A new version of a popular test for cancer-causing agents is cheaper, more sensitive and, best of all, animal-free, thanks to a U of G researcher. Prof. David Josephy, Chemistry and Biochemistry, has developed a way of testing substances for cancer-causing potential without using animal tissue. Instead, his version of the Ames test involves gene splicing.
“Nobody has figured a way around using animals until now,” says Josephy. “We hope that no more animals will have to die for the sake of the Ames test.” Two decades ago, the Ames test (named after inventor Bruce Ames, a bacterial geneticist from the University of California at Berkeley) was heralded as a breakthrough in cancer research. Ames’s goal was to eliminate the use of animals in tests for cancer-causing or “mutagenic” agents.
In his efforts to put an end to animal use, Ames came up with a way to use animal tissue for his tests, rather than the whole animal. In animals, cancer-causing agents are inactive until they’re chemically changed or “metabolized” by certain enzymes. When they’re changed, they become dangerous because they’re converted into different forms of chemicals.
Ames chose rodent liver extracts for his test because the liver contains more metabolic enzymes than other organs do. In a test tube, he combined liver cells and bacteria. He used bacteria because they’re so small that billions of cells can be affected by the mutagen in one test, making results easier to observe. When a potential cancer-causing agent is introduced into the test tube, it’s metabolized by the enzymes in the liver and causes DNA damage or mutations to the bacterial cells. DNA damage mutates cells, which results in cancer in animals.
The test has enabled researchers to identify carcinogens such as the charring on burnt food and a chemical used to fireproof children’s pyjamas, which was banned after the discovery was made. The Ames test used only a portion of a rodent’s liver. That meant it reduced the use of animals needed to detect suspected mutagens because one liver provided enough material for hundreds of tests. With the Ames test, mutagen-detection laboratories need to use only a few dozen rodent livers each year instead of the thousands of animals that lifetime feeding tests would require.
Now Josephy has taken that a step further. He has completely eliminated the need for animals to be involved. In the last few years, researchers have identified the gene — called P4501A2 — that makes the enzyme needed to metabolize carcinogens so they become mutagenic. Different enzymes metabolize different carcinogens; the enzyme P4501A2 metabolizes one class of compounds called aromatic amines, the carcinogens in charred material.
Josephy spliced the P4501A2 gene into the bacterial cell responsible for producing the metabolizing enzyme that identifies it as a mutagen. By splicing the gene into the bacteria, he’s made it possible for the bacteria to produce the required enzyme, so that no rat liver is needed. As a result, when potential mutagenic chemicals are introduced, the bacteria are a complete mutagen-detecting package in themselves.
Josephy has installed a clone of the human P4501A2 gene into the bacteria to make the test even more representative of human metabolism. The cloned human genes come from Peter Guengerich, a collaborator at the Vanderbilt University School of Medicine in Nashville. “It means we can do a much more sophisticated mutagen analysis than we could in the past,” says Josephy. “We’re fulfilling Ames’s goal.” This work is sponsored by the National Cancer Institute of Canada and the Natural Sciences and Engineering Research Council.
More men are developing breast cancer – but most fail to spot tumours until they are at an advanced stage, a study has warned. University of Texas research found that, while men are far less likely to develop breast tumours than women, the numbers are increasing. Writing in an online edition of the journal Cancer, they warn men seem to be unaware they can develop the cancer.
LOS ANGELES- the Postal Service unveiled the design of the Breast Cancer Research “Semipostal” Stamp, here, at the Revlon Run and Walk for Women on May 9th. A nationwide issuance of this self-adhesive stamp begins in early August.
Breast Cancer Research Semi-postal Stamps are subject to special limitations and conditions:
What if the knowledge that scientists might have gained about the cancer-like tree disease referred to below could have led to a cure for human cancer?
I am not sure if you have or haven’t heard about this. Next summer there will be a cross-Canada run that will be in the fund-rasing spirit for fighting breast cancer. Janet Blades proposed thata similar venture be taken in the US as well, at the same time as the Canada run. I responded, but alas I am inundated with school and cannot be of any use it seems. So I will pass the word on, and any brave souls wishing to take up this cause may do so. Please email me or Janet (I don’t think she’ll mind – if she does blame me) about any questions, but Janet’s the one to really turn to for answers.
Help Make Prostate Cancer Research a National Health Priority!
Santa Rosa Memorial Hospital has been selected to take part in what doctors said is a promising 10-year national study on whether vitamin supplements can help prevent prostate cancer, the second leading cause of death for men.
