Insights on Tumor Growth Lead to New Treatments
February 17, 2017 - WebMD
Recent discoveries that shed light on how tumors grow are giving doctors new tools to fight cancer. It's just the beginning and there's a long way to go, experts say, but they're hopeful about the future of cancer treatment.
The Role of Genes in Cancer
In 2003, scientists completed the Human Genome Project, which gives a clear map of what our DNA looks like and how it tells our genes what to do. This had a big impact on understanding cancer.
"Cancer is a disease of genes," says Jean Claude Zenklusen, PhD, director of the National Cancer Institute's Cancer Genome Atlas. "When the genome was open, we could suddenly take a magnifying glass and look at the DNA of tumor cells."
While scientists had known genes played a role in cancer, mapping out the sequence of DNA helped them see what was normal and what wasn't. Now they can pinpoint problems with genes that are linked to cancer and see how cells interact to spark tumor growth.
The new insights help doctors use "targeted therapy" to fight cancer. They can prescribe drugs that zero in on specific parts of cells that trigger the growth of tumors.
"If you can identify the main genes, you can turn the genes off," says Alexander Spira, MD, PhD, director of the Virginia Cancer Specialists Research Institute. For example, people with lung cancer often have a mutation, or change, of the EGFR gene. Now doctors have drugs that target the way that gene works.
Cancer and Our Immune System
Scientists have recently pulled the curtain back on how the immune system -- your body's defense against germs -- responds to cancer. The research has opened the way to developing new drugs that give your immune system the power to attack cancer. It's an approach called immunotherapy.
When left to its own devices, the immune system often has trouble targeting cancer cells. Sometimes, its response is too weak to help. Other times, it simply doesn't recognize cancer cells. And some cancer cells trick immune cells into ignoring them.
"If you look at a picture of a tumor, there are a lot of immune cells within the tumor," Zenklusen says. "The immune system is trying to do something, but it's not effective."
Scientists recently discovered that some tumors have a receptor that should be a red flag that tells immune cells to get to work, but instead it fools them. "It tells them, 'Yes, I look funny, but you shouldn't worry,' " Zenklusen says.
Since discovering the receptor, scientists have created antibodies to stop it. "We can block the receptor. Then the immune system can respond -- and it responds like gangbusters. It's incredible," he says.
Immunotherapy doesn't work for everyone or for all types of cancer. It's been most successful in treating lung cancer, head and neck cancers, and Hodgkin's lymphoma. But early results are promising. Zenklusen says it works for about 20% of people with cancer.
Doctors now have an assortment of immunotherapy drugs to choose from, and more are getting tested in studies.
There's still plenty of work to be done. "While our knowledge of cancer genetics has exploded, the actual application of that knowledge to benefit patients hasn't caught up," says Hao Zhu, MD, an associate professor at the UT Southwestern Children's Medical Center Research Institute.
Figuring out who will benefit from targeted treatment and immunotherapy is an important next step, he says. And more types of tumors need to be studied in depth.
Researchers still need to make more progress in understanding individual differences. "Not all people will respond to medication in the same way," Zenklusen says.
The next frontier is to develop treatment that's tailored for different people. It will open up new ways to help people who don't respond to the drugs they take or find that their medicines stop working after a while. A personalized approach could bring new breakthroughs in cancer treatment in the years ahead.
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