Long non-coding RNAs (lncRNAs) are emerging as key molecules in cancers, yet their potential molecular mechanisms are not well understood. The objective of this study is to examine the expression and ...functions of lncRNAs in the development of colorectal cancer (CRC).
LncRNA expression profiling of CRC, adenoma and normal colorectal tissues was performed to identify tumour-related lncRNAs involved in colorectal malignant transformation. Then, we used quantitative reverse transcription PCR assays to measure the tumour-related lncRNA and to assess its association with survival and response to adjuvant chemotherapy in 252 patients with CRC. The mechanisms of CCAL function and regulation in CRC were examined using molecular biological methods.
We identified colorectal cancer-associated lncRNA (CCAL) as a key regulator of CRC progression. Patients whose tumours had high CCAL expression had a shorter overall survival and a worse response to adjuvant chemotherapy than patients whose tumours had low CCAL expression. CCAL promoted CRC progression by targeting activator protein 2α (AP-2α), which in turn activated Wnt/β-catenin pathway. CCAL induced multidrug resistance (MDR) through activating Wnt/β-catenin signalling by suppressing AP-2α and further upregulating MDR1/P-gp expression. In addition, we found that histone H3 methylation and deacetylases contributed to the upregulation of CCAL in CRC.
Our results suggest that CCAL is a crucial oncogenic regulator involved in CRC tumorigenesis and progression.
Nearly 20% of the global cancer burden can be linked to infectious agents. Fusobacterium nucleatum promotes tumor formation by epithelial cells via unclear mechanisms. We aimed to identify microRNAs ...(miRNAs) induced by F nucleatum and evaluate their ability to promote colorectal carcinogenesis in mice.
Colorectal cancer (CRC) cell lines were incubated with F nucleatum or control reagents and analyzed in proliferation and would healing assays. HCT116, HT29, LoVo, and SW480 CRC cell lines were incubated with F nucleatum or phosphate-buffered saline (PBS control) and analyzed for miRNA expression patterns and in chromatin immunoprecipitation assays. Cells were incubated with miRNAs mimics, control sequences, or small interfering RNAs; expression of reporter constructs was measured in luciferase assays. CRC cells were incubated with F nucleatum or PBS and injected into BALB/C nude mice; growth of xenograft tumors was measured. C57BL adenomatous polyposis colimin/+, C57BL miR21a−/−, and C57BL mice with full-length miR21a (controls) were given F nucleatum by gavage; some mice were given azoxymethane and dextran sodium sulfate to induce colitis and colon tumors. Intestinal tissues were collected and tumors were counted. Serum samples from mice were analyzed for cytokine levels by enzyme-linked immunosorbent assay. We performed in situ hybridization analyses to detect enrichment of F nucleatum in CRC cells. Fusobacterium nucleatum DNA in 90 tumor and matched nontumor tissues from patients in China were explored for the expression correlation analysis; levels in 125 tumor tissues from patients in Japan were compared with their survival times.
Fusobacterium nucleatum increased proliferation and invasive activities of CRC cell lines compared with control cells. CRC cell lines infected with F nucleatum formed larger tumors, more rapidly, in nude mice than uninfected cells. Adenomatous polyposis colimin/+ mice gavaged with F nucleatum developed significantly more colorectal tumors than mice given PBS and had shorter survival times. We found several inflammatory factors to be significantly increased in serum from mice given F nucleatum (interleukin 17F, interleukin 21, and interleukin 22, and MIP3A). We found 50 miRNAs to be significantly up-regulated and 52 miRNAs to be significantly down-regulated in CRCs incubated with F nucleatum vs PBS; levels of miR21 increased by the greatest amount (>4-fold). Inhibitors of miR21 prevented F nucleatum from inducing cell proliferation and invasion in culture. miR21a−/− mice had a later appearance of fecal blood and diarrhea after administration of azoxymethane and dextran sodium sulfate, and had longer survival times compared with control mice. The colorectum of miR21a−/− mice had fewer tumors, of smaller size, and the miR21a−/− mice survived longer than control mice. We found RASA1, which encodes an RAS GTPase, to be one of the target genes consistently down-regulated in cells that overexpressed miR21 and up-regulated in cells exposed to miR21 inhibitors. Infection of cells with F nucleatum increased expression of miR21 by activating Toll-like receptor 4 signaling to MYD88, leading to activation of the nuclear factor−κB. Levels of F nucleatum DNA and miR21 were increased in tumor tissues (and even more so in advanced tumor tissues) compared with non-tumor colon tissues from patients. Patients whose tumors had high amounts of F nucleatum DNA and miR21 had shorter survival times than patients whose tumors had lower amounts.
We found infection of CRC cells with F nucleatum to increase their proliferation, invasive activity, and ability to form xenograft tumors in mice. Fusobacterium nucleatum activates Toll-like receptor 4 signaling to MYD88, leading to activation of the nuclear factor−κB and increased expression of miR21; this miRNA reduces levels of the RAS GTPase RASA1. Patients with both high amount of tissue F nucleatum DNA and miR21 demonstrated a higher risk for poor outcomes.
Colorectal cancer stem cells (CR-CSC) are responsible for the generation and maintenance of intestinal tumors and are highly resistant to conventional chemotherapeutic agents. Aurora-A, a ...serine-threonine kinase involved in mitosis regulation, plays multiple key functions in tumor initiation and progression. We found that Aurora-A is overexpressed in primary colorectal tumor cells, in the CR-CSC fraction, and in stem cell-derived differentiated cells, compared with normal colon tissue. Aurora-A expression was functionally linked to centrosome amplification in CR-CSC, as indicated by the decrease in cells with multiple centrosomes that followed Aurora-A silencing. Knockdown of Aurora-A resulted in growth inhibition of CR-CSC, alteration of cell cycle kinetics, and downregulation of the expression levels of antiapoptotic Bcl-2 family members, strongly sensitizing to chemotherapy-induced cell death. Moreover, Aurora-A silencing compromised the ability to form tumor xenografts in immunocompromised mice and reduced the migratory capacity of CR-CSC. Altogether, these results indicate that Aurora-A is essential for CR-CSC regeneration and resistance to cytotoxic stimuli and suggest that therapies directed against Aurora-A may effectively target the stem cell population in colorectal cancer.
Background/Aims: Let-7b was dramatically reduced after a dicer knockout of mice with intestinal barrier function injuries. This paper aims to investigate the molecular mechanism of let-7b by ...targeting p38 MAPK in preventing intestinal barrier dysfunction. Methods: A total of 186 patients were enrolled, with 93 in the control group and 93 in the PRO group. Only 158 patients completed the entire study, whereas the others either did not meet the inclusion criteria or refused to participate. To further verify the role of let-7b, intestinal epithelial conditional knockout (IKO) mice of mmu-let-7b model were established. Serum let-7b, zonulin, IL-6, and TNF-α concentrations were measured by ELISA or quantitative RT-PCR. Permeability assay was done by ussing chamber. The apoptotic cells were identified using an In Situ Cell Death Detection Kit. Protein was detected by western blot. Results: Probiotics can lower infection-related complications, as well as increase the serum and tissue let-7b levels. P38 MAPK was identified as the target of let-7b, as verified by NCM460 cells. P38 MAPK expression was increased, whereas tight-junction (TJ) proteins were significantly decreased in let-7b IKO mice (both P<0.05). Negative regulation of p38 MAPK molecular signaling pathways was involved in the protective effects of let-7b on intestinal barrier function. Conclusion: Let-7b was identified as a novel diagnosis biomarker or a potential treatment target for preventing intestinal barrier dysfunction.
TNF plays an integral role in inflammatory bowel disease (IBD), as evidenced by the dramatic therapeutic responses in Crohn's disease (CD) patients induced by chimeric anti-TNF mAbs. However, ...treatment of CD patients with etanercept, a decoy receptor that binds soluble TNF, fails to improve disease. To explore this discrepancy, we investigated the role of TNF signaling in Wnt/β-catenin-mediated intestinal stem cell and progenitor cell expansion in CD patients, human cells, and preclinical mouse models. We hypothesized that TNF exerts beneficial effects on intestinal epithelial cell (IEC) responses to injury. In CD patients, intestinal stem cell and progenitor cell Wnt/β-catenin signaling correlates with inflammation status. TNF-deficient (
) mice exhibited increased apoptosis, less IEC proliferation, and less Wnt signaling when stimulated with anti-CD3 mAb. Bone marrow (BM) chimera mice revealed that mucosal repair depended on TNF production by BM-derived cells and TNFR expression by radioresistant IECs. Wild-type→
BM chimera mice with chronic dextran sodium sulfate colitis exhibited delayed ulcer healing, more mucosal inflammation, and impaired Wnt/β-catenin signaling, consistent with the hypothesis that epithelial TNFR signaling participates in mucosal healing. The direct effect of TNF on stem cells was demonstrated by studies of TNF-induced Wnt/β-catenin target gene expression in murine enteroids and colonoid cultures and TNF-induced β-catenin activation in nontransformed human NCM460 cells (TOPFlash) and mice (TOP-GAL). Together, these data support the hypothesis that TNF plays a beneficial role in enhancing Wnt/β-catenin signaling during ulcer healing in IBD. These novel findings will inform clinicians and therapeutic chemists alike as they strive to develop novel therapies for IBD patients.
In the western world, colorectal cancer (CRC) is the third most common cause of cancer-related deaths. Survival is closely related to the stage of cancer at diagnosis striking the clinical need for ...biomarkers capable of early detection. To search for possible biological parameters for early diagnosis of CRC we evaluated protein expression for three CREC (acronym:
ab45,
eticulocalbin,
RC-55,
alumenin) proteins: reticulocalbin, calumenin, and ERC-55 in a cellular model consisting of a normal derived colon mucosa cell line, NCM460, and a primary adenocarcinoma cell line of the colon, SW480. Furthermore, this cellular model was analyzed by a top-down proteomic approach, 2-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for novel putative diagnostic markers by identification of differentially expressed proteins between the two cell lines. A different colorectal carcinoma cell line, HCT 116, was used in a bottom-up proteomic approach with label-free quantification (LFQ) LC-MS/MS. The two cellular models gave sets of putative diagnostic CRC biomarkers. Various of these novel putative markers were verified with increased expression in CRC patient neoplastic tissue compared to the expression in a non-involved part of the colon, including reticulocalbin, calumenin, S100A6 and protein SET. Characterization of these novel identified biological features for CRC patients may have diagnostic potential and therapeutic relevance in this malignancy characterized by a still unmet clinical need.
The premessenger RNA of the majority of human genes can generate various transcripts through alternative splicing, and different tissues or disease states show specific patterns of splicing variants. ...These patterns depend on the relative concentrations of the splicing factors present in the cell nucleus, either as a consequence of their expression levels or of post-translational modifications, such as protein phosphorylation, which are determined by signal transduction pathways. Here, we analyzed the contribution of protein kinases to the regulation of alternative splicing variant Rac1b that is overexpressed in certain tumor types. In colorectal cells, we found that depletion of AKT2, AKT3, GSK3β, and SRPK1 significantly decreased endogenous Rac1b levels. Although knockdown of AKT2 and AKT3 affected only Rac1b protein levels suggesting a post-splicing effect, the depletion of GSK3β or SRPK1 decreased Rac1b alternative splicing, an effect mediated through changes in splicing factor SRSF1. In particular, the knockdown of SRPK1 or inhibition of its catalytic activity reduced phosphorylation and subsequent translocation of SRSF1 to the nucleus, limiting its availability to promote the inclusion of alternative exon 3b into the Rac1 pre-mRNA. Altogether, the data identify SRSF1 as a prime regulator of Rac1b expression in colorectal cells and provide further mechanistic insight into how the regulation of alternative splicing events by protein kinases can contribute to sustain tumor cell survival.
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