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Papers by John Buatti

International Journal of Radiation Oncology*Biology*Physics, 2021

PURPOSE/OBJECTIVE(S) Ataxia telangiectasia mutated protein (ATM) is one of the key sensors of DNA... more PURPOSE/OBJECTIVE(S) Ataxia telangiectasia mutated protein (ATM) is one of the key sensors of DNA damage and specific inhibitors of ATM are potent radiosensitizers. However, their clinical utility with radiation (RT) is limited because they lack tissue specificity and increase normal tissue injury. Pharmacologic (high dose) ascorbate (P-AscH-) selectively increases oxidative stress in tumors while functioning as a donor antioxidant and reducing RT damage in normal tissues. We hypothesized that P-AscH- could enhance the therapeutic index of ATM-inhibitor based chemoradiation (CRT) for colorectal cancer (CRC) by simultaneously enhancing efficacy and reducing RT bowel injury. MATERIALS/METHODS Human HCT116, SW480, and HT29 and murine CT26 and MC38 CRC models were used. Clonogenic survival was assessed following single-fraction RT (2-8 Gy) +/- P-AscH- (5 pM/cell) +/- veliparib (PARP), VE821 (ATR), or KU60019 (ATM). Catalase expression was induced using HCT116 cells expressing a doxycycline inducible catalase transgene. DNA double strand breaks (DSBs) were quantified using neutral comet assays 0-24 hours post RT. Cell cycle phases were assessed using flow cytometry. ATM and pATM localization were assessed using IF. Jejunal toxicity was assessed using IHC in fixed tissues following single fraction (10 Gy) whole abdominal RT in c57bl/6 mice. Tumor growth delay was assessed following RT (5 Gy x 3) +/- drug treatment in unilateral flank tumors. RESULTS Veliparib, VE821, and KU60019 were potent radiosensitizers in HCT116, SW480, HT29, MC38, and CT26 CRC tumor models and P-AscH- further reduced clonogenic survival with DRIs in all lines except for HT29. In contrast, P-AscH- enhanced survival of cultured HUVEC and FHs-74 cells exposed to RT. Enhanced cell kill with P-AscH- is H202 mediated as it is completely attenuated by inducible catalase expression. P-AscH- significantly increased the number of DNA DSBs in tumors after RT in vitro. Despite the increase in DNA DSBs, P-AscH-significantly decreased nuclear localization of activated pATM after RT and significantly decreased the fraction of cells in G2/M phases of the cell cycle. In vivo, RT + P-AscH- + KU60019 induced more tumor growth delay/clearance than all other combinations in unilateral MC38 or HCT116 flank tumors. Finally, P-AscH- significantly reduced loss of jejunal crypt cell density, epithelial architecture, and markers of lipid and protein oxidation following whole abdominal RT. CONCLUSION P-AscH- selectively enhances the efficacy of ATM-based CRT in CRC tumor models while simultaneously decreasing RT-mediated small bowel toxicity. In tumors, P-AscH- enhances DNA DSBs by stimulating an H202 flux and prevents activation of DNA repair pathways and cell cycle checkpoints by inhibiting RT-induced activation of ATM. Selective radioprotectors like P-AscH- could facilitate the clinical translation ATM inhibitors as radiosensitizers.

Redox biology, Jun 1, 2023

Pharmacological ascorbate (P-AscH-), as an adjuvant to standard treatment for glioblastoma, may s... more Pharmacological ascorbate (P-AscH-), as an adjuvant to standard treatment for glioblastoma, may selectively enhance cancer cell killing. The mechanisms of P-AscH- have been associated with redox changes in the labile iron pool. This study applies T2* and QSM to assess the redox changes in 40 glioblastoma patients receiving standard treatment and adjuvant P-AscH-. The results demonstrate an increase in T2* values and a decrease in QSM values within contrast-enhancing lesions 1 hour after P-AscH- infusion. These changes in T2* and QSM may result from the redox changes by P-AscH-, supporting the potential for imaging assessment of response to P-AscH-.

Chemoradiation therapy is the mainstay for treatment of locally advanced, borderline resectable p... more Chemoradiation therapy is the mainstay for treatment of locally advanced, borderline resectable pancreatic cancer. Pharmacologic ascorbate (P-AscH−, i.e., intravenous infusions of ascorbic acid, vitamin C), but not oral ascorbate, produces high plasma concentrations capable of selective cytotoxicity to tumor cells. In doses achievable in humans, P-AscH− decreases the viability and proliferative capacity of pancreatic cancer via a hydrogen peroxide (H2O2)-mediated mechanism. In this study, we demonstrate that P-AscH− radiosensitizes pancreatic cancer cells but inhibits radiation-induced damage to normal cells. Specifically, radiation-induced decreases in clonogenic survival and double-stranded DNA breaks in tumor cells, but not in normal cells, were enhanced by P-AscH−, while radiation-induced intestinal damage, collagen deposition, and oxidative stress were also reduced with P-AscH− in normal tissue. We also report on our first-in-human phase I trial that infused P-AscH− during the radiotherapy “beam on.” Specifically, treatment with P-AscH− increased median overall survival compared with our institutional average (21.7 vs. 12.7 months, P = 0.08) and the E4201 trial (21.7 vs. 11.1 months). Progression-free survival in P-AscH−–treated subjects was also greater than our institutional average (13.7 vs. 4.6 months, P < 0.05) and the E4201 trial (6.0 months). Results indicated that P-AscH− in combination with gemcitabine and radiotherapy for locally advanced pancreatic adenocarcinoma is safe and well tolerated with suggestions of efficacy. Because of the potential effect size and minimal toxicity, our findings suggest that investigation of P-AscH− efficacy is warranted in a phase II clinical trial.Significance:These findings demonstrate that pharmacologic ascorbate enhances pancreatic tumor cell radiation cytotoxicity in addition to offering potential protection from radiation damage in normal surrounding tissue, making it an optimal agent for improving treatment of locally advanced pancreatic adenocarcinoma.

Cancer Research, Jun 15, 2022

Purpose/Objective(s): The ATM protein is key to DNA double strand break (DSB) repair and ATM inhi... more Purpose/Objective(s): The ATM protein is key to DNA double strand break (DSB) repair and ATM inhibitors are potent radiosensitizers. Clinical translation of these agents in combination with radiotherapy (RT) has been limited due to concerns for increased normal tissue toxicity. Pharmacologic Ascorbate (P-AscH-) radiosensitizes cancer cells via generation of a H2O2 flux while acting as a radioprotector in normal tissue via free radicle scavenging. We hypothesized that P-AscH- could open a therapeutic window for the combination of RT and ATM inhibition in colorectal cancer (CRC). Materials/Methods: Multiple human and murine CRC cell lines were used in vitro. Clonogenic survival was assessed after combinations of RT +/- P-AscH and DNA Repair Inhibitors (DRIs). Catalase expression was induced using HCT116 cells expressing a doxycycline-inducible catalase transgene. DSBs were quantified using neutral comet assays. Cell cycle distribution were assessed using flow cytometry. ATM localization/activation were assessed using IF. Normal tissue toxicity in vivo was assessed using IHC following whole-abdominal RT. Survival and tumor growth delay was assessed following 5Gyx3 +/- drug treatment to unilateral flank tumors in syngeneic/xenograft models. Results: DRIs were potent radiosensitizers in most CRC cell lines and the addition of P-AscH- further reduced clonogenic survival. In contrast, P-AscH- did not radiosensitize HUVEC or FHs-74int normal cell lines. P-AscH- significantly increased the number of DSBs in tumors after RT in vitro. P-AscH- simultaneously decreased nuclear localization and activation of pATM after RT and perturbed G2+M phase progression. In vivo, the addition of P-AscH- to RT + KU60019 significantly increased survival delayed tumor growth in syngeneic/xenograft models while ameliorating increased normal bowel toxicity as measured by jejunal crypt density, acute weight loss, rectal injury, and markers of oxidative stress following whole-abdominal RT. The effects of P-AscH were reversed by inducing the overexpression of catalase. Conclusion: P-AscH- improves both aspects of the therapeutic window of RT+ATM inhibition in CRC by simultaneously enhancing tumor efficacy while decreasing RT-mediated bowel toxicity. The effects of P-AscH- on clonogenic survival, initial and persistent DSBs, G2+M phase perturbations, ATM activation/localization, and in vivo survival and tumor growth delay were dependent on H202 flux. Normal tissue protection appears to be related to decreased oxidative stress. Citation Format: Cameron M. Callaghan, Ibrahim M. Abukhiran, Richard V. Van Rheeden, Amanda L. Kalen, Samuel N. Rodman, Michael S. Petronek, Kranti A. Mapuskar, Sarah L. Mott, Mitchell C. Coleman, Prabhat C. Goswami, John M. Buatti, Bryan G. Allen, Douglas R. Spitz, Joseph M. Caster. Pharmacologic ascorbate opens a therapeutic window for ATM inhibition and radiotherapy in colorectal cancer [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 811.

Redox biology, Jul 1, 2022

Statistics and Computing

High-dimensional cancer data can be burdensome to analyze, with complex relationships between mol... more High-dimensional cancer data can be burdensome to analyze, with complex relationships between molecular measurements, clinical diagnostics, and treatment outcomes. Data-driven computational approaches may be key to identifying relationships with potential clinical or research use. To this end, reliable comparison of feature engineering approaches in their ability to support machine learning survival modeling is crucial. With the limited number of cases often present in multi-omics datasets (“big p, little n,” or many features, few subjects), a resampling approach such as cross validation (CV) would provide robust model performance estimates at the cost of flexibility in intermediate assessments and exploration in feature engineering approaches. A holdout (HO) estimation approach, however, would permit this flexibility at the expense of reliability. To provide more reliable HO-based model performance estimates, we propose a novel sampling procedure: representative random sampling (RR...

Mission Statement: The American Society for Radiology Oncology (ASTRO) has formed a multi-society... more Mission Statement: The American Society for Radiology Oncology (ASTRO) has formed a multi-society Task Force to undertake an initiative to promote the Integration of the Healthcare Enterprise (IHE) – Radiation Oncology (RO), fostering seamless connectivity and integration of radiotherapy equipment and the patient health information systems. The Task Force will include members from ASTRO, RSNA, American Association of Physicists in Medicine (AAPM), the American College of Radiology (ACR) and the Medical Imaging and Technology Alliance (MITA). In addition, members of the International community have also been invited to participate in IHE-RO. The IHE-RO Task Force, in close collaboration with radiotherapy product manufacturers, will develop appropriate integration profiles for radiation therapy and setup a demonstration of seamless communication among the full array of radiotherapy products.

Journal of Neurosurgery, 2001

Object. The aim of this study was to identify factors associated with delayed cranial neuropathy ... more Object. The aim of this study was to identify factors associated with delayed cranial neuropathy following radiosurgery for vestibular schwannoma (VS or acoustic neuroma) and to determine how such factors may be manipulated to minimize the incidence of radiosurgical complications while maintaining high rates of tumor control. Methods. From July 1988 to June 1998, 149 cases of VS were treated using linear accelerator radiosurgery at the University of Florida. In each of these cases, the patient's tumor and brainstem were contoured in 1-mm slices on the original radiosurgical targeting images. Resulting tumor and brainstem volumes were coupled with the original radiosurgery plans to generate dose—volume histograms. Various tumor dimensions were also measured to estimate the length of cranial nerve that would be irradiated. Patient follow-up data, including evidence of cranial neuropathy and radiographic tumor control, were obtained from a prospectively maintained, computerized dat...

International Journal of Radiation Oncology*Biology*Physics, 2009

Journal of Clinical Medicine, 2022

MR-guided adaptive radiotherapy (MRgART) provides opportunities to benefit patients through enhan... more MR-guided adaptive radiotherapy (MRgART) provides opportunities to benefit patients through enhanced use of advanced imaging during treatment for many patients with various cancer treatment sites. This novel technology presents many new challenges which vary based on anatomic treatment location, technique, and potential changes of both tumor and normal tissue during treatment. When introducing new treatment sites, considerations regarding appropriate patient selection, treatment planning, immobilization, and plan-adaption criteria must be thoroughly explored to ensure adequate treatments are performed. This paper presents an institution’s experience in developing a MRgART program for a 1.5T MR-linac for the first 234 patients. The paper suggests practical treatment workflows and considerations for treating with MRgART at different anatomical sites, including imaging guidelines, patient immobilization, adaptive workflows, and utilization of bolus.

2018 IEEE 15th International Symposium on Biomedical Imaging (ISBI 2018), 2018

Positron emission tomography and computed tomography (PET-CT) plays a critically important role i... more Positron emission tomography and computed tomography (PET-CT) plays a critically important role in modern cancer therapy. In this paper, we focus on automated tumor delineation on PET-CT image pairs. Inspired by co-segmentation model, we develop a novel 3D image co-matting technique making use of the inner-modality information of PET and CT for matting. The obtained co-matting results are then incorporated in the graph-cut based PET-CT co-segmentation framework. Our comparative experiments on 32 PET-CT scan pairs of lung cancer patients demonstrate that the proposed 3D image co-matting technique can significantly improve the quality of cost images for the co-segmentation, resulting in highly accurate tumor segmentation on both PET and CT scan pairs.

arXiv: Computer Vision and Pattern Recognition, 2019

Automated surface segmentation is important and challenging in many medical image analysis applic... more Automated surface segmentation is important and challenging in many medical image analysis applications. Recent deep learning based methods have been developed for various object segmentation tasks. Most of them are a classification based approach (e.g., U-net), which predicts the probability of being target object or background for each voxel. One problem of those methods is lacking of topology guarantee for segmented objects, and usually post processing is needed to infer the boundary surface of the object. In this paper, a novel model based on 3-D convolutional neural networks (CNNs) and Conditional Random Fields (CRFs) is proposed to tackle the surface segmentation problem with end-to-end training. To the best of our knowledge, this is the first study to apply a 3-D neural network with a CRFs model for direct surface segmentation. Experiments carried out on NCI-ISBI 2013 MR prostate dataset and Medical Segmentation Decathlon Spleen dataset demonstrated promising segmentation res...

Clinical Cancer Research, 2019

Purpose: Standard treatment for glioblastoma (GBM) includes surgery, radiation therapy (RT), and ... more Purpose: Standard treatment for glioblastoma (GBM) includes surgery, radiation therapy (RT), and temozolomide (TMZ), yielding a median overall survival (OS) of approximately 14 months. Preclinical models suggest that pharmacologic ascorbate (P-AscH−) enhances RT/TMZ antitumor effect in GBM. We evaluated the safety of adding P-AscH− to standard RT/TMZ therapy. Patients and Methods: This first-in-human trial was divided into an RT phase (concurrent RT/TMZ/P-AscH−) and an adjuvant (ADJ) phase (post RT/TMZ/P-AscH− phase). Eight P-AscH− dose cohorts were evaluated in the RT phase until targeted plasma ascorbate levels were achieved (≥20 mmol/L). In the ADJ phase, P-AscH− doses were escalated in each subject at each cycle until plasma concentrations were ≥20 mmol/L. P-AscH− was infused 3 times weekly during the RT phase and 2 times weekly during the ADJ phase continuing for six cycles or until disease progression. Adverse events were quantified by CTCAE (v4.03). Results: Eleven subjects w...

International Journal of Radiation Oncology*Biology*Physics, 2007