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IDH1 mutation‐inspired α‐ketoglutaric acid mimics for oxidative therapy of higher grade gliomas through α‐ketoglutarate dehydrogenase inhibition
Author(s) -
Madala Hanumantha Rao,
Punganuru Surendra Reddy,
Srivenugopal Kalkunte
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.797.6
Subject(s) - isocitrate dehydrogenase , epigenetics , cancer research , chemistry , metabolite , o 6 methylguanine dna methyltransferase , carcinogenesis , oxidative stress , glioma , histone , biochemistry , methyltransferase , biology , dna , enzyme , gene , methylation
Mutations at the active site of isocitrate dehydrogenase 1 gene (IDH1; R132H) occur at a high frequency (>70%) early in the oncogenesis of lower grade malignant gliomas, and result in a dramatic accumulation of the oncometabolite D‐2 hydroxyglutarate (D‐2HG), that effectively replaces the normal metabolite α‐ketoglutarate (α‐KG) in cell physiology. Surprisingly, IDH1 mutations bestow superior therapeutic responses to alkylating agents and better patient survival. D‐2HG, effectively competes with α‐KG and potently inhibits various dioxygenase reactions, including the TET1&2 DNA ‐demethylases and histone demethylases thereby, re‐shaping and reprogramming the epigenetic landscape, and consequent transcriptional silencing; the DNA repair protein O6‐lguanine DNA methyltransferase (MGMT), which confers drug resistance is one major target for such repression. As a novel and innovative strategy of turning the tide against GBMs by exploiting the mechanistic aspects of the oncometabolite, we hypothesized that D‐2HG and α‐KG derivatives that can replace the natural metabolite in epigenomic dioxygenase reactions will serve as potent anti‐glioma drugs either by themselves or in combination with the alkylating agents. To this end, we synthesized a 2,4‐dimethyleneglutaric acid (DMG), an α‐KG mimic with methylene groups inserted at the C2 and C4 positions. The hydrophobic DMG ester, by itself, was cytotoxic with IC 50 values up to 300 μM against brain tumor cell lines, however, when combined at 100 μM with TMZ resulted in >20‐fold increased synergistic cell killing. DMG induced oxidative stress inhibited α‐KG dehydrogenase, MGMT and TET1&2. DMG induced oxidative stress further caused mitochondrial damage as confirmed with JC‐1 staining. Mitochondrial damage further affected its biosynthetic, bioenergetic and signaling functions as confirmed with respective assays. We also observed a marked reduction in ATP and NADH levels and rapid metabolic flux changes indicating an altered cellular metabolism. Metabolomic analysis of major Krebs cycle intermediates revealed significant decrease in their levels. We, further observed that, bioenergetic stress induced by DMG activated AMPK and inhibited mTOR signaling cascade. Sub‐acute toxicity on mice revealed the safety of DMG in mice and we observed significant regression in tumor growth in intracranial xenograft tumor models. Collectively, these data reveal that acute treatments of α‐KG analogs can alter the cellular metabolic and epigenetic makeup in a manner ascribed to D‐2HG, and open up much‐needed novel and exciting avenues of oncometabolite‐based therapies for brain tumors Support or Funding Information CPRIT grants RP130266 and RP170207 to KSS This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .