October 16, 2009
Breast Cancer DNA Completely Sequenced

Scientists have begun doing complete genome sequencing of tumor cells from cancer patients.

Scientists have sequenced the genomes of two tumors from the same breast cancer patient--a primary tumor and a metastatic tumor that occurred nine years later--illuminating some of the genetic changes that trigger the progression of cancer. The initial findings suggest that both primary cancers and the process of metastasis--the spread of cancer cells--are more complicated and more variable than expected, which means that successful cancer treatment might ultimately require a combination of drugs targeted to different mutations.

The project is also a testament to how easy it has become to sequence a human genome. The researchers, from the British Columbia Cancer Agency, in Vancouver, now plan to sequence the tumor genomes of more than 250 additional patients over the next year. "We are sequencing dozens of tumors a week now," says Samuel Aparicio, the scientist who led the study.

The decline in DNA sequencing costs from hundreds of millions of dollars per person to several thousands of dollars has suddenly made many types of scientific investigation possible. By doing sequencing of tumors at different stages in large numbers of patients scientists will develop a much better picture of which mutations occur in people to cause their cancers become more malignant and deadly. This will lead to treatments aimed at the most deadly mutations.

The amount of data involved in this sort of research is enormous. Each sequencing turns up data for a few billion DNA letters. A cancer patient could get sequencing done at each stage of their cancer. With about 1.6 million people in the United States alone suffering from cancer the total amount of complete genome sequencing that will get done just for cancer patients will equal at least that number per year in order to track existing cancers thru stages of development.

Share |      Randall Parker, 2009 October 16 12:01 AM  Biotech Cancer

Engineer-Poet said at October 17, 2009 10:01 PM:

I suppose the next step is to anticipate the mutations the cancer will make to metastasize or evade a therapy, and hit it with drugs which kill cells which make those changes.  Kind of like combination therapy for HIV.

Randall Parker said at October 17, 2009 11:55 PM:

E-P, Yes, I expect combination therapy in order to attack multiple mutations at once. It makes sense to attack mutations that haven't happened yet. That way synergy from mutations doesn't build up.

One problem with combo therapy is the sheer number of possible mutations that can help cancer spread. It a dozen or two dozen drugs be necessary? Does toxicity become a problem?

Another approach is gene therapy that reverses the effect of harmful mutations. Or, better yet, gene therapy that selectively kills cells that have key cancer-causing mutations.

not anon or anonymous said at October 18, 2009 11:22 AM:

It a dozen or two dozen drugs be necessary? Does toxicity become a problem?

If combination therapy turns out to be useful, we'll probably develop special drugs that can provide the desired effects while keeping toxicity under check. We're not going to administer a dozen drugs to each cancer patient.

And yes, once genome sequencing becomes cheap enough, we're probably going to track cancer mutations in the lab and develop a better picture of these resistance mechanisms.

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