CFIm25 and alternative polyadenylation: Conflicting roles in cancer

The role of circular RNA targeting IGF2BPs in cancer-a potential target for cancer therapy

Circular RNAs (circRNAs) are an interesting class of conserved single-stranded RNA molecules derived from exon or intron sequences produced by the reverse splicing of precursor mRNA. CircRNAs play important roles as microRNA sponges, gene splicing and transcriptional regulators, RNA-binding protein sponges, and protein/peptide translation factors. Abnormal functions of circRNAs and RBPs in tumor progression have been widely reported. Insulin-like growth factor-2 mRNA-binding proteins (IGF2BPs) are a highly conserved family of RBPs identified in humans that function as post-transcriptional fine-tuners of target transcripts. Emerging evidence suggests that IGF2BPs regulate the processing and metabolism of RNA, including its stability, translation, and localization, and participate in a variety of cellular functions and pathophysiology. In this review, we have summarized the roles and molecular mechanisms of circRNAs and IGF2BPs in cancer development and progression. In addition, we briefly introduce the role of other RNAs and IGF2BPs in cancer, discuss the current clinical applications and challenges faced by circRNAs and IGF2BPs, and propose future directions for this promising research field.

Involvement of oncomiRs miR-23, miR-24, and miR-27 in the regulation of alternative polyadenylation in glioblastoma via CFIm25 cleavage factor

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor with a poor prognosis. The cleavage factor Im 25 (CFIm25), a crucial component of the CFIm complex, plays a key role in regulating the length of the mRNA 3'-UTR and has been implicated in various cancers, including GBM. This study sought to investigate the regulatory influence of specific microRNAs (miRNAs) on CFIm25 expression in GBM, a highly aggressive brain tumor. Bioinformatics analysis identified miRNA candidates targeting CFIm25 mRNA, and gene expression profiles from the NCBI database (GSE90603) were used for further analysis. Expression levels of CFIm25 and selected miRNAs were assessed using qRT-PCR in GBM clinical samples (n = 20) and non-malignant brain tissues (n = 5). Additionally, the MTT assay was performed to examine the effect of miRNA overexpression on U251 cell viability. Lentivectors expressing the identified miRNAs were employed to experimentally validate their regulatory role on CFIm25 in U251 cell lines, and Western blot analysis was conducted to determine CFIm25 protein levels. We observed significantly increased levels of miR-23, miR-24, and miR-27 expression, associated with a marked reduction in CFIm25 expression in GBM samples compared to non-malignant brain tissues. In particular, overexpression of miR-23, miR-24, and miR-27 in U251 cells resulted in CFIm25 downregulation at both the mRNA and protein levels, while their inhibition increased CFIm25 and reduced cell proliferation. These observations strongly implicate miR-23, miR-24, and miR-27 in regulating CFIm25 expression in GBM, emphasizing their potential as promising therapeutic targets for enhancing treatment responses in glioblastoma.

The role of alternative polyadenylation in breast cancer

Breast cancer (BC), as a highly prevalent malignant tumor worldwide, is still unclear in its pathogenesis and has poor therapeutic outcomes. Alternative polyadenylation (APA) is a post-transcriptional regulatory mechanism widely found in eukaryotes. Precursor mRNA (pre-mRNA) undergoes the APA process to generate multiple mRNA isoforms with different coding regions or 3'UTRs, thereby greatly increasing the diversity and complexity of the eukaryotic transcriptome and proteome. Studies have shown that APA is involved in the progression of various diseases, including cancer, and plays a crucial role. Therefore, clarifying the biological mechanisms of APA and its regulators in breast cancer will help to comprehensively understand the pathogenesis of breast cancer and provide new ideas for its prevention and treatment.

RNA m6a Methylation Regulator Expression in Castration-Resistant Prostate Cancer Progression and Its Genetic Associations

N6-methyladenosine (m6A) methylation, a prevalent epitranscriptomic modification, plays a crucial role in regulating mRNA expression, stability, and translation in mammals. M6A regulators have gained attention for their potential implications in tumorigenesis and clinical applications, such as cancer diagnosis and therapeutics. The existing literature predominantly addresses m6A regulators in the context of primary prostate cancer (PCa). However, a notable gap in the knowledge emerges regarding the dynamic expression patterns of these regulators as PCa progresses towards the castration-resistant stage (CRPC). Employing sequential window acquisition of all theoretical mass spectra (SWATH-MS) and RNAseq analysis, we comprehensively profiled the expression of 27 m6A regulators in hormone/androgen-dependent and -independent PCa cell lines, revealing distinct clustering between tumor and adjacent normal prostate tissues. High-grade PCa tumors demonstrated the upregulation of METTL3, RBM15B, and HNRNAPA2B1 and the downregulation of ZC3H13, NUDT21, and FTO. Notably, we identified six m6A regulators associated with PCa survival. Additionally, association analysis of the PCa-associated risk loci in the cancer genome atlas program (TCGA) data unveiled genetic variations near the WTAP, HNRNPA2B1, and FTO genes as significant expression quantitative trait loci. In summary, our study unraveled abnormalities in m6A regulator expression in PCa progression, elucidating their association with PCa risk loci. Considering the heterogeneity within the PCa phenotypes and treatment responses, our findings suggest that prognostic stratification based on m6A regulator expression could enhance PCa diagnosis and prognosis.

Nudt21-mediated alternative polyadenylation of MZT1 3'UTR contributes to pancreatic cancer progression

Alternative polyadenylation (APA) is an important post-transcriptional regulatory mechanism and is involved in many diseases, but its function and mechanism in regulating pancreatic cancer (PC) pathogenesis remain unclear. In this study, we found that the 3' UTR shortening of MZT1 was the most prominent APA event in PC liver metastases. The short-3'UTR isoform exerted a stronger effect in promoting cell proliferation and migration both in vitro and in vivo. NUDT21, a core cleavage factor involved in APA, promoted the usage of proximal polyadenylation sites (PASs) on MZT1 mRNA by binding to the UGUA element located upstream of the proximal PAS. High percentage of distal polyA site usage index of MZT1 was significantly associated with a better prognosis. These findings demonstrate a crucial mechanism that NUDT21-mediated APA of MZT1 could promote the progression of PC. Our findings provided a better understanding of the connection between PC progression and APA machinery.

NUDT21 interacts with NDUFS2 to activate the PI3K/AKT pathway and promotes pancreatic cancer pathogenesis

BACKGROUND

NUDT21 (Nudix Hydrolase 21) has been shown to play an essential role in multiple biological processes. Pancreatic adenocarcinoma (PAAD) is one of the most fatal cancers in the world. However, the biological function of NUDT21 in PAAD remains rarely understood. The aim of this research was to identify the prediction value of NUDT21 in diagnosis, prognosis, immune infiltration, and signal pathway in PAAD.

METHODS

Combined with the data in online databases, we analyzed the expression, immune infiltration, function enrichment, signal pathway, diagnosis, and prognosis of NUDT21 in PAAD. Then, the biological function of NUDT21 and its interacted protein in PAAD was identified through plasmid transduction system and protein mass spectrometry. Expression of NUDT21 was further verified in clinical specimens by immunofluorescence.

RESULTS

We found that NUDT21 was upregulated in PAAD tissues and was significantly associated with the diagnosis and prognosis of pancreatic cancer through bioinformatic data analysis. We also found that overexpression of NUDT21 enhanced PAAD cells proliferation and migration, whereas knockdown NUDT21 restored the effects through in vitro experiment. Moreover, NDUFS2 was recognized as a potential target of NUDT21.We further verified that the expression of NDUFS2 was positively correlated with NUDT21 in PAAD clinical specimens. Mechanically, we found that NUDT21 stabilizes NDUFS2 and activates the PI3K-AKT signaling pathway.

CONCLUSION

Our investigation reveals that NUDT21 is a previously unrecognized oncogenic factor in the diagnosis, prognosis, and treatment target of PAAD, and we suggest that NUDT21 might be a novel therapeutic target in PAAD.

Lengthening of 3' Untranslated Regions of mRNAs by Alternative Polyadenylation Is Associated With Tumor Progression and Poor Prognosis of Clear Cell Renal Cell Carcinoma

Alternative polyadenylation (APA) is emerging as a major posttranscriptional mechanism for gene regulation in cancer. A prevailing hypothesis is that shortening of the 3' untranslated region (3'UTR) increases oncoprotein expression because of the loss of miRNA-binding sites (MBSs). We showed that the longer 3'UTR is associated with a more advanced tumor stage in patients with clear cell renal cell carcinoma (ccRCC). More surprisingly, 3'UTR shortening is correlated with better overall survival in patients with ccRCC. Furthermore, we identified a mechanism by which longer transcripts lead to increased oncogenic protein and decreased tumor-suppressive protein expression compared to the shorter transcripts. In our model, shortening of 3'UTRs by APA may increase the mRNA stability of the majority of the potential tumor-suppressor genes due to the loss of MBSs and AU-rich elements (AREs). Unlike potential tumor-suppressor genes, the potential oncogenes display much lower MBS and ARE density and globally much higher m6A density in distal 3'UTRs. As a result, 3'UTRs shortening decreases the mRNA stability of potential oncogenes and enhances the mRNA stability of potential tumor-suppressor genes. Our findings highlight the cancer-specific pattern of APA regulation and extend our understanding of the mechanism of APA-mediated 3'UTR length changes in cancer biology.

Iron restriction increases the expression of a cytotoxic cysteine proteinase TvCP2 by a novel mechanism of tvcp2 mRNA alternative polyadenylation in Trichomonas vaginalis

Trichomonas vaginalis TvCP2 (TVAG_057000) is a cytotoxic cysteine proteinase (CP) expressed under iron-limited conditions. This work aimed to identify one of the mechanisms of tvcp2 gene expression regulation by iron at the posttranscriptional level. We checked tvcp2 mRNA stability under both iron-restricted (IR) and high iron (HI) conditions in the presence of actinomycin D. Greater stability of the tvcp2 mRNA under the IR than in HI conditions was observed, as expected. In silico analysis of the 3' regulatory region showed the presence of two putative polyadenylation signals in the tvcp2 transcript. By 3'-RACE assays, we demonstrated the existence of two isoforms of the tvcp2 mRNA with different 3'-UTR that resulted in more TvCP2 protein under IR than in HI conditions detected by WB assays. Additionally, we searched for homologs of the trichomonad polyadenylation machinery by an in silico analysis in the genome database, TrichDB. 16 genes that encode proteins that could be part of the trichomonad polyadenylation machinery were found. qRT-PCR assays showed that most of these genes were positively regulated by iron. Thus, our results show the presence of alternative polyadenylation as a novel iron posttranscriptional regulatory mechanism in T. vaginalis for the tvcp2 gene expression.

Relationship between NUDT21 mediated alternative polyadenylation process and tumor

Alternative polyadenylation (APA) is a molecular process that generates diversity at the 3' end of RNA polymerase II transcripts from over 60% of human genes. APA and microRNA regulation are both mechanisms of post-transcriptional regulation of gene expression. As a key molecular mechanism, Alternative polyadenylation often results in mRNA isoforms with the same coding sequence but different lengths of 3' UTRs, while microRNAs regulate gene expression by binding to specific mRNA 3' UTRs. Nudix Hydrolase 21 (NUDT21) is a crucial mediator involved in alternative polyadenylation (APA). Different studies have reported a dual role of NUDT21 in cancer (both oncogenic and tumor suppressor). The present review focuses on the functions of APA, miRNA and their interaction and roles in development of different types of tumors.NUDT21 mediated 3' UTR-APA changes can be used to generate specific signatures that can be used as potential biomarkers in development and disease. Due to the emerging role of NUDT21 as a regulator of the aforementioned RNA processing events, modulation of NUDT21 levels may be a novel viable therapeutic approach.

Targeting the PI3K/AKT/mTOR and RAF/MEK/ERK pathways for cancer therapy

The PI3K/AKT/mTOR and RAF/MEK/ERK pathways are commonly activated by mutations and chromosomal translocation in vital targets. The PI3K/AKT/mTOR signaling pathway is dysregulated in nearly all kinds of neoplasms, with the component in this pathway alternations. RAF/MEK/ERK signaling cascades are used to conduct signaling from the cell surface to the nucleus to mediate gene expression, cell cycle processes and apoptosis. RAS, B-Raf, PI3K, and PTEN are frequent upstream alternative sites. These mutations resulted in activated cell growth and downregulated cell apoptosis. The two pathways interact with each other to participate in tumorigenesis. PTEN alterations suppress RAF/MEK/ERK pathway activity via AKT phosphorylation and RAS inhibition. Several inhibitors targeting major components of these two pathways have been supported by the FDA. Dozens of agents in these two pathways have attracted great attention and have been assessed in clinical trials. The combination of small molecular inhibitors with traditional regimens has also been explored. Furthermore, dual inhibitors provide new insight into antitumor activity. This review will further comprehensively describe the genetic alterations in normal patients and tumor patients and discuss the role of targeted inhibitors in malignant neoplasm therapy. We hope this review will promote a comprehensive understanding of the role of the PI3K/AKT/mTOR and RAF/MEK/ERK signaling pathways in facilitating tumors and will help direct drug selection for tumor therapy.

Hsa_circ_0040809 and hsa_circ_0000467 promote colorectal cancer cells progression and construction of a circRNA-miRNA-mRNA network

Objective: Circular RNAs (circRNAs) have been demonstrated to be closely involved in colorectal cancer (CRC) pathogenesis and metastasis. More potential biomarkers are needed to be searched for colorectal cancer (CRC) diagnosis and treatment. The objective of this study is to seek differentially expressed circRNAs (DEcircRNAs), test their roles in CRC and construct a potential competing endogenous RNA (ceRNA) network.

Methods: CircRNA microarrays were obtained from Gene Expression Omnibus, and differential expression was analyzed by R software. The relative expressions of DEcircRNAs were confirmed in CRC tissues and cell lines by qRT-PCR. MTs and Transwell experiments were performed for detecting the roles of circRNAs on CRC cell proliferation and migration, respectively. Targeted miRNAs of circRNAs and targeted mRNAs of miRNAs were predicted and screened by bioinformatics methods. A ceRNA network of DEcircRNAs was constructed by Cytoscape. To further verify the potential ceRNA network, the expressions of miRNAs and mRNAs in knockdown of DEcircRNAs CRC cells were detected by qRT-PCR.

Results: Two DEcircRNAs (hsa_circ_0040809 and hsa_circ_0000467) were identified and validated in CRC tissues and cell lines. The results of MTs and Transwell experiments showed that hsa_circ_0040809 and hsa_circ_0000467 promoted CRC proliferation and migration. Bioinformatics analysis screened 3 miRNAs (miR-326, miR-330-5p, and miR-330-3p) and 2 mRNAs (FADS1 and RUNX1), and a ceRNA network was constructed. In knockdown of hsa_circ_0040809 HCT-116 cells, the expression of miR-330-3p was significantly upregulated, while RUNX1 was significantly downregulated. In knockdown of hsa_circ_0000467 HCT-116 cells, the expressions of miR-326 and miR-330-3p were upregulated, while FADS1was downregulated.

Conclusion: We found that hsa_circ_0040809 and hsa_circ_0000467 were upregulated in CRC tissues and cell lines, and promoted CRC cell progression. A circRNA-miRNA-mRNA network based on hsa_circ_0040809 and hsa_circ_0000467 was constructed.

Targeting the mRNA endonuclease CPSF73 inhibits breast cancer cell migration, invasion, and self-renewal

Cleavage by the endonuclease CPSF73 and polyadenylation of nascent RNA is an essential step in co-transcriptional mRNA maturation. Recent work has surprisingly identified CPSF73 as a promising drug target for inhibiting the growth of specific cancers, triggering further studies on understanding CPSF73 regulation and functions in cells. Here, we report that a HECT-like E3 ligase, UBE3D, participates in stabilizing CPFS73 protein by preventing its ubiquitin-mediated degradation by the proteasome. Depletion of UBE3D leads to CPSF73 downregulation, a pre-mRNA cleavage defect, and dysregulated gene expression in cells. UBE3D dysfunction or chemical inactivation of CPSF73 inhibited migration and invasion as well as stem cell renewal phenotypes in vitro in triple-negative breast cancer cells. In addition, genetic overexpression of CPSF73 promoted breast cancer stemness and knocking down CPSF73 inhibited stem cell renewal properties. Together, our findings indicate that targeting the pre-mRNA processing nuclease CPSF73 has potential for breast cancer therapy.

CFIm25 regulates human stem cell function independently of its role in mRNA alternative polyadenylation

It has recently been shown that CFIm25, a canonical mRNA 3’ processing factor, could play a variety of physiological roles through its molecular function in the regulation of mRNA alternative polyadenylation (APA). Here, we used CRISPR/Cas9-mediated gene editing approach in human embryonic stem cells (hESCs) for CFIm25, and obtained three gene knockdown/mutant cell lines. CFIm25 gene editing resulted in higher proliferation rate and impaired differentiation potential for hESCs, with these effects likely to be directly regulated by the target genes, including the pluripotency factor rex1. Mechanistically, we unexpected found that perturbation in CFIm25 gene expression did not significantly affect cellular mRNA 3’ processing efficiency and APA profile. Rather, we provided evidences that CFIm25 may impact RNA polymerase II (RNAPII) occupancy at the body of transcribed genes, and promote the expression level of a group of transcripts associated with cellular proliferation and/or differentiation. Taken together, these results reveal novel mechanisms underlying CFIm25ʹs modulation in determination of cell fate, and provide evidence that the process of mammalian gene transcription may be regulated by an mRNA 3’ processing factor.

CFIm-mediated alternative polyadenylation remodels cellular signaling and miRNA biogenesis

The mammalian cleavage factor I (CFIm) has been implicated in alternative polyadenylation (APA) in a broad range of contexts, from cancers to learning deficits and parasite infections. To determine how the CFIm expression levels are translated into these diverse phenotypes, we carried out a multi-omics analysis of cell lines in which the CFIm25 (NUDT21) or CFIm68 (CPSF6) subunits were either repressed by siRNA-mediated knockdown or over-expressed from stably integrated constructs. We established that >800 genes undergo coherent APA in response to changes in CFIm levels, and they cluster in distinct functional classes related to protein metabolism. The activity of the ERK pathway traces the CFIm concentration, and explains some of the fluctuations in cell growth and metabolism that are observed upon CFIm perturbations. Furthermore, multiple transcripts encoding proteins from the miRNA pathway are targets of CFIm-dependent APA. This leads to an increased biogenesis and repressive activity of miRNAs at the same time as some 3′ UTRs become shorter and presumably less sensitive to miRNA-mediated repression. Our study provides a first systematic assessment of a core set of APA targets that respond coherently to changes in CFIm protein subunit levels (CFIm25/CFIm68). We describe the elicited signaling pathways downstream of CFIm, which improve our understanding of the key role of CFIm in integrating RNA processing with other cellular activities.

Cleavage factor Im 25 as a potential biomarker for prognosis of colorectal cancer

Background

Cleavage factor Im 25 (CFIm25) affects the prognosis and progression of cancer by regulating alternative polyadenylation; however, its role in colorectal cancer remains unclear.

Methods

A standard EnVision tissue microarray was used to evaluate the expression of CFIm25 by immunohistochemistry in 363 patients with colorectal cancer. The correlation between CFIm25 expression and clinicopathological characteristics was analyzed using the χ² test. Univariate analysis was used to study the relationship between clinicopathological characteristics and patient prognosis. Multivariate analysis was performed using the Cox regression model to identify independent prognostic factors for patients with colorectal cancer.

Results

Statistical analysis revealed that CFIm25 expression was significantly associated with vascular invasion (P=0.000), serous invasion (P=0.007), pT stage (P=0.016), and clinical stage (P=0.007). Age, vascular invasion, nerve invasion, serosal invasion, differentiation, clinical stage, recurrence, and CFIm25 expression were significantly correlated with the survival time of colorectal cancer patients (P<0.05). The mean overall survival rate in colorectal cancer patients with decreased CFIm25 expression was only 88.53 months, compared with 110.69 months in the high expression group (P=0.000). Decreased CFIm25 expression indicated a worse prognosis in patients with colorectal cancer. Further analysis by the Cox multivariate model showed that CFIm25 (HR, 0.543; 95% CI: 0.372–0.792; P=0.002) and serosa invasion (HR, 1.470; 95% CI: 1.032–2.094; P=0.033) are independent prognostic factors for colorectal cancer.

Conclusions

Decreased CFIm25 expression indicates a worse prognosis of colorectal cancer patients and could be a novel target for the treatment of colorectal cancer in the future.

Keywords

Polyadenylation; survival analysis; colorectal cancer (CRC); CFIm25

Alternative polyadenylation: An untapped source for prostate cancer biomarkers and therapeutic targets?

Objective

To review alternative polyadenylation (APA) as a mechanism of gene regulation and consider potential roles for APA in prostate cancer (PCa) biology and treatment.

Methods

An extensive review of mRNA polyadenylation, APA, and PCa literature was performed. This review article introduces APA and its association with human disease, outlines the mechanisms and components of APA, reviews APA in cancer biology, and considers whether APA may contribute to PCa progression and/or produce novel biomarkers and therapeutic targets for PCa.

Results

Eukaryotic mRNA 3′-end cleavage and polyadenylation play a critical role in gene expression. Most human genes encode more than one polyadenylation signal, and produce more than one transcript isoform, through APA. Polyadenylation can occur throughout the gene body to generate transcripts with differing 3′-termini and coding sequence. Differences in 3′-untranslated regions length can modify post-transcriptional gene regulation by microRNAs and RNA binding proteins, and alter mRNA stability, translation efficiency, and subcellular localization. Distinctive APA patterns are associated with human diseases, tissue origins, and changes in cellular proliferation rate and differentiation state. APA events may therefore generate unique mRNA biomarkers or therapeutic targets in certain cancer types or phenotypic states.

Conclusions

The full extent of cancer-associated and tissue-specific APA events have yet to be defined, and the mechanisms and functional consequences of APA in cancer remain incompletely understood. There is evidence that APA is active in PCa, and that it may be an untapped resource for PCa biomarkers or therapeutic targets.

NUDT21 Promotes Tumor Growth and Metastasis Through Modulating SGPP2 in Human Gastric Cancer

Gastric cancer is one of the major malignancies with poor survival outcome. In this study, we reported that NUDT21 promoted cell proliferation, colony formation, cell migration and invasion in gastric cancer cells. The expression levels of NUDT21 were found to be much higher in human gastric cancer tissues compared with normal gastric tissues. NUDT21 expression was positively correlated with tumor size, lymph node metastasis and clinical stage in gastric cancer patients. High level of NUDT21 was associated with poor overall survival (OS) rates in gastric cancer patients. The expression levels of NUDT21 were also much higher in gastric cancer tissues from patients with tumor metastasis compared with those of patients without tumor metastasis. Moreover, forced expression of NUDT21 in gastric cancer cells promoted tumor growth and cell proliferation in xenograft nude mice, and depletion of NUDT21 in gastric cancer cells restrained lung metastasis in vivo. Through high throughput RNA-sequencing, SGPP2 was identified to be positively regulated by NUDT21 and mediated the tumor promoting role of NUDT21 in gastric cancer cells. Therefore, NUDT21 played an oncogenic role in human gastric cancer cells. NUDT21 could be considered as a novel potential target for gastric cancer therapy.

SAM homeostasis is regulated by CFIm-mediated splicing of MAT2A

S-adenosylmethionine (SAM) is the methyl donor for nearly all cellular methylation events. Cells regulate intracellular SAM levels through intron detention of MAT2A, the only SAM synthetase expressed in most cells. The N6-adenosine methyltransferase METTL16 promotes splicing of the MAT2A detained intron by an unknown mechanism. Using an unbiased CRISPR knock-out screen, we identified CFIm25 (NUDT21) as a regulator of MAT2A intron detention and intracellular SAM levels. CFIm25 is a component of the cleavage factor Im (CFIm) complex that regulates poly(A) site selection, but we show it promotes MAT2A splicing independent of poly(A) site selection. CFIm25-mediated MAT2A splicing induction requires the RS domains of its binding partners, CFIm68 and CFIm59 as well as binding sites in the detained intron and 3´ UTR. These studies uncover mechanisms that regulate MAT2A intron detention and reveal a previously undescribed role for CFIm in splicing and SAM metabolism.

Cervical Cancer Diagnosis: Insights into Biochemical Biomarkers and Imaging Techniques

Cervical malignancy is known as one of the important cancers which is originated from cervix. This malignancy has been observed in women infected with papillomavirus who had regular oral contraceptives, multiple pregnancies, and sexual relations. Early and fast cervical cancer diagnosis is known as two important aspects of cervical cancer therapy. Several investigations indicated that early and fast detection of cervical cancer could be associated with better treatment process and increasing survival rate of patients with this malignancy. Imaging techniques are very important diagnosis tools that could be employed for diagnosis and following responses to therapy in various cervical cancer stages. Multiple lines of evidence indicated that utilization of imaging techniques is related to some limitations (i.e. high cost, and invasive effects). Hence, it seems that along with using imaging techniques, finding and developing new biomarkers could be useful in the diagnosis and treatment of subjects with cervical cancer. Taken together, many studies showed that a variety of biomarkers including, several proteins, mRNAs, microRNAs, exosomes and polymorphisms might be introduced as prognostic, diagnostic and therapeutic biomarkers in cervical cancer therapy. In this review article, we highlighted imaging techniques as well as novel biomarkers for the diagnosis of cervical cancer.

Downregulation of NUDT21 contributes to cervical cancer progression through alternative polyadenylation

Nudix Hydrolase 21 (NUDT21), an alternative polyadenylation (APA)-regulatory protein, exhibits tumor-suppressive effects. However, its role in cervical cancer (CxCa) remains unknown. In the present study, we found that NUDT21 expression was reduced in CxCa tissues and cells, and NUDT21 levels were highly associated with the clinical prognosis of patients with CxCa. Knockdown of NUDT21 promoted CxCa cell proliferation, migration, and invasion in vitro, as well as tumorigenesis and lung metastasis in vivo. Overexpression of NUDT21 produces the opposite effects. Moreover, we performed polyadenylation site sequencing (PAS-Seq) and identified 457 transcripts with lengthened 3' untranslated regions (3' UTRs) upon NUDT21 overexpression. In particular, NUDT21 modulated the expression of several genes involved in fatty acid metabolism and the Wnt and NF-κB signaling pathways in CxCa development. Taken together, our study demonstrated that the APA regulatory effect of NUDT21 is an important mechanism for CxCa suppression.

Review on circular RNAs and new insights into their roles in cancer

Circular RNAs (circRNAs) are a very interesting class of conserved single-stranded RNA molecules derived from exonic or intronic sequences by precursor mRNA back-splicing. Unlike canonical linear RNAs, circRNAs form covalently closed, continuous stable loops without a 5'end cap and 3'end poly(A) tail, and therefore are resistant to exonuclease digestion. The majority of circRNAs are highly abundant, and conserved across different species with a tissue or developmental-stage-specific expression. circRNAs have been shown to play important roles as microRNA sponges, regulators of gene splicing and transcription, RNA-binding protein sponges and protein/peptide translators. Emerging evidence reveals that circRNAs function in various human diseases, particularly cancers, and may function as better predictive biomarkers and therapeutic targets for cancer treatment. In consideration of their potential clinical relevance, circRNAs have become a new research hotspot in the field of tumor pathology. In the present study, the current understanding of the biogenesis, characteristics, databases, research methods, biological functions subcellular distribution, epigenetic regulation, extracellular transport and degradation of circRNAs was discussed. In particular, the multiple databases and methods involved in circRNA research were first summarized, and the recent advances in determining the potential roles of circRNAs in tumor growth, migration and invasion, which render circRNAs better predictive biomarkers, were described. Furthermore, future perspectives for the clinical application of circRNAs in the management of patients with cancer were proposed, which could provide new insights into circRNAs in the future.

Alternative Polyadenylation: a new frontier in post transcriptional regulation

Polyadenylation of pre-messenger RNA (pre-mRNA) specific sites and termination of their downstream transcriptions are signaled by unique sequence motif structures such as AAUAAA and its auxiliary elements. Alternative polyadenylation (APA) is an important post-transcriptional regulatory mechanism that processes RNA products depending on its 3'-untranslated region (3'-UTR) specific sequence signal. APA processing can generate several mRNA isoforms from a single gene, which may have different biological functions on their target gene. As a result, cellular genomic stability, proliferation capability, and transformation feasibility could all be affected. Furthermore, APA modulation regulates disease initiation and progression. APA status could potentially act as a biomarker for disease diagnosis, severity stratification, and prognosis forecast. While the advance of modern throughout technologies, such as next generation-sequencing (NGS) and single-cell sequencing techniques, have enriched our knowledge about APA, much of APA biological process is unknown and pending for further investigation. Herein, we review the current knowledge on APA and how its regulatory complex factors (CFI/IIm, CPSF, CSTF, and RBPs) work together to determine RNA splicing location, cell cycle velocity, microRNA processing, and oncogenesis regulation. We also discuss various APA experiment strategies and the future direction of APA research.

Involved microRNAs in alternative polyadenylation intervene in breast cancer via regulation of cleavage factor "CFIm25"

Cleavage factor “CFIm25”, as a key repressor at proximal poly (A) site, negatively correlates to cell proliferation and tumorigenicity in various cancers. Hence, understanding CFIm25 mechanism of action in breast cancer would be a great benefit. To this aim four steps were designed. First, potential miRNAs that target 3′-UTR of CFIm25 mRNA, retrieved from Targetscan web server. Second, screened miRNAs were profiled in 100 breast cancer and 100 normal adjacent samples. Third, miRNAs that their expression was inversely correlated to the CFIm25, overexpressed in MDA-MB-231 cell line, and their effect on proliferation and migration monitored via MTT and wound healing assays, respectively. Fourth, interaction of miRNAs of interest with 3′-UTR of CFIm25 confirmed via luciferase assay and western blot. Our results indicate that CFIm25 considerably down-regulates in human breast cancer tissue. qRT-PCR assay, luciferase test, and western blotting confirm that CFIm25 itself could be directly regulated by oncomiRs such as miR-23, -24, -27, -135, -182 and -374. Besides, according to MTT and wound healing assays of cell lines, CFIm25 knockdown intensifies cell growth, proliferation and migration. Our results also confirm indirect impact of CFIm25 on regulation of mRNA’s 3′–UTR length, which then control corresponding miRNAs’ action. miRNAs directly control CFIm25 expression level, which then tunes expression of the oncogenes and tumor proliferation. Therefore, regulation of CFIm25 expression level via miRNAs is expected to improve treatment responses in breast cancer.

CFIm25 in Solid Tumors: Current Research Progress

Cleavage factor I m25 is a newly discovered solid tumor-related gene, however, its precise role in cancer pathogenesis has not yet been characterized. Alternative polyadenylation is an RNA-processing mechanism that generates distinct 3′-termini on messenger RNAs, producing messenger RNA isoforms. Different factors influence the initiation and development of this process. As a key factor in alternative polyadenylation, cleavage factor I m25 plays an important role in messenger RNA maturation and cell signal transduction. Moreover, by regulating the process of alternative polyadenylation, it can inhibit the proliferation, invasion, and metastasis of a variety of tumors. Cleavage factor I m25 also acts as an oncogene in select tumors. The present review focuses on the role of cleavage factor I m25 in solid tumors and treatment. Due to the lack of current knowledge regarding the mechanisms of action and regulation of cleavage factor I m25 and alternative polyadenylation, it is necessary to further examine their role in cancer as well as in other diseases.

Cancer stem cells as therapeutic targets of pancreatic cancer

The discovery of stem cells and their potential abilities in self-renewal and differentiation has opened a new horizon in medicine. Scientists have found a small population of stem cells in some types of cancers with the same functions as normal stem cells. There are two models for tumor progression: clonal (stochastic) and cancer stem cell (CSCs) models. According to the first model, all transformed cells in the tumor have carcinogenic potential and are able to proliferate and produce the same cells. The latter model, which has received more attention recently, considers the role of CSCs in drug resistance and tumor metastasis. Following the model, researchers have found that targeting CSCs may be a promising way in cancer therapy. This review describes CSC characteristics in general, while also focusing on CSC properties in the context of pancreatic cancer.