Explore the vast range of titles available.

Circular RNAs (circRNAs) have emerged as key regulators of human cancers, yet their modes of action in gastric cancer (GC) remain largely unknown. Here, we identified circURI1 back-spliced from exons 3 and 4 of unconventional prefoldin RPB5 interactor 1 (URI1) from circRNA profiling of five-paired human gastric and the corresponding nontumor adjacent specimens (paraGC). CircURI1 exhibits the significantly higher expression in GC compared with paraGC and inhibitory effects on cell migration and invasion in vitro and GC metastasis in vivo. Mechanistically, circURI1 directly interacts with heterogeneous nuclear ribonucleoprotein M (hnRNPM) to modulate alternative splicing of genes, involved in the process of cell migration, thus suppressing GC metastasis. Collectively, our study expands the current knowledge regarding the molecular mechanism of circRNA-mediated cancer metastasis via modulating alternative splicing.

Alternative splicing has been shown to causally contribute to the epithelial–mesenchymal transition (EMT) and tumor metastasis. However, the scope of splicing factors that govern alternative splicing in these processes remains largely unexplored. Here we report the identification of A-Kinase Anchor Protein (AKAP8) as a splicing regulatory factor that impedes EMT and breast cancer metastasis. AKAP8 not only is capable of inhibiting splicing activity of the EMT-promoting splicing regulator hnRNPM through protein–protein interaction, it also directly binds to RNA and alters splicing outcomes. Genome-wide analysis shows that AKAP8 promotes an epithelial cell state splicing program. Experimental manipulation of an AKAP8 splicing target CLSTN1 revealed that splice isoform switching of CLSTN1 is crucial for EMT. Moreover, AKAP8 expression and the alternative splicing of CLSTN1 predict breast cancer patient survival. Together, our work demonstrates the essentiality of RNA metabolism that impinges on metastatic breast cancer. Splice isoform switching regulated by the heterogeneous nuclear ribonucleoprotein M (hnRNPM) induces EMT and metastasis. Here, the authors report that AKAP8 is a metastasis suppressor that inhibits the splicing activity of hnRNPM and antagonizes genome-wide EMT-associated alternative splicing to maintain epithelial cell state.

Background Heterogeneous nuclear ribonucleoprotein M (HnRNPM) is a key splicing factor involved in various biological processes, including the epithelial‒mesenchymal transition and cancer development. Alternative splicing is widely involved in the process of spermatogenesis. However, the function of hnRNPM as a splicing factor during spermatogenesis remains unknown. Methods The expression of hnRNPM in germ cells at different stages was detected by polymerase chain reaction, western blotting, a single-cell database, and chromosome spreading assays. Conditional hnRNPM knockout mice were generated to observe the development of testes and germ cells in male mice. Histological staining, immunofluorescence staining and transmission electron microscopy were used to observe the abnormal development of sperm from conditional hnRNPM-deficient mice. Coimmunoprecipitation and mass spectrometry analyses revealed the proteins that interact with hnRNPM. RNA sequencing was performed to analyse the different alternative splicing events in the testes of control and hnRNPM-deficient mice. Results In this study, we revealed that hnRNPM is highly expressed in spermatocytes and round spermatids, with the exception of XY bodies and metaphase. Therefore, we generated a germ cell-specific hnRNPM conditional knockout mouse model to investigate the role of hnRNPM in spermatogenesis. A lack of hnRNPM led to male infertility under natural conditions. Male hnRNPM-deficient mice presented lower numbers of sperm, lower motility, significantly more malformed sperm and even tailless sperm. Moreover, we found that hnRNPM interacted with PTBP1 to collectively regulate the process of spermatogenesis. In addition, we found that hnRNPM deficiency caused 1617 different alternative splicing events, and we detected abnormal exon skipping events in Cep152, Cyld, Inpp4b and Cd59b. Conclusions Together, our results suggest that hnRNPM regulates the alternative splicing of mRNAs during spermatogenesis by recruiting PTBP1 and is required for male mouse fertility.

High spliceosome activity is a dependency for cancer cells, making them more vulnerable to perturbation of the splicing machinery compared to normal cells. To identify splicing factors important for prostate cancer (PCa) fitness, we performed pooled shRNA screens in vitro and in vivo. Our screens identified heterogeneous nuclear ribonucleoprotein M (HNRNPM) as a regulator of PCa cell growth. RNA- and eCLIP-sequencing identified HNRNPM binding to transcripts of key homeostatic genes. HNRNPM binding to its targets prevents aberrant exon inclusion and backsplicing events. In both linear and circular mis-spliced transcripts, HNRNPM preferentially binds to GU-rich elements in long flanking proximal introns. Mimicry of HNRNPM-dependent linear-splicing events using splice-switching-antisense-oligonucleotides was sufficient to inhibit PCa cell growth. This suggests that PCa dependence on HNRNPM is likely a result of mis-splicing of key homeostatic coding and non-coding genes. Our results have further been confirmed in other solid tumors. Taken together, our data reveal a role for HNRNPM in supporting cancer cell fitness. Inhibition of HNRNPM activity is therefore a potential therapeutic strategy in suppressing growth of PCa and other solid tumors.

Circular (circ)RNAs participate in colorectal cancer (CRC) occurrence and progression. However, the role of hsa_circ_0004662 (circ_0004662) in CRC remains unknown. Reverse transcription-quantitative PCR noted high expression of circ_0004662 in CRC compared with normal colorectal epithelial cells. circ_0004662 knockdown inhibited migration of CRC cells in vitro and in vivo; would healing and Transwell assays showed that circ_0004662 overexpression contributed to CRC migration. Nuclear cytoplasmic analysis and fluorescence in situ hybridization revealed localization of circ_0004662 in the nucleus and cytoplasm. CircRNADB databases predicted that circ_0004662 exhibited translational potential and liquid chromatography-mass spectrometry (LC-MS) of circ_0004662 pull-down products suggested that circ_0004662 bound to multiple ribosomal subunits. However, peptide products of 149aa translated by circ_0004662, with a molecular weight of ~17 kDa were not detected. Nevertheless, LC-MS analysis indicated that circ_0004662 bound multiple proteins. Immunoprecipitation of RNA-binding proteins revealed that circ_0004662 bound to heterogeneous nuclear ribonucleoprotein M (hnRNPM) and that hnRNPM interference decreased circ_0004662 expression, thereby affecting CRC progression. In summary, circ_0004662 was significantly upregulated in CRC. As a non-coding RNA, it may promote CRC progression by binding to hnRNPM, which may serve as a potential target for treating CRC.

In response to oncogenic signals, Alternative Splicing (AS) regulators such as SR and hnRNP proteins show altered expression levels, subnuclear distribution and/or post-translational modification status, but the link between signals and these changes remains unknown. Here, we report that a cytosolic scaffold protein, IQGAP1, performs this task in response to heat-induced signals. We show that in gastric cancer cells, a nuclear pool of IQGAP1 acts as a tethering module for a group of spliceosome components, including hnRNPM, a splicing factor critical for the response of the spliceosome to heat-shock. IQGAP1 controls hnRNPM’s sumoylation, subnuclear localisation and the relevant response of the AS machinery to heat-induced stress. Genome-wide analyses reveal that IQGAP1 and hnRNPM co-regulate the AS of a cell cycle-related RNA regulon in gastric cancer cells, thus favouring the accelerated proliferation phenotype of gastric cancer cells. Overall, we reveal a missing link between stress signals and AS regulation.

Background The identification of cancer driver genes from sequencing data has been crucial in deepening our understanding of tumor biology and expanding targeted therapy options. However, apart from the most commonly altered genes, the mechanisms underlying the contribution of other mutations to cancer acquisition remain understudied. Leveraging on our whole-exome sequencing of the largest Asian lung adenocarcinoma (LUAD) cohort ( n  = 302), we now functionally assess the mechanistic role of a novel driver, PARP4. Methods In vitro and in vivo tumorigenicity assays were used to study the functional effects of PARP4 loss and mutation in multiple lung cancer cell lines. Interactomics analysis by quantitative mass spectrometry was conducted to identify PARP4’s interaction partners. Transcriptomic data from cell lines and patient tumors were used to investigate splicing alterations. Results PARP4 depletion or mutation (I1039T) promotes the tumorigenicity of KRAS- or EGFR-driven lung cancer cells. Disruption of the vault complex, with which PARP4 is commonly associated, did not alter tumorigenicity, indicating that PARP4’s tumor suppressive activity is mediated independently. The splicing regulator hnRNPM is a potentially novel PARP4 interaction partner, the loss of which likewise promotes tumor formation. hnRNPM loss results in splicing perturbations, with a propensity for dysregulated intronic splicing that was similarly observed in PARP4 knockdown cells and in LUAD cohort patients with PARP4 copy number loss. Conclusions PARP4 is a novel modulator of lung adenocarcinoma, where its tumor suppressive activity is mediated not through the vault complex—unlike conventionally thought, but in association with its novel interaction partner hnRNPM, thus suggesting a role for splicing dysregulation in LUAD tumorigenesis.

Aberrant alternative splicing events play a critical role in cancer biology, contributing to tumor invasion, metastasis, epithelial-mesenchymal transition, and drug resistance. Recent studies have shown that alternative splicing is a key feature for transcriptomic variations in colorectal cancer, which ranks third among malignant tumors worldwide in both incidence and mortality. Long non-coding RNAs can modulate this process by acting as trans-regulatory agents, recruiting splicing factors, or driving them to specific targeted genes. LncH19 is a lncRNA dis-regulated in several tumor types and, in colorectal cancer, it plays a critical role in tumor onset, progression, and metastasis. In this paper, we found, that in colorectal cancer cells, the long non-coding RNA H19 can bind immature RNAs and splicing factors as hnRNPM and RBFOX2. Through bioinformatic analysis, we identified 57 transcripts associated with lncH19 and containing binding sites for both splicing factors, hnRNPM, and RBFOX2. Among these transcripts, we identified the mRNA of the GTPase-RAC1, whose alternatively spliced isoform, RAC1B, has been ascribed several roles in the malignant transformation. We confirmed, in vitro, the binding of the splicing factors to both the transcripts RAC1 and lncH19. Loss and gain of expression experiments in two colorectal cancer cell lines (SW620 and HCT116) demonstrated that lncH19 is required for RAC1B expression and, through RAC1B, it induces c-Myc and Cyclin-D increase. In vivo, investigation from biopsies of colorectal cancer patients showed higher levels of all the explored genes (lncH19, RAC1B, c-Myc and Cyclin-D) concerning the healthy counterpart, thus supporting our in vitro model. In addition, we identified a positive correlation between lncH19 and RAC1B in colorectal cancer patients. Finally, we demonstrated that lncH19, as a shuttle, drives the splicing factors RBFOX2 and hnRNPM to RAC1 allowing exon retention and RAC1B expression. The data shown in this paper represent the first evidence of a new mechanism of action by which lncH19 carries out its functions as an oncogene by prompting colorectal cancer through the modulation of alternative splicing.

To evaluate the prognostic effect of the Heterogeneous nuclear ribonucleoprotein type M (HNRPM) and Solute carrier 1A5 (SLC1A5) in FIGO-stages I-II epithelial ovarian cancer. A retrospective cohort study was designed to investigate the prognostic effect of HNRPM and SLC1A5, and the association with clinical-pathologic characteristics in 131 patients with FIGO-stages I-II epithelial ovarian cancer. Tissue microarrays were constructed and protein levels were assessed by immunohistochemistry (IHC). Positive HRNPM status was associated with positive staining for PUMA (P = 0.04), concomitant PUMA and p21 staining (P = 0.005), and VEGF-R2 (P = 0.003). Positive SLC1A5 staining was associated with positive staining of p27 (P = 0.030), PUMA (P = 0.039), concomitant PUMA and p27 staining, and VEGF-R2 (P = 0.039). In non-serous tumors (n = 72), the SLC1A5 positivity was associated with recurrent disease (P = 0.01). In a multivariable logistic regression analysis FIGO-stage (OR = 12.4), tumor grade (OR = 5.1) and SLC1A5 positivity (OR = 0.1) were independent predictive factors for recurrent disease. Disease-free survival (DFS) in women with SLC1A5-positive non-serous tumors was 92% compared with of 66% in patients with SLC1A5-negative non-serous tumors (Log-rank = 15.343; P = 0.008). In Cox analysis with DFS as endpoint, FIGO-stage (HR = 4.5) and SLC1A5 status (HR = 0.3) were prognostic factors. As the proteins HRNPM and SLC1A5 are associated with the cell cycle regulators p21 or p27, the apoptosis regulators PTEN and PUMA, and the VEGF-R2 it is concluded that both proteins have role in the pathogenesis of ovarian cancer. In patients with non-serous ovarian cancer SLC1A5 protects from recurrent disease, presumably by means of biological mechanisms that are unrelated to cytotoxic drug sensitivity.

This article discusses the role of carcinoembryonic antigen (CEA) as a facilitator of the inflammatory response and its effect on colorectal cancer hepatic metastasis. Colorectal cancer accounts for 11% of all cancers in the United States and the majority of deaths are associated with liver metastasis. If left untreated, median survival is only six to 12 months. Resection of liver metastases offers the only chance for cure. Of the small number of patients who have operable cancer most will have further tumor recurrence. The molecular mechanisms associated with colorectal cancer metastasis to the liver are largely unknown. However CEA production has been shown both clinically and experimentally to be a factor in an increased metastatic potential of colorectal cancers to the liver. CEA also has a role in protecting tumor cells from the effects of anoikis and this affords a selective advantage for tumor cell survival in the circulation. CEA acts in the liver through its interaction with its receptor (CEAR), a protein that is related to the hnRNP M family of RNA binding proteins. In the liver CEA binds with hnRNP M on Kupffer cells and causes activation and production of pro- and anti-inflammatory cytokines including IL-1, IL-10, IL-6 and TNF-α. These cytokines affect the up-regulation of adhesion molecules on the hepatic sinusoidal endothelium and protect the tumor cells against cytotoxicity by nitric oxide (NO) and other reactive oxygen radicals. HnRNP M signaling in Kupffer cells appears to be controlled by beta-adrenergic receptor activation. The cells will respond to the β-adrenergic receptor agonist terbutaline resulting in reduced TNF-α and increased IL-10 and IL-6 production following CEA activation. This has implications for the control of tumor cell implantation and survival in the liver.