Accumulation of oncometabolite D-2-Hydroxyglutarate by SLC25A1 inhibition: A metabolic strategy for induction of HR-ness and radiosensitivity

Abstract

Oncogenic mutations in metabolic genes and associated oncometabolite accumulation support cancer progression but can also restrict cellular functions needed to cope with DNA damage. For example, gain-of-function mutations in isocitrate dehydrogenase (IDH) and the resulting accumulation of the oncometabolite D-2-hydroxyglutarate (D-2-HG) enhanced the sensitivity of cancer cells to inhibition of poly(ADP-ribose)-polymerase (PARP)1 and radiotherapy (RT). In our hand, inhibition of the mitochondrial citrate transport protein (SLC25A1) enhanced radiosensitivity of cancer cells and this was associated with increased levels of D-2-HG and a delayed repair of radiation-induced DNA damage. Here we aimed to explore the suggested contribution of D-2-HG-accumulation to disturbance of DNA repair, presumably homologous recombination (HR) repair, and enhanced radiosensitivity of cancer cells with impaired SLC25A1 function. Genetic and pharmacologic inhibition of SLC25A1 (SLC25A1i) increased D-2-HG-levels and sensitized lung cancer and glioblastoma cells to the cytotoxic action of ionizing radiation (IR). SLC25A1i-mediated radiosensitization was abrogated in MEFs with a HR-defect. D-2-HG-accumulation was associated with increased DNA damage and delayed resolution of IR-induced γH2AX and Rad51 foci. Combining SLC25A1i with PARP- or the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs)-inhibitors further potentiated IR-induced DNA damage, delayed DNA repair kinetics resulting in radiosensitization of cancer cells. Importantly, proof of concept experiments revealed that combining SLC25A1i with IR without and with PARPi also reduced tumor growth in the chorioallantoic membrane (CAM) model in vivo. Thereby SLC25A1i offers an innovative strategy for metabolic induction of context-dependent lethality approaches in combination with RT and clinically relevant inhibitors of complementary DNA repair pathways.

α-Ketoglutarate Supplementation and NAD+ Modulation Enhance Metabolic Rewiring and Radiosensitization in SLC25A1 Inhibited Cancer Cells

“…fumarate hydrotase (FH), Succinate dehydrogenase (SDH) or isocitrate dehydrogenase (IDH)) [8]. Interestingly, our previous work revealed a strategy to induce an accumulation of 2-HG as a common phenotype by inhibiting the mitochondrial citrate carrier SLC25A1 in cancer cells without somatic mutation of IDH [11,12]. SLC25A1 inhibition (SLC25A1i) created a phenotype represented by reduced repair of radiation-induced DNA double strand breaks (DSB) and survival upon radiotherapy (RT) [12].…”

“…Interestingly, our previous work revealed a strategy to induce an accumulation of 2-HG as a common phenotype by inhibiting the mitochondrial citrate carrier SLC25A1 in cancer cells without somatic mutation of IDH [11,12]. SLC25A1 inhibition (SLC25A1i) created a phenotype represented by reduced repair of radiation-induced DNA double strand breaks (DSB) and survival upon radiotherapy (RT) [12]. In more detail, SLC25A1i affected the repair of lethal DNA lesions introduced by ionizing radiation (IR) treatment presumably by inducing accumulation of the oncometabolite D-2-hydroxyglutarate (D-2HG) and associated restriction of homologous recombination (HR) repair [12].…”

“…SLC25A1 inhibition (SLC25A1i) created a phenotype represented by reduced repair of radiation-induced DNA double strand breaks (DSB) and survival upon radiotherapy (RT) [12]. In more detail, SLC25A1i affected the repair of lethal DNA lesions introduced by ionizing radiation (IR) treatment presumably by inducing accumulation of the oncometabolite D-2-hydroxyglutarate (D-2HG) and associated restriction of homologous recombination (HR) repair [12]. Furthermore, targeting SLC25A1 indicated vulnerability of cancer cells to inhibition of poly(ADP-ribose)-polymerase (PARP)1 or the catalytic subunit of DNAdependent protein kinase (DNA-PKcs) in combination with IR suggesting a window for therapeutic opportunity [12].…”

“…In more detail, SLC25A1i affected the repair of lethal DNA lesions introduced by ionizing radiation (IR) treatment presumably by inducing accumulation of the oncometabolite D-2-hydroxyglutarate (D-2HG) and associated restriction of homologous recombination (HR) repair [12]. Furthermore, targeting SLC25A1 indicated vulnerability of cancer cells to inhibition of poly(ADP-ribose)-polymerase (PARP)1 or the catalytic subunit of DNAdependent protein kinase (DNA-PKcs) in combination with IR suggesting a window for therapeutic opportunity [12]. Interestingly, SLC25A1i affected not only the DNA repair, but also reduced the abundance of cellular NAD-levels as well as of mitochondrial function [12].…”

“…Furthermore, targeting SLC25A1 indicated vulnerability of cancer cells to inhibition of poly(ADP-ribose)-polymerase (PARP)1 or the catalytic subunit of DNAdependent protein kinase (DNA-PKcs) in combination with IR suggesting a window for therapeutic opportunity [12]. Interestingly, SLC25A1i affected not only the DNA repair, but also reduced the abundance of cellular NAD-levels as well as of mitochondrial function [12].…”