Pleomorphic adenoma gene-like 2 regulates expression of the p53 family member, p73, and induces cell cycle block and apoptosis in human promonocytic U937 cells

The oncogenic function of PLAGL2 is mediated via ASCL2 and IGF2 and a Wnt-independent mechanism in colorectal cancer

Colorectal cancer (CRC) tumorigenesis and progression are linked to common oncogenic mutations, especially in the tumor suppressor APC, whose loss triggers the deregulation of TCF4/β-Catenin activity. CRC tumorigenesis is also driven by multiple epimutational modifiers such as transcriptional regulators. We describe the common (and near-universal) activation of the zinc finger transcription factor and Let-7 target PLAGL2 in CRC and find that it is a key driver of intestinal epithelial transformation. PLAGL2 drives proliferation, cell cycle progression, and anchorage-independent growth in CRC cell lines and nontransformed intestinal cells. Investigating effects of PLAGL2 on downstream pathways revealed very modest effects on canonical Wnt signaling. Alternatively, we find pronounced effects on the direct PLAGL2 target genes IGF2, a fetal growth factor, and ASCL2, an intestinal stem cell-specific bHLH transcription factor. Inactivation of PLAGL2 in CRC cell lines has pronounced effects on ASCL2 reporter activity. Furthermore, ASCL2 expression can partially rescue deficits of proliferation and cell cycle progression caused by depletion of PLAGL2 in CRC cell lines. Thus, the oncogenic effects of PLAGL2 appear to be mediated via core stem cell and onco-fetal pathways, with minimal effects on downstream Wnt signaling.NEW & NOTEWORTHY A Let-7 target called PLAGL2 drives oncogenic transformation via Wnt-independent pathways. This work illustrates the robust effects of this zinc finger transcription factor in colorectal cancer (CRC) cell lines and nontransformed intestinal epithelium, with effects mediated, in part, via the direct target genes ASCL2 and IGF2. This has implications for the role of PLAGL2 in activation of onco-fetal and onco-stem cell pathways, contributing to immature and highly proliferative phenotypes in CRC.

PLAGL2 induces nucleus pulposus cell apoptosis via regulating RASSF5 expression and thus accelerates intervertebral disc degeneration

Excessive apoptosis of nucleus pulposus (NP) cells is the main pathological change in intervertebral disc degeneration (IVDD) progression. Pleomorphic adenoma gene like-2 (PLAGL2) plays a key role in cell apoptosis, however, the effect of PLAGL2 on IVDD has not been clarified yet. In this study, we established mouse IVDD models via the annulus fibrosis needle puncture, TUNEL and safranin O staining were used to verify the successful establishment of IVDD models, and PLAGL2 expression was detected in disc tissues. Then, NP cells isolated from disc tissues were used to construct PLAGL2 knockdown cells. PLAGL2 expression in NP cells was analyzed with qRT-PCR and Western blot. The impact of PLAGL2 on the viability, apoptosis, and mitochondria function of NP cells was evaluated by MTT assay, TUNEL, JC1 staining, and flow cytometry assay. Additionally, the regulatory mechanism of PLAGL2 was further assessed. We found that PLAGL2 was upregulated in IVDD disc tissues and serum deprivation (SD)-stimulated NP cells. PLAGL2 knockdown inhibited apoptosis and mitochondria damage in NP cells. Moreover, knockdown of PLAGL2 downregulated the expression of downstream apoptosis-related factors RASSF5, Nip3, and p73. Mechanically, PLAGL2 transcriptionally activated RASSF5 via binding to its promoter. In general, our findings indicate that PLAGL2 induces apoptosis in NP cells and aggravates IVDD progression. This study provides a promising therapeutic target for IVDD treatment.

A Review of the Regulatory Mechanisms of N-Myc on Cell Cycle

Neuroblastoma has obvious heterogeneity. It is one of the few undifferentiated malignant tumors that can spontaneously degenerate into completely benign tumors. However, for its high-risk type, even with various intensive treatment options, the prognosis is still unsatisfactory. At the same time, a large number of research data show that the abnormal amplification and high-level expression of the MYCN gene are positively correlated with the malignant progression, poor prognosis, and mortality of neuroblastoma. In this context, this article explores the role of the N-Myc, MYCN gene expression product on its target genes related to the cell cycle and reveals its regulatory network in promoting tumor proliferation and malignant progression. We hope it can provide ideas and direction for the research and development of drugs targeting N-Myc and its downstream target genes.

High Expression of PLAGL2 is Associated With Poor Prognosis in High-Grade Glioma

Pleomorphic adenoma gene like-2 (PLAGL2) has been implicated in the development and progression of diverse malignancies, including glioblastoma. An increasing number of studies have reported that dysregulated expression of PLAGL2 is a common phenomenon in different malignancies. However, the mechanism and biological functions of PLAGL2 in patients with high-grade glioma (HGG) remain unclear. In addition, the expression and clinical significance of PLAGL2 in HGG have not yet been reported. Herein, we investigated the expression patterns and prognostic values of PLAGL2 in patients with HGG by using various databases, including Tumor Immune Estimation Resource 2.0 (TIMER2.0), GENT2, ONCOMINE, GEPIA, Human Protein Atlas, and Gene Expression Omnibus datasets. In the present study, we analyzed the relationship between PLAGL2 mRNA expression and clinical parameters in 184 HGG cases and found that PLAGL2 presented positively high expression and was relevant to poor prognosis. Immunohistochemistry analysis confirmed the overexpression of PLAGL2 protein, which is mainly expressed in the nucleus of glioma. Additionally, a high level of expression of the PLAGL2 gene was associated with lower survival in progression-free survival and overall survival in GBM patients. The correlation analysis between PLAGL2 and immune infiltration related to the abundance of B cells, CD8⁺ T cells, CD4⁺ T cells, macrophages, DCs, and neutrophils was also performed using TIMER2.0. GSEA results showed that high PLAGL2 expression was associated with cell migration, proliferation, actin cytoskeletal, and angiogenesis. To sum up, our findings indicated that PLAGL2 could serve as an independent prognostic biomarker and might be a potential therapeutic target for HGG, which should be further investigated.

The p53 family member p73 in the regulation of cell stress response

During oncogenesis, cells become unrestrictedly proliferative thereby altering the tissue homeostasis and resulting in subsequent hyperplasia. This process is paralleled by resumption of cell cycle, aberrant DNA repair and blunting the apoptotic program in response to DNA damage. In most human cancers these processes are associated with malfunctioning of tumor suppressor p53. Intriguingly, in some cases two other members of the p53 family of proteins, transcription factors p63 and p73, can compensate for loss of p53. Although both p63 and p73 can bind the same DNA sequences as p53 and their transcriptionally active isoforms are able to regulate the expression of p53-dependent genes, the strongest overlap with p53 functions was detected for p73. Surprisingly, unlike p53, the p73 is rarely lost or mutated in cancers. On the contrary, its inactive isoforms are often overexpressed in cancer. In this review, we discuss several lines of evidence that cancer cells develop various mechanisms to repress p73-mediated cell death. Moreover, p73 isoforms may promote cancer growth by enhancing an anti-oxidative response, the Warburg effect and by repressing senescence. Thus, we speculate that the role of p73 in tumorigenesis can be ambivalent and hence, requires new therapeutic strategies that would specifically repress the oncogenic functions of p73, while keeping its tumor suppressive properties intact.

PLAGL2-EGFR-HIF-1/2α Signaling Loop Promotes HCC Progression and Erlotinib Insensitivity

BACKGROUND AND AIMS

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide, hence a major public health threat. Pleomorphic adenoma gene like-2 (PLAGL2) has been reported to play a role in tumorigenesis. However, its precise function in HCC remains poorly understood.

APPROACH AND RESULTS

In this study, we demonstrated that PLAGL2 was up-regulated in HCC compared with that of adjacent nontumorous tissues and also correlated with overall survival times. We further showed that PLAGL2 promoted HCC cell proliferation, migration, and invasion both in vitro and in vivo. PLAGL2 expression was positively correlated with epidermal growth factor receptor (EGFR) expression. Mechanistically, this study demonstrated that PLAGL2 functions as a transcriptional regulator of EGFR and promotes HCC cell proliferation, migration, and invasion through the EGFR-AKT pathway. Moreover, hypoxia was found to significantly induce high expression of PLAGL2, which promoted hypoxia inducible factor 1/2 alpha subunit (HIF1/2A) expression through EGFR. Therefore, this study demonstrated that a PLAGL2-EGFR-HIF1/2A signaling loop promotes HCC progression. More importantly, PLAGL2 expression reduced hepatoma cells' response to the anti-EGFR drug erlotinib. PLAGL2 knockdown enhanced the response to erlotinib.

CONCLUSIONS

This study reveals the pivotal role of PLAGL2 in HCC cell proliferation, metastasis, and erlotinib insensitivity. This suggests that PLAGL2 can be a potential therapeutic target of HCC.

Nuclear Tau, p53 and Pin1 Regulate PARN-Mediated Deadenylation and Gene Expression

While nuclear tau plays a role in DNA damage response (DDR) and chromosome relaxation, the mechanisms behind these functions are not fully understood. Here, we show that tau forms complex(es) with factors involved in nuclear mRNA processing such as tumor suppressor p53 and poly(A)-specific ribonuclease (PARN) deadenylase. Tau induces PARN activity in different cellular models during DDR, and this activation is further increased by p53 and inhibited by tau phosphorylation at residues implicated in neurological disorders. Tau's binding factor Pin1, a mitotic regulator overexpressed in cancer and depleted in Alzheimer's disease (AD), also plays a role in the activation of nuclear deadenylation. Tau, Pin1 and PARN target the expression of mRNAs deregulated in AD and/or cancer. Our findings identify novel biological roles of tau and toxic effects of hyperphosphorylated-tau. We propose a model in which factors involved in cancer and AD regulate gene expression by interactions with the mRNA processing machinery, affecting the transcriptome and suggesting insights into alternative mechanisms for the initiation and/or developments of these diseases.

miRNA and mRNA Integration Network Construction Reveals Novel Key Regulators in Left-Sided and Right-Sided Colon Adenocarcinoma

Background

The distinction between right-sided and left-sided colon adenocarcinoma has recently received considerable. This study aims to identify key MicroRNA (miRNA) and mRNAs in right-sided colon adenocarcinoma (RSCOAD) and left-sided colon adenocarcinoma (LSCOAD) by TCGA integration analysis.

Methods

The miRNA and mRNA expression profiles of a large group of patients with RSCOAD and LSCOAD were obtained from TCGA. The differentially expressed miRNAs (DEmiRNAs) and mRNAs (DEmRNAs) were identified by TCGA integration analysis. The optimal diagnostic miRNA biomarkers for RSCOAD and LSCOAD were identified by Boruta algorithm. We established classification models to distinguish RSCOAD and LSCOAD. Protein-protein interaction (PPI) network analysis, DEmiRNA-DEmRNA interaction analysis, and functional annotation were performed. The expression of selected DEmiRNAs and DEmRNAs was validated by qRT-PCR.

Results

A total of 2534 DEmRNAs (940 downregulated and 1594 upregulated mRNAs) and 54 DEmiRNAs (22 downregulated and 32 upregulated miRNAs) between RSCOAD and LSCOAD were identified. The feature selection procedure was to obtain 22 optimal diagnostic miRNAs biomarkers in RSCOAD compared to LSCOAD. The AUC of the random forests model was 0.869 and the specificity and sensitivity of this model were 79% and 84.6%, respectively. Three DEmiRNAs (hsa-miR-224-5p, hsa-miR-155-5p, and hsa-miR-31-5p) and five DEmRNAs (CXCR4, SMAD4, KRAS, FITM2, and PLAGL2) were identified key DEmiRNAs and DEmRNAs in RSCOAD compared to LSCOAD. The qRT-PCR results of CXCR4, FITM2, TFAP2A, ULBP2, hsa-miR-224-5p, and hsa-miR-155-5p were consistent with our integrated analysis.

Conclusion

A total of three DEmiRNAs (hsa-miR-224-5p, hsa-miR-155-5p, and hsa-miR-31-5p) and five DEmRNAs (CXCR4, SMAD4, KRAS, FITM2, and PLAGL2) may be involved in the pathogenesis of RSCOAD and LSCOAD which may make a contribution for understanding mechanisms and developing therapeutic strategies for RSCOAD and LSCOAD.

Increased miR-214 expression suppresses cell migration and proliferation in Hirschsprung disease by interacting with PLAGL2

BACKGROUND

The miR-214 has been reported to be associated with various diseases, but its involvement in the pathophysiology of Hirschsprung disease (HSCR) is almost completely unexplored.

METHODS

In our study, we conducted a series of experiments to unravel the biological role of miR-214 in the pathophysiology of HSCR. qRT-PCR and western blotting were utilized to investigate the relative expression levels of miR-214, mRNAs, and proteins of related genes in colon tissues from 20 controls without HSCR and 24 patients with HSCR. The potential biological role of miR-214 in two cell lines (SKN-SH and SH-SY5Y) was assessed using the CCK8 assay, EdU staining, transwell assay, and flow cytometry. The dual-luciferase reporter assay was used to confirm PLAGL2 as a common target gene of miR-214.

RESULTS

All results suggested that miR-214 is upregulated in HSCR tissue samples compared with controls. Additionally, we found that miR-214 could inhibit cell proliferation and migration by directly downregulating the expression of PLAGL2, and the extent of the miR-214-mediated inhibitory effects could be rescued by a PLAGL2 overexpression plasmid.

CONCLUSION

Our results revealed that miR-214 is indeed involved in the pathophysiology of HSCR and suppresses cell proliferation and migration by directly downregulating PLAGL2 in cell models.

DJ-1 promotes colorectal cancer progression through activating PLAGL2/Wnt/BMP4 axis

Metastasis remains a big barrier for the clinical treatment of colorectal cancer (CRC). Our previous proteomics analysis identified DJ-1 as a potential metastasis biomarker of CRC. In this study, we found that DJ-1 was upregulated in CRC. The levels of DJ-1 were closely correlated with the depths of invasion and predicted patient outcome. Enforced expression of DJ-1 could enhance CRC proliferation and metastasis in vitro and in vivo by stimulating Wnt-β-catenin signaling. Specifically, DJ-1-induced β-catenin nuclear translocation stimulated TCF transcription activity, which promoted BMP4 expression for CRC cell migration and invasion, and elevated CCND1 expression for CRC cell proliferation, respectively. Furthermore, DJ-1-induced Wnt signaling activation was dependent on PLAGL2 expression. In conclusion, our study demonstrates that DJ-1 can promote CRC metastasis by activating PLAGL2-Wnt-BMP4 axis, suggesting novel therapeutic opportunities for postoperative adjuvant therapy in CRC patients.

Studying the mechanism of PLAGL2 overexpression and its carcinogenic characteristics based on 3'-untranslated region in colorectal cancer

Pleomorphic adenoma gene like-2 (PLAGL2) is a zinc finger protein transcription factor, which is upregulated and serves an oncogenic function in multiple human malignancies, including colorectal cancer (CRC). First, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression levels of PLAGL2 in CRC tissues and normal tissues. Then, bioinformatics analysis, RT-qPCR, western blotting, luciferase reporter assays and RNA-binding protein immunoprecipitation assays were performed to explore whether the underlying mechanisms, including copy number variation (CNV), microRNAs (miRNAs/miRs) and RNA-binding proteins (RBPs) led to the abnormal expression of PLAGL2. Finally, cell counting kit-8 assays, Transwell assays and xenograft models were used to detect carcinogenesis-associated characteristics based on the 3′-untranslated region (3′-UTR) of PLAGL2. In the present study, PLAGL2 was revealed to be upregulated in CRC tissues compared with normal CRC tissues. CNV was one of the causes leading to the upregulation of PLAGL2. miRNA, including downregulated miR-486-5p, and RBPs, including upregulated human antigen R (HuR), were other key underlying causes. In addition, PLAGL2 3′-UTR was revealed to promote the progression of CRC in vitro and in vivo, and to regulate the expression of C-MYC and CD44. To conclude, these results suggested that high expression of PLAGL2 in CRC was associated with CNV, miR-486-5p and HuR expression, whose 3′-UTR may promote colon carcinogenesis and serve as a novel potential biomarker for CRC therapies.

Overexpression of Pleomorphic Adenoma Gene-Like 2 Is a Novel Poor Prognostic Marker of Prostate Cancer

Pleomorphic adenoma gene like-2 (PLAGL2) is a member of the PLAG gene family. Previous studies have revealed that overexpression of PLAGL2 is associated with many human cancers. However, it has been reported that PLAGL2 also plays as a tumor suppressor. The precise role of PLAGL2 in prostate cancer (PCa) is still unknown. The aim of this study was to investigate the expression and prognostic value of PLAGL2 in PCa. Data from microarray datasets demonstrated that the DNA copy number and mRNA level of PLAGL2 were significantly increased in PCa compared with normal prostate. qRT-PCR and western blot analysis from paired PCa samples and prostate cell lines confirmed upregulated mRNA and protein expression levels in PCa. Immunohistochemistry analysis showed that staining of PLAGL2 in PCa tissues was significantly higher than that in benign prostatic hyperplasia (BPH) tissues. In addition, the high expression of PLAGL2 was only involved in preoperative PSA, but was not related to age, Gleason score, seminal vesicle invasion, surgical margin status, clinical stage and positive lymph node metastasis. Moreover, our results showed that PLAGL2 was an independent prognostic factor for biochemical recurrence (BCR)-free survival and overall survival (OS) of PCa patients, and overexpressed PLAGL2 was related to early development of BCR and poor OS. In conclusion, our findings suggest that PLAGL2 is overexpressed in PCa. The increased expression of PLAGL2 correlates to PCa progression following radical prostatectomy and may serve as a novel poor prognostic marker for PCa.

Identification of upstream regulators for prognostic expression signature genes in colorectal cancer

Background

Gene expression signatures have been commonly used as diagnostic and prognostic markers for cancer subtyping. However, expression signatures frequently include many passengers, which are not directly related to cancer progression. Their upstream regulators such as transcription factors (TFs) may take a more critical role as drivers or master regulators to provide better clues on the underlying regulatory mechanisms and therapeutic applications.

Results

In order to identify prognostic master regulators, we took the known 85 prognostic signature genes for colorectal cancer and inferred their upstream TFs. To this end, a global transcriptional regulatory network was constructed with total >200,000 TF-target links using the ARACNE algorithm. We selected the top 10 TFs as candidate master regulators to show the highest coverage of the signature genes among the total 846 TF-target sub-networks or regulons. The selected TFs showed a comparable or slightly better prognostic performance than the original 85 signature genes in spite of greatly reduced number of marker genes from 85 to 10. Notably, these TFs were selected solely from inferred regulatory links using gene expression profiles and included many TFs regulating tumorigenic processes such as proliferation, metastasis, and differentiation.

Conclusions

Our network approach leads to the identification of the upstream transcription factors for prognostic signature genes to provide leads to their regulatory mechanisms. We demonstrate that our approach could identify upstream biomarkers for a given set of signature genes with markedly smaller size and comparable performances. The utility of our method may be expandable to other types of signatures such as diagnosis and drug response.