TRAF6-Mediated Inflammatory Cytokines Secretion in LPS-induced Colorectal Cancer Cells Is Regulated by miR-140

Anticancer Potential of Flavonoids: An Overview with an Emphasis on Tangeretin

Natural compounds with pharmacological activity, flavonoids have been the subject of an exponential increase in studies in the field of scientific research focused on therapeutic purposes due to their bioactive properties, such as antioxidant, anti-inflammatory, anti-aging, antibacterial, antiviral, neuroprotective, radioprotective, and antitumor activities. The biological potential of flavonoids, added to their bioavailability, cost-effectiveness, and minimal side effects, direct them as promising cytotoxic anticancer compounds in the optimization of therapies and the search for new drugs in the treatment of cancer, since some extensively antineoplastic therapeutic approaches have become less effective due to tumor resistance to drugs commonly used in chemotherapy. In this review, we emphasize the antitumor properties of tangeretin, a flavonoid found in citrus fruits that has shown activity against some hallmarks of cancer in several types of cancerous cell lines, such as antiproliferative, apoptotic, anti-inflammatory, anti-metastatic, anti-angiogenic, antioxidant, regulatory expression of tumor-suppressor genes, and epigenetic modulation.

Gut Barrier Dysfunction and Bacterial Lipopolysaccharides in Colorectal Cancer

BACKGROUND

Inflammation is known to be an essential driver of various types of cancer. An increasing number of studies have suggested that the occurrence and development of colorectal cancer (CRC) are linked to the inflammatory microenvironment of the intestine. This assumption is further supported by the fact that patients with inflammatory bowel disease (IBD) are more likely to develop CRC. Multiple studies in mice and humans have shown that preoperative systemic inflammatory response is predictive of cancer recurrence after potentially curative resection. Lipopolysaccharides (LPS) are membrane surface markers of gram-negative bacteria, which induce gut barrier dysfunction and inflammation and might be significantly involved in the occurrence and development of CRC.

METHODS

A selective literature search was conducted in Medline and PubMed, using the terms "Colorectal Cancer", "Gut Barrier", "Lipopolysaccharides", and "Inflammation".

RESULTS

Disruption of intestinal homeostasis, including gut barrier dysfunction, is linked to increased LPS levels and is a critical factor for chronic inflammation. LPS can activate the diverse nuclear factor-κB (NF-κB) pathway via Toll-like receptors 4 (TLR4) to promote the inflammatory response, which aggravates gut barrier dysfunction and encourages CRC development. An intact gut barrier prevents antigens and bacteria from crossing the intestinal endothelial layer and entering circulation. In contrast, a damaged gut barrier triggers inflammatory responses and increases susceptibility to CRC. Thus, targeting LPS and the gut barrier might be a promising novel therapeutic approach for additional treatment of CRC.

CONCLUSION

Gut barrier dysfuction and bacterial LPS seem to play an important role in the pathogenesis and disease progression of colorectal cancer and therefore require further investigation.

Ficus dubia Latex Extract Induces Cell Cycle Arrest and Apoptosis by Regulating the NF-κB Pathway in Inflammatory Human Colorectal Cancer Cell Lines

Simple Summary

In this study, the anti-tumor activity of Ficus dubia latex extract (FDLE) against HCT-116 and HT-29 human colorectal cancer cell lines in normal and inflammatory conditions was investigated. The results indicated that an inflammation-activated NF-κB increased proliferation-related proteins and decreased apoptosis-related proteins, leading to hyperproliferation of colorectal cancer cell lines. FDLE exhibited remarkable antiproliferative activity in both conditions, however, more effective anti-proliferation was observed due to its more effective regulation of NF-κB inactivation and some proteins related to cell cycle progression and apoptosis induction in inflammatory condition. Our finding may promote the antiproliferative study of FDLE in inflammation-induced colorectal cancer progression.

Abstract

Colorectal cancer is one of the most diagnosed cancers that is associated with inflammation. Ficus dubia latex is recognized as a remedy with various therapeutic effects in traditional medicine, including anti-inflammatory and antioxidant activity. The present study aims to compare the anti-tumor activity of Ficus dubia latex extract (FDLE) against HCT-116 and HT-29 human colorectal cancer cell lines in normal and inflammatory condition and explore its mechanism of action. FDLE exhibited remarkable antiproliferative activity against HCT-116 and HT-29 colorectal cancer cell lines in both conditions using MTT and colony formation assays and more effective anti-proliferation was observed in inflammatory condition. Mechanistically, FDLE induced cell cycle arrest at G0/G1 phase by down-regulating NF-κB, cyclin D1, CDK4 and up-regulatingp21 in both cell in normal condition. In inflammatory condition, FDLE not only exhibited stronger induction of cell cycle arrest in both cells by down-regulating NF-κB, cyclin D1, CDK4 and down-regulating p21, but also selectively induced apoptosis in HCT-116 cells by down-regulating NF-κB and Bcl-xl and up-regulating Bid, Bak, cleaved caspase-7 and caspase-3 through stronger ability to regulate these proteins. Our results demonstrated that the phytochemical agent in the latex of Ficus dubia could potential be used for treatment and prevention of human colorectal cancer, especially in inflammation-induced hyperproliferation progression.

TRAF6 regulates the signaling pathway influencing colorectal cancer function by ubiquitination mechanisms

Tumor necrosis factor receptor‐associated factor‐6 (TRAF6) is a ubiquitin E3 ligase. TRAF6 plays an important role in tumor invasion and metastasis. However, the specific mechanism by which TRAF6 promotes colorectal cancer (CRC) metastasis is incompletely understood. This study aimed to determine whether TRAF6 affects the LPS‐NF‐κB‐VEGF‐C signaling pathway through ubiquitination, which plays a role in colorectal cancer metastasis. Here, our results showed that TRAF6 affected lymphangiogenesis through the LPS‐NF‐κB‐VEGF‐C signaling pathway. Using ubiquitination experiments, we found that TRAF6 was mainly ubiquitinated with the K63‐linked chains, and LPS promoted ubiquitination of TRAF6 and K63‐linked chains. More importantly, TRAF6 124mut is the main ubiquitination site of TRAF6 interacting with K63‐linked chains. TRAF6 affected the migration, invasion, and lymphatic metastasis of colorectal cancer through its ubiquitination. In subcutaneous xenograft models, TRAF6 124mut inhibited tumor growth. In conclusion, our results provide new insight for studying the mechanism of lymphangiogenesis in colorectal cancer to promote cancer metastasis, which may provide new ideas for tumor immunotherapy.

The Structure and Ubiquitin Binding Properties of TRAF RING Heterodimers

Tumour necrosis factor (TNF) receptor associated factor (TRAF) family members share a common domain architecture, but play non-redundant physiological roles in cell signalling. At the N terminus, most TRAFs have a RING domain, followed by a series of Zinc finger (ZF) domains. The RING domain of TRAF6 dimerizes, and the RING homodimer together with the first ZF assembles ubiquitin chains that form a platform which facilitates activation of downstream kinases. The RING dimer interface is conserved amongst TRAF proteins, suggesting that functional heterodimers could be possible. Here we report the structure of the TRAF5-TRAF6 RING heterodimer, which accounts for the stability of the heterodimer as well as its ability to assemble ubiquitin chains. We also show that the RING domain of TRAF6 heterodimerizes with TRAF3 and TRAF2, and demonstrate that the linker helix and first ZF of TRAF2 can cooperate with TRAF6 to promote chain assembly. Collectively our results suggest that TRAF RING homo- and hetero-dimers have the potential to bridge interaction of nearby TRAF trimers and modulate TRAF-mediated signalling.

Neurensin-2 promotes proliferation, invasion and migration of colorectal cancer cells via interaction with SOX12

Colorectal cancer (CRC) is the third most common malignant type of tumor worldwide. Neurensin-2 (NRSN2) is a small neuronal membrane protein associated with tumorigenesis. Therefore, the present study aimed to investigate the association between NRSN2 and CRC, and further examined the underlying mechanism of its effect on CRC metastasis. Human CRC SW620 cells were used to determine the biological functions of NRSN2 in CRC. Cell counting Kit-8 (CCK8), colony formation, wound-healing and transwell assays were performed to evaluate the role of NRSN2 on survival and metastasis of SW620 cells. The interaction between NRSN2 and SOX12 was determined via bioinformatics analysis and confirmed using immunoprecipitation. It was identified that NRSN2 was highly expressed in CRC cells and served a critical role in CRC cell survival compared with in healthy colon epithelial cells. Furthermore, NRSN2-knockdown inhibited the proliferation, invasion and migration of SW620 cells, while NRSN2 overexpression promoted these cellular processes. Additionally, it was demonstrated that NRSN2 could recruit SOX12 in SW620 cells. NRSN2-knockdown decreased SOX12 expression, while NRSN2 overexpression upregulated SOX12 expression. Overall, the present results suggested NRSN2 as a novel biomarker for CRC diagnosis and identified NRSN2 as a potential therapeutic target for CRC treatment.

Tumor cell endogenous HIF-1α activity induces aberrant angiogenesis and interacts with TRAF6 pathway required for colorectal cancer development

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Findings provide evidence that hypoxia response deficient tumors show more functionally perfused vasculature and that TRAF6, an upstream effector of NF-κB, is directly interacting with HIF-1α thereby contributing to enhanced angiogenesis.

Hypoxia and inflammation are key factors for colorectal cancer tumorigenesis. The colonic epithelium belongs to the tissues with the lowest partial pressure of oxygen in the body, and chronic inflammation is associated with an increased chance to develop colon cancer. How the colonic epithelium responds to hypoxia and inflammation during tumorigenesis remains to be elucidated. Here we show, that murine colon adenocarcinoma cells with attenuated response to hypoxia, due to a knock-down (KD) of HIF-1α, produce smaller and less hypoxic tumors in an orthotopic mouse model when compared to tumors induced with control cells. HIF-1α-KD tumors showed more functional perfused vasculature associated with increased levels of vessel-stabilizing factors and reduced levels of proangiogenic factors, including extracellular matrix protein Cyr61/CCN1. Intratumoral injection of Cyr61 in HIF-1α-KD tumors revealed an in increased vessel permeability and tumor hypoxia. Further bioinformatics analysis identified a possible interaction between HIF-1α and TRAF6, an upstream effector of the NF-κB pathway that was confirmed by coimmunoprecipitation in MC-38 and CT26 colon adenocarcinoma cells and in situ by proximity ligation assay. Down-regulation of TRAF6 resulted in virtual abrogation of orthotopic tumor growth. Subcutaneous TRAF6-KD tumors were smaller and contained reduced vessel size and differently polarized macrophages. These data demonstrate that the tumor cell response to increased hypoxia in the colon leads to promotion of nonfunctional angiogenesis, regulated by both hypoxia and TRAF6 pathways.