Treatment of former smokers with 9-cis-retinoic acid reverses loss of retinoic acid receptor-beta expression in the bronchial epithelium: results from a randomized placebo-controlled trial.
BACKGROUND: Loss of retinoic acid receptor beta (RAR-beta) expression in the bronchial epithelium is considered a biomarker of preneoplasia. Retinoids can restore expression of this receptor and, presumably, halt the progression of carcinogenesis. This study was designed to investigate whether either of two retinoid-based regimens, 9-cis-retinoic acid (RA) or 13-cis-RA plus alpha-tocopherol (AT), could reverse RAR-beta expression loss in former smokers after 3 months of treatment. METHODS: Individuals (n = 226) who had smoked at least 20 pack-years and had ceased smoking for at least 12 months were randomly assigned to receive 3 months of daily oral 9-cis-RA (100 mg), 13-cis-RA (1 mg/kg) + AT (1200 IU), or placebo. Bronchoscopy and biopsy at six predetermined sites of the bronchial tree were performed before treatment and at 3 and 6 months thereafter. Specimens were evaluated for squamous metaplasia, dysplasia, and RAR-beta expression. McNemar's test was used to test changes in RAR-beta expression and squamous metaplasia within each treatment group, and a generalized estimating equations model was applied to model the treatment effect, adjusting for covariates. All statistical tests were two-sided. RESULTS: A total of 177 assessable subjects completed at least 3 months of therapy and underwent at least the baseline and 3-month bronchoscopic evaluations with biopsies. RAR-beta was detected in 69.7% of all baseline biopsy samples, and metaplasia was evident in 6.9% of all baseline samples from 240 subjects. Restoration of RAR-beta expression (P =.03) and reduction of metaplasia (P =.01) were found in the 9-cis-RA group. After adjustment for years of smoking, packs/day smoked, and metaplasia, treatment with 9-cis-RA, but not with 13-cis-RA + AT, led to a statistically significant increase in RAR-beta expression compared with placebo (P =.03). CONCLUSION: 9-cis-RA treatment can restore RAR-beta expression in the bronchial epithelium of former smokers, raising the possibility that this retinoid has potential chemopreventive properties in former smokers.[1]References
- Treatment of former smokers with 9-cis-retinoic acid reverses loss of retinoic acid receptor-beta expression in the bronchial epithelium: results from a randomized placebo-controlled trial. Kurie, J.M., Lotan, R., Lee, J.J., Lee, J.S., Morice, R.C., Liu, D.D., Xu, X.C., Khuri, F.R., Ro, J.Y., Hittelman, W.N., Walsh, G.L., Roth, J.A., Minna, J.D., Hong, W.K. J. Natl. Cancer Inst. (2003) [Pubmed]
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