Growth Hormone Implicated in Deadly Lung Cancer

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Dec. 21, 1999 (New York) -- The release of a growth hormone may be an initial step in triggering the cascade of events that lead to lung cancer, researchers report in the Dec. 21 issue of the Proceedings of the National Academy of Sciences. The new study suggests that antagonistic drugs designed to block the release of the hormone may be a promising therapy for shrinking the deadly tumors.

"This paper shows that ... [drugs] of this class can probably be used in the future for cancer treatment," co-author Hippokratis Klaris, PhD, tells WebMD. But Klaris, an instructor at Tulane University School of Medicine in New Orleans, stresses that it would be premature to draw too many conclusions from this study, which involved mice deliberately given a human type of lung cancer known as small-cell lung cancer, or SCLC.

For the last five years, Klaris and colleagues, including lead author Andrew V. Schally, PhD, have been working on developing drugs that block growth hormone-releasing hormone, also known as GHRH. In previous work, such drugs have been shown to block the growth of bone cancers, brain cancers, small-cell and non-small-cell lung cancers, as well as cancers of the prostate, kidney, pancreas, and breast. Growth hormone is released from the pituitary gland, but how it plays a role in causing tumors is unknown. However, one important observation from this study is that GHRH is present elsewhere in the body, not just in the pituitary.

Compared with disease-free mice, mice bearing the human lung cancers had higher levels of growth hormone-releasing hormone. When a drug that inhibits growth hormone-releasing hormone was given to the mice for 31 days, it blocked tumor growth and reduced tumor volume by 80% and tumor weight by 73%. Even though researchers do not yet understand what effect GHRH has on tumor production, there is a possibility that they may be able to spot individuals at high risk of lung cancer based on the level of GHRH in his or her blood. Klaris says the research team is now focusing on more of the same type of research in different tumors that are associated with the production of this hormone.

New therapies for treating lung cancer are important since the disease usually is associated with a very poor prognosis and few effective strategies exist. Lung cancer is the leading cause of cancer-related deaths in the Western world, and small-cell lung cancer accounts for about 20% of all cases of cancers of the lung.

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