Krüpple-like factor 5 is required for proper maintenance of adult intestinal crypt cellular proliferation

Krüppel-like Factors 4 and 5 in Colorectal Tumorigenesis

Krüppel-like factors (KLFs) are transcription factors regulating various biological processes such as proliferation, differentiation, migration, invasion, and homeostasis. Importantly, they participate in disease development and progression. KLFs are expressed in multiple tissues, and their role is tissue- and context-dependent. KLF4 and KLF5 are two fascinating members of this family that regulate crucial stages of cellular identity from embryogenesis through differentiation and, finally, during tumorigenesis. They maintain homeostasis of various tissues and regulate inflammation, response to injury, regeneration, and development and progression of multiple cancers such as colorectal, breast, ovarian, pancreatic, lung, and prostate, to name a few. Recent studies broaden our understanding of their function and demonstrate their opposing roles in regulating gene expression, cellular function, and tumorigenesis. This review will focus on the roles KLF4 and KLF5 play in colorectal cancer. Understanding the context-dependent functions of KLF4 and KLF5 and the mechanisms through which they exert their effects will be extremely helpful in developing targeted cancer therapy.

Genome-Wide Analysis of Long Noncoding RNAs in Porcine Intestine during Weaning Stress

Long noncoding RNAs (lncRNAs) play crucial roles in various biological processes, and they are considered to be closely associated with the pathogenesis of intestinal diseases. However, the role and expression of lncRNAs in intestinal damage during weaning stress remain unknown. Herein, we investigated the expression profiles of jejunal tissue from weaning piglets at 4 and 7 d after weaning (groups W4 and W7, respectively) and from suckling piglets on the same days (groups S4 and S7, respectively). Genome-wide analysis of lncRNAs was also performed using RNA sequencing technology. A total of 1809 annotated lncRNAs and 1612 novel lncRNAs were obtained from the jejunum of piglets. In W4 vs. S4, a total of 331 lncRNAs showed significant differential expression, and a total of 163 significantly differentially expressed lncRNAs (DElncRNAs) was identified in W7 vs. S7. Biological analysis indicated that DElncRNAs were involved in intestinal diseases, inflammation, and immune functions, and were mainly enriched in the Jak-STAT signaling pathway, inflammatory bowel disease, T cell receptor signaling pathway, B cell receptor signaling pathway and intestinal immune network for IgA production. Moreover, we found that lnc_000884 and target gene KLF5 were significantly upregulated in the intestine of weaning piglets. The overexpression of lnc_000884 also significantly promoted the proliferation and depressed apoptosis of IPEC-J2 cells. This result suggested that lnc_000884 may contribute to repairing intestinal damage. Our study identified the characterization and expression profile of lncRNAs in the small intestine of weaning piglets and provided new insights into the molecular regulation of intestinal damage during weaning stress.

miRNA-576 Alleviates the Malignant Progression of Atherosclerosis through Downregulating KLF5

Objective

To elucidate the role of microRNA-576 (miRNA-576) in alleviating the deterioration of atherosclerosis (AS) through downregulating krüpple-like factor 5 (KLF5).

Materials and Methods

The AS model in mice was first constructed. Body weight, inflammation degrees, blood lipid, and relative levels of KLF5, miRNA-576, caspase-3, and bcl-2 in AS mice and control mice were compared. Dual-luciferase reporter gene assay was performed to evaluate the binding between miRNA-576 and KLF5. RAW264.7 cells were treated with 200 mg/L ox-LDL for establishing in vitro high-fat model. Regulatory effects of miRNA-576/KLF5 on relative levels of β-catenin and inflammatory factors in RAW264.7 cells were explored.

Results

Body weight was heavier in AS mice than in controls. Protein levels of KLF5 and caspase-3 were upregulated, while bcl-2 was downregulated in AS mice. In particular, protein level of KLF5 was highly expressed in aortic tissues of AS mice. TC and LDL increased, and HDL decreased in AS mice compared with controls. Inflammatory factor levels were markedly elevated in AS mice. KLF5 was verified to be the target gene binding miRNA-576. Overexpression of miRNA-576 downregulated KLF5, inflammatory factors, and β-catenin in ox-LDL-treated RAW264.7 cells. Regulatory effect of miRNA-576 on the release of inflammatory factors in RAW264.7 cells could be partially abolished by KLF5.

Conclusions

miRNA-576 alleviates malignant progression of AS via downregulating KLF5.

Lactobacillus plantarum PS128 Promotes Intestinal Motility, Mucin Production, and Serotonin Signaling in Mice

Lactobacillus plantarum PS128 has been reported as a psychobiotic to improve mental health through the gut–brain axis in experimental animal models. To explore its mechanism of action in the gut, this study aimed to analyze the effects of L. plantarum PS128 ingestion on naïve and loperamide (Lop)-induced constipation mice. We found that, in the two mouse models, the weight, number, and water content of feces in the L. plantarum PS128 group were higher than those in the vehicle control group. Histological observation revealed that L. plantarum PS128 increased the level of colonic mucins including the major mucin MUC2. In addition, the charcoal meal test showed that L. plantarum PS128 significantly increased the small intestine transit in naïve mice, but not in the Lop-treated mice. Since intestinal serotonin has been found to modulate motility, we further analyzed the expression of genes related to serotonin signal transduction in the small intestine of naïve mice. The results showed that L. plantarum PS128 significantly altered the expression levels of Tph1, Chga, Slc6a4, and Htr4, but did not affect the expression levels of Tph2, Htr3a, and Maoa. Furthermore, immunohistochemistry revealed that L. plantarum PS128 significantly increased the number of serotonin-containing intestinal cells in mice. Taken together, our results suggest that L. plantarum PS128 could promote intestinal motility, mucin production, and serotonin signal transduction, leading to a laxative effect in mice.

The Novel Small-Molecule SR18662 Efficiently Inhibits the Growth of Colorectal Cancer In Vitro and In Vivo

Krüppel-like factor 5 (KLF5), a member of the SP/KLF family of zinc finger transcription factors, is overexpressed in human colorectal cancer specimens, and this overabundance is associated with aggressive cancer development and progression. We demonstrated that mice haploinsufficient for Klf5 had reduced intestinal tumor burden in the background of germline mutation in Apc, a gatekeeper of intestinal tumorigenesis. Based on a high-throughput screening strategy, we developed ML264, a small-molecule compound that inhibits KLF5, and showed that it inhibits growth of colorectal cancer in vitro and in vivo Through optimization efforts based on the structure of ML264, we have now identified a new lead compound, SR18662. We find that treatment with SR18662 significantly reduces growth and proliferation of colorectal cancer cells as compared with treatment with vehicle control, ML264, or SR15006 (a less optimized analogue from SAR efforts leading to SR18662). SR18662 showed improved efficacy in reducing the viability of multiple colorectal cancer cell lines. Flow cytometry analysis following SR18662 treatment showed an increase in cells captured in either S or G₂-M phases of the cell cycle and a significant increase in the number of apoptotic cells, the latter a unique property compared with ML264 or SR15006. SR18662 treatment also reduces the expression of cyclins and components of the MAPK and WNT signaling pathways. Importantly, we observed a significant dose-dependent inhibition of xenograft growth in mice following SR18662 treatment that exceeded the effect of ML264 at equivalent doses. These findings support further development of SR18662 and its analogues for colorectal cancer therapy.

The Krüppel-like factor (KLF5) as a predictive biomarker in preoperative chemoradiation therapy for rectal cancer

Purpose

Preoperative chemoradiation therapy (CRT) has become the standard treatment for patients with locally advanced rectal cancer, 15%–30% of patients still progress while being treated with CRT. The aim of this study was to identify as important biomarker of poor response and evaluate the mechanism associated with CRT resistance.

Methods

This study included 60 human colon tumour pre-irradiation specimens. Expressions of epidermal growth factor receptor (EGFR), p53, Krüppel-like factor 5 (KLF5), C-ern, Ki67 were assessed and correlated with tumor regression grades and complete remission. We added in vitro study with biomarker which has been identified as important biomarker of poor response to evaluate the mechanism associated with CRT resistance.

Results

Pathologic complete remission (pCR) was achieved by 9 patients (18%). EGFR and KLF5 were significantly associated with pCR (P = 0.048, P = 0.023, respectfully). And multivariate analysis showed high KLF5 intensity was worse factor for pCR (P = 0.012). In vitro study, radiation or chemotherapy therapy stabilized KLF5 protein levels in a time- and dose-depended manner in HCT116 and Caco-2 cells. KLF5 overexpression in HCT116 stable cell line showed significantly better cell viability by increasing cyclinD1 and b-catenin compared to control cells in MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, suggesting that KLF5 mediates cell survival.

Conclusion

KLF5 was significantly associated with the presence of KRAS mutations, and KLF5 was an independent poor response predictor of CRT in rectal cancer. Our study is pilot study and more research will be needed in the future.

SP and KLF Transcription Factors in Digestive Physiology and Diseases

Specificity proteins (SPs) and Krüppel-like factors (KLFs) belong to the family of transcription factors that contain conserved zinc finger domains involved in binding to target DNA sequences. Many of these proteins are expressed in different tissues and have distinct tissue-specific activities and functions. Studies have shown that SPs and KLFs regulate not only physiological processes such as growth, development, differentiation, proliferation, and embryogenesis, but pathogenesis of many diseases, including cancer and inflammatory disorders. Consistently, these proteins have been shown to regulate normal functions and pathobiology in the digestive system. We review recent findings on the tissue- and organ-specific functions of SPs and KLFs in the digestive system including the oral cavity, esophagus, stomach, small and large intestines, pancreas, and liver. We provide a list of agents under development to target these proteins.

The regulatory niche of intestinal stem cells

The niche constitutes a unique category of cells that support the microenvironment for the maintenance and self-renewal of stem cells. Intestinal stem cells reside at the base of the crypt, which contains adjacent epithelial cells, stromal cells and smooth muscle cells, and soluble and cell-associated growth and differentiation factors. We summarize here recent advances in our understanding of the crucial role of the niche in regulating stem cells. The stem cell niche maintains a balance among quiescence, proliferation and regeneration of intestinal stem cells after injury. Mesenchymal cells, Paneth cells, immune cells, endothelial cells and neural cells are important regulatory components that secrete niche ligands, growth factors and cytokines. Intestinal homeostasis is regulated by niche signalling pathways, specifically Wnt, bone morphogenetic protein, Notch and epidermal growth factor. These insights into the regulatory stem cell niche during homeostasis and post-injury regeneration offer the potential to accelerate development of therapies for intestine-related disorders.

The novel enterochromaffin marker Lmx1a regulates serotonin biosynthesis in enteroendocrine cell lineages downstream of Nkx2.2

Intestinal hormone-producing cells represent the largest endocrine system in the body, but remarkably little is known about enteroendocrine cell type specification in the embryo and adult. We analyzed stage- and cell type-specific deletions of Nkx2.2 and its functional domains in order to characterize its role in the development and maintenance of enteroendocrine cell lineages in the mouse duodenum and colon. Although Nkx2.2 regulates enteroendocrine cell specification in the duodenum at all stages examined, it controls the differentiation of progressively fewer enteroendocrine cell populations when deleted from Ngn3(+) progenitor cells or in the adult duodenum. During embryonic development Nkx2.2 regulates all enteroendocrine cell types, except gastrin and preproglucagon. In developing Ngn3(+) enteroendocrine progenitor cells, Nkx2.2 is not required for the specification of neuropeptide Y and vasoactive intestinal polypeptide, indicating that a subset of these cell populations derive from an Nkx2.2-independent lineage. In adult duodenum, Nkx2.2 becomes dispensable for cholecystokinin and secretin production. In all stages and Nkx2.2 mutant conditions, serotonin-producing enterochromaffin cells were the most severely reduced enteroendocrine lineage in the duodenum and colon. We determined that the transcription factor Lmx1a is expressed in enterochromaffin cells and functions downstream of Nkx2.2. Lmx1a-deficient mice have reduced expression of Tph1, the rate-limiting enzyme for serotonin biosynthesis. These data clarify the function of Nkx2.2 in the specification and homeostatic maintenance of enteroendocrine populations, and identify Lmx1a as a novel enterochromaffin cell marker that is also essential for the production of the serotonin biosynthetic enzyme Tph1.

Krüppel-Like Factor 5 Promotes Epithelial Proliferation and DNA Damage Repair in the Intestine of Irradiated Mice

BACKGROUND & AIMS: High doses of radiation induce severe DNA damage in intestinal epithelial cells, especially crypt cells, and cause intestinal injury, but the underlying molecular mechanisms remain unclear. Krüppel-like factor 5 (KLF5), a zinc finger-containing transcription factor, is induced by various stress stimuli and is involved in cell proliferation and survival. The role of KLF5 in radiation-induced intestinal injury was investigated here.

METHODS: Wild type mice were treated with 8 or 15 Gy total body irradiation (TBI). KLF5 content and cellular localization in the small intestines of irradiated mice were detected by Western blot and immunohistochemical analysis. Mice with intestinal-specific knockdown of KLF5 (Vil-Cre; Klf5^fl/+ mice) were generated and their response to radiation was compared with controls. Morphological changes were determined by hematoxylin and eosin staining. Proliferation was examined by Ki67 immunostaining. The molecular response of the small intestine after KLF5 knockdown was investigated using microarrays.

RESULTS: KLF5 expression correlated with the progression of intestinal damage. Decreased levels of KLF5 in the gut were associated with increased damage to the intestinal mucosa and reduced epithelial proliferation after TBI. Our microarray data disclosed that KLF5 knockdown down-regulated genes related to DNA damage repair pathways such as nucleotide excision repair, mismatch repair, non-homologous end joining and the Fanconi anemia pathway, which may suggest a novel function of KLF5.

CONCLUSIONS: Our study illustrates that KLF5 may modulate DNA repair pathways to prevent intestinal injury induced by TBI. KLF5 signaling provides a novel field for identification of potential therapeutic targets for the treatment of radiation-induced intestinal damage.

Three cheers for the goblet cell: maintaining homeostasis in mucosal epithelia

Many organs throughout the body maintain epithelial homeostasis by employing a mucosal barrier which acts as a lubricant and helps to preserve a near-sterile epithelium. Goblet cells are largely responsible for secreting components of this mucosal barrier and represent a major cellular component of the innate defense system. In this review we summarize what is known about the signaling pathways that control goblet cell differentiation in the intestine, the lung, and the ocular surface, and we discuss a novel functional role for goblet cells in mucosal epithelial immunology. We highlight the cell type-specificity of the circuitry regulating goblet cell differentiation and shed light on how changes to these pathways lead to altered goblet cell function, a prominent feature of mucosa-associated diseases.