Alternative Splicing Events and Their Clinical Significance in Colorectal Cancer: Targeted Therapeutic Opportunities.

Colorectal cancer (CRC) ranks as one of the top causes of cancer mortality worldwide and its incidence is on the rise, particularly in low-middle-income countries (LMICs). There are several factors that contribute to the development and progression of CRC. Alternative splicing (AS) was found to be one of the molecular mechanisms underlying the development and progression of CRC. With the advent of genome/transcriptome sequencing and large patient databases, the broad role of aberrant AS in cancer development and progression has become clear. AS affects cancer initiation, proliferation, invasion, and migration. These splicing changes activate oncogenes or deactivate tumor suppressor genes by producing altered amounts of normally functional or new proteins with different, even opposing, functions. Thus, identifying and characterizing CRC-specific alternative splicing events and variants might help in designing new therapeutic splicing disrupter drugs. CRC-specific splicing events can be used as diagnostic and prognostic biomarkers. In this review, alternatively spliced events and their role in CRC development will be discussed. The paper also reviews recent research on alternatively spliced events that might be exploited as prognostic, diagnostic, and targeted therapeutic indicators. Of particular interest is the targeting of protein arginine methyltransferase (PMRT) isoforms for the development of new treatments and diagnostic tools. The potential challenges and limitations in translating these discoveries into clinical practice will also be addressed.

Genomic Interplay between Neoneurogenesis and Neoangiogenesis in Carcinogenesis: Therapeutic Interventions.

Angiogenesis, the generation of new blood vessels, is one of the hallmarks of cancer. The growing tumor requires nutrients and oxygen. Recent evidence has shown that tumors release signals to attract new nerve fibers and stimulate the growth of new nerve fibers. Neurogenesis, neural extension, and axonogenesis assist in the migration of cancer cells. Cancer cells can use both blood vessels and nerve fibers as routes for cells to move along. In this way, neurogenesis and angiogenesis both contribute to cancer metastasis. As a result, tumor-induced neurogenesis joins angiogenesis and immunosuppression as aberrant processes that are exacerbated within the tumor microenvironment. The relationship between these processes contributes to cancer development and progression. The interplay between these systems is brought about by cytokines, neurotransmitters, and neuromodulators, which activate signaling pathways that are common to angiogenesis and the nervous tissue. These include the AKT signaling pathways, the MAPK pathway, and the Ras signaling pathway. These processes also both require the remodeling of tissues. The interplay of these processes in cancer provides the opportunity to develop novel therapies that can be used to target these processes.

Competing Endogenous RNA (ceRNA) Networks and Splicing Switches in Cervical Cancer: HPV Oncogenesis, Clinical Significance and Therapeutic Opportunities.

Cervical cancer (CC) is the primary cause of female cancer fatalities in low-middle-income countries (LMICs). Persistent infections from the human papillomavirus (HPV) can result in cervical cancer. However, numerous different factors influence the development and progression of cervical cancer. Transcriptomic knowledge of the mechanisms with which HPV causes cervical cancer pathogenesis is growing. Nonetheless, there is an existing gap hindering the development of therapeutic approaches and the improvement of patient outcomes. Alternative splicing allows for the production of numerous RNA transcripts and protein isoforms from a single gene, increasing the transcriptome and protein diversity in eukaryotes. Cancer cells exhibit astounding transcriptome modifications by expressing cancer-specific splicing isoforms. High-risk HPV uses cellular alternative splicing events to produce viral and host splice variants and proteins that drive cancer progression or contribute to distinct cancer hallmarks. Understanding how viruses utilize alternative splicing to drive pathogenesis and tumorigenesis is essential. Although research into the role of miRNAs in tumorigenesis is advancing, the function of other non-coding RNAs, including lncRNA and circRNA, has been understudied. Through their interaction with mRNA, non-coding RNAs form a network of competing endogenous RNAs (ceRNAs), which regulate gene expression and promote cervical cancer development and advancement. The dysregulated expression of non-coding RNAs is an understudied and tangled process that promotes cervical cancer development. This review will present the role of aberrant alternative splicing and immunosuppression events in HPV-mediated cervical tumorigenesis, and ceRNA network regulation in cervical cancer pathogenesis will also be discussed. Furthermore, the therapeutic potential of splicing disruptor drugs in cervical cancer will be deliberated.

Apoptosis in Cancer Cells Is Induced by Alternative Splicing of hnRNPA2/B1 Through Splicing of Bcl-x, a Mechanism that Can Be Stimulated by an Extract of the South African Medicinal Plant, Cotyledon orbiculata.

Alternative splicing is deregulated in cancer and alternatively spliced products can be linked to cancer hallmarks. Targeting alternative splicing could offer novel effective cancer treatments. We investigated the effects of the crude extract of a South African medicinal plant, Cotyledon orbiculata, on cell survival of colon (HCT116) and esophageal (OE33 and KYSE70) cancer cell lines. Using RNASeq, we discovered that the extract interfered with mRNA regulatory pathways. The extract caused hnRNPA2B1 to splice from the hnRNPB1 to the hnRNPA2 isoform, resulting in a switch in the BCL2L1 gene from Bcl-xL to Bcl-xS causing activation of caspase-3-cleavage and apoptosis. Similar splicing effects were induced by the known anti-cancer splicing modulator pladienolide B. Knockdown of hnRNPB1 using siRNA resulted in decreased cell viability and increased caspase-3-cleavage, and over-expression of hnRNPB1 prevented the effect of C. orbiculata extract on apoptosis and cell survival. The effect of the hnRNPA2/B1 splicing switch by the C. orbiculata extract increased hnRNPA2B1 binding to Bcl-xl/s, BCL2, MDM2, cMYC, CD44, CDK6, and cJUN mRNA. These findings suggest that apoptosis in HCT116, OE33, and KYSE cancer cells is controlled by switched splicing of hnRNPA2B1 and BCL2L1, providing evidence that hnRNPB1 regulates apoptosis. Inhibiting this splicing could have therapeutic potential for colon and esophageal cancers. Targeting hnRNPA2B1 splicing in colon cancer regulates splicing of BCL2L1 to induce apoptosis. This approach could be a useful therapeutic strategy to induce apoptosis and restrain cancer cell proliferation and tumor progression. Here, we found that the extract of Cotyledon orbiculata, a South African medicinal plant, had an anti-proliferative effect in cancer cells, mediated by apoptosis induced by alternative splicing of hnRNPA2B1 and BCL2L1.

VEGFR2 promotes central endothelial activation and the spread of pain in inflammatory arthritis.

Chronic pain can develop in response to conditions such as inflammatory arthritis. The central mechanisms underlying the development and maintenance of chronic pain in humans are not well elucidated although there is evidence for a role of microglia and astrocytes. However in pre-clinical models of pain, including models of inflammatory arthritis, there is a wealth of evidence indicating roles for pathological glial reactivity within the CNS. In the spinal dorsal horn of rats with painful inflammatory arthritis we found both a significant increase in CD11b+ microglia-like cells and GFAP+ astrocytes associated with blood vessels, and the number of activated blood vessels expressing the adhesion molecule ICAM-1, indicating potential glio-vascular activation. Using pharmacological interventions targeting VEGFR2 in arthritic rats, to inhibit endothelial cell activation, the number of dorsal horn ICAM-1+ blood vessels, CD11b+ microglia and the development of secondary mechanical allodynia, an indicator of central sensitization, were all prevented. Targeting endothelial VEGFR2 by inducible Tie2-specific VEGFR2 knock-out also prevented secondary allodynia in mice and glio-vascular activation in the dorsal horn in response to inflammatory arthritis. Inhibition of VEGFR2 in vitro significantly blocked ICAM-1-dependent monocyte adhesion to brain microvascular endothelial cells, when stimulated with inflammatory mediators TNF-α and VEGF-A165a. Taken together our findings suggest that a novel VEGFR2-mediated spinal cord glio-vascular mechanism may promote peripheral CD11b+ circulating cell transmigration into the CNS parenchyma and contribute to the development of chronic pain in inflammatory arthritis. We hypothesise that preventing this glio-vascular activation and circulating cell translocation into the spinal cord could be a new therapeutic strategy for pain caused by rheumatoid arthritis.