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- PORTLAND, Ore. (AP) - Cyclosporine, a drug given to transplant patients
to prevent organ rejection, may turn pre-existing cancer more aggressive,
researchers say.
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- Transplants always carried the risk of
cancer because doctors must suppress the immune system with powerful drugs
such as cyclosporine to prevent the patient's body from attacking the new
organ.
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- But previously it was believed the cancer
risk increased because the weakened immune system failed to destroy defective
cells that could turn malignant.
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- "This study suggests the drug has
a direct effect on the tumor cell and enhances it growth,'' said Dr. Gary
Nabel, a University of Michigan researcher who specializes in the immune
system.
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- The study was conducted by Cornell University
researchers and published in Thursday's issue of the journal Nature.
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- Doctors were quick to caution that the
findings will not affect treatment of transplant patients because it applies
only to cancer that has already formed.
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- In fact, they emphasized the study provides
an important clue about blocking cancer growth.
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- "If anything, it's a reason for
hope,'' said Dr. Manikkam Suthanthiran, chief of transplant medicine at
Cornell.
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- Suthanthiran and his colleagues isolated
human lung and bladder cancer cells that were treated with cyclosporine.
They also injected cancerous cells into specially bred mice that had virtually
no immune system.
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- The findings indicated that cyclosporine
promotes the production of a natural protein called transforming growth
factor beta, already a suspect in cancer growth.
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- "Our findings in no way mean this
is increasing the incidence of cancer,'' Suthanthiran said. "It more
reflects that cancer can be made more aggressive by a certain protein.''
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- He added that the study reveals a potential
mechanism for blocking cancer by inhibiting the production of TGF beta.
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- Cyclosporine, which is also used to treat
arthritis, is made by the Swiss-based pharmaceutical giant Novartis. Geoff
Cook, a Novartis spokesman, said the company sees no cause for concern.
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- Dr. Israel Penn, a transplant pioneer
at the University of Cincinnati, said only a small proportion of transplant
patients have pre-existing cancer.
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- "For the tens of thousands of people
receiving cyclosporine for years with very beneficial results, the good
far, far outweighs the bad,'' he siads.
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