Adenoviral delivery of the EMX2 gene suppresses growth in human gastric cancer

EMX2 inhibits clear cell renal cell carcinoma progress via modulating Akt/FOXO3a pathway

Empty spiracles homeobox 2 (EMX2) is initially identified as a key transcription factor that plays an essential role in the regulation of neuronal development and some brain disorders. Recently, several studies emphasized that EMX2 could as a tumor suppressor, but its role in human clear cell renal cell carcinoma (ccRCC) remains unclear. In the present study, we investigated the role and underlying mechanism of EMX2 in the regulation of ccRCC progress. Our results demonstrated that EMX2 expression was markedly decreased in ccRCC tissues and cell lines, and low EMX2 expression predicted the poor prognosis of ccRCC patients. In addition, forced expression of EMX2 significantly inhibited the cell growth, migration, and invasion in vitro, as well as ccRCC tumor growth in nude mice, via, at least in part, regulating Akt/FOXO3a pathway. In detail, EMX2 could attenuate the phosphorylation levels of Akt and FOXO3a, and increase FOXO3a expression without affecting total Akt expression in vivo and in vitro. Meanwhile, shRNA-mediated knockdown of FOXO3a expression could obviously attenuate the effects of EMX2 on cell growth, migration, invasion, and tumor growth. Furthermore, EMX2 could significantly attenuate the interaction between Akt and FOXO3a. Taken together, our results demonstrated that EMX2 could inhibit ccRCC progress through, at least in part, modulating Akt/FOXO3a signaling pathway, thus representing a novel role and underlying mechanism of EMX2 in the regulation of ccRCC progress.

Identification of genetic associations and functional SNPs of bovine KLF6 gene on milk production traits in Chinese holstein

BACKGROUND

Our previous research identified the Kruppel like factor 6 (KLF6) gene as a prospective candidate for milk production traits in dairy cattle. The expression of KLF6 in the livers of Holstein cows during the peak of lactation was significantly higher than that during the dry and early lactation periods. Notably, it plays an essential role in activating peroxisome proliferator-activated receptor α (PPARα) signaling pathways. The primary aim of this study was to further substantiate whether the KLF6 gene has significant genetic effects on milk traits in dairy cattle.

RESULTS

Through direct sequencing of PCR products with pooled DNA, we totally identified 12 single nucleotide polymorphisms (SNPs) within the KLF6 gene. The set of SNPs encompasses 7 located in 5' flanking region, 2 located in exon 2 and 3 located in 3' untranslated region (UTR). Of these, the g.44601035G > A is a missense mutation that resulting in the replacement of arginine (CGG) with glutamine (CAG), consequently leading to alterations in the secondary structure of the KLF6 protein, as predicted by SOPMA. The remaining 7 regulatory SNPs significantly impacted the transcriptional activity of KLF6 following mutation (P < 0.005), manifesting as changes in transcription factor binding sites. Additionally, 4 SNPs located in both the UTR and exons were predicted to influence the secondary structure of KLF6 mRNA using the RNAfold web server. Furthermore, we performed the genotype-phenotype association analysis using SAS 9.2 which found all the 12 SNPs were significantly correlated to milk yield, fat yield, fat percentage, protein yield and protein percentage within both the first and second lactations (P < 0.0001 ~ 0.0441). Also, with Haploview 4.2 software, we found the 12 SNPs linked closely and formed a haplotype block, which was strongly associated with five milk traits (P < 0.0001 ~ 0.0203).

CONCLUSIONS

In summary, our study represented the KLF6 gene has significant impacts on milk yield and composition traits in dairy cattle. Among the identified SNPs, 7 were implicated in modulating milk traits by impacting transcriptional activity, 4 by altering mRNA secondary structure, and 1 by affecting the protein secondary structure of KLF6. These findings provided valuable molecular insights for genomic selection program of dairy cattle.

The tissue-specificity associated region and motif of an emx2 downstream enhancer CNE2.04 in zebrafish

BACKGROUND

Expression level of EMX2 plays an important role in the development of nervous system and cancers. CNE2.04, a conserved enhancer downstream of emx2, drives fluorescent protein expression in the similar pattern of emx2.

METHODS

CNE2.04 truncated or motif-mutated transgenic reporter plasmids were constructed and injected into the zebrafish fertilized egg with Tol2 mRNA at the unicellular stage of zebrafish eggs. The green fluorescence expression patterns were observed at 24, 48, and 72 hpf, and the fluorescence rates of different tissues were counted at 48 hpf.

RESULTS

Compared to CNE2.04, CNE2.04-R400 had comparable enhancer activity, while the tissue specificity of CNE2.04-L400 was obviously changed. Motif CCCCTC mutation obviously changed the enhancer activity, while motif CCGCTC mutations also changed it.

CONCLUSION

Due to their correlation with tissue specificity, CNE2.04-R400 is associated with the tissue-specificity of CNE2.04, and motif CCCCTC plays an important role in the enhancer activity of CNE2.04.

EMX1 functions as a tumor inhibitor in spinal cord glioma through transcriptional suppression of WASF2 and inactivation of the Wnt/β-catenin axis

BACKGROUND

Gliomas are the most frequent and aggressive cancers in the central nervous system, and spinal cord glioma (SCG) is a rare class of the gliomas. Empty spiracles homobox genes (EMXs) have shown potential tumor suppressing roles in glioma, but the biological function of EMX1 in SCG is unclear.

METHODS

The EMX1 expression in clinical tissues of patients with SCG was examined. SCG cells were extracted from the tissues, and altered expression of EMX1 was then introduced to examine the role of EMX1 in cell growth and invasiveness in vitro. Xenograft tumors were induced in nude mice for in vivo validation. The targets of EXM1 were predicted via bioinformatic analysis and validated by luciferase and ChIP-qPCR assays. Rescue experiments were conducted to validate the involvements of the downstream molecules.

RESULTS

EMX1 was poorly expressed in glioma, which was linked to decreased survival rate of patients according to the bioinformatics prediction. In clinical tissues, EMX1 was poorly expressed in SCG, especially in the high-grade tissues. EMX1 upregulation significantly suppressed growth and metastasis of SCG cells in vitro and in vivo. EMX1 bound to the promoter of WASP family member 2 (WASF2) to suppress its transcription. Restoration of WASF2 blocked the tumor-suppressing effect of EMX1. EMX1 suppressed Wnt/β-catenin signaling activity by inhibiting WASF2. Coronaridine, a Wnt/β-catenin-specific antagonist, blocked SCG cell growth and metastasis induced by WASF2.

CONCLUSION

This study elucidates that EMX1 functions as a tumor inhibitor in SCG by suppressing WASF2-dependent activation of the Wnt/β-catenin axis.

Genetic Regulation of Vertebrate Forebrain Development by Homeobox Genes

Forebrain development in vertebrates is regulated by transcription factors encoded by homeobox, bHLH and forkhead gene families throughout the progressive and overlapping stages of neural induction and patterning, regional specification and generation of neurons and glia from central nervous system (CNS) progenitor cells. Moreover, cell fate decisions, differentiation and migration of these committed CNS progenitors are controlled by the gene regulatory networks that are regulated by various homeodomain-containing transcription factors, including but not limited to those of the Pax (paired), Nkx, Otx (orthodenticle), Gsx/Gsh (genetic screened), and Dlx (distal-less) homeobox gene families. This comprehensive review outlines the integral role of key homeobox transcription factors and their target genes on forebrain development, focused primarily on the telencephalon. Furthermore, links of these transcription factors to human diseases, such as neurodevelopmental disorders and brain tumors are provided.

Prognostic significance of AP-2α/γ targets as cancer therapeutics

Identifying genes with prognostic importance could improve cancer treatment. An increasing number of reports suggest the existence of successful strategies based on seemingly "untargetable" transcription factors. In addition to embryogenesis, AP-2 transcription factors are known to play crucial roles in cancer development. Members of this family can be used as prognostic factors in oncological patients, and AP-2α/γ transcription factors were previously investigated in our pan-cancer comparative study using their target genes. The present study investigates tumors that were previously found similar with an emphasis on the possible role of AP-2 factors in specific cancer types. The RData workspace was loaded back to R environment and 3D trajectories were built via Monocle3. The genes that met the requirement of specificity were listed using top_markers(), separately for mutual and unique targets. Furthermore, the candidate genes had to meet the following requirements: correlation with AP-2 factor (through Correlation AnalyzeR) and validated prognostic importance (using GEPIA2 and subsequently KM-plotter or LOGpc). Eventually, the ROC analysis was applied to confirm their predictive value; co-dependence of expression was visualized via BoxPlotR. Some similar tumors were differentiated by AP-2α/γ targets with prognostic value. Requirements were met by only fifteen genes (EMX2, COL7A1, GRIA1, KRT1, KRT14, SLC12A5, SEZ6L, PTPRN, SCG5, DPP6, NTSR1, ARX, COL4A3, PPEF1 and TMEM59L); of these, the last four were excluded based on ROC curves. All the above genes were confronted with the literature, with an emphasis on the possible role played by AP-2 factors in specific cancers. Following ROC analysis, the genes were verified using immunohistochemistry data and progression-related signatures. Staining differences were observed, as well as co-dependence on the expression of e.g. CTNNB1, ERBB2, KRAS, SMAD4, EGFR or MKI67. In conclusion, prognostic value of targets suggested AP-2α/γ as candidates for novel cancer treatment. It was also revealed that AP-2 targets are related to tumor progression and that some mutual target genes could be inversely regulated.

Functional New Transcription Factors (TFs) Associated with Cervical Cancer

The goal of this research was to find noval transcription factors (TFs) that are involved in cervical carcinogenesis. The Gene Expression Omnibus (GEO) database was utilized to analyze ten cervical cancer datasets using the Robust Rank Aggregation (RRA) technique. Survival and differential expression were validated using GEPIA (Gene Expression Profiling Interactive Analysis). The transcriptional regulatory network and putative targets were built using Cytoscape. A real-time PCR (quantitative real-time polymerase chain reaction) experiment was used to confirm the mRNA expression. Using public cervical cancer single-cell RNA-sequencing (scRNA-seq), bulk TCGA-CESC RNA-seq, and microarray datasets, coexpression correlations between putative targets and TFs were confirmed. After combining the results of 10 datasets, 8 TFs, including EMX2 (Empty Spiracles Homeobox 2), were chosen among 385 robust DEGs. In the normal female reproductive tract, EMX2 is extensively expressed, but it is reduced in cervical cancer. Overexpression EMX2 suppresses the proliferation of HeLa cells. 12 potential targets of EMX2 were selected. Our research has revealed evidence that EMX2 acted as a tumor suppressor in cervical cancer and PDZRN3 might be possible target of EMX2 in cervical cancer. It might be a therapeutic target in the future.

Empty spiracles homeobox genes EMX1 and EMX2 regulate WNT pathway activation in sarcomagenesis

Background

Sarcomas are a very heterogeneous group of tumors with intrinsic developmental programs derived from the cell of origin. This implies a functional hierarchy inside tumors governed by sarcoma stem cells. Therefore, genetic and/or epigenetic changes profoundly affect the biology of sarcoma tumor stem cells. EMX genes are proposed to be transcription factors that are involved in the sarcomagenesis process, regardless of the neural or mesodermal embryological sarcoma origin. It has been shown that EMX1 or EMX2 overexpression reduces tumorigenic properties, while reducing the levels of these genes enhances these properties. Furthermore, it has been shown that EMX genes decrease the expression of stem cell regulatory genes and the stem cell phenotype. Taken together, these results indicate that the EMX1 and EMX2 genes negatively regulate these tumor-remodeling populations or sarcoma stem cells, acting as tumor suppressors in sarcoma.

Methods

Bioinformatic analysis, quantitative mRNA and protein expression analysis, cell models of sarcoma by ectopic expression of EMX genes. By cell biology methods we measured tumorigenesis and populations enriched on stem cell phenotypes, either in vitro or in vivo.

Results

In this work, we showed that the canonical Wnt pathway is one of the mechanisms that explains the relationships of EMX1/EMX2 and stem cell genes in sarcoma. The Wnt-EMX1/EMX2 relationship was validated in silico with sarcoma patient datasets, in vitro in primary derived sarcoma cell lines, and in vivo. EMX expression was found to negatively regulate the Wnt pathway. In addition, the constitutive activation of the Wnt pathway revers to a more aggressive phenotype with stem cell properties, and stemness gene transcription increased even in the presence of EMX1 and/or EMX2 overexpression, establishing the relationship among the Wnt pathway, stem cell genes and the EMX transcription factors.

Conclusions

Our data showed that Empty Spiracles Homeobox Genes EMX1 and EMX2 represses WNT signalling and activation of WNT pathway bypass EMX-dependent stemness repression and induces sarcomagenesis. These results also suggest the relevance of the Wnt/b-catenin/stemness axis as a therapeutic target in sarcoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02048-9.

Regulation of sarcomagenesis by the empty spiracles homeobox genes EMX1 and EMX2

The EMX (Empty Spiracles Homeobox) genes EMX1 and EMX2 are two homeodomain gene members of the EMX family of transcription factors involved in the regulation of various biological processes, such as cell proliferation, migration, and differentiation, during brain development and neural crest migration. They play a role in the specification of positional identity, the proliferation of neural stem cells, and the differentiation of certain neuronal cell phenotypes. In general, they act as transcription factors in early embryogenesis and neuroembryogenesis from metazoans to higher vertebrates. The EMX1 and EMX2's potential as tumor suppressor genes has been suggested in some cancers. Our work showed that EMX1/EMX2 act as tumor suppressors in sarcomas by repressing the activity of stem cell regulatory genes (OCT4, SOX2, KLF4, MYC, NANOG, NES, and PROM1). EMX protein downregulation, therefore, induced the malignance and stemness of cells both in vitro and in vivo. In murine knockout (KO) models lacking Emx genes, 3MC-induced sarcomas were more aggressive and infiltrative, had a greater capacity for tumor self-renewal, and had higher stem cell gene expression and nestin expression than those in wild-type models. These results showing that EMX genes acted as stemness regulators were reproduced in different subtypes of sarcoma. Therefore, it is possible that the EMX genes could have a generalized behavior regulating proliferation of neural crest-derived progenitors. Together, these results indicate that the EMX1 and EMX2 genes negatively regulate these tumor-altering populations or cancer stem cells, acting as tumor suppressors in sarcoma.

Downregulation of enhancer RNA EMX2OS is associated with poor prognosis in kidney renal clear cell carcinoma

Enhancer RNAs are a subclass of long non-coding RNAs transcribed from enhancer regions that play an important role in the transcriptional regulation of genes. However, their role in kidney renal clear cell carcinoma (KIRC) is largely unknown. Herein, we identified the key enhancer RNAs in KIRC via an integrated data analysis method. Gene expression profiles and clinical data of KIRC and 32 other cancer types were acquired using the University of California Santa Cruz Xena platform. Reported enhancer RNAs and genes regulated by them were selected as putative enhancer RNA-target pairs. Kaplan-Meier survival and correlation analyses were performed to identify the key enhancer RNAs. Finally, EMX2OS was identified as the enhancer RNA most associated with survival, with EMX2 as its target. EMX2OS downregulation was significantly associated with higher histological grade, advanced stage, and poorer prognosis. The results were validated in pan-cancer data from The Cancer Genome Atlas and RT-qPCR analysis of 12 pairs of KIRC and normal real-world samples. Functional enrichment analysis indicated that several metabolism-associated signaling pathways were enriched. This study demonstrated that EMX2OS is a key metabolism-associated enhancer RNA in KIRC with a favorable impact on survival and may be a novel therapeutic target in KIRC.

Long non-coding RNA CCAT1 is overexpressed in endometrial cancer and regulates growth and transcriptome of endometrial adenocarcinoma cells

BACKGROUND

Long non-coding RNAs (lncRNAs) play important roles in regulation of gene expression and are involved in pathogenesis of different diseases including cancer. Recent studies suggested the lncRNA Colon cancer associated transcript-1 (CCAT1) to act as putative oncogene. In this study, to elucidate the role of this lncRNA in endometrial cancer, we examined its expression in normal endometrium and type 1 endometrial cancer and knocked down its expression in endometrial cancer cell lines followed by transcriptome and pathway analyses.

METHODS

CCAT1 expression was examined in 100 tissue samples of normal endometrium and type 1 endometrial cancer tissues by means of RT-qPCR. Knockdown of CCAT1 expression in HEC-1B and RL95/2 endometrial cancer cells was performed by siRNA transfection. Affymetrix GeneChip arrays were used to elucidate the effect of both lncRNAs on the transcriptome of these cell lines.

RESULTS

Median CCAT1 expression was found to be 9.3-fold higher in endometrial cancer when compared to normal endometrium (p < 0.05). In contrast to premenopausal endometrium and G1, G2 and G3 graded endometrial cancer, CCAT1 expression was nearly absent in postmenopausal tissue. Knockdown of CCAT1 by transient siRNA transfection significantly reduced proliferation of HEC-1B cancer cells in vitro by 35.5 % 6 days after transfection and notably reduced their colony formation ability. Affymetrix microarray and Ingenuity pathway analyses revealed a set of up- or down-regulated genes in transfected ERα-negative HEC-1B cells forming a network controlled by the key regulators TNF and TP53, including genes known to be involved in growth control, providing putative molecular mechanisms underlying the observed growth inhibition of HEC-1B cells. In contrast, CCAT1 knockdown in ERα-positive RL95/2 cells did not significantly affect proliferation, but resulted in down-regulation of a network of ERα target genes.

CONCLUSIONS

Given that the lncRNA CCAT1 was found to be overexpressed in endometrial cancer, affected the growth of HEC-1B cells and the expression of growth regulatory genes, our data suggest CCAT1 to exert oncogenic functions in endometrial cancer and encourage further studies to examine to what extent this lncRNA might be a potential therapy target in this cancer entity.

The downregulation of lncRNA EMX2OS might independently predict shorter recurrence-free survival of classical papillary thyroid cancer

Homeobox protein Emx2 is a transcription factor that is encoded by the EMX2 gene. In this study, using data from the Cancer Genome Atlas-Thyroid Cancer (TCGA-THCA), we aimed to examine the expression profile of EMX2 and its antisense transcript EMX2OS in papillary thyroid cancer (PTC), their prognostic value and potential regulatory networks. Results showed that in the three variants of PTC, EMX2 was significantly downregulated in classical PTC, while EMX2OS were significantly downregulated in follicular and classical PTC, compared with adjacent normal tissues. Kaplan-Meier survival curves showed that EMX2 and EMX2OS expression was not related to RFS in follicular PTC. In comparison, the high EMX2 or EMX2OS group were associated with better RFS compared with their respective low expression group in classical PTC (p = 0.007 and 0.004 respectively). Correlation analysis showed that EMX2 and EMX2OS were highly co-expressed in PTC tissues (Spearman’s r = 0.83). By performing stepwise regression, we found that EMX2OS was better than EMX2 in predicting RFS in classical PTC. Multivariate analysis confirmed that high EMX2OS expression was an independent indicator of favorable RFS in classical PTC (HR: 0.239, 95%CI: 0.100 = 0.569, p = 0.001), after adjustment of pathological stages and residual tumors. By performing in silico analysis, we found that the genes co-expressed with EMX2 or EMX2OS were highly overlapped. KEGG pathway analysis showed that these genes were enriched in the ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling, protein digestion and absorption and proteoglycans in cancer pathways, which are closely related to cancer initiation and progression. Based on the findings, we infer that decreased EMX2OS expression might be a valuable prognostic biomarker of unfavorable RFS in classical PTC.

The expression of EMX2 lead to cell cycle arrest in glioblastoma cell line

Background

Glioblastoma (GB) is a highly invasive primary brain tumor that nearly always systematically recurs at the site of resection despite aggressive radio-chemotherapy. Previously, we reported a gene expression signature related to tumor infiltration. Within this signature, the EMX2 gene encodes a homeodomain transcription factor that we found was down regulated in glioblastoma. As EMX2 is reported to play a role in carcinogenesis, we investigated the impact of EMX2 overexpression in glioma-related cell lines.

Methods

For that purpose, we constructed tetracycline-inducible EMX2 expression lines. Transfected cell phenotypes (proliferation, cell death and cell cycle) were assessed in time-course experiments.

Results

Restoration of EMX2 expression in U87 glioblastoma cells significantly inhibited cell proliferation. This inhibition was reversible after EMX2 removal from cells. EMX2-induced proliferative inhibition was very likely due to cell cycle arrest in G1/S transition and was not accompanied by signs of cell death.

Conclusion

Our results suggest that EMX2 may constitute a putative therapeutic target for GB treatment.

Further studies are required to decipher the gene networks and transduction signals involved in EMX2’s effect on cell proliferation.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5094-y) contains supplementary material, which is available to authorized users.

EMX2 gene expression predicts liver metastasis and survival in colorectal cancer

BACKGROUND

The Empty Spiracles Homeobox (EMX-) 2 gene has been associated with regulation of growth and differentiation in neuronal development. While recent studies provide evidence that EMX2 regulates tumorigenesis of various solid tumors, its role in colorectal cancer remains unknown. We aimed to assess the prognostic significance of EMX2 expression in stage III colorectal adenocarcinoma.

METHODS

Expression levels of EMX2 in human colorectal cancer and adjacent mucosa were assessed by qRT-PCR technology, and results were correlated with clinical and survival data. siRNA-mediated knockdown and adenoviral delivery-mediated overexpression of EMX2 were performed in order to investigate its effects on the migration of colorectal cancer cells in vitro.

RESULTS

Compared to corresponding healthy mucosa, colorectal tumor samples had decreased EMX2 expression levels. Furthermore, EMX2 down-regulation in colorectal cancer tissue was associated with distant metastasis (M1) and impaired overall patient survival. In vitro knockdown of EMX2 resulted in increased tumor cell migration. Conversely, overexpression of EMX2 led to an inhibition of tumor cell migration.

CONCLUSIONS

EMX2 is frequently down-regulated in human colorectal cancer, and down-regulation of EMX2 is a prognostic marker for disease-free and overall survival. EMX2 might thus represent a promising therapeutic target in colorectal cancer.

Empty Spiracles Homeobox 2 (EMX2) Inhibits the Invasion and Tumorigenesis in Colorectal Cancer Cells

Empty spiracles homeobox 2 (EMX2) is a homeodomain-containing transcription factor that plays an essential role in tumorigenesis. However, to the best of our knowledge, the role of EMX2 in human colorectal cancer (CRC) is still unclear. Thus, the aim of this study was to investigate the expression and role of EMX2 in CRC. Our results demonstrated that the expression of EMX2 was greatly decreased in CRC tissues and cell lines. Overexpression of EMX2 significantly inhibited the proliferation in vitro and CRC tumor growth in nude mice. In addition, EMX2 also inhibited the migration and invasion of CRC cells. Mechanically, overexpression of EMX2 downregulated the expression levels of β-catenin, cyclin D1, and c-Myc in CRC cells. Taken together, our study demonstrates that EMX2 inhibits proliferation and tumorigenesis through inactivation of the Wnt/β-catenin pathway in CRC cells. Therefore, EMX2 may be a potential therapeutic target for the treatment of CRC.

EMX2 Is a Predictive Marker for Adjuvant Chemotherapy in Lung Squamous Cell Carcinomas

Background

Squamous cell carcinomas (SCC) account for approximately 30% of non-small cell lung cancer (NSCLC). Current staging methods do not adequately predict outcome for this disease. EMX2 is a homeo-domain containing transcription factor known to regulate a key developmental pathway. This study assessed the significance of EMX2 as a prognostic and predictive marker for resectable lung SCC.

Methods

Two independent cohorts of patients with lung SCC undergoing surgical resection were studied. EMX2 protein expression was examined by immunohistochemistry, Western blot, or immunofluorescence. EMX2 expression levels in tissue specimens were scored and correlated with patient outcomes. Chemo-sensitivity of lung SCC cell lines stably transfected with EMX2 shRNAs to cisplatin, carboplatin, and docetaxel was examined in vitro.

Results

EMX2 expression was down-regulated in lung SCC tissue samples compared to their matched adjacent normal tissues. Positive EMX2 expression was significantly associated with improved overall survival in stage I lung SCC patients, and in stage II/IIIA lung SCC patients receiving adjuvant chemotherapy. EMX2 expression was also associated with expression of EMT markers in both lung SCC cell lines and tissue samples. Knock-down of EMX2 expression in lung SCC cells promoted chemo-resistance and cell migration.

Conclusions

EMX2 expression is down-regulated in lung SCC and its down-regulation is associated with chemo-resistance in lung SCC cells, possibly through regulation of Epithelial-to-Mesenchymal Transition (EMT). EMX2 may serve as a novel prognostic marker for stage I lung SCC patients and a prediction marker for stage II/IIIA lung SCC patients receiving adjuvant chemotherapy.

Depletion of poly(A)-specific ribonuclease (PARN) inhibits proliferation of human gastric cancer cells by blocking cell cycle progression

Regulation of mRNA decay plays a crucial role in the post-transcriptional control of cell growth, survival, differentiation, death and senescence. Deadenylation is a rate-limiting step in the silence and degradation of the bulk of highly regulated mRNAs. However, the physiological functions of various deadenylases have not been fully deciphered. In this research, we found that poly(A)-specific ribonuclease (PARN) was upregulated in gastric tumor tissues and gastric cancer cell lines MKN28 and AGS. The cellular function of PARN was investigated by stably knocking down the endogenous PARN in the MKN28 and AGS cells. Our results showed that PARN-depletion significantly inhibited the proliferation of the two types of gastric cancer cells and promoted cell death, but did not significantly affect cell motility and invasion. The depletion of PARN arrested the gastric cancer cells at the G0/G1 phase by upregulating the expression levels of p53 and p21 but not p27. The mRNA stability of p53 was unaffected by PARN-knockdown in both types of cells. A significant stabilizing effect of PARN-depletion on p21 mRNA was observed in the AGS cells but not in the MKN28 cells. We further showed that the p21 3'-UTR triggered the action of PARN in the AGS cells. The dissimilar observations between the MKN28 and AGS cells as well as various stress conditions suggested that the action of PARN strongly relied on protein expression profiles of the cells, which led to heterogeneity in the stability of PARN-targeted mRNAs.