Scientists find new mechanism that causes cancer

Washington: Scientists have discovered a key
chemical process in the body which sometimes goes wrong and
causes cancer, a finding that could lead to the development of
new drugs and therapies to treat such disease.

Researchers at Brown University and Rhode Island Hospital
in the US found that prolactin receptors -- membranes proteins
that play a vital role in cellular communications -- are like
cellular wiring and susceptible to short circuits that can
cause cancer.

Prolactin receptors, which stimulate the mammary glands
in women to produce milk, are also found in other organs
including the lung and the colon.

The researchers, who detailed their study in the journal
Proceedings of the National Academy of Science, found the
chemical reaction inside the cell, called "acetylation", is
triggered by the binding of the arrival of the prolactin
hormone at the receptor.

This process can draw prolactin receptors together into a
structure called a "dimer". Like a pair of chopsticks, this
dimer structure is just right to pick up growth factors in the
body that can lead to cancerous growth, said Y Eugene Chin of
the Warren Alpert Medical School of Brown University.

"Our findings may provide an important clue about how to
develop drugs to break down receptor dimers in breast cancer
therapy," said Chin, a senior author of the study that also
involved researchers from Zhejiang University School of
Medicine in China and the University of Rochester in New York.

Normally, a shared positive electrical charge and the
resulting mutual repulsion keeps prolactin receptors from
coming together.

In their experiments, the team found that when prolactin
binds to the receptors outside the cells, the acetylation
neutralises that charge on the receptors inside the cells,
allowing the receptor molecules to come together, Chin said.

The more prolactin receptors a cell has, the more
susceptible it is to this problem occurring, Chin said.
Overexpression of prolactin receptors in patients has been
linked to cancer in the past.

Chin, who has been investigating the molecular basis of
cancer for years, said he was encouraged about uncovering this
new step and pointed to drugs, such as Herceptin, that target
receptors to combat cancer.

"This will be extremely important for breast cancer and
other cancer therapy by targeting receptors," he said.

One possibility, he said, will be developing monoclonal
antibodies to target the prolactin receptors directly. But
artificial compounds could also be developed to block the
receptors from joining as dimers.


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