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Background & Aims The circadian clock is crucial for physiological homeostasis including gut homeostasis. Disorder of the circadian clock may contribute to many diseases including inflammatory bowel disease (IBD). However, the role and the mechanisms of circadian clock involvement in IBD still are unclear. Methods Disorder of the circadian clock including chronic social jet lag and circadian clock gene deficiency mice ( Bmal1 -/- , and Per1 -/- Per2 -/- ) were established. Dextran sulfate sodium (DSS) and/or azoxymethane were used to induce mouse models of colitis and its associated colorectal cancer. Flow cytometry, immunohistochemistry, immunofluorescence, Western blot, and reverse-transcription quantitative polymerase chain reaction were used to analyze the characteristics of immune cells and their related molecules. Results Mice with disorders of the circadian clock including chronic social jet lag and circadian clock gene deficiency were susceptible to colitis. Functionally, regulatory B (Breg) cells highly expressing Programmed cell death 1 ligand 1 (PDL1) in intestinal intraepithelial lymphocytes (IELs) helped to alleviate the severity of colitis after DSS treatment and was dysregulated in DSS-treated Bmal1 -/- mice. Notably, interleukin 33 in the intestinal microenvironment was key for Bmal1-regulated PDL1 + Breg cells and interleukin 33 was a target of Bmal1 transcriptionally. Dysregulated PDL1 + B cells induced cell death of activated CD4 + T cells in DSS-treated Bmal1 -/- mice. Consequently, circadian clock disorder was characterized as decreased numbers of Breg + PDL1 + cells in IELs and dysfunction of CD4 + T cells promoted colitis-associated colorectal cancer (CRC) in mice. In clinical samples from CRC patients, low expression of Bmal1 gene in paracancerous tissues and center area of tumor was associated closely with a poorer prognosis of CRC patients. Conclusions Our study uncovers the importance of the circadian clock regulating PDL1 + Breg + cells of IELs in IBD and IBD-associated CRC.

In our search for bioactive mushrooms native to British Columbia, we determined that the ethanol extracts from fruiting bodies of the terrestrial polypore Albatrellus flettii had potent anti-cell viability activity. Using bioassay-guided fractionation, mass spectrometry and nuclear magnetic resonance, we successfully isolated three known compounds (grifolin, neogrifolin and confluentin). These compounds represent the major anti-cell viability components from the ethanol extracts of A. flettii. We also identified a novel biological activity for these compounds, specifically in down-regulating KRAS expression in two human colon cancer cell lines. Relatively little is known about the anti-cell viability activity and mechanism of action of confluentin. For the first time, we show the ability of confluentin to induce apoptosis and arrest the cell cycle at the G2/M phase in SW480 human colon cancer cells. The oncogenic insulin-like growth factor 2 mRNA-binding protein 1 (IMP1) has been previously shown to regulate KRAS mRNA expression in colon cancer cells, possibly through its ability to bind to the KRAS transcript. Using a fluorescence polarization assay, we show that confluentin dose-dependently inhibits the physical interaction between KRAS RNA and full-length IMP1. The inhibition also occurs with truncated IMP1 containing the KH1 to KH4 domain (KH1to4 IMP1), but not with the di-domain KH3 and KH4 (KH3&4 IMP1). In addition, unlike the control antibiotic neomycin, grifolin, neogrifolin and confluentin do not bind to KRAS RNA. These results suggest that confluentin inhibits IMP1-KRAS RNA interaction by binding to the KH1&2 di-domains of IMP1. Since the molecular interaction between IMP1 and its target RNAs is a prerequisite for the oncogenic function of IMP1, confluentin should be further explored as a potential inhibitor of IMP1 in vivo.

The pathogenesis and key functional molecules involved in inflammatory bowel disease (IBD) including Crohn's disease (CD) and ulcerative colitis (UC) remain unclear. Here, we reported that Erbin, a protein required for the polarity of epithelial cells, is conserved across species and highly expressed in the intestinal mucosa in mice and zebrafish. Pathologically, Erbin expression in the intestinal mucosa was significantly decreased in DSS induced acute colitis mice, IL-10 deficient mice and clinical biopsy specimens from patients with ulcerative colitis. Moreover, Erbin deficient mice are more susceptible to experimental colitis, exhibiting more severe intestinal barrier disruption, with increased histological scores and excessive production of proinflammatory cytokines. Mechanistically, Erbin deficiency or knockdown significantly exacerbated activation of autophagic program and autophagic cell death in vivo and in vitro. And, inhibition of autophagy by Chloroquine attenuates excessive inflammatory response in the DSS-induced colitis mouse model of Erbin deletion. Generally, our study uncovers a crucial role of Erbin in autophagic cell death and IBD, giving rise to a new strategy for IBD therapy by inhibiting excessive activation of autophagy and autophagic cell death.

The stabilization of glioma-associated oncogene 1 (GLI1) mRNA by coding region determinant binding protein (CRD-BP) through the Wnt/b-catenin signaling pathway is implicated in the proliferation of colorectal cancer and basal cell carcinoma. Here, we set out to characterize the physical interaction between CRD-BP and GLI1 mRNA so as to find inhibitors for such interaction. Studies using CRD-BP variants with a point mutation in the GXXG motif at each KH domain showed that KH1 and KH2 domain are critical for the binding of GLI1 RNA. The smallest region of GLI1 RNA binding to CRD-BP was mapped to nucleotides (nts) 320-380. A 37-nt S1 RNA sense oligonucleotide, containing two distinct stem-loops present in nts 320-380 of GLI1 RNA, was found to be effective in blocking CRD-BP-GLI1 RNA interaction. Studies using various competitor RNAs with modifications to S1 RNA oligonucleotide further displayed that both the sequences and the structure of the two stem-loops are important for CRD-BP-GLI1 RNA binding. The role of the two-stem-loop motif in influencing CRD-BP-RNA interaction was further investigated in cells. The 29-O-methyl derivative of the S1 RNA oligonucleotide significantly decreased GLI1, c-myc, and CD44 mRNA levels, in a panel of colon and breast cancer cells. The results from this study demonstrate the potential importance of the two-stem-loop motif as a target region for the inhibition of the CRD-BP-GLI1 RNA interaction and Hedgehog signaling pathway. Such results pave the way for the development of novel inhibitors that act by destabilizing the CRD-BP-GLI1 mRNA interaction.