Protein Arginine (R) methylation is the most common post-translational methylation in mammalian cells. Protein Arginine Methyltransferases (PRMT) 1 and 5 dimethylate their substrates on R residues, asymmetrically and symmetrically, respectively. They are ubiquitously expressed and play fundamental roles in tumour malignancies, including glioblastoma multiforme (GBM) which presents largely deregulated Myc activity. Previously, we demonstrated that PRMT5 associates with Myc in GBM cells, modulating, at least in part, its transcriptional properties. Here we show that Myc/PRMT5 protein complex includes PRMT1, in both HEK293T and glioblastoma stem cells (GSCs). We demonstrate that Myc is both asymmetrically and symmetrically dimethylated by PRMT1 and PRMT5, respectively, and that these modifications differentially regulate its stability. Moreover, we show that the ratio between symmetrically and asymmetrically dimethylated Myc changes in GSCs grown in stem versus differentiating conditions. Finally, both PRMT1 and PRMT5 activity modulate Myc binding at its specific target promoters. To our knowledge, this is the first work reporting R asymmetrical and symmetrical dimethylation as novel Myc post-translational modifications, with different functional properties. This opens a completely unexplored field of investigation in Myc biology and suggests symmetrically dimethylated Myc species as novel diagnostic and prognostic markers and druggable therapeutic targets for GBM.

Nitric oxide (NO) is a diffusible signaling molecule produced by three isoforms of nitric oxide synthase, which release NO during the metabolism of the amino acid arginine. NO participates in pathophysiological responses of many different tissues, inducing concentration-dependent effect. Indeed, while low NO levels generally have protective effects, higher NO concentrations induce cytotoxic/cytostatic actions. In recent years, evidences have been accumulated unveiling S-nitrosylation as a major NO-dependent post-translational mechanism ruling gene expression. S-nitrosylation is a reversible, highly regulated phenomenon in which NO reacts with one or few specific cysteine residues of target proteins generating S-nitrosothiols. By inducing this chemical modification, NO might exert epigenetic regulation through direct effects on both DNA and histones as well as through indirect actions affecting the functions of transcription factors and transcriptional co-regulators. In this light, S-nitrosylation may also impact on cancer cell gene expression programs. Indeed, it affects different cell pathways and functions ranging from the impairment of DNA damage repair to the modulation of the activity of signal transduction molecules, oncogenes, tumor suppressors, and chromatin remodelers. Nitrosylation is therefore a versatile tool by which NO might control gene expression programs in health and disease.

Glioblastoma multiforme (GBM) has high mortality and recurrence rates. Malignancy resilience is ascribed to Glioblastoma Stem Cells (GSCs), which are resistant to Temozolomide (TMZ), the gold standard for GBM post-surgical treatment. However, Nitric Oxide (NO) has demonstrated anti-cancer efficacy in GBM cells, but its potential impact on GSCs remains unexplored. Accordingly, we investigated the effects of NO, both alone and in combination with TMZ, on patient-derived GSCs. Experimentally selected concentrations of diethylenetriamine/NO adduct and TMZ were used through a time course up to 21 days of treatment, to evaluate GSC proliferation and death, functional recovery, and apoptosis. Immunofluorescence and Western blot analyses revealed treatment-induced effects in cell cycle and DNA damage occurrence and repair. Our results showed that NO impairs self-renewal, disrupts cell-cycle progression, and expands the quiescent cells’ population. Consistently, NO triggered a significant but tolerated level of DNA damage, but not apoptosis. Interestingly, NO/TMZ cotreatment further inhibited cell cycle progression, augmented G0 cells, induced cell death, but also enhanced DNA damage repair activity. These findings suggest that, although NO administration does not eliminate GSCs, it stunts their proliferation, and makes cells susceptible to TMZ. The resulting cytostatic effect may potentially allow long-term control over the GSCs’ subpopulation.

Background/Objectives: Mammalian sirtuins (SIRTs) are evolutionarily conserved proteins that are epigenetically involved in biological processes such as metabolism and longevity. SIRT1 expression is reduced in metabolic disorders and in complicated diseases such as obesity. However, whether the SIRT1 level in subcutaneous adipose tissue (SAT) matches with its circulating form in obesity is unknown. The aim of our study is to evaluate SIRT1 derived from SAT and plasma of the same subject in individuals with and without obesity to assess whether plasma measurements may provide clinically significant information. Methods: Eleven subjects with obesity (BMI ≥ 30 kg/m²) and six controls without the disease (BMI < 30 kg/m²) were enrolled, and SIRT1 was measured in SAT and plasma by ELISA. Anthropometric parameters, glycemia and transaminases were also assessed. Results: Patients with obesity showed similar levels of SIRT1 in SAT and plasma (1.28 ± 0.45 and 1.9 ± 0.25 ng/mL, respectively, p = 0.243). Patients without obesity showed higher SIRT1 levels in SAT than in plasma (4.19 ± 1.33 and 1.06 ± 0.12 ng/mL, respectively, p = 0.039). An inverse correlation between SAT-derived SIRT1 and BMI was found (r = −0.632, p = 0.007). Conclusions: In this pilot study, our results show that the plasma SIRT1 levels substantially reflect those of SAT in patients with obesity. Given the metabolic role of SIRT1, further comprehensive investigations in larger longitudinal cohorts are needed to support plasma SIRT1 as an eligible diagnostic tool for stratifying metabolic risk associated with fat mass expansion in obesity.

Lipodystrophies (LDs) are rare, complex disorders of the adipose tissue characterized by selective fat loss, altered adipokine profile and metabolic impairment. Sirtuins (SIRTs) are class III NAD⁺-dependent histone deacetylases linked to fat metabolism. SIRT1 plays a critical role in metabolic health by deacetylating target proteins in tissue types including liver, muscle, and adipose. Circulating SIRT1 levels have been found to be reduced in obesity and increased in anorexia nervosa and patients experiencing weight loss. We evaluated circulating SIRT1 levels in relation to fat levels in 32 lipodystrophic patients affected by congenital or acquired LDs compared to non-LD subjects (24 with anorexia nervosa, 22 normal weight, and 24 with obesity). SIRT1 serum levels were higher in LDs than normal weight subjects (mean ± SEM 4.18 ± 0.48 vs. 2.59 ± 0.20 ng/mL) and subjects with obesity (1.7 ± 0.39 ng/mL), whereas they were close to those measured in anorexia nervosa (3.44 ± 0.46 ng/mL). Our findings show that within the LD group, there was no relationship between SIRT1 levels and the amount of body fat. The mechanisms responsible for secretion and regulation of SIRT1 in LD deserve further investigation.

Lipodystrophies (LDs) are rare, complex disorders of the adipose tissue characterized by selective fat loss, altered adipokines profile and metabolic impairment. Sirtuins (SIRTs) are class III NAD+-dependent histone-deacetylases linked to fat metabolism. SIRT1 plays a critical role in metabolic health by deacetylating target proteins in tissues including liver, muscle and adipose tissue. Circulating SIRT1 levels have been found to be reduced in obesity while increased in anorexia nervosa and in patients experiencing weight loss. We evaluated circulating SIRT1 levels in relation to fat amount in 32 lipodystrophic patients affected by congenital or acquired LDs compared to non-LD subjects (24 with anorexia nervosa, 22 normal weight and 24 with obe-sity). SIRT1 serum levels were higher in LDs as compared with normal weight subjects (mean ± SEM: 4.17 ± 0.48 vs. 2.59 ± 0.20 ng/mL) or subjects with obesity (1.7 ± 0.39 ng/mL), whereas they were close to those measured in anorexia nervosa (3.44 ± 0.46 ng/mL). Our findings show that within the LD group there was no relationship between SIRT1 levels and the amount of body fat. The mechanisms responsible for secretion and regulation of SIRT1 in LD deserve further investi-gation.