Single nucleotide polymorphisms in matrix metalloproteinase genes and lung cancer chemotherapy response and prognosis.

The prognosis for lung cancer patients treated with chemotherapy is poor. Single nucleotide polymorphisms (SNPs) in matrix metalloproteinase (MMP) genes could influence treatment outcome by altering apoptotic pathways. Eight SNPs with known or suspected phenotypic effect in six genes (MMP1, MMP2, MMP3, MMP7, MMP9 and MMP12) were investigated. For 349 Caucasian patients with primary lung cancer, receiving first-line chemotherapy, three different endpoints were analysed: response after the second cycle, progression free survival (PFS) and overall survival (OS). The prognostic value of the SNPs was analysed using multiple logistic regression for all patients and histology-, stage- and treatment-specific subgroups. Hazard ratio estimates for PFS and OS were calculated using Cox regression methods. None of the investigated polymorphisms modified response significantly in the whole patient population. However, tumour stage IIIB variant allele carriers of MMP2 C-735T showed a significantly worse response. PFS was significantly prolonged in MMP1 G-1607GG variant allele carriers and OS in small cell lung cancer patients carrying the MMP12 A-82G variant allele. In conclusion, this study identified SNPs in MMP1, MMP2, MMP7 and MMP12 for further investigation as possible predictors of chemotherapy outcome in lung cancer patients.

The chromosome-based challenge assay using fluorescence in situ hybridization: a possible test for increased cancer susceptibility.

UNLABELLED: The challenge assay is a cytogenetic approach to measure the repair competence of cells. For in vitro studies, human lymphocytes are exposed to different substances and are irradiated simultaneously. To investigate subjects exposed occupationally or environmentally, untreated blood samples are directly irradiated without any further treatment. Certain substances like heavy metals reveal carcinogenic potential without well defined mechanism of action. While they are not mutagenic they may have an effect on DNA repair capacity. The challenge assay was successfully applied in vitro experiments with cadmium to detect an interaction of this heavy metal with the repair of X-ray-induced chromosome breaks. CdCl(2) alone had no effect on the formation of chromosome aberrations (CA), not even in the cytotoxic concentration (50 microM). However, cadmium showed an effect on the number of chromosomal rearrangements (CR) after X-ray challenge. For 0.5 microM CdCl(2), CA frequencies were significantly elevated compared to the rates for X-rays alone. For the two higher concentrations the rates showed a slight additional increase. Hence, the challenge assay appears suitable to test for chromosomal sensitivity induced by toxicants. Subsequently, a study of styrene exposed workers was initiated to address the question whether styrene exposure has an influence on the DNA repair. In addition, we investigated whether a polymorphism of genes coding for phase II detoxifying enzymes glutathione-S-transferases GSTM1 and GSTT1 had an influence on chromosomal sensitivity. First and preliminary data are presented. While there is a correlation of the rate of CR with cumulative lifetime exposure of styrene, the most recent styrene exposure had no effect. 'At risk' genotypes with higher incidence of CA could not be identified at this stage of the ongoing study. CONCLUSION: the challenge assay is able to detect enhanced susceptibility for CR caused by genetic predisposition for DNA repair deficiency. Our data indicate that environmental or occupational exposure to certain substances can interfere with DNA repair processes. As the process of induction of CR is associated with carcinogenesis, the challenge assay may provide a valuable biomarker for cancer epidemiology studies.

Induction and repair inhibition of oxidative DNA damage by nickel(II) and cadmium(II) in mammalian cells.

Compounds of nickel(II) and cadmium(II) are carcinogenic to humans and to experimental animals. One frequently discussed mechanism involved in tumor formation is an increase in reactive oxygen species by both metals with the subsequent generation of oxidative DNA damage. In the present study we used human HeLa cells to investigate the potential of nickel(II) and cadmium(II) to induce DNA lesions typical for oxygen free radicals in intact cells and the effect on their repair. As indicators of oxidative DNA damage, we determined the frequencies of DNA strand breaks and of lesions recognized by the bacterial formamidopyrimidine-DNA glycosylase (Fpg protein), including 7,8-dihydro-8-oxoguanine (8-hydroxyguanine), a pre-mutagenic DNA base modification. Nickel(II) caused a slight increase in DNA strand breaks at 250 microM and higher, while the frequency of Fpg-sensitive sites was enhanced only at the cytotoxic concentration of 750 microM. The repair of oxidative DNA lesions induced by visible light was reduced at 50 microM and at 100 microM nickel(II) for Fpg-sensitive sites and DNA strand breaks, respectively; the removal of both types of lesions was blocked nearly completely at 250 microM nickel(II). In the case of cadmium(II), DNA strand breaks occurred at 10 microM and no Fpg-sensitive sites were detected. However, the repair of Fpg-sensitive DNA lesions induced by visible light was reduced at 0.5 microM cadmium(II) and higher, while the closure of DNA strand breaks was not affected. Since oxidative DNA damage is continuously induced during aerobic metabolism, an impaired repair of these lesions might well explain the carcinogenic action of nickel(II) and cadmium(II).

Sensitive analysis of oxidative DNA damage in mammalian cells: use of the bacterial Fpg protein in combination with alkaline unwinding.

The measurement of oxidative DNA base modifications by different methods has received special attention in recent years. Here we describe a procedure to quantify DNA lesions recognized by the bacterial formamido-pyrimidine-DNA glycosylases (Fpg protein). These include 7,8-dihydro-8-oxoguanine (8-hydroxyguanine) as well as some other forms of imidazole ring-opened purines, which are converted into abasic sites and subsequently into DNA single-strand breaks by the associated endonuclease activity. The frequency of DNA strand breaks is determined by the alkaline unwinding technique. The procedure provides a fast and sensitive tool to assess the extent of spontaneous as well as induced oxidative DNA damage in mammalian cells.

Interaction of carcinogenic metal compounds with deoxyribonucleic acid repair processes.

The potentials of nickel(II) and cadmium(II) to interfere with the repair of different types of deoxyribonucleic acid (DNA) lesions was investigated. Concerning the nucleotide excision repair pathway, nickel(II) has been shown to reduce the incision and the ligation frequency after ultraviolet (UV)-irradiation. When applying a gel mobility shift assay and HeLa nuclear cell free extracts, nickel(II) diminishes the specific binding of a protein to UV-damaged DNA, suggesting that nickel(II) interferes with the DNA-protein interactions involved in the damage recognition after UV-irradiation. Similarly, the incision frequency is reduced in the presence of low concentrations of cadmium(II). Concerning the repair of oxidative DNA damage induced by visible light, non-cytotoxic concentrations of nickel(II) caused a complete repair inhibition of DNA base modifications like 7,8-dihydro-8-oxoguanine (8-hydroxyguanine) and of DNA strand breaks. Since the repair of DNA damage is essential for the prevention of cancer, its inhibition may account for the carcinogenic action of the respective metal compounds.