Hemant K Roy, M.D., Professor of Medicine, Chief, Section of Gastroenterology
Dr. Roy joined the faculty in 2013. He completed his medical degree from Northwestern University with distinction and completed internal medicine residency at Beth Isreal followed by GI Fellowship at University of Chicago.
Dr. Roy’s research interests center on GI cancer risk stratification using intermediate biomarkers of field carcinogenesis. He has been involved in the development and clinical implementation of a variety of biophotonic techniques for risk stratification encompassing both fiberoptic probes and cytological based techniques and these are complemented by a variety of molecular markers including microRNAs.
This has served as a platform for assessing risk modification via chemoprevention and applied to a number of non-GI malignancies including lung and ovarian cancer. Dr. Roy is a fellow of the American Gastroenterological Association and member of the Early Detection Research Network and the Cancer Biomarkers Study Section of the NIH.
More clinically, his interests are in high risk colon cancer syndromes and role of gender in colorectal cancer screening. Throughout his career he has also been involved in teaching receiving numerous awards in this regard.
Uri Avissar, M.D., Assistant Professor of Medicine
Dr. Avissar joined the faculty of the Section of Gastroenterology in 2008. Dr. Avissar received his medical degree at the University of Rochester School of Medicine and Dentistry. After finishing his internal medicine residency at the University of Pittsburgh Medical Center, he went on to complete a fellowship in gastroenterology and a fellowship in transplant hepatology at the University of Cincinnati. While maintaining a broad interest in gastroenterology, Dr. Avissar’s clinical focus is in hepatology, and his practice encompasses all aspects of liver disease. His particular interests include the evaluation of liver transplant candidates and the medical management of liver transplant recipients. Dr. Avissar is also avidly involved in medical education and currently serves as the Assistant Fellowship Director for the Section.
Charles M. Bliss, Jr., M.D., Assistant Professor of Medicine
Dr. Bliss joined the faculty in 2000. He received his medical degree from Boston University, completed his internal medicine residency at Boston City Hospital, and his gastroenterology fellowship at Boston Medical Center. He practices as a general gastroenterologist. His interests in clinical practice include H. pylori treatment and inflammation. As part of his practice, Dr. Bliss has included some of his patients in clinical studies, including the studies of Dr. Roy involving spectroscopy to develop different screening tools for colon cancer. Part of his clinical practice includes an outreach at the East Boston Neighborhood Health Center. Dr. Bliss is a Fellow of the American College of Physicians and a Fellow of the American Gastroenterological Association.
Audrey H. Calderwood, M.D., M.S., Assistant Professor of Medicine
Dr. Calderwood joined the faculty in 2009. She received her medical degree from the University of Chicago’s Pritzker School of Medicine. She completed her internal medicine residency at the University of Chicago and the Brigham and Women’s Hospital, followed by gastroenterology fellowship at Boston Medical Center. She received her Master’s Degree in Health Services Research from the Boston University School of Public Health.
Dr. Calderwood’s clinical interests include general gastroenterology, high-risk cancer syndromes, and celiac disease. Her research focuses on quality in gastroenterology, specifically optimizing appropriate use of colorectal cancer screening and surveillance. She is the recipient of an NIH Career Development Award (K08). She is a Fellow of the American Society of Gastrointestinal Endoscopy where she serves on the Quality Assurance in Endoscopy Committee and the Research Committee. She has chaired national guidelines on safety in the endoscopy unit and co-directs the Improving Quality and Safety in Your Endoscopy Unit Course. She is also a Fellow of the American College of Gastroenterology.
Lizabeth Cline, NP Instructor of Medicine
Ms. Cline received her BS in Nursing in 1982 from Boston University and her MSN from Syracuse University in 1995. Ms. Cline’s clinical focus is liver disease including fatty liver disease and viral hepatitis.
Francis A. Farraye, M.D., MSc, Clinical Director, Section of Gastroenterology and Co-Director, Center for Digestive Disorders, Professor of Medicine, Boston University School of Medicine
After graduating from the State University of New York at Stony Brook, Dr. Farraye earned his medical doctorate from the Albert Einstein College of Medicine in New York and his master’s degree in Epidemiology from the Harvard School of Public Health. He completed an internal medicine residency and gastroenterology fellowship at the Beth Israel Hospital in Boston.
Dr. Farraye’s clinical interests are in the care of patients with inflammatory bowel disease and the management of colon polyps and colorectal cancer. Dr. Farraye’s clinical interests are in the care of patients with inflammatory bowel disease and the management of colon polyps and colorectal cancer. He is currently investigating C. difficile infection in IBD patients, the management and diagnosis of dysplasia and cancer in patients with IBD; pouchitis after ileal pouch anal anastomosis; vaccinations in patients with IBD; and the role of serrated polyps as an alternative pathway to the development of colorectal cancer.
A frequent speaker and invited lecturer on topics on the diagnosis and management of inflammatory bowel disease, Dr. Farraye has authored or co-authored over 350 original scientific manuscripts, chapters, reviews and abstracts. He is the series editor for the text Curbside Consultations in Gastroenterology and co-wrote the text, Curbside Consultation in Inflammatory Bowel Disease and Gastrointestinal Emergencies. His newest books for patients are Questions and Answers about Ulcerative Colitis, Questions and Answers about Crohn’s Disease and Ulcerative Colitis for Dummies.
Dr. Farraye is a Fellow of the American College of Physicians, American Society of Gastrointestinal Endoscopy (ASGE), American Gastroenterological Association (AGA) and the American College of Gastroenterology (ACG). He has served as the AGA representative on the National Colorectal Cancer Round Table, chair of the lower gastrointestinal disorders section of the Annual Scientific Program Committee of the ASGE and a member of the ASGE Technology Committee and a member of the Board of Trustees in the ACG. He is a member of the Crohn’s and Colitis Foundation of America (CCFA) Professional Education Committee and the Chapter Medical Advisory Committee for the New England CCFA and a past chairman. The New England CCFA named Dr. Farraye Humanitarian of the Year in 2003. He was the 2009 recipient of the ACG William Carey Award for service to the college. In 2013, he received the Clinical Research Mentor of the year award from the house staff in the Department of Medicine at Boston Medical Center. Dr. Farraye was recognized as a “Top Doctor” in Gastroenterology by Boston magazine in 2010-2014 and by U.S. News and World Report in 2011-2014.
Christopher Huang, M.D., Assistant Professor of Medicine
Dr. Huang is a clinician-educator with particular interest in therapeutic endoscopy and endoscopy training. He performs a wide range of diagnostic and therapeutic endoscopy procedures, including endoscopic retrograde cholangiopancreatography, endoscopic ultrasonography, endoscopic mucosal resection, enteral stenting, and radiofrequency ablation of dysplastic Barrett’s esophagus. His other clinical interests include colorectal cancer prevention and management of gastrointestinal complications of bariatric surgery. He is actively involved in the education and training of Gastroenterology fellows and serves as the fellowship program’s Director of Endoscopy Education. He also serves as the Subspecialty Education Coordinator for the Internal Medicine residency training program. His regular teaching responsibilities include lecturing on various topics to medical residents and Gastroenterology fellows, and teaching in several courses at Boston University School of Medicine and School of Dental Medicine. He is also a member of the Admissions Committee for Boston University School of Medicine’s Seven-Year Liberal Arts/Medical Education Program and Modular Medical Integrated Curriculum Program.
His academic interests include the role of serrated polyps in colorectal cancer pathogenesis, and he has co-authored several articles on the topic in peer-reviewed journals. He has also authored Up-To-Date topic cards on Endoscopy in Bariatric Surgical Patients and ERCP in patients with Roux-en-Y anatomy.
Dr. Huang has participated as faculty in several local and regional courses, including the Boston International Live Endoscopy Course, Harvard’s Advanced Diagnostic and Therapeutic Endoscopy Course, and Children’s Hospital’s Advances in Pediatric Gastroenterology, Hepatology, and Nutrition Course. Dr. Huang is a member of the American Society for Gastrointestinal Endoscopy, the American Gastroenterological Association, the American College of Gastroenterology, and serves on the Education Committee of the Massachusetts Gastroenterology Association.
Brian C. Jacobson, M.D., M.P.H., Medical Director of the Boston Accountable Care Organization, Director of Gastroenterology Quality Improvement, Associate Professor of Medicine
Dr. Jacobson serves as the Medical Director for Boston Medical Center’s new Accountable Care Organization. In this role he oversees quality improvement and population healthcare efforts for BMC and several nearby community health centers. He is also an Associate Professor of Medicine at Boston University School of Medicine. Dr. Jacobson received his undergraduate degree from Amherst College, his medical degree from Albert Einstein College of Medicine, and his Master’s Degree in Public Health from Harvard University School of Public Health. He completed both his residency in Internal Medicine and his fellowship in Gastroenterology at Brigham and Women’s Hospital. He later served as Chief Medical Resident at Brigham and Women’s followed by a fellowship in Advanced Interventional Endoscopy at the Brigham and Women’s and Massachusetts General Hospitals.
Dr. Jacobson is also a therapeutic endoscopist performing endoscopic ultrasonography with fine-needle aspiration, ERCP, endoscopic mucosal resection, and placement of internal stents for palliation of malignant obstructions. He participates in the training of fellows, residents, and medical students at Boston Medical Center and Boston University School of Medicine. Dr. Jacobson’s research interests focus on Barrett’s esophagus as well as bowel preparation for colonoscopy. He serves as a Councilor on the Governing Board of the American Society for Gastrointestinal Endoscopy.
David R. Lichtenstein, M.D., FACG Director of Gastrointestinal Endoscopy Associate Professor of Medicine
Dr. Lichtenstein is the Director of the Gastrointestinal Endoscopy at Boston Medical Center and Associate Professor of Medicine at Boston University School of Medicine. He received his medical doctorate from the University of Pennsylvania School of Medicine. After completing a residency in Internal Medicine at Duke University Medical Center, Dr. Lichtenstein received fellowship training in Gastroenterology at Beth Israel Hospital in Boston. He later served as Chief Medical Resident at Duke University Medical Center and subsequently received advanced interventional endoscopy training at Duke University Medical Center and Brigham and Women’s Hospital.
Dr. Lichtenstein is currently the director of endoscopy at Boston Medical Center where he directs a state-of-the-art center with dedicated facilities for performing a wide array of endoscopic procedures inclusive of advanced technologies such as ERCP, endoscopic ultrasonography, radiofrequency mucosal ablation, and deep enteroscopy. He supervises Gastroenterology Fellowship training in advanced endoscopic procedures and is responsible for evaluating and implementing new endoscopic technologies at Boston Medical Center. His main interests focus on the development and application of endoscopic approaches for diagnosing and managing gastrointestinal hemorrhage, pancreaticobiliary tract disorders, and gastrointestinal malignancies.
Dr. Lichtenstein is an active member and current Fellow of the American Society for Gastrointestinal Endoscopy (ASGE), American College of Gastroenterology (ACG), and American Gastroenterological Association (AGA). He has been listed in The Best Doctors in America database, Boston Magazine issue “Best Doctors of Boston”, as well as Guide to America’s Top Doctors. He is the former chair of the ERCP Section of the Annual Scientific Program Committee for Digestive Disease Week, chair of the Assessment and Certification Task Force, and member of the Research, Standards of Practice, International, Web Education, Gastrointestinal Endoscopy Self-Assessment Program Committees of the ASGE. In addition, he served as past President of the New England Endoscopy Society.
Robert C. Lowe, M.D., Associate Professor of Medicine
Dr. Lowe is a graduate of Harvard Medical School, and he completed his residency in Internal Medicine at Brigham and Women’s Hospital. He then trained in Gastrtoenterology at Boston Medical Center before returning to BWH to serve as Chief Resident in Medicine. He joined the BMC faculty in 2001, and served as GI Fellowship Director until 2015. Dr. Lowe has an active role in the Medical Residency Program, serving as an Evans Educator. In this role, he attends frequently on the inpatient Medicine Service and facilitates educational conferences twice a month for the Medicine Housestaff and students. He also directs the Medical Education Pathway for residents interested in a careers in medical educatiom. His clinical focus is in hepatology, and his practice encompasses all aspects of liver disease. His particular interests include the treatment of viral hepatitis, the management of cirrhosis and the complications of advanced liver disease, and the management of metabolic liver diseases.
T. Carlton Moore, M.D., Assistant Professor in Medicine
Dr. T. Carlton Moore joined the Section of Gastroenterology after completing gastroenterology fellowship here at Boston Medical Center. He received his medical doctorate from Johns Hopkins School of Medicine and completed internal medicine residency at the Hospital of the University of Pennsylvania.
Dr. Moore’s principal area of expertise is in gastrointestinal motility and esophageal disorders. He works closely with our thoracic surgeons, otolaryngologists, and rheumatologists to manage difficult esophageal cases. He runs the motility elective for the gastroenterology fellows, with didactics, hands on experience in the motility lab, and reading esophageal and anorectal manometry studies
Gustavo Mostoslavsky, M.D., Ph.D., Assistant Professor of Medicine
Dr. Mostoslavsky received his M.D. from the University of Tucuman in Argentina and his Ph.D. from the Hebrew University in Jerusalem, Israel. His longstanding interest in basic science and regenerative medicine brought him to the laboratory of Dr. Richard Mulligan at Harvard Medical School to pursue postdoctoral studies with stem cells and gene therapy. In 2008 Dr. Mostoslavsky was recruited to the faculty of the Section of Gastroenterology in the Department of Medicine at Boston University School of Medicine.
Dr. Mostoslavsky Lab is a basic science laboratory and his goal is to advance our understanding of stem cell biology with a focus on their genetic manipulation via gene transfer and their potential use for stem cell-based therapy. In 2010 Dr. Mostoslavsky founded and Co-directs the Center for Regenerative Medicine (CReM) at BUSM, which has recently moved into a new state-of-the-art facility, comprising six Research Programs. Project areas in the lab focuses on the use of different stem cell populations, including embryonic and induced Pluripotent stem cells, hematopoietic stem cells and intestinal stem cells. For more details visit www.mostoslavskylab.com
Ansu Mammen Noronha, M.D., Assistant Professor of Medicine
Dr. Noronha joined the Section of Gastroenterology in 2009 after completing a gastroenterology fellowship at Boston University School of Medicine. She received her medical doctorate from
David P. Nunes, M.D., Director of Hepatology, Associate Professor of Medicine
Dr. Nunes has achieved considerable expertise and prominence in the area of hepatitis C/HIV co-infection and noninvasive evaluation of hepatic fibrosis markers, and he is now considered one of the foremost experts in this area throughout the United States. Despite a number of competing clinical, teaching and administrative duties, Dr. Nunes has been able to maintain a deep commitment to research. During his tenure at Boston Medical Center, his research activities have evolved from mostly basic science work related to elucidating the molecular basis of gallstone formation to more translational and clinical work related to the evaluation of non-invasive markers of liver fibrosis and the treatment of hepatitis C/HIV co-infection. He has authored or co-authored 47 original articles in peer reviewed journals, four book chapters, two electronic publications and 48 abstracts. His work has been presented at numerous national and international meetings of a wide variety of professional organizations. He has also been invited to serve on several ad hoc NIH grant review committee, attesting to his prominence as an investigator in the area of hepatitis C control.
Gwynneth Offner, Ph.D., Director of the M.A. in Medical Sciences Program, Associate Professor of Medicine
Dr. Gwynneth Offner focuses on medical education and on mentoring and advising fellows who plan to incorporate teaching into their careers. Her interests include developing and evaluating new methods of pedagogy in the medical school curriculum including on-line modules, promoting active student engagement in classroom teaching and using clinical cases to teach basic science content. She also maintains an interest in the function of mucins in the biliary and gastrointestinal tracts and their role in the development of cancer and IBD. Dr. Offner directs the MS in Medical Sciences Program at BUSM and is an Assistant Dean of Admissions at the medical school.
Angela Reffel PA-C, MHP, Instructor of Medicine
Angela Reffel received her Bachelor’s Degree at
Elihu M. Schimmel, M.D., Professor of Medicine
Dr. Schimmel has focused a career of clinical investigations on several gastrointestinal disorders particularly prevalent in the population of military veterans: Barrett’s esophagus, inflammatory bowel disorders (Crohn’s Disease, ulcerative colitis and infectious colitis), and chronic pancreatitis. In addition, he has maintained a longitudinal study of patients whose gastrointestinal diseases have been treated surgically: clinical follow-up of patients undergoing esophageal resection for cancer; patients who have had gastric surgery for peptic ulcer disease; post-colectomy ileostomy; and those who have had pancreatic surgery for pancreatic inflammatory disease. Since 1976, he has served on the Nutrition Support Program at the VA Boston Healthcare System with special interest in protein metabolism and the nutritional requirements for amino acids. Since 1992, he has been in the forefront of implementation of the Computerized Patient Record System at the Boston VA, and in the use of computer-based technology for the management of clinical data. Lastly, he has an active interest in the cognitive processes of collecting and analyzing clinical data in patients with disorders of the gastrointestinal system in arriving at assessments for the formulation of diagnostic and therapeutic plans. Dr. Schimmel has developed expertise in the area of translational teaching, bringing the results of laboratory research to the care of patients for fellows, residents, and medical students in the outpatient clinics and at the hospital bedside in a didactic synthesis.
Paul C. Schroy, III, M.D., M.P.H., Professor of Medicine
Dr. Paul Schroy is a graduate of Haverford College, Jefferson Medical School and the Boston University School of Public Health. He completed his residency in Internal Medicine at the North Shore University Hospital (Cornell University) and fellowship in Gastroenterology at the Memorial Sloan-Kettering Cancer Center. Dr. Schroy is a Professor of Medicine at the Boston University School of Medicine and Director of Clinical Research for the Section of Gastroenterology at Boston Medical Center. He is the recipient of a number of grants, which support his ongoing research in the area of community-based colorectal cancer control. Dr. Schroy is a founding member and former chair of the Massachusetts Colorectal Cancer Working Group and former member of the Steering Committee of the National Colorectal Cancer Roundtable. He is also the current co-chair of the National Colorectal Cancer Roundtable’s Familial Risk Task Group, a member of the American Cancer Society New England Division’s Colorectal Cancer Advisory Committee, and a member of the Massachusetts Department of Public Health’s Cancer Registry Advisory Committee.
Utilizing an integrated approach that incorporates a strong background in laboratory research, clinical experience and public health training, Dr. Schroy’s research activities focus primarily on the development, implementation and evaluation of model programs for community-based colorectal cancer control. Current ongoing studies are exploring: (1) the role of shared decision-making as a strategy for increasing patient participation in colorectal cancer screening; (2) the epidemiology of colorectal neoplasia; (3) the feasibility and validity of novel colorectal cancer screening strategies such as stool-based DNA testing and virtual colonoscopy; and (4) quality issues related to colorectal cancer screening.
Satish K. Singh, MD, Associate Professor of Medicine, Biomedical Engineering, and Molecular & Translational Medicine; Associate Chief of Gastroenterology, Director of Endoscopy, VA Boston Healthcare System
The Singh Lab is focused on translational research spanning concept to clinical application. Our main interests are (1) novel biophotonic approaches to endoscopic diagnosis and treatment (2) point-of-service diagnostics using optical and nano-scale technologies, and (3) hormonal regulation of gut epithelial nutrient transport related to obesity and diabetes.
Our laboratory uses technological advances to address specific clinical needs by bridging disciplines rigorously. Together with colleagues in the BU College of Engineering, we have developed novel spectroscopically-guided tools that aid in “optical biopsy,” or tissue classification in situ and in real-time. These low-cost, clinically-friendly “smart” instruments are accessible to any practitioner and can be used to guide biopsies, detect tumor margins, identify dysplastic tissue, and assess for the presence of cancer and disease field effects in real-time during endoscopy. In another project, we have developed a novel fiberoptically-mediated confocal fluorescence endomicroscope that can be used to reveal unprecedented structural and functional detail in situ during endoscopy. In the area of nanotechnology, we have developed a handheld disposable nanoscale microfluidic system capable of isolating nucleic acids from bacteria in clinical samples. As a result, we can perform on-chip- PCR detection of stool pathogens including Clostridium difficile.
At VA Boston, I am overseeing a new, six-room state-of-the art endoscopy facility that will open in Q1 2014. This “endoscopy unit of the future” will provide a breadth of cutting-edge capabilities unparalleled in the nation for patient care, research, and training. Capabilties will include confocal & optical coherence endomicroscopies; contrast-enhanced endoscopic sonography; elastography; electromagnetic navigation endoscopy; full HD video integration, digital pathology scanners; virtual reality simulation & training; enhanced capsule endoscopy, and the newest HD wide-angle multiband endoscopes for all applications.
At the “bench,” in the field of integrative physiology, we have recently published that the physiological incretin hormone, GIP, in fact directly stimulates intestinal nutrient uptake. This novel hormonal “entero-enteric axis” may be key to the pathogenesis of obesity, type-2 diabetes, glycemic control and the anabolic response to feeding. We continue work on elucidating the mechanisms of incretin-regulated nutrient absorption using a variety of state-of-the art cellular and molecular biological approaches.
Kathleen Sullivan, MSRN, ANP
Kathleen Sullivan is a nurse practitioner for the Section of Gastroenterology at Boston Medical Center. She received her Master of Arts in Clinical Psychology and later received her Master of Science in Nursing and Adult Primary Care at MGH Institute of Health Professions. She is certified as an Adult Nurse Practitioner, and is a member of the National Honor Society for Nursing. Through her gastroenterology experience, she has developed a special interest in inflammatory bowel disease.
Ramesh Wali, Ph.D., Associate Professor of Medicine
Dr. Wali joined the faculty in 2013. Dr. Wali received his doctorate degree from the Postgraduate Institute of Medical education and Research; Chandigarh, India. He did his postdoctoral fellowship from the University of South California before taking faculty positions at the University of Chicago, Chicago, IL and later at Northwestern University, Evanston, IL. Dr. Wali has long standing research interest is in the area of cancer biology especially in identifying and characterizing new biomarkers for early detection and chemoprevention of colon cancer. He has been involved in number of bench-to-bedside projects translating basic scientific findings into therapeutic intervention and risk-stratification. Dr. Wali is a member of the American Association of Gastroenterology.
Sharmeel K. Wasan, M.D., Fellowship Director, Section of Gastroenterology, Assistant Professor of Medicine
Dr. Wasan joined the faculty of the Section of Gastroenterology in 2010. She is a graduate of Stanford University in Palo Alto, CA and received her medical doctorate from Albert Einstein College of Medicine in New York. She completed her internal medicine residency at the University of Maryland Medical Center and the Brigham and Women’s Hospital, where she also worked as a hospitalist for one year. She then completed her fellowship in gastroenterology at Boston Medical Center.
In her role as Fellowship Director for the Section, Dr. Wasan is actively involved in the training of fellows and coordinates educational activities for the Fellowship program. She teaches the fellows during their morning reports and pre-clinic lectures, serves as an endoscopy mentor, organizes and mentors the fellows clinic, and facilitates the fellow’s overall career development.
Dr. Wasan’s clinical interests are in inflammatory bowel disease, general gastroenterology, and colorectal cancer prevention. Her research interests include vaccination strategies, health care maintenance, and pregnancy related issues in patients with Crohn’s disease and Ulcerative Colitis. She is currently serving on the Women’s Committee of the American College of Gastroenterology and on the Patient Education Committee of the Crohn’s and Colitis Foundation of America (CCFA). She is also Fellow of the American College of Gastroenterology.
H. Christian Weber, M.D., Assistant Professor of Medicine
The major interest of Dr. Weber’s laboratory focuses on the investigation of molecular mechanisms of mammalian bombesin receptor expression and their intracellular signal transduction pathways in human cancers and obesity. This family of G protein-coupled receptors comprise the gastrin-releasing peptide receptor (GRP-R), the neuromedin B receptor (NMB-R), and the orphan bombesin receptor subtype-3 (BRS-3). With the exception of BRS-3, they are predominantly expressed in the CNS and the gastrointestinal (GI) tract where they mediate important physiologic functions, such as gastric acid secretion, pancreatic secretion, and smooth muscle contraction. Moreover, after ligand-specific activation of the GRP-R in prostate, gastric, colon, and pancreatic cancer cells mediates potent mitogenic properties. In addition, it has now been clearly established in the murine model that GRP-R and BRS-3 play a significant role in energy metabolisms, satiety and obesity.
Accordingly, Dr. Weber’s laboratory is investigating the human GRP-R and BRS-3 gene regulation and their intracellular signaling pathways to determine molecular mechanisms important in gastrointestinal cancer cell proliferation and in obesity. Studies also include the immunohistochemical localization of the receptor molecules in various tissues, structure and function analysis of the human bombesin receptor proteins, and genetic epidemiological studies of bombesin receptor protein mutations. Other interests of Dr. Weber include the genotype-phenotype analysis of patients with familial polyposis syndromes, such as Cowden disease, the pathophysiology of gastric acid secretion, and the molecular pathomechanisms involved in the development of neuroendocrine tumors, such as gastrinoma (Zollinger-Ellison syndrome).