Expression of μ-protocadherin is negatively regulated by the activation of the β-catenin signaling pathway in normal and cancer colorectal enterocytes

Wnt signaling in colorectal cancer: pathogenic role and therapeutic target

Background

The Wnt signaling pathway is a complex network of protein interactions that functions most commonly in embryonic development and cancer, but is also involved in normal physiological processes in adults. The canonical Wnt signaling pathway regulates cell pluripotency and determines the differentiation fate of cells during development. The canonical Wnt signaling pathway (also known as the Wnt/β-catenin signaling pathway) is a recognized driver of colon cancer and one of the most representative signaling pathways. As a functional effector molecule of Wnt signaling, the modification and degradation of β-catenin are key events in the Wnt signaling pathway and the development and progression of colon cancer. Therefore, the Wnt signaling pathway plays an important role in the pathogenesis of diseases, especially the pathogenesis of colorectal cancer (CRC).

Objective

Inhibit the Wnt signaling pathway to explore the therapeutic targets of colorectal cancer.

Methods

Based on studying the Wnt pathway, master the biochemical processes related to the Wnt pathway, and analyze the relevant targets when drugs or inhibitors act on the Wnt pathway, to clarify the medication ideas of drugs or inhibitors for the treatment of diseases, especially colorectal cancer.

Results

Wnt signaling pathways include: Wnt/β-catenin or canonical Wnt signaling pathway, planar cell polarity (Wnt-PCP) pathway and Wnt-Ca²⁺ signaling pathway. The Wnt signaling pathway is closely related to cancer cell proliferation, stemness, apoptosis, autophagy, metabolism, inflammation and immunization, microenvironment, resistance, ion channel, heterogeneity, EMT/migration/invasion/metastasis. Drugs/phytochemicals and molecular preparations for the Wnt pathway of CRC treatment have now been developed. Wnt inhibitors are also commonly used clinically for the treatment of CRC.

Conclusion

The development of drugs/phytochemicals and molecular inhibitors targeting the Wnt pathway can effectively treat colorectal cancer clinically.

Mesalazine initiates an anti-oncogenic β-catenin / MUCDHL negative feed-back loop in colon cancer cells by cell-specific mechanisms

Chronic inflammation associated with intestinal architecture and barrier disruption puts patients with inflammatory bowel disease (IBD) at increased risk of developing colorectal cancer (CRC). Widely used to reduce flares of intestinal inflammation, 5-aminosalicylic acid derivatives (5-ASAs) such as mesalazine appear to also exert more direct mucosal healing and chemopreventive activities against CRC. The mechanisms underlying these activities are poorly understood and may involve the up-regulation of the cadherin-related gene MUCDHL (CDHR5). This atypical cadherin is emerging as a new actor of intestinal homeostasis and opposes colon tumorigenesis. Here, we showed that mesalazine increase mRNA levels of MUCDHL and of other genes involved in the intestinal barrier function in most intestinal cell lines. In addition, using gain / loss of function experiments (agonists, plasmid or siRNAs transfections), luciferase reporter genes and chromatin immunoprecipitation, we thoroughly investigated the molecular mechanisms triggered by mesalazine that lead to the up-regulation of MUCDHL expression. We found that basal transcription of MUCDHL in different CRC cell lines is regulated positively by CDX2 and negatively by β-catenin through a negative feed-back loop. However, mesalazine-stimulation of MUCDHL transcription is controlled by cell-specific mechanisms, involving either enhanced activation of CDX2 and PPAR-γ or repression of the β-catenin inhibitory effect. This work highlights the importance of the cellular and molecular context in the activity of mesalazine and suggests that its efficacy against CRC depends on the genetic alterations of transformed cells.

The atypical cadherin MUCDHL antagonizes colon cancer formation and inhibits oncogenic signaling through multiple mechanisms

Cadherins form a large and pleiotropic superfamily of membranous proteins sharing Ca²⁺-binding repeats. While the importance of classic cadherins such as E- or N-cadherin for tumorigenesis is acknowledged, there is much less information about other cadherins that are merely considered as tissue-specific adhesion molecules. Here, we focused on the atypical cadherin MUCDHL that stood out for its unusual features and unique function in the gut. Analyses of transcriptomic data sets (n > 250) established that MUCDHL mRNA levels are down-regulated in colorectal tumors. Importantly, the decrease of MUCDHL expression is more pronounced in the worst-prognosis subset of tumors and is associated with decreased survival. Molecular characterization of the tumors indicated a negative correlation with proliferation-related processes (e.g., nucleic acid metabolism, DNA replication). Functional genomic studies showed that the loss of MUCDHL enhanced tumor incidence and burden in intestinal tumor-prone mice. Extensive structure/function analyses revealed that the mode of action of MUCDHL goes beyond membrane sequestration of ß-catenin and targets through its extracellular domain key oncogenic signaling pathways (e.g., EGFR, AKT). Beyond MUCDHL, this study illustrates how the loss of a gene critical for the morphological and functional features of mature cells contributes to tumorigenesis by dysregulating oncogenic pathways.

Cadherins down-regulation: towards a better understanding of their relevance in colorectal cancer

The down-regulation of cadherin expression in colorectal cancer (CRC) has been widely studied. However, existing data on cadherin expression are highly variable and its relevance to CRC development has not been completely established. This review examines published studies on cadherins whose down-regulation has been already demonstrated in CRC, trying to establish a relationship with promoter methylation, the capacity to influence the Wnt / CTNNB1 (catenin beta 1, beta-catenin) signalling pathway and the clinical implications for disease outcome. Moreover, it also analyses factors that may explain data variability and highlights the importance of considering the altered subcellular localization of the examined cadherins. The results of this survey reveal that thirty of one hundred existing cadherins appear to be down-regulated in CRC. Among these, ten are cadherins, sixteen are protocadherins, equally divided between clustered and non clustered, and four are cadherin - related. These findings suggest that, to better define the role played by cadherin down-regulation in CRC pathogenesis, the expression of multiple rather than individual cadherins should be taken into account and further functional studies are necessary to clarify the relative ability of individual cadherins to inhibit CTNNB1 therefore acting as tumor suppressors.

CDHR5 inhibits proliferation of hepatocellular carcinoma and predicts clinical prognosis

BACKGROUND

As one of the most prevalent malignancies, hepatocellular carcinoma (HCC) ranks the third leading cause of cancer death worldwide. Due to the lack of biomarkers for early diagnosis, the clinical outcome of HCC remains unsatisfied with the current common therapeutic approaches, including surgery and chemotherapies. Thus, sensitive biomarkers and targeted therapies are in great need.

AIMS

In this study, we explored and verified whether CDHR5 (cadherin-related family member 5), a cadherin family protein, could serve as the potential biomarkers for HCC in the clinic.

METHODS

A retrospective study which contained 154 HCC patients was performed. Chi-square was utilized to analyze the relationship between CDHR5 expression and the clinicopathological features of HCC patients. The Kaplan-Meier method and Cox regression analyses were then used to evaluate the survival of HCC patients. In addition, cell proliferation assay and colony formation assay were performed to examine the effects of CDHR5 on the progression of HepG2 and Huh7 cells.

RESULTS

IHC and RT-qPCR revealed that CDHR5 was downregulated in HCC tissues compared with adjacent liver tissues. In addition, CDHR5 expression was significantly correlated with tumor numbers, tumor size, and TNM stage. CDHR5 expression was then shown to be an independent risk factor for survival of HCC patients by survival analysis. In vitro experiments showed that CDHR5 suppressed the proliferation capacity of HCC cells.

CONCLUSIONS

Taken together, our study not only identified CDHR5 as a novel prognostic biomarker in HCC but also provided evidence that CDHR5 can inhibit HCC cell proliferation.

miR-640 aggravates intervertebral disc degeneration via NF-κB and WNT signalling pathway

OBJECTIVES

Low back pain becomes a common orthopaedic disease today. It is mainly induced by the degeneration of the intervertebral disc. In this study, we tried to reveal the pathogenesis of the degeneration and the relative therapeutic strategy, which are still elusive.

MATERIALS AND METHODS

We collected 15 degenerative intervertebral tissues and five healthy donors. Nucleus pulposus and annulus fibrosus cells were subcultured. miR-640 expression was determined by qPCR. Computer analysis and luciferase reporter assay were used to confirm miR-640 target genes. Immunohistochemical and immunocytochemical staining was used to trace the proinflammatory cytokines and key transductor of signalling pathways. We also used β-galactosidase staining, flow cytometry, and cell viability assay to monitor the degenerative index.

RESULTS

miR-640 overexpressed in patients derived degenerative nucleus pulposus tissues and cells. The inflammatory environment promoted miR-640 expression via NF-κB signalling pathway. In addition, miR-640 targeted to LRP1 and enhances NF-κB signal activity, which built a positive feedback loop. miR-640 inhibited the expression of β-catenin and EP300, therefore, restrained WNT signal and induced the degeneration in nucleus pulposus cells. miR-640 inhibitor treatment exhibited the effects of anti-inflammation, reverse WNT signalling pathway exhaustion, and remission of degenerative characteristics in vitro.

CONCLUSIONS

miR-640 plays an important role in the degeneration of intervertebral disc and the relative inflammatory microenvironment. It is a promising potential therapeutic target for the low back pain biotherapy.

Physiological expression of miR-130a during differentiation of CD34+ human hematopoietic stem cells results in the inhibition of monocyte differentiation

MicroRNAs (miRNA) are small noncoding RNAs that regulate gene expression by targeting mRNAs in a sequence specific manner, thereby determining their degradation or inhibiting translation. They are involved in processes such as proliferation, differentiation and apoptosis by fine-tuning the expression of genes underlying such events. The expression of specific miRNAs is involved in hematopoietic differentiation and their deregulation contributes to the development of hematopoietic malignancies such as acute myeloid leukemia (AML). miR-130a is over-expressed in AML. Here we show that miR-130a is physiologically expressed in myeloblasts and down-regulated during monocyte differentiation. Gain- and loss-of-function experiments performed on CD34⁺ human hematopoietic stem cells confirmed that expression of miR-130a inhibits monocyte differentiation by interfering with the expression of key transcription factors HOXA10, IRF8, KLF4, MAFB and PU-1. The data obtained in this study highlight that the correct modulation of miR-130a is necessary for normal differentiation to occur and confirming that deregulation of this miRNA might underlie the differentiation block occurring in AML.

The H2A.Z histone variant integrates Wnt signaling in intestinal epithelial homeostasis

The Tip60/p400 chromatin-modifying complex, which is involved in the incorporation and post-translational modification of the H2A.Z histone variant, regulates cell proliferation and important signaling pathways, such as Wnt. Here, we study the involvement of H2A.Z in intestinal epithelial homeostasis, which is dependent on the finely-tuned equilibrium between stem cells renewal and differentiation, under the control of such pathway. We use cell models and inducible knock-out mice to study the impact of H2A.Z depletion on intestinal homeostasis. We show that H2A.Z is essential for the proliferation of human cancer and normal intestinal crypt cells and negatively controls the expression of a subset of differentiation markers, in cultured cells and mice. H2A.Z impairs the recruitment of the intestine-specific transcription factor CDX2 to chromatin, is itself a target of the Wnt pathway and thus, acts as an integrator for Wnt signaling in the control of intestinal epithelial cell fate and homeostasis.

The histone variant, H2A.Z is known to regulate gene expression and cell proliferation. Here the authors show that H2A.Z has a central role in the control of intestinal epithelial homeostasis in mice, by preventing terminal differentiation of intestinal progenitors.

Loss of expression of μ-protocadherin and protocadherin-24 in sporadic and hereditary nonpolyposis colorectal cancers

Colorectal cancer (CRC) is a neoplastic disease in which normal mucosa undergoes a process of malignant transformation due to the progressive accumulation of molecular alterations affecting proto-oncogenes and oncosuppressor genes. Some of these modifications exert their carcinogenic potential by promoting a constitutive activation of the β-catenin signaling proliferation pathway, and when present, loss of cadherin expression also significantly contributes to the same effect. Using a combined approach of molecular and immunohistochemical analysis, we have previously demonstrated that most sporadic CRCs exhibit a down-regulated expression of a cadherin, named μ-protocadherin, that is generally observed in association with a higher proliferation rate and a worse prognosis. The aim of this report was to perform a comparative immunohistochemical assessment of μ-protocadherin and a similar cadherin, named protocadherin-24, in sporadic CRC and hereditary nonpolyposis colorectal cancer. The data obtained put in evidence that double-negative CRCs, lacking both the analyzed protocadherins, are more represented among sporadic tumors, whereas double-positive CRCs, maintaining their expression, exhibit an opposite trend. As expected, loss of protocadherin expression was accompanied by nuclear localization of β-catenin and increased positivity of the Ki-67 proliferation marker. This finding is consistent with the different clinical evolution of the 2 considered CRC sets according to which patients with hereditary nonpolyposis colorectal cancer experience a better prognosis as compared with those affected by a sporadic CRC.

KLF4 Mediates the Effect of 5-ASA on the β-Catenin Pathway in Colon Cancer Cells

Mesalazine (5-ASA) is an aminosalicylate anti-inflammatory drug capable of inducing μ-protocadherin, a protein expressed by colorectal epithelial cells that is downregulated upon malignant transformation. Treatment with 5-ASA restores μ-protocadherin expression and promotes the sequestration of β-catenin to the plasma membrane. Here, we show that 5-ASA-induced μ-protocadherin expression is directly regulated by the KLF4 transcription factor. In addition, we suggest the existence of a dual mechanism whereby 5-ASA-mediated β-catenin inhibition is caused by μ-protocadherin-dependent sequestration of β-catenin to the plasma membrane and by the direct binding of KLF4 to β-catenin. In addition, we found that 5-ASA treatment suppresses the expression of miR-130a and miR-135b, which target KLF4 mRNA, raising the possibility that this mechanism is involved in the increased expression of KLF4 induced by 5-ASA. Cancer Prev Res; 11(8); 503-10. ©2018 AACR.