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Lymphocyte proliferation and tumourigenesis are dependent on nucleotide synthesis to support DNA, RNA and phospholipid synthesis. Here, we identified that reprogramming of nucleotide metabolism as an important factor divides mantle cell lymphoma (MCL) into two groups with different transcriptional signalling pathways and varying prognoses. We establish a nucleotide metabolism‐related prognostic model that includes six genes with different regression coefficients, which significantly predicts prognosis for MCL patients (p < 0.0001). Of these six genes, de novo CTP synthesis pathway enzyme CTPS1 whose inhibitor (STP938) is already in clinical trials for relapsed/refractory lymphomas (NCT05463263) has the highest regression coefficient. An increase in CTPS1 expression predicts adverse overall survival and progression‐free survival with independent prognostic significance in 105 primary MCL samples and GEO database (GSE93291). CRISPR CTPS1 knockout causes DNA damage and proliferation defects in MCL. Additionally, MYC positively regulates CTPS1 expression, and TP53‐aberrant and ibrutinib‐resistant MCL cells also rely on cytidine metabolism. Furthermore, besides the obvious decreased CTP pool caused by CTPS1 deficiency, CTPS1 inhibition may also induce immune‐related responses via activating dsDNA‐cGAS‐STING pathway, which plays a crucial role in impeding tumour growth in MCL patients. [ABSTRACT FROM AUTHOR]

Abstract: A major role of plasma membrane bound ectonucleotidases is the modulation of ATP, ADP, adenosine (the purinergic agonists), UTP, and UDP (the pyrimidinergic agonists) availability in the extracellular space at their respective receptors. We have recently shown that an ATP driven uridine–UTP cycle is operative in the brain, based on the strictly compartmentalized processes of uridine salvage to UTP and uridine generation from UTP, in which uptaken uridine is anabolized to UTP in the cytosol, and converted back to uridine in the extracellular space by the action of ectonucleotidases (Ipata et al. Int J Biochem Cell Biol 2010;42:932–7). In this paper we show that a similar cytidine–CTP cycle exists in rat brain. Since (i) brain relies on imported preformed nucleosides for the synthesis of nucleotides, RNA, nuclear and mitochondrial DNA, coenzymes, pyrimidine sugar- and lipid-conjugates and (ii) no specific pyrimidinergic receptors have been identified for cytidine and their nucleotides, our results, taken together with previous studies on the intra- and extracellular metabolic network of ATP, GTP, UTP, and their nucleosides in the brain (Barsotti and Ipata. Int J Biochem Cell Biol 2004;36:2214–25; Balestri et al. Neurochem Int 2007;50:517–23), strongly suggest that, apart from the modulation of ligand availability, ectonucleotidases may serve the process of local nucleoside recycling in the brain. [Copyright &y& Elsevier]