Inhibiting the m6A Reader IGF2BP3 Suppresses Ovarian Cancer Cell Growth via Regulating PLAGL2 mRNA Stabilization

Background

The oncogene IGF2 mRNA binding protein 3 (IGF2BP3) could function as an m6A reader in stabilizing many tumor-associated genes' mRNAs. However, the relevant oncogenic mechanism by which IGF2BP3 promotes ovarian cancer growth is largely unknown.

Methods

The IGF2BP3 expression in ovarian cancer was identified by retrieving the datasets from The Cancer Genome Atlas (TCGA). GEO datasets evaluated the relevant signaling pathways in IGF2BP3 knockdown in ovarian cancer cells. IGF2BP3 positive correlation gene in TCGA was calculated. MTS proliferation assay was identified in IGF2BP3 knockdown and rescued by PLAG1 like zinc finger 2 (PLAGL2) overexpression in ES-2 and SKOV3 cells. Bioinformatic analysis and RIP-qPCR were predicted and identified the IGF2BP3 binding site and PLAGL2 mRNA stability. The animal experiment identified IGF2BP3 proliferation inhibition.

Results

IGF2BP3 was upregulated in ovarian cancer tissue and cells. The depletion of IGF2BP3 in ovarian cancer cells leads to an enhancement of the pathway involved in cellular proliferation and mRNA stability. IGF2BP3 positive correlation suppressed pro-proliferation gene PLAGL2. IGF2BP3 knockdown suppressed ovarian cancer cell proliferation and was rescued by PLAGL2 overexpression. Luciferase reporter assay confirmed that IGF2BP3 could bind to 3'-UTR of PLAGL2 to maintain the mRNA stability. Further, in in vivo experiments, IGF2BP3 knockdown suppressed ovarian cancer cell proliferation via inhibiting PLAGL2 expression.

Conclusion

All of these indicate that PLAGL2 mediates the main function of IGF2BP3 knockdown on ovarian cancer proliferation inhibition through mRNA stability regulation.

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.

TEAD4 predicts poor prognosis and transcriptionally targets PLAGL2 in serous ovarian cancer

The oncogenic function of TEA domain transcription factor 4 (TEAD4) has been confirmed in multiple human malignancies, while its potential role and regulatory mechanism in serous ovarian cancer progression are left unknown. By the gene expression analyses from Gene Expression Profiling Interactive Analysis (GEPIA) database, TEAD4 expression is shown to be up-regulated in serous ovarian cancer samples. Here, we confirmed the high expression of TEAD4 in clinical serous ovarian cancer specimens. In the following functional experiments, we found that TEAD4 overexpression promoted serous ovarian cancer malignant phenotypes, including proliferation, migration and invasion in serous ovarian cancer SK-OV-3 and OVCAR-3 cells, while TEAD4 knockout exerted the opposite function. The tumor growth inhibition of TEAD4 depletion was also affirmed by a Xenograft model in mice. In addition, this phenotypic deterioration induced by TEAD4 overexpression was diminished by PLAG1 like zinc finger 2 (PLAGL2) silencing. More importantly, combined with the results of the dual-luciferase assay, the transcriptional regulation of TEAD4 on PLAGL2 promoter was evidenced. Our results showed that the cancer-promoting gene TEAD4 was involved in serous ovarian cancer progression via targeting PLAGL2 at the transcriptional level.

PLAGL2 promotes the stemness and is upregulated by transcription factor E2F1 in human lung cancer

This study mainly focuses on revealing the role of PLAGL2 in lung cancer stemness. In vitro and in vivo experiments were performed to evaluate the effects of PLAGL2 on lung cancer cell stemness. Mechanistic analysis using luciferase reporter and ChIP assays were implemented to reveal the underlying mechanisms. The transcriptional factor E2F1 transcriptionally activated PLAGL2 expression via directly binding to PLAGL2 promoter in lung cancer cells. Moreover, PLAGL2 promoted the stemness of lung cancer cells dependent on E2F1-mediated transcriptional activation. This study provides a potential target for lung cancer progression.

Long non-coding RNA LGALS8-AS1 facilitates PLAGL2-mediated malignant phenotypes in gastric cancer

BACKGROUND

Great progress has been made in studying the function of long non-coding RNA (lncRNA) in various tumors, including gastric cancer (GC). However, there are still numerous lncRNAs that have not yet been studied and explored for their roles in GC, and their important functions need to be further revealed.

METHODS

Through analyzing The Cancer Genome Atlas (TCGA) database combined with bioinformatics survival tools, a novel GC-related lncRNA LGALS8-AS1 was identified. A quantitative real-time polymerase chain reaction and a series of in vitro or in vivo cell functional experiments were performed to determine the expression and the role of LGALS8-AS1/miR-138-5p/PLAGL2 in GC.

RESULTS

LGALS8-AS1 was remarkably upregulated and correlated with the unfavorable prognosis in GC. Higher expression of LGALS8-AS1 was positively associated with higher lymph node metastasis rate, as well as larger tumor size. In addition, a series of cell functional experiments revealed that LGALS8-AS1 could facilitate GC cell proliferation, migration and metastasis in vitro or in vivo. A deeper mechanism exploration revealed that LGALS8-AS1 could function as the miR-138-5p molecular sponge and upregulate the PLAGL2 expression, thereby promoting the cell proliferation, migration and metastasis in GC.

CONCLUSIONS

In brief, we revealed the tumor promoting role of the LGALS8-AS1/miR-138-5p/PLAGL2 molecular signaling axis in GC, and our findings provide enlightenment for further understanding of the mechanism of tumorigenesis and development of GC, making LGALS8-AS1 a possible new diagnostic or therapeutic target for GC.

PLAGL2 increases adriamycin resistance and EMT in breast cancer cells by activating the Wnt pathway

BACKGROUND

Adriamycin (ADR) is an effective treatment for breast cancer; nevertheless, it is often linked with acquired resistance in breast cancer cells, reducing ADR's therapeutic efficacy and increasing the risk of recurrence and poor prognosis. It has been revealed that the zinc-finger transcription factor pleomorphic adenoma gene like-2 (PLAGL2) is required for epithelial to mesenchymal transition (EMT) in cancer cells. Recent data indicates that PLAGL2 is also involved in regulating chemotherapeutic drug resistance, albeit the exact mechanism by which this happens remains unknown.

OBJECTIVE

This study examines the effect of PLAGL2 on adriamycin resistance and EMT in breast cancer cells.

METHODS

The small interfering RNA (siRNA) targeting PLAGL2 was transfected to breast cancer cells to alter PLAGL2 expression. Cell counting kit-8 (CCK-8) and colony formation assay detected cell growth and proliferation rate. Moreover, wound-healing and transwell assays were conducted to evaluate migration and invasion. Western blot (WB) checked the apoptosis and EMT-associated proteins.

RESULTS

PLAGL2 expression is associated with breast cancer cells' acquired resistance to ADR in this investigation. Additionally, deletion of PLAGL2 was associated with enhanced sensitivity to ADR, reduced proliferation, migration, and invasion capabilities, increased E-cadherin levels, and reduced Wnt6, β-catenin, and DVL1 levels in ADR-resistant breast cancer cells (MCF-7/ADR and MDA-MB-231/ADR cells). PLAGL2 could bind to the promoter region of Wnt6 and promote its expression. Additionally, the results of this research established that Wnt signaling is implicated in breast cancer cells' resistance to ADR since BML-284, a Wnt signaling activator partly restored the sensitivity of MCF-7/ADR and MDA-MB-231/ADR cells to ADR.

CONCLUSION

PLAGL2 promotes adriamycin resistance and cell aggressiveness in breast cancer cells via activating the Wnt signaling pathway.

Amplification of the PLAG-family genes-PLAGL1 and PLAGL2-is a key feature of the novel tumor type CNS embryonal tumor with PLAGL amplification

Pediatric central nervous system (CNS) tumors represent the most common cause of cancer-related death in children aged 0-14 years. They differ from their adult counterparts, showing extensive clinical and molecular heterogeneity as well as a challenging histopathological spectrum that often impairs accurate diagnosis. Here, we use DNA methylation-based CNS tumor classification in combination with copy number, RNA-seq, and ChIP-seq analysis to characterize a newly identified CNS tumor type. In addition, we report histology, patient characteristics, and survival data in this tumor type. We describe a biologically distinct pediatric CNS tumor type (n = 31 cases) that is characterized by focal high-level amplification and resultant overexpression of either PLAGL1 or PLAGL2, and an absence of recurrent genetic alterations characteristic of other pediatric CNS tumor types. Both genes act as transcription factors for a regulatory subset of imprinted genes (IGs), components of the Wnt/β-Catenin pathway, and the potential drug targets RET and CYP2W1, which are also specifically overexpressed in this tumor type. A derived PLAGL-specific gene expression signature indicates dysregulation of imprinting control and differentiation/development. These tumors occurred throughout the neuroaxis including the cerebral hemispheres, cerebellum, and brainstem, and were predominantly composed of primitive embryonal-like cells lacking robust expression of markers of glial or neuronal differentiation (e.g., GFAP, OLIG2, and synaptophysin). Tumors with PLAGL1 amplification were typically diagnosed during adolescence (median age 10.5 years), whereas those with PLAGL2 amplification were diagnosed during early childhood (median age 2 years). The 10-year overall survival was 66% for PLAGL1-amplified tumors, 25% for PLAGL2-amplified tumors, 18% for male patients, and 82% for female patients. In summary, we describe a new type of biologically distinct CNS tumor characterized by PLAGL1/2 amplification that occurs predominantly in infants and toddlers (PLAGL2) or adolescents (PLAGL1) which we consider best classified as a CNS embryonal tumor and which is associated with intermediate survival. The cell of origin and optimal treatment strategies remain to be defined.

LncRNA HCP5 acts as a miR-128-3p sponge to promote the progression of multiple myeloma through activating Wnt/β-catenin/cyclin D1 signaling via PLAGL2

BACKGROUND

Although long non-coding RNA (lncRNA) HCP plays essential roles in human cancers, its function and mechanism in multiple myeloma (MM) have not crystallized.

METHODS

HCP5 level in MM was assessed through qRT-PCR. A series of functional investigations were conducted to evaluate the influences of HCP5 on proliferation and apoptosis. Bioinformatics analysis and RIP/RNA pull-down assays were carried out to determine the relationships among HCP5, miR-128-3p, and PLAGL2. Relative protein level was determined through Western blot. A xenograft tumor model was applied for validating the roles of HCP5/miR-128-3p/PLAGL2 axis in vivo.

RESULTS

HCP5 was significantly increased in MM. HCP5 knockdown effectively thwarted the proliferative rate and cell cycle of MM cell lines and suppressed tumor growth. HCP5 regulated PLAGL2 expression by sponging miR-128-3p. PLAGL2 overexpression effectively rescued cells from influences by sh-HCP5 on cell proliferative and apoptotic rates. Additionally, HCP5 knockdown significantly inhibited Wnt/β-catenin/cyclin D1 signaling, and these effects were eliminated by PLAGL2 overexpression.

CONCLUSION

Our study revealed that HCP5/miR-128-3p/PLAGL2 is closely correlated to MM development by modulating Wnt/β-catenin/cyclin D1 signaling. HCP5 promoted cell proliferation and tumor formation of MM cells by activating the Wnt/β-catenin/CCND1 signaling pathway by sponging miR-128-3p to increase PLAGL2 expression.

PLAGL2 Promotes the Proliferation and Migration of Diffuse Large B-cell Lymphoma Cells via Wnt/β-catenin Pathway

OBJECTIVE

Pleomorphic adenoma gene like-2 (PLAGL2) belongs to PLAG protein family and functions as a zinc finger transcriptional factor to participate in the cellular processes, including cell transformation, migration, and apoptosis. Increasing evidence has shown the oncogenic role of PLAGL2 in various cancers, while the potential molecular mechanism and biology roles of PLAGL2 in diffuse large B-cell lymphoma (DLBCL) are still unclear.

METHODS

Expression of PLAGL2 was found to be elevated in DLBCL cells. Functional assays showed that silence of PLAGL2 suppressed cell proliferation and reduced the cell migration and invasion in DLBCL. The cell proliferation and metastasis in DLBCL were promoted by over-expression of PLAGL2. Moreover, the protein expression of E-cadherin was increased, while the protein expressions of N-cadherin and vimentin were decreased in DLBCL cells by knockdown of PLAGL2. However, over-expression of PLAGL2 promoted epithelial to mesenchymal transition (EMT) of DLBCL through down-regulation of E-cadherin, and up-regulations of N-cadherin and vimentin.

RESULTS

Over-expression of PLAGL2 up-regulated β-catenin and c-myc, while down-regulated axis inhibition protein 2 (AXIN2) and adenomatous polyposis coli (APC) in DLBCL. Knockdown of PLAGL2 suppressed the activation of Wnt/β-catenin pathway in DLBCL through downregulating β-catenin and c-myc but upregulating AXIN2 and APC. Xenograft model also demonstrated that interference of PLAGL2 repressed the in vivo tumor growth of DLBCL.

CONCLUSION

In conclusion, PLAGL2 promoted the malignancy of DLBCL through activation of Wnt/β-catenin pathway.

Selenium sulfide disrupts the PLAGL2/C-MET/STAT3-induced resistance against mitochondrial apoptosis in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide. Overexpression of pleomorphic adenoma gene like-2 (PLAGL2) is associated with tumorigenesis. However, its function in HCC is unclear, and there are currently no anti-HCC drugs that target PLAGL2. Drug repositioning may facilitate the development of PLAGL2-targeted drug candidates.

METHODS

The expression of PLAGL2 in HCC clinical tissue samples and HCC cell lines was analyzed by western blotting. The constructed HCC cell models were used to confirm the underlying function of PLAGL2 as a therapeutic target. Multiple in vitro and in vivo assays were conducted to determine the anti-proliferative and apoptosis-inducing effects of selenium sulfide (SeS2 ), which is clinically used for the treatment of seborrheic dermatitis and tinea versicolor.

RESULTS

PLAGL2 expression was higher in HCC tumor tissues than in normal adjacent tissues. Its overexpression promoted the resistance of HCC cells of mitochondrial apoptosis through the regulation of the downstream C-MET/STAT3 signaling axis. SeS2 exerted significant anti-proliferative and apoptosis-inducing effects on HCC cells in a PLAGL2-dependent manner. Mechanistically, SeS2 suppressed C-MET/STAT3, AKT/mTOR, and MAPK signaling and triggered Bcl-2/Cyto C/Caspase-mediated intrinsic mitochondrial apoptosis both in vitro and in vivo.

CONCLUSIONS

Our data reveal an important role of PLAGL2 in apoptosis resistance in HCC and highlight the potential of using SeS2 as a PLAGL2 inhibitor in patients with HCC.

Long noncoding RNA ILF3-AS1 aggravates papillary thyroid carcinoma progression via regulating the miR-4306/PLAGL2 axis

BACKGROUND

It have been proven that long non-coding RNAs (lncRNAs) serve as regulators in carcinogenesis. Interleukin enhancer binding factor 3 antisense RNA 1 (ILF3-AS1) has been illuminated as a prognostic factor in some cancers. Nevertheless, its expression pattern and possible functions in papillary thyroid carcinoma (PTC) have not been studied.

METHODS

The expression of ILF3-AS1 was measured by RT-qPCR and ISH. Colony formation assay and EdU assay were used to probe cell proliferation. TUNEL assay was used for analysis of cell apoptosis. Immunofluorescence and western blot were conducted to evaluate the expression change of E-cadherin and N-cadherin. The RNA interaction was demonstrated by mechanism experiments, including pull down assay and dual luciferase reporter assay.

RESULTS

ILF3-AS1 expression was evidently upregulated in PTC cell lines. ILF3-AS1 knockdown restrained the proliferation, migration and invasion of PTC cells. Mechanical investigation revealed that miR-4306 could interact with ILF3-AS1. PLAGL2 was a downstream target of miR-4306. The effects of ILF3-AS1 knockdown on the cellular processes were abrogated by miR-4306 downregulation or pleiomorphic adenoma gene-like 2 (PLAGL2) overexpression.

CONCLUSION

ILF3-AS1 plays tumor-promoting role in PTC via targeting miR-4306/PLAGL2 axis.

Hsa-circRNA-103809 Promotes Hepatocellular Carcinoma Development via MicroRNA-1270/PLAG1 Like Zinc Finger 2 Axis

BACKGROUND

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death in the worldwide. A great number of reports manifested that circular RNA hsa-circRNA-103809 (circRNA-103809) could work in several cancers.

AIMS

This study aimed to explore the function and mechanism of circRNA-103809 in HCC.

METHODS

Gene expressions were detected by quantitative real-time polymerase chain reaction. Colony formation, cell counting kit-8, transwell and wound healing assays were implemented to check the role of circRNA-103809 in HCC. Subcellular fractionation analysis was designed to figure out the cellular location of circRNA-103809. Luciferase reporter assay and RNA pull down assay were employed to verify the relationships among RNAs.

RESULTS

CircRNA-103809 was highly expressed in HCC cell lines. After interfering circRNA-103809, the proliferation, migration, invasion and epithelial-to-mesenchymal transition process were all hindered in HCC cells. Significantly, circRNA-103809 competed with PLAG1 like zinc finger 2 (PLAGL2) for binding with microRNA-1270 (miR-1270), which formulated a competing endogenous RNA network in HCC. Thereafter, we verified the tumor-facilitating effect of circRNA-103809/miR-1270/PLAGL2 axis on biological behaviors of HCC cells.

CONCLUSION

Hsa-circRNA-103809 promoted development of HCC via sequestering miR-1270 and up-regulating PLAGL2.

LncRNA ARAP1-AS1 aggravates the malignant phenotypes of ovarian cancer cells through sponging miR-4735-3p to enhance PLAGL2 expression

Ovarian cancer is one of the leading lethal gynecological cancers, causing serious harm to the health of female populations. Growing studies emphasize that lncRNAs serve as significant regulators in the tumorigenesis and evolution of numerous malignancies, including ovarian cancer. Recently, the oncogenic activity of lncRNA ARAP1-AS1 has been justified in a variety of cancers. However, the potential function of ARAP1-AS1 in ovarian cancer development is still unclear. Herein, we firstly revealed the expression profile of ARAP1-AS1 in ovarian cancer. Compared to normal samples and cells, upregulation of ARAP1-AS1 was observed in tissues and cells of ovarian cancer. Therewith, it was disclosed that knockdown of ARAP1-AS1 alleviated the carcinogenicity of ovarian cancer cells. Besides, our findings delineated that ARAP1-AS1 silence inhibited the expression of oncogene PLAGL2. Considering that ARAP1-AS1 was principally expressed in the the cytoplasm of ovarian cancer cells, we speculated that ARAP1-AS1 facilitated ovarian cancer progression via functioning as a ceRNA. Further investigations indicated that ARAP1-AS1 promoted PLAGL2 expression by competitively binding with miR-4735-3p. Of note, ARAP1-AS1 contributed to the malignant phenotypes of ovarian cancer cells through modulation of miR-4735-3p/PLAGL2 axis, revealing ARAP1-AS1 as a promising therapeutic target for ovarian cancer patients.

Long non-coding RNA MAPKAPK5-AS1/PLAGL2/HIF-1α signaling loop promotes hepatocellular carcinoma progression

Background

Long non-coding RNAs (lncRNAs) are widely involved in human cancers’ progression by regulating tumor cells’ various malignant behaviors. MAPKAPK5-AS1 has been recognized as an oncogene in colorectal cancer. However, the biological role of MAPKAPK5-AS1 in hepatocellular carcinoma (HCC) has not been explored.

Methods

Quantitative real-time PCR was performed to detect the level of MAPKAPK5-AS1 in HCC tissues and cell lines. The effects of MAPKAPK5-AS1 on tumor growth and metastasis were assessed via in vitro experiments, including MTT, colony formation, EdU, flow cytometry, transwell assays, and nude mice models. The western blotting analysis was carried out to determine epithelial-mesenchymal transition (EMT) markers and AKT signaling. The interaction between MAPKAPK5-AS1, miR-154-5p, and PLAGL2 were explored by luciferase reporter assay and RNA immunoprecipitation. The regulatory effect of HIF-1α on MAPKAPK5-AS1 was evaluated by chromatin immunoprecipitation.

Results

MAPKAPK5-AS1 expression was significantly elevated in HCC, and its overexpression associated with malignant clinical features and reduced survival. Functionally, MAPKAPK5-AS1 knockdown repressed the proliferation, mobility, and EMT of HCC cells and induced apoptosis. Ectopic expression of MAPKAPK5-AS1 contributed to HCC cell proliferation and invasion in vitro. Furthermore, MAPKAPK5-AS1 silencing suppressed, while MAPKAPK5-AS1 overexpression enhanced HCC growth and lung metastasis in vivo. Mechanistically, MAPKAPK5-AS1 upregulated PLAG1 like zinc finger 2 (PLAGL2) expression by acting as an endogenous competing RNA (ceRNA) to sponge miR-154-5p, thereby activating EGFR/AKT signaling. Importantly, rescue experiments demonstrated that the miR-154-5p/PLAGL2 axis mediated the function of MAPKAPK5-AS1 in HCC cells. Interestingly, we found that hypoxia-inducible factor 1α (HIF-1α), a transcript factor, could directly bind to the promoter to activate MAPKAPK5-AS1 transcription. MAPKAPK5-AS1 regulated HIF-1α expression through PLAGL2 to form a hypoxia-mediated MAPKAPK5-AS1/PLAGL2/HIF-1α signaling loop in HCC.

Conclusions

Our results reveal a MAPKAPK5-AS1/PLAGL2/HIF-1α signaling loop in HCC progression and suggest that MAPKAPK5-AS1 could be a potential novel therapeutic target of HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01868-z.

PLAGL2 promotes the proliferation and migration of gastric cancer cells via USP37-mediated deubiquitination of Snail1

Rationale: PLAGL2 (pleomorphic adenoma gene like-2), a zinc finger PLAG transcription factor, is aberrantly expressed in several malignant tumors. However, the biological roles of PLAGL2 and its underlying mechanism in gastric cancer (GC) remain unclear.

Methods: A series of experiments in vitro and in vivo were conducted to reveal the role of PLAGL2 in GC progression.

Results: The data revealed that PLAGL2 promotes GC cell proliferation, migration, invasion, and EMT in vitro and in vivo. Mechanistically, we demonstrated the critical role of PLAGL2 in the stabilization of snail family transcriptional repressor 1 (Snail1) and promoting Snail1-mediated proliferation and migration of GC cells. PLAGL2 activated the transcription of deubiquitinase USP37, which then interacted with and deubiquitinated Snail1 protein directly. In addition, GSK-3β-dependent phosphorylation of Snail1 protein is essential for USP37-mediated Snail1 deubiquitination regulation.

Conclusions: In general, PLAGL2 promotes the proliferation and migration of GC cells through USP37-mediated deubiquitination of Snail1 protein. This work provided potential therapeutic targets for GC treatment.

MicroRNA-214-3p targets the PLAGL2-MYH9 axis to suppress tumor proliferation and metastasis in human colorectal cancer

Evidence has shown that microRNAs (miRNAs) participate in the progression of CRC. Previous studies have indicated that miR-214-3p is abnormally expressed in various malignant tumors. However, the biological function it plays in CRC and the potential mechanism are unclear. Here, we demonstrated that miR-214-3p was obviously downregulated in CRC. Moreover, we found a strong correlation between the miR-214-3p level and tumor size and lymphatic metastasis. Furthermore, when miR-214-3p was decreased by an Lv-miR-214-3p inhibitor, the proliferation and migration of SW480 and HCT116 cells were significantly increased. As expected, the ability of proliferation and migration was significantly suppressed when miR-214-3p was overexpressed in DLD1 cells. According to the dual-luciferase reporter results, PLAGL2 was found to be a direct downstream molecule of miR-214-3p. Chromatin immunoprecipitation (CHIP) confirmed that MYH9, a well-known cytoskeleton molecule in CRC, was a direct targeting gene of PLAGL2. Silencing PLAGL2 or MYH9 could reverse the effect of a miR-214-3p inhibitor on CRC cells. In summary, our studies proved that low expression of miR-214-3p and overexpression of downstream PLAGL2 in CRC indicated a poor prognosis. MiR-214-3p suppressed the malignant behaviors of colorectal cancer by regulating the PLAGL2/MYH9 axis. MiR-214-3p might be a novel therapeutic target or prognostic marker for CRC.

The PLAGL2/MYCN/miR-506-3p interplay regulates neuroblastoma cell fate and associates with neuroblastoma progression

Background

The oncogene MYCN is critical for tumorigenesis of several types of cancers including neuroblastoma. We previously reported that miR-506-3p repressed MYCN expression in neuroblastoma cells. However, the mechanism underlying such regulation was undetermined since there is no miR-506-3p target site in MYCN 3’UTR.

Methods

By a systematic investigation combining microarray, informatics and luciferase reporter assay, we identified that the transcriptional factor pleiomorphic adenoma gene-like 2 (PLAGL2) is a direct target of miR-506-3p that mediates its regulation on MYCN expression. Using CHIP-PCR and luciferase reporter assay, we validated the transcriptional regulation of MYCN by PLAGL2 and we further demonstrated the transcriptional regulation of PLAGL2 by MYCN. We examined the function of PLAGL2 in regulating neuroblastoma cell fate by cell viability assay, colony formation and Western blotting of differentiation markers. We examined the effect of retinoic acid, the differentiation agent used in neuroblastoma therapy, on miR-506-3p, PLAGL2 and MYCN expressions by quantitative PCR and Western blots. We investigated the clinical relevance of PLAGL2 expression by examining the correlation of tumor PLAGL2 mRNA levels with MYCN mRNA expression and patient survival using public neuroblastoma patient datasets.

Results

We found that miR-506-3p directly down-regulated PLAGL2 expression, and we validated a PLAGL2 binding site in the MYCN promoter region responsible for promoting MYCN transcription, thereby establishing a mechanism through which miR-506-3p regulates MYCN expression. Conversely, we discovered that MYCN regulated PLAGL2 transcription through five N-Myc-binding E-boxes in the PLAGL2 promoter region. We further confirmed the reciprocal regulation between endogenous PLAGL2 and MYCN in multiple neuroblastoma cell lines. Moreover, we found that PLAGL2 knockdown induced neuroblastoma cell differentiation and reduced cell proliferation, and combined knockdown of PLAGL2 and MYCN showed a synergistic effect. More strikingly, we found that high tumor PLAGL2 mRNA levels were significantly correlated with high MYCN mRNA levels and poor patient survival in neuroblastoma patients. Furthermore, we found that retinoic acid increased expression of miR-506-3p and repressed expression of MYCN and PLAGL2.

Conclusions

Our findings altogether suggest that the interplay network formed by PLAGL2, MYCN and miR-506-3p is an important mechanism in regulating neuroblastoma cell fate, determining neuroblastoma prognosis, and mediating the therapeutic function of retinoic acid.

Circ-SOX4 drives the tumorigenesis and development of lung adenocarcinoma via sponging miR-1270 and modulating PLAGL2 to activate WNT signaling pathway

Background

Lung adenocarcinoma (LUAD), a widespread histopathological subtype of lung cancer, is deemed as a malignant tumor with a peak risk of mortality. Emerged as RNA with a loop structure that depleted protein coding ability, circular RNA (circRNA) has been identified as a regulator in cancer progression. Circ-SOX4, identified as a novel circRNA, has not been studied in any cancer yet. Thus, the regulatory function that circ-SOX4 exerts on LUAD development remains obscure.

Aim of the study

This study aimed to investigate the biological function and molecular mechanism of circ-SOX4 in LUAD.

Methods

The expression of circ-SOX4 was detected by qRT-PCR. CCK-8, colony formation, transwell and wound healing assays were performed to explore the biological function of circ-SOX4 in LUAD. The interaction between miR-1270 and circ-SOX41 (or PLAGL2) was confirmed by RNA pull down, luciferase reporter and RIP assays.

Results

Circ-SOX4 was found to be obviously upregulated in LUAD tissues and cells, and knockdown of it inhibited cell proliferation, invasion and migration in LUAD. Furthermore, silenced circ-SOX4 also inhibited LUAD tumor growth. Molecular mechanism assays revealed that circ-SOX4 interacted with miR-1270 in LUAD. Besides, PLAGL2 was confirmed as a downstream gene of miR-1270. Rescue assays validated that miR-1270 suppression or PLAGL2 overexpression countervailed circ-SOX4 depletion-mediated inhibition on cell proliferation, invasion and migration in LUAD. Additionally, it was discovered that circ-SOX4/miR-1270/PLAGL2 axis activated WNT signaling pathway in LUAD.

Conclusions

Circ-SOX4 boosted the development of LUAD and activate WNT signaling pathway through sponging miR-1270 and modulating PLAGL2, which provided a valuable theoretical basis for exploring underlying therapeutic target in LUAD.

PLAGL2 and POFUT1 are regulated by an evolutionarily conserved bidirectional promoter and are collaboratively involved in colorectal cancer by maintaining stemness

Background

Our previous study revealed that PLAGL2 or POFUT1 can promote tumorigenesis and maintain significant positive correlations in colorectal cancer (CRC). However, the mechanism leading to the co-expression and the underlying functional and biological implications remain unclear.

Methods

Clinical tumor tissues and TCGA dataset were utilized to analyze the co-expression of PLAGL2 and POFUT1. Luciferase reporter assays, specially made bidirectional promoter vectors and ectopic expression of 3’UTR were employed to study the mechanisms of co-expression. In vitro and in vivo assays were performed to further confirm the oncogenic function of both. The sphere formation assay, immunofluorescence, Western blot and qRT-PCR were performed to investigate the effect of both genes in colorectal cancer stem cells (CSCs).

Findings

PLAGL2 and POFUT1 maintained co-expression in CRC (r = 0.91, p < .0001). An evolutionarily conserved bidirectional promoter, rather than post-transcriptional regulation by competing endogenous RNAs, caused the co-expression of PLAGL2 and POFUT1 in CRC. The bidirectional gene pair PLAGL2/POFUT1 was subverted in CRC and acted synergistically to promote colorectal tumorigenesis by maintaining stemness of colorectal cancer stem cells through the Wnt and Notch pathways. Finally, PLAGL2 and POFUT1 share transcription factor binding sites, and introducing mutations into promoter regions with shared transcription regulatory elements led to a decrease in the PLAGL2/POFUT1 promoter activity in both directions.

Interpretation

Our team identified for the first time a bidirectional promoter pair oncogene, PLAGL2-POFUT1, in CRC. The two genes synergistically promote the progression of CRC and affect the characteristics of CSCs, which can offer promising intervention targets for clinicians and researchers.

Fund

National Nature Science Foundation of China, the Hunan province projects of Postgraduate Independent Exploration and Innovation of Central South University.

The Zinc Finger Transcription Factor PLAGL2 Enhances Stem Cell Fate and Activates Expression of ASCL2 in Intestinal Epithelial Cells

Intestinal epithelial stem cell (IESC) fate is promoted by two major transcriptional regulators, the TCF4/β-catenin complex and ASCL2, which drive expression of IESC-specific factors, including Lgr5, Ephb2, and Rnf43. Canonical Wnt signaling via TCF4/β-catenin directly transactivates Ascl2, which in turn auto-regulates its own expression. Conversely, Let-7 microRNAs antagonize the IESC lineage by repressing specific mRNA targets. Here, we identify the zinc finger transcription factor PLAGL2 as a Let-7 target that regulates IESC fate. PLAGL2 drives an IESC expression signature, activates Wnt gene expression, and enhances a TCF/LEF reporter in intestinal organoids. In parallel, via cell-autonomous mechanisms, PLAGL2 is required for lineage clonal expansion and directly enhances expression of ASCL2. PLAGL2 also supports enteroid growth and survival in the context of Wnt ligand depletion. PLAGL2 expression is strongly associated with an IESC signature in colorectal cancer and may be responsible for contributing to the aberrant activation of an immature phenotype.

MiR-449a suppresses cell migration and invasion by targeting PLAGL2 in breast cancer

BACKGROUND

Breast cancer is one of the most common malignancies worldwide. However, the detailed molecular mechanisms underlying breast cancer metastasis are still incompletely clear. MicroRNAs (miRNAs) play a crucial role in cancer metastasis. In this study, we aimed to analyze the expression and function of miR-449a in breast cancer.

MATERIAL AND METHODS

A total of 15 human primary breast cancer tissues and adjacent non-cancerous tissues (10 pairs) were obtained. MiR-449a was examined in tumor tissues and adjacent nontumorous tissues of breast cancer patients and cell lines by real-time PCR. The protein expression levels were analyzed by western blot and immunohistochemistry staining. Luciferase reporter assays was used to validate the target of miR-449a. The effect of miR-449a on breast cancer cell migration and invasion were studied in vitro and in vivo.

RESULTS

The expression levels of miR-449a were significantly decreased in breast cancer tissues and cell lines. Overexpression of miR-449a suppressed breast cancer cell proliferation, clone formation, migration, invasion and metastasis in vitro and in vivo. Pleomorphic adenoma gene like-2 (PLAGL2) was identified as a major target of miR-449a. Both overexpression of miR-449a inhibited the expression of PLAGL2 significantly and the knockdown of PLAGL2 expression inhibited the breast cancer cell proliferation and metastasis.

CONCLUSION

We demonstrate the miR-449a tumor suppressor role in breast cancer cell migration and invasion via targeting PLAGL2. These findings suggesting that miR-449a/PLAGL2 could serve as a therapeutic strategy for targeting breast cancer.

The role of pleomorphic adenoma gene-like 2 in gastrointestinal cancer development, progression, and prognosis

Numerous previous studies have revealed that pleomorphic adenoma gene-like 2 (PLAGL2) is a transcription factor that is active in cancer progression. The aim of this study was to investigate the role of PLAGL2 in the development, progression and prognosis of gastrointestinal cancer. Immunohistochemical analysis revealed that PLAGL2 was expressed in gastrointestinal tumors and adjacent normal tissues. The expression of PLAGL2 was significantly higher in 225 colorectal cancer tissues than in 66 adjacent non-tumor tissues (P = 0.037). However, expression was not significantly different between 286 gastric tumors and 57 adjacent non-tumor tissues (P = 0.352). Moreover, the PLAGL2 expression level significantly correlated with the depth of tumor invasion in colorectal cancer (P = 0.030). However, the PLAGL2 expression level significantly correlated with tumor size in gastric cancer (P = 0.046). Furthermore, we performed survival analyses and found that neither higher nor lower PLAGL2 expression was a prognostic factor in gastrointestinal cancer. Our findings indicate that PALGL2 serves as a tumor oncoprotein in the development and progression of colorectal cancer. However, the role of this protein in the development, progression and prognosis of gastric cancer is uncertain. Further investigation into the molecular mechanisms of PLAGL2 activity in gastrointestinal cancer is warranted.