Murali Krishna Cherukuri

Detecting response of rat C6 glioma tumors to radiotherapy using hyperpolarized [1-13C]pyruvate and 13C magnetic resonance spectroscopic imaging

We show here that hyperpolarized [1‐13C]pyruvate can be used to detect treatment response in a glioma tumor model; a tumor type where detection of response with 18fluoro‐2‐deoxyglucose, using positron emission tomography, is limited by the high background signals from normal brain tissue. 13C chemical shift images acquired following intravenous injection of hyperpolarized [1‐13C]pyruvate into rats with implanted C6 gliomas showed significant labeling of lactate within the tumors but comparatively low levels in surrounding brain.Labeled pyruvate was observed at high levels in blood vessels above the brain and from other major vessels elsewhere but was detected at only low levels in tumor and brain.The ratio of hyperpolarized 13C label in tumor lactate compared to the maximum pyruvate signal in the blood vessels was decreased from 0.38 ± 0.16 to 0.23 ± 0.13, (a reduction of 34%) by 72 h following whole brain irradiation with 15 Gy. Magn Reson Med, 2011.

Nitroxide derivatives of non-steroidal anti-inflammatory drugs exert anti-inflammatory and superoxide dismutase scavenging properties in A459 cells

Inflammation and reactive oxygen species are associated with the promotion of various cancers. The use of non‐steroidal anti‐inflammatory drugs (NSAIDs) in cancer prevention treatments has been promising in numerous cancers. We report the evaluation of NSAIDs chemically modified by the addition of a redox‐active nitroxide group. TEMPO‐aspirin (TEMPO‐ASA) and TEMPO‐indomethacin (TEMPO‐IND) were synthesized and evaluated in the lung cancer cell line A549.

Oral administration of the nitroxide radical TEMPOL exhibits immunomodulatory and therapeutic properties in multiple sclerosis models

Therapies with both immunomodulatory and neuroprotective properties are thought to have the greatest promise in reducing the severity and progression of multiple sclerosis (MS). Several reactive oxygen (ROS) and reactive nitrogen species (RNS) are implicated in inflammatory-mediated damage to the central nervous system (CNS) in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) is a stable nitroxide radical with potent antioxidant activity. The goal of our studies was to investigate the immunomodulatory effects and therapeutic potential of orally-delivered TEMPOL in the mouse EAE model. Mice receiving TEMPOL chow ad libitum for 2weeks prior to induction of active EAE showed delayed onset and reduced incidence of disease compared to control-fed animals. Reduced disease severity was associated with limited microglial activation and fewer inflammatory infiltrates. TEMPOLs effects were immunomodulatory, not immunosuppressive: T cells produced less interferon-γ and tumor necrosis factor-α, and TEMPOL-fed mice exhibited a shift towards TH2-type antibody responses. Both myeloid and myeloid-dendritic cells of TEMPOL-fed EAE animals had significantly lower levels of MHC class II expression than controls; CD40 was also significantly reduced. TEMPOL administration was associated with an enrichment of CD8+ T cell populations and CD4+FoxP3+ regulatory populations. TEMPOL reduced the severity of clinical disease when administered after the induction of disease, and also after the onset of clinical symptoms. To exclude effects on T cell priming in vivo, TEMPOL was tested with the passive transfer of encephalitogenic T cells and was found to reduce the incidence and peak severity of disease. Protection was associated with reduced infiltrates and a relative sparing of neurofilaments and axons. The ability of oral TEMPOL to reduce inflammation and axonal damage and loss demonstrate both anti-inflammatory and protective properties, with significant promise for the treatment of MS and related neurological disorders.

Reconstruction of electron paramagnetic resonance images using iterative methods

Electron Paramagnetic Resonance (EPR) allows for the non-invasive imaging of free radicals in biological systems. Although a number of physical factors have hindered the development of EPR as an imaging modality, EPR offers the potential for tissue oxymetry. EPR images are typically reconstructed using a traditional filtered back-projection technique. We are attempting to improve the quality of EPR images by using maximum-entropy based iterative image reconstruction algorithms. Our investigation has so far focused on two methods, the multiplicative algebraic reconstruction technique (MART), and an algorithm that is motivated by interior-point reconstruction. MART is a row-action method that maintains strict equality in the constraints while minimizing the entropy functional. The latter method, which we have named Least-Squares Barrier Entropy (LSBEnt), transforms the constrained problem into an unconstrained problem and maximizes entropy at a prescribed distance from the measured data. EPR studies are frequently characterized by low signal-to-noise ratios and wide line widths. The effect of the backprojection streaking artifact can be quite severe and can seriously compromise a study. We have compared the iterative results with filtered backprojection on two-dimensional (2-D) EPR acquisitions of various phantoms. Encouraging preliminary results have demonstrated that one of the clear advantages of the iterative methods is their lack of streaking artifacts that plague filtered backprojection.

Abstract 2852: Monitoring the impact on metabolic flux in vivo of a newly developed LDH inhibitor using hyperpolarized 13C magnetic resonance spectroscopic imaging

[aim] Increased lactate production is a feature of many neoplasms, and Lactate Dehydrogenase A (LDH-A) plays a key role in conversion of pyruvate to lactate. LDHA inhibition, therefore, is considered to be a promising approach toward developing a new therapeutic strategy for cancer treatment focused on targeting cancer metabolism. Non-invasive imaging approaches able to monitor metabolic fluxes in vivo will be useful for this purpose. Hyperpolarized 13C Magnetic Resonance Imaging (MRI) has been well known as a valuable technology to investigate metabolic processes in tumor xenografts, allowing us to perform dynamic 13C-metabolic flux analysis in vivo. Use of [1-13C]pyruvate with this technology provides the ability to monitor LDHA activity in real time through dynamic observation of conversion of [1-13C]pyruvate to [1-13C]lactate. This study aimed to monitor drug efficacy of a newly developed LDH inhibitor (LDHI, obtained from National Cancer Institute Experimental Therapeutics Program, NExT) in a xenograft tumor model using 13C MRI technology with hyperpolarized 13C-labeled pyruvate. [Results] Hyperpolarized [1-13C]pyruvate MR studies were performed before and after LDHI administration to assess the impact on metabolic flux in vivo. Using hyperpolarized [1-13C]pyruvate MR Spectroscopy (MRS), we found that lactate production was significantly suppressed by LDHI administration in MiaPaca (a glycolytic pancreatic cancer cell line) tumors, as was the [1-13C]lactate to [1-13C]pyruvate ratio ([1-13C]-Lac/Pyr), which was calculated from the areas under the curves (AUC) using time-intensity data. This ratio decreased from 1.08 to 0.128 (88.1% decrease) 30 minutes after intravenous administration of the LDHI. In addition, hyperpolarized [1-13C]pyruvate MRS revealed that LDHI significantly suppressed lactate production in a dose dependent manner. Furthermore, Chemical Shift Imaging with 13C MRI demonstrated that the [1-13C]lactate signal in each voxel clearly decreased, compared to that before LDHI administration. The sum of [1-13C]lactate signals in the tumor region decreased after LDHI administration, resulting in a significant decrease in the tumor-specific [1-13C] Lac/Pyr ratio (1.463±0.31 before LDHI to 0.134±0.036 30 minutes after LDHI administration, a 90.67±2.56% decrease, n=3, p [Conclusions] These results indicate that hyperpolarized 13C-MRI is a useful method to evaluate on-target efficacy of novel LDH inhibitors in vivo, and this technique can be used to determine optimum dose and exposure time of the LDHI in the tumor region. The current method can be of great value in providing an in vivo pharmacodynamic biomarker for this novel anti-cancer therapeutic targeting deregulated tumor metabolism. Citation Format: Nobu Oshima, Shun Kishimoto, Kristin Beebe, Keita Saito, Kazutoshi Yamamoto, Jeffery Brender, Anastasia Sowers, Ganesha Rai, Bryan T. Mott, David J. Maloney, James B. Mitchell, Murali K. Cherukuri, Leonard M. Neckers. Monitoring the impact on metabolic flux in vivo of a newly developed LDH inhibitor using hyperpolarized 13C magnetic resonance spectroscopic imaging [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2852. doi:10.1158/1538-7445.AM2017-2852