism of liver metastases.Therefore,further exploration of the occurrence and development mechanism of CRLM has important clinical significance for developing new and effective treatments for liver metastases and improving the prognosis of CRLM patients.Methods(1)Microarray datasets and high-throughput sequencing datasets were collected from Gene Expression Omnibus(GEO)to identify the differences in the expression levels of SMLR1 between CRC primary tumors and CRC liver metastases,and two pairs of organoids from CRLM patients were used to verify the expression difference by performing q PCR experiments.(2)Gene Set Enrichment Analysis(GSEA)and pearson correlation analysis were performed on high-throughput sequencing data to explore the potential function and molecular mechanism of SMLR1.(3)The role of SMLR1 in the process of CRLM was verified by constructing mouse models of CRLM overexpressing SMLR1,and the effect of SMLR1 on the survival prognosis of CRLM mice was explored by survival analysis.(4)Co-immunoprecipitation(Co-IP),mass spectrometry analysis,and Western Blot(WB)were performed to further explore the molecular mechanism of SMLR1 in promoting the occurrence and development of CRLM.(5)Vitro cellular retention assay was used to further verify the direct interaction of CRC tumor cells expressing SMLR1 with CD206~+/CD169~+macrophages.(6)Explore the quantitative changes of CD206~+/CD169~+macrophages in the liver of CRLM mice model overexpressing SMLR1 by flow cytometry fluorescence sorting technology(FACS).Results(1)SMLR1 was significantly upregulated in liver metastasis tissues compared with the expression level in primary tumor tissues of patients with CRLM,and there is no significant difference in the expression level of SMLR1 between normal colorectal tissues and primary tumor tissues.(2)The results of GSEA analysis indicated that the role of SMRL1 in the occurrence and development of CRLM was closely related to the activation of macrophages and the inhibition of the tumor immune microenvironment,and the results of the Pearson correlation analysis further showed that SMLR1 was significantly positively correlated with the expression of 11/16 M2-like macrophage-related molecular markers(p<0.05).(3)In vivo experiments of CRLM mouse model,the results showed that overexpression of SMRL1 in CRC metastatic tumor cells could significantly promote the development and progression of CRLM.(4)The results of co-IP,Mass spectrometry analysis,and WB suggested that protein SMLR1 could specifically and physically interact with protein CD206 and protein CD169.(5)The results of the vitro cellular retention assay demonstrated that SMLR1 could promote the direct interaction of CRC tumor cells with CD169~+/CD206~+macrophages.(6)Flow cytometry analysis showed that SMLR1 could promote the accumulation of CD169~+/CD206~+macrophages in liver metastases of CRLM mouse model.ConclusionLiver metastatic CRC tumor cells can physically interact with CD169~+/CD206~+macrophages by expressing SMLR1,and promote their accumulation in the liver,thereby promoting the occurrence and development of CRLM.