Adjunct Assistant Professor
Department of Pediatrics
Section of Hematology/Oncology
Baylor College of Medicine
Dr. Allan Sison is a pediatric oncologist who primarily cares for children with leukemia, a cancer of the white blood cells. He was recently featured in the Emmy-nominated PBS documentary, “Cancer: The Emperor of All Maladies.”
Dr. Sison first became interested in cancer while he was taking pre-med classes in college. Then, shortly after starting medical school, he joined a buddy program that paired kids with cancer with first-year medical students. Dr. Sison’s “buddy” was a 10-year-old boy named Mathew who had just been diagnosed with a brain tumor. Dr. Sison soon developed a close friendship with Mathew and his family. Dr. Sison actually learned more about the non-medical aspects of cancer diagnosis and treatment during the 3 years that he knew Mathew than he had learned during his entire pediatrics training. For example, Dr. Sison was moved by Mathew’s understanding of the value of cancer research, even at his young age. When Mathew’s cancer relapsed, Mathew asked to participate in a phase 1 clinical trial. Even though Mathew knew that the trial’s intent was not to cure him, he wanted to give other kids a chance at being cured by participating in a trial that would help to improve our understanding of cancer medicine. Mathew is one of the main reasons why Dr. Sison is a pediatric oncologist today.
At first, Dr. Sison was solely interested in the patient care aspect of being a pediatric oncologist. During his pediatric training, he had taken care of several patients whose leukemia had relapsed or returned after treatment with chemotherapy. He wanted to figure out a way to cure these patients. But, in order to do so, he knew that someone had to figure out why their leukemias were so hard to treat. Then, during his pediatric hematology/oncology fellowship, Dr. Sison had his first exposure to the laboratory. He realized that he could figure out some of the answers to his questions by studying leukemia cells in the lab. In turn, those discoveries could be used to improve existing treatments or to develop newer, more powerful therapies. After just a couple of months working in the lab, Dr. Sison knew that he wanted to be a physician-scientist.
Dr. Allan Sison began his research career in the laboratory of Dr. Patrick Brown, an internationally-recognized pediatric leukemia researcher and Director of Pediatric Leukemia at Johns Hopkins. Previous research by Dr. Brown and others had suggested that normal, non-cancerous cells in the bone marrow—known as stromal cells—help small populations of leukemia cells survive chemotherapy treatment. Dr. Sison wondered if protection from stromal cells could be a reason why his patients’ leukemias had relapsed. While working in Dr. Brown’s lab, Dr. Sison studied signals that are sent from bone marrow stromal cells to leukemia cells. Dr. Sison found that these signals allowed acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) cells to be protected from chemotherapy through an increase in a protein called CXCR4. He also found that blocking CXCR4 made ALL and AML more sensitive to chemotherapy in the lab.
Dr. Sison’s research efforts have been supported by grants from St. Baldrick’s Foundation and the Conquer Cancer Foundation of the American Society of Clinical Oncology (ASCO). His work has been presented at several international meetings, including the annual meetings of the American Society of Hematology (ASH) and the American Society of Pediatric Hematology/Oncology (ASPHO).
Dr. Sison’s research has also been published in various scientific journals, including Nature, the British Journal of Haematology, Molecular Cancer Research, and Oncotarget.
Dr. Sison joined Texas Children’s Cancer Center in 2014 as a participant in the K12 Pediatric Oncology Clinical Research Training Program. This program allows him to continue his laboratory-based research and to obtain formal education in clinical research through mentorship and coursework. Dr. Sison’s time is currently divided between performing research in the laboratory, where he is mentored by Dr. Michele Redell, a member of the Texas Children’s Cancer Center faculty and an expert in AML; working to develop and implement leukemia clinical trials; and caring for patients in the Cancer Center. As a member of the Leukemia Program, Dr. Sison cares for children, adolescents, and young adults with ALL, AML, and chronic myeloid leukemia (CML).
Because of his interest in clinical trials, Dr. Allan Sison acquired training in clinical research through the Johns Hopkins Bloomberg School of Public Health, as well as through workshops conducted by ASH, ASCO, and the American Association for Cancer Research (AACR). Dr. Sison subsequently wrote and opened a clinical trial at Johns Hopkins Hospital using allopurinol for patients with pediatric ALL, and he plans to open the trial at Texas Children’s later this year. He is also involved in Children’s Oncology Group (COG), which is the world’s largest organization devoted to pediatric cancer research, and will be involved in serving as a local investigator for a clinical trial for patients with acute promyelocytic leukemia (APL).
MD, Tufts University School of Medicine
BA, Biology and English, Rutgers, The State University of New Jersey
Residency, Pediatrics, Yale-New Haven Hospital
Fellowship, Pediatric Hematology/Oncology, Johns Hopkins University / National Cancer Institute
American Board of Pediatrics
American Board of Pediatrics – Hematology/Oncology
Member, American Academy of Pediatrics (AAP)
Member, American Association for Cancer Research (AACR)
Member, American Society of Clinical Oncology (ASCO)
Member, American Society of Hematology (ASH)
Member, American Society of Hematology – Committee on Communications
Member, American Society of Pediatric Hematology and Oncology (ASPHO)
Member, Children’s Oncology Group (COG)
The main focus of Dr. Allan Sison’s laboratory research is understanding how normal, non-cancerous cells in the bone marrow—also known as stromal cells—protect leukemia cells from chemotherapy. For example, Dr. Sison is studying how chemotherapy and other anti-leukemia treatments affect survival signaling between bone marrow stromal cells and leukemia cells. By doing so, he hopes to determine if these therapy-induced changes in signaling make these therapies more or less effective.
He is also testing newly developed compounds and drugs that can interrupt or even completely block these survival signals, with the hopes of making chemotherapy more potent.
Finally, Dr. Sison is also interested in leukemia-initiating cells, which are a small population of cells within a patient’s leukemia that act like stem cells. These leukemia-initiating cells are able to give rise to the entire leukemia and are also thought to be important in leukemia relapses. Specifically, Dr. Sison is interested in determining if leukemia-initiating cells respond differently to survival signals from bone marrow stromal cells.
Leukemia, a cancer of the white blood cells, is the most common cancer in children. Because of advances in the treatment of leukemia, most children with leukemia can expect to be cured with today’s chemotherapy regimens. However, an unacceptable number of children with ALL and AML are not cured by our current therapies. Many studies have suggested that non-cancerous bone marrow stromal cells are able to protect leukemia cells from chemotherapy, which can then potentially lead to treatment failure in high-risk ALL and AML. Dr. Sison hopes that a better understanding interactions between bone marrow stromal cells and leukemia cells will translate into higher cure rates for children with ALL and AML. Ultimately, Dr. Sison hopes that his research will lead directly to the development of clinical trials and new therapies for children with high-risk leukemias.
Dr. Sison’s research is focused on the bone marrow microenvironment as a mediator of chemotherapy resistance in pediatric ALL and AML, with a particular emphasis on CXCR4. Dr. Sison plans to determine the role of surface expression of CXCR4 in pediatric leukemias, evaluate upregulation of CXCR4 and other adhesion molecule receptors as a potential mechanism of therapeutic resistance in pediatric acute leukemias, undertake preclinical evaluation of CXCR4 and other microenvironment-targeted antagonists, and study interactions between leukemia-initiating cells and the bone marrow microenvironment. In his studies, Dr. Sison will focus on high-risk pediatric ALL and AML subtypes, including infant MLL-rearranged (MLL-R) ALL.