Bivalent Genes Targeting of Glioma Heterogeneity and Plasticity

Deciphering glioma epitranscriptome: focus on RNA modifications

Gliomas are highly malignant tumors accounting for the majority of brain neoplasms. They are characterized by nuclear atypia, high mitotic rate and cellular polymorphism that often contributes to aggressiveness and resistance to standard therapy. They often associate with challenging treatment approaches and poor outcomes. New treatment strategies or regimens to improve the efficacy of glioma treatment require a deeper understanding of glioma occurrence and development as well as elucidation of their molecular biological characteristics. Recent studies have revealed RNA modifications as a key regulatory mechanism involved in tumorigenesis, tumor progression, immune regulation, and response to therapy. The present review discusses research advances on several RNA modifications involved in glioma progression and tumor microenvironment (TME) immunoregulation as well as in the development of adaptive drug resistance, summarizing current progress on major RNA modification targeting strategies.

Impact of Solute Carrier Transporters in Glioma Pathology: A Comprehensive Review

Solute carriers (SLCs) are essential for brain physiology and homeostasis due to their role in transporting necessary substances across cell membranes. There is an increasing need to further unravel their pathophysiological implications since they have been proposed to play a pivotal role in brain tumor development, progression, and the formation of the tumor microenvironment (TME) through the upregulation and downregulation of various amino acid transporters. Due to their implication in malignancy and tumor progression, SLCs are currently positioned at the center of novel pharmacological targeting strategies and drug development. In this review, we discuss the key structural and functional characteristics of the main SLC family members involved in glioma pathogenesis, along with their potential targeting options to provide new opportunities for CNS drug design and more effective glioma management.

Pan-cancer analysis revealed H3K4me1 at bivalent promoters premarks DNA hypermethylation during tumor development and identified the regulatory role of DNA methylation in relation to histone modifications

BACKGROUND

DNA hypermethylation at promoter CpG islands (CGIs) is a hallmark of cancers and could lead to dysregulation of gene expression in the development of cancers, however, its dynamics and regulatory mechanisms remain elusive. Bivalent genes, that direct development and differentiation of stem cells, are found to be frequent targets of hypermethylation in cancers.

RESULTS

Here we performed comprehensive analysis across multiple cancer types and identified that the decrease in H3K4me1 levels coincides with DNA hypermethylation at the bivalent promoter CGIs during tumorigenesis. Removal of DNA hypermethylation leads to increment of H3K4me1 at promoter CGIs with preference for bivalent genes. Nevertheless, the alteration of H3K4me1 by overexpressing or knockout LSD1, the demethylase of H3K4, doesn't change the level or pattern of DNA methylation. Moreover, LSD1 was found to regulate the expression of a bivalent gene OVOL2 to promote tumorigenesis. Knockdown of OVOL2 in LSD1 knockout HCT116 cells restored the cancer cell phenotype.

CONCLUSION

In summary, our work identified a universal indicator that can pre-mark DNA hypermethylation in cancer cells, and dissected the interplay between H3K4me1 and DNA hypermethylation in detail. Current study also reveals a novel mechanism underlying the oncogenic role of LSD1, providing clues for cancer therapies.

CIMP-positive glioma is associated with better prognosis: A systematic analysis

BACKGROUND

CpG island methylator phenotype (CIMP) was closely related to the degree of pathological differentiation of tumors, and it's an important determinant of glioma pathogenicity. However, the molecular and pathological features of CIMP-positive glioma have not been fully elucidated. In addition, CIMP have been reported to be a useful prognostic marker in several human cancers, yet its prognostic value in gliomas is still controversial. Therefore, we aimed to evaluate gene mutations and pathological features of CIMP-positive glioma and explore the prognostic value of CIMP in gliomas.

METHODS

We comprehensively searched PubMed, Embase, and MEDLINE for studies describing gene mutations, pathological features and overall survival of gliomas stratified by CIMP status. Odds ratios (OR), hazard ratios (HR), and their 95% confidence intervals (CI) were used to estimate the correlation between CIMP and the outcome parameters.

RESULTS

Twelve studies with 2386 gliomas (1051 CIMP-positive and 1335 CIMP-negative) were included. Our results showed that CIMP was more frequent in isocitrate dehydrogenase 1 (IDH1)-mutated gliomas (OR 229.07; 95% CI 138.72-378.26) and 1p19q loss of heterozygosis (LOH) gliomas (OR 5.65; 95% CI 2.66-12.01). Pathological analysis showed that CIMP was common in low-malignant oligodendroglioma (OR 5.51; 95% CI 3.95-7.70) with molecular features including IDH1 mutations and 1p19q LOH, but rare in glioblastoma (OR 0.14; 95% CI 0.10-0.19). However, CIMP showed no obvious correlation with anaplastic oligoastrocytomas (OR 1.57; 95% CI 1.24-2.00) or oligoastrocytomas (OR 0.79; 95% CI 0.35-1.76). Concerning the prognosis, we found that CIMP-positive gliomas had longer overall survival (HR 0.57; 95% CI 0.97-0.16) than CIMP-negative gliomas.

CONCLUSIONS

CIMP could be used as a potential independent prognostic indicator for glioma.

Comprehensive analysis of epigenetics regulation, prognostic and the correlation with immune infiltrates of GPX7 in adult gliomas

Gliomas are the most commonly occurring malignant brain tumor characterized by an immunosuppressive microenvironment accompanied by profound epigenetic changes, thus influencing the prognosis. Glutathione peroxidase 7 (GPX7) is essential for regulating reactive oxygen species homeostasis under oxidative stress. However, little is known about the function of GPX7 in gliomas. In this study, we hypothesized that GPX7 methylation status could influence biological functions and local immune responses that ultimately impact prognosis in adult gliomas. We conducted an integrated bioinformatics analysis mining GPX7 DNA methylation status, transcriptional and survival data of glioma patients. We discovered that GPX7 was remarkably increased in glioma tissues and cell lines, and was associated with poor prognosis. This upregulation was significantly linked to clinicopathological and molecular features, besides being expressed in a cell cycle-dependent manner. Our results consistently demonstrated that upregulation of GPX7 is tightly modulated by epigenetic processes, which also impacted the overall survival of patients with low-grade gliomas (LGG). Based on the analysis of biological functions, we found that GPX7 might be involved in immune mechanisms involving both innate and adaptive immunity, type I interferon production and regulation of synaptic transmission in LGG, whereas in GBM, it is mainly related to metabolic regulation of mitochondrial dynamics. We also found that GPX7 strongly correlates with immune cell infiltration and diverse immune cell markers, suggesting its role in tumor-specific immune response and in regulating the migration of immune cell types to the tumor microenvironment. Combining these multiple data, we provided the first evidence regarding the epigenetic-mediated regulatory mechanisms underlying GPX7 activation in gliomas. Furthermore, our study brings key insights into the significant effect of GPX7 in modulating both immune molecules and in immune cell infiltration in the microenvironment of gliomas, which might impact the patient outcome, opening up future opportunities to regulate the local immune response.

Epigenetic targeting of SLC30A3 by HDAC1 is related to the malignant phenotype of glioblastoma

The epigenetic abnormality is believed as a major driver for cancer initiation. Histone modification plays a vital role in tumor formation and progression. Particularly, alteration in histone acetylation has been highly associated with gene expression, cell cycle, as well as carcinogenesis. By analyzing glioblastoma (GBM)-related microarray from the GEO database and conducting chromatin immunoprecipitation-sequencing (ChIP-seq), we discovered that solute carrier family 30 member 3 (SLC30A3), a super enhancer (SE)-regulated factor, was significantly reduced in GBM tissues. Furthermore, histone deacetylase 1 (HDAC1), overexpressed in GBM tissues, could inhibit SLC30A3 expression by promoting histone H3K27ac deacetylation modification of the SE region of SLC30A3. Our functional validation revealed that SLC30A3 can inhibit the growth and metastatic spread of GBM cells in vitro and in vivo, and can activate the MAPK signaling pathway to promote apoptosis of GBM cells. Moreover, overexpression of HDAC1 resulted in a significant increase in DNA replication activity, a significant decline in apoptosis and cell cycle arrest in GBM cells. In a word, these findings indicate that combined epigenetic targeting of SLC30A3 by HDAC1 and SE is potentially therapeutically feasible in GBM.