Epidermal growth factor receptor gene polymorphisms are associated with prognostic features of breast cancer.

BACKGROUND: The epidermal growth factor receptor (EGFR) is differently expressed in breast cancer, and its presence may favor cancer progression. We hypothesized that two EGFR functional polymorphisms, a (CA)n repeat in intron 1, and a single nucleotide polymorphism, R497K, may affect EGFR expression and breast cancer clinical profile. METHODS: The study population consisted of 508 Brazilian women with unilateral breast cancer, and no distant metastases. Patients were genotyped for the (CA)n and R497K polymorphisms, and the associations between (CA)n polymorphism and EGFR transcript levels (n = 129), or between either polymorphism and histopathological features (n = 505) were evaluated. The REMARK criteria of tumor marker evaluation were followed. RESULTS: (CA)n lengths ranged from 14 to 24 repeats, comprehending 11 alleles and 37 genotypes. The most frequent allele was (CA)16 (0.43; 95% CI = 0.40-0.46), which was set as the cut-off length to define the Short allele. Variant (CA)n genotypes had no significant effect in tumoral EGFR mRNA levels, but patients with two (CA)n Long alleles showed lower chances of being negative for progesterone receptor (ORadjusted = 0.42; 95% CI = 0.19-0.91). The evaluation of R497K polymorphism indicated a frequency of 0.21 (95% CI = 0.19 - 0.24) for the variant (Lys) allele. Patients with variant R497K genotypes presented lower proportion of worse lymph node status (pN2 or pN3) when compared to the reference genotype Arg/Arg (ORadjusted = 0.32; 95% CI = 0.17-0.59), which resulted in lower tumor staging (ORadjusted = 0.34; 95% CI = 0.19-0.63), and lower estimated recurrence risk (OR = 0.50; 95% CI = 0.30-0.81). The combined presence of both EGFR polymorphisms (Lys allele of R497K and Long/Long (CA)n) resulted in lower TNM status (ORadjusted = 0.22; 95% CI = 0.07-0.75) and lower ERR (OR = 0.25; 95% CI = 0.09-0.71). When tumors were stratified according to biological classification, the favorable effects of variant EGFR polymorphisms were preserved for luminal A tumors, but not for other subtypes. CONCLUSIONS: The data suggest that the presence of the variant forms of EGFR polymorphisms may lead to better prognosis in breast cancer, especially in patients with luminal A tumors.

PTGS2 polymorphism rs689466 favors breast cancer recurrence in obese patients.

Breast cancer is the leading cancer among women, and its increasing incidence is a challenge worldwide. Estrogen exposure is the main risk factor, but obesity among postmenopausal women has been shown to favor disease onset and progression. The link between obesity and mammary carcinogenesis involves elevated estrogen production and proinflammatory stimuli within the adipose tissue, with activation of the cyclooxygenase-2 pathway. Here, we evaluate the impact of the four most common cyclooxygenase-2 gene polymorphisms (rs689465, rs689466, rs20417 and rs20417), in combination with obesity, on the risk of breast cancer progression in a cohort of Brazilian breast cancer patients (N = 1038). Disease-free survival was evaluated using Kaplan-Meier curves, with multivariate Cox proportional hazards regression models for calculation of adjusted hazard ratios (HRadj). Obesity did not affect disease progression, whereas rs689466 variant genotypes increased the recurrence risk among obese patients (HRadj = 2.5; 95% CI = 1.4-4.3), either for luminal (HRadj = 2.2; 95% CI = 1.1-4.2) or HER2-like and triple-negative tumors (HRadj = 3.2; 95% CI = 1.2-8.5). Likewise, the haplotype *4, which contains variant rs689466, was associated with shorter disease-free survival among obese patients (HRadj = 3.3; 95% CI = 1.8-6.0), either in luminal (HRadj = 3.5; 95% CI = 1.6-7.3) or HER2-like and triple-negative (HRadj = 3.1; 95% CI = 1.1-8.9) tumors. Such deleterious impact of variant rs689466 on disease-free survival of obese breast cancer patients was restricted to postmenopausal women. In conclusion, cyclooxygenase-2 genotyping may add to the prognostic evaluation of obese breast cancer patients.

Loss of constitutive ABCB1 expression in breast cancer associated with worse prognosis.

ABCB1 gene encodes an adenosine 5'-triphosphate-binding cassette transporter, which not only confers multidrug resistance phenotype in malignant cells, but is also present in several nonmalignant tissues. For the last thirty years, ABCB1 expression in breast cancer has been described by many authors, but the extent of expression differs among the studies, and there is no consensus regarding its potential role in carcinogenesis or in the tumor response to antineoplastic drugs. This study aimed to characterize the expression of ABCB1 in breast tumors as a function of genetic, clinical, and histopathological variables. The ABCB1 expression was also evaluated in nonmalignant mammary tissues adjacent to tumors and in benign lesions. The detection of ABCB1 protein was performed by immunohistochemistry in tissue specimens of excised breasts obtained from a prospective cohort of Brazilian women with breast cancer. The association of ABCB1 protein levels with ABCB1 mRNA, gene polymorphisms, and clinical and histopathological variables was also evaluated. The Kaplan-Meier curves and multivariate Cox regression analyses were conducted to identify independent predictors of disease-free survival of patients with breast cancer. ABCB1 was detected in 86.3% (656) of breast tumors, 98.8% (606) of nonmalignant mammary tissue adjacent to tumors, and 100% (28) of benign lesions. Reduced ABCB1 protein levels in breast tumors was associated with triple-negative subtype (adjusted odds ratio [ORadj] =0.24; 95% confidence interval [CI] =0.13-0.45), lymph node status < pN2 (ORadj =0.27; 95% CI =0.10-0.71), tumor size >2 cm (ORadj =0.55; 95% CI =0.32-0.93), and hypertensive status (ORadj =0.42; 95% CI =0.24-0.73), and it was significantly associated with shorter disease-free survival, either for all breast cancer patients (p log-rank =0.012; hazard ratio [HR] =3.46; 95% CI =1.21-9.91) or for those with triple-negative tumors (p log-rank =0.007; HR =11.41; 95% CI =1.29-100.67). The loss of constitutive ABCB1 expression in breast cancer, especially in triple-negative tumors, seems to indicate a subgroup of worse prognosis.

Caracterização de polimorfismos do gene PTGS2 na população brasileira e avaliação quanto ao risco de desenvolvimento de câncer de mama

A enzima inflamatória ciclooxigenase-2 (COX-2) encontra-se com alta expressão em diversos tipos de câncer e está associada à progressão, potencial de invasão e metástase. A COX-2 é codificada pelo gene PTGS2, que é polimórfico e apresenta variações na região promotora (RP) e na região 3’-não traduzida (3´-UTR). Tais variantes podem contribuir para aumentar a transcrição ou a estabilidade do RNAm, favorecendo um efeito pró-inflamatório e podendo aumentar o risco de desenvolvimento de câncer. A freqüência de polimorfismos em PTGS2 varia entre grupos étnicos e, até o momento, não há informações quanto à distribuição genotípica em brasileiros saudáveis ou com câncer. Este trabalho teve como objetivo geral a caracterização de variações no gene PTGS2 em brasileiros, a fim de avaliar se tais variações podem afetar o risco de desenvolvimento de câncer de mama. O protocolo utilizado foi aprovado pelo Comitê de Ética em Pesquisa do INCA e todos os participantes assinaram o Termo de Consentimento Livre e Esclarecido. A etapa de rastreamento de polimorfismos foi realizada em sete fragmentos da região promotora e em três da região 3’-UTR, com os métodos de dHPLC ou PCR-RFLP. Nós recrutamos 282 voluntários sadios com o objetivo de caracterizar as freqüências alélicas e as distribuições genotípicas e avaliar as possíveis diferenças entre sexo e cor de pele. Foram identificados nove polimorfismos já descritos em outras populações, com as seguintes freqüências alélicas: -1290AG (0,22), -1195AG (0,15), - 1131GA (0,007), -765GC (0,32), -604TC (0,015), -163CG (0,02) e -62CG(0,007), 8473TC (0,22) e 9850AG (0,01). Todas as distribuições genotípicas estavam em equilíbrio de Hardy-Weinberg (Eq-HW) e não houve diferenças em relação ao sexo. O polimorfismo 8473TC foi o único que apresentou diferença na distribuição genotípica em função da cor de pele (P = 0,034), sendo menos freqüente em brancos do que em pardos ou pretos. Os polimorfismos com freqüência maior que 10% foram selecionados para o estudo caso-controle em câncer de mama que envolveu 131 voluntárias sadias e 216 pacientes. As freqüências alélicas encontradas para as variações -1290AG, -1195AG, -765GC e 8473TC foram, respectivamente, de 0,16 (IC95% 0,11-0,21), 0,13 (IC95% 0,09- 0,18), 0,31 (IC95% 0,25-0,37), 0,24 (IC95% 0,18-0,30) em voluntárias e 0,17 (IC95% 0,13-0,20), 0,1 (IC95% 0,07-0,13), 0,31 (IC95% 0,26-0,35) e 0,31 (IC95% 0,26-0,35) em pacientes. Nós encontramos uma relação significativa ente o polimorfismo 8473TC e o risco para câncer de mama, com uma odds ratio (OR) de 1,73 (IC95% 1,08-2,77; P = 0,024) para a população total do estudo caso-controle e OR de 2,54 (IC95% 1,21-5,32; P = 0,017) apenas entre mulheres brancas. Além dos polimorfismos de PTGS2 outros fatores de risco para câncer de mama, como idade, tabagismo e histórico familiar de câncer foram avaliados...

The inflammatory enzyme ciclooxigenase-2 (COX-2) is over expressed in several types of cancer and its presence is associated with progression, invasive potential and metastasis. The gene encoding human COX-2 (PTGS2) is polymorphic and many variants have been described in the promoter region and in the 3’-untranslated (3’-UTR) region. These polymorphisms may affect gene transcription or RNAm stability, and thereby favor the synthesis of COX-2 and a pro-inflammatory effect, which might increase the risk of cancer. The frequency of PTGS2 polymorphisms varies between ethnic groups and, until now, there have been no reports about its distribution in Brazilians. The objective of our study was to characterize PTGS2 polymorphisms occurring in the Brazilian population in order to evaluate the role of selected variants as risk factors for breast cancer. The protocol was approved by the local ethics committee and all participants signed a consent form. The screening of PTGS2 polymorphisms was performed in seven fragments of the promoter region and in three fragments in the 3'–UTR region by dHPLC or PCR-RFLP. We recruited 282 healthy volunteers in order to characterize allelic frequencies and genotypic distributions and to evaluate possible differences according to gender or skin color. We identified nine polymorphisms with the following allelic frequencies: -1290AG (0.22), - 1195AG (0.15), -1131GA (0.007), -765GC (0.32), -604TC (0.015), -163CG (0.02), -62CG (0.007), 8473TC (0.22) and 9850AG (0.01). All genotypic distributions followed Hardy-Weinberg equilibrium and no differences were observed in relation to gender. The 8473TC polymorphism was the only one which showed different genotypic distributions in Brazilian color groups (P = 0.034), being less frequent in whites that in intermediate or black volunteers. The polymorphisms with minor allele frequencies higher than 0.10 were selected for the case-control study in breast cancer, which involved 131 healthy women and 216 patients. The frequencies of the variant alleles -1290G, -1195G, -765C and 8473C were respectively: 0.16 (CI95% 0.11-0.21), 0.13 (CI95% 0.09-0.18), 0.31 (CI95% 0.25-0.37) and 0.24 (CI95% 0.18-0.30) among healthy controls and 0.17 (CI95% 0.13-0.20), 0.10 (CI95% 0.07-0.13), 0.31 (CI95% 0.26-0.35) and 0.31 (CI95% 0.26-0.35) among patients. We found a significant association between 8473TC polymorphism and breast cancer risk, with an odds ratio (OR) of 1.73 (CI95% 1.08 - 2.77; P = 0.024) in the general study population and an OR of 2.54 (CI95% 1.21- 5.32; P = 0.017) among white women. Besides the PTGS2 polymophisms, we evaluated the contribution of other possible risk factors for breast cancer, namely: age, smoking and family history of cancer. We found significant association only for age (OR = 1,65; CI95% 1,07-2,54). The results suggest that the polymorphism 8473TC located in the 3‘-UTR region of PTGS2 gene may be a risk factor for development of breast cancer in Brazilian women.