Pancreatic adenocarcinoma (PAAD) is a prevalent and highly malignant gastrointestinal tumor. Therefore, exploring the mechanisms of drug resistance and immune pathways in PAAD is crucial for clinical treatment. In this study, a total of 497 differentially expressed genes (DEGs) were identified between normal and PAAD samples, and which were enriched to 117 GO terms and 7 functional pathways. Subsequently, 5 overall survival-related DEGs (ESRP1, KRT6A, H2BC11, H2BC4 and KLK) was generated using Cox hazards regression analysis in TCGA dataset. Furthermore, the weighted gene co-expression network analysis revealed a strong association between ESRP1 and PAAD among 5 survival-related DEGs. Patients were divided into two clusters based on ESRP1 expression levels, and low ESRP1 expression existed stronger immune infiltration and higher expression of immunomodulatory targets than high ESRP1 expression by single-sample gene set enrichment analysis, which indicated that low ESRP1 expression was associated with longer survival compared to high ESRP1 expression. Finally, our study also found that immune cells distribution and immunomodulatory targets gene expression in the GEO dataset were similar to the TCGA cohort. Overall, our findings suggest that ESRP1 may play a role in influencing immune contexture and regulating immune function of PAAD patients by integrating data from various databases. SIGNIFICANCE: Utilizing TCGA and GEO datasets, this study uncovers the significant impact of epithelial splicing regulatory protein 1 (ESRP1) on PAAD. ESRP1 emerges as a key regulator of immune function, influencing tumor microenvironment and immune cell infiltration. Cluster analysis shows that low ESRP1 expression correlates with enhanced immune activity, predicting better prognosis. This discovery suggests that ESRP1 can serve as a potential biomarker for the prognosis of PAAD, offering new insights into personalized immunotherapy by influencing immune regulation and tumor progression.

OBJECTIVE: Epithelial splicing regulatory protein 1 (ESRP1) regulates tumor progression and metastasis through the epithelial‒mesenchymal transition by interacting with zinc finger E-box binding 1 (ZEB1) and CD44 in cancers. However, the role of ESRP1 in intrahepatic cholangiocarcinoma (iCCA) remains unclear.
METHODS: Three iCCA cell lines (HuCCT-1, SSP-25, and KKU-100) were analyzed using small interfering RNA to investigate the molecular biological functions of ESRP1 and ZEB1. The association between clinicopathological features and the expression of ESRP1 and ZEB1 in iCCA tissues was analyzed immunohistochemically. Proteomic analysis was performed to identify molecules related to ESRP1 expression.
RESULTS: ESRP1 expression was upregulated in HuCCT-1 and SSP-25 cells. Cell migration and invasion were enhanced, and the expression of ZEB1 and CD44s (CD44 standard) isoforms were upregulated in the ESRP1 silencing cells. Moreover, ESRP1 silencing increased the expression of N-cadherin and vimentin, indicating the presence of mesenchymal properties. Conversely, ZEB1 silencing increased the expression of ESRP1 and CD44v (CD44 variant) isoforms. Immunohistochemical analysis revealed that a lower ESRP1-to-ZEB1 expression ratio was associated with poor recurrence-free survival in patients with iCCA. Flotillin 2, a lipid raft marker related to epithelial‒mesenchymal transition, was identified as a protein related to the interactive feedback loop in proteomic analysis.
CONCLUSIONS: ESRP1 suppresses tumor progression in iCCA by interacting with ZEB1 and CD44 to regulate epithelial‒mesenchymal transition.

BACKGROUND: Emerging evidence indicates the pivotal involvement of circular RNAs (circRNAs) in cancer initiation and progression. Understanding the functions and underlying mechanisms of circRNAs in tumor development holds promise for uncovering novel diagnostic indicators and therapeutic targets. In this study, our focus was to elucidate the function and regulatory mechanism of hsa-circ-0003764 in hepatocellular carcinoma (HCC).
METHODS: A newly discovered hsa-circ-0003764 (circPTPN12) was identified from the circbase database. QRT-PCR analysis was utilized to assess the expression levels of hsa-circ-0003764 in both HCC tissues and cells. We conducted in vitro and in vivo experiments to examine the impact of circPTPN12 on the proliferation and apoptosis of HCC cells. Additionally, RNA-sequencing, RNA immunoprecipitation, biotin-coupled probe pull-down assays, and FISH were employed to confirm and establish the relationship between hsa-circ-0003764, PDLIM2, OTUD6B, P65, and ESRP1.
RESULTS: In HCC, the downregulation of circPTPN12 was associated with an unfavorable prognosis. CircPTPN12 exhibited suppressive effects on the proliferation of HCC cells both in vitro and in vivo. Mechanistically, RNA sequencing assays unveiled the NF-κB signaling pathway as a targeted pathway of circPTPN12. Functionally, circPTPN12 was found to interact with the PDZ domain of PDLIM2, facilitating the ubiquitination of P65. Furthermore, circPTPN12 bolstered the assembly of the PDLIM2/OTUD6B complex by promoting the deubiquitination of PDLIM2. ESRP1 was identified to bind to pre-PTPN12, thereby fostering the generation of circPTPN12.
CONCLUSIONS: Collectively, our findings indicate the involvement of circPTPN12 in modulating PDLIM2 function, influencing HCC progression. The identified ESRP1/circPTPN12/PDLIM2/NF-κB axis shows promise as a novel therapeutic target in the context of HCC.

Aberrant expression of circular RNAs (circRNAs) is frequently linked to colorectal cancer (CRC). Here, we identified circZFR as a promising biomarker for CRC diagnosis and prognosis. CircZFR was upregulated in CRC tissues and serum exosomes and its level was linked to cancer incidence, advanced-stages, and metastasis. In both in vitro and in vivo settings, circZFR promoted the growth and spread while suppressing apoptosis of CRC. Exosomes with circZFR overexpression promoted the proliferation and migration of cocultured CRC cells. Mechanistically, epithelial splicing regulatory protein 1 (ESRP1) in CRC cells may enhance the production of circZFR. BCL2-associated transcription factor 1 (BCLAF1) bound to circZFR, which prevented its ubiquitinated degradation. Additionally, circZFR sponged miR-3127-5p to boost rhotekin 2 (RTKN2) expression. Our TCP1-CD-QDs nanocarrier was able to carry and deliver circZFR siRNA (si-circZFR) to the vasculature of CRC tissues and cells, which inhibited the growth of tumors in patient-derived xenograft (PDX) models. Taken together, our results show that circZFR is an oncogenic circRNA, which promotes the development and spread of CRC in a BCLAF1 and miR-3127-5p-dependent manner. CircZFR is a possible serum biopsy marker for the diagnosis and a desirable target for further treatment of CRC.

Alternative splicing is often deregulated in cancer, and cancer-specific isoform switches are part of the oncogenic transformation of cells. Accumulating evidence indicates that isoforms of the multifunctional cell-surface glycoprotein CD44 play different roles in cancer cells as compared to normal cells. In particular, the shift of CD44 isoforms is required for epithelial to mesenchymal transition (EMT) and is crucial for the maintenance of pluripotency in normal human cells and the acquisition of cancer stem cells phenotype for malignant cells. The growing and seemingly promising use of splicing inhibitors for treating cancer and other pathologies gives hope for the prospect of using such an approach to regulate CD44 alternative splicing. This review integrates current knowledge about regulating CD44 alternative splicing by RNA-binding proteins.

Oral squamous cell carcinoma (OSCC) is a common malignancy in the oral and maxillofacial regions with an increasing incidence rate. Circular RNA (circRNA) is a recently discovered long-chain non-coding RNA family member. The objective of this study was to analyze the role of circ_0068162 in OSCC development.
We downloaded sample data GSE145608 from the Gene Expression Omnibus database. Online databases Starbase, TargetScan and miRDB were used to predict the target microRNAs (miRNAs) and genes. Cell viability and proliferation were assessed using the CCK-8 and EdU assays, respectively. Cell migration and invasion abilities were detected using transwell assay. The double luciferase reporter and RNA immunoprecipitation (RIP) assays were performed to verify the interaction relationship between the identified target molecules. RNase R and actinomycin D treatment were performed to analyze the stability of circ_0068162.
We found that circ_0068162 was overexpressed in the cytoplasm of OSCC cells and clinical OSCC tissues. Knockdown of circ_0068162 inhibited the growth, migration and invasion of OSCC cells. We also identified miR-186 as the target miRNA of circ_0068162, and JAG1 and JAG2 as the target genes of miR-186. The miR-186 inhibitor rescued the effects of sh-circ_0068162 and JAG1/JAG2 overexpression rescued the effects of miR-186 mimic in OSCC cells. Furthermore, ESRP1 promoted the biosynthesis of circ_0068162.
The circ_0068162/miR-186/JAGs/ESRP1 feedback loop is closely related to OSCC development.

OBJECTIVE: Gastric cancer (GC) is one of the most malignant tumors worldwide. Thus, it is necessary to explore the underlying mechanisms of GC progression and develop novel therapeutic regimens. Long non-coding RNAs (lncRNAs) have been demonstrated to be abnormally expressed and regulate the malignant behaviors of cancer cells. Our previous research demonstrated that lncRNA colon cancer-associated transcript 2 (CCAT2) has potential value for GC diagnosis and discrimination. However, the functional mechanisms of lncRNA CCAT2 in GC development remain to be explored.
METHODS: GC and normal adjacent tissues were collected to detect the expression of lncRNA CCAT2, ESRP1 and CD44 in clinical specimens and their clinical significance for GC patients. Cell counting kit-8, wound healing and transwell assays were conducted to investigate the malignant behaviors in vitro. The generation of nude mouse xenografts by subcutaneous, intraperitoneal and tail vein injection was performed to examine GC growth and metastasis in vivo. Co-immunoprecipitation, RNA-binding protein pull-down assay and fluorescence in situ hybridization were performed to reveal the binding relationships between ESRP1 and CD44.
RESULTS: In the present study, lncRNA CCAT2 was overexpressed in GC tissues compared to adjacent normal tissues and correlated with short survival time of patients. lncRNA CCAT2 promoted the proliferation, migration and invasion of GC cells. Its overexpression modulates alternative splicing of Cluster of differentiation 44 (CD44) variants and facilitates the conversion from the standard form to variable CD44 isoform 6 (CD44v6). Mechanistically, lncRNA CCAT2 upregulated CD44v6 expression by binding to epithelial splicing regulatory protein 1 (ESRP1), which subsequently mediates CD44 alternative splicing. The oncogenic role of the lncRNA CCAT2/ESRP1/CD44 axis in the promotion of malignant behaviors was verified by both in vivo and in vitro experiments.
CONCLUSIONS: Our findings identified a novel mechanism by which lncRNA CCAT2, as a type of protein-binding RNA, regulates alternative splicing of CD44 and promotes GC progression. This axis may become an effective target for clinical diagnosis and treatment.

Lung metastasis occurs in parts of the bladder carcinoma (BC) patients but represents the highest severity and a poor outcome of the disease. The molecular mechanism underlying lung metastasis of BC is not fully understood. Fibroblast growth factor receptor 2 (FGFR2) signaling plays a substantial role in the BC cell growth and invasion. In this study, we assessed the regulation of the alternative splicing of FGFR2 by epithelial splicing regulatory proteins (ESRPs) in lung metastasis of BC.
Gene profile of BC in comparison with adjacent non-tumor bladder tissue was obtained from GEO public database to analyze the levels of differentiated genes and pathways. Moreover, the association of ESRP1 or ESRP2 with lung metastasis of BC was analyzed on our own clinic samples. The effects of altered expression of ESRP1 or ESRP2 on alternative splicing of FGFR2 IIIb and IIIc, which represents epithelial and mesenchymal-like splicing, were analyzed on BC cell lines T24 and RT4. The in vivo effects of ESRP1 or ESRP2 on lung metastasis of BC were assessed in mice subcutaneously grafted with ESRP1/2-modified BC labeled with fluorescent and luciferase reporters.
We detected significant reduction of ESRP1 and ESRP2 in BC in public database of BC specimens. Moreover, analysis on our own specimens also showed strong downregulation of ESRP1 or ESRP2 in BC, and the latter was more pronounced in cases with lung metastasis. In vitro, altered levels of ESRP1 or ESRP2 caused a switch of FGFR2 splicing between FGFR2-IIIb and FGFR2-IIIc, resulting in changes in tumor cell growth and metastatic potential. In vivo, re-expression of ESRP1 or ESRP2 in BC cells not only inhibited the growth of the xenografted tumor formation in nude mice, but also reduced the occurrence of lung metastasis, partially through altering polarization of tumor-associated macrophages.
Our data thus suggest that reduction in ESRP1 or ESRP2 promotes lung metastasis of BC through altering FGFR2 splicing and macrophage polarization.

Resistance to hormone therapy leads to a recurrence of estrogen receptor-positive breast cancer. We have demonstrated that the epithelial splicing regulatory protein 1 (ESRP1) significantly affects cell/tumor growth and metabolism and is associated with a poor prognosis in this breast cancer subtype. In this study, we aimed to investigate the ESRP1 protein-messenger RNA (mRNA) interaction in hormone therapy-resistant breast cancer. RNA-binding protein immunoprecipitation (RIP) followed by Clariom D (Applied Biosystems/Thermo Fisher Scientific) transcriptomics microarray (RIP-Chip) was performed to identify mRNA-binding partners of ESRP1. The integration of RIP-Chip and immunoprecipitation-mass spectrometry analyses identified phosphoglycerate dehydrogenase (PHGDH), a key metabolic enzyme, as a binding partner of ESRP1 in hormone-resistant breast cancer. Bioinformatic analysis showed ESRP1 binding to the 5\' untranslated region of PHGDH. RNA electrophoresis mobility shift assay and RIP-quantitative reverse transcription-polymerase chain reaction further validated the ESRP1-PHGDH binding. In addition, knockdown of ESRP1 decreased PHGDH mRNA stability significantly, suggesting the posttranscriptional regulation of PHGDH by ESRP1. The presence or absence of ESRP1 levels significantly affected the stability in tamoxifen-resistant LCC2 and fulvestrant-resistant LCC9 cells. PHGDH knockdown in tamoxifen-resistant cells further reduced the oxygen consumption rate (ranging from P = .005 and P = .02), mimicking the effects of ESRP1 knockdown. Glycolytic parameters were also altered (ranging P = .001 and P = .005). ESRP1 levels did not affect the stability of PHGDH in T-47D cells, although knockdown of PHGDH affected the growth of these cells. In conclusion, to our knowledge, this study, for the first time, reports that ESRP1 binds to the 5\' untranslated region of PHGDH, increasing its mRNA stability in hormone therapy-resistant estrogen receptor-positive breast cancer. These findings provide evidence for a novel mechanism of action of RNA-binding proteins such as ESRP1. These new insights could assist in developing novel strategies for the treatment of hormone therapy-resistant breast cancer.

Severe corneal damage leads to complete vision loss, thereby affecting life quality and impinging heavily on the healthcare system. Current clinical approaches to manage corneal wounds suffer from severe drawbacks, thus requiring the development of alternative strategies. Of late, mesenchymal stromal/stem cell (MSC)-derived extracellular vesicles (EVs) have become a promising tool in the ophthalmic field. In the present study, we topically delivered bone-marrow-derived MSC-EVs (BMSC-EVs), embedded in methylcellulose, in a murine model of alkali-burn-induced corneal damage in order to evaluate their role in corneal repair through histological and molecular analyses, with the support of magnetic resonance imaging. Our data show that BMSC-EVs, used for the first time in this specific formulation on the damaged cornea, modulate cell death, inflammation and angiogenetic programs in the injured tissue, thus leading to a faster recovery of corneal damage. These results were confirmed on cadaveric donor-derived human corneal epithelial cells in vitro. Thus, BMSC-EVs modulate corneal repair dynamics and are promising as a new cell-free approach for intervening on burn wounds, especially in the avascularized region of the eye.