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Doctoral Thesis
DOI
https://doi.org/10.11606/T.5.2008.tde-29012009-144143
Document
Author
Full name
Otávio Alberto Curioni
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2008
Supervisor
Committee
Gattas, Gilka Jorge Figaro (President)
Camargo, Roberto Souza
Longatto Filho, Adhemar
Massad, Eduardo
Rapoport, Abrão
Title in Portuguese
Poliformismos genéticos no câncer de cabeça e pescoço: análise de risco e evolução clínica
Keywords in Portuguese
Glutationa s-transferase
Neoplasias bucais
Neoplasias de cabeça e pescoço
Polimorfismo genético
Prognóstico
Abstract in Portuguese
O carcinoma epidermóide de cabeça e pescoço (CECP) é considerado um dos tumores mais freqüentes em países em desenvolvimento, detectado quase sempre em estádios mais avançados, com poucas opções eficazes de tratamento, o que diminui a taxa de sobrevida para cinco anos em 50%. Os principais fatores de risco associados são consumo de tabaco e de álcool, seguidos da dieta e infecções virais. Não parecem existir até o momento métodos de vigilância, biomarcadores moleculares ou quimioprevenção que tenham se mostrado eficientes. A identificação de polimorfismos em genes de metabolização do tabaco e do álcool tem sido sugerida na busca de marcadores de susceptibilidade individual ao CECP. Dentre as enzimas envolvidos na fase I de metabolização incluem-se as da família do citocromo P450 (CYPs) e da fase II de metabolização as enzimas glutationa S-transferases (GSTs). Incluem-se também os polimorfismos em genes de reparo que podem alterar o risco para desenvolvimento CECP, sobretudo nos indivíduos consumidores de álcool e tabaco. Polimorfismos em CYPs e GSTs podem alterar a dinâmica de metabolização e excreção de carcinógenos aumentando o risco de mutações como adutos de DNA e conseqüentemente o câncer. No presente estudo foram avaliados polimorfismos em genes da fase I (CYP1A1 MspI, CYP2E1 PstI) da fase II (GSTM1, GSTT1, GSTP1 BsmA) e no gene de reparo XRCC1, em 207 pacientes portadores de CECP, dos quais 92 (44%) com carcinoma epidermóide da cavidade bucal (CECB), e em 244 controles, selecionados no mesmo hospital. A identificação dos polimorfismos a partir do DNA de linfócitos periféricos dos pacientes e controles (PCR-RFLP) revelou maior freqüência do genótipo GSTM1 nulo em pacientes com CECP (53,2%) quando comparados aos controles (37,7%), aumentando em aproximadamente cinco vezes o risco da doença (OR = 4,75; IC 95%, 3,06-7,40). Resultados semelhantes para o genótipo GSTM1 nulo foram encontrados nos casos de CECB (OR = 2,15; IC 95%, 1,28-3,6). Verificou-se também aumento no risco de CECB com o genótipo XRCC1-194Trp (OR = 2,33; IC 95%, 1,08-4,98) e proteção associada ao genótipo XRCC1-399Gln (OR, 0.35; IC 95%, 0.12-0.96) que foi mais prevalente nos controles do que nos pacientes com CECB. A presença simultânea de dois genes desfavoráveis (associação gene-gene) aumentou em torno de duas vezes o risco de CECB quando associados GSTM1-CYP1A1 (OR=1,93; IC 95%, 1,1-3,3), GSTM1-CYP2E1 (OR=2,2; IC 95%, 1,36-3,87), GSTM1-XRCC1-194 (OR=2,44; IC 95%, 1,44-4,14) e CYP2E1-XRCC1-194 (OR=2,0; IC 95%, 1,1 3,62). Quando considerada na análise a interação gene-ambiente verificamos que pacientes com CECB que consumiam acima de 39 maços/ano tinham risco aumentado de câncer associado aos genótipos GSTP1 BmsA (OR = 5,0; IC 95%, 1,9 -12,4) e acima de 20 maços/ano com o genótipo CYP1A1MstI (OR = 53,7; IC 95%, 1,0 -14,2). Por outro lado, o consumo acima de 30 g/l/d, associado ao genótipo XRCC1-194 aumentou oito vezes o risco de CECB (OR = 8,8,; IC 95%, 1,3-45,7) e o genótipo XRCC1-399 parece ter sido um fator de proteção ao CECB mesmo com consumo de álcool acima de 5 a 30 g/l/d (OR = 0,1; IC 95%, 0,03 0,7). Os resultados obtidos parecem sugerir uma contribuição dos polimorfismos genéticos de metabolização do álcool e do tabaco no risco de CECP e da cavidade bucal. A identificação de marcadores genéticos de suscetibilidade individual ao câncer pode auxiliar o médico na indicação de medidas de prevenção e de controle no acompanhamento de pacientes ou da população de risco ao CECP, principalmente fumantes e alcoolistas crônicos.
Title in English
Genetic polymorphisms in head and neck cancer: analysis of risk and clinical evolution
Keywords in English
Genetic polimorphisms
Glutathione s-transferase
Head and neck neoplsms
Mouth neoplasms
Prognosis
Abstract in English
The squamous cell carcinoma of the head and neck (HNSCC) is considered one of the most prevalent cancers in developing countries, detected nearly always in well-advanced phases with few effective treatment options, which reduce the survival rate to five years in 50% of the patients. The main risk factors associated with it are tobacco and alcohol intake, followed by diet and viral infections. For the moment, there seems not to be vigilance methods, molecular biomarkers or chemioprevention that have been shown to be efficient. The identification of polymorphisms in tobacco and alcohol metabolizing genes has been suggested in the search for markers of individual susceptibility to the HNSCC. Among the enzymes involved in the metabolizing phase I are those belonging to the P450 cytochrome family (CYPs) while in the metabolizing phase II are included the glutathione S-transferases (GSTs). The repair gene polymorphisms which may alter the risk of developing HNSCC, especially in alcohol and tobacco consumers are also included. Polymorphisms in CYPs and GSTs may alter the metabolizing dynamics and carcinogen excretion increasing the risk of mutations like DNA adducts and, as a consequence, the risk of cancer. In the present study, polymorphisms in phase I genes (CYP1A1 MspI, CYP2E1 PstI) and in Phase II genes (GSTM1, GSTT1, GSTP1 BsmA) were evaluated, and the repair gene XRCC1 as well, in 207 HNSCC carriers, 92 of them (44%) with oral squamous cell carcinoma (OSCC), and also in 244 controls selected in the same hospital. The identification of polymorphisms from the DNA of peripheral lymphocytes in patients and control subjects (PCR-RFLP) showed greater prevalence of the GSTM1 null genotype which was higher in patients with HNSCC (53.2%) when compared to the controls (37.7%), increasing about five times as much the risk for the disease (OR = 4.75; 95% CI, 3.06-7.40). Similar results for the GSTM1 null genotype were found in the OSCC (OR = 2.15; 95% CI, 1.28-3.6). It was also observed that there was a rise in the risk for OSCC with the XRCC1-194Trp (OR = 2.33; 95% CI, 1.08-4.98) genotype and some protection associated with the XRCC1-399Gln (OR, 0.35; 95% CI, 0.12-0.96) genotype, which was more prevalent in the control subjects than in the OSCC patients. The simultaneous presence of two unfavourable genes (gene-gene association) approximately doubled the risk for OSCC when GSTM1-CYP1A1 (0R=1.93; 95% CI, 1.1-3.3), GSTM1-CYP2E1 (0R=2.2; CI 95%, 1.36-3.87), GSTM1-XRCC1-194 (OR=2.44; CI 95%, 1.44-4.14) and CYP2E1-XRCC1-194 (OR=2.0; CI 95%, 1.1 3.62) were associated. When the interaction gene-environment was considered in the analysis, it was found that OSCC patients who were used to consuming above 39 cigarette packs a year had an increase in the risk of getting cancer associated with the GSTP1 BmsA (OR=5.0; CI 95%, 1.9-12.4) genotypes and above 20 packs a year associated with the CYP1A1MstI (OR = 53.7; CI 95%, 1.0 - 14.2) genotype. On the other hand, the above-30-g/l/d consumption associated with the XRCC1-194 genotype raised eight times as much the risk for ECOC (OR=8,8; CI 95%, 1.3-45.7) and the XRCC1-399 genotype seems to have been a protection factor against ECOC even with alcohol consumption above 5 to 30 g/l/d (OR=0.1; CI 95%, 0.03 0.7). The results obtained seem to suggest a contribution of the genetic polymorphisms of the alcohol-and-tobacco-related metabolizing enzymes to HNSCC and the OSCC. The identification of genetic markers of individual susceptibility to cancer may help the clinician with the indication of prevention and control measures for the medical follow-up of patients or the population at risk of contracting SCCHN, mainly chronic smokers and alcoholics.
 
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Publishing Date
2009-02-13
 
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