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Analysis of aberrant methylation on promoter sequences of tumor suppressor genes and total DNA in sputum samples: a promising tool for early detection of COPD and lung cancer in smokers

Leda Guzmán1*, María Soledad Depix2, Ana María Salinas2, Rosa Roldán3, Francisco Aguayo4, Alejandra Silva2 and Raul Vinet56

Author Affiliations

1 Departamento de Bioquímica, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile

2 Facultad de Salud, Escuela de Tecnología Médica, Universidad Santo Tomás, Santiago, Chile

3 Unidad de Enfermedades respiratorias, Hospital San José, Santiago, Chile

4 Programa de Virología, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile

5 Facultad de Farmacia, Universidad de Valparaíso, Valparaíso, Chile

6 Centro Regional de Estudios en Alimentos Saludables (CREAS), Valparaíso, Chile

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Diagnostic Pathology 2012, 7:87  doi:10.1186/1746-1596-7-87

Published: 20 July 2012

Abstract

Background

Chronic obstructive pulmonary disease (COPD) is a disorder associated to cigarette smoke and lung cancer (LC). Since epigenetic changes in oncogenes and tumor suppressor genes (TSGs) are clearly important in the development of LC. In this study, we hypothesize that tobacco smokers are susceptible for methylation in the promoter region of TSGs in airway epithelial cells when compared with non-smoker subjects. The purpose of this study was to investigate the usefulness of detection of genes promoter methylation in sputum specimens, as a complementary tool to identify LC biomarkers among smokers with early COPD.

Methods

We determined the amount of DNA in induced sputum from patients with COPD (n = 23), LC (n = 26), as well as in healthy subjects (CTR) (n = 33), using a commercial kit for DNA purification, followed by absorbance measurement at 260 nm. The frequency of CDKN2A, CDH1 and MGMT promoter methylation in the same groups was determined by methylation-specific polymerase chain reaction (MSP). The Fisher’s exact test was employed to compare frequency of results between different groups.

Results

DNA concentration was 7.4 and 5.8 times higher in LC and COPD compared to the (CTR) (p < 0.0001), respectively. Methylation status of CDKN2A and MGMT was significantly higher in COPD and LC patients compared with CTR group (p < 0.0001). Frequency of CDH1 methylation only showed a statistically significant difference between LC patients and CTR group (p < 0.05).

Conclusions

We provide evidence that aberrant methylation of TSGs in samples of induced sputum is a useful tool for early diagnostic of lung diseases (LC and COPD) in smoker subjects.

Virtual slides

The abstract MUST finish with the following text: Virtual Slides The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1127865005664160

Keywords:
DNA methylation; Sputum; Lung cancer; COPD