2-Hydroxyglutarate (2HG) exists as two enantiomers, (R)-2HG and (S)-2HG, and both are implicated in tumor progression via their inhibitory effects on α-ketoglutarate (αKG)-dependent dioxygenases. The former is an oncometabolite that is induced by the neomorphic activity conferred by isocitrate dehydrogenase-1 and -2 (IDH1/2) mutations, whereas the latter is produced under pathologic processes such as hypoxia. Here, we report that IDH1/2 mutations induce a homologous recombination (HR) defect that renders tumor cells exquisitely sensitive to poly (ADP-ribose) polymerase (PARP) inhibitors. This “BRCAness” phenotype of IDH mutant cells can be completely reversed by treatment with small molecule inhibitors of the mutant IDH1 enzyme, and, conversely, it can be entirely recapitulated by treatment with either 2HG enantiomer alone in cells with intact IDH1/2 proteins. We demonstrate IDH1-dependent PARP inhibitor sensitivity in a range of clinically relevant models, including primary patient-derived glioma cells in culture and genetically matched tumor xenografts in vivo. These findings provide the basis for a possible therapeutic strategy exploiting the biological consequences of mutant IDH, rather than attempting to block 2HG production, by targeting the 2HG-dependent HR-deficiency with PARP inhibition. Furthermore, our results uncover an unexpected link between oncometabolites, altered DNA repair, and genetic instability.

SUMMARY DNA double-strand break (DSB) repair by homologous recombination (HR) is initiated by CtIP/MRN-mediated DNA end resection to maintain genome integrity. SAMHD1 is a dNTP triphosphohydrolase, which restricts HIV-1 infection, and mutations are associated with Aicardi-Goutières syndrome and cancer. We show that SAMHD1 has a dNTPase-independent function in promoting DNA end resection to facilitate DSB repair by HR. SAMHD1 deficiency or Vpx-mediated degradation causes hypersensitivity to DSB-inducing agents, and SAMHD1 is recruited to DSBs. SAMHD1 complexes with CtIP via a conserved carboxyl-terminal domain and recruits CtIP to DSBs to facilitate end resection and HR. Significantly, a cancer-associated mutant with impaired CtIP interaction but not dNTPase-inactive SAMHD1 fails to rescue the end resection impairment of SAMHD1 depletion. Our findings define a dNTPase-independent function for SAMHD1 in HR-mediated DSB repair by facilitating CtIP accrual to promote DNA end resection, providing insight into how SAMHD1 promotes genome integrity and prevents disease, including cancer.

1. This study was conducted on 467 cases of non-insulin-dependent diabetes mellitus and 180 healthy controls. Lipid peroxidation products in plasma and erythrocytes were assayed as thiobarbituric acid reactive substances, along with the erythrocyte antioxidant enzymes, namely superoxide dismutase, catalase and glutathione peroxidase. In addition, scavenger vitamins A, C and E and reduced glutathione levels in blood were also measured. 2. Lipid peroxidation was significantly raised within the first 2 years of diagnosis, and superoxide dismutase, catalase, reduced glutathione and vitamins C and E were significantly lowered. 3. These changes were correlated with the duration of the disease and were of a higher magnitude with the development of complications. 4. The results suggest that the antioxidant deficiency and excessive peroxide-mediated damage may appear early on in non-insulin-dependent diabetes mellitus, before the development of secondary complications.

Key Points• Broad immune activation after a combination of lenalidomide and a-GalCer-loaded dendritic cells.• Proof of principle for harnessing NK T cells to prevent cancer in humans. Natural killer T (iNKT) cells can help IntroductionNatural killer T (NKT) cells are distinct innate CD1d-restricted T cells that recognize lipid antigens. 1 The best-studied subset of NKT cells in both mice and humans are type I NKT cells that express an invariant T-cell receptor. Several studies have described potent antitumor properties of iNKT cells in preclinical models and iNKT cells have also been implicated in immune surveillance against both spontaneous as well as carcinogeninduced murine tumors. 2,3 While iNKT cells can mediate lysis of tumor cells, their antitumor effects likely depend in large part on their ability to activate other immune cells such as NK and dendritic cells (DCs) and recruit adaptive immunity as well as mediate antiangiogenesis. 4-6 ␣-galactosylceramide (␣-GalCer) is a potent prototypic ligand for both human and murine iNKT cells. 7 The availability of clinical-grade ␣-GalCer (KRN7000; KHK) allowed testing of iNKT-targeted approaches in humans. 8 Initial studies with injection of soluble KRN7000 led to only modest effects in humans. [9][10][11] Preclinical studies suggested that targeting ␣-GalCer to DCs led to superior activation of NKT cells in vivo. 12 In a prior study, we have shown that the injection of ␣-GalCer-loaded human DCs led to a clear increase in circulating iNKT cells in vivo. 13 However, these cells were still functionally deficient and, importantly, little activation of downstream innate immune function (including NK cells) was observed.It is now clear that nearly all cases of clinical myeloma (MM) are preceded by an asymptomatic precursor state, including a phase termed as asymptomatic multiple myeloma (AMM). 14 Patients with AMM are currently observed but carry high risk for progression to clinical MM requiring therapy. Strategies to prevent clinical MM may therefore have a major impact on disease-related morbidity and mortality. 14 In prior studies, we have shown that progression from precursor to clinical MM is associated with progressive dysfunction of iNKT cells in vivo. 15 Myeloma is an attractive tumor for NKT-targeted approaches because tumor cells commonly express CD1d and are sensitive to lysis by both NKT as well as NK cells. 15,16 In the past decade, incorporation of immunomodulatory drugs such as lenalidomide (LEN) into clinical care has improved outcome in human MM. 17 An important property of these drugs is providing costimulation of both human T cells as well as NKT cells in culture in an antigen-dependent manner. 18-20 Therefore, we hypothesized that the combination of LEN with ␣-GalCer-loaded DCs will lead to synergistic activation of innate lymphocytes in vivo and mediate antitumor effects in the preventive setting. As LEN alone has some single-agent activity in MM, 21 we chose to test a LEN dose of 10 mg/d, which is lower than the usual starting dose (25 mg/d) in ...

The hereditary cancer syndromes hereditary leiomyomatosis and renal cell cancer (HLRCC) and succinate dehydrogenase-related hereditary paraganglioma and pheochromocytoma (SDH PGL/PCC) are linked to germline loss-of-function mutations in genes encoding the Krebs cycle enzymes fumarate hydratase and succinate dehydrogenase, thus leading to elevated levels of fumarate and succinate, respectively. Here, we report that fumarate and succinate both suppress the homologous recombination (HR) DNA-repair pathway required for the resolution of DNA double-strand breaks (DSBs) and for the maintenance of genomic integrity, thus rendering tumor cells vulnerable to synthetic-lethal targeting with poly(ADP)-ribose polymerase (PARP) inhibitors. These results identify HLRCC and SDH PGL/PCC as familial DNA-repair deficiency syndromes, providing a mechanistic basis to explain their cancer predisposition and suggesting a potentially therapeutic approach for advanced HLRCC and SDH PGL/PCC, both of which are incurable when metastatic.

Key Points Prospective analysis of antigen-specific B/T-cell immunity in natural history of human premalignancy. Stemness antigens and ICPs may be targets for cancer prevention.

Approximately half of glioblastoma and more than two-thirds of grade II and III glioma tumors lack the DNA repair protein O 6 -methylguanine methyl transferase (MGMT). MGMT-deficient tumors respond initially to the DNA methylation agent temozolomide (TMZ) but frequently acquire resistance through loss of the mismatch repair (MMR) pathway. We report the development of agents that overcome this resistance mechanism by inducing MMR-independent cell killing selectively in MGMT-silenced tumors. These agents deposit a dynamic DNA lesion that can be reversed by MGMT but slowly evolves into an interstrand cross-link in MGMT-deficient settings, resulting in MMR-independent cell death with low toxicity in vitro and in vivo. This discovery may lead to new treatments for gliomas and may represent a new paradigm for designing chemotherapeutics that exploit specific DNA repair defects.

Insect-borne diseases have experienced a troubling resurgence in recent years. Emergence of resistance to pesticides greatly hampers control efforts. Paratransgenesis, or the genetic transformation of bacterial symbionts of disease vectors, is an alternative to traditional approaches. Previously, we developed paratransgenic lines of Rhodnius prolixus, a vector of Chagas disease in Central America. Here, we report identification of a Corynebacterial species as a symbiont of Triatoma infestans, a leading vector of Chagas disease in South America. We have modified this bacterium to produce an immunologically active single chain antibody fragment, termed rDB3. This study establishes the basis for generating paratransgenic T. infestans as a strategy for control of Chagas disease.