Smoking-induced Up-regulation of AKR1B10 Expression in the Airway Epithelium of Healthy Individuals

The aldokatoreductases (AKRs) represent a gene superfamily that code for monomeric, soluble NAD(P)H-dependent oxidoreductases that mediate elimination reactions. AKR1B10, an AKR that functions to eliminate retinals, has been observed to be upregulated in squamous metaplasma and non small cell lung cancer, and has been suggested as a diagnostic marker specific to tobacco-related carcinogenesis. In the context of the link of smoking and lung cancer and the enhanced expression of AKR1B10 expression in lung cancer, we hypothesize that enhanced expression of AKR1B10 may be initiated in healthy smokers, prior to the development of any evidence of lung cancer. For this purpose, expression of AKR1B10 was assessed at the mRNA level using microarrays in the large airway epithelium (21 healthy nonsmokers, 31 health smokers) and small airway epithelium (51 healthy nonsmokers, 58 healthy smokers) obtained by fiberoptic bronchoscopy and brushing, as well as assessment in a subset of this population by TaqMan PCR and in endobronchial biopsies by Western analysis and immunohistochemistry. Compared to healthy nonsmokers, ARK1B10 mRNA levels were markedly upregulated in both the large and small airway epithelium of healthy smokers (large airway microarray p<0.0001, small airway p<0.0001; TaqMan large airway, p<0.02, small airway p<0.01). Consistent with the mRNA data, AKR1B10 protein was significantly upregulated in the airway epithelium of healthy smokers as assessed by Western analysis and by immunohistochemistry, with AKR1B10 expressed in both differentiated and basal cells of the normal epithelium. Finally, cigarette smoke extract mediated up-regulation of AKR1B10 in airway epithelial cells in vitro. Thus, smoking per se mediates up-regulation of AKR1B10 expression in the airway epithelium of healthy smokers with no evidence of lung cancer. In the context of these observations, and the link of AKR1B10 to the metabolism of retinals and to lung cancer, the smoking-induced up-regulation of AKR1B10 may be an early process in the multiple events leading to the develop of lung cancer.

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Wang R, Wang G, Ricard MJ, Ferris B, Strulovici-Barel Y, Salit J, Hackett NR, Gudas LJ, Crystal RG