IF high-dose intraperitoneal vitamin C (ascorbate; 400 mg/kg/day) combined with low-dose azacitidine (0.25 mg/kg/day, 5 days/week, subcutaneous) is administered to naturally aged (18–22 month), male and female Tet2+/− C57BL/6 mice for 8 consecutive weeks without prior transplantation conditioning,

THEN a measurable reversal of accumulated epigenetic damage will be observed — specifically: (1) ≥20% reduction in Tet2-mutant HSPC variant allele fraction (VAF) relative to baseline and vehicle controls, (2) restoration of gene body 5-hydroxymethylcytosine (5hmC) density at inflammatory loci (e.g., Il1b, Nlrp3, Il6) in bone marrow-derived macrophages (BM-DMs), (3) ≥30% reduction in circulating IL-1β and suppression of NLRP3 inflammasome activation (ASC speck formation) in peritoneal macrophages, and (4) measurable reversal of cardiac inflammatory remodeling markers (myocardial IL-1β immunofluorescence, plasma BNP),

BECAUSE the following causal chain operates:

1. TET2 haploinsufficiency in aged HSPCs depletes genomic 5hmC, generating two distinct but synergistic damage substrates: hypermethylated stem cell enhancers driving aberrant self-renewal, AND depleted gene body 5hmC in already-differentiated Tet2-mutant macrophages — the latter of which removes an aging-relevant transcriptional buffering mechanism that normally restricts the magnitude of inflammatory gene expression during cellular stress (Gene body 5hmC restricts transcriptional variance during aging)[https://doi.org/10.1101/2023.02.15.528714].

2. Pharmacological ascorbate (400 mg/kg IP) regenerates Fe(II) at the TET2 active site via reduction of Fe(III), hyperactivating the remaining wild-type Tet2 allele in haploinsufficient HSPCs and TET1/TET3 in homozygous-null cells, thereby restoring 5hmC at HSC self-renewal enhancers, inducing myeloid differentiation, and directly repairing gene body 5hmC depletion in Tet2-mutant macrophages (Cimmino et al., Cell, 2017; Agathocleous et al., Nature, 2017, as cited in Evidence Set).

3. Low-dose azacitidine (0.25 mg/kg/day) covalently traps and degrades DNMT1 in actively cycling Tet2-null HSPCs that vitamin C alone cannot epigenetically rescue, passively depleting 5mC and inducing terminal myeloid differentiation — creating a selective synthetic epigenetic pressure that eliminates the already-expanded mutant clone fraction (Bejar et al., TET2 mutations predict HMA response, as cited in Evidence Set).

4. Crucially, the restoration of gene body 5hmC in Tet2-mutant macrophages by ascorbate suppresses the transcriptional hyperactivation of Nlrp3 and Il1b, directly breaking the NLRP3 inflammasome → IL-1β → inflammatory niche → mutant clone fitness positive feedback loop that sustains clonal expansion in aged tissue (Sano et al., JACC, 2018; Fuster et al., Science, 2017, as cited in Evidence Set) [SPECULATIVE link: gene body 5hmC loss at Nlrp3 specifically amplifies NLRP3 transcript variance in aged macrophages — this r...

SENS category: OncoSENS

Key references: • doi.org/10.1101/2023.02.15.528714]. • doi.org/10.1101/2023.02.15.528714], • doi.org/10.1101/2023.02.15.528714]