Functions and Clinical Significance of UPF3a Expression in Human Colorectal Cancer

Nonsense-Mediated mRNA Decay: Mechanistic Insights and Physiological Significance

Nonsense-mediated mRNA decay (NMD) is an evolutionarily conserved surveillance mechanism across eukaryotes and also regulates the expression of physiological transcripts, thus involved in gene regulation. It essentially ensures recognition and removal of aberrant transcripts. Therefore, the NMD protects the cellular system by restricting the synthesis of truncated proteins, potentially by eliminating the faulty mRNAs. NMD is an evolutionarily conserved surveillance mechanism across eukaryotes and also regulates the expression of physiological transcripts, thus involved in gene regulation as well. Primarily, the NMD machinery scans and differentiates the aberrant and non-aberrant transcripts. A myriad of cellular dysfunctions arise due to production of truncated proteins, so the NMD core proteins, the up-frameshift factors (UPFs) recognizes the faulty mRNAs and further recruits factors resulting in the mRNA degradation. NMD exhibits astounding variability in its ability in regulating cellular mechanisms including both pathological and physiological events. But, the detailed underlying molecular mechanisms in NMD remains blurred and require extensive investigation to gain insights on cellular homeostasis. The complexity in understanding of NMD pathway arises due to the involvement of numerous proteins, molecular interactions and their functioning in different steps of this process. Moreover methods such as alternative splicing generates numerous isoforms of mRNA, so it makes difficulties in understanding the impact of alternative splicing on the efficiency of NMD functioning. Role of NMD in cancer development is very complex. Studies have shown that in some cases cancer cells use NMD pathway as a tool to exploit the NMD mechanism to maintain tumor microenvironment. A greater level of understanding about the intricate mechanism of how tumor used NMD pathway for their benefits, a strategy can be developed for targeting and inhibiting NMD factors involved in pro-tumor activity. There are very little amount of information available about the NMD pathway, how it discriminate mRNAs that are targeted by NMD from those that are not. This review highlights our current understanding of NMD, specifically the regulatory mechanisms and attempts to outline less explored questions that warrant further investigations. Taken as a whole, a detailed molecular understanding of the NMD mechanism could lead to wide-ranging applications for improving cellular homeostasis and paving out strategies in combating pathological disorders leaping forward toward achieving United Nations sustainable development goals (SDG 3: Good health and well-being).

Serum methylation of GALNT9, UPF3A, WARS, and LDB2 as noninvasive biomarkers for the early detection of colorectal cancer and advanced adenomas

BACKGROUND

Early detection has proven to be the most effective strategy to reduce the incidence and mortality of colorectal cancer (CRC). Nevertheless, most current screening programs suffer from low participation rates. A blood test may improve both the adherence to screening and the selection to colonoscopy. In this study, we conducted a serum-based discovery and validation of cfDNA methylation biomarkers for CRC screening in a multicenter cohort of 433 serum samples including healthy controls, benign pathologies, advanced adenomas (AA), and CRC.

RESULTS

First, we performed an epigenome-wide methylation analysis with the MethylationEPIC array using a sample pooling approach, followed by a robust prioritization of candidate biomarkers for the detection of advanced neoplasia (AN: AA and CRC). Then, candidate biomarkers were validated by pyrosequencing in independent individual cfDNA samples. We report GALNT9, UPF3A, WARS, and LDB2 as new noninvasive biomarkers for the early detection of AN. The combination of GALNT9/UPF3A by logistic regression discriminated AN with 78.8% sensitivity and 100% specificity, outperforming the commonly used fecal immunochemical test and the methylated SEPT9 blood test.

CONCLUSIONS

Overall, this study highlights the utility of cfDNA methylation for CRC screening. Our results suggest that the combination methylated GALNT9/UPF3A has the potential to serve as a highly specific and sensitive blood-based test for screening and early detection of CRC.

Targeted splicing therapy: new strategies for colorectal cancer

RNA splicing is the process of forming mature mRNA, which is an essential phase necessary for gene expression and controls many aspects of cell proliferation, survival, and differentiation. Abnormal gene-splicing events are closely related to the development of tumors, and the generation of oncogenic isoform in splicing can promote tumor progression. As a main process of tumor-specific splicing variants, alternative splicing (AS) can promote tumor progression by increasing the production of oncogenic splicing isoforms and/or reducing the production of normal splicing isoforms. This is the focus of current research on the regulation of aberrant tumor splicing. So far, AS has been found to be associated with various aspects of tumor biology, including cell proliferation and invasion, resistance to apoptosis, and sensitivity to different chemotherapeutic drugs. This article will review the abnormal splicing events in colorectal cancer (CRC), especially the tumor-associated splicing variants arising from AS, aiming to offer an insight into CRC-targeted splicing therapy.

Characterization of a rhabdomyosarcoma reveals a critical role for SMG7 in cancer cell viability and tumor growth

Soft-tissue sarcomas (STSs) are a rare and diverse group of mesenchymal cancers plagued with aggression, poor response to systemic therapy, and high rates of recurrence. Although STSs generally have low mutational burdens, the most commonly mutated genes are tumor suppressors, which frequently acquire mutations inducing nonsense-mediated mRNA decay (NMD). This suggests that STS cells may exploit NMD to suppress these anti-cancer genes. To examine the role that the NMD factor SMG7 plays in STS, we developed an inducible knockout mouse model in the Trp53-/- background. Here, we isolated a subcutaneous STS and identified it as a rhabdomyosarcoma (RMS). We report that knockout of SMG7 significantly inhibited NMD in our RMS cells, which led to the induction of NMD targets GADD45b and the tumor suppressor GAS5. The loss of NMD and upregulation of these anti-cancer genes were concomitant with the loss of RMS cell viability and inhibited tumor growth. Importantly, SMG7 was dispensable for homeostasis in our mouse embryonic fibroblasts and adult mice. Overall, our data show that the loss of SMG7 induces a strong anti-cancer effect both in vitro and in vivo. We present here the first evidence that disrupting SMG7 function may be tolerable and provide a therapeutic benefit for STS treatment.

Nonsense-mediated RNA decay: an emerging modulator of malignancy

Nonsense-mediated RNA decay (NMD) is a highly conserved RNA turnover pathway that selectively degrades RNAs harbouring truncating mutations that prematurely terminate translation, including nonsense, frameshift and some splice-site mutations. Recent studies show that NMD shapes the mutational landscape of tumours by selecting for mutations that tend to downregulate the expression of tumour suppressor genes but not oncogenes. This suggests that NMD can benefit tumours, a notion further supported by the finding that mRNAs encoding immunogenic neoantigen peptides are typically targeted for decay by NMD. Together, this raises the possibility that NMD-inhibitory therapy could be of therapeutic benefit against many tumour types, including those with a high load of neoantigen-generating mutations. Complicating this scenario is the evidence that NMD can also be detrimental for many tumour types, and consequently tumours often have perturbed NMD. NMD may suppress tumour generation and progression by degrading subsets of specific normal mRNAs, including those encoding stress-response proteins, signalling factors and other proteins beneficial for tumours, as well as pro-tumour non-coding RNAs. Together, these findings suggest that NMD-modulatory therapy has the potential to provide widespread therapeutic benefit against diverse tumour types. However, whether NMD should be stimulated or repressed requires careful analysis of the tumour to be treated.

STAT3 Signaling in Breast Cancer: Multicellular Actions and Therapeutic Potential

Simple Summary

Many signaling pathways are overactive in breast cancer, and among them is the STAT3 signaling pathway. STAT3 is activated by secreted factors within the breast tumor, many of which are elevated and correlate to advanced disease and poor survival outcomes. This review examines how STAT3 signaling is activated in breast cancer by the proinflammatory, gp130 cytokines, interleukins 6 and 11. We evaluate how this signaling cascade functions in the various cells of the tumor microenvironment to drive disease progression and metastasis. We discuss how our understanding of these processes may lead to the development of novel therapeutics to tackle advanced disease.

Abstract

Interleukin (IL)-6 family cytokines, such as IL-6 and IL-11, are defined by the shared use of the gp130 receptor for the downstream activation of STAT3 signaling and the activation of genes which contribute to the “hallmarks of cancer”, including proliferation, survival, invasion and metastasis. Increased expression of these cytokines, or the ligand-specific receptors IL-6R and IL-11RA, in breast tumors positively correlate to disease progression and poorer patient outcome. In this review, we examine evidence from pre-clinical studies that correlate enhanced IL-6 and IL-11 mediated gp130/STAT3 signaling to the progression of breast cancer. Key processes by which the IL-6 family cytokines contribute to the heterogeneous nature of breast cancer, immune evasion and metastatic potential, are discussed. We examine the latest research into the therapeutic targeting of IL-6 family cytokines that inhibit STAT3 transcriptional activity as a potential breast cancer treatment, including current clinical trials. The importance of the IL-6 family of cytokines in cellular processes that promote the development and progression of breast cancer warrants further understanding of the molecular basis for its actions to help guide the development of future therapeutic targets.

Increased AOC1 Expression Promotes Cancer Progression in Colorectal Cancer

Background

Amine oxidase copper containing 1 (AOC1) is a gene whose biological function in colorectal cancer (CRC) has not been elucidated. Therefore, the purpose of this study was to investigate the clinical significance of AOC1 expression in CRC and its biological function in CRC cell lines.

Materials and Methods

AOC1 expression levels were examined in paired CRC and peritumoral tissues, and distant liver metastatic tissues were examined using quantitative real-time PCR, western blotting, and immunohistochemistry staining. The log-rank test and Cox regression model were used to analyze the relationship between AOC1 expression and prognosis. Proliferation assays (Cell Counting Kit‐8 and colony formation assays), migration assays (Transwell and wound healing assays) and xenograft tumor formation in nude mice were performed to assess the biological role of AOC1 in CRC cells.

Results

AOC1 expression significantly increased in human CRC tissues, especially in liver metastases, and was associated with a worse prognosis. In addition, AOC1 had higher expression in tumor organoids than in normal organoids, suggesting that it was highly expressed in the tumor epithelium. Functional analysis demonstrated that AOC1 knockdown inhibited the proliferation and migration of CRC cells by inducing EMT in vitro. Xenograft tumor formation in nude mice showed that knockdown of AOC1 inhibited the tumor xenografts growth in vivo.

Conclusion

High expression of AOC1 was significantly associated with worse clinical outcomes, was an independent risk factor for poor prognosis, and promoted aggressive CRC cell phenotypes. AOC1 is expected to become a novel biomarker for predicting the prognosis of patients with CRC and an effective therapeutic target in clinical practice.

Nonsense-mediated RNA decay and its bipolar function in cancer

Nonsense-mediated decay (NMD) was first described as a quality-control mechanism that targets and rapidly degrades aberrant mRNAs carrying premature termination codons (PTCs). However, it was found that NMD also degrades a significant number of normal transcripts, thus arising as a mechanism of gene expression regulation. Based on these important functions, NMD regulates several biological processes and is involved in the pathophysiology of a plethora of human genetic diseases, including cancer. The present review aims to discuss the paradoxical, pro- and anti-tumorigenic roles of NMD, and how cancer cells have exploited both functions to potentiate the disease. Considering recent genetic and bioinformatic studies, we also provide a comprehensive overview of the present knowledge of the advantages and disadvantages of different NMD modulation-based approaches in cancer therapy, reflecting on the challenges imposed by the complexity of this disease. Furthermore, we discuss significant advances in the recent years providing new perspectives on the implications of aberrant NMD-escaping frameshifted transcripts in personalized immunotherapy design and predictive biomarker optimization. A better understanding of how NMD differentially impacts tumor cells according to their own genetic identity will certainly allow for the application of novel and more effective personalized treatments in the near future.