MEX3A promotes colorectal cancer migration, invasion and EMT via regulating the Wnt/ß-catenin signaling pathway.

BACKGROUND: Mex-3 RNA binding family members are well-established to be important in cancer development and progression. However, the functions of Mex-3 RNA binding family member A (MEX3A) in colorectal cancer (CRC) metastasis remain poorly understood. In this study, we aim to reveal the function and the mechanism of MEX3A in promoting CRC metastasis. METHODS: We used multiple databases including TCGA database, UALCAN, LinkedOmics, CancerSEA, GeneMANIA and STRING database to investigate the expression, the functions and underlying molecular mechanism of MEX3A in CRC. Multiple experimental methods were adapted to determine the study, including real-time PCR (qPCR), immunohistochemistry (IHC), western blot (WB), transfection, transwell migration and invasion assays, immunofluorescence (IF). RESULTS: We found that MEX3A was significantly upregulated and correlated to tumor stage and lymph nodal metastasis in CRC through bioinformatics analysis and tissue immunohistochemistry (IHC). The higher expression of MEX3A in CRC correlated with poor recurrence-free survival (RFS) and overall survival (OS). In vitro studies showed that knockdown of MEX3A suppressed EMT transition, invasion and metastasis of CRC cells. Mechanistically, we revealed that MEX3A promotes epithelial-mesenchymal transition (EMT), invasion and metastasis of CRC cells by upregulating the Wnt/ß-catenin signaling pathway. CONCLUSION: In conclusion, our study reveals that MEX3A promotes CRC migration, invasion and EMT via regulating the Wnt/ß-catenin signaling pathway and could be a novel therapeutic target for this patient population.

Construction of a TP53 mutation-associated ceRNA network as prognostic biomarkers in hepatocellular carcinoma.

Background: Hepatocellular carcinoma (HCC) continues to endanger human health worldwide. Regulatory networks of competing endogenous RNAs (ceRNAs) play important roles in HCC. TP53 is the second most often altered gene in HCC and has a significant role in regulating target genes such as miRNAs and lncRNAs. Methods: Data from patients with TP53 mutation were collected through the cBioPortal database and differential analysis was performed to screen RNAs related to TP53 mutation. The lncRNA-miRNA-mRNA relationship was predicted by the miRcode, miRDB, and TargetScan databases. The ceRNA networks were screened and visualized by Cytoscape. Core ceRNA networks were generated by differential analysis, coexpression analysis, prognostic analysis and subcellular localization. Finally, methylation, mutation, PPI, GSEA, immunity and drug sensitivity analyses of MEX3A were performed to determine the role of MEX3A in HCC. Results: We identified 1508 DEmRNAs, 85 DEmiRNAs and 931 DElncRNAs and obtained a ceRNA network including 28 lncRNAs, 4 miRNAs and 31 mRNAs. Twenty hub DERNAs in the TP53-altered-related ceRNA network were screened out by Cytoscape and the core ceRNA network (LINC00491/TCL6-hsa-miR-139-5p-MEX3A) was obtained by multiple analyses. In addition, we discovered that the methylation level of MEX3A was decreased and the mutation frequency was raised in HCC. Furthermore, elevated MEX3A expression was associated with alterations in the HCC immunological microenvironment. Conclusion: We successfully constructed a reciprocal ceRNA network, which could provide new ideas for exploring HCC mechanisms and therapeutic approaches.

Hsa_circ_0008133 contributes to lung cancer progression by promoting glycolysis metabolism through the miR-760/MEX3A axis.

BACKGROUND: Lung cancer is a very common cancer with poor prognosis and high mortality. Circular RNAs (circRNAs) have been confirmed to be related to the occurrence of lung cancer, and circ_0008133 has been found to be possibly related to lung cancer. METHODS: Expression of circ_0008133, miR-760, and mex-3 RNA binding family member A (MEX3A) messenger RNA (mRNA) was detected using quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability, colony number, migration, and invasion were assessed using cell counting kit-8 (CCK8), colony formation, wound healing, and transwell assays. Glucose consumption and lactate production were detected using commercial kits. Protein expression was measured using western blot. Dual-luciferase reporter assay and RNA pull-down assay were used to analyze the relationships between miR-760 and circ_0008133 or MEX3A. The effects of circ_0008133 knockdown on tumor growth in vivo were examined by the nude mice expriment. Immunohistochemistry (IHC) assay analyzed Ki-67 expression. RESULTS: Circ_0008133 and MEX3A were markedly boosted in lung cancer tissues and cells. Circ_0008133 knockdown decreased lung cancer cell viability, glucose consumption, lactate production, colony formation, migration, and invasion. In mechanism, circ_0008133 might positively regulate MEX3A expression by sponging miR-760. Additionally, knockdown of circ_0008133 inhibited tumor growth in vivo. CONCLUSION: Circ_0008133 accelerated the progression of lung cancer by promoting glycolysis metabolism through the miR-760/MEX3A axis.

Application value of MEX3A,CDX2,MUC2 and MUC5AC in judging cancerous gastric mucosal intestinal metaplasia / 中国现代医生

@#Objective To investigate the correlation between MEX3A and differentiation characteristics of gastric cancer and intestinal metaplasia,and its combination with caudal-related homeobox transcription factor 2(CDX2)and mucin 2(MUC2)and mucin 5AC(MUC5AC)to determine the role of carcinogenic intestinal metaplasia.Methods From January 2010 to December 2014,a total of 410 cases of gastric cancer and paracarcinoma paraffin-embedded tissue samples were selected from the Central Hospital Affiliated to Shenyang Medical College and the Second Hospital Affiliated to Shenyang Medical College.According to pathological diagnosis,they were divided into control group(mild superficial gastritis,79 cases),intestinal metaplasia group(149 cases)and gastric cancer group(182 cases).The expressions of MEX3A,CDX2,MUC2 and MUC5AC were detected by immunohistochemistry.Results MEX3A was highly expressed in gastric cancer group and intestinal metaplasia group,especially diffuse gastric cancer,poorly differentiated gastric cancer and type Ⅲ intestinal metaplasia(P<0.05).CDX2 and MUC2 were highly expressed in gastric cancer group and intestinal metaplasia group,especially intestinal type gastric cancer,highly and moderately differentiated gastric cancer,type Ⅰ and type Ⅱ intestinal metaplasia(P<0.05).The expression of MUC5AC was high in control group and low in gastric cancer group and intestinal metaplasia group,especially in intestinal type gastric cancer,type Ⅰ and type Ⅲ intestinal metaplasia(P<0.05).Gastric cancer and intestinal metaplasia differentiation were negatively correlated with MEX3A and MUC5AC expression,but positively correlated with CDX2 and MUC2 expression(P<0.05).MEX3A was negatively correlated with the expression of CDX2 and MUC2,and positively correlated with the expression of MUC5AC in gastric cancer(P<0.05).MEX3A was negatively correlated with the expression of CDX2 and MUC2 in intestinal metaplasia(P<0.05),while CDX2 was positively correlated with the expression of MUC2(P<0.05).Conclusion MEX3A is negatively correlated with gastric cancer and intestinal metaplasia differentiation.Gastric cancer is characterized by high MEX3A expression and low CDX2 and MUC2 expression.

MEX3A induces the development of thyroid cancer via targeting CREB1.

Thyroid cancer is a prevalent form of endocrine cancer, and its global incidence has been steadily increasing. MEX3A is a protein that is known to be highly expressed in various human malignant tumors, including thyroid cancer, and it has been linked to patient prognosis. However, the molecular mechanisms underlying MEX3A's tumorigenic capabilities in thyroid cancer are not fully understood. In this study, we aimed to investigate the role of MEX3A in thyroid cancer. We confirmed that MEX3A was overexpressed in both thyroid cancer tissues and cell lines. Additionally, we found a positive correlation between high levels of MEX3A and the AJCC stage. To further understand the functional significance of MEX3A in thyroid cancer, we depleted MEX3A expression in B-CPAP and TPC-1 cells. Interestingly, we observed a significant reduction in thyroid cancer cell proliferation and migration, as well as ameliorated cell apoptosis and arrested tumor growth upon MEX3A depletion. These findings strongly suggested that MEX3A played a critical role in the development of thyroid cancer. Furthermore, our study uncovered an important interaction between MEX3A and CREB1 (cAMP response element-binding protein 1). The interaction between MEX3A and CREB1 appeared to contribute to the tumor-promoting effects of MEX3A in thyroid cancer by directly targeting CREB1. Silencing CREB1 was observed to alleviate the malignant phenotypes promoted by MEX3A in thyroid cancer cells. Together, this study highlighted the importance of the MEX3A-CREB1 interaction in thyroid cancer development and suggested the therapeutic potential of targeting MEX3A for the treatment of this disease.

MEX3A determines in vivo hepatocellular carcinoma progression and induces resistance to sorafenib in a Hippo-dependent way.

BACKGROUND: Hepatocellular carcinoma (HCC) is most common malignant tumor worldwide, and one of the most lethal malignancies. MEX3A, RNA-binding protein, is profoundly implicated in tumor initiation and progression. But its role and potential mechanism in HCC remains fully unclear. METHODS: The expression of MEX3A in HCC was analysis using the data derived from the Cancer Genome Atlas (TCGA) dataset and further confirmed by HCC samples and cells lines. The roles of MEX3A in the proliferation, migration and sorafenib resistance were detected both in vitro and vivo. In addition, the underline mechanism was investigated. RESULTS: In this study, MEX3A expression was upregulated in HCC tissue and cell lines. Knockdown or overexpression of MEX3A disturbed the proliferation, migration and apoptosis of HCC cells by modulating the activation of Hippo signaling pathway. The expression of MEX3A was negatively associated with sorafenib sensitivity and upregulated in sorafenib resistant HCC cells. MEX3A knockdown facilitated the expression of WWC1, a negative modulator of Hippo signaling pathway, and led to increase of the phosphorylation of LATS1 and YAP1. Pharmacological inhibition of LATS1 or WWC1 overexpression alleviated the proliferative and migrated suppression and increased sorafenib sensitivity, whereas WWC1 inhibition using genetic interference strategy showed opposite trend in MEX3A knockdown HCC cells. Importantly, MEX3A knockdown led to growth and lung metastasis inhibition using xenograft model established by means of subcutaneous or tail vein injection. In addition, a combination of MEX3A knockdown and WWC1 overexpression dramatically enhances the growth inhibition of sorafenib in vivo. CONCLUSION: MEX3A may facilitate HCC progression and hinder sorafenib sensitivity via inactivating Hippo signaling. The present study suggested that targeting MEX3A can be served as a novel therapeutic strategy for HCC.

The RNA binding protein MEX3A promotes tumor progression of breast cancer by post-transcriptional regulation of IGFBP4.

PURPOSE: Breast cancer (BC) is the most frequent malignant tumor in women worldwide with exceptionally high morbidity. The RNA-binding protein MEX3A plays a crucial role in genesis and progression of multiple cancers. We attempted to explore its clinicopathological and functional significance in BC in which MEX3A is expressed. METHODS: The expression of MEX3A detected by RT-qPCR and correlated the results with clinicopathological variables in 53 BC patients. MEX3A and IGFBP4 profile data of BC patients were downloaded from TCGA and GEO database. Kaplan-Meier (KM) analysis was used to estimate the survival rate of BC patients. Western Blot, CCK-8, EdU, colony formation and flow cytometry were performed to investigate the role of MEX3A and IGFBP4 in BC cell proliferation, invasion and cell cycle in vitro. A subcutaneous tumor mouse model was constructed to analyze in vivo growth of BC cells after MEX3A knockdown. The interactions among MEX3A and IGFBP4 were measured by RNA pull-down and RNA immunoprecipitation. RESULTS: The expression of MEX3A was upregulated in BC tissues compared to adjacent tissues and high expression of MEX3A was associated with poor prognosis. Subsequent in vitro studies demonstrated that MEX3A knockdown inhibited BC cells proliferation and migration, as well as xenograft tumor growth in vivo. The expression of IGFBP4 was significantly negatively correlated with MEX3A in BC tissues. Mechanistic investigation showed that MEX3A binds to IGFBP4 mRNA in BC cells, decreasing IGFBP4 mRNA levels, which further activated the PI3K/AKT and other downstream signaling pathways implicated cell cycle progression and cell migration. CONCLUSION: Our results indicate that MEX3A plays a prominent oncogenic role in BC tumorigenesis and progression by targeting IGFBP4 mRNA and activating PI3K/AKT signaling, which can be used as a novel therapeutic target for BC.

Activation of insulin-like growth factor-1 receptor (IGF-1R) promotes growth of colorectal cancer through triggering the MEX3A-mediated degradation of RIG-I.

Insulin-like growth factor-1 receptor (IGF-1R) has been made an attractive anticancer target due to its overexpression in cancers. However, targeting it has often produced the disappointing results as the role played by cross talk with numerous downstream signalings. Here, we report a disobliging IGF-1R signaling which promotes growth of cancer through triggering the E3 ubiquitin ligase MEX3A-mediated degradation of RIG-I. The active ß-arrestin-2 scaffolds this disobliging signaling to talk with MEX3A. In response to ligands, IGF-1Rß activated the basal ßarr2 into its active state by phosphorylating the interdomain domain on Tyr64 and Tyr250, opening the middle loop (Leu130‒Cys141) to the RING domain of MEX3A through the conformational changes of ßarr2. The models of ßarr2/IGF-1Rß and ßarr2/MEX3A could interpret the mechanism of the activated-IGF-1R in triggering degradation of RIG-I. The assay of the mutants ßarr2Y64A and ßarr2Y250A further confirmed the role of these two Tyr residues of the interlobe in mediating the talk between IGF-1Rß and the RING domain of MEX3A. The truncated-ßarr2 and the peptide ATQAIRIF, which mimicked the RING domain of MEX3A could prevent the formation of ßarr2/IGF-1Rß and ßarr2/MEX3A complexes, thus blocking the IGF-1R-triggered RIG-I degradation. Degradation of RIG-I resulted in the suppression of the IFN-I-associated immune cells in the TME due to the blockade of the RIG-I-MAVS-IFN-I pathway. Poly(I:C) could reverse anti-PD-L1 insensitivity by recovery of RIG-I. In summary, we revealed a disobliging IGF-1R signaling by which IGF-1Rß promoted cancer growth through triggering the MEX3A-mediated degradation of RIG-I.

MEX3A promotes angiogenesis in colorectal cancer via glycolysis.

As a gastrointestinal malignancy, colorectal cancer (CRC) is a main cause of cancer-related deaths worldwide. Mex-3 RNA-binding family member A (MEX3A) is upregulated in multiple types of tumors and plays a critical role in tumor proliferation and metastasis. However, the function of MEX3A in CRC angiogenesis has not been fully understood. Hence, the aim of this study was to explore the role of MEX3A in CRC angiogenesis and investigate its underlying mechanisms. MEX3A expression in CRC was first investigated by bioinformatics means and then measured by qRT-PCR and Western blot. CCK-8 assay was employed to test cell viability. Angiogenesis assay was used to assess angiogenesis. The protein levels of VEGF, FGF and SDF-1 were evaluated using Western blot. The expression levels of MYC, HK2 and PGK1 were investigated by qRT-PCR. Extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) were determined by Seahorse XP 96. The levels of pyruvate, lactate, citric acid and malate were measured by corresponding kits. Bioinformatics analysis demonstrated high MEX3A expression in CRC tissues and MEX3A enrichment in glycolysis and angiogenesis pathways. Cell assays showed high MEX3A expression in CRC cells and its promoting effects in CRC cell proliferation and glycolysis as well as angiogenesis. Rescue experiment confirmed that glycolysis inhibitor 2-DG could offset the promoting effects of MEX3A on the proliferation, angiogenesis and glycolysis of CRC cells. In conclusion, MEX3A could facilitate CRC angiogenesis by activating the glycolytic pathway, suggesting that MEX3A may be a novel therapeutic target for CRC.

circGRAMD1B contributes to migration, invasion and epithelial-mesenchymal transition of lung adenocarcinoma cells via modulating the expression of SOX4.

Lung adenocarcinoma (LUAD) represents the subtype of non-small-cell lung cancer (NSCLC), with the high morbidity over the world. Mounting studies have highlighted the important roles of circular RNAs (circRNA) in cancers, including LUAD. This study mainly focused on revealing the role of circGRAMD1B and its relevant regulatory mechanism in LUAD cells. RT-qPCR and Western blot were conducted to detect the expression of target genes. Function assays were performed to determine the effect of related genes on migration, invasion, and epithelial-mesenchymal transition (EMT) of LUAD cells. Mechanism analyses were conducted to figure out the specific mechanism with regard to circGRAMD1B and its downstream molecules as well. Based on the experimental results, circGRAMD1B was upregulated in LUAD cells and promoted the migration, invasion, and EMT of LUAD cells. Mechanically, circGRAMD1B sponged miR-4428 to upregulate the expression of SOX4. In addition, SOX4 activated the expression of MEX3A at the transcriptional level, thereby modulating PI3K/AKT pathway to facilitate LUAD cell malignant behaviors. In conclusion, circGRAMD1B is discovered to modulate miR-4428/SOX4/MEX3A axis to further activate PI3K/AKT pathway, finally boosting migration, invasion, and EMT of LUAD cells.

Activation of insulin-like growth factor-1 receptor (IGF-1R) promotes growth of colorectal cancer through triggering the MEX3A-mediated degradation of RIG-I

Insulin-like growth factor-1 receptor (IGF-1R) has been made an attractive anticancer target due to its overexpression in cancers. However, targeting it has often produced the disappointing results as the role played by cross talk with numerous downstream signalings. Here, we report a disobliging IGF-1R signaling which promotes growth of cancer through triggering the E3 ubiquitin ligase MEX3A-mediated degradation of RIG-I. The active β-arrestin-2 scaffolds this disobliging signaling to talk with MEX3A. In response to ligands, IGF-1Rβ activated the basal βarr2 into its active state by phosphorylating the interdomain domain on Tyr64 and Tyr250, opening the middle loop (Leu130‒Cys141) to the RING domain of MEX3A through the conformational changes of βarr2. The models of βarr2/IGF-1Rβ and βarr2/MEX3A could interpret the mechanism of the activated-IGF-1R in triggering degradation of RIG-I. The assay of the mutants βarr2Y64A and βarr2Y250A further confirmed the role of these two Tyr residues of the interlobe in mediating the talk between IGF-1Rβ and the RING domain of MEX3A. The truncated-βarr2 and the peptide ATQAIRIF, which mimicked the RING domain of MEX3A could prevent the formation of βarr2/IGF-1Rβ and βarr2/MEX3A complexes, thus blocking the IGF-1R-triggered RIG-I degradation. Degradation of RIG-I resulted in the suppression of the IFN-I-associated immune cells in the TME due to the blockade of the RIG-I-MAVS-IFN-I pathway. Poly(I:C) could reverse anti-PD-L1 insensitivity by recovery of RIG-I. In summary, we revealed a disobliging IGF-1R signaling by which IGF-1Rβ promoted cancer growth through triggering the MEX3A-mediated degradation of RIG-I.

Identifying the E2F3-MEX3A-KLF4 signaling axis that sustains cancer cells in undifferentiated and proliferative state.

Rationale: Dysregulation of signaling that governs self-renewal and differentiation of intestinal stem cells (ISCs) is a major cause of colorectal cancer (CRC) initiation and progression. Methods: qRT-PCR, western blotting, in situ hybridization, immunohistochemistry and immunofluorescence assays were used to detect the expression levels of MEX3A, KLF4 and E2F3 in CRC tissues. The biological functions of MEX3A were studied using Mex3a knockout (KO) and intestinal epithelium specific conditional knockout (cKO) mice, AOM-DSS mouse colorectal tumor model, Apc floxed mouse tumor model and intestinal and tumor organoids. Transcriptomic RNA sequencing (RNA-seq), RNA crosslinking immunoprecipitation (CLIP) and luciferase reporter assays were performed to explore the molecular mechanisms of MEX3A. Results: RNA-binding protein MEX3A, a specific ISC marker gene, becomes ectopically upregulated upon CRC and its levels negatively correlate with patient survival prognosis. MEX3A functions as an oncoprotein that retains cancer cells in undifferentiated and proliferative status and it enhances their radioresistance to DNA damage. Mechanistically, a rate limiting factor of cellular proliferation E2F3 induces MEX3A, which in turn activates WNT pathway by directly suppressing expression of its pro-differentiation transcription factor KLF4. Knockdown of MEX3A with siRNA or addition of KLF4 agonist significantly suppressed tumor growth both by increasing differentiation status of cancer cells and by suppressing their proliferation. Conclusions: It identifies E2F3-MEX3A-KLF4 axis as an essential coordinator of cancer stem cell self-renewal and differentiation, representing a potent new druggable target for cancer differentiation therapy.

Grass Carp Mex3A Promotes Ubiquitination and Degradation of RIG-I to Inhibit Innate Immune Response.

As one of the Mex3 family members, Mex3A is crucial in cell proliferation, migration, and apoptosis in mammals. In this study, a novel gene homologous to mammalian Mex3A (named CiMex3A, MW368974) was cloned and identified in grass carp, which is 1,521 bp in length encoding a putative polypeptide of 506 amino acids. In CIK cells, CiMex3A is upregulated after stimulation with LPS, Z-DNA, and especially with intracellular poly(I:C). CiMex3A overexpression reduces the expressions of IFN1, ISG15, and pro-inflammatory factors IL8 and TNFα; likewise, Mex3A inhibits IRF3 phosphorylation upon treatment with poly(I:C). A screening test to identify potential targets suggested that CiMex3A interacts with RIG-I exclusively. Co-localization analysis showed that Mex3A and RIG-I are simultaneously located in the endoplasmic reticulum, while they rarely appear in the endosome, mitochondria, or lysosome after exposure to poly(I:C). However, RIG-I is mainly located in the early endosome and then transferred to the late endosome following stimulation with poly(I:C). Moreover, we investigated the molecular mechanism underlying CiMex3A-mediated suppression of RIG-I ubiquitination. The results demonstrated that Mex3A truncation mutant (deletion in the RING domain) can still interact physically with RIG-I, but fail to degrade it, suggesting that Mex3A also acts as a RING-type E3 ubiquitin ligase. Taken together, this study showed that grass carp Mex3A can interact with RIG-I in the endoplasmic reticulum following poly(I:C) stimulation, and then Mex3A facilitates the ubiquitination and degradation of RIG-I to inhibit IRF3-mediated innate antiviral immune response.

SMYD2 epigenetically activates MEX3A and suppresses CDX2 in colorectal cancer cells to augment cancer growth.

Dysfunction of the protein methyltransferase SET and MYND domain-containing protein 2 (SMYD2) is frequently linked to multiple diseases including cancer. The study focused on the role of SMYD2 in colorectal cancer (CRC) development. SMYD2 was expressed at high levels in CRC tissues and cells. Knockdown of SMYD2 in LOVO cells reduced cell proliferation, migration and invasiveness in vitro and it suppressed xenograft tumorigenesis in vivo. Overexpression of SMYD2 in HCT116 cells led to inverse trends. Mex-3 RNA binding family member A (MEX3A) was predicted as a target of SMYD2. Chromatin immunoprecipitation (ChIP)-reverse transcription quantitative polymerase chain reaction (qPCR) and cellular assays were performed and validated that SMYD2 activated MEX3A expression by promoting H3K36me2 modification on its promoter. Data in the STRING bioinformatics system indicated caudal type homeobox 2 (CDX2) as an important MEX3A-related gene. Silencing of MEX3A alone blocked proliferation and growth of CRC cells in vitro and in vivo, whereas MEX3A overexpression promoted cell growth by suppressing CDX2. In rescue experiments, MEX3A silencing suppressed the cell growth augmented by SMYD2, and CDX2 downregulation restored the malignance of cancer cells inhibited by MEX3A silencing. Taken together, this study reports that SMYD2-mediated activation of MEX3A augments progression of CRC by suppressing CDX2.

RNA-binding protein MEX3A controls G1/S transition via regulating the RB/E2F pathway in clear cell renal cell carcinoma.

MEX3A is an RNA-binding protein that mediates mRNA decay through binding to 3' untranslated regions. However, its role and mechanism in clear cell renal cell carcinoma remain unknown. In this study, we found that MEX3A expression was transcriptionally activated by ETS1 and upregulated in clear cell renal cell carcinoma. Silencing MEX3A markedly reduced clear cell renal cell carcinoma cell proliferation in vitro and in vivo. Inhibiting MEX3A induced G1/S cell-cycle arrest. Gene set enrichment analysis revealed that E2F targets are the central downstream pathways of MEX3A. To identify MEX3A targets, systematic screening using enhanced cross-linking and immunoprecipitation sequencing, and RNA-immunoprecipitation sequencing assays were performed. A network of 4,000 genes was identified as potential targets of MEX3A. Gene ontology analysis of upregulated genes bound by MEX3A indicated that negative regulation of the cell proliferation pathway was highly enriched. Further assays indicated that MEX3A bound to the CDKN2B 3' untranslated region, promoting its mRNA degradation. This leads to decreased levels of CDKN2B and an uncontrolled cell cycle in clear cell renal cell carcinoma, which was confirmed by rescue experiments. Our findings revealed that MEX3A acts as a post-transcriptional regulator of abnormal cell-cycle progression in clear cell renal cell carcinoma.

RNA-Binding Protein MEX3A Interacting with DVL3 Stabilizes Wnt/ß-Catenin Signaling in Endometrial Carcinoma.

Disease recurrence and metastasis lead to poor prognosis in patients with advanced endometrial carcinoma (EC). RNA-binding proteins (RBPs) are closely associated with tumor initiation and metastasis, but the function and molecular mechanisms of RBPs in EC are unclear. RBPs were screened and identified using the TCGA, GEO, and RBPTD databases. The effect of MEX3A on EC was verified by in vitro and in vivo experiments. Gene set enrichment analysis (GSEA), immunofluorescence (IF), and co-immunoprecipitation (Co-IP) were used to identify potential molecular mechanisms of action. We identified 148 differentially expressed RBPs in EC. MEX3A was upregulated and related to poor prognosis in patients with EC. In vitro and vivo experiments demonstrated that MEX3A promoted the growth, migration, and invasion capacities of EC cells. Mechanistically, DVL3, a positive regulator of the Wnt/ß-catenin pathway, also increased the proliferation and metastasis of EC cells. MEX3A enhanced EMT and played a pro-carcinogenic role by interacting with DVL3 to stabilize ß-catenin and upregulated the expression of its downstream target genes. MEX3A is upregulated in EC and promotes tumor progression by activating EMT and regulating the Wnt/ß-catenin pathway via DVL3. MEX3A may therefore be a novel therapeutic target for EC.

MEX3A promotes proliferation and migration of colorectal cancer cells via PI3K/Akt signaling pathway / 解剖学报

Objective To investigate the expression of MEX3A in colorectal cancer (CRC), and to explore the effect and mechanism of MEX3A on the proliferation and migration of colorectal cancer cells. Methods Totally 327 cases of data(41 normal tissues and 286 tumor tissues) were obtained from TCGA database, and 104 cases of clinical samples (77 cases tissues and 27 paracancerous tissues) were collected for immunohistochemistry, then analysed the differences in MEX3A expression between CRC tissues and normal tissues. Western blotting and immunofluorescence staining were used to evaluate the differential expression of MEX3A in CRC cell lines. CL187 cells were selected as the follow-up research vector. Small interfering RNA of MEX3A(siMEX3A) was transfected into CL187 cells to inhibit the expression of MEX3A. The proliferation and migration of CL187 cells were measured by MTT, colony formation assay and Transwell assay. The expression of PI3K, p-PI3K, Akt and p-Akt were detected by Western blotting. Results TCGA database, immunohistochemistry and Western blotting analysis showed that MEX3A was highly expressed in colorectal cancer. The result of immunofluorescence staining showed that MEX3A was concentrated in the cytoplasm and the nucleus. In MTT, colony formation assay and Transwell assay, the proliferation and migration ability of CL187 cells in siMEX3A group decreased significantly than those in control group (P<0.05). Western blotting result showed that the expression of p-PI3K and p-Akt in siMEX3A group down-regulated significantly (P<0.05), and the inhibition of proliferation and migration ability of CL187 cells induced by siMEX3A group could be reversed by 740 Y-P via activating the PI3K/Akt signaling pathway. Conclusion MEX3A is highly expressed in colorectal cancer and promotes the proliferation and migration of CRC cells via PI3K/Akt signaling pathway.

Mex-3 RNA binding MEX3A promotes the proliferation and migration of breast cancer cells via regulating RhoA/ROCK1/LIMK1 signaling pathway.

Breast cancer has been known as cancer with high mortality rates. It has been studied that MEX3A (Mex-3 RNA Binding Family Member A) is involved in carcinogenesis by accelerating cancer proliferation and migration. Therefore, this research aimed to study how MEX3A regulates the biological behaviors of breast cancer. Firstly, we used GEPIA and KM-plotter databases to evaluate MEX3A expression in human breast cancer tissue compared to adjacent normal tissue. Immunohistochemistry was employed to assess MEX3A protein expression in clinical specimens. MEX3A mRNA expression level was assessed through quantitative real-time PCR (RT-qPCR). Western blotting was used to detect protein expression. Moreover, Cell Count Kit-8 (CCK-8) assay, wound healing assay and transwell invasion assay were used to determine the proliferation, migration and invasion of breast cancer cells, respectively. Our study found that MEX3A expression level was much higher in human breast cancer tissues as compared to adjacent normal tissues. Similarly, breast cancer cell lines showed higher expression of MEX3A as compared to the normal breast cells. This higher expression of MEX3A was linked with the poor survival of breast cancer. Moreover, we found that overexpression of MEX3A stimulated proliferation and migration in the breast cancer cells. However, inhibition of MEX3A significantly reduced the proliferation and migration of breast cancer cells. In addition, we determined that MEX3A could activate RhoA/ROCK1/LIMK1 signaling in the breast cancer cells. Overall, our study concluded that MEX3A promotes its migration and proliferation in breast cancer cells via modulating RhoA/ROCK1/LIMK1 signaling pathway.

Targeting MEX3A attenuates metastasis of breast cancer via ß-catenin signaling pathway inhibition.

Metastasis is the major cause of mortality in patients with breast cancer. Understanding the metastatic mechanism to guide clinical diagnoses and the treatment of breast cancer remains a challenge. We found that the expression of Mex-3 RNA binding family member A (MEX3A) was upregulated significantly and related to tumor grade in breast cancer. The results of in vitro and in vivo studies showed that knockdown of MEX3A inhibited the metastasis and impaired the stemness of breast cancer cells. Furthermore, activation of the ß-catenin signaling pathway was discovered as a molecular intermediate of MEX3A-mediated regulation. We also found that ectopic expression of ß-catenin restored the migration ability, invasion ability, and CD44+/CD24- percentage of MDA-MB-231 and BT549 cells when MEX3A was depleted. In addition, we revealed that MEX3A positively regulated the expression of ß-catenin by downregulating Dickkopf WNT signaling pathway inhibitor 1 (DKK1) expression. Therefore, a previously undiscovered role of MEX3A comprising a critical contribution to promoting metastasis and maintaining the stemness of breast cancer via the Wnt/ß-catenin pathway was demonstrated in the present study.

Oncogenic Potential of the Dual-Function Protein MEX3A.

MEX3A belongs to the MEX3 (Muscle EXcess) protein family consisting of four members (MEX3A-D) in humans. Characteristic for MEX3 proteins is their domain structure with 2 HNRNPK homology (KH) domains mediating RNA binding and a C-terminal really interesting new gene (RING) domain that harbors E3 ligase function. In agreement with their domain composition, MEX3 proteins were reported to modulate both RNA fate and protein ubiquitination. MEX3 paralogs exhibit an oncofetal expression pattern, they are severely downregulated postnatally, and re-expression is observed in various malignancies. Enforced expression of MEX3 proteins in various cancers correlates with poor prognosis, emphasizing their oncogenic potential. The latter is supported by MEX3A's impact on proliferation, self-renewal as well as migration of tumor cells in vitro and tumor growth in xenograft studies.