Deoxyuridine-rich cytoplasmic DNA antagonizes STING-dependent innate immune responses and sensitizes resistant tumors to anti-PD-L1 therapy.

DNA damage and cytoplasmic DNA induce type-1 interferon (IFN-1) and potentiate responses to immune checkpoint inhibitors. Our prior work found that inhibitors of the DNA damage response kinase ATR (ATRi) induce IFN-1 and deoxyuridine (dU) incorporation by DNA polymerases, akin to antimetabolites. Whether and how dU incorporation is required for ATRi-induced IFN-1 signaling is not known. Here, we show that ATRi-dependent IFN-1 responses require uracil DNA glycosylase (UNG)-initiated base excision repair and STING. Quantitative analyses of nine distinct nucleosides reveals that ATRi induce dU incorporation more rapidly in UNG wild-type than knockout cells, and that induction of IFN-1 is associated with futile cycles of repair. While ATRi induce similar numbers of micronuclei in UNG wild-type and knockout cells, dU containing micronuclei and cytoplasmic DNA are increased in knockout cells. Surprisingly, DNA fragments containing dU block STING-dependent induction of IFN-1, MHC-1, and PD-L1. Furthermore, UNG knockout sensitizes cells to IFN-γ in vitro , and potentiates responses to anti-PD-L1 in resistant tumors in vivo . These data demonstrate an unexpected and specific role for dU-rich DNA in suppressing STING-dependent IFN-1 responses, and show that UNG-deficient tumors have a heightened response to immune checkpoint inhibitors. STATEMENT OF SIGNIFICANCE: Antimetabolites disrupt nucleotide pools and increase dU incorporation by DNA polymerases. We show that unrepaired dU potentiates responses to checkpoint inhibitors in mouse models of cancer. Patients with low tumor UNG may respond to antimetabolites combined with checkpoint inhibitors, and patients with high tumor UNG may respond to UNG inhibitors combined with checkpoint inhibitors.

Quantitation of Cabozantinib in Human Plasma by LC-MS/MS.

To support a phase III randomized trial of the multi-targeted tyrosine kinase inhibitor cabozantinib in neuroendocrine tumors, we developed a high-performance liquid chromatography mass spectrometry method to quantitate cabozantinib in 50 µL of human plasma. After acetonitrile protein precipitation, chromatographic separation was achieved with a Phenomenex synergy polar reverse phase (4 µm, 2 × 50 mm) column and a gradient of 0.1% formic acid in acetonitrile and 0.1% formic acid in water over a 5-min run time. Detection was performed on a Quattromicro quadrupole mass spectrometer with electrospray, positive-mode ionization. The assay was linear over the concentration range 50-5000 ng/mL and proved to be accurate (103.4-105.4%) and precise (<5.0%CV). Hemolysis (10% RBC) and use of heparin as anticoagulant did not impact quantitation. Recovery from plasma varied between 103.0-107.7% and matrix effect was -47.5 to -41.3%. Plasma freeze-thaw stability (97.7-104.9%), stability for 3 months at -80°C (103.4-111.4%), and stability for 4 h at room temperature (100.1-104.9%) were all acceptable. Incurred sample reanalysis of (N = 64) passed: 100% samples within 20% difference, -0.7% median difference and 1.1% median absolute difference. External validation showed a bias of less than 1.1%. This assay will help further define the clinical pharmacokinetics of cabozantinib.

In vitro evaluation of the metabolic enzymes and drug interaction potential of triapine.

PURPOSE: To investigate the metabolic pathways of triapine in primary cultures of human hepatocytes and human hepatic subcellular fractions; to investigate interactions of triapine with tenofovir and emtricitabine; and to evaluate triapine as a perpetrator of drug interactions. The results will better inform future clinical studies of triapine, a radiation sensitizer currently being studied in a phase III study. METHODS: Triapine was incubated with human hepatocytes and subcellular fractions in the presence of a number of inhibitors of drug metabolizing enzymes. Triapine depletion was monitored by LC-MS/MS. Tenofovir and emtricitabine were co-incubated with triapine in primary cultures of human hepatocytes. Triapine was incubated with a CYP probe cocktail and human liver microsomes, followed by LC-MS/MS monitoring of CYP specific metabolite formation. RESULTS: Triapine was not metabolized by FMO, AO/XO, MAO-A/B, or NAT-1/2, but was metabolized by CYP450s. CYP1A2 accounted for most of the depletion of triapine. Tenofovir and emtricitabine did not alter triapine depletion. Triapine reduced CYP1A2 activity and increased CYP2C19 activity. CONCLUSION: CYP1A2 metabolism is the major metabolic pathway for triapine. Triapine may be evaluated in cancer patients in the setting of HIV with emtricitabine or tenofovir treatment. Confirmatory clinical trials may further define the in vivo triapine metabolic fate and quantify any drug-drug interactions.

Psychosocial and behavioral pathways of metabolic syndrome in cancer caregivers.

OBJECTIVE: Cancer caregivers are at increased risk for cardiovascular disease (CVD) and mortality. The aims of this study were to examine psychosocial and behavioral predictors of metabolic syndrome, an intermediate endpoint of CVD. METHODS: Cancer caregivers were administered a battery of questionnaires assessing sociodemographic characteristics, depressive symptoms, perceived stress, caregiver quality of life, sleep, physical activity, alcohol and tobacco use, social support, relationship quality, and loneliness. Metabolic syndrome was defined using the American Heart Association guidelines and the National Cholesterol Education Program's Adult Treatment Panel (ATP) III, which includes the presence of at least three of the following abnormalities: blood pressure, glucose, abdominal girth, high-density lipoprotein (HDL), and triglycerides. RESULTS: Of the 104 caregivers, 77% were female, 94% were Caucasian, and the mean age was 59.5 (SD = 12.8). Of the 104 caregivers, 35.6% reported depressive symptoms in the clinical range of the Center for Epidemiologic Studies-Depression (CES-D) and 69.2% reported Perceived Stress Scale scores at least one standard deviation above the general population norms. A total of 16.3% of caregivers currently used tobacco, 28.8% consumed alcohol, and 26.7% were overweight (BMI = 25-29.9) and 48.5% were obese (BMI ≥ 30). Forty-nine percent of the caregivers met the criteria for metabolic syndrome. After age, gender, and race were adjusted, the following remained as significant predictors of metabolic syndrome: low levels of caregiver quality of life (Odds Ratio (OR) = 1.067; 95% CI, 1.019-1.117; P = .006), high levels of hostility (OR = 1.142; 95% CI, 1.030-1.267; P = .012), and current alcohol use (OR = 4.193; 95% CI, 1.174-14.978; P = .027). CONCLUSION: Development of interventions to reduce the risk of metabolic syndrome in cancer caregivers is recommended.