When researchers in this study sequenced just the genes that were switched on in the AMKL cells of 14 young patients, the scientists discovered half carried the CBFA2T3-GLIS2 fusion. Additional fusion genes were identified in five of the other patients. Each of those fusion genes occurred in a single patient. The genes involved included HOXA9 and MN1, both previously linked to leukemia, and GATA2 and FLII, which play roles in normal development of the megakaryocytic blood cells that are targeted in AMKL. Megakaryocytes produce the platelets that help blood clot.
Additional sequencing of DNA from adult and pediatric AMKL patients, including whole genome sequencing of the normal and cancer cells of four young AMKL patients, found the CBFA2T3-GLIS2 protein was unique to pediatric AMKL. Of the 48 pediatric AMKL patients screened in this study, 13 carried the fusion gene. None of 28 adult AMKL patients screened had the gene.
"Whole genome sequencing has allowed us to detect alterations in cancer cells that were previously unknown. Many of these changes contribute directly to the development of cancer," Gruber said. "Such sequencing also provides the deeper understanding of the disease that is critical for developing more effective, less-toxic targeted therapies."
GLIS2 is a transcription factor, meaning it attaches to DNA and turns genes on or off. GLIS2 is normally switched off in blood cells and has not been previously linked to cancer.Working in several laboratory models, researchers showed that GLIS2, either alone or in the fusion gene, increased the activity of other genes in pathways that control cell functions disrupted in cancer. The genes include BMP2 and BMP4, which are now the focus of additional research. The genes are in a pathway that is active early in the developing blood system. This study implicated the genes in AMKL. The study's other authors are Amanda Larson Gedman, Jinghui Zhang, Cary Koss, Suresh Marada, Shann-Ching Chen, Stacey Ogden, Jinjun Dang, Gang Wu, Stanley Pounds, Lei Shi, John Easton, Heather Mulder, Michael Rusch, Matthew Parker, Jing Ma, Sheila Shurtleff, Jeffrey Rubnitz and Ching-Hon Pui, all of St. Jude; Huy Ta, Vedant Gupta, Anna Andersson, Michael Barbato, Jayanthi Manne, Jianmin Wang, Ramapriya Ganti and Ina Radtke, all formerly of St. Jude; Xiaoping Su, Steven Kornblau, Farhad Ravandi and Hagop Kantarjian, all of MD Anderson Cancer Center, Houston; Swati Ranade, Pacific Biosciences, Menlo Park, Calif.; Li Ding, Timothy Ley and Elaine Mardis, all of Washington University; Giovanni Cazzaniga and Andrea Biondi, both of University of Milan-Bicocca, Monza, Italy; Stephen Nimer, Sloan-Kettering Institute, New York; Konstanze Dohner and Hartmut Dohner, both of University of Ulm, Germany; Paola Ballerini, Hospital Armand-Trousseau, Paris; Daisuke Tomizawa, Tokyo Medical and Dental University; Souichi Adachi, Kyoto University, Japan; Yasuhide Hayashi, Gunma Children's Medical Center, Japan; Akio Tawa, Osaka National Hospital, Japan; Lee-Yung Shih, Chang Gung University, Taipei; and Der-Cherng Liang, Mackay Memorial Hospital, Taipei. The research was funded in part by the Pediatric Cancer Genome Project, including Kay Jewelers, a lead project sponsor; the National Institutes of Health (P30CA021765); the Eric Trump Foundation; a Leukemia & Lymphoma Society Specialized Center of Research grant and ALSAC.