Development Of Human Colorectal Cancer Research Articles

Different Roles of Apoptosis and Autophagy in the Development of Human Colorectal Cancer.

Colorectal cancer (CRC) remains a major life-threatening malignancy, despite numerous therapeutic and screening attempts. Apoptosis and autophagy are two processes that share common signaling pathways, are linked by functional relationships and have similar protein components. During the development of cancer, the two processes can trigger simultaneously in the same cell, causing, in some cases, an inhibition of autophagy by apoptosis or apoptosis by autophagy. Malignant cells that have accumulated genetic alterations can take advantage of any alterations in the apoptotic process and as a result, progress easily in the cancerous transformation. Autophagy often plays a suppressive role during the initial stages of carcinogenicity, while in the later stages of cancer development it can play a promoting role. It is extremely important to determine the regulation of this duality of autophagy in the development of CRC and to identify the molecules involved, as well as the signals and the mechanisms behind it. All the reported experimental results indicate that, while the antagonistic effects of autophagy and apoptosis occur in an adverse environment characterized by deprivation of oxygen and nutrients, leading to the formation and development of CRC, the effects of promotion and collaboration usually involve an auxiliary role of autophagy compared to apoptosis. In this review, we elucidate the different roles of autophagy and apoptosis in human CRC development.

MicroRNA-31 induced by Fusobacterium nucleatum infection promotes colorectal cancer tumorigenesis

Persistent Fusobacterium nucleatum infection is associated with the development of human colorectal cancer (CRC) and promotes tumorigenicity, but the underlying mechanisms remain unclear. Here, we reported that F.nucleatum promoted the tumorigenicity of CRC, which was associated with F.nucleatum-induced microRNA-31 (miR-31) expression in CRC tissues and cells. F.nucleatum infection inhibited autophagic flux by miR-31 through inhibiting syntaxin-12 (STX12) and was associated with the increased intracellular survival of F.nucleatum. Overexpression of miR-31 in CRC cells promoted their tumorigenicity by targeting eukaryotic initiation factor 4F-binding protein 1/2 (eIF4EBP1/2), whereas miR-31 knockout mice were resistant to the formation of colorectal tumors. In conclusion, F.nucleatum, miR-31, and STX12 form a closed loop in the autophagy pathway, and continuous F.nucleatum-induced miR-31 expression promotes the tumorigenicity of CRC cells by targeting eIF4EBP1/2. These findings reveal miR-31 as a potential diagnostic biomarker and therapeutic target in CRC patients with F.nucleatum infection.

Gasdermin D represses inflammation-induced colon cancer development by regulating apoptosis.

Chronic inflammation is widely recognized as a major risk factor for cancer formation, but the underlying mechanisms are poorly understood. Recently, it was shown that Gasdermin D (GSDMD) protein drives pyroptotic cell death in macrophages on cleavage by inflammatory caspases. Even though the Gsdmd gene is specifically expressed in the intestinal epithelium, the role of Gsdmd in the intestinal tissues remains poorly characterized. In this study, we examined the biological role of Gsdmd in colorectal cancer (CRC) development, employing an azoxymethane/dextran sulfate sodium carcinogenesis model. Results show that GSDMD deficiency enhances CRC development, probably due to decreased apoptosis caused by downregulation of interferon-gamma (IFNγ)-signal transducer and activator 1 (STAT1) signaling. Furthermore, we show that GSDMD protein is diminished in human colorectal cancer, indicating involvement of GSDMD in repression of CRC development in humans. Our findings provide a new insight into functions of Gsdmd/GSDMD in colonic inflammation and human CRC development.

The EDN1/EDNRA/β‑arrestin axis promotes colorectal cancer progression by regulating STAT3 phosphorylation.

Endothelin receptor A (EDNRA) has been reported to play various crucial physiological roles and has been shown to be associated with the pathology of several diseases, including colorectal cancer (CRC). However, the molecular mechanisms of EDNRA in the development of human CRC have not been fully elucidated to date. In this context, the present study was performed to investigate biological functions and novel downstream signaling pathways affected by EDNRA, during CRC progression. First, using public data repositories, it was observed that the EDRNA expression levels were markedly increased in CRC tissues, as compared to normal tissues. Patients with CRC with an increased EDNRA expression exhibited a significantly decreased survival rate in comparison with those with a lower EDNRA expression. Furthermore, a positive correlation between the levels of EDNRA and its ligand, EDN1, was found in CRC tissues. The ectopic expression of EDNRA or its ligand, EDN1, promoted, whereas the silencing of EDNRA or EDN1 decreased cell proliferation and migration invitro. To elucidate the signaling pathways involved in the regulation of EDNRA expression in CRC cells, a phosphokinase array analysis was performed, and it was observed that the knockdown of EDNRA substantially suppressed the phosphorylation of signal transducer and activator of transcription 3 (STAT3) in CRC cells. Of note, STAT3 silencing simultaneously decreased EDN1 and EDNRA expression, with the expression of EDN1 and/or EDNRA appearing to be directly regulated by binding STAT3 to their promoter region, according to chromatin immunoprecipitation and promoter assays, ultimately indicating a positive feedback loop in the expression of EDNRA and EDN1. It was also observed that treatment with an EDNRA antagonist (macitentan), alone or in combination with cisplatin, suppressed cell growth and migration ability, and induced cell apoptosis. Collectively, these data suggest a critical role of the EDN1/EDNRA signaling pathway in CRC progression. Thus, the pharmacological intervention of this signaling pathway may prove to be a potential therapeutic approach for patients with CRC.

Transcriptomic and Proteomic Study on the High-Fat Diet Combined With AOM/DSS-Induced Adenomatous Polyps in Mice

ObjectiveTo screen and identify molecular targets and bacteria genus leading to adenomatous polyps in mouse induced by high-fat diet (HFD) +AOM/DSS using omics technology.MethodsThe molecular targets of colorectal adenoma disease were obtained from the GeneCards and OMIM database. The SPF C57BL mice were randomly divided into blank (Control) and AOM/DSS+HFD colorectal adenoma model (ADH) groups. The ADH model group was intraperitoneally injected with AOM reagent. Then, mice were given with 2.5% DSS (in free drinking water) and high-fat diet to establish the mouse model. During this period, the changes of physical signs of mice in each group were observed. After the end of modeling, HE staining was used to evaluate the histopathological change of mice. The differentially expressed genes and proteins in the Control group and ADH group were detected by RNA-seq transcriptome sequencing and Tandem Mass Tags (TMT) quantitative proteomics. The histological results were analyzed by intersection with the intestinal adenoma molecular targets obtained from the database. Moreover, the changes of intestinal flora in the two groups were examined. The correlation between targets and differential bacteria was analyzed and verified by Parallel Reaction Monitoring (PRM) to comprehensively evaluate the mouse model of adenomatous polyp induced by AOM/DSS+HFD.ResultsThe general condition and histopathological results of mice confirmed that the ADH mouse model was successfully established and tubular adenoma was formed. A total of 604 genes and 42 proteins related to intestinal adenoma were obtained by histological analysis and database intersection analysis. The intestinal microflora of ADH mice was different from that of normal mice, and the constituents and abundance of intestinal flora were similar to those of human intestinal adenoma. GATA4 and LHPP were selected as potential pathological markers of the model mice by correlation analysis of targets and intestinal flora. The results of PRM verification were highly consistent with the results of RNA-Seq transcriptome sequencing and TMT analysis.ConclusionThe pathological results, molecular pathological markers and the changes of intestinal flora suggest that the mouse ADH model is ideal for studying the transformation of inflammatory cancer. The ADH model will be helpful for understanding the occurrence and development of human colorectal cancer at the transcriptomic and proteomic level.

Identification of Hub Gene TIMP1 and Relative ceRNAs Regulatory Network in Colorectal Cancer

ObjectiveThis study aimed to discover the ceRNAs network in the pathophysiological development of human colorectal cancer (CRC) and to screen biomarkers for target therapy and prognosis by using integrated bioinformatics analysis.MethodsData on gene expressions of mRNAs, miRNAs, and circRNAs and clinical information were downloaded from The Cancer Genome Atlas and Gene Expression Omnibus databases, respectively. Differentially expressed mRNAs (DEmRNAs) were identified by using the DESeq2 package of R software. Functional enrichment analysis was conducted using the ClusterProfiler package of R software. The protein–protein interaction (PPI) network was shown by the STRING website. Survival analysis of hub genes was performed using the survival package in R software. Interactions among hub genes, differentially expressed miRNAs (DEmiRNAs), and differentially expressed circRNAs (DEcircRNAs) were used to construct the ceRNAs network.ResultsA total of 412 DEmRNAs including 82 upregulated and 330 downregulated genes were screened out between 473 CRC and 41 normal samples. Two hundred and sixty DEcircRNAs including 253 upregulated and 7 downregulated genes were altered between 23 CRC and 23 normal samples. One hundred and ninety DEmiRNAs including 82 upregulated and 108 downregulated genes were obtained between 450 CRC and 8 normal samples. A ceRNAs and PPI network were successfully constructed, and TIMP1 associated with prognosis was employed.ConclusionThe present study identified a novel circRNAs-miRNAs-mRNA ceRNAs network, which implied that TIMP1 and related miRNAs, circRNAs were potential biomarkers underlying the development of CRC, providing new insights for survival predictions and therapeutic targets.

Long noncoding RNA MALAT1 sponging miR-26a-5p to modulate Smad1 contributes to colorectal cancer progression by regulating autophagy.

Accumulating evidences have suggested that bone morphogenetic protein (BMP)-Smad have a functional role in regulating autophagy in the development of human colorectal cancer (CRC). However, the regulatory mechanisms controlling this process remain unclear. Here, we showed that Smad1, the key effector of BMP2-Smad signaling, induces autophagy by upregulating autophagy-related gene 5 (ATG5) expression, and Smad1 binds to the proximal promoter to induce its expression. Moreover, BMP2 induces autophagy in CRC. Overexpression of Smad1 promotes tumorigenesis and migration of CRC cells, and knockdown of ATG5 is able to rescue the Smad1-induced promotion of CRC proliferation and migration partially. Mechanistically, metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) may act as a competing endogenous RNA by binding with miR-26a-5p competitively and thus modulating the de-repression of downstream target Smad1. Furthermore, clinical analysis results show that Smad1 is positively correlated with MALAT1 and negatively correlated with miR-26a-5p in CRC samples. In conclusion, our results demonstrated that Smad1 may serve as an oncogene in CRC through autophagy.

Post-transcriptional suppression of G protein-coupled receptor 15 (GPR15) by microRNA-1225 inhibits proliferation, migration, and invasion of human colorectal cancer cells

The G protein-coupled receptors (GPRs) have been shown to regulate several cancer related processes. The aberrant expression of GPRs has been linked to the development of several cancers. The present study was designed to examine the expression and decipher the role of GPR15 in the development of human colorectal cancer. The results revealed GPR15 to be significantly (P < 0.05) upregulated in colorectal cancer cells. The silencing of GPR15 inhibited the growth of the colorectal cancer cells via induction of apoptosis. Induction of apoptosis in colorectal cancer cells was associated increase in Bax and decrease in Bcl-2 expression. The silencing of GPR-15 also caused a significant (P < 0.05) decline in the migration and invasion of the colorectal cancer cells. Bioinformatic analysis and luciferase assay revealed that the expression of GPR15 to be post-transcriptionally regulated by microRNA-1225 (miR-1225). The expression of miR-1225 was found to significantly (P < 0.05) downregulated in colorectal cancer cells and its overexpression caused suppression of GPR15 and inhibited the proliferation of the colorectal cancer cells. Nonetheless, overexpression of GPR15 could avoid the growth inhibitory effects of miR-1225. The results suggest that the GPR15/miR-1225 axis play an important role in the development of colon rectal cancer and exhibit therapeutic implications for its treatment.

Transcriptome profiling unveils GAP43 regulates ABC transporters and EIF2 signaling in colorectal cancer cells

BackgroundThe growth- and plasticity-associated protein-43 (GAP43) is biasedly expressed in indigestive system and nervous system. Recent study has shown that GAP43 is responsible for the development of neuronal growth and axonal regeneration in normal nervous tissue, while serves as a specific biomarker of relapsed or refractory neuroblastoma. However, its expression pattern and function in digestive system cancer remains to be clarified.MethodsIn this study, we examined the GAP43 status with qRT-PCR and bisulfite genomic sequencing in colorectal cancer (CRC). We investigated the effect of overexpressed GAP43 in CRC cells with RNA-seq. The RNA-seq data was analyzed with DAVID and IPA.ResultsGAP43 was downregulated in CRC compared to the adjacent tissues. DNA methylase inhibitor 5-Aza-CdR treatment could significantly induce GAP43, indicated that the silencing of GAP43 gene in CRC is closely related to DNA methylation. Bisulfite genomic sequencing confirmed the promoter methylation of GAP43 in CRC. To explore the transcriptional alterations by overexpressed GAP43 in CRC, we performed RNA-seq and found that upregulated genes were significantly enriched in the signaling pathways of ABC transporters and ECM-receptor interaction, while downregulated genes were significantly enriched in Ribosome signaling pathway. Further Ingenuity Pathway Analysis (IPA) showed that EIF2 signaling pathway was significantly repressed by overexpression of GAP43.ConclusionOur findings provide a novel mechanistic insight of GAP43 in CRC. Transcriptome profiling of overexpressed GAP43 in CRC uncovered the functional roles of GAP43 in the development of human CRC.

Wnt/β-catenin Signaling Inhibitors suppress the Tumor-initiating properties of a CD44+CD133+ subpopulation of Caco-2 cells

Tumor-initiating cells or cancer stem cells are a subset of cancer cells that have tumorigenic potential in human cancer. Although several markers have been proposed to distinguish tumor-initiating cells from colorectal cancer cells, little is known about how this subpopulation contributes to tumorigenesis. Here, we characterized a tumor-initiating cell subpopulation from Caco-2 colorectal cancer cells. Based on the findings that Caco-2 cell subpopulations express different cell surface markers, we were able to discriminate three main fractions, CD44-CD133-, CD44-CD133+, and CD44+CD133+ subsets, and characterized their biochemical and tumorigenic properties. Our results show that CD44+CD133+ cells possessed an unusual capacity to proliferate and could form tumors when transplanted into NSG mice. Additionally, primary tumors grown from CD44+CD133+ Caco-2 cells contained mixed populations of CD44+CD133+ and non-CD44+CD133+ Caco-2 cells, indicating that the full phenotypic heterogeneity of the parental Caco-2 cells was re-created. Notably, only the CD44+CD133+ subset of Caco-2-derived primary tumors had tumorigenic potential in NSG mice, and the tumor growth of CD44+CD133+ cells was faster in secondary xenografts than in primary transplants. Gene expression analysis revealed that the Wnt/β-catenin pathway was over-activated in CD44+CD133+ cells, and the growth and tumorigenic potential of this subpopulation were significantly suppressed by small-molecule Wnt/β-catenin signaling inhibitors. Our findings suggest that the CD44+CD133+ subpopulation from Caco-2 cells was highly enriched in tumorigenic cells and will be useful for investigating the mechanisms leading to human colorectal cancer development.

Prognostic Role of Inflammasome Components in Human Colorectal Cancer.

Simple SummaryInflammasomes are critically involved in gut epithelial homeostasis, immunosurveillance and in controlling tumorigenesis mechanisms. Data on the role of inflammasomes in tumorigenesis are mostly provided by transcriptomic analyses of bulk tumors, eluding a potential specific role of intrinsic epithelial inflammasomes. Therefore, we investigated the expression of inflammasome components in intestinal epithelial cells, at the protein level in patient tissues and assessed the correlation with clinicopathological parameters. We found that downregulation of the epithelial expression of NOD-like receptor family pyrin domain containing 6 (NLRP6) and IL-18 was associated with more advanced disease and worse patients’ outcome. Furthermore, the loss of both epithelial and stromal IL-18 was also associated with worse disease outcome. Finally, we identified an epithelial innate immune protein profile combining NLRP6 and IL-18 that stratified patients for better clinical prognosis. Together, analysis of epithelial inflammasomes may help clinical decisions for better prognostic assessment and may identify new therapeutic targets in colorectal cancer.(1) We wanted to assess the prognostic impact of inflammasomes involved in gut epithelial homeostasis and the development of human colorectal cancer (CRC). (2) We investigated the expression of inflammasome components in colonic epithelial cells at the protein level in patient tissues, through an immunofluorescence assay. (3) In a cohort of 104 patients, we found that all inflammasome components were downregulated in CRC. Loss of epithelial (but not stromal) expression of NLRP6, caspase-1 and IL-18 was associated with an increased mortality of 72%, 58% and 68% respectively and to disease progression into metastasis. The loss of epithelial and stromal IL-18 but not NLRP6, was associated to lower tumor immune infiltrates in the lymphoid compartment and higher Programmed cell Death receptor 1 (PD-1) expression. Finally, we found that combined downregulation of IL-18 and NLRP6 was associated with a worse outcome. Indeed, 5-year survival rates were 26% for the NLRP6low/IL-18low tumors, compared to 64.4% for the entire cohort. This downregulation was associated with a more advanced disease (p < 0.0001) and a trend to lower lymphoid cell infiltration. (4) We identified critical inflammasome markers that may help in better stratifying patients for prognosis in CRC and could help clinicians to determine which patients may benefit from immunotherapies.

Insulin receptor substrate 1 may play divergent roles in human colorectal cancer development and progression.

BACKGROUNDDespite effective prevention and screening methods, the incidence and mortality rates associated with colorectal cancer (CRC) are still high. Insulin receptor substrate 1 (IRS-1), a signaling molecule involved in cell proliferation, survival and metabolic responses has been implicated in carcinogenic processes in various cellular and animal models. However, the role of IRS-1 in CRC biology and its value as a clinical CRC biomarker has not been well defined.AIMTo evaluate if and how IRS-1 expression and its associations with the apoptotic and proliferation tumor markers, Bax, Bcl-xL and Ki-67 are related to clinicopathological features in human CRC.METHODSThe expression of IRS-1, Bax, Bcl-xL and Ki-67 proteins was assessed in tissue samples obtained from 127 patients with primary CRC using immunohistochemical methods. The assays were performed using specific antibodies against IRS-1, Bax, Bcl-xL, Ki-67. The associations between the expression of IRS-1, Bax, Bcl-xL, Ki-67 were analyzed in relation to clinicopathological parameters, i.e., patient age, sex, primary localization of tumor, histopathological type, grading, staging and lymph node spread. Correlations between variables were examined by Spearman rank correlation test and Fisher exact test with a level of significance at P < 0.05.RESULTSImmunohistochemical analysis of 127 CRC tissue samples revealed weak cytoplasmatic staining for IRS-1 in 66 CRC sections and strong cytoplasmatic staining in 61 cases. IRS-1 expression at any level in primary CRC was associated with tumor grade (69% in moderately differentiated tumors, G2 vs 31% in poorly differentiated tumors, G3) and with histological type (81.9% in adenocarcinoma vs 18.1% in adenocarcinoma with mucosal component cases). Strong IRS-1 positivity was observed more frequently in adenocarcinoma cases (95.1%) and in moderately differentiated tumors (85.2%). We also found statistically significant correlations between expression of IRS-1 and both Bax and Bcl-xL in all CRC cases examined. The relationships between studied proteins were related to clinicopathological parameters of CRC. No significant correlation between the expression of IRS-1 and proliferation marker Ki-67, excluding early stage tumors, where the correlation was positive and on a high level (P = 0.043, r = 0.723).CONCLUSIONThis study suggests that IRS-1 is co-expressed with both pro- and antiapoptotic markers and all these proteins are more prevalent in more differentiated CRC than in poorly differentiated CRC.

Zeb2 drives invasive and microbiota-dependent colon carcinoma.

Colorectal cancer (CRC) is highly prevalent in Western society, and increasing evidence indicates strong contributions of environmental factors and the intestinal microbiota to CRC initiation, progression and even metastasis. We have identified a synergistic inflammatory tumor-promoting mechanism through which the resident intestinal microbiota boosts invasive CRC development in an epithelial-to-mesenchymal transition-prone tissue environment. Intestinal epithelial cell (IEC)-specific transgenic expression of the epithelial-to-mesenchymal transition regulator Zeb2 in mice (Zeb2IEC-Tg/+) leads to increased intestinal permeability, myeloid cell-driven inflammation and spontaneous invasive CRC development. Zeb2IEC-Tg/+ mice develop a dysplastic colonic epithelium, which progresses to severely inflamed neoplastic lesions while the small intestinal epithelium remains normal. Zeb2IEC-Tg/+ mice are characterized by intestinal dysbiosis, and microbiota depletion with broad-spectrum antibiotics or germ-free rederivation completely prevents cancer development. Zeb2IEC-Tg/+ mice represent the first mouse model of spontaneous microbiota-dependent invasive CRC and will help us to better understand host-microbiome interactions driving CRC development in humans.

Significance of the gut microbiome in multistep colorectal carcinogenesis.

Colorectal cancer (CRC) is highly prevalent worldwide. In 2018, there were over 1.8 million new cases. Most sporadic CRC develop from polypoid adenomas and are preceded by intramucosal carcinoma (stage 0), which can progress into more malignant forms. This developmental process is known as the adenoma‐carcinoma sequence. Early detection and endoscopic removal are crucial for CRC management. Accumulating evidence suggests that the gut microbiota is associated with CRC development in humans. Comprehensive characterization of this microbiota is of great importance to assess its potential as a diagnostic marker in the very early stages of CRC. In this review, we summarized recent studies on CRC‐associated bacteria and their carcinogenic mechanisms in animal models, human cell lines and human cohorts. High‐throughput technologies have facilitated the identification of CRC‐associated bacteria in human samples. We have presented our metagenome and metabolome studies on fecal samples collected from a large Japanese cohort that revealed stage‐specific phenotypes of the microbiota in CRC. Furthermore, we have discussed the potential carcinogenic mechanisms of the gut microbiota, from which we can infer whether changes in the gut microbiota are a cause or effect in the multi‐step process of CRC carcinogenesis.

TH9, TH17, and TH22 Cell Subsets and Their Main Cytokine Products in the Pathogenesis of Colorectal Cancer.

In recent years, several newly identified T helper (TH) cell subsets, such as TH9, TH17, and TH22 cells, and their respective cytokine products, IL-9, IL-17, and IL-22, have been reported to play critical roles in the development of chronic inflammation in the colorectum. Since chronic inflammation is a potent driving force for the development of human colorectal cancer (CRC), the contributions of TH9/IL-9, TH17/IL-17, and TH22/IL-22 in the pathogenesis of CRC have recently become an increasingly popular area of scientific investigation. Extensive laboratory and clinical evidence suggests a positive relationship between these new TH subsets and the growth and formation of CRC, whereas, administration of IL-9, IL-17, and IL-22 signaling inhibitors can significantly alter the formation of colorectal chronic inflammation or CRC lesions in animal models, suggesting that blocking these cytokine signals might represent promising immunotherapeutic strategies. This review summarizes recent findings and currently available data for understanding the vital role and therapeutic significance of TH9/IL-9, TH17/IL-17, and TH22/IL-22 in the development of colorectal tumorigenesis.

Autophagy Keeps the Balance in Tissue Homeostasis

Gut cells are exposed to diverse insults that necessitate their replacement from a stem cell pool balancing differentiation and proliferation. In this issue of Developmental Cell, Zhang and colleagues (2019) show autophagy-mediated regulation of EGFR signaling cell autonomously controls intestinal stem cell proliferation, with implications for human colorectal cancer development.

Overexpression of the cohesin-core subunit SMC1A contributes to colorectal cancer development

BackgroundCancer cells are characterized by chromosomal instability (CIN) and it is thought that errors in pathways involved in faithful chromosome segregation play a pivotal role in the genesis of CIN. Cohesin forms a large protein ring that binds DNA strands by encircling them. In addition to this central role in chromosome segregation, cohesin is also needed for DNA repair, gene transcription regulation and chromatin architecture. Though mutations in both cohesin and cohesin-regulator genes have been identified in many human cancers, the contribution of cohesin to cancer development is still under debate.MethodsNormal mucosa, early adenoma, and carcinoma samples deriving from 16 subjects affected by colorectal cancer (CRC) were analyzed by OncoScan for scoring both chromosome gains and losses (CNVs) and loss of heterozygosity (LOH). Then the expression of SMC1A was analyzed by immunochemistry in 66 subjects affected by CRC. The effects of SMC1A overexpression and mutated SMC1A were analyzed in vivo using immunocompromised mouse models. Finally, we measured global gene expression profiles in induced-tumors by RNA-seq.ResultsHere we showed that SMC1A cohesin core gene was present as extra-copies, mutated, and overexpressed in human colorectal carcinomas. We then demonstrated that cohesin overexpression led to the development of aggressive cancers in immunocompromised mice through gene expression dysregulation.ConclusionCollectively, these results support a role of defective cohesin in the development of human colorectal cancer.

Msx1 loss suppresses formation of the ectopic crypts developed in the Apc-deficient small intestinal epithelium

The first step in the development of human colorectal cancer is aberrant activation of the Wnt signaling pathway. Wnt signaling hyperactivation is predominantly caused by loss-of-function mutations in the adenomatous polyposis coli (APC) gene that encodes the pathway negative regulator. In order to identify genes affected by the Apc loss, we performed expression profiling of intestinal epithelium isolated from mice harboring a conditional Apc allele. The gene encoding transcriptional factor msh homeobox 1 (Msx1) displayed robust upregulation upon Apc inactivation. Histological analysis of the Apc-deficient epithelium revealed that in the small intestine, the Msx1 protein was localized exclusively in ectopic crypts, i.e., in pockets of proliferating cells abnormally positioned on the villi. Ablation of the Msx1 gene leads to the disappearance of ectopic crypts and loss of differentiated cells. Moreover, tumors arising from Msx1-deficient cells display altered morphology reminiscent of villous adenomas. In human tumor specimens, MSX1 displayed significantly increased expression in colonic neoplasia with a descending tendency during the lesion progression towards colorectal carcinoma. In summary, the results indicate that Msx1 represents a novel marker of intestinal tumorigenesis. In addition, we described the previously unknown relationship between the Msx1-dependent formation of ectopic crypts and cell differentiation.

Down-regulation of lncTCF7 inhibits cell migration and invasion in colorectal cancer via inhibiting TCF7 expression.

The prognosis of colorectal cancer (CRC) is still very poor, owing to the high incidence of metastasis. Long noncoding RNA TCF7 (lncTCF7) has been shown to play critical roles in human CRC development and progression, but the molecular mechanisms of lncTCF7 in CRC are still unknown. This study aimed to explore the functions and molecular mechanisms of lncTCF7 on the migration and invasion of CRC cells. Notably, lncTCF7 was highly expressed in CRC cell lines relative to normal colonic epithelial cells. LncTCF7 knockdown significantly inhibited migration and invasion of CRC cells. In addition, TCF7 was highly expressed in CRC cell lines relative to that in normal colonic epithelial cells and its expression was significantly decreased in CRC cells transfected with si-lncTCF7. RNA immunoprecipitation, chromatin immunoprecipitation, and luciferase reporter assays showed that LncTCF7 recruits BAF170 to activate the TCF7 promoter and regulate TCF7 expression. TCF7 overexpression could promote migration and invasion in CRC cells transfected with si-lncTCF7, which reversed the effect of lncTCF7 on the migration and invasion of CRC cells. In conclusion, our data indicate that the downregulation of lncTCF7 significantly inhibits migration and invasion of CRC cells by inhibiting TCF7 expression, suggesting that lncTCF7 may be a potential target for CRC therapy.

Dietary HNE and other lipid oxidation products in the development of colorectal carcinogenesis

Based on epidemiological studies and meta-analyses, the World Cancer Research Fund (WCRF) panel stated that red meat is a convincing cause of colorectal cancer. Recently, the IARC/WHO classified red meat consumption as “probably carcinogenic to humans” (Group 2A). Red meat contains high concentrations of heme iron that induces lipid peroxidation in the colon lumen and the subsequent formation of secondary lipid oxidation products such as 4-hydroxynonenal (HNE). HNE was found in foodstuffs in relatively high concentration, particularly in meat and processed meat. Moreover, HNE formation possibly occurs in the digestive tract when rats receive heme iron and a PUFA-rich oil at the same time. In vivo studies in rats show that the development of preneoplastic lesions is well correlated with heme-iron and HNE content of the diet, and also with the urinary excretion of the major metabolite of HNE, the mercapturic acid of 1,4-dihydroxynonene (DHN-MA). Secondary oxidation products of PUFA, and especially HNE, could be one of the missing links between heme iron, enhanced luminal lipid peroxidation and colon cancer development. In vitro studies in mouse epithelial colon immortalized cells show that the cells mutated on the Apc (Adenomatous polyposis coli) gene, an early and frequent mutation during the development of human colorectal cancer, were more resistant to HNE than non-mutated cells. This resistance is due to a better metabolization capacity of those cells towards HNE. The enzymes involved are under the transcriptional control of Nrf2/antioxidant responsive element (ARE) pathway, a pathway that is upregulated in Apc mutated cells. Nrf2 natural inducers, as curcumin, have a protective effect both in vitro and in vivo.