Signaling Protein For Multiple Myeloma Identified, Findings May Result In New Therapeutic TargetArticle Date: 12 Sep 2007 - 8:00 PST
http://whsc.emory.edu/press_releases2.cfm?announcement_id_seq=11503Researchers at Emory University's
Winship Cancer Institute are the first to discover a mechanism that plays a critical role in the multiple
myeloma cell cycle and survival. Their research may result in identification of a new therapeutic target for treating multiple
myeloma.
The results of the study appear in the September issue of Cancer Cell.
Jing Chen, PhD, assistant professor of hematology and oncology at Emory
Winship and a Georgia Cancer Coalition Distinguished Cancer Scholar, is senior author on the paper.
Sumin Kang, PhD, a postdoctoral fellow at Emory
Winship, is the paper's first author.
Multiple
Myeloma is among the most common hematologic malignancies in patients over 65. About15 percent of multiple
myeloma patients harbor a genetic abnormality called "t(4;14) chromosomal
translocation" that causes over-expression of a tyrosine
kinase called fibroblast growth factor receptor 3 (
FGFR3).
Tyrosine
kinases are molecules that act as biological switches inside cells, regulating processes including cell division and growth. Abnormal
kinases have been identified as a driving force in many forms of cancer.
"We are interested in how
FGFR3 mediates transforming signals," says Dr. Chen. "We wanted to know which protein factors in cells are activated by
FGFR3 and then transform normal cells to highly malignant cells. We identified
Ribosomal S6
kinase 2 (
RSK2), which is a protein factor that mediates signaling in cells as critical in downstream signaling of
FGFR3 in
myeloma cells."
Dr. Chen and his colleagues are the first to discover a mechanism to "turn-on"
RSK2 by
FGFR3.
FGFR3 impacts downstream proteins through
phosphorylation at special "tyrosine" sites.
"We found that
FGFR3 directly
phosphorylates RSK2, which is a critical step in the process to activate (turn-on)
RSK2," says Dr. Chen.
The researchers observed that elimination of
RSK2 proteins or shutting down
RSK2 activity blocks
FGFR3 transformation signaling in
myeloma cells. This means
FGFR3 requires
RSK2 to transform normal cells.
"This is a beautiful model," says Dr. Chen. "We are able to mark the connection between the
oncogenic FGFR3 and its downstream protein
kinase RSK2, which plays a critical role in regulation of cell cycle and survival. These findings extend our understanding of pathogenesis of multiple
myeloma in a signaling basis."
Collaborators on the project include Roberto
Polakiewicz, PhD, and Ting-Lei
Gu, PhD, both of Cell Signaling Technologies (CST), developers of the "
PhosphoScan" technology, which enables investigators to identify hundreds to thousands of
phosphorylated sequences and observe the global state of protein tyrosine
phosphorylation in cells and tissues.
"Using this technology," says Dr. Chen, "we identified
RSK2 as a critical downstream signaling protein effector of
FGFR3 in
myeloma cells." Other authors include researchers from the University of California at San Francisco, Harvard Medical School, Mayo Clinic and
Novartis Pharma AG.
Dr. Chen and his colleagues also tested a drug called
fmk that was designed by co-author Jack
Taunton, PhD, at UCSF to specifically target
RSK2 in treatment of human malignant
myeloma cells from laboratory culture or primary samples from multiple
myeloma patients, and saw that
fmk effectively kills t(4;14)
myeloma cells with abnormal over-expression of
FGFR3.
"This study shows the potential utility of drugs that block the downstream effectors of mutant tyrosine
kinases, and that these drugs are opening more doors to treating hematologic malignancies and cancers," explains Dr. Chen. In addition to the t(4;14) in multiple
myeloma that is caused by abnormal over-expression of
FGFR3, abnormality of
FGFR3 has also been identified in human bladder and cervical cancers. The findings suggest, the authors write, that targeting
RSK2 with
RSK inhibitors such as
fmk may be effective in treating t(4;14) multiple
myeloma, as well as other diseases and cancers where mutant
FGFR3 is the culprit.
----------------------------
Article adapted by Medical News Today from original press release.
----------------------------
The research was supported by grants from the National Institutes of Health, the Leukemia and Lymphoma Society and the Multiple Myeloma Research Foundation.About Emory
Winship Cancer Institute: As a leader in cancer patient care and research, Emory University's
Winship Cancer Institute (
EWCI) offers new therapies not usually available outside university-affiliated medical centers, including nearly 150 clinical trials for all types and stages of cancer. The
EWCI serves as the coordinating center for a vast array of resources in medical, surgical and radiation oncology, diagnostic imaging, and the
subspecialties of cancer care throughout Emory University -from blood and bone marrow stem cell transplants to internationally recognized breast reconstruction. For more information, visit:
http://www.cancer.emory.edu/.
Source: Vincent
Dollard Emory University Article Date: 12 Sep 2007 - 8:00 PST