E-23. A DNA methylation profile of lung cancer

Abstract

Since the early 8Os, the irruption of the genetic alterations in lung cancer has received a lot of attention from the scientific community and the funding agencies. However, recently, a new type of alterations that have been denominated epigenetic lesions (because they do not involve changes in the strict nucleotide sequences) has attracted a huge interest. The main epigenetic modification in humans is DNA methylation. Nowadays, aberrations in the DNA methylation patterns are recognized as common hallmarks of all human cancers. An enormous effort to study the DNA methylation profile of human tumors is starting to be developed and it is shown in the exponential number of references and citations that this subject has generated in the scientific literature. Because DNA methylation is a dynamic defect, it is a perfect model to study the effects of environmental carcinogens and new anticancer pharmacological agents. Thus, it is very important to know the DNA methylation profile of lung cancer in all its forms: primary colon cancers, human colon cancer cell lines and mouse models. The aim of our laboratory is to accomplish this long coveted goal. We have created a multidisciplinary approach that studies DNA methylation in lung cancer from the most intimate molecular mechanisms to the most applicable-translational studies in molecular oncology. First, we have defined a detailed map of all the hypermethylation lesions presents in the vast majority of human primary tumors and cancer cell lines. These goal have been accomplished using two approaches: candidate gene approach (selecting the “suspicious genes” to be involved in cancer) and by massive genomic screenings of cDNA and DNA microarrays customized for DNA methylation studies. The hypermethylated genes found in these ways have been carefully dissected combining multiple techniques including bisulfite genomic sequencing, methylation-sensitive restriction analysis, methylation-specific-PCR and similarly driven techniques. Second, we have defined which are the total methylcitosine content in human neoplasia, counting each methylated cytosine in the genome using sophisticated technologies such as high performance capillary electrophoresis and high performance liquid chromatography. These studies are key for standardization of all the techniques described above, because can be applied in a automatized ways in different countries around the world making the results comparable. Third, we have tested a new set of putative DNA demethylating agents and inhibitors of histone deacetylases against human lung cancer cell lines. We have studied the effects of these compounds analyzing the degree of CpG island hypermethylation, the reduction in the Smethylcytosine DNA content and the changes in cell number and the cell cycle phase-induced by the drugs. And fourth, we are making the final transition to the applied clinical part. We study the usefulness of the methylation alterations found in the chapters described above for their benefit in cancer patients in three fronts: As a diagnostic markers of the presence of the malignant disease in patients with lung cancer and theoretically healthy populations. As a prognostic markers for the virulence of the tumors and survival of the patients. As a marker of the efficacy of the new cancer therapies based in epigenetics: the inhibitors of DNA methylation such as 5-aza2-deoxycitidine (Decitabine).