Identificación de marcadores genómicos con valor pronóstico en pacientes diagnosticados de carcinoma de pulmón en estadio temprano mediante microarrays de single nucleotide polimorphisms (SNPS)

Resumo

CHARACTERIZATION OF PRONOSTIC GENOME ABERRATIONS IN EARLY STAGE NSCLC PATIENTS BY USING SINGLE NUCLEOTIDE POLYMORPHISMS MICROARRAYS Lung cancer is the first cause of death by cancer world-wide. In spite of the huge amount of biomedical studies and the development of the screening protocols during the last 20 years, the global survival rate is 16%. Staging is mandatory for treatment adaptation, it is the unique prognostic and predictive factor retrospectively validated. Therefore it has an important impact in patients¿ survival. Early stages of lung cancer are infrequent in patients¿ diagnosis due to its asymptomatic course, but it¿s possible to detect them by screening protocol using low-dose TC. The first line treatment for this stage is the surgery resection of the tumor usually by lobectomy. Despite the high surveillance rate of these patients, around 30% relapse after the surgery. Nowadays we don¿t have any biological markers to define this group of patients in order to propose a more suitable treatment for them. Molecular studies of lung cancer have revealed that it has multiple genomic aberrations. Copy number abnormalities are frequent in tumor progression process, and these abnormal regions have been described in several studies. Single nucleotide polymorphism microarrays (aSNP) permit the study of millions of SNPs in one experiment, and determinate different copy number regions. The aim of this study is the identifications of the prognostic genome aberrations in early stage lung cancer patients, in order to define a poor prognostic group, and propose a more suitable treatment for them. MATERTIAL AND METHODS: We selected an early-stage lung cancer cohort defined by: stage I, adenocarcinoma or squamous lung cell carcinoma, non-radiotherapy or chemotherapy treatment previous or after the surgery and without any history of neoplasic disease in the previous 5 years. Also, we selected a 36 lung cancer cell lines with all histological types. Tumors were processed by laser-capture microdissection. Genomic DNA was processed by GeneChip Human Mapping 500K Arrays protocol. Previous analyzing the patients¿ cohort we evaluate the effect of laser-capture microdissection and intra-tumor heterogeneity in the context of characterization of genomic aberration by aSNP. The bioinformatic analysis was carried out by Partek Genomic Suit in a non-paired experiment (HapMap controls) for the cell lines and GLAD and GISTIC algorithms in a paired design (patients¿ blood). Statistical associations of the regions with clinic-pathological features were carried out by Kaplan-Meier studies and COX multivariate analysis. RESULTS: We described the most representative genomic aberrations in the different histological subtypes in our cell lines; we could identify previous regions described in other studies and new regions which must be studied in order to find out diver genes. Laser-capture microdissection technique showed a clear improve of sensibility for genomic aberrations identification, this effect was higher in the case of LOH regions. We didn¿t find a significant intra-tumor heterogeneity in our samples, and it didn¿t have any effect in aberrations¿ description. Regarding to the stage I patient cohort, the copy number profile was similar to others previously described; we found some different regions because of the specific clinical features of our samples and the usage of laser-capture microdissection. In adenocarcinoma, 1q21.1 amplification and 6q13 deletion were associated to a poor global surveillance rate; in the other hand, patient with 11p11.2 deletions had higher disease-free survival and 6q13 deletion lower. In Squamous carcinoma patients, 7p11.2 and 17q24.3 amplifications and 8q23.3 deletions were associated to a poor disease-free survival and global survival. Finally, 7p11.2 amplification which includes EGFR gene was found as an independent prognostic factor in squamous cell carcinoma patients.