Involvement of the Catecholamine Pathway in Glioblastoma Development

Abstract

Glioblastoma (GBM) is the most aggressive tumor of the central nervous system (CNS). The standard of care improves the overall survival of patients only by a few months. Explorations of new therapeutic targets related to molecular properties of the tumor are under way. Even though neurotransmitters and their receptors normally function as mediators of interneuronal communication, growing data suggest that these molecules are also involved in modulating the development and growth of GBM by acting on neuronal and glioblastoma stem cells. In our previous DNA CpG methylation studies, gene ontology analyses revealed the involvement of the monoamine pathway in sequential GBM. In this follow-up study, we quantitated the expression levels of four selected catecholamine pathway markers (alpha 1D adrenergic receptor—ADRA1D; adrenergic beta receptor kinase 1 or G protein-coupled receptor kinase 2—ADRBK1/GRK2; dopamine receptor D2—DRD2; and synaptic vesicle monoamine transporter—SLC18A2) by immunohistochemistry, and compared the histological scores with the methylation levels within the promoters + genes of these markers in 21 pairs of sequential GBM and in controls. Subsequently, we also determined the promoter and gene methylation levels of the same markers in an independent database cohort of sequential GBM pairs. These analyses revealed partial inverse correlations between the catecholamine protein expression and promoter + gene methylation levels, when the tumor and control samples were compared. However, we found no differences in the promoter + gene methylation levels of these markers in either our own or in the database primary–recurrent GBM pairs, despite the higher protein expression of all markers in the primary samples. This observation suggests that regulation of catecholamine expression is only partially related to CpG methylation within the promoter + gene regions, and additional mechanisms may also influence the expression of these markers in progressive GBM. These analyses underscore the involvement of certain catecholamine pathway markers in GBM development and suggest that these molecules mediating or modulating tumor growth merit further exploration.

Epigenetic Suppression of the IL-7 Pathway in Progressive Glioblastoma

“…None of the patients were alive at the time of the initiation of the original epigenomic analyses in 2018–2019 [ 5 ]; the histological diagnoses of the obtained tumor specimens were based on the 2016 WHO guideline [ 12 ]. As additional immunohistochemical studies were subsequently also performed and reported on the same tissue specimens [ 5 , 6 , 7 ], no sufficient tissue remained for complementary testing of those molecular alterations (i.e., H3F3A, HIST1H3B, HIST1H3C, TERT, EGFR-amplification) recommended in the 2021 WHO revision [ 13 ]. As Table S1 shows, however, all tumors were late-onset GBMs, and thus mutations in histone proteins would be very unlikely.…”

“…Methylomes of five epilepsy surgery specimens (CG) obtained from the European Nucleotide Archive [ 14 ] ( , Primary Accession: PRJNA391429; EGAS00001002538 accessed on 17 June 2022) were used as controls in the DNA CpG methylation analyses in comparisons with GBM prim and GBM rec [ 5 , 6 , 7 ].…”

“…We observed that analyzing CpG sites only within the (approx. 2000 bp) gene promoters in our relatively small cohorts could not provide statistically meaningful outcomes for defining differential methylation [ 6 , 7 ]. The methylation levels were expressed as percentages where the numerators were calculated from the numbers of methylated sites (with the degree of methylation also computed into the figures), and the denominators were the numbers of all CpG sites within the investigated region, and multiplied by 100.…”

“…In a previous study, relying on the Restricted Resolution Bisulfite Sequencing (RRBS) technology, we detected several differentially methylated pathways (DMP) in primary and recurrent FFPE GBM specimens [ 5 ]. Subsequently, we further investigated the most outstanding DMPs, the Wnt and catecholamine pathways, by comparing the promoter and gene methylation profiles with protein expression levels of their elements in the same specimens [ 6 , 7 ]. In the present study, we investigated in more depth the third-most outstanding DMP, the immune pathways that have not been previously scrutinized [ 5 ].…”

Molecular Biology in Glioblastoma Multiforme Treatment

“…Kraboth and colleagues [ 8 ] explore the role of DNA CpG methylation in modulating the expression of neurotransmitters in GBM. These molecules have a well-known role in CNS development and physiology but have been found to be equally important in GBM, due to their interplay with neurons and glioma cells [ 9 , 10 ].…”