Anna Jakubowska

Contribution of Germline Mutations in the RAD51B, RAD51C, and RAD51D Genes to Ovarian Cancer in the Population

PURPOSE The aim of this study was to estimate the contribution of deleterious mutations in the RAD51B, RAD51C, and RAD51D genes to invasive epithelial ovarian cancer (EOC) in the population and in a screening trial of individuals at high risk of ovarian cancer. PATIENTS AND METHODS The coding sequence and splice site boundaries of the three RAD51 genes were sequenced and analyzed in germline DNA from a case-control study of 3,429 patients with invasive EOC and 2,772 controls as well as in 2,000 unaffected women who were BRCA1/BRCA2 negative from the United Kingdom Familial Ovarian Cancer Screening Study (UK_FOCSS) after quality-control analysis. RESULTS In the case-control study, we identified predicted deleterious mutations in 28 EOC cases (0.82%) compared with three controls (0.11%; P < .001). Mutations in EOC cases were more frequent in RAD51C (14 occurrences, 0.41%) and RAD51D (12 occurrences, 0.35%) than in RAD51B (two occurrences, 0.06%). RAD51C mutations were associated with an odds ratio of 5.2 (95% CI, 1.1 to 24; P = .035), and RAD51D mutations conferred an odds ratio of 12 (95% CI, 1.5 to 90; P = .019). We identified 13 RAD51 mutations (0.65%) in unaffected UK_FOCSS participants (RAD51C, n = 7; RAD51D, n = 5; and RAD51B, n = 1), which was a significantly greater rate than in controls (P < .001); furthermore, RAD51 mutation carriers were more likely than noncarriers to have a family history of ovarian cancer (P < .001). CONCLUSION These results confirm that RAD51C and RAD51D are moderate ovarian cancer susceptibility genes and suggest that they confer levels of risk of EOC that may warrant their use alongside BRCA1 and BRCA2 in routine clinical genetic testing.

Germline 657del5 mutation in the NBS1 gene in breast cancer patients

In this report the proportion of consecutive and familial breast cancer cases harboring the 657del5 of exon 6 of the NBS1 gene was determined to assess whether it is associated with the increased risk of breast cancer development. The study consisted of 3 groups of patients: a series of consecutive 150 patients with histologically confirmed breast cancer, diagnosed under the age of 50 in the city of Szczecin; a series of 80 breast cancer patients with a family history of breast cancer in their first‐degree relatives; and a series of 530 consecutive individuals without the diagnosis of breast cancer selected at random by family doctors from the city of Szczecin. Molecular examination included allele‐specific PCR assay for the common Slavic NBS1 mutation (657del5), LOH analysis using denucleotide CA repeat microsatellite markers, haplotype analysis and sequencing. The NBS1 founder mutation was detected in 2 of 150 (1.3%) consecutive breast cancer cases diagnosed under the age of 50 years; in 3 of 80 familial breast cancer cases (3.7%); and in 3 of 530 individuals (0.6%) from the general population. Examination of tumor DNA from patients with the NBS1 mutation (groups A and B) revealed loss of heterozygosity (LOH) in all cases. Additional haplotype analysis revealed that allelic loss affects specifically wild‐type alleles. The majority of probands with breast cancer and the NBS1 mutation had a positive family history of breast cancer in their first‐degree relatives. It appears that the 657del5 mutation in exon 6 of the NBS1 gene is responsible for the occurrence of a small but significant proportion of familial breast cancer patients.

BRCA1-associated breast and ovarian cancer risks in Poland: no association with commonly studied polymorphisms

Polymorphisms in genes involved in DNA repair, steroid hormone biosynthesis/metabolism/signaling, folate metabolism as well as cell growth are prime candidates for possible associations with breast and ovarian cancer risk in women with an inherited predisposition. We investigated 29 polymorphisms in 20 genes encoding key proteins of the above four biological pathways for their breast and ovarian cancer risk modifying effect in Polish women harboring BRCA1 founder mutations. Of the analyzed genes, ERCC2, XRCC1, XRCC2, XRCC3 and Lig4 participate in DNA repair, TP53 in cell cycle check point control, AIB1, AR, COMT, CYP11A1, CYP17A1, CYP19A1, HSD17 and PGR in steroid hormone biosynthesis/metabolism/signaling, TYMS in folate metabolism and HER2, IL6, LRP1, TGFB and TGFBR1 affect cell growth. Using validated methods, we genotyped 319 breast cancer cases, 146 ovarian cancer cases and 290 unaffected controls, all of whom harbored one of three causative mutations in BRCA1. Our results revealed no association of any of the investigated polymorphisms with BRCA1-associated breast or ovarian cancer risk. Thus, it appears that these polymorphisms do not influence disease risk in Polish women carrying one of the three common BRCA1 founder mutations.

The VEGF_936_C>T 3'UTR polymorphism reduces BRCA1-associated breast cancer risk in Polish women.

The vascular endothelial growth factor (VEGF) plays a crucial role in the initiation of angiogenesis, which is an important stage in tumor development. A functional 936_C>T polymorphism in the VEGF gene and its association with sporadic breast cancer risk has been analyzed in various studies yielding conflicting results. To analyze the role of this polymorphism in modifying hereditary breast and ovarian cancer risks, we conducted a case-control study and genotyped 755 Polish BRCA1 carriers, including 319 breast cancer cases, 146 ovarian cancer cases, and 290 unaffected controls. The results revealed an association of the CT+TT genotypes with a reduced breast cancer risk (OR(adj) 0.63, 95% CI, 0.41-0.98; OR(clustered) 0.63, 95% CI, 0.48-0.83), and a potential effect on ovarian cancer risk (OR(adj) 0.62, 95% CI, 0.33-1.18; OR(clustered) 0.62, 95% CI, 0.47-0.83). Thus, the 936_C>T polymorphism appears to modify disease risks in BRCA1 carriers.

A high frequency of BRCA2 gene mutations in Polish families with ovarian and stomach cancer

Germ-line mutations in the BRCA2 gene are associated with a wide range of cancer types, including the breast, ovary, pancreas, prostate and melanoma. In this study, we evaluated the importance of a family history of stomach cancer in predicting the presence of a BRCA2 mutation in Polish patients with ovarian cancer. A BRCA2 mutation was found in eight of 34 women with ovarian cancer and a family history of stomach cancer versus three of 75 women with ovarian cancer and a family history of ovarian cancer, but not of stomach cancer (odds ratio=7.4; 95% CI 1.8–30; P=0.004). The results of this study suggest that, in the Polish population, the constellation of ovarian and stomach cancer predicts the presence of a germ-line BRCA2 mutation and confirms that stomach cancer is part of the spectrum of BRCA2 mutations. It is expected that the penetrance of BRCA2 mutations for stomach cancer will vary from country to country, reflecting local environmental and lifestyle factors.

Optimization of experimental conditions for RNA-based sequencing of MLH1 and MSH2 genes

The most sensitive technique for the detection of germline mutations is exon by exon sequencing of the gene under investigation using genomic DNA as a template for analysis. This approach, however, has cost and sensitivity limitations that can, at least in part, be overcome by RNA‐based analysis. Germline mutations of MLH1 and MSH2 are the most frequent cause of the inherited susceptibility to colorectal and other epithelial cancers known as hereditary non‐polyposis colorectal cancer (HNPCC). We compared the analysis of the MLH1 and MSH2 genes using mRNA and genomic DNA as starting material from 21 HNPCC patients. All samples were investigated by RT‐PCR, sequencing of cDNA and simultaneous sequencing of genomic DNA. The cDNA was generated using specific primers complementary to the ends of MLH1 and MSH2 genes, respectively. Mutations in MLH1 and MSH2 were detected in 11 out of 21 unrelated patients. In 10 out of 11 cases, mutations were detected independently of the type of primers used for reverse transcription (RT). One novel missense mutation (K751R) in MLH1 was detected using this method. One nonsense mutation (E205X) in MSH2 was only detectable when RT was performed using MSH2 gene‐specific primers. Shorter PCR products indicative of alternatively spliced transcripts were not observed when MLH1 or MSH2 specific cDNA RT primers were employed to generate template, except in one case where exon skipping was observed for exons 9 and 10. In this report we demonstrate that primers specific for RT of MLH1 and MSH2 are crucial for increasing the sensitivity of cDNA analysis. DNA sequencing using RNA as a basis for template construction may be a valuable and economical alternative to genomic DNA sequencing. Hum Mutat 17:52–60, 2001.

Ovarian cancer of endometrioid type as part of the MSH6 gene mutation phenotype

AbstractThe MSH6 gene is one of the DNA mismatch repair genes involved in development of inherited cancers, predominantly of the colorectum and endometrium. Herein we describe the first Polish MSH6 family and the pathological and clinical data about the ovarian cancer diagnosed in the proband. Our results and reports by others indicate that, besides colorectal and endometrial cancer, the late-onset endometrioid type of ovarian cancer can be a feature of families with MSH6 germline mutations.

Association of zinc level and polymorphism in MMP-7 gene with prostate cancer in Polish population

Introduction Prostate cancer is one of the most commonly diagnosed malignancies among men in Western populations. Evidence reported in the literature suggests that zinc may be related to prostate cancer. In this study we evaluated the association of serum zinc levels and polymorphisms in genes encoding zinc-dependent proteins with prostate cancer in Poland. Methods The study group consisted of 197 men affected with prostate cancer and 197 healthy men. Serum zinc levels were measured and 5 single nucleotide polymorphisms in MMP-1, MMP-2, MMP-7, MMP-13, MT2A genes were genotyped. Results The mean serum zinc level was higher in prostate cancer patients than in healthy controls (898.9±12.01 μg/l vs. 856.6±13.05 μg/l, p<0.01). When compared in quartiles a significant association of higher zinc concentration with the incidence of prostate cancer was observed. The highest OR (OR = 4.41, 95%CI 2.07–9.37, p<0.01) was observed in 3rd quartile (>853.0–973.9 μg/l). Among five analyzed genetic variants, rs11568818 in MMP-7 appeared to be correlated with 2-fold increased prostate cancer risk (OR = 2.39, 95% CI = 1.19–4.82, p = 0.015). Conclusion Our results suggest a significant correlation of higher serum zinc levels with the diagnosis of prostate cancer. The polymorphism rs11568818 in MMP-7 gene was also associated with an increased prostate cancer risk in Poland.

CHAPTER 22:Selenium and Cancer

Selenium is a trace element that is an essential component of many enzymes that play an important role in several major metabolic pathways and ameliorate environmental insult, including the antioxidant defense system, the immune system and functioning of the thyroid gland. There is a range of serum selenium levels associated, with the lowest rate of all causing mortality – the levels should be maintained at an optimal level and be neither too low nor too high. Selenium intake varies, largely based on the selenium content of food. The mean level of selenium in the population varies considerably between countries. Thus, for some countries selenium supplementation should be considered, whereas for others it could be contraindicated. Recent meta-analyses indicate unequivocally that selenium supplementation of people with low initial serum selenium levels decreases the incidence of cancer incidence by ∼35% and of cancer mortality by almost 50%. Additionally, it appears that in Se-deficient countries selenium levels may be a useful marker to select patients for cancer surveillance using for example computerized tomography for detection of the earliest stages of bronchial malignancy and colonoscopy for detection of the early stage colorectal cancer.