Re: Integrin 3 Leu33Pro Homozygosity and Risk of Cancer

Common rs5918 (PlA1/A2) polymorphism in the ITGB3 gene and risk of coronary artery disease

INTRODUCTION

The T to C transition at nucleotide 1565 of the human glycoprotein IIIa (ITGB3) gene represents a genetic polymorphism (PlA1/A2) that can influence both platelet activation and aggregation and that has been associated with many types of disease. Here, we present a newly designed multiplex tetra-primer amplification refractory mutation system - polymerase chain reaction (T-ARMS-PCR) for genotyping a single nucleotide polymorphism (SNP) (dbSNP ID: rs5918) in the human ITGB3 gene.

MATERIAL AND METHODS

We set up T-ARMS-PCR for the rs5918 SNP in a single-step PCR and the results were validated by the PCR-RFLP method in 132 coronary artery disease (CAD) patients and 122 unrelated healthy individuals.

RESULTS

Full accordance was found for genotype determination by the PCR-RFLP method. The multiple logistic regression analysis showed a significant association of the rs5918 polymorphism and CAD according to dominant and recessive models (dominant model OR: 2.40, 95% CI: 1.33-4.35; p = 0.003, recessive model OR: 4.71, 95% CI: 1.32-16.80; p = 0.0067).

CONCLUSIONS

Our T-ARMS-PCR in comparison with RFLP and allele-specific PCR is more advantageous because this PCR method allows the evaluation of both the wild type and the mutant allele in the same tube. Our results suggest that the rs5918 (PlA1/A2) polymorphism in the ITGB3 gene may contribute to the susceptibility of sporadic Iranian coronary artery disease (CAD) patients.

Breast cancer genomics based on biobanks

Attempts to find genes contribution to complex diseases, such as cancer, require new study designs which incorporate an efficient use of population resources and modern genotyping technologies. We describe here two approaches, used by us for the study of breast cancer, both of which take the use of biobanks. One uses a cancer registry as a source of case information, which is then linked to a biobank on blood DNA. The biobank provides also samples from matched controls. After genotyping, clinical data are retrieved from hospital records, and the results can be presented for genotype-specific cancer risks, or similarly for genotype-specific clinical and survival parameters. The second approach uses registered data on cancer in families or among twins. On defined groups of patients, paraffin tissue is collected by contacting the pathology departments of the hospitals where the patients were diagnosed. Tumor and healthy tissue is prepared and used for mutation, the loss of heterozygosity, or copy number analysis. We believe that in the era of whole-genome genotyping technologies, the importance of well-characterized sample sets cannot be overemphasized. Samples rather than technologies limit the rate of gene discovery in complex diseases.

The Leu33Pro polymorphism in the ITGB3 gene does not modify BRCA1/2-associated breast or ovarian cancer risks: results from a multicenter study among 15,542 BRCA1 and BRCA2 mutation carriers

Integrins containing the beta(3) subunit are key players in tumor growth and metastasis. A functional Leu33Pro polymorphism (rs5918) in the beta(3) subunit of the integrin gene (ITGB3) has previously been suggested to act as a modifier of ovarian cancer risk in Polish BRCA1 mutation carriers. To investigate the association further, we genotyped 9,998 BRCA1 and 5,544 BRCA2 mutation carriers from 34 studies from the Consortium of Investigators of Modifiers of BRCA1/2 for the ITGB3 Leu33Pro polymorphism. Data were analysed within a Cox-proportional hazards framework using a retrospective likelihood approach. There was marginal evidence that the ITGB3 polymorphism was associated with an increased risk of ovarian cancer for BRCA1 mutation carriers (per-allele Hazard Ratio (HR) 1.11, 95% CI 1.00-1.23, p-trend 0.05). However, when the original Polish study was excluded from the analysis, the polymorphism was no longer significantly associated with ovarian cancer risk (HR 1.07, 95% CI 0.96-1.19, p-trend 0.25). There was no evidence of an association with ovarian cancer risk for BRCA2 mutation carriers (HR 1.09, 95% CI 0.89-1.32). The polymorphism was not associated with breast cancer risk for either BRCA1 or BRCA2 mutation carriers. The ITGB3 Leu33Pro polymorphism does not modify breast or ovarian cancer risk in BRCA1 or BRCA2 mutation carriers.

Polymorphisms in predicted microRNA-binding sites in integrin genes and breast cancer: ITGB4 as prognostic marker

Integrins control the cell attachment to the extracellular matrix and play an important role in mediating cell proliferation, migration and survival. A number of important cancer-associated integrin genes can be regulated by microRNAs (miRNAs) that bind to their target sites in the 3' untranslated regions. We examined the effect of single-nucleotide polymorphisms (SNPs) in predicted miRNA target sites of six integrin genes (ITGA3, ITGA6, ITGAv, ITGB3, ITGB4 and ITGB5) on breast cancer (BC) risk and clinical outcome. Six SNPs were genotyped in 749 Swedish incident BC cases with detailed clinical data and up to 15 years of follow-up together with 1493 matched controls. We evaluated associations between genotypes and BC risk and clinical tumour characteristics. Survival probabilities were compared between different subgroups. As a novel finding, several SNPs seemed to associate with the hormone receptor status. The strongest association was observed between the A allele of the SNP rs743554 in the ITGB4 gene and oestrogen receptor-negative tumours [odds ratio 2.09, 95% confidence intervals (CIs) 1.19-3.67]. The same SNP was associated with survival. The A allele carriers had a worse survival compared with the wild-type genotype carriers (hazard ratio 2.11, 95% CIs 1.21-3.68). The poor survival was significantly associated with the aggressive tumour characteristics: high grade, lymph node metastasis and high stage. None of the SNPs was significantly associated with BC risk. As the ITGB4 SNP seems to influence tumour aggressiveness and survival, it may have prognostic value in the clinic.

Integrin beta3 Leu33Pro polymorphism increases BRCA1-associated ovarian cancer risk

Integrins are heterodimeric transmembrane glycoproteins that function as key adhesion and cell signalling receptors. A functional polymorphism in the integrin beta3 subunit encoded by the ITGB3 gene, Leu33Pro, has been shown to modify a variety of traits of beta3-expressing cells. To analyse the role of this functional polymorphism in modifying BRCA1-associated ovarian and breast cancer risks, a case-control study was performed among Polish BRCA1 mutation carriers including 319 breast cancer cases, 146 ovarian cancer cases and 290 controls unaffected by breast and ovarian cancer, in situ breast cancer or any other kind of cancer. Genotyping analysis was performed using PCR-based restriction fragment length polymorphism analysis. Odds ratios were calculated using univariate and multivariate logistic regression, taking into account a series of confounding variables, including the presence of related study subjects, that potentially could have biased any association. The results revealed that the ITGB3_Leu33Pro polymorphism was associated with a 2.5-fold increased risk of ovarian cancer, whereas no association with breast cancer risk was found. Thus, it appears that the ITGB3_Leu33Pro polymorphism may potentially increase the risk of ovarian cancer in Polish women with an inherited BRCA1 mutation.

No association of breast cancer risk with integrin beta3 (ITGB3) Leu33Pro genotype

To pursue a borderline increased risk of breast cancer for carriers of two integrin beta₃ (ITGB3) 33Pro alleles found in a recent prospective study, we conducted a case–control study of 1088 women with breast cancer and 4815 female controls. Leu33Pro heterozygotes, homozygotes and heterozygotes+homozygotes vs noncarriers had odds ratios for breast cancer of 1.0 (95% confidence interval: 0.8–1.1), 0.8 (0.5–1.2) and 1.0 (0.8–1.1), respectively. After stratification for conventional risk factors, odds ratio for breast cancer in heterozygotes, homozygotes and heterozygotes+homozygotes vs noncarriers were not increased above 1.0 in any of the 14 strata examined. This was also true after stratification for tumour histological subtype and cancer stage at the time of diagnosis.

Integrin ?3 Leu33Pro polymorphism and breast cancer risk: a population-based case-control study in Germany

A functional polymorphism at codon 33 (leucine-to-proline, Leu33Pro)/nucleotide 1565 (T-to-C, T1565C) of the integrin beta3 has been hypothesized to increase the risk of breast cancer and its metastasis. Three studies have been conducted up to date and the results were contradictory. We used a large population-based age-matched case-control study in German Caucasian women by the age of 50 years to assess breast cancer risk associated with this polymorphism, taking into consideration of possible interaction with other risk factors, and to examine if it affects clinical presentation. Overall, the odds ratios (OR) for breast cancer were not increased in women carrying either allele. However, we observed a differential effect of the Leu33Pro polymorphism by age group when patients were stratified by 45 years of age (p=0.055). Being a carrier of the 33proline allele was found to be associated with a 32% increased risk (95% Cl=1.0-1.8) for breast cancer compared to the wild-type leucine homozygotes among women age 45 or younger but not in older women. Furthermore, we observed significant dose effect of the 33proline allele (p=0.04), with 30% risk increase per allele (95% Cl=1.0-1.7). Significant evidence was also found for a positive association between 33proline carrier status and increasing axillary node involvement (p=0.048) but neither size nor grading of tumor in this study. Our data suggest that inheritance of the integrin beta3 Leu33Pro polymorphism may increase the breast cancer risk by age 45 in the German population.

Genetic epidemiology of cancer: From families to heritable genes

A reliable determination of familial risks for cancer is important for clinical counseling, prevention and understanding cancer etiology. Family-based gene identification efforts may be targeted if the risks are well characterized and the mode of inheritance is identified. Medically verified data on familial risks have not been available for all types of cancer but they have become available through the use of the nationwide Swedish Family-Cancer Database, which includes all Swedes born in 1932 and later with their parents, totaling over 10 million individuals. Over 150 publications have emanated from this source. The familial risks of cancer have been characterized for all main cancers and the contribution of environmental and heritable effects to the familial aggregation has been assessed. Furthermore, the mode of inheritance has been deduced by comparing risks from parental and sibling probands. Examples are shown on familial clustering of cancers, for which heritable susceptibility genes are yet unknown, such as squamous cell carcinoma of the skin, intestinal carcinoids, thyroid papillary tumors, brain astrocytomas and pituitary adenomas. Some common cancers, such as lung and kidney cancers, appear to show an early-onset recessive component because familial risks among siblings are much higher than those in families where parents are probands. Many of the cancer sites showing high familial risks lack guidelines for clinical counseling or action level. In conclusion, we recommend that any future gene identification efforts, either using linkage or association designs, devise their strategies based on data from family studies. Clinical genetic counseling would benefit from reviewing established familial risks on all main types of cancer.