Serine-Arginine Protein Kinase 1 (SRPK1): a systematic review of its multimodal role in oncogenesis

SATB2 Expression Affects Chemotherapy Metabolism and Immune Checkpoint Gene Expression in Colorectal Cancer

BACKGROUND

Special AT-rich binding protein-2 (SATB2) is a nuclear matrix associated protein regulating gene expression which is normally expressed in colonic tissue. Loss of SATB2 expression in colorectal cancer (CRC) has negative implications for prognosis and has been associated with chemotherapy resistance. Furthermore, recent evidence suggests SATB2 may influence immune checkpoint (IC) expression. We hypothesized that SATB2 expression may be associated with altered expression of chemotherapy resistance associated and IC genes.

METHODS

Clinicopathologic and gene expression data were extracted from The Cancer Genome Atlas PanCancer Atlas. SATB2 expression was compared by clinicopathologic characteristic and by using multivariate regression analysis to explore associations with chemotherapy and IC gene expression.

RESULTS

About 553 patients were included for analysis. Lower quartile SATB2 expression was associated with worse disease specific survival (P = .04). MSI (P < .001) and mucinous (P < .001) tumors were associated with reduced SATB2 expression independently. SATB2 varied by consensus molecular subtype (P < .001) and was lowest in CMS1. On multivariate analysis, SATB2 was negatively associated with 5-FU related metabolism genes, while more complex but significant relationships were seen with oxaliplatin and irinotecan related genes. Low SATB2 expression was associated with increased expression of PD-1, PD-L1, TIM-3 and CTLA-4 IC genes.

CONCLUSION

The positive prognostic influence of SATB2 expression is reaffirmed in this study. This effect may be explained by the negative association between SATB2 and 5-FU-resistance related gene expression. Enhanced IC gene expression in SATB2 low cases suggests a potential role for IC inhibition in this setting, but further study is required.

CDK12-inactivation-induced MYC signaling causes dependency on the splicing kinase SRPK1

Inactivation of cyclin-dependent kinase 12 (CDK12) characterizes an aggressive sub-group of castration-resistant prostate cancer (CRPC). Hyper-activation of MYC transcription factor is sufficient to confer the CRPC phenotype. Here, we show that loss of CDK12 promotes MYC activity, which renders the cells dependent on the otherwise non-essential splicing regulatory kinase SRSF protein kinase 1 (SRPK1). High MYC expression is associated with increased levels of SRPK1 in patient samples, and overexpression of MYC sensitizes prostate cancer cells to SRPK1 inhibition using pharmacological and genetic strategies. We show that Endovion (SCO-101), a compound currently in clinical trials against pancreatic cancer, phenocopies the effects of the well-characterized SRPK1 inhibitor SRPIN340 on nascent transcription. This is the first study to show that Endovion is an SRPK1 inhibitor. Inhibition of SRPK1 with either of the compounds promotes transcription elongation, and transcriptionally activates the unfolded protein response. In brief, here we discover that CDK12 inactivation promotes MYC signaling in an SRPK1-dependent manner, and show that the clinical grade compound Endovion selectively targets the cells with CDK12 inactivation.

Therapeutic targeting of TGF-β in lung cancer

Transforming growth factor-β (TGF-β) plays a complex role in lung cancer pathophysiology, initially acting as a tumor suppressor by inhibiting early-stage tumor growth. However, its role evolves in the advanced stages of the disease, where it contributes to tumor progression not by directly promoting cell proliferation but by enhancing epithelial-mesenchymal transition (EMT) and creating a conducive tumor microenvironment. While EMT is typically associated with enhanced migratory and invasive capabilities rather than proliferation per se, TGF-β's influence on this process facilitates the complex dynamics of tumor metastasis. Additionally, TGF-β impacts the tumor microenvironment by interacting with immune cells, a process influenced by genetic and epigenetic changes within tumor cells. This interaction highlights its role in immune evasion and chemoresistance, further complicating lung cancer therapy. This review provides a critical overview of recent findings on TGF-β's involvement in lung cancer, its contribution to chemoresistance, and its modulation of the immune response. Despite the considerable challenges encountered in clinical trials and the development of new treatments targeting the TGF-β pathway, this review highlights the necessity for continued, in-depth investigation into the roles of TGF-β. A deeper comprehension of these roles may lead to novel, targeted therapies for lung cancer. Despite the intricate behavior of TGF-β signaling in tumors and previous challenges, further research could yield innovative treatment strategies.

SRPK1 Promotes Glioma Proliferation, Migration, and Invasion through Activation of Wnt/β-Catenin and JAK-2/STAT-3 Signaling Pathways

Currently, the treatment of gliomas still relies primarily on surgery and radiochemotherapy. Although there are various drugs available, including temozolomide, the overall therapeutic effect is unsatisfactory, and the prognosis remains poor. Therefore, the in-depth study of the mechanism of glioma development and a search for new therapeutic targets are the keys to improving the therapeutic treatment of gliomas and improving the prognosis of patients. Immunohistochemistry is used to detect the expression of relevant molecules in tissues, qPCR and Western blot are used to detect the mRNA and protein expression of relevant molecules, CCK-8 (Cell Counting Kit-8) is used to assess cell viability and proliferation capacity, Transwell is used to evaluate cell migration and invasion ability, and RNA transcriptome sequencing is used to identify the most influential pathways. SRPK1 (SRSF protein kinase 1) is highly expressed in gliomas but is not expressed in normal tissues. Its expression is positively correlated with the grades of gliomas and negatively correlated with prognosis. SRPK1 significantly promotes the occurrence and development of gliomas. Knocking down SRPK1 leads to a significant decrease in the proliferation, migration, and invasion abilities of gliomas. Loss of SRPK1 expression induces G2/M phase arrest and mitotic catastrophe, leading to apoptosis in cells. Overexpression of SRPK1 activates the Wnt/β-catenin (wingless-int1/β-catenin) and JAK-2/STAT-3 (Janus kinase 2/signal transducer and activator of transcription 3) signaling pathways, promoting the proliferation, migration, and invasion of gliomas. Overexpression of SRPK1 rescues the reduced cell proliferation, migration, and invasion abilities caused by the silencing of β-catenin or JAK-2. A stable shRNA-LN229 cell line was constructed, and using a nude mouse model, it was found that stable knockout of SRPK1 significantly reduced the tumorigenic ability of glioma cells, as evidenced by a significant decrease in the subcutaneous tumor volume and weight in nude mice. We have demonstrated that SRPK1 is highly expressed in gliomas. Overexpression of SRPK1 activates the Wnt/β-catenin and JAK-2/STAT-3 signaling pathways, promoting the proliferation, migration, and invasion of gliomas. Silencing SRPK1-related signaling pathways may provide potential therapeutic options for glioma patients.

Functions of SRPK, CLK and DYRK kinases in stem cells, development, and human developmental disorders

Human developmental disorders encompass a wide range of debilitating physical conditions and intellectual disabilities. Perturbation of protein kinase signalling underlies the development of some of these disorders. For example, disrupted SRPK signalling is associated with intellectual disabilities, and the gene dosage of DYRKs can dictate the pathology of disorders including Down's syndrome. Here, we review the emerging roles of the CMGC kinase families SRPK, CLK, DYRK, and sub-family HIPK during embryonic development and in developmental disorders. In particular, SRPK, CLK, and DYRK kinase families have key roles in developmental signalling and stem cell regulation, and can co-ordinate neuronal development and function. Genetic studies in model organisms reveal critical phenotypes including embryonic lethality, sterility, musculoskeletal errors, and most notably, altered neurological behaviours arising from defects of the neuroectoderm and altered neuronal signalling. Further unpicking the mechanisms of specific kinases using human stem cell models of neuronal differentiation and function will improve our understanding of human developmental disorders and may provide avenues for therapeutic strategies.

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.

Serine-arginine protein kinases and their targets in viral infection and their inhibition

Accumulating evidence has consolidated the interaction between viral infection and host alternative splicing. Serine-arginine (SR) proteins are a class of highly conserved splicing factors critical for the spliceosome maturation, alternative splicing and RNA metabolism. Serine-arginine protein kinases (SRPKs) are important kinases that specifically phosphorylate SR proteins to regulate their distribution and activities in the central pre-mRNA splicing and other cellular processes. In addition to the predominant SR proteins, other cytoplasmic proteins containing a serine-arginine repeat domain, including viral proteins, have been identified as substrates of SRPKs. Viral infection triggers a myriad of cellular events in the host and it is therefore not surprising that viruses explore SRPKs-mediated phosphorylation as an important regulatory node in virus-host interactions. In this review, we briefly summarize the regulation and biological function of SRPKs, highlighting their involvement in the infection process of several viruses, such as viral replication, transcription and capsid assembly. In addition, we review the structure-function relationships of currently available inhibitors of SRPKs and discuss their putative use as antivirals against well-characterized viruses or newly emerging viruses. We also highlight the viral proteins and cellular substrates targeted by SRPKs as potential antiviral therapeutic candidates.