Gene fusions trigger cancer growth, could impact treatment choices
ANN ARBOR, Mich. — Researchers at the University of Michigan Comprehensive Cancer Center have discovered how genes turn on the switch that leads to prostate cancer.
The team discovered that pieces of two chromosomes can trade places with each other and cause two genes to fuse together. The fused genes then override the “off” switch that keeps cells from growing uncontrollably, causing prostate cancer to develop.
By testing these gene fusions in mice and in cell cultures, the researchers showed that the fusions are what cause prostate cancer to develop. But it’s not just one set of genes that fuse. The researchers found that any one of several in a family of genes can become scrambled and fuse. Results of the study appear in the Aug. 2 issue of Nature.
“Each of these switches, or gene fusions, represent different molecular subtypes. This tells us there’s not just one type of prostate cancer. It’s a more complex disease and potentially needs to be treated differently in each patient,” says lead study author Arul Chinnaiyan, M.D., Ph.D., director of the Michigan Center for Translational Pathology, a new U-M center whose goal is to translate research into real world practice.
The gene fusion research is the centerpiece project of the new center. In the current study, researchers found one of several abnormal gene fusions in the prostate cancer tissue samples they tested. In 2005, the researchers identified a prostate-specific gene called TMPRSS2, which fuses with either ERG or ETV1, two genes known to be involved in several types of cancer.
The Nature paper reports on five additional genes that fuse with ERG or ETV1 to cause prostate cancer. Gene fusions were involved in 60 percent to 70 percent of the prostate cancer cell lines the researchers looked at. The genes involved are all controlled by a different mechanism. For example, four of the genes are regulated by androgen, a male sex hormone known to fuel prostate cancer. Androgen deprivation is a common therapy for prostate cancer.
Knowing which gene fusion is involved in an individual patient’s tumor could impact treatment options. If an androgen-regulated gene is involved, androgen therapy would be appropriate. But if the gene fusion involves a gene that represses androgen, the anti-androgen therapy could encourage the cancer’s growth. This may also explain why androgen treatment is not effective for some prostate cancers.
“Typing someone’s prostate cancer by gene fusion can affect the treatment given. We would not want to give androgen to someone whose prostate cancer gene fusion is not regulated by androgen,” says Chinnaiyan, who is the S.P. Hicks Collegiate Professor of Pathology at the U-M Medical School.
Rearrangements in chromosomes and fused genes are known to play a role in blood cell cancers like leukemia and lymphoma, and in Ewing’s sarcoma. A fused gene combination that plays a role in chronic myelogenous leukemia led researchers to develop the drug Gleevec, which has dramatically improved survival rates for that disease.
Chinnaiyan believes the prostate gene fusions will eventually lead to similar treatments for prostate cancer.
“More immediately, we hope to develop tests for diagnosis or prognosis. But long-term, we hope this will lead to better therapies to treat prostate cancer. The key challenge is to find a drug that would go after this gene fusion,” Chinnaiyan says.
The gene fusion technology has been licensed to San Diego-based Gen-Probe Inc., which is working on a screening tool to detect gene fusions in urine. The tool could one day supplement or replace the prostate specific antigen, or PSA, test currently used to screen for prostate cancer.
The idea of translating laboratory research findings into a test or treatment that will impact patients is central to the new Michigan Center for Translational Pathology. The center brings together experts in genomics, proteomics and bioinformatics to look at common patterns and potential targets in cancer and other diseases. This is the first center of its kind in the nation in that it is associated with one of 39 National Cancer Institute-designated “comprehensive” cancer centers, a premier medical school and a large health system with both clinicians and patients.
The center’s goal is to study the genes, proteins and other markers on cells to develop new diagnostic tests or screening tools as well as targeted treatments for cancer and other diseases, with the key being to translate these laboratory discoveries into clinical applications.
Chinnaiyan and his team have received numerous awards and honors, including the American Association for Cancer Research Team Science Award for their previously published work on gene fusions, and the Specialized Program of Research Excellence Outstanding Investigator award. The new Center for Translational Pathology supported in part by the Prostate Cancer Foundation, which has offered to match up to $1 million dollars in donations to support work related to developing therapies against prostate cancer gene fusions at the university.
“Mapping of the human genome was only the beginning. Equipped with the comprehensive analysis of the human genome, we can now systematically examine the blueprint of disease at the molecular level. This essential knowledge may lead to better diagnostic tests and promising new treatments for cancer, cardiovascular disease, diabetes and other illnesses,” Chinnaiyan says.
For information about the Michigan Center for Translational Pathology, go to http://www.med.umich.edu/mctp.
About 218,890 men will be diagnosed with prostate cancer this year, and 27,050 will die from the disease, according to the American Cancer Society. The gene fusion work is not currently available for treatment or diagnosis, and no clinical trials are currently recruiting. For information about prostate cancer and currently available treatments, go to http://www.mcancer.org or call the U-M Cancer AnswerLine at 800-865-1125.
In addition to Chinnaiyan, U-M study authors were Scott Tomlins; Saravana Dhanasekaran, Ph.D.; Bharathi Laxman; Qi Cao; Beth Helgeson; Xuhong Cao; David Morris, M.D.; Anjana Menon; Xiaojun Jing; Bo Han; James Montie, M.D.; Kenneth Pienta, M.D.; Diane Roulston; Rajal Shah, M.D.; Sooryanarayana Varambally, Ph.D.; and Rohit Mehra, M.D. Mark Rubin, M.D., from Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School is also a study author.
Funding for the study came from the U.S. Department of Defense, the National Institutes of Health, the Early Detection Research Network, the Prostate Cancer Foundation and Gen-Probe Inc.
The University of Michigan has filed for a patent on the detection of gene fusions in prostate cancer, on which Tomlins, Mehra, Rubin and Chinnaiyan are co-inventors. The diagnostic field of use has been licensed to Gen-Probe Inc. Chinnaiyan also has a sponsored research agreement with Gen-Probe; however, GenProbe has had no role in the design or experimentation of this study, nor has it participated in the writing of the manuscript.
Reference: Nature, Vol. 448, No. 7153, Aug. 2, 2007
Contact: Nicole Fawcett
University of Michigan Health System
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WINSTON-SALEM, N.C. – A gene discovered by scientists at Wake Forest University School of Medicine has been linked to lupus and related autoimmune diseases. The finding, reported in the current issue of Nature Genetics, is the latest in a series of revelations that shed new light on what goes wrong in human cells to cause the diseases.
“This research is a huge leap toward understanding the cause of lupus and related autoimmune diseases,” said Fred Perrino, Ph.D., a co-author on the paper and a professor of biochemistry at Wake Forest. “There had been few clues before now.”
Perrino, who discovered the gene in 1998, said he suspected it was involved in human disease, but it took a group of researchers from around the world collaborating to put the puzzle together.
“We’ve known that lupus was a complex disease, but now we have a specific protein and a particular cellular process that appears to be one of the causes,” said Perrino. “We’re connecting the dots to understand the biology of what’s going on with the disease.”
In Nature Genetics, lead author Min Ae Lee-Kirsch, M.D., from the Technische Universität Dresden in Dresden, Germany, and colleagues report finding variations of the TREX1 gene discovered by Perrino in patients with systemic lupus erythematosus. The study involved 417 lupus patients from the United Kingdom and Germany. Mutations were found in nine patients with lupus and were absent in 1,712 people without lupus.
“Our data identify a stronger risk for developing lupus in patients that carry variants of the gene,” said Lee-Kirsch.
In recent years, the gene was also linked to Aicardi-Goutieres syndrome, a rare neurological disease that causes death in infants, and to chilblain lupus, an inherited disease associated with painful bluish-red skin lesions that occur during cold weather and usually improve in summer. The current research also links it to Sjogren’s syndrome, a form of lupus.
The diseases are all autoimmuine diseases, which means that the body makes antibodies against itself. In lupus, these antibodies cause pain and inflammation in various parts of the body, including the skin, joints, heart, lungs, blood, kidneys and brain. The disease is characterized by pain, heat, redness, swelling and loss of function.
Perrino began studying the protein made by the gene more than 14 years ago.
“We basically cracked open cells to locate the protein and find the gene,” said Perrino. “In the 14 years since, we’ve learned a lot about the protein and how it functions.”
The gene manufactures a protein, also known as TREX1, whose function is to “disassemble” or “unravel” DNA, the strand of genetic material that controls processes within cells. The “unraveling” occurs during the natural process of cells dying and being replaced by new cells. If a cell’s DNA isn’t degraded or unraveled during cell death, the body develops antibodies against it.
“If the TREX1 protein isn’t working to disassemble the DNA, you make antibodies to your own DNA and can end up with a disease like lupus,” said Perrino.
Perrino and colleagues at Wake Forest have been studying the gene and its protein since 1993. Thomas Hollis, Ph.D., an assistant professor of biochemistry at Wake Forest, is credited with solving the structure of both TREX1 and a similar protein, TREX2. Perrino has also developed a way to measure the function of the proteins.
In a study reported in April in the Journal of Biological Chemistry, Hollis and Perrino found that three variations of the gene reduced the activity of the protein by four- to 35,000-fold.
“Now that we have the structure, we can understand how it disassembles DNA and how mutations in the gene may affect that process,” said Hollis.
The researchers hope that understanding more about the gene’s mutations and the structure of the protein may lead to drug treatments to help ensure that mutant copies of the gene are inactive.
Media Contacts: Karen Richardson, firstname.lastname@example.org; Shannon Koontz, email@example.com; at 336-716-4587.
Wake Forest University Baptist Medical Center is an academic health system comprised of North Carolina Baptist Hospital and Wake Forest University Health Sciences, which operates the university’s School of Medicine. U.S. News & World Report ranks Wake Forest University School of Medicine 18th in primary care and 44th in research among the nation’s medical schools. It ranks 35th in research funding by the National Institutes of Health. Almost 150 members of the medical school faculty are listed in Best Doctors in America.
Contact: Karen Richardson
Wake Forest University Baptist Medical Center
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