Multiple roles of mothers against decapentaplegic homolog 4 in tumorigenesis, stem cells, drug resistance, and cancer therapy

The transforming growth factor(TGF)-βsignaling pathway controls many cellular processes,including proliferation,differentiation,and apoptosis.Abnormalities in the TGF-βsignaling pathway and its components are closely related to the occurrence of many human diseases,including cancer.Mothers against decapentaplegic homolog 4(Smad4),also known as deleted in pancreatic cancer locus 4,is a typical tumor suppressor candidate gene locating at q21.1 of human chromosome 18 and the common mediator of the TGF-β/Smad and bone morphogenetic protein/Smad signaling pathways.It is believed that Smad4 inactivation correlates with the development of tumors and stem cell fate decisions.Smad4 also interacts with cytokines,miRNAs,and other signaling pathways,jointly regulating cell behavior.However,the regulatory function of Smad4 in tumorigenesis,stem cells,and drug resistance is currently controversial.In addition,Smad4 represents an attractive therapeutic target for cancer.Elucidating the specific role of Smad4 is important for understanding the mechanism of tumorigenesis and cancer treatment.Here,we review the identification and characterization of Smad4,the canonical TGF-β/Smad pathway,as well as the multiple roles of Smad4 in tumorigenesis,stem cells,and drug resistance.Furthermore,we provide novel insights into the prospects of Smad4-targeted cancer therapy and the challenges that it will face in the future.

Genetic variations in the SMAD4 gene and gastric cancer susceptibility

AIM:To explore the association between mothers against decapentaplegic homolog 4 (SMAD4) gene polymorphisms and gastric cancer risk.METHODS:Five tagging single nucleotide polymor-phisms (tSNPs) in the SMAD4 gene were selected and genotyped in 322 gastric cancer cases and 351 cancerfree controls in a Chinese population by using the polymerase chain reactionrestriction fragment length polymorphism method.Immunohistochemistry was used to examine SMAD4 protein expression in 10 normal gastric tissues adjacent to tumors.RESULTS:In the single-locus analysis,two significantly decreased risk polymorphisms for gastric cancer were observed:the SNP3 rs17663887 TC genotype (adjusted odds ratio=0.38,95% confidence interval:0.21-0.71),compared with the wild-type TT genotype and the SNP5 rs12456284 GG genotype (0.31,0.16-0.60),and with the wild-type AA genotype.In the combined analyses of these two tSNPs,the combined genotypes with 2-3 protective alleles (SNP3 C and SNP5 G allele) had a significantly decreased risk of gastric cancer (0.28,0.16-0.49) than those with 0-1 protective allele.Furthermore,individuals with 0-1 protective allele had significantly decreased SMAD4 protein expression levels in the norma tissues adjacent to tumors than those with 2-3 protective alleles (P=0.025).CONCLUSION:These results suggest that genetic variants in the SMAD4 gene play a protective role in gastric cancer in a Chinese population.

Hsa_circRNA_102610 upregulation in Crohn’s disease promotes transforming growth factor-β1-induced epithelial-mesenchymal transition via sponging of hsa-miR-130a-3p

BACKGROUND The incidence of inflammatory bowel disease,a chronic intestinal inflammatory disorder that includes Crohn’s disease(CD)and ulcerative colitis,is rising.Circular RNAs are considered valuable diagnostic biomarkers for CD.Current evidence supports the views that epithelial-mesenchymal transition(EMT)plays an important role in CD pathogenesis,and that hsa-miR-130a-3p can inhibit transforming growth factor-β1(TGF-β1)-induced EMT.Our previous study revealed that hsa_circRNA_102610 was upregulated in CD patients.Moreover,we predicted an interaction between hsa_circRNA_102610 and hsa-miR-130a-3p.Thus,we hypothesized that hsa_circRNA_102610 may play roles in the proliferation and EMT of intestinal epithelial cells by sponging hsa-miR-130a-3p to participate in the pathogenesis of CD.AIM To explore the mechanism of hsa_circRNA_102610 in the pathogenesis of CD.METHODS The relative expression levels of hsa_circRNA_102610 and hsa-miR-130a-3p in patients were detected by quantitative reverse transcription-polymerase chain reaction.The proliferation of human intestinal epithelial cells(HIECs)and normal-derived colon mucosa cell line 460(NCM460)cells was detected by cell counting kit-8,5-ethynyl-2’-deoxyuridine staining and cell cycle assays following overexpression or downregulation of hsa_circRNA_102610.Cell proliferation assays were performed as described above in a rescue experiment with hsa-miR-130a-3p mimics.The interaction of hsa_circRNA_102610 and hsa-miR-130a-3p was verified by fluorescence in situ hybridization and dual luciferase reporter assays.The relative expression levels of CyclinD1,mothers against decapentaplegic homolog 4(SMAD4),E-cadherin,N-cadherin and Vimentin were detected by western blotting following hsa_circRNA_102610 overexpression,TGF-β1-induced EMT or hsa-miR-130a-3p mimic transfection(in rescue experiments).RESULTS Upregulation of hsa_circRNA_102610 was determined to be positively correlated with elevated fecal calprotectin levels in CD(r=0.359,P=0.007)by Pearson correlation analysis.Hsa_circRNA_102610 promoted the proliferation of HIECs and NCM460 cells,while hsa-miR-130a-3p reversed the cell proliferationpromoting effects of hsa_circRNA_102610.Fluorescence in situ hybridization and dual luciferase reporter assays showed that hsa_circRNA_102610 directly bound hsa-miR-130a-3p in NCM460 and 293T cells.An inverse correlation between downregulation of hsa-miR-130a-3p and upregulation of hsa_circRNA_102610 in CD patients was observed(r=-0.290,P=0.024)by Pearson correlation analysis.Moreover,overexpression of hsa_circRNA_102610 promoted SMAD4 and CyclinD1 protein expression validated by western-blotting.Furthermore,overexpression of hsa_circRNA_102610 promoted TGF-β1 induced EMT in HIECs and NCM460 cells via targeting of hsa-miR-130a-3p,with increased expression of Vimentin and N-cadherin and decreased expression of E-cadherin.CONCLUSION Hsa_circRNA_102610 upregulation in CD patients could promote the proliferation and EMT of intestinal epithelial cells via sponging of hsa-miR-130a-3p.