NAD(P)H:quinone oxidoreductase (DT-diaphorase) activity and mRNA content in normal and neoplastic mouse lung epithelia

Primary lung tumors in mice as an aid for understanding, preventing, and treating human adenocarcinoma of the lung

Primary lung tumors in mice have morphologic, histogenic, and molecular features similar to human lung adenocarcinoma, and in particular, the bronchiolo-alveolar carcinoma subtype. Because of this, and because of the genetic homology between man and mouse and the ease of genetic manipulations in mice, this model system is receiving intense research attention. This review is intended to be informative to clinical investigators, and describes features of this model, how it is being used for translational research, and points out additional avenues of study that could have practical benefits, such as application for identifying novel therapeutic strategies.

Molecular comparison of human and mouse pulmonary adenocarcinomas

Mice develop lung tumors similar in their histogenesis and molecular features to peripheral adenocarcinomas in humans. The advantage of this model system is that events early in tumorigenesis can be delineated and their biological consequences tested by transgenic and knockout strategies. Both human and murine adenocarcinomas contain Kras mutations; in mice these occur within weeks following carcinogen administration. Decreased expression of similar tumor suppressor genes occur in both species due to mutation, deletion, altered DNA methylation, or unknown mechanisms. These genes include p15, p16, Rb, cyclin D1, p53, Apc, Mcc, and Gjal. Some genes have only been examined in one of these species, such as the deletions in chromosome 3p and the overexpression of bcl 2 in human adenocarcinoma. Not all molecular changes are identical to the two species, however. Quinone oxidoreductase (DT-diaphorase) levels rise in the human tumors but fall in the mouse; the extent of both changes is very dramatic. Similarly, EGF-receptor content often increases in human lung adenocarcinomas but decreases in the mouse tumors. In general, however, the nature of the molecular changes is quite similar.

Mouse lung epithelial cell lines--tools for the study of differentiation and the neoplastic phenotype

Several dozen lung epithelial cell lines have been established in culture over the past 20 years from normal lung explants and their spontaneous transformants, and from lung tumors that arose spontaneously or were induced with chemicals, viruses, or oncogenic transgenes. To provide information from which to choose appropriate lines for investigating problems in lung cell biology and pulmonary neoplasia, this review describes the origins of these lines and some of their characteristics. These include growth, morphology, tumorigenicity, ability to metastasize, xenobiotic metabolism, mutational status, signal transducing activities, cytogenetics, ability to form domes, and electric conductance. In addition to collecting this information in a single place for the first time, we describe previously unpublished apoptosis features of some of these lines. An increasing number of investigations are beginning to use these lines and this review contains references into 1997.

Mouse liver NAD(P)H:quinone acceptor oxidoreductase: protein sequence analysis by tandem mass spectrometry, cDNA cloning, expression in Escherichia coli, and enzyme activity analysis

The amino acid sequence of mouse liver NAD(P)H:quinone acceptor oxidoreductase (EC 1.6.99.2) has been determined by tandem mass spectrometry and deduced from the nucleotide sequence of the cDNA encoding for the enzyme. The electrospray mass spectral analyses revealed, as previously reported (Prochaska HJ, Talalay P, 1986, J Biol Chem 261:1372-1378), that the 2 forms--the hydrophilic and hydrophobic forms--of the mouse liver quinone reductase have the same molecular weight. No amino acid sequence differences were found by tandem mass spectral analyses of tryptic peptides of the 2 forms. Moreover, the amino-termini of the mouse enzymes are acetylated as determined by tandem mass spectrometry. Further, only 1 cDNA species encoding for the quinone reductase was found. These results suggest that the 2 forms of the mouse quinone reductase have the same primary sequences, and that any difference between the 2 forms may be attributed to a labile posttranslational modification. Analysis of the mouse quinone reductase cDNA revealed that the enzyme is 273 amino acids long and has a sequence homologous to those of rat and human quinone reductases. In this study, the mouse quinone reductase cDNA was also ligated into a prokaryotic expression plasmid pKK233.2, and the constructed plasmid was used to transform Escherichia coli strain JM109. The E. coli-expressed mouse quinone reductase was purified and characterized. Although mouse quinone reductase has an amino acid sequence similar to those of the rat and human enzymes, the mouse enzyme has a higher NAD(P)H-menadione reductase activity and is less sensitive to flavones and dicoumarol, 2 known inhibitors of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of CB 1954 cytotoxicity by reduced pyridine nucleotides in human tumour cells by stimulation of DT diaphorase activity

The toxicity of CB 1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide] towards human cells was greatly enhanced by NADH (when foetal calf serum was present in the culture medium) and by nicotinamide riboside (reduced) (NRH), but not by nicotinate riboside (reduced). Co-treatment of human cells with CB 1954 and NADH resulted in the formation of crosslinks in their DNA. The toxicity produced by other DNA crosslinking agents was unaffected by reduced nicotinamide compounds. When caffeine was included in the medium, a reduction in the cytotoxicity of CB 1954 occurred. The toxicity experienced by human cell lines after exposure to CB 1954 and NADH was proportional to their levels of the enzyme DT diaphorase NAD(P)H dehydrogenase (quinone), EC 1.6.99.2. It is concluded that NRH, which we have shown to be a co-factor for rat DT diaphorase (Friedlos et al., Biochem Pharmacol 44: 25-31, 1992), is generated from NADH by enzymes in foetal calf serum, and stimulates the activity of human DT diaphorase towards CB 1954.

Identification of novel reduced pyridinium derivatives as synthetic co-factors for the enzyme DT diaphorase (NAD(P)H dehydrogenase (quinone), EC 1.6.99.2)

The enzyme DT diaphorase (NAD(P)H dehydrogenase (quinone), EC 1.6.99.2) is unusual in that it can utilize either NADH or NADPH as a co-factor for the reduction of its substrates. We have shown that the intact NAD(P)H molecule is not required and that other reduced pyridinium compounds can also act as co-factors for DT diaphorase. The entire adenine dinucleotide portion of NAD(P)H can be dispensed with entirely and the simplest quaternary (and therefore reducible) derivative of nicotinamide, 1-methylnicotinamide, was as effective as NAD(P)H as a co-factor for the reduction of the quinone, menadione. Nicotinamide 5'-O-benzoyl riboside was also as effective a co-factor as NAD(P)H, whilst nicotinamide ribotide and riboside have a higher Km, and decreased the kcat of DT diaphorase. Nicotinic acid derivatives had little activity. Kinetic analysis indicated that both nicotinamide ribotide and riboside may be interacting with the menadione binding site rather than the NAD(P)H site. Irrespective of the differences between the various reduced pyridinium derivatives in their ability to act as co-factors for the reduction of menadione by DT diaphorase, all the compounds that showed activity in this assay were equally effective co-factors for the reduction of the nitrobenzamide, CB 1954 (5-(aziridin-1-yl)-2,4-dinitrobenzamide). The apparent Km of DT diaphorase for all these co-factors approached zero. It was concluded that co-factor binding is not a rate-limiting step in the nitroreductase activity of DT diaphorase.

Differential expression of cytochrome P-450 in proliferating and quiescent cultures of murine lung epithelial cells

Expression of the cytochrome P-450 monooxygenase activity 7-ethoxyresorufin O-deethylase (7-ERD) was surveyed in proliferating and quiescent cultures of murine cell line C-10, a non-tumorigenic line of presumed alveolar type II origin. 7-ERD activities were undetectable in subconfluent/proliferating cultures but became detectable once the cultures had become confluent and their growth had arrested due to contact inhibition. Serum deprivation of subconfluent cultures resulted in a rapid inhibition of cell proliferation and the subsequent expression of 7-ERD. These results suggest that 7-ERD expression is regulated as a function of the proliferative status of C-10 cells.