The authors, Jui-I.Chao and Pao-Chen Kuo, found critical problems with some of the data they reported in the above paper and wish to withdraw it from publication. The paper has been published online in Carcinogenesis Advance Access and the authors hereby retract this paper and discourage citations of it.
For reference, the abstract of the paper is printed below:
Abstract
In this report, we investigated the role of nitric oxide (NO) in regulating cell cycle arrest and apoptosis in the human lung carcinoma cells. Cadmium (Cd) is a well-known environmental toxicant and human carcinogen. CdCl2 (80 µM, 2 h) increased the inducible nitric oxide synthase (iNOS) proteins and enhanced the NO production in CL3 human lung adenocarcinoma cells. The cytotoxicity, caspase-3 activation, and apoptosis induced by Cd were reduced when iNOS activity was inhibited by NG-nitro-L-arginine methyl ester (L-NAME) or when NO was scavenged by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (cPTIO). Exposure to exogenous NO, derived from 400 µM S-nitroso-N-acetyl-penicillamine (SNAP), for 24 h also induced the cytotoxicity, caspase-3 activation and apoptosis in CL3 cells, which were inhibited by cPTIO but not by L-NAME. Thus Cd and SNAP induced apoptosis via iNOS-dependent and iNOS-independent pathway, respectively. In addition, SNAP inhibited cell growth and induced G2/M arrest in CL3 cells. Total p53 and phospho-p53 (Ser-15) proteins were increased by SNAP in a concentration-dependent manner. H1299-tsp53 cells that expressed functional p53Leu173 (at 32°C) were much more effective in the induction of p21 and more resistant to cytotoxicity than those expressed mutant p53Leu173 (at 37°C) when treated with SNAP. In contrast, cells with mutant p53Leu173 increased Cd- and SNAP-induced activation of caspase-3 and p38 mitogen-activated protein (MAP) kinase. Moreover, Cd- and SNAP-induced caspase-3 activation and cell death were reduced when CL3 cells expressed a dominant negative p38 protein. These findings suggest that p53 elevates the p21 level, which mediates NO-induced G2/M arrest and reduces cell death. In contrast, p38 MAP kinase plays a major role in the NO-induced apoptosis via the caspase-3 activation in a p53 independent pathway.