Browsing by Subject "Mammalian target of rapamycin (mTOR)"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    A carbon-11 labeled imidazo[1,2- a]pyridine derivative as a new potential PET probe targeting PI3K/mTOR in cancer
    (e-Century Publishing, 2023-06-25) Liu, Wenqing; Ma, Wenjie; Wang, Min; Wang, Zhuangzhuang; Grega, Shaun D.; Zheng, Qi-Huang; Xu, Zhidong; Radiology and Imaging Sciences, School of Medicine
    The PI3K/Akt/mTOR pathway is frequently dysregulated in cancer due to its central role in cell growth, survival, and proliferation. Overactivation of the PI3K/Akt/mTOR pathway may occur through varying mechanisms including mutations, gene amplification, and upstream signaling events, ultimately resulting in cancer. Therefore, PI3K/Akt/mTOR pathway has emerged as an attractive target for cancer therapy and imaging. A promising approach to inhibit this pathway involves a simultaneous inhibition of both PI3K and mTOR using a dual inhibitor. Recently, a potent dual PI3K/mTOR inhibitor, 2,4-difluoro-N-(2-methoxy-5-(3-(5-(2-(4-methylpiperazin-1-yl)ethyl)-1,3,4-oxadiazol-2-yl)imidazo[1,2-a]pyridin-6-yl)pyridin-3-yl)benzenesulfonamide (7), was discovered and demonstrated excellent kinase selectivity IC50 (PI3K/mTOR) = 0.20/21 nM; good cellular growth inhibition IC50 (HCT-116 cell) = 10 nM, modest plasma clearance, and acceptable oral bioavailability. Expanding on this discovery, here we present the synthesis of the carbon-11 labeled imidazo[1,2-a]pyridine derivative 2,4-difluoro-N-(2-methoxy-5-(3-(5-(2-(4-[11C]methylpiperazin-1-yl)ethyl)-1,3,4-oxadiazol-2-yl)imidazo[1,2-a]pyridin-6-yl)pyridin-3-yl)benzenesulfonamide (N-[11C]7) as a new potential radiotracer for the biomedical imaging technique positron emission tomography (PET) imaging of PI3K/mTOR in cancer. The reference standard 7 and its N-demethylated precursor, 2,4-difluoro-N-(2-methoxy-5-(3-(5-(2-(piperazin-1-yl)ethyl)-1,3,4-oxadiazol-2-yl)imidazo[1,2-a]pyridin-6-yl)pyridin-3-yl)benzenesulfonamide (11), were synthesized in 7 and 8 steps with 10% and 7% overall chemical yield, respectively. N-[11C]7 was prepared from 11 using [11C]methyl triflate ([11C]CH3OTf) through N-11C-methylation and isolated by high-performance liquid chromatography (HPLC) and solid-phase extraction (SPE) formulation in 40-50% radiochemical yield decay corrected to end of bombardment (EOB) based on [11C]CO2. The radiochemical purity was > 99% and the molar activity (Am) at EOB was in the range of 296-555 GBq/µmol (n = 5).
  • Thumbnail Image
    Item
    Obesity challenges the hepatoprotective function of the integrated stress response to asparaginase exposure in mice
    (American Society for Biochemistry and Molecular Biology, 2017-04-21) Nikonorova, Inna A.; Al-Baghdadi, Rana J. T.; Mirek, Emily T.; Wang, Yongping; Goudie, Michael P.; Wetstein, Berish B.; Dixon, Joseph L.; Hine, Christopher; Mitchell, James R.; Adams, Christopher M.; Wek, Ronald C.; Anthony, Tracy G.; Biochemistry and Molecular Biology, School of Medicine
    Obesity increases risk for liver toxicity by the anti-leukemic agent asparaginase, but the mechanism is unknown. Asparaginase activates the integrated stress response (ISR) via sensing amino acid depletion by the eukaryotic initiation factor 2 (eIF2) kinase GCN2. The goal of this work was to discern the impact of obesity, alone versus alongside genetic disruption of the ISR, on mechanisms of liver protection during chronic asparaginase exposure in mice. Following diet-induced obesity, biochemical analysis of livers revealed that asparaginase provoked hepatic steatosis that coincided with activation of another eIF2 kinase PKR-like endoplasmic reticulum kinase (PERK), a major ISR transducer to ER stress. Genetic loss of Gcn2 intensified hepatic PERK activation to asparaginase, yet surprisingly, mRNA levels of key ISR gene targets such as Atf5 and Trib3 failed to increase. Instead, mechanistic target of rapamycin complex 1 (mTORC1) signal transduction was unleashed, and this coincided with liver dysfunction reflected by a failure to maintain hydrogen sulfide production or apolipoprotein B100 (ApoB100) expression. In contrast, obese mice lacking hepatic activating transcription factor 4 (Atf4) showed an exaggerated ISR and greater loss of endogenous hydrogen sulfide but normal inhibition of mTORC1 and maintenance of ApoB100 during asparaginase exposure. In both genetic mouse models, expression and phosphorylation of Sestrin2, an ATF4 gene target, was increased by asparaginase, suggesting mTORC1 inhibition during asparaginase exposure is not driven via eIF2-ATF4-Sestrin2. In conclusion, obesity promotes a maladaptive ISR during asparaginase exposure. GCN2 functions to repress mTORC1 activity and maintain ApoB100 protein levels independently of Atf4 expression, whereas hydrogen sulfide production is promoted via GCN2-ATF4 pathway.