The nucleotide sequence of the 4,377-bp chromosomal region of Pseudomonas fluorescens ST that codes for the oxidation of styrene to phenylacetic acid was determined. Four open reading frames, named styA, styB, styC, and styD, were identified in this region. Sequence analysis and biotransformation assays, performed with batch and continuous cultures, allowed us to identify the functions of the sequenced genes. styA and styB encode a styrene monooxygenase responsible for the transformation of styrene to epoxystyrene; styC codes for the second enzyme of the pathway, an epoxystyrene isomerase that converts epoxystyrene to phenylacetaldehyde; and the styD gene produces a phenylacetaldehyde dehydrogenase that oxidizes phenylacetaldehyde to phenylacetic acid. StyA, 415-amino-acids long, was found to be weakly homologous to p-hydroxybenzoate hydroxylase from both P. fluorescens and P. aeruginosa and to salicylate hydroxylase from P. putida, suggesting that it might be a flavin adenine dinucleotide-binding monooxygenase. StyB was found to be partially homologous to the carboxyterminal part of the 2,4-dichlorophenol-6-monooxygenase encoded by plasmid pJP4, while the styC product did not share significant homology with any known proteins. The fourth open reading frame, styD, could encode a protein of 502 amino acids and was strongly homologous to several eukaryotic and prokaryotic aldehyde dehydrogenases. The order of the genes corresponds to that of the catabolic steps. The previously suggested presence of the gene for epoxystyrene reductase, which directly converts epoxystyrene to 2-phenylethanol (A. M. Appl. Environ. Microbiol. 61:121-127, 1996), has not been confirmed by sequencing and by biotransformation assays performed in continuous cultures. A copy of the insertion sequence IS1162, belonging to the IS21-like family of elements, was identified immediately downstream of the styrene catabolic genes.

It is well known that the occupational exposure to contaminants and carcinogens leads to the development of cancer in exposed workers. In the 18th century, Percivall Pott was the first to hypothesize that chronic exposure to dust in the London chimney sweeps was associated with an increased risk of developing cancer. Subsequently a growing body of evidence indicated that other physical factors were also responsible for oncogenic mutations. Over the past decades, many carcinogens have been found in the occupational environment and their presence is often associated with an increased incidence of cancer. Occupational exposure involves several factors and the association between carcinogens, occupational exposure and cancer is still unclear. Only a fraction of factors is recognized as occupational carcinogens and for each factor, there is an increased risk of cancer development associated with a specific work activity. According to the International Agency for Research on Cancer (IARC), the majority of carcinogens are classified as ‘probable’ and ‘possible’ human carcinogens, while, direct evidence of carcinogenicity is provided in epidemiological and experimental studies. In the present review, exposures to benzene, pesticides and mineral fibers are discussed as the most important cancer risk factors during work activities.

A gene bank from Pseudomonas fluorescens ST was constructed in the broad-host-range cosmid pLAFR3 and mobilized into Pseudomonas putida PaW340. Identification of recombinant cosmids containing the styrene catabolism genes was performed by screening transconjugants for growth on styrene and epoxystyrene. Transposon mutagenesis and subcloning of one of the selected genome fragments have led to the identification of three enzymatic activities: a monooxygenase activity encoded by a 3-kb PstI-EcoRI fragment and an epoxystyrene isomerase activity and an epoxystyrene reductase activity encoded by a 2.3-kb BamHI fragment. Escherichia coli clones containing the 3-kb PstI-EcoRI fragment were able to transform styrene into epoxystyrene, and those containing the 2.3-kb BamHI fragment converted epoxystyrene into phenylacetaldehyde or, only in the presence of glucose, into 2-phenylethanol. The three genes appear to be clustered and are probably encoded by the same DNA strand. In E. coli, expression of the epoxystyrene reductase gene was under the control of its own promoter, whereas the expression of the other two genes was dependent on the presence of an external vector promoter.

Liver cancer is the second leading worldwide cause of cancer-associated mortalities. Hepatocellular carcinoma, which accounts for the majority of liver tumors, ranks fifth among types of human cancer. Well-established risk factors for liver cancer include the hepatitis B and C viruses, aflatoxins, alcohol consumption, and oral contraceptives. Tobacco smoking, androgenic steroids, and diabetes mellitus are suspected risk factors. Current knowledge regarding non-infective occupational risk factors for liver cancer is inconclusive. The relevance of liver disorders to occupational medicine lies in the fact that the majority of chemicals are metabolized in the liver, and toxic metabolites generated via metabolism are the predominant cause of liver damage. However, their non-specific clinical manifestations that are similar in a number of liver diseases make diagnosis difficult. Furthermore, concomitant conditions, such as viral hepatitis and alcohol or drug abuse, may mask liver disorders that result from occupational hepatotoxic agents and block the demonstration of an occupational cause. The identification of environmental agents that result in human cancer is a long and often difficult process. The purpose of the present review is to summarize current knowledge regarding the association of non-infective occupational risk exposure and HCC, to encourage further research and draw attention to this global occupational public health problem.

Malignant mesothelioma (MM) is an aggressive tumor associated with environmental or occupational exposure to asbestos fibers. Erionite is a fibrous zeolite, morphologically similar to asbestos and it is assumed to be even more carcinogenic. Onset and progression of MM has been suggested as the result of the cooperation between asbestos and other cofactors, such as SV40 virus infection. Nevertheless, several cases of MM were associated with environmental exposure to erionite in Turkey, where SV40 was never isolated in MM specimens. We show here that erionite is poorly cytotoxic, induces proliferating signals and high growth rate in human mesothelial cells (HMC). Long term exposure to erionite, but not to asbestos fibers, transforms HMC in vitro, regardless of the presence of SV40 sequences, leading to foci formation in cultured monolayers. Cells derived from foci display constitutive activation of Akt, NF-jB and Erk1/2, show prolonged survival and a deregulated cell cycle, involving cyclin D1 and E overexpression. Our results reveal that erionite is able per se to turn HMC into transformed highly proliferating cells and disclose the carcinogenic properties of erionite, prompting for a careful evaluation of environmental exposure to these fibers. The genetic predisposition to the effect of erionite is a separate subject for investigation. ' 2007 Wiley-Liss, Inc.