The intricate orchestration of enzymatic activities involving nicotinamide adenine dinucleotide (NAD⁺) is essential for maintaining metabolic homeostasis and preserving genomic integrity. As a co-enzyme, NAD⁺ plays a key role in regulating metabolic pathways, such as glycolysis and Kreb’s cycle. ADP-ribosyltransferases (PARPs) and sirtuins rely on NAD⁺ to mediate post-translational modifications of target proteins. The activation of PARP1 in response to DNA breaks leads to rapid depletion of cellular NAD⁺ compromising cell viability. Therefore, the levels of NAD⁺ must be tightly regulated. Here we show that exogenous NAD⁺, but not its precursors, has a direct effect on mitochondrial activity. Short-term incubation with NAD⁺ boosts Kreb’s cycle and the electron transport chain and enhances pyrimidine biosynthesis. Extended incubation with NAD⁺ results in depletion of pyrimidines, accumulation of purines, activation of the replication stress response and cell cycle arrest. Moreover, a combination of NAD⁺ and 5-fluorouridine selectively kills cancer cells that rely on de novo pyrimidine synthesis. We propose an integrated model of how NAD⁺ regulates nucleotide metabolism, with relevance to healthspan, ageing and cancer therapy.

Fanconi anemia (FA) is a clinically and genetically heterogeneous disorder characterized by the variable presence of congenital somatic abnormalities, bone marrow failure (BMF), and a predisposition to develop cancer. Monoallelic germline mutations in at least five genes involved in the FA pathway are associated with the development of sporadic hematological and solid malignancies. The key function of the FA pathway is to orchestrate proteins involved in the repair of interstrand cross-links (ICLs), to prevent genomic instability and replication stress. Recently, many studies have highlighted the importance of FA genes in noncanonical pathways, such as mitochondria homeostasis, inflammation, and virophagy, which act, in some cases, independently of DNA repair processes. Thus, primary defects in DNA repair mechanisms of FA patients are typically exacerbated by an impairment of other cytoprotective pathways that contribute to the multifaceted clinical phenotype of this disease. In this review, we summarize recent advances in the understanding of the pathogenesis of FA, with a focus on the cytosolic noncanonical roles of FA genes, discussing how they may contribute to cancer development, thus suggesting opportunities to envisage novel therapeutic approaches.

Medulloblastoma (MB) is a childhood malignant brain tumour comprising four main subgroups characterized by different genetic alterations and rate of mortality. Among MB subgroups, patients with enhanced levels of the c-MYC oncogene (MB_Group3) have the poorest prognosis. Here we identify a previously unrecognized role of the pro-autophagy factor AMBRA1 in regulating MB. We demonstrate that AMBRA1 expression depends on c-MYC levels and correlates with Group 3 patient poor prognosis; also, knockdown of AMBRA1 reduces MB stem potential, growth and migration of MB_Group3 stem cells. At a molecular level, AMBRA1 mediates these effects by suppressing SOCS3, an inhibitor of STAT3 activation. Importantly, pharmacological inhibition of autophagy profoundly affects both stem and invasion potential of MB_Group3 stem cells, and a combined anti-autophagy and anti-STAT3 approach impacts the MB_Group3 outcome. Taken together, our data support the c-MYC/AMBRA1/STAT3 axis as a strong oncogenic signalling pathway with significance for both patient stratification strategies and targeted treatments of MB_Group3.