There really is something good about Pseudomonas

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Bacteria protein kills cancer cells

BYLINE: By MARCELLA S. KREITER

Researchers at the University of Illinois at Chicago reported

Tuesday they

have found a protein produced by bacteria that kills cancer cells in

mice.

In research published in the Oct. 29 issue of the Proceedings

of the National

Academy of Sciences, the researchers said they took bacteria that

causes serious

respiratory problems in human patients with cystic fibrosis and burn

injuries

and used it to kill human melanoma cells that had been implanted in

specially

bred mice.

The bacteria produce a protein called azurin that actually

unites with the

natural cancer-suppressing protein p53 to stabilize the latter and

increase its

activity, said Ananda Chakrabarty, professor of microbiology and

immunology.

" It's been known for a long time that when people get infected,

their tumors

regress, " Chakrabarty said. " The problem is that the infection can't

be allowed

to go on. It will kill them. When drugs are used to remove the

infection, the

tumor will come back. It is generally believed such regression of

tumors is due

to activation of immune system. "

By using only the azurin protein molecule rather than the whole

bacterium,

however, the effects of infection are eliminated and only the

cancer-fighting

properties are left.

For their study, the investigators used the bacterium

Pseudomonas aeruginosa,

which is known to be resistant to antibiotics. It protects itself

from

destruction by killing macrophages, the cells representing the immune

system's

first line of attack against a foreign body.

They implanted human melanoma cells into specially bred

immunodeficient mice

and injected the tumors with azurin, purified from P. aeruginosa.

Chakrabarty

said the azurin enhances p53's ability to make cancer cells die.

After 22 days,

the tumors had shrunk by an average of 60 percent.

If the experiment had been allowed to continue, Chakrabarty

explained, the

tumors likely would have been eliminated altogether. He said the

researchers

also tested azurin on breast cancer cells and achieved a 50 percent

reduction in

tumors in a similar timeframe. Tests also were conducted on colon and

lung

cancer cells, with some success.

Azurin is not the only bacteria-produced protein under study,

Chakrabarty

said, and it is possible a combination of such proteins or a

combination of

proteins and chemotherapy drugs could result in a new and effective

weapon

against cancer. " This kind of protein is produced by many bacteria, "

he said.

Bacteria first were observed as a cancer-fighting agent in 1893

by a New York

doctor treating bone cancer patients. Dr. Coley noticed

patients who

contracted bacterial infections survived longer. More recent,

researchers at

s Hopkins University used bacteria that survive without oxygen to

destroy

the hard cores of tumors where radiation and chemotherapy had proven

ineffective. However, the mice in those experiments died, either from

the

toxicity of the bacteria or because of something released by the

dying cancer

cells.

" Our research suggests we can achieve a therapeutic outcome

using bacterial

proteins, without toxicity associated with live bacteria, "

Chakrabarty said. " We

are hopeful a variety of other human cancers might also be

susceptible to the

anti-cancer activity of this protein. "

Phase 1 tests in humans still are at least two years off,

however, and if

such tests prove effective and non-toxic, further testing is at least

three

years off, he said.

Dr. Inder Verma, a professor in laboratory of genetics at the

Salk Institute

in San Diego, called the findings interesting but noted numerous

questions still

need to be answered, including how the protein would be delivered to

cancer

cells within the body.

" You can't inject each tumor cell with the protein, " Verma told

UPI. " The

idea is there. The question is how you deliver this gene product into

the cell

because the cells that do not get it will not die. ... If one cell

does not die,

the cancer will come back. "

The other question, he said, is what happens to cancer cells in

which the p53

protein already has mutated.