Inhibition of lung carcinogenesis by 1α,25‐dihydroxyvitamin D₃ and 9‐cis retinoic acid in the A/J mouse model: Evidence of retinoid mitigation of vitamin D toxicity

Abstract

9-cis-Retinoic acid (9cRA) and 1a, 25-dihydroxyvitamin D 3 (1,25D) show promise as potential chemopreventive agents. We examined 9cRA and 1,25D, alone and in combination, for their potential to inhibit carcinogen (NNK)-induced lung carcinogenesis in A/J mice. A/J mice (n 5 14/group) were treated with 9cRA (7.5, 15, or 30 mg/kg diet), 1,25D (2.5 or 5.0 lg/kg diet), or a combination of 9cRA (15 mg/kg diet) plus 1,25D (2.5 lg/kg diet) for 3 weeks before and 17 weeks after carcinogen injection. Lung tumor incidence, tumor multiplicity, plasma 1,25D levels and kidney expression of vitamin D 24-hydroxylase (CYP24) were determined. Compared to carcinogen-injected controls, mice receiving 9cRA supplementation had significantly lower tumor multiplicity at all doses (decreased 68-85%), with body weight loss at the higher doses of 9cRA. Mice receiving 1,25D supplementation had significantly lower tumor incidence (decreased 36 and 82%) and tumor multiplicity (decreased 85 and 98%), but experienced significant body weight loss, kidney calcium deposition, elevated kidney CYP24 expression and decreased fasting plasma 1,25D levels. Although, there was no apparent influence on chemopreventive efficacy, addition of 9cRA to 1,25D treatment effectively prevented the weight loss and kidney calcification associated with 1,25D treatment alone. These data demonstrate that 9cRA and 1,25D, alone or combined, can inhibit lung tumor promotion in the A/J mouse model. Combining 1,25D with 9cRA has the potential to mitigate the toxicity of 1,25D, while preserving the significant effect of 1,25D treatment against lung carcinogenesis. The underlying mechanism behind this effect does not appear to be related to retinoid modulation of vitamin D catabolism. ' 2006 Wiley-Liss, Inc.Key words: lung cancer; 9-cis retinoic acid; 1a,25-dihydroxyvitamin D 3Chemoprevention by diet or drug intervention may offer a realistic and practical means of modifying the risk of lung cancer, the leading cause of cancer deaths in both men and women in the United States. 1 Two classes of chemopreventive compounds that have been considered are the retinoids and the active form of vitamin D, 1a,25-dihydroxyvitamin D 3 (1,25D, also calcitriol).Retinoids are required for proper differentiation of lung and upper airway epithelium, 2 and both 9-cis retinoic acid (9cRA, also 9-cis tretinoin) and all-trans retinoic acid have been shown to inhibit cell growth and proliferation in lung cancer cell lines. 3 Studies in animal models of lung cancer suggest that retinoids may be effective in cancer chemoprevention in vivo, but results have varied with species, dose and timing of treatment in relation to induction of carcinogenesis. [4][5][6] In human lung cancer, epidemiological evidence supports a role for vitamin A-rich foods and supplements in protection against the development of lung cancer in smokers and nonsmokers alike 7 ; however, clinical trials assessing the efficacy of retinoid supplementation against lung cancer have yielded inconsistent and inconclusive results. [8][...

Association between Serum 25-Hydroxyvitamin D Levels and TTN

“…Sundar et al [25] have suggested that the lack of vitamin D receptor activates pathways that are associated with pathogenesis of chronic obstructive pulmonary disease. A study in a mouse model of lung cancer found that vitamin D supplementation decreased tumor incidence [26]. …”

Low Plasma 25-Hydroxyvitamin D and Risk of Tobacco-Related Cancer

“…Tobacco smoke chemicals may influence vitamin D metabolism and function (8 -10 ), and conversely vitamin D may modify the carcinogenicity of tobacco smoke chemicals (3,(11)(12)(13)(14). Such studies led the International Agency for Research on Cancer to suggest that the effect of tobacco smoke on vitamin D may explain a component of the carcinogenicity conferred by smoking (15 ); however, evidence from later nested case control and prospective cohort studies regarding individual tobacco-related cancers has been conflicting (16 -23 ).…”

Vitamin D and Lung Cancer Risk: A Comprehensive Review and Meta-Analysis

“…Vitamin D insufficiency is a global health problem and is associated with a number of illnesses [4,5]. Vitamin D also has been suggested to have important roles against cancer development, and it has anti-tumor effects [6,7]. Previous epidemiological studies have suggested that vitamin D is associated with decreased risks of colorectal cancer, and breast cancer [4,8].…”