Azurin Triggers Death of Cancer Cells in Mice

Researchers have found that the bacterial protein azurin induces apoptosis in cancer cells by stabilizing p53 protein in the cytosol, which allows p53 to reach a concentration that triggers the sequence of biochemical events leading to the death of the cell. This finding was published in the October 29, 2002, issue of the Proceedings of the National Academy of Sciences.

Azurin is a relatively well-studied protein isolated from the growth medium of Pseudomonas aeruginosa. Since P aeruginosa survives by killing macrophages, researchers from the University of Illinois, Chicago (USA; www.uic.edu) tested the possibility of applying this ability to the destruction of cancer cells.

Immunodeficient mice implanted with human melanoma were treated with half a milligram of azurin daily for 22 days. At the conclusion of the trial, the average size of the tumors in these mice was 60% smaller than those in untreated mice. None of the mice showed signs of illness or loss of weight.

Azurin was found to stabilize the p53 protein, a product of the tumor suppressor p53 gene. Normally, the p53 protein is rapidly destroyed in the cytosol. However, azurin transported into the nucleus of the tumor cell binds to the p53 protein and protects it from degradation, thus raising its level within the cell.

According to Dr. Tapas Das Gupta, a co-investigator and head of surgical oncology at the University of Illinois, preliminary data show that azurin kills several types of cancer cells, including breast and colon cancer. "These results suggest that azurin could be a useful anticancer agent not just for melanoma but for different kinds of tumors,” said Dr. Das Gupta.

"Bacterial proteins could well be a new weapon in the war against cancer,” said Dr. Ananda Chakrabarty, professor of microbiology and immunology and senior author.




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