title: Non-genomic inhibitory signaling of beta-carotene in squamous cell carcinoma of the lungs.
abstract: Studies have suggested that retinoids prevent lung cancer by interacting with nuclear retinoid receptors. However, clinical trials with beta-carotene increased lung cancer mortality. We recently showed that beta-carotene stimulates the proliferation of small airway-derived adenocarcinoma by increasing cAMP signaling. Here, we have tested the hypothesis that beta-carotene may stimulate squamous cell carcinoma cells via similar mechanisms. We determined the effects of beta-carotene in cell lines from squamous cell carcinomas and large airway epithelia on proliferation by MTT assays in the presence and absence of inhibitors. Signaling via cAMP/PKA was measured by immunoassays and PKA activation assay. Phosphorylated ERK1/2 was determined by Western blotting. beta-carotene significantly inhibited proliferation and phosphorylation of ERK1/2 by Galphas-mediated signaling involving adenylyl cyclase, cAMP, PKA and ERK1/2. These findings introduce a non-genomic inhibitory mechanism of beta-carotene and emphasize the need for the development of marker-guided lung cancer prevention.
authors.affiliation: Experimental Oncology Laboratory, Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA.
authors.forename: Hussein A N
authors.initials: HA
authors.lastname: Al-Wadei
authors.forename: Hildegard M
authors.initials: HM
authors.lastname: Schuller
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007118:Immunoassay; D008175:Lung Neoplasms / Q000378:metabolism*; D008954:Models, Biological; D010766:Phosphorylation; D015398:Signal Transduction; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D019207:beta Carotene / Q000494:pharmacology*
chemical_list: D013778:Tetrazolium Salts; D013844:Thiazoles; D019207:beta Carotene; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C022616:thiazolyl blue