Evaluation of the germline single nucleotide polymorphism rs583522 in the TNFAIP3 gene as a prognostic marker in esophageal cancer

A20 Restricts NOS2 Expression and Intestinal Tumorigenesis in a Mouse Model of Colitis-Associated Cancer

BACKGROUND AND AIMS

Colon cancer can occur sporadically or in the setting of chronic inflammation, such as in patients with inflammatory bowel disease. We previously showed that A20, a critical negative regulator of tumor necrosis factor signal transduction, could regulate sporadic colon cancer development. In this report, we investigate whether A20 also acts as a tumor suppressor in a model of colitis-associated cancer.

METHODS

Colitis and colitis-associated tumors were induced in wild-type and A20 intestinal epithelial cell-specific knockout (A20dIEC) mice using dextran sodium sulfate and azoxymethane. Clinicopathologic markers of inflammation were assessed in conjunction with colonic tumor burden. Gene expression analyses and immunohistochemistry were performed on colonic tissue and intestinal enteroids. Nitric oxide (NO) production and activity were assessed in whole colonic lysates and mouse embryonic fibroblasts.

RESULTS

A20dIEC mice develop larger tumors after treatment with dextran sodium sulfate and azoxymethane than wild-type mice. In addition to elevated markers of inflammation, A20dIEC mice have significantly enhanced expression of inducible nitric oxide synthase (iNOS), a well-known driver of neoplasia. Enhanced iNOS expression is associated with the formation of reactive nitrogen species and DNA damage. Loss of A20 also enhances NO-dependent cell death directly.

CONCLUSION

Mechanistically, we propose that A20 normally restricts tumor necrosis factor-induced nuclear factor kappa B-dependent production of iNOS in intestinal epithelial cells, thereby protecting against colitis-associated tumorigenesis. We also propose that A20 plays a direct role in regulating NO-dependent cell death.

The dual roles of A20 in cancer

A20 is a prototypical anti-inflammatory molecule that is linked to multiple human diseases, including cancers. The role of A20 as a tumor suppressor was first discovered in B cell lymphomas. Subsequent studies revealed the dual roles of A20 in solid cancers. This review focuses on the roles of A20 in different cancer types to demonstrate that the effects of A20 are cancer type-dependent. A20 plays antitumor roles in colorectal carcinomas and hepatocellular carcinomas, whereas A20 acts as an oncogene in breast cancers, gastric cancers and melanomas. Moreover, the roles of A20 in the setting of glioma therapy are context-dependent. The action mechanisms of A20 in different types of cancer are summarized. Additionally, the role of A20 in antitumor immunity is discussed. Furthermore, some open questions in this rapidly advancing field are proposed. Exploration of the actions and molecular mechanisms of A20 in cancer paves the way for the application of A20-targeting approaches in future cancer therapy.

Rare Tumor-Normal Matched Whole Exome Sequencing Identifies Novel Genomic Pathogenic Germline and Somatic Aberrations

Whole exome sequencing (WES) of matched tumor-normal pairs in rare tumors has the potential to identify genome-wide mutations and copy number alterations (CNAs). We evaluated 27 rare cancer patients with tumor-normal matching by WES and tumor-only next generation sequencing (NGS) as a comparator. Our goal was to: 1) identify known and novel variants and CNAs in rare cancers with comparison to common cancers; 2) examine differences between germline and somatic variants and how that functionally impacts rare tumors; 3) detect and characterize alleles in biologically relevant genes-pathways that may be of clinical importance but not represented in classical cancer genes. We identified 3343 germline single nucleotide variants (SNVs) and small indel variants-1670 in oncogenes and 1673 in tumor suppressor genes-generating an average of 124 germline variants/case. The number of somatic SNVs and small indels detected in all cases was 523:306 in oncogenes and 217 in tumor suppressor genes. Of the germline variants, six were identified to be pathogenic or likely pathogenic. In the 27 analyzed rare cancer cases, CNAs are variable depending on tumor type, germline pathogenic variants are more common. Cell fate pathway mutations (e.g., Hippo, Notch, Wnt) dominate pathogenesis and double hit (mutation + CNV) represent ~18% cases.

A20: A multifunctional tool for regulating immunity and preventing disease

A20, also known as TNFAIP3, is a potent regulator of ubiquitin (Ub) dependent signals. A20 prevents multiple human diseases, indicating that the critical functions of this protein are clinically as well as biologically impactful. As revealed by mouse models, cell specific functions of A20 are linked to its ability to regulate diverse signaling pathways. Aberrant expression or functions of A20 in specific cell types underlie divergent disease outcomes. Discernment of A20's biochemical functions and their phenotypic outcomes will contribute to our understanding of how ubiquitination is regulated, how Ub mediated functions can prevent disease, and will pave the way for future therapeutic interventions.

The inhibitory effects of COL1A2 on colorectal cancer cell proliferation, migration, and invasion

Purpose: Collagen type I alpha 2 chain (COL1A2) has been shown to participate in the development of various human malignancies. However, the role of COL1A2 in human colorectal cancer (CRC) remains unknown. This study investigated the expression pattern of COL1A2 in primary CRC tissues as well as the correlation of COL1A2 expression with clinicopathological features and prognosis of CRC. The function of COL1A2 in CRC cell proliferation, migration, and invasion as well as the possible mechanisms were also examined. Methods: Real-time PCR and immunohistochemical analysis were performed to determine the expression of COL1A2 in primary cancer tissues and adjacent normal tissues from CRC patients. A COL1A2-expressing lentiviral vector was transfected into CRC cells, and cell counting kit-8 and Transwell assays were used to explore the effects of COL1A2 on CRC cell proliferation, migration, and invasion. Microarray-based mRNA expression profile screening was performed to reveal the possible signaling pathways involved in COL1A2-regulated cell behaviors. Results: COL1A2 was significantly downregulated in primary CRC tissues. The mRNA levels of COL1A2 in CRC tissues were correlated with tumor differentiation, invasion, and lymph node metastasis. Overexpression of COL1A2 inhibited proliferation, migration, and invasion of CRC cell lines (SW480 and SW620). The microarray analysis showed that COL1A2 overexpression regulated numerous oncogenes and cancer-related signaling pathways. Among them, altered expression of ten representative cancer-related genes in these pathways were further confirmed by western blotting. Conclusions: Our study identified COL1A2 as a novel tumor suppressor in CRC and provided a potential therapeutic approach to treat CRC.