Nallathamby Devasahayam - Academia.edu (original) (raw)

Papers by Nallathamby Devasahayam

PEGPH20 is a PEGylated form of recombinant human hyaluronidase PH20. The purpose of this study is... more PEGPH20 is a PEGylated form of recombinant human hyaluronidase PH20. The purpose of this study is to investigate physiologic changes in pancreatic adenocarcinoma xenograft after PEGPH20 treatment using multi-modal imaging and further determine the utility of PEGPH20 as radiosensitizer. PEGPH20 treatment significantly increased intratumor pO2, blood perfusion and volume, and decreased glycolytic flux assessed by EPR, MRI with USPIO or Gd, and 13C DNP MRI, respectively. PEGPH20 enhanced treatment effect of radiotherapy. The results validated the utility of the imaging methods to monitor the changes in the tumor microenvironment after hyaluronan depletion and to predict the radio-sensitizing effect of PEGPH20.

Molecular imaging approaches for metabolic and physiologic imaging of tumors have become importan... more Molecular imaging approaches for metabolic and physiologic imaging of tumors have become important for treatment planning and response monitoring. However, the relationship between the physiologic and metabolic aspects of tumors is not fully understood. Here, we developed new hyperpolarized MRI and electron paramagnetic resonance imaging procedures that allow more direct assessment of tumor glycolysis and oxygenation status quantitatively. We investigated the spatial relationship between hypoxia, glucose uptake, and glycolysis in three human pancreatic ductal adenocarcinoma tumor xenografts with differing physiologic and metabolic characteristics. At the bulk tumor level, there was a strong positive correlation between 18F-FDG-PET and lactate production, while pO2 was inversely related to lactate production and 18F-2-fluoro-2-deoxy-D-glucose (18F-FDG) uptake. However, metabolism was not uniform throughout the tumors, and the whole tumor results masked different localizations that became apparent while imaging. 18F-FDG uptake negatively correlated with pO2 in the center of the tumor and positively correlated with pO2 on the periphery. In contrast to pO2 and 18F-FDG uptake, lactate dehydrogenase activity was distributed relatively evenly throughout the tumor. The heterogeneity revealed by each measure suggests a multimodal molecular imaging approach can improve tumor characterization, potentially leading to better prognostics in cancer treatment.Significance:Novel multimodal molecular imaging techniques reveal the potential of three interrelated imaging biomarkers to profile the tumor microenvironment and interrelationships of hypoxia, glucose uptake, and glycolysis.

Tumors exhibit fluctuations in blood flow that influence oxygen concentrations and therapeutic re... more Tumors exhibit fluctuations in blood flow that influence oxygen concentrations and therapeutic resistance. To assist therapeutic planning and improve prognosis, noninvasive dynamic imaging of spatial and temporal variations in oxygen partial pressure (pO 2) would be useful. Here, we illustrate the use of pulsed electron paramagnetic resonance imaging (EPRI) as a novel imaging method to directly monitor fluctuations in oxygen concentrations in mouse models. A common resonator platform for both EPRI and magnetic resonance imaging (MRI) provided pO 2 maps with anatomic guidance and microvessel density. Oxygen images acquired every 3 minutes for a total of 30 minutes in two different tumor types revealed that fluctuation patterns in pO 2 are dependent on tumor size and tumor type. The magnitude of fluctuations in pO 2 in SCCVII tumors ranged between 2-to 18-fold, whereas the fluctuations in HT29 xenografts were of lower magnitude. Alternating breathing cycles with air or carbogen (95% O 2 plus 5% CO 2) distinguished higher and lower sensitivity regions, which responded to carbogen, corresponding to cycling hypoxia and chronic hypoxia, respectively. Immunohistochemical analysis suggests that the fluctuation in pO 2 correlated with pericyte density rather than vascular density in the tumor. This EPRI technique, combined with MRI, may offer a powerful clinical tool to noninvasively detect variable oxygenation in tumors. Cancer Res; 70(16); 6427-36. ©2010 AACR.

Supplementary Movie 1 from Low-Field Magnetic Resonance Imaging to Visualize Chronic and Cycling ... more Supplementary Movie 1 from Low-Field Magnetic Resonance Imaging to Visualize Chronic and Cycling Hypoxia in Tumor-Bearing Mice

Comparison of EPR images, MR images and histological images. To better understand the relationshi... more Comparison of EPR images, MR images and histological images. To better understand the relationship between tumor pO 2 , blood volume, blood perfusion and hypoxia, we compared five types of images: T 2-weighted anatomical MR images, oxymetric EPR images, blood volume MR images, H&E histology, and Hoechst33342 perfusion images combined with pimonidazole immuno-histochemistry in the same or adjacent tumor section (Supplemental Figure 1). These images distinguished two typical regions with different characteristics. T 2-weighted MRI showed heterogeneity within the tumor, i.e., a hyperintense core in region 1 and a hypointense core in region 2 (Figure S1A). In pO 2 maps derived from EPRI, ROI 1 was found to be well-oxygenated while ROI 2 displayed extremely hypoxic zones over a wide area (Figure S1B). Consistent with the pO 2 map, the MR image-based microvessel density map (Figure S1C) revealed that ROI 1 was better vascularized in comparison to ROI 2. The perfusion marker Hoechst33342 showed that ROI 1 was well perfused compared to ROI 2 (Figure S1D). In addition, in ROI 1, which was more highly perfused, there was less staining for the hypoxia marker pimonidazole (pimo), suggesting that this ROI had less hypoxia. In contrast, ROI 2 was found to contain DAPI-negative cells, which are necrotic cells in this region were also reporting as pimonidazole-negative.

Immunostaining of hypoxia marker pimonidazole of three pancreatic tumors. Representative pictures... more Immunostaining of hypoxia marker pimonidazole of three pancreatic tumors. Representative pictures of whole tumor area were shown.

Benefit of combination therapy over monotherapy.

Review of Scientific Instruments, Oct 25, 2002

A commercially available high-speed, digital signal-averager is integrated into an existing time-... more A commercially available high-speed, digital signal-averager is integrated into an existing time-domain radio frequency (rf) electron paramagnetic resonance (EPR) spectrometer/imager. Sensitivity enhancement by the integrated system is estimated by coherent averaging of free induction decay signals, obtained from narrow-line EPR spin probes, and its performance is compared with that of an existing custom-built averager. For the existing custom-built “Analytek” averager, the minimum realizable trigger rate was 50 kHz, whereas for the commercial EG&G 9826 system, due the spectrometer constraints, we set the retrigger rate to 133 kHz. Very short summing and down loading times of the latter enable good temporal resolution in phantom as well as in vivo rf Fourier transform EPR images, obtained by the single point imaging (SPI) modality. For two-dimensional and three-dimensional imaging using the SPI mode, a saving of time by a factor of >2 could be achieved with the EG&G system compared with the Analytek.

Colloids and Surfaces B: Biointerfaces, Nov 1, 2018

alginate as a versatile three-dimensional (3D) culturing system capable of generating areas of ox... more alginate as a versatile three-dimensional (3D) culturing system capable of generating areas of oxygen heterogeneity and modeling metabolic changes in vitro. Here, through dosimetry, clonogenic and viability assays, and pimonidazole staining, we demonstrate that alginate can model radiobiological responses that monolayer cultures do not simulate. Notably, alginate hydrogels with radii greater than 500 µm demonstrate hypoxic cores, while smaller hydrogels do not. The size of this hypoxic region correlates with hydrogel size and improved cell survival following radiation therapy. Hydrogels can also be utilized in hyperpolarized magnetic resonance spectroscopy and extracellular flux analysis. Alginate therefore offers a reproducible, consistent, and low-cost means for 3D culture of cancer cells for radiobiological studies that simulates important in vivo parameters such as regional hypoxia, as well as enables long-term culturing and in vitro metabolic studies.

Antioxidants & Redox Signaling, Sep 10, 2014

Aims: The tumor microenvironment is characterized by a highly reducing redox status, a low pH, an... more Aims: The tumor microenvironment is characterized by a highly reducing redox status, a low pH, and hypoxia. Anti-angiogenic therapies for solid tumors frequently function in two steps: the transient normalization of structurally and functionally aberrant tumor blood vessels with increased blood perfusion, followed by the pruning of tumor blood vessels and the resultant cessation of nutrients and oxygen delivery required for tumor growth. Conventional anatomic or vascular imaging is impractical or insufficient to distinguish between the two steps of tumor response to anti-angiogenic therapies. Here, we investigated whether the noninvasive imaging of the tumor redox state and energy metabolism could be used to characterize anti-angiogenic drug-induced transient vascular normalization. Results: Daily treatment of squamous cell carcinoma (SCCVII) tumor-bearing mice with the multityrosine kinase inhibitor sunitinib resulted in a rapid decrease in tumor microvessel density and the suppression of tumor growth. Tumor pO 2 imaging by electron paramagnetic resonance imaging showed a transient increase in tumor oxygenation after 2-4 days of sunitinib treatment, implying improved tumor perfusion. During this window of vascular normalization, magnetic resonance imaging of the redox status using an exogenously administered nitroxide probe and hyperpolarized 13 C MRI of the metabolic flux of pyruvate/lactate couple revealed an oxidative shift in tumor redox status. Innovation: Redox-sensitive metabolic couples can serve as noninvasive surrogate markers to identify the vascular normalization window in tumors with imaging techniques. Conclusion: A multimodal imaging approach to characterize physiological, metabolic, and redox changes in tumors is useful to distinguish between the different stages of anti-angiogenic treatment. Antioxid. Redox Signal. 21, 1145-1155.

Magnetic Resonance in Medicine, Jun 12, 2012

The hypoxic nature of tumors results in treatment resistance and poor prognosis. To spare limited... more The hypoxic nature of tumors results in treatment resistance and poor prognosis. To spare limited oxygen for more crucial pathways, hypoxic cancerous cells suppress mitochondrial oxidative phosphorylation and promote glycolysis for energy production. Thereby, inhibition of glycolysis has the potential to overcome treatment resistance of hypoxic tumors. Here, EPR imaging was used to evaluate oxygen dependent efficacy on hypoxia‐sensitive drug. The small molecule 3‐bromopyruvate blocks glycolysis pathway by inhibiting hypoxia inducible enzymes and enhanced cytotoxicity of 3‐bromopyruvate under hypoxic conditions has been reported in vitro. However, the efficacy of 3‐bromopyruvate was substantially attenuated in hypoxic tumor regions (pO2 < 10 mmHg) in vivo using squamous cell carcinoma (SCCVII)‐bearing mouse model. Metabolic MRI studies using hyperpolarized 13C‐labeled pyruvate showed that monocarboxylate transporter‐1 is the major transporter for pyruvate and the analog 3‐bromopyruvate in SCCVII tumor. The discrepant results between in vitro and in vivo data were attributed to biphasic oxygen dependent expression of monocarboxylate transporter‐1 in vivo. Expression of monocarboxylate transporter‐1 was enhanced in moderately hypoxic (8–15 mmHg) tumor regions but down regulated in severely hypoxic (<5 mmHg) tumor regions. These results emphasize the importance of noninvasive imaging biomarkers to confirm the action of hypoxia‐activated drugs. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.

bioRxiv (Cold Spring Harbor Laboratory), May 18, 2023

In this study, we compared two triarylmethyl (TAM) spin probes, Ox071 and Ox063 for their efficac... more In this study, we compared two triarylmethyl (TAM) spin probes, Ox071 and Ox063 for their efficacy in measuring tissue oxygen concentration by R2*-based oximetry in hypoxic and normoxic conditions. Methods: The R2* dependence with spin probe and oxygen was calibrated using standard phantom solutions at 1, 2, 5, 10 mM spin probe and 0, 2, 5, 10, 21% oxygen concentrations. For a hypoxic model, in vivo imaging of a MIA PaCa-2 tumor implanted in the hind leg of a mouse was performed on successive days by using either Ox071 or Ox063. For normoxic model, renal imaging of healthy athymic mice was performed under similar conditions. The 3D spin density images acquired under three different gradients and reconstructed by single point imaging modality were used for computing the R2 * values. Results: The signal intensities of Ox071 were about three times greater in the phantom solutions than Ox063 in the entire pO2 range investigated. Although histograms computed from the pO2 images of the tumor were skewed towards low pO2 levels for both spin probes due to R2* signal loss, more frequency counts in the normoxic region at pO2 > 32 mmHg could be detected with Ox071. In the normoxic model in kidney, the high pO2 cortex and the low pO2 medulla regions were well delineated. The histograms of high-resolution kidney oximetry images using Ox071 were nearly symmetrical and frequency counts were seen up to 55 mmHg which were missed in Ox063 imaging. Conclusion: This study illustrates Ox071 as a better oximetric probe than Ox063 in terms of sensitivity and the pO2 dynamic range.

Supplemental Data 1 Supplemental Methods Probes for EPRI and MRI Electron Paramagnetic Resonance ... more Supplemental Data 1 Supplemental Methods Probes for EPRI and MRI Electron Paramagnetic Resonance (EPR) oxygen imaging uses an oxygen-sensitive triarylmethyl radical (TAM) probe OX63 (Suppl. Methods Fig.1), which was obtained from GE Healthcare (London, UK). OX63 is derivatized extensively to confer optimal chemical, pharmacological, and EPR characteristics such as stability, water solubility, low toxicity, long in vivo half-lives, single narrow line resonance, and pO 2-dependent EPR line widths (1). The dose of OX63 used for imaging (1.125 mmol/kg) was well below the maximally tolerated dose of 2.5-7.0 mmol/kg and the LD 50 of 8.0 mmol/kg (2). The pharmacologic half-life of OX63 in kidney and blood is

Complete and detailed descriptions of materials and methods are in the supplementary information,... more Complete and detailed descriptions of materials and methods are in the supplementary information, including animal studies, image registration, hyperpolarized 13C MRI, 18F-FDG PET, EPR imaging, Western blot, Immunohistochemistry, and statistical analysis. A supplementary Figure S contains H&E and CD31 staining of 100 μm thick slices from the center of the xenograft tumors to depict differences in vascularity are not the primer driver for the rim/interior difference in FDG uptake and O2 levels.

Supplementary Movie 2 from Low-Field Magnetic Resonance Imaging to Visualize Chronic and Cycling ... more Supplementary Movie 2 from Low-Field Magnetic Resonance Imaging to Visualize Chronic and Cycling Hypoxia in Tumor-Bearing Mice

Antioxidants & Redox Signaling, May 23, 2023

Aims: Pancreatic ductal adenocarcinomas (PDACs) form hypovascular and hypoxic tumors which are di... more Aims: Pancreatic ductal adenocarcinomas (PDACs) form hypovascular and hypoxic tumors which are difficult to treat with current chemotherapy regimens. Gemcitabine (GEM) is often used as a first line treatment for PDACs, but has issues with chemoresistance and penetration in the interior of the tumor. Evofosfamide, a hypoxia activated prodrug, has been shown to be effective in combination with GEM, although the mechanism of each drug on the other has not been established. We used two mouse xenografts from two cell lines (MIA Paca-2 and SU 86.86) with different tumor microenvironmental characteristics to probe the action of each drug on the other. Results: GEM treatment enhanced survival times in mice with SU.86.86 xenografts (HR =0.35, 95% CI=0.13 to 0.90 p=0.03) but had no effect on MIA Paca-2 mice (HR =0.91, 95% CI=0.37 to 2.25, p=0.84). Conversely, evofosfamide had no effect on SU86.86 mice and did not improve survival times to a statistically significant degree (HR=0.57, 95% CI=0.23 to 1.42, p=0.22). In MIA Paca-2 tumors, which were initially poorly perfused, electron paramagnetic resonance (EPR) imaging showed that oxygenation worsened when treated with GEM, providing a direct mechanism for the activation of evofosfamide by GEM and the effectiveness of evofosfamide and GEM combinations. Sublethal amounts of either treatment enhanced the toxicity of other treatment in vitro in Su86.86 but not in MIAPaca-2. Repair of double stranded DNA lesions was enhanced in the combination treatment in Su86.86 but not MIA Paca-2. Innovations: A possible mechanism for the synergy between evofosfamide and GEM has been proposed. Conclusion: The synergy between GEM and evofosfamide appears to stem from the dual action of GEM's effect on tumor vasculature and the GEM inhibition of the homologous recombination DNA repair process. The relative importance of each pathway is dependent on the tumor microenvironment and merits further study. and is also made available for use under a CC0 license.

Cancer Research, Jun 15, 2022

[Purpose] In pancreatic ductal adenocarcinoma (PDAC) which is characterized by an intense desmopl... more [Purpose] In pancreatic ductal adenocarcinoma (PDAC) which is characterized by an intense desmoplastic feature, the extracellular matrix (ECM) can significantly influence the tumor microenvironment (TME). Hyaluronan (HA), a major component of ECM, is associated with elevated tumor pressure, vascular collapse, and poor perfusion in TME, conferring hypoxia. HA expression is also correlated with poor prognosis in the patients with PDAC. PEGylated human hyaluronidase (PEGPH20) enzymatically depletes hyaluronan in tumors. The resultant improvement in vascular patency and blood perfusion is expected to increase the delivery of therapeutic molecules. The aim of this study was to investigate the change in physiologic and metabolic profile of the tumor in response to treatment with PEGPH20 using multi-modal imaging techniques. We also investigated the capability of PEGPH20 to enhance treatment effect of radiation. [Methods] Athymic nude mice were inoculated with BxPC3 (human pancreatic adenocarcinoma) tumor cells transduced with hyaluronan synthase 3 (HAS3) to the right tibial periosteum. BxPC3-HAS3 tumor treated with PEGPH20 or control buffer were scanned with Electron paramagnetic Resonance imaging (EPRI), dynamic contrast enhanced (DCE) MRI, ultra-small superparamagnetic iron oxide (USPIO) MRI, Photoacoustic imaging (PAI), and Hyperpolarized 13C-MRI using [1-13C] pyruvate to evaluate intratumor pO2, intratumor perfusion, blood volume, O2 saturation, and glycolysis, respectively. [Results] EPRI showed significantly increased pO2 in PEGPH20 treated group. DCE-MRI and USPIO-MRI showed improved perfusion/permeability and local blood volume, respectively after PEGPH20 treatment, accounting for the increase in tumor oxygenation. PAI provided the evidence of immediate changes in tumor oxygenation after treatment. Hyperpolarized 13C-MRI using [1-13C] pyruvate suggested the decreased glycolytic flux evaluated by lactate/pyruvate ratio after PEGPH20 treatment. Combination of radiotherapy and PEGPH20 synergistically delayed tumor progression and prolonged the survival. [Conclusions] This study examined the effect of PEGPH20 on TME in PDAC xenograft model by using non-invasive multimodal imaging techniques. In summary, the non-invasive imaging modalities were useful in evaluating the changes in hemodynamics and metabolism in TME induced by modulation of ECM such as PEGPH20 treatment. PEGPH20 enhanced treatment effect of radiation therapy. The results validated the utility of the imaging methods to non-invasively monitor the changes in TME and predicted the radiosensitizing effect of hyaluronan depletion. Citation Format: Yu Saida, Tomohiro Seki, Shun Kishimoto, Jeffrey R. Brender, Gadisetti VR. Chandramouli, Yasunori Otowa, Kota Yamashita, Kazutoshi Yamamoto, Nallathamby Devasahayam, Murali C. Krishna. Multimodal molecular imaging detects early reoxygenation induced by hyaluronan depletion in pancreatic cancer model mouse [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5974.

Proceedings of SPIE, Feb 12, 2009

A novel fast imaging modality for free radicals in vivo: continuous wave (CW) EPR imaging with di... more A novel fast imaging modality for free radicals in vivo: continuous wave (CW) EPR imaging with direct detection and rapid field scan in the presence of rotating gradients," Proc. SPIE 7170, Design and Quality for Biomedical Technologies II, 717008 (