Xiuxing Wang

Zika virus has oncolytic activity against glioblastoma stem cells

Glioblastoma is a highly lethal brain cancer that frequently recurs in proximity to the original resection cavity. We explored the use of oncolytic virus therapy against glioblastoma with Zika virus (ZIKV), a flavivirus that induces cell death and differentiation of neural precursor cells in the developing fetus. ZIKV preferentially infected and killed glioblastoma stem cells (GSCs) relative to differentiated tumor progeny or normal neuronal cells. The effects against GSCs were not a general property of neurotropic flaviviruses, as West Nile virus indiscriminately killed both tumor and normal neural cells. ZIKV potently depleted patient-derived GSCs grown in culture and in organoids. Moreover, mice with glioblastoma survived substantially longer and at greater rates when the tumor was inoculated with a mouse-adapted strain of ZIKV. Our results suggest that ZIKV is an oncolytic virus that can preferentially target GSCs; thus, genetically modified strains that further optimize safety could have therapeutic efficacy for adult glioblastoma patients.

Altered protein prenylation in Sertoli cells is associated with adult infertility resulting from childhood mumps infection

Loss of GGPPS from childhood mumps infection or deletion in mice results in constitutively activated MAPK and NF-kB signaling that induces spermatogonium apoptosis, macrophage invasion into seminiferous tubules, and sterility.

Targeting glioma stem cells through combined BMI1 and EZH2 inhibition

Glioblastomas are lethal cancers defined by angiogenesis and pseudopalisading necrosis. Here, we demonstrate that these histological features are associated with distinct transcriptional programs, with vascular regions showing a proneural profile, and hypoxic regions showing a mesenchymal pattern. As these regions harbor glioma stem cells (GSCs), we investigated the epigenetic regulation of these two niches. Proneural, perivascular GSCs activated EZH2, whereas mesenchymal GSCs in hypoxic regions expressed BMI1 protein, which promoted cellular survival under stress due to downregulation of the E3 ligase RNF144A. Using both genetic and pharmacologic inhibition, we found that proneural GSCs are preferentially sensitive to EZH2 disruption, whereas mesenchymal GSCs are more sensitive to BMI1 inhibition. Given that glioblastomas contain both proneural and mesenchymal GSCs, combined EZH2 and BMI1 targeting proved more effective than either agent alone both in culture and in vivo, suggesting that strategies that simultaneously target multiple epigenetic regulators within glioblastomas may be effective in overcoming therapy resistance caused by intratumoral heterogeneity.

RBPJ maintains brain tumor–initiating cells through CDK9-mediated transcriptional elongation

Glioblastomas co-opt stem cell regulatory pathways to maintain brain tumor-initiating cells (BTICs), also known as cancer stem cells. NOTCH signaling has been a molecular target in BTICs, but NOTCH antagonists have demonstrated limited efficacy in clinical trials. Recombining binding protein suppressor of hairless (RBPJ) is considered a central transcriptional mediator of NOTCH activity. Here, we report that pharmacologic NOTCH inhibitors were less effective than targeting RBPJ in suppressing tumor growth. While NOTCH inhibitors decreased canonical NOTCH gene expression, RBPJ regulated a distinct profile of genes critical to BTIC stemness and cell cycle progression. RBPJ was preferentially expressed by BTICs and required for BTIC self-renewal and tumor growth. MYC, a key BTIC regulator, bound the RBPJ promoter and treatment with a bromodomain and extraterminal domain (BET) family bromodomain inhibitor decreased MYC and RBPJ expression. Proteomic studies demonstrated that RBPJ binds CDK9, a component of positive transcription elongation factor b (P-TEFb), to target gene promoters, enhancing transcriptional elongation. Collectively, RBPJ links MYC and transcriptional control through CDK9, providing potential nodes of fragility for therapeutic intervention, potentially distinct from NOTCH.

Protein prenylation and human diseases: a balance of protein farnesylation and geranylgeranylation.

The protein prenylation is one of the essential post-translational protein modifications, which extensively exists in the eukaryocyte. It includes protein farnesylation and geranylgeranylation, using farnesyl pyrophosphate (FPP) or geranylgeranyl pyrophosphate (GGPP) as the substrate, respectively. The prenylation occurs by covalent addition of these two types of isoprenoids to cysteine residues at or near the carboxyl terminus of the proteins that possess CaaX motif, such as Ras small GTPase family. The attachment of hydrophobic prenyl groups can anchor the proteins to intracellular membranes and trigger downstream cell signaling pathway. Geranylgeranyl biphosphate synthase (GGPPS) catalyzes the synthesis of 20-carbon GGPP from 15-carbon FPP. The abnormal expression of this enzyme will affect the relative content of FPP and GGPP, and thus disrupts the balance between protein farnesylation and geranylgeranylation, which participates into various aspects of cellular physiology and pathology. In this paper, we mainly review the property of this important protein post-translational modification and research progress in its regulation of cigarette smoke induced pulmonary disease, adipocyte insulin sensitivity, the inflammation response of Sertoli cells, the hepatic lipogenesis and the cardiac hypertrophy.

Deubiquitinase USP13 maintains glioblastoma stem cells by antagonizing FBXL14-mediated Myc ubiquitination

Glioblastoma is the most lethal brain tumor and harbors glioma stem cells (GSCs) with potent tumorigenic capacity. The function of GSCs in tumor propagation is maintained by several core transcriptional regulators including c-Myc. c-Myc protein is tightly regulated by posttranslational modification. However, the posttranslational regulatory mechanisms for c-Myc in GSCs have not been defined. In this study, we demonstrate that the deubiquitinase USP13 stabilizes c-Myc by antagonizing FBXL14-mediated ubiquitination to maintain GSC self-renewal and tumorigenic potential. USP13 was preferentially expressed in GSCs, and its depletion potently inhibited GSC proliferation and tumor growth by promoting c-Myc ubiquitination and degradation. In contrast, overexpression of the ubiquitin E3 ligase FBXL14 induced c-Myc degradation, promoted GSC differentiation, and inhibited tumor growth. Ectopic expression of the ubiquitin-insensitive mutant T58A–c-Myc rescued the effects caused by FBXL14 overexpression or USP13 disruption. These data suggest that USP13 and FBXL14 play opposing roles in the regulation of GSCs through reversible ubiquitination of c-Myc.

Tumour-associated macrophages secrete pleiotrophin to promote PTPRZ1 signalling in glioblastoma stem cells for tumour growth

Intense infiltration of tumour-associated macrophages (TAMs) facilitates malignant growth of glioblastoma (GBM), but the underlying mechanisms remain undefined. Herein, we report that TAMs secrete abundant pleiotrophin (PTN) to stimulate glioma stem cells (GSCs) through its receptor PTPRZ1 thus promoting GBM malignant growth through PTN–PTPRZ1 paracrine signalling. PTN expression correlates with infiltration of CD11b+/CD163+ TAMs and poor prognosis of GBM patients. Co-implantation of M2-like macrophages (MLCs) promoted GSC-driven tumour growth, but silencing PTN expression in MLCs mitigated their pro-tumorigenic activity. The PTN receptor PTPRZ1 is preferentially expressed in GSCs and also predicts GBM poor prognosis. Disrupting PTPRZ1 abrogated GSC maintenance and tumorigenic potential. Moreover, blocking the PTN–PTPRZ1 signalling by shRNA or anti-PTPRZ1 antibody potently suppressed GBM tumour growth and prolonged animal survival. Our study uncovered a critical molecular crosstalk between TAMs and GSCs through the PTN–PTPRZ1 paracrine signalling to support GBM malignant growth, indicating that targeting this signalling axis may have therapeutic potential.

Purine synthesis promotes maintenance of brain tumor initiating cells in glioma

Brain tumor initiating cells (BTICs), also known as cancer stem cells, hijack high-affinity glucose uptake active normally in neurons to maintain energy demands. Here we link metabolic dysregulation in human BTICs to a nexus between MYC and de novo purine synthesis, mediating glucose-sustained anabolic metabolism. Inhibiting purine synthesis abrogated BTIC growth, self-renewal and in vivo tumor formation by depleting intracellular pools of purine nucleotides, supporting purine synthesis as a potential therapeutic point of fragility. In contrast, differentiated glioma cells were unaffected by the targeting of purine biosynthetic enzymes, suggesting selective dependence of BTICs. MYC coordinated the control of purine synthetic enzymes, supporting its role in metabolic reprogramming. Elevated expression of purine synthetic enzymes correlated with poor prognosis in glioblastoma patients. Collectively, our results suggest that stem-like glioma cells reprogram their metabolism to self-renew and fuel the tumor hierarchy, revealing potential BTIC cancer dependencies amenable to targeted therapy.

The pig p160 co-activator family: full length cDNA cloning, expression and effects on intramuscular fat content in Longissimus Dorsi muscle.

Evidence has shown in mouse that the p160 co-activator family, consisting of nuclear receptor co-activators 1 (NCOA1), 2 (NCOA2) and 3 (NCOA3) plays a critical role in adipogenesis. In the present study, we cloned these three porcine genes, identified their transcript variants and analyzed their expression level in relation to intramuscular fat (IMF) content in Longissimus Dorsi (LD) muscle. Both in silico cloning and PCR amplification revealed a full length cDNA sequence of 6591bp for NCOA1 (EU346671), 7628bp for NCOA2 (EU346672) and 5005bp for NCOA3 (EU346674) in pigs, respectively. Interestingly, three transcript variants were identified for the porcine NCOA1 and two for the porcine NCOA2 gene. In addition, the deduced amino acid sequences indicated that isoform 2 of NCOA2 lacks the fourth LXXLL motif, the number of which has been shown to influence the selectivity and affinity for different nuclear receptors. Finally, 15 animals with high IMF content and fifteen animals with low IMF content (p<0.05) selected from 60 individuals were used to investigate how the family members and their variants affect the phenotype in pigs using real-time PCR. Our results showed that both NCOA1 transcript variant 2 (r=-0.554, p<0.01) and total NCOA1 (r=-0.516, p<0.01) expression levels were negatively correlated with IMF contents, while NCOA2 transcript variant 1 (r=0.605, p<0.01) and NCOA3 (r=0.435, p<0.05) were positively associated with IMF content in LD muscle. Overall, the present study provides evidence for the first time that the p160 co-activator family might have a concordant effect on lipid metabolism in mammals.

Therapeutic targeting of ependymoma as informed by oncogenic enhancer profiling

Genomic sequencing has driven precision-based oncology therapy; however, the genetic drivers of many malignancies remain unknown or non-targetable, so alternative approaches to the identification of therapeutic leads are necessary. Ependymomas are chemotherapy-resistant brain tumours, which, despite genomic sequencing, lack effective molecular targets. Intracranial ependymomas are segregated on the basis of anatomical location (supratentorial region or posterior fossa) and further divided into distinct molecular subgroups that reflect differences in the age of onset, gender predominance and response to therapy. The most common and aggressive subgroup, posterior fossa ependymoma group A (PF-EPN-A), occurs in young children and appears to lack recurrent somatic mutations. Conversely, posterior fossa ependymoma group B (PF-EPN-B) tumours display frequent large-scale copy number gains and losses but have favourable clinical outcomes. More than 70% of supratentorial ependymomas are defined by highly recurrent gene fusions in the NF-κB subunit gene RELA (ST-EPN-RELA), and a smaller number involve fusion of the gene encoding the transcriptional activator YAP1 (ST-EPN-YAP1). Subependymomas, a distinct histologic variant, can also be found within the supratetorial and posterior fossa compartments, and account for the majority of tumours in the molecular subgroups ST-EPN-SE and PF-EPN-SE. Here we describe mapping of active chromatin landscapes in 42 primary ependymomas in two non-overlapping primary ependymoma cohorts, with the goal of identifying essential super-enhancer-associated genes on which tumour cells depend. Enhancer regions revealed putative oncogenes, molecular targets and pathways; inhibition of these targets with small molecule inhibitors or short hairpin RNA diminished the proliferation of patient-derived neurospheres and increased survival in mouse models of ependymomas. Through profiling of transcriptional enhancers, our study provides a framework for target and drug discovery in other cancers that lack known genetic drivers and are therefore difficult to treat.