Analysis of GSTM1 and GSTT1 polymorphisms in circulating plasma DNA of lung cancer patients.

The concentration of free circulating plasma DNA and the genetic profile of patients suffering from various types of tumors were studied in an effort to increase the understanding of the biomarkers and genetic factors involved in predisposing an individual to lung cancer (LC). The polymorphic inheritance of glutathione S-transferases (GST), which modulate the effects of various genotoxic agents, especially those derived from benzo[a]pyrene, one of the main tobacco carcinogens, has been implicated in both cancer risk and prognostics. We investigated gene polymorphisms in the blood serum of patients previously diagnosed at the Pneumology Division of the Clementino Fraga Filho University Hospital of the Federal University of Rio de Janeiro and in buccal swab samples of exfoliated oral cells obtained from a population of healthy controls. The distribution of GSTM1 and GSTT1 polymorphisms was not significantly different between LC patients and the controls, suggesting that GSTM1 and GSTT1 alone or in combination are not independent risk factors for LC. However, a close relationship between smoking status and LC was clearly demonstrated. The most significant risk for LC concerning tobacco smoking was found in the association of null genotypes for GSTM1 and GSTT1 (P < 0.0001).

Identification of new RECQL4 mutations in Caucasian Rothmund-Thomson patients and analysis of sensitivity to a wide range of genotoxic agents.

Rothmund-Thomson syndrome (RTS), a rare recessive autosomal disorder, presents genome instability and clinical heterogeneity with growth deficiency, skin and bone defects, premature aging symptoms and cancer susceptibility. A subset of RTS patients presents mutations of the RECQL4 gene, member of the RecQ family of DNA helicases, including the RECQL2 (BLM) and RECQL3 (WRN) genes, defective in the cancer prone Bloom and Werner syndromes, respectively. Analysis of the RECQL4 gene in six clinically diagnosed RTS patients shows five patients, including two siblings, with eight mutations mainly located in the helicase domain, three patients presenting two mutations. The alterations include four missense mutations, one nonsense mutation and the same frameshift deletion, g.2881delG in exon 9 found in three patients. Seven RECQL4 polymorphisms, two being new, have also been identified. Primary RTS fibroblasts from these RTS patients show no sensitivity to a wide variety of genotoxic agents including ionizing or ultraviolet irradiation, nitrogen mustard, 4NQO, 8-MOP, Cis-Pt, MMC, H2O2, HU, or UV plus caffeine which could be related to the RECQL4 alterations identified here. This is in contrast with the DNA damage sensitive Bloom and Werner cells and highlights the complexity of the numerous RecQ protein functions implicated in the different cellular pathways required for maintaining genomic integrity.

Changes in protein expression due to deleterious mutations in the FA/BRCA pathway.

Inherited deleterious mutations in one of the Fanconi anemia genes lead to a disease, characterized by bone marrow failure, myeloid leukemia, and hypersensitivity to DNA damage. We identified proteins likely associated to the molecular signaling pathways involved in DNA repair of interstrand cross-link lesions and in mechanisms of genomic stability mediated by FA/BRCA pathways. We compared protein maps resolved by bidimensional electrophoresis and analyzed differentially expressed proteins, by mass spectrometry, between FA complementation group C (FANCC)-deficient cells, and their ectopically corrected counterpart in physiological conditions or after treatment with MMC. We found six differentially expressed proteins; among them, the checkpoint mediator protein MDC1 whose expression was disrupted in FANCC-/- cells. The potential role of differentially expressed proteins in FA phenotype is discussed.