RESUMO
Molecular classification of colorectal cancer (CRC) is currently based on microsatellite instability (MSI), KRAS or BRAF mutation and, occasionally, chromosomal instability (CIN). Whilst useful, these categories may not fully represent the underlying molecular subgroups. We screened 906 stage II/III CRCs from the VICTOR clinical trial for somatic mutations. Multivariate analyses (logistic regression, clustering, Bayesian networks) identified the primary molecular associations. Positive associations occurred between: CIN and TP53 mutation; MSI and BRAF mutation; and KRAS and PIK3CA mutations. Negative associations occurred between: MSI and CIN; MSI and NRAS mutation; and KRAS mutation, and each of NRAS, TP53 and BRAF mutations. Some complex relationships were elucidated: KRAS and TP53 mutations had both a direct negative association and a weaker, confounding, positive association via TP53-CIN-MSI-BRAF-KRAS. Our results suggested a new molecular classification of CRCs: (1) MSI(+) and/or BRAF-mutant; (2) CIN(+) and/or TP53(-) mutant, with wild-type KRAS and PIK3CA; (3) KRAS- and/or PIK3CA-mutant, CIN(+) , TP53-wild-type; (4) KRAS(-) and/or PIK3CA-mutant, CIN(-) , TP53-wild-type; (5) NRAS-mutant; (6) no mutations; (7) others. As expected, group 1 cancers were mostly proximal and poorly differentiated, usually occurring in women. Unexpectedly, two different types of CIN(+) CRC were found: group 2 cancers were usually distal and occurred in men, whereas group 3 showed neither of these associations but were of higher stage. CIN(+) cancers have conventionally been associated with all three of these variables, because they have been tested en masse. Our classification also showed potentially improved prognostic capabilities, with group 3, and possibly group 1, independently predicting disease-free survival.
Assuntos
Biomarcadores Tumorais/genética , Instabilidade Cromossômica , Neoplasias Colorretais/classificação , Neoplasias Colorretais/genética , Técnicas de Diagnóstico Molecular/métodos , Mutação , Proteínas de Neoplasias/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Classe I de Fosfatidilinositol 3-Quinases , Neoplasias Colorretais/mortalidade , Intervalo Livre de Doença , Feminino , Humanos , Masculino , Instabilidade de Microssatélites , Pessoa de Meia-Idade , Análise Multivariada , Estadiamento de Neoplasias , Fosfatidilinositol 3-Quinases/genética , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas B-raf/genética , Proteínas Proto-Oncogênicas p21(ras) , Ensaios Clínicos Controlados Aleatórios como Assunto , Fatores Sexuais , Succinimidas , Proteína Supressora de Tumor p53/genética , Proteínas ras/genéticaRESUMO
Association studies using SNPs provides one of the best tools that we have at the moment for looking for genes involved in physical traits. However the studies should be carefully designed from the very beginning in all the steps of the procedure: pre-genotyping, genotyping and the mathematical analysis of the results. If the actual knowledge is correctly applied in the design of the study the probability of being successful in finding an association can be considerably increased. Improved statistical analysis techniques are helping in the robustness of the findings. The current consensus from the literature indicates that this would be a good time to investigate complex or quantitative traits via dense SNP genotyping, and a number of studies have been published, providing potential models. The state of the art of candidate genes for pigmentation, stature and facial morphology is described.
