skip to main content

Explore Research Products in the NSF-PAR

Title: EZH2 is a key component of hepatoblastoma tumor cell growth
Abstract Background

Enhancer of zeste homolog 2 (EZH2) catalyzes the trimethylation of histone H3 at lysine 27 via the polycomb recessive complex 2 (PRC2) and plays a time‐specific role in normal fetal liver development. EZH2 is overexpressed in hepatoblastoma (HB), an embryonal tumor. EZH2 can also promote tumorigenesis via a noncanonical, PRC2‐independent mechanism via proto‐oncogenic, direct protein interaction, including β‐catenin. We hypothesize that the pathological activation of EZH2 contributes to HB propagation in a PRC2‐independent manner.

 Methods and results

We demonstrate that EZH2 promotes proliferation in HB tumor‐derived cell lines through interaction with β‐catenin. Although aberrant EZH2 expression occurs, we determine that both canonical and noncanonical EZH2 signaling occurs based on specific gene‐expression patterns and interaction with SUZ12, a PRC2 component, and β‐catenin. Silencing and inhibition of EZH2 reduce primary HB cell proliferation.

 Conclusions

EZH2 overexpression promotes HB cell proliferation, with both canonical and noncanonical function detected. However, because EZH2 directly interacts with β‐catenin in human tumors and EZH2 overexpression is not equal to SUZ12, it seems that a noncanonical mechanism is contributing to HB pathogenesis. Further mechanistic studies are necessary to elucidate potential pathogenic downstream mechanisms and translational potential of EZH2 inhibitors for the treatment of HB.

  more » « less
NSF-PAR ID:
10482778
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Pediatric Blood & Cancer
Volume:
71
Issue:
2
ISSN:
1545-5009
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ( , Pediatric Blood & Cancer)
    Abstract Background

    Hepatoblastoma (HB) is the most common pediatric liver malignancy, occurring mainly during the first 4 years of life. Recent studies unraveled the frequent, coordinated activation of Wnt/β‐catenin and YAP/Hippo (where YAP is yes‐associated protein) pathways in human HB samples. Furthermore, it was found that concomitant overexpression of activated forms of β‐catenin and YAP in the mouse liver triggers HB formation in YAP/β‐catenin mice. Cyclin‐dependent kinases 9 (CDK9) is an elongating kinase, which has been shown to mediate YAP‐driven tumorigenesis. The role of CDK9 in HB molecular pathogenesis has not been investigated to date.

     Methods

    CDK9 expression was determined in human HB lesions, HB cell lines, and YAP/β‐catenin mouse livers. CDK9 was silenced in human HB cell lines and the effects on growth rate and YAP targets were analyzed. Hydrodynamic transfection of YAPS127A and ∆N90‐β‐catenin together with either shCdk9 or control shLuc (where Luc is luciferase) plasmids was employed to assess the requirement of Cdk9 for HB development in vivo.

     Results

    Nuclear immunoreactivity for CDK9 protein was more pronounced in human HB samples and YAP/β‐catenin mouse HB tumor tissues than in corresponding surrounding nontumorous liver tissues. CDK9 protein was also expressed in human HB cell lines. Silencing of CDK9 in human HB cell lines did not lead to consistent effects on HB cell growth or YAP target gene expression. Surprisingly, silencing of Cdk9 led to accelerated liver tumorigenesis in YAP/β‐catenin mice.

     Conclusion

    CDK9 is not a major downstream mediator of YAP oncogenic function in HB development and progression.

     
    more » « less
  2. ; ; ; ; ; ; ; ; ; ( , Journal of Neuro-Oncology)
    Abstract Introduction The Polycomb group (PcG) is an important family of transcriptional regulators that controls growth and tumorigenesis. The PcG mainly consists of two complexes, PRC1 and Polycomb Repressive Complex 2 (PRC2). Polycomb-like 2 (PCL2) is known to interact with the PRC2 protein. The role of PCL2 in the development and progression of glioma is unclear. Methods We use The Cancer Genome Atlas (TCGA) database to detect the expression of PCL2 in various tumors. 117 cases of clinical glioma (WHOI–IV) were collected, and PCL2 expression and localization were detected by immunohistochemical staining. Glioma cells U87/U251 were infected with overexpressed and interfered PCL2. CCK8 assay, colony formation assay, EdU method, cell cycle and apoptosis were used to detect cell proliferation and apoptosis. Western blot was used to detect the expression of PRC2-related core proteins. After DZNeP intervention, PRC2 protein expression was again measured to discuss the mechanism of PCL2 action. Results TCGA database results and immunohistochemical staining results suggest that PCL2 is highly expressed in gliomas. We found that the PCL2 gene promoted tumor cell proliferation, enhanced the colony formation ability, and increased S phase in the cell cycle. The overexpression of PCL2 upregulated the expression levels of EZH2 and EED (two core members of PRC2), decreased the expression of SUZ12, increased the level of H3K27 trimethylation (H3K27me3), H3K4 dimethylation (H3K4me2), and decreased H3K9 dimethylation (H3K9me2). The result after interfering with PCL2 was the opposite. Conclusions As an important accessory protein of PRC2, PCL2 can not only change the expression of PRC2 components, but also affect the expression level of Histone methylation. Therefore, PCL2 may be an important hub for regulating the synergy among PRC2 members. This study revealed PCL2 as a new target for tumor research and open up a new avenue for future research in glioma. 
    more » « less
  3. ; ; ; ( , Developmental Dynamics)
    Abstract Background

    While much is known about the genetic regulation of early valvular morphogenesis, mechanisms governing fetal valvular growth and remodeling remain unclear. Hemodynamic forces strongly influence morphogenesis, but it is unknown whether or how they interact with valvulogenic signaling programs. Side‐specific activity of valvulogenic programs motivates the hypothesis that shear stress pattern‐specific endocardial signaling controls the elongation of leaflets.

     Results

    We determined that extension of the semilunar valve occurs via fibrosa sided endocardial proliferation. Low OSS was necessary and sufficient to induce canonical Wnt/β‐catenin activation in fetal valve endothelium, which in turn drives BMP receptor/ligand expression, and pSmad1/5 activity essential for endocardial proliferation. In contrast, ventricularis endocardial cells expressed active Notch1 but minimal pSmad1/5. Endocardial monolayers exposed to LSS attenuate Wnt signaling in a Notch1 dependent manner.

     Conclusions

    Low OSS is transduced by endocardial cells into canonical Wnt signaling programs that regulate BMP signaling and endocardial proliferation. In contrast, high LSS induces Notch signaling in endocardial cells, inhibiting Wnt signaling and thereby restricting growth on the ventricular surface. Our results identify a novel mechanically regulated molecular switch, whereby fluid shear stress drives the growth of valve endothelium, orchestrating the extension of the valve in the direction of blood flow.

     
    more » « less
  4. ; ; ; ; ; ; ( , Sexual Development)
    Temperature-dependent sex determination (TSD) is a well-known characteristic of many reptilian species. However, the molecular processes linking ambient temperature to determination of gonad fate remain hazy. Here, we test the hypothesis that Wnt expression and signaling differ between female- and male-producing temperatures in the snapping turtle Chelydra serpentina. Canonical Wnt signaling involves secretion of glycoproteins called WNTs, which bind to and activate membrane bound receptors that trigger β-catenin stabilization and translocation to the nucleus where β-catenin interacts with TCF/LEF transcription factors to regulate expression of Wnt targets. Non-canonical Wnt signaling occurs via 2 pathways that are independent of β-catenin: one involves intracellular calcium release (the Wnt/Ca2+ pathway), while the other involves activation of RAC1, JNK, and RHOA (the Wnt/planar cell polarity pathway). We screened 20 Wnt genes for differential expression between female- and male-producing temperatures during sex determination in the snapping turtle. Exposure of embryos to the female-producing temperature decreased expression of 7 Wnt genes but increased expression of 2 Wnt genes and Rspo1 relative to embryos at the male-producing temperature. Temperature also regulated expression of putative Wnt target genes in vivo and a canonical Wnt reporter (6x TCF/LEF sites drive H2B-GFP expression) in embryonic gonadal cells in vitro. Results indicate that Wnt signaling was higher at the female- than at the male-producing temperature. Evolutionary analyses of all 20 Wnt genes revealed that thermosensitive Wnts, as opposed to insensitive Wnts, were less likely to show evidence of positive selection and experienced stronger purifying selection within TSD species. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ( , Macromolecular Bioscience)
    Abstract

    The ability of the extracellular matrix (ECM) to instruct progenitor cell differentiation has generated excitement for the development of materials‐based regenerative solutions. Described a nanoparticulate mineralized collagen glycosaminoglycan (MC‐GAG) material capable of inducing in vivo skull regeneration without exogenous growth factors or ex vivo progenitor cell‐priming is described previously. Here, the contribution of titrating stiffness to osteogenicity is evaluated by comparing noncrosslinked (NX‐MC) and crosslinked (MC) forms of MC‐GAG. While both materials are osteogenic, MC demonstrates an increased expression of osteogenic markers and mineralization compared to NX‐MC. Both materials are capable of autogenously activating the canonical BMPR signaling pathway with phosphorylation of Smad1/5. However, unlike NX‐MC, human mesenchymal stem cells cultured on MC demonstrate significant elevations in the major mechanotransduction mediators YAP and TAZ expression, coincident with β‐catenin activation in the canonical Wnt signaling pathway. Inhibition of YAP/TAZ activation reduces osteogenic expression, mineralization, and β‐catenin activation in MC, with less of an effect on NX‐MC. YAP/TAZ inhibition also results in a reciprocal increase in Smad1/5 phosphorylation and BMP2 expression. The results indicate that increasing MC‐GAG stiffness induces osteogenic differentiation via the mechanotransduction mediators YAP/TAZ and the canonical Wnt signaling pathway, whereas the canonical BMPR signaling pathway is activated independent of stiffness.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email