such as "Introduction", "Conclusion"..etc
October 2007 -- Treatment with a derivative of vitamin A called retinoic acid was
associated with reduced lung cell growth in a group of former heavy
smokers, according to a study published online October 30 in the Journal of the National Cancer Institute.
smokers remain at elevated risk for lung cancer. According to one
hypothesis, lung cells that were damaged during years of smoking may
continue to grow and evolve into cancer even after that person has quit
smoking. Previous studies have suggested that retinoids, a class of
drugs related to vitamin A, may be effective for preventing lung cancer
in former smokers. Retinoids have also been shown to slow the growth of
cancer cells in laboratory experiments.
Investigators at the
University of Texas M.D. Anderson Cancer Center in Houston previously
conducted a double-blind lung cancer prevention trial among 225 former
heavy smokers. The subjects were randomly assigned to receive a 3-month
treatment of 13-cis-retinoic acid and vitamin E, or 9-cis-retinoic
acid, or a placebo. Walter Hittelman, Ph.D., and colleagues later
examined biopsy samples of participants’ lung tissue taken before and
after treatment, then measured the proliferation of the cells using a
biomarker called Ki-67.
Both treatments reduced cell
proliferation in one layer of the lung cells (the parabasal layer), but
not the other (the basal layer), which surprised the researchers.
In patients given 13-cis-retinoic acid and vitamin E,
there was a statistically significant reduction in parabasal layer cell
growth compared with the placebo treatment, but not in those given 9-cis-retinoic acid. When the data were analyzed by the biopsy site, both treatments statistically significantly reduced cell growth.
will therefore be important to distinguish the effects of molecularly
targeted agents on the basal and parabasal [lung cell] layers in
proposed lung chemoprevention trials with long follow-up,” the authors
In an accompanying editorial, Eva Szabo, M.D., of the
National Cancer Institute in Bethesda, Md., discusses the
appropriateness of using the biomarker Ki-67 as an alternative endpoint
in cancer prevention trials. While the biomarker showed that the
retinoid agents were able to reduce cell growth, she says it is still
too soon to test them in more advanced clinical trials. “We do not have
a full understanding of the effects of these agents on [lung cells] or
their effects during the full spectrum of carcinogenesis,” she writes.
Source : Journal of the National Cancer Institute
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