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Research Q&A: Identifying cancer’s source

The Asarum caulescens plant used in traditional Chinese medicine contains known carcinogens tied to bladder cancer. Photo: KENPAI/CC

In a case of “what caused the cancer?” University of Minnesota scientists are aiming to find out if diet or environmental exposures to hazardous chemicals from a person’s past can be linked to a patient’s cancer today.

Health Talk recently sat down to discuss a noteworthy discovery made in the lab of researcher Robert Turesky, Ph.D., and postdoctoral fellow Byeong Hwa Yun, Ph.D., while the tandem were at the New York State Department of Health’s Wadsworth Center.

Turesky and Yun recently joined the Masonic Cancer Center, University of Minnesota, research team. Turesky is also a University of Minnesota College of Pharmacy professor.

Health Talk: Why investigate environmental or dietary contributors to cancer?
Turesky: Right now, if you smoke and develop a lung cancer that’s been linked to smoking tobacco, your doctor might identify smoking as the likely cause… and that’s a pretty good deduction.

Your doctor might also test a fresh, frozen sample of cancerous tissue taken during a biopsy and say that your DNA looks like it was damaged by chemicals found in cigarettes. Again, he’d tell you that smoking probably contributed to your cancer.

But what if you never smoked and lung cancer didn’t run in your family? What if a dietary or environmental factor was linked to your cancer? (For example, despite smoking, the lung cancer could be connected to radon.)

Up until now we haven’t been able to readily identify cancer’s cause at the chemical level in many cases.

HT: So what did you find?
Turesky: We found what researchers have been trying to do for years.

Using mass spectrometry, we identified DNA damage induced by Aristolochic acid – a chemical found in the Aristolochia and Asarum plants of traditional Chinese medicine – in wax samples from a tissue bank. The samples were taken from patients with bladder cancer who consumed herbal plants containing Aristolochic acid.

Currently, when we run tests on biopsy tissue to help identify what might be causing cancer, we look for chemicals that may have latched onto a cell’s DNA, which may have started the development of cancer. We look for DNA lesions. Until now, such measurements could only be obtained from fresh, frozen cancer tissue samples… and those biospecimens aren’t usually easy to obtain for investigations in large-scale human studies.

We established a new technique to remove crosslinks from DNA preserved with formalin from cancer tissue. We discovered a unique chemical found in these people’s diet that is likely to have caused their cancer. That’s big news because we haven’t been able to do that with tissue samples embedded in wax  (something that exist in tissue banks across the world) ever before.

HT: What are the implications of that finding?
Turesky: Firstly, it may help epidemiologists add another piece of data to their tool kit to help assess carcinogen exposure and take into consideration other cancer-causing chemicals we might not have known about. It will help lessen the uncertainty around exposures to hazardous chemicals and the potential causes of some people’s cancer when there isn’t a fresh, frozen tissue sample available.

Secondly, while this test does require expensive equipment, it’s good to know that the technology is there and biomonitoring methods can be done. The technique opens up the opportunity for future refinement and cost-reduction, particularly, if we can test for other carcinogens and their DNA damage in this way too.

HT: What’s the next step you’re taking into U of M labs?
Turesky: The next step is to find out if we can apply our techniques to detect DNA damage in urinary bladder cancer and other organs to other kinds of cancer caused by charred meat, tobacco or air pollution. We want to learn how versatile this method is and how robust the technique is to look for other carcinogens and their DNA damage implicated in other types of human cancer.

 

 

Learn more about the finding in this April 2013 Chemical & Engineering News article (login required).

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