Biology subjects

Oltean, S.

Publications and source records attributed to Oltean, S..

10 recordsLinked to original sources

bioRxiv2026

SRPK1 is a determinant of chemoresistance to Docetaxel in prostate cancer

Docetaxel is a major therapeutic option for advanced prostate cancer, but the development of acquired resistance substantially limits its clinical efficacy. Although multiple mechanisms have been implicated in docetaxel resistance, the upstream regulatory pathways coordinating these phenotypes remain incompletely understood. Here, we investigated the role of serine/arginine-rich protein kinase 1 (SRPK1), a key regulator of pre-mRNA splicing, in acquired docetaxel resistance in prostate cancer. Docetaxel-resistant PC3 cells showed increased SRPK1 expression at both the protein and RNA levels. Genetic depletion or pharmacological inhibition of SRPK1 substantially restored docetaxel sensitivity, whereas ectopic SRPK1 expression in parental PC3 cells increased resistance. Mechanistically, SRPK1 inhibition reduced expression of {beta}III-tubulin and restored docetaxel-induced microtubule bundling. SRPK1 inhibition also increased apoptosis in resistant cells, accompanied by increased cleavage of caspase-8, caspase-9 and PARP. In parallel, SRPK1 inhibition restored E-cadherin expression and reduced the enhanced migratory phenotype of resistant cells. At the signalling and RNA-processing levels, docetaxel-resistant cells exhibited increased EGFR expression and increased phosphorylation of the SRPK1 substrate SRSF1. SRSF1 depletion partially restored docetaxel sensitivity, supporting an EGFR-SRPK1-SRSF1 pathway in resistance. Importantly, inhibition of SRPK1 or depletion of SRSF1 altered the splicing of apoptosis- and microtubule-associated genes, increasing the pro-apoptotic Bcl-xS and MCL-1S isoforms and shifting tau splicing towards 3R at the expense of 4R. Collectively, these findings identify SRPK1 as a central regulator of multiple phenotypic and molecular features of docetaxel resistance in prostate cancer. Targeting SRPK1-dependent splicing may therefore represent a strategy to re-sensitize resistant prostate cancer cells to docetaxel.

cancer biology↗

bioRxiv2025

Mechanistic analysis of compounds that modulate VEGF-A splicing in podocytes with therapeutic potential for diabetic nephropathy

Vascular endothelial growth factor A (VEGF-A) has an alternatively spliced variant, VEGF-A165b, formed when a distal 3 splice site in exon 8 is selected. The anti-angiogenic and anti-permeability VEGF-A165b has reno-protective properties and has been shown to rescue kidney function in diabetic nephropathy (DN) mouse models (PMID 25542969). We previously identified three new compounds that can increase the expression of the VEGF-A165b isoform. Two of these compounds, named ESSO1 and ESSO3, were discovered through a screen of synthetic compounds that alter VEGF-A splicing (PMID 33941763). A third compound, delphinidin, was found to be the key regulator of VEGF-A splicing in a natural blueberry and sea-buckthorn extract (DIAVIT) (PMID 30865689). This study aimed to investigate the signalling mechanism through which these three compounds regulate VEGF-A splicing and increase the protective VEGF-A165b isoform in renal podocytes. Human podocytes were exposed to a diabetic environment (glucose soup [GS]: 25 mM glucose, 1 ng/ml TNF-, 1 ng/ml IL-6, and 100 nM insulin), in comparison to a normal glucose (5.5 mM glucose) and an osmotic control (5.5 mM glucose + 19.5 mM mannitol) control, for 48 hours. RNA and protein were extracted for RT-PCR and Western blotting analysis of splice isoforms. Immunofluorescence and cell viability assays were also used. Immunofluorescence showed no significant difference in nephrin expression for all treatments compared to control, suggesting that normal podocyte function is not affected by these compounds. Trypan blue exclusion assay, used to assess the percentage cell viability of podocyte cells, showed that they do not affect podocyte cell viability. By using various inhibitor treatments, we have found several molecules involved in signalling, like JNK and splicing kinases SRPK1 and CLK1 for ESSO1, splicing factor hnRNPH and kinase CLK1 for ESSO3 and AMPK, splicing factor SRSF6 and kinase CLK1 for delphinidin. Other molecules, like ATM, E2F1, and hnRNPA1, were ruled out. Interestingly, all three compounds significantly increased expression of the splicing kinase CLK1, which has been involved in VEGF-A splicing regulation, suggesting that all three compounds may be increasing the VEGF-A165b/panVEGF-A165 ratio through signalling through this kinase. Studies of human biopsies showed that CLK1 is downregulated in DN patients compared to healthy volunteers. The development of a CLK1 activator as a DN therapy seems, therefore, a plausible opportunity.

pharmacology and toxicology↗

bioRxiv2025

Clinical Implications of SRPK1 Expression in Human Tumours: A Comprehensive Pan-Cancer Analysis Based on Multi-Omics Databases

Serine/arginine-rich protein kinase 1 (SRPK1), which primarily regulates alternative splicing (AS), has been implicated in various malignancies. However, the comprehensive expression landscape and clinical relevance of SRPK1 across diverse tumour types have not been systematically investigated. Chemoresistance remains a formidable obstacle in cancer treatment, accounting for nearly 90% of treatment failures and leading to poor patient survival. Aberrant AS, often driven by splicing factors like SRPK1, is a mechanism cancer cells exploit to overcome chemotherapy-induced cytotoxicity. With that, this study tested the hypothesis of tumour-specific alterations in SRPK1 expression as novel therapeutic targets through a pan-cancer analysis of SRPK1 using multi-omics data, obtained from public databases, including TCGA, CPTAC, GEPIA2, and drug sensitivity platforms. The analysis specifically assessed the pan-cancer expression landscape of SRPK1 at the mRNA and protein levels and its prognostic implications across different cancer types (breast, colon, and prostate cancers), functional analysis of SRPK1-associated splicing network, and its expression in correlation with predicted drug sensitivity. The results revealed the correlations of high SRPK1 expression with worse overall and disease-free survival in a cancer-specific manner and resistance to standard-of-care agents like cisplatin and docetaxel. The integrative multi-omics approach in this study provided a robust foundation for understanding the complex, multifaceted role of SRPK1 in tumour-specific chemoresistance.

bioinformatics↗

bioRxiv2025

Modulators of epithelial-mesenchymal transitions in prostate cancer: potential for novel therapeutics development

Research in the area of hallmarks of cancer has opened the possibility of designing novel therapeutic interventions based on modulating cancer properties. Interestingly, the epithelial-mesenchymal transition (EMT), important in both tumour growth and metastasis, has not been targeted in prostate cancer (PCa). Previously, in a repositioning screen, three new chemicals that modulate EMT in PCa (named LLSOs) have been found. This study aims to investigate how they work mechanistically as well as the effect of these LLSOs on the properties of PCa cells both in vitro and in vivo. Although LLSOs exhibited varying effects on different cancer cell lines, all of them modulated EMT by inhibiting the migration of PCa cells. LLSO3 also exhibited a significant inhibitory effect on tumour growth in vivo, concomitant with an increase in the expression levels of E-cadherin. Further investigation was conducted to obtain mechanistic insights into the LLSO compounds mode of action. In conclusion, our work strongly supports that LLSO compounds may become important candidates for targeted therapeutics in prostate cancer.

cancer biology↗

bioRxiv2025

The apoptosis gene BCL-X splice isoforms have opposing effects in diabetic kidney disease: potential treatment target and prognostic value

In recent years, the importance of alternative splicing (AS) of certain genes in the nature and progression of diabetic nephropathy (DN) has been studied. We report a novel AS event observed in the diabetic kidney - AS of the apoptosis gene BCL-X to increase the pro-apoptotic BCL-XS and decrease the anti-apoptotic BCL-XL. This study aimed to further investigate the role of this novel AS event in the pathogenesis of DN. To characterize important splicing events in progression of DN, human glomerular endothelial cells (GEnCs) were exposed to a diabetic environment for 1 week and RNAseq was performed. While several splicing changes have been discovered we have focused further on the apoptosis gene BCL-X isoforms. In GEnCs, an upregulation of the BCL-XS/BCL-XL ratio was observed which resulted in an increase in GEnC apoptosis. An upregulation of IL-6 was also observed; treatment with IL-6 alone induced a dose-dependent shift in BCL-X splicing to promote expression of the pro-apoptotic BCL-XS. Furthermore, we identified certain splicing factors, SF3B1 and PTBP1, involved in the BCL-X splicing regulation. A switch in expression of the anti-apoptotic BCL-XL isoform rescues apoptosis, suggesting a possible therapeutic avenue. In patients, an increase in the pro-apoptotic BCL-XS in urinary RNA correlated with a decline in the GFR, while in blood it correlated with the level of albuminuria. There is an increase in the pro-apoptotic BCL-XS isoform in the diabetic glomerular endothelium, resulting in increased GEnC apoptosis. Increased BCL-XS expression correlates with a markers of renal function decline, implicating this AS event as a potential biomarker for DN severity and suggesting that the switch of isoforms from BCL-XS to BCL-XL may for a novel therapeutic strategy.

molecular biology↗

bioRxiv2025

A novel combinatorial treatment for Neurofibromatosis type 1 tumours revealed through cross-species genetic analysis

Neurofibromatosis type 1 (NF1) is a multisystem genetic disorder associated with a wide range of symptoms, including the formation of tumours along nerves. These tumours can affect nerve function, leading to pain and loss of sensory or motor capacity. Drug treatments are currently limited, and relatively few new targets have emerged for NF1 tumors despite intensive research. Therefore, new drugs to target NF1-deficient tumour cells are urgently required. Here, we have used a cross-species screening strategy combined with bioinformatic analysis to identify candidates with a high chance of successful translation to humans. First, we used data from a synthetic lethal screen performed in Drosophila cells to identify novel drug targets of NF1. Then, we performed statistical enrichment analysis of the screen results to identify further candidate targets that were not conserved between Drosophila and humans and could not have been found in the screen. We identified and validated hTERT as a synthetic lethal partner gene to NF1 with high potential as a therapeutic drug target, using the FDA-approved inhibitor azidothymidine (AZT). The lethal effect of AZT was validated in peripheral neurofibroma NF1-deficient human cell lines and NF1-deficient malignant peripheral nerve sheath tumour cells. The effect of AZT was also conserved in vivo, highlighting the translational potential; treatment of mice with AZT inhibited NF1 mutant xenograft growth to the same extent as the current clinically approved MEK inhibitor, selumetinib. Finally, we show that combined treatment with AZT and selumetinib resulted in a further synergistic reduction in NF1-deficient human cell viability. In conclusion, AZT represents a promising novel therapeutic for the treatment of NF1 tumours, either alone or in combination with selumetinib.

cancer biology↗

bioRxiv2024

The insulin / IGF axis is critically important controlling gene transcription in the podocyte.

Signalling to the podocyte via the structurally related insulin receptor (IR) or insulin-like growth factor 1 receptor (IGF1R) is important for podocyte function. This study sought to elucidate the compound role of the insulin/IGF1 axis in podocytes using transgenic mice and cell culture models deficient in both receptors. Podocyte specific IR/IGF1R knockdown mice developed a severe kidney phenotype with albuminuria, glomerulosclerosis and renal failure with death occurring in some mice between 4 and 24 weeks. Simultaneous knockdown of both receptors in cultured podocytes resulted in >50% cell death by 7 days. Proteomic analysis revealed a striking downregulation of spliceosome-related proteins in IR/IGF1R knockdown podocytes with long-read RNA sequence data indicating an increased fraction of transcripts with intron retention/premature termination codons in these cells. Furthermore, phospho-proteomic analysis revealed multiple insulin / IGF1 induced spliceosomal post-translational protein and kinase modifications suggesting dynamic control of this system. This study underlines the importance of podocyte insulin/IGF signalling demonstrating a novel role for this extrinsic hormonal signalling axis in regulating gene transcription in this cell type.

cell biology↗

bioRxiv2024

The splicing factor kinase SRPK1 is a therapeutic target for Peripheral Vascular Disease

IntroductionIn peripheral arterial disease (PAD) anti-angiogenic VEGF-A165b isoform overexpression in monocytes contributes to impaired collateralisation. Serine-arginine protein-kinase-1 (SRPK1) regulates VEGF splicing. To determine whether SRPK1 controlled monocytic VEGF, impairing collateralisation, we investigated SRPK1 inhibition and monocyte-specific knockout in mouse models of and in human monocytes from PAD. MethodsVEGF-A165b activity was measured by co-culture of PAD patients monocytes with endothelial cells with SRPK1 inhibition. Mice with impaired revascularisation due to soluble-frizzled-related-protein-5 knockout (Sfrp5-/-), monocyte-specific Wnt5a gain-of-function (LysM-Wnt5aGOF), or obese mice on a high-fat high-sucrose (HF/HS) diet were subjected to femoral artery ligation and treated with SRPK1 inhibitor. We generated an SRPK1 conditional knockout and crossed it with monocyte-specific (LysM-Cre) driver line to specifically knockout SRPK1 in monocyte lineages. Blood flow was measured by Laser Speckle Imaging before, and for 28 days after surgery. ResultsMonocytes from PAD patients significantly inhibited endothelial cell migration, which was reversed by an anti-VEGF-A165b antibody. Surprisingly, migration was stimulated by SRPK1 inhibition, switching splicing from VEGF-A165b to VEGF-A165a. In Sfrp5-/-, LysM-Wnt5aGOF and HF/HS mouse models of PAD, blood flow was improved by SRPK1 inhibition. Impaired revascularisation in LysM-Wnt5aGOF mice was rescued in LysM-Wnt5aGOF:SRPK1MoKO mice, which had a phenotypic shift towards M2 macrophages. Impaired blood flow recovery was also rescued in obese-SRPK1MoKO mice. ConclusionVEGF splicing in monocytes is regulated differently from VEGF splicing in epithelial or cancer cells suggesting that control of splicing is dependent on cell type and/or environment. SRPK1 inhibition enhances collateralisation in mice, and in human in vitro models of monocyte-dependent impaired angiogenesis. New and NoteworthyA novel potential treatment for peripheral arterial disease (PAD) is described. Inhibition of SRPK1, or knockout in monocytes, induces angiogenesis by preventing splicing to anti-angiogenic VEGF (VEGF-A165b) in patients and animal models. In PAD, monocyte splicing control is different from other cell types and SRPK1 inhibition by drug like compounds can alter macrophage phenotype and reverse PAD in mice using a new cell specific SRPK1-LoxP mouse.

physiology↗

bioRxiv2020

The epithelial splicing regulator ESRP2 is epigenetically repressed by DNA hypermethylation in Wilms tumour and acts as a tumour suppressor

Wilms tumour (WT), a childhood kidney cancer with embryonal origins, has been extensively characterised for genetic and epigenetic alterations, but a proportion of WTs still lack identifiable abnormalities. To uncover DNA methylation changes critical for WT pathogenesis, we compared the epigenome of fetal kidney with two WT cell lines, using methyl-CpG immunoprecipitation. We filtered our results to remove common cancer-associated epigenetic changes, and to enrich for genes involved in early kidney development. This identified four candidate genes that were hypermethylated in WT cell lines compared to fetal kidney, of which ESRP2 (epithelial splicing regulatory protein 2), was the most promising gene for further study. ESRP2 was commonly repressed by DNA methylation in WT, and this was shown to occur early in WT development (in nephrogenic rests). ESRP2 expression could be reactivated by DNA methyltransferase inhibition in WT cell lines. When ESRP2 was overexpressed in WT cell lines, it acted as an inhibitor of cellular proliferation in vitro, and in vivo it suppressed tumour growth of orthotopic xenografts in nude mice. RNA-seq of the ESRP2-expressing WT cell lines identified several novel splicing targets, in addition to well-characterised targets of ESRP2. We propose a model in which the mesenchymal to epithelial transition that is essential for early kidney development, can be disrupted in to generate WT, either by genetic abnormalities such as WT1 mutations, or by epigenetic defects, such as ESRP2 methylation.

cancer biology↗

bioRxiv2019

Androgen-regulated transcription of ESRP2 drives alternative splicing patterns in prostate cancer

Prostate is the most frequent cancer in men. Prostate cancer progression is driven by androgen steroid hormones, and delayed by androgen deprivation therapy (ADT). Androgens control transcription by stimulating androgen receptor (AR) activity, yet also control pre-mRNA splicing through less clear mechanisms. Here we find androgens regulate splicing through AR-mediated transcriptional control of the epithelial-specific splicing regulator ESRP2. Both ESRP2 and its close paralog ESRP1 are highly expressed in primary prostate cancer. Androgen stimulation induces splicing switches in many endogenous ESRP2-controlled mRNA isoforms, including a key splicing switch in the metastatic regulator FLNB which is associated with disease relapse. ESRP2 expression in clinical prostate cancer is repressed by ADT, which may thus inadvertently dampen epithelial splice programmes. Supporting this, FLNB splicing was reciprocally switched by the AR antagonist bicalutamide (Casodex(R)). Our data reveal a new mechanism of splicing control in prostate cancer with important implications for metastatic disease progression.\n\nKey pointsO_LITranscriptional regulation of ESRP2 by the androgen receptor controls splice isoform patterns in prostate cancer cells.\nC_LIO_LISplicing switches regulated by the androgen-ESRP2 axis include a splice isoform in the FLNB gene that is a known metastatic driver.\nC_LIO_LIBoth ESRP1 and ESRP2 are highly expressed in prostate cancer tissue.\nC_LIO_LIEctopic expression of ESRP1 and 2 inhibits prostate cancer cell growth.\nC_LIO_LIBy repressing ESRP2 expression androgen deprivation therapy (ADT) may dampen epithelial splicing programmes to inadvertently prime disease progression towards metastasis.\nC_LI

molecular biology↗