Factor boosting leukemia's aggressiveness identified

"The microenvironment is the term used to describe the cells that cluster around CLL cells in the lymph nodes, spleen and bone marrow. These cells secrete factors that can protect CLL cells from dying," said Thomas J. Kipps, MD, PhD, Evelyn and Edwin Tasch Chair in Cancer Research, Professor of Medicine, Deputy Director of Research Operations at the Rebecca and John Moores UCSD Cancer Center and senior co-author of the paper with Michael Karin, PhD, Distinguished Professor of Pharmacology in UCSD's Laboratory of Gene Regulation and Signal Transduction.

Kipps, Karin and colleagues from Iowa, The Netherlands and Taiwan looked specifically at a protein called B-cell activating factor or BAFF, which is produced in high levels by "nurselike cells" in the CLL microenvironment. Nurselike cells are a subset of blood cells in CLL patients that help cancer cells avoid apoptosis or natural cell death. Kipps and colleagues first described this relationship in 2000.

The researchers found that BAFF interacts with a gene linked to leukemogenesis -- the development of leukemia -- called c-MYC. Normal MYC genes help regulate cell proliferation, but when upregulated or increased by mutations, c-MYC can promote more aggressive leukemias and lymphomas. To what degree this relationship influences CLL -- the most common form of adult leukemia -- remains unknown, though Kipps said the findings suggest therapeutic promise.

"We found that BAFF can upregulate expression of c-MYC in CLL cells and that patients who have CLL cells with high levels of c-MYC have aggressive disease," said Kipps. "These findings may lead to improvements in our ability to treat patients with CLL, either by blocking the effect of BAFF on CLL cells or inhibiting the signaling pathways triggered by BAFF that can lead to upregulation of MYC."

Co-authors of the paper include Weizhou Zhang of the Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, UC San Diego School of Medicine and of the departments of Medicine and Radiology at Moores UCSD Cancer Center; Arnon P. Kater of the Department of Hematology, Academic Medical Center, The Netherlands; George F. Widhopf II, Han-Yu Chuang and Danelle F. James of UCSD's Department of Medicine; Thomas Enzler of Department of Medicine, Stanford School of Medicine; Maxim Poustovoitov of the Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology and UCSD School of Medicine; Ping-Hui Tseng of the Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taiwan' Siegfried Janz of the Department of Pathology at the University of Iowa Carver College of Medicine; Carl Hoh of UCSD's Department of Radiology and Harvey Herschman of the departments of Biological Chemistry and Pharmacology, UC Los Angeles.

Funding for this project was provided by the National Institutes of Health and a grant from the Leukemia and Lymphoma Society Specialized Center of Research.