The Alkylating Chemotherapeutic Temozolomide Induces Metabolic Stress in IDH1-Mutant Cancers and Potentiates NAD+ Depletion–Mediated Cytotoxicity

Abstract

IDH1 -mutant gliomas are dependent upon the canonical coenzyme nicotinamide adenine dinucleotide (NAD+) for survival. It is known that Poly(ADP-ribose) polymerase (PARP) activation consumes NAD+ during base excision repair (BER) of chemotherapy-induced DNA damage. We therefore hypothesized that a strategy combining NAD+ biosynthesis inhibitors with the alkylating chemotherapeutic agent temozolomide (TMZ) could potentiate NAD+ depletion-mediated cytotoxicity in mutant IDH1 cancer cells. To investigate the impact of TMZ on NAD+ metabolism, patient-derived xenografts and engineered mutant IDH1-expressing cell lines were exposed to TMZ, in vitro and in vivo, both alone and in combination with nicotinamide phosphoribosyltransferase (NAMPT) inhibitors, which block NAD+ biosynthesis. The acute time-period (<3 hrs) after TMZ treatment displayed a burst of NAD+ consumption driven by PARP activation. In IDH1 mutant-expressing cells, this consumption reduced further the abnormally-lowered basal steady-state levels of NAD+, introducing a window of hyper-vulnerability to NAD+ biosynthesis inhibitors. This effect was selective for IDH1-mutant cells and independent of methylguanine methyltransferase (MGMT) or mismatch repair (MMR) status, which are known rate-limiting mediators of adjuvant TMZ genotoxic sensitivity. Combined TMZ and NAMPT inhibition in an in vivo IDH1-mutant cancer model exhibited enhanced efficacy compared to each agent alone. Thus, we find IDH1-mutant cancers have distinct metabolic stress responses to chemotherapy-induced DNA damage and that combination regimens targeting non-redundant NAD+ pathways yield potent anti-cancer efficacy in vivo. Such targeting of convergent metabolic pathways in genetically-selected cancers could minimize treatment toxicity and improve durability of response to therapy.

Inhibition of PARP Sensitizes Chondrosarcoma Cell Lines to Chemo- and Radiotherapy Irrespective of the IDH1 or IDH2 Mutation Status

“…We did not identify a similar association in a panel of human chondrosarcoma cell lines. Likewise, the synthetic lethal interaction between temozolomide and IDH mutations described in gliomas was not observed in our study [35,36]. Our research group published that the reported synthetic lethal interaction between IDH mutations and Bcl-2, NAMPT, and glutaminase inhibition was absent in chondrosarcoma [11,[37][38][39].…”

Beyond Energy Metabolism: Exploiting the Additional Roles of NAMPT for Cancer Therapy

“…In addition to developing rational combination regimens using NAMPT inhibitors, careful patient selection represents an additional opportunity to maximize the efficacy of these agents. For example, IDH mutant cancers have been shown to have exquisite sensitivity to NAMPT inhibitors (63)(64)(65), as have tumors deficient in NAPRT (9,(145)(146)(147)(148)(149)(150)(151). Patient selection may also be guided by recognition of specific vulnerabilities in the non-metabolic pathways supported by NAMPT, such as HR-deficiency or EMT targeting for metastatic disease.…”

“…Given these insights, a number of studies have sought to determine the efficacy of NAMPT inhibitors when combined with DNA damaging agents. Enhanced antitumor activity has been reported across multiple malignancies when genetic or pharmacological inhibition of NAMPT has been combined with radiation (101), DNA alkylating agents (63,99,100,102,103), topoisomerase inhibitors (19,46,86), or other classes of chemotherapy known to augment the effects of impaired DNA repair (19,20,43,46,(104)(105)(106). Surprisingly, in some cancers, an improvement in efficacy was restricted to combinations with only certain chemotherapeutic agents, as in preclinical studies in pancreatic cancer models which revealed that gemcitabine, but not 5-fluorouracil (5-FU) or oxaliplatin, enhanced the antiproliferative effect of NAMPT inhibitors (107).…”

“…In cancer cells, NAMPT inhibitors affect glycolysis (40, 45-55), oxidative phosphorylation (45, 49, 53, 56-59), serine biosynthesis and one-carbon metabolism (60), the pentose phosphate pathway (40, 53, 61), amino acid metabolism (53), purine and pyrimidine metabolism (53), and fatty acid and lipid synthesis (45, 62). In addition, cancer types harboring mutations in metabolic pathways, such as isocitrate dehydrogenase (IDH), have been shown to be exquisitely sensitive to loss of NAMPT activity (63)(64)(65).…”

MGMT Expression Contributes to Temozolomide Resistance in H3K27M-Mutant Diffuse Midline Gliomas

“…The first two usually do not induce cytotoxicity, because poly (ADP-ribose) polymerase (PARP) activation allows for base excision repair of damaged DNA. Inhibition of PARP or depletion of NAD + , which is a co-enzyme of PARP, leads to cell death (3,44). A previous study has shown PARP1 expression in DIPG cell lines (45).…”