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Last Updated: Nov 19th, 2006 - 12:21:58 |
8 Sep, (foodconsumer.org) - Scientists have unraveled about 200 genes that play a major role in the development of breast cancer and colorectal cancer. This genetic map promises to be a major breakthrough in the fight against cancer.
Researchers hope that the finding of these cancer-causing genes will one day herald in a new era in gene-targeted cancer therapies. Previous studies found specific cancer-causing genes and chromosomes. But the new study shoes that various genetic routes all lead to the same end result of a malignancy.
Cancer is the unhindered growth of certain cells that seem to have lost the ability to die out naturally. It is a generally accepted fact that genes are involved in causing cancer. For example, mutations in BRCA1 and BRCA 2 genes signal a greater risk for the development of breast cancer.
In the current study, researchers from Howard Hughes Medical Institute (HHMI), Johns Hopkins University, Case Western Reserve University School of Medicine, and a team of researchers from The Kimmel Cancer Center at Johns Hopkins, focused on mapping out all genetic variations that could lead to development of breast and colon cancer.
Breast and colorectal cancers are the leading cause of cancer deaths and account for more than 2 million cancer cases and around 940,000 deaths worldwide, according to the American Cancer Society.
Cancer is triggered off by multiple genetic mutations that together exceed the body's capacity to fight the attack. Although researchers have identified major culprits, many minor genetic alterations that collectively account for cancer remain unknown.
For the present study, researchers identified 13,000 genes found in 11 breast tumors and 11 colorectal tumors that had been preserved for study. They then turned their attention to alterations in the genes found in cancer when compared to normal tissue.
This result was then crosschecked the result with an additional bank of tumors from 24 breast or colorectal cancers.
The team found far more mutated genes in tumor cells than they had expected. They found 189 genetic mutations in the tumors, which are suspected to be involved in causing cancer. The main point was that these genes were never implicated in cancer previously. The findings were released in the September 8, 2006, issue of Science.
"Only by understanding this blueprint of cancer will we be fully able to understand the mechanism of what makes a cancer a cancer and to think about strategies for diagnosis, prevention and therapy," said Dr. Victor Velculescu, senior researcher on the project and an assistant professor of oncology at Johns Hopkins University's Kimmel Cancer Center.
“Scientists who have seen these data have told us that it keeps them up all night thinking,” said Bert Vogelstein, a co-researcher in the study. “It will hopefully open up a large number of opportunities in many areas of cancer research.”
The researchers had theorized that they would find a maximum of 90 mutations that alter protein structure. Through crosschecking, the researchers identified an average of 11 genes in each cancer that were most likely involved in how the cancer presented itself. Approximating this to the human genome, the researchers say an average of about 17 genes are expected to have critical involvement in the development of each cancer.
The researchers found another startling fact. No two cancers were similar even if the genes were the same, meaning that different genes presented in different ways for the same type of cancer in different individuals. The genes contributing to breast cancer were different from those mutated in colorectal cancers
“It presents a whole new view of the neoplastic process,” said Vogelstein, “and explains the heterogeneity that clinicians have long noted to exist among cancer patients.”
"Work from the past two decades has shown us that cancer is a genetic disease," said Velculescu. "A mutation is really like a typo in a blueprint that's 3 billion letters long." But despite the complexity of the task, the researchers were able to discover that many of the genes that are mutated are involved in pathways thought to be important in cancer.
For example flaws in genes is directly linked to altering cell adhesion, movement, and signaling. Each of these pathways relies on multiple genes, and flaws in any of the genes in a pathway may have similar consequences, the researchers explained.
“By taking a systems biology approach to connect these genes, we suspect that the complexity will be less than it appears at first sight,” said Vogelstein.
“The same 10 or 20 pathways may be altered in every cancer, though the particular mutated genes in these pathways will be different. The picture will become much clearer as the function of these genes and the ways they interact are better worked out.”
Velculescu added that many mutated genes in the breast cancers and colorectal cancers had a common function as far as causing cancer was concerned. He said that this finding may aid in the development of drugs that interfere with these functions or processes. "Simpler themes emerge within the complexity," he said.
This study is a prelude to a $100 million federal initiative to chalk out a Cancer Genome Atlas by the US National Human Genome Research Institute and the National Cancer Institute.
Velculescu said the finding that many genes were involved in cancer was surprising. "Colon and breast cancers are different, and, in addition, each individual's cancer is different. This, in part, may explain the differences that clinicians for a long time have seen among their cancer patients," he observed.
Dr. Len Lichtenfeld, deputy chief medical officer at the American Cancer Society described the study as an important achievement. "This achievement is important because, to the degree that those genes are proven now to be related to the cancer process, they provide targets that can be potentially used either for diagnostic or treatment purposes," he added.
Lichtenfeld said that the study had given valuable pointers to drug developers who can target specific genes and their proteins to create treatments that stop a cancer without the patient suffering. "So, this new achievement is a really important step and an important link between where we are today and where we have been talking that we will be in five, 10, 15 years," he said.
The American Cancer society says that in the US, breast cancer is expected to strike more than 200,000 women and kill nearly 41,000 this year alone. Colorectal cancer is expected to strike nearly 150,000 Americans and kill more than 55,000 this year. This finding may be of monumental significance to cancer sufferers in the future.
"Just as sequencing the human genome laid the groundwork for subsequent research in genetics, these data lay the foundation for decades of research on colon and breast cancers, " said Velculescu. "We're not there yet, and there's still a long way to go. But without knowing what's broken inside a cancer cell, we have no hope of fixing it."
© 2004-2005 by foodconsumer.org unless otherwise specified
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