Flavio Lejbkowicz

Genetically Determined Heterogeneity in Hemoglobin Scavenging and Susceptibility to Diabetic Cardiovascular Disease

Abstract —A major function of haptoglobin (Hp) is to bind hemoglobin (Hb) to form a stable Hp‐Hb complex and thereby prevent Hb‐induced oxidative tissue damage. Clearance of the Hp‐Hb complex can be mediated by the monocyte/macrophage scavenger receptor CD163. We recently demonstrated that diabetic individuals homozygous for the Hp 2 allele (Hp 2–2) were at 500% greater risk of cardiovascular disease (CVD) compared with diabetic individuals homozygous for the Hp 1 allele (Hp 1–1). No differences in risk by Hp type were seen in individuals without diabetes. To understand the relationship between the Hp polymorphism and diabetic CVD, we sought to identify differences in antioxidant and scavenging functions between the Hp types and to determine how these functions were modified in diabetes. The scavenging function of Hp was assessed using rhodamine‐tagged and 125I‐Hp in cell lines stably transfected with CD163 and in macrophages expressing endogenous CD163. We found that the rate of clearance of Hp 1–1‐Hb by CD163 is markedly greater than that of Hp 2–2‐Hb. Diabetes is associated with an increase in the nonenzymatic glycosylation of serum proteins, including Hb. The antioxidant function of Hp was assessed with glycosylated and nonglycosylated Hb. We identified a severe impairment in the ability of Hp to prevent oxidation mediated by glycosylated Hb. We propose that the specific interaction between diabetes, CVD, and Hp genotype is the result of the heightened urgency of rapidly clearing glycosylated Hb‐Hp complexes from the subendothelial space before they can oxidatively modify low‐density lipoprotein to atherogenic oxidized low‐density lipoprotein. (Circ Res. 2003;92:1193–1200.)

Genetic variation in 8q24 associated with risk of colorectal cancer

Chromosome 8q24 harbors oncogenes known to be involved in pathogenesis of colorectal cancer (CRC) as well as uncharacterized genetic variants that have recently been shown to influence inherited risk of prostate cancer. In a population-based case-control study of colorectal cancer in northern Israel, we investigated the association between variation in 8q24 and risk of CRC. Among 1,861 incident cases and 1,937 population-based controls matched on age, gender, ethnicity, and clinic, rs10505477 was associated with risk of CRC in a dominant model, with an odds ratio = 1.23, 95% confidence interval = 1.05 -1.43, (p=0.008). This association was independently validated in an analysis of cancer among relatives of carriers of the risk allele, with a hazard ratio of 3.2 (95% bootstrap CI = 1.16 – 17.8). Genetic variation at rs10505477 on 8q24 potentially accounts for 14% of CRC in this population and should be replicated in other studies.

Clinical implications of UGT1A1*28 genotype testing in colorectal cancer patients

Metastatic colorectal cancer is frequently treated with irinotecan, a topoisomerase‐I inhibitor. The UGT1A1 gene encodes for an enzyme that metabolizes irinotecan, and its genetic variants were shown to be associated with increased drug toxicity. We evaluated clinical outcomes associated with the UGT1A1*28 variant.

FGFR2 Is a Breast Cancer Susceptibility Gene in Jewish and Arab Israeli Populations

Genetic variation in FGFR2 is a newly described risk factor for breast cancer. We estimated the relative risk and contribution of FGFR2 polymorphisms to breast cancer risk in diverse ethnic groups within Jewish and other Middle Eastern populations. We genotyped four FGFR2 single nucleotide polymorphisms (SNP) and tested for association of these SNPs and haplotypes with breast cancer risk in a population-based case-control study of 1,529 women with breast cancer and 1,528 controls. We found significant associations between breast cancer risk and all four studied SNPs in FGFR2 (Ptrend for all SNPs < 0.0001). In ethnicity-specific analysis, all four SNPs were significantly associated with breast cancer risk in Ashkenazi and Sephardi Jews, with a similar but not significant trend in Arabs. Haplotype analysis identified five common haplotypes (>1%). The previously described AAGT risk haplotype was significantly associated with breast cancer risk in Ashkenazi [odds ratio (OR), 1.25; 95% confidence interval (95% CI), 1.07-1.45; P = 0.0059] and Sephardi Jews (OR, 1.46; 95% CI, 1.17-1.80; P = 0.0006) compared with the reference GGAC haplotype. The AAAC haplotype was significantly associated with breast cancer risk in Sephardi Jews (OR, 1.97; 95% CI, 1.16-3.35; P = 0.0125) but not in Ashkenazi Jews (OR, 0.83; 95% CI, 0.41-1.62; P = 0.5613) or in Arabs (OR, 1.31; 95% CI, 0.80-2.14; P = 0.2881). Genetic variation in FGFR2, identified by rs1219648, may account for a substantial fraction of breast cancer in Arab (12%), Ashkenazi (15%), and Sephardi Jewish (22%) populations. The identification of population-specific risk haplotypes in FGFR2 is likely to help identify causal variants for breast cancer. (Cancer Epidemiol Biomarkers Prev 2008;17(5):1060–5)

Gene Expression Differences between Colon and Rectum Tumors

Purpose: Colorectal cancer studies typically include both colon and rectum tumors as a common entity, though this assumption is controversial and only minor differences have been reported at the molecular and epidemiologic level. We conducted a molecular study based on gene expression data of tumors from colon and rectum to assess the degree of similarity between these cancer sites at transcriptomic level. Experimental Design: A pooled analysis of 460 colon tumors and 100 rectum tumors from four data sets belonging to three independent studies was conducted. Microsatellite instable tumors were excluded as these are known to have a different expression profile and have a preferential proximal colon location. Expression differences were assessed with linear models, and significant genes were identified using adjustment for multiple comparisons. Results: Minor differences at a gene expression level were found between tumors arising in the proximal colon, distal colon, or rectum. Only several HOX genes were found to be associated with tumor location. More differences were found between proximal and distal colon than between distal colon and rectum. Conclusions: Microsatellite stable colorectal cancers do not show major transcriptomic differences for tumors arising in the colon or rectum. The small but consistent differences observed are largely driven by the HOX genes. These results may have important implications in the design and interpretation of studies in colorectal cancer. Clin Cancer Res; 17(23); 7303–12. ©2011 AACR.

Genome-wide association study of colorectal cancer identifies six new susceptibility loci

Genetic susceptibility to colorectal cancer is caused by rare pathogenic mutations and common genetic variants that contribute to familial risk. Here we report the results of a two-stage association study with 18,299 cases of colorectal cancer and 19,656 controls, with follow-up of the most statistically significant genetic loci in 4,725 cases and 9,969 controls from two Asian consortia. We describe six new susceptibility loci reaching a genome-wide threshold of P<5.0E-08. These findings provide additional insight into the underlying biological mechanisms of colorectal cancer and demonstrate the scientific value of large consortia-based genetic epidemiology studies.

MutYH mutation carriers have increased breast cancer risk

Variants of the mutY homolog gene MutYH, a DNA repair gene, are associated with increased risk of colorectal cancer; however, it remains unclear whether these variants also are associated with the risk of other cancers. The authors studied the risk of breast cancer associated with MutYH variants in a unique ethnic group of Sephardi Jews in Israel with a high prevalence of MutYH mutations.

Double heterozygosity in the BRCA1 and BRCA2 genes in the Jewish population

BACKGROUND The frequency and characteristics of disease in individuals who concomitantly harbor pathogenic mutations in both BRCA1 and BRCA2 genes are not established. MATERIALS AND METHODS Data were collected from the database of Clalit Health Services National Familial Cancer Consultation Service. Probands referred to this clinical service and their family members are routinely tested for the three Jewish founder mutations (BRCA1: 185delAG, 5382insC, BRCA2: 6174delT). In addition, carriers identified in a population-based cohort of all cases diagnosed with breast cancer in Israel in 1987-1988 allowed the estimation of the population frequency of this phenomenon. RESULTS In the clinic-based series of 1191 carriers of mutations in BRCA1 or BRCA2 belonging to 567 families, 22 males and females (1.85%) from 17 different families (3.0%) were found to harbor two different mutations. These included 18 individuals (1.51%) who concomitantly carried the 185delAG BRCA1 and the 6174delT BRCA2 mutations and four individuals (0.34%) who carried the 5382insC BRCA1 and the 6174delT mutations. All individuals were heterozygote carriers and none had a double mutation of both founder mutations in the BRCA1 gene itself. Seven of the 16 double carrier women (46.7%) had a personal history of breast carcinoma, diagnosed at a mean age of 44.6, compared with 372/926 (40.2%) carriers of a single mutation diagnosed with a mean age at diagnosis of 48.1 [odds ratio (OR)=1.3, 95% confidence interval (CI) 0.4-4.0]. One case (6.7%) had a personal history of ovarian carcinoma diagnosed at the age of 53 compared with 55/926 (5.9%) of the women with single mutation (OR=1.1, CI=0.2-7.6). The frequency of double mutations in the population-based national breast cancer cohort was 2.2% of all carriers, and 0.3% of all breast cancer cases in the Ashkenazi population in the cohort. The mean age at diagnosis of breast cancer was younger in the carriers of two mutations. CONCLUSION Double carriers of mutations in the BRCA genes are rare and seem to be carrying a similar probability of developing breast and ovarian cancers as carriers of single mutations.

Blood BDNF Level Is Gender Specific in Severe Depression

Though the role of brain derived neurotrophic factor (BDNF) as a marker for major depressive disorder (MDD) and antidepressant efficacy has been widely studied, the role of BDNF in distinct groups of patients remains unclear. We evaluated the diagnostic value of BDNF as a marker of disease severity measured by HAM-D scores and antidepressants efficacy among MDD patients. Fifty-one patients who met DSM-IV criteria for MDD and were prescribed antidepressants and 38 controls participated in this study. BDNF in serum was measured at baseline, 1st, 2nd and 8th treatment weeks. Depression severity was evaluated using the Hamilton Rating Scale for Depression (HAM-D). BDNF polymorphism rs6265 (val66met) was genotyped. We found a positive correlation between blood BDNF levels and severity of depression only among untreated women with severe MDD (HAM-D>24). Serum BDNF levels were lower in untreated MDD patients compared to control group. Antidepressants increased serum BDNF levels and reduced between-group differences after two weeks of treatment. No correlations were observed between BDNF polymorphism, depression severity, duration of illness, age and BDNF serum levels. Further supporting the role of BDNF in the pathology and treatment of MDD, we suggest that it should not be used as a universal biomarker for diagnosis of MDD in the general population. However, it has diagnostic value for the assessment of disease progression and treatment efficacy in individual patients.

Genetic polymorphisms in fatty acid metabolism genes and colorectal cancer

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. Epidemiological risk factors for CRC included dietary fat intake; consequently, the role of genes in the fatty acid biosynthesis and metabolism pathways is of particular interest. Moreover, hyperlipidaemia has been associated with different type of cancer and serum lipid levels could be affected by genetic factors, including polymorphisms in the lipid metabolism pathway. The aim of this study is to assess the association between single-nucleotide polymorphisms (SNPs) in fatty acid metabolism genes, serum lipid levels, body mass index (BMI) and dietary fat intake and CRC risk; 30 SNPs from 8 candidate genes included in fatty acid biosynthesis and metabolism pathways were genotyped in 1780 CRC cases and 1864 matched controls from the Molecular Epidemiology of Colorectal Cancer study. Information on clinicopathological characteristics, lifestyle and dietary habits were also obtained. Logistic regression and association analysis were conducted. Several LIPC (lipase, hepatic) polymorphisms were found to be associated with CRC risk, although no particular haplotype was related to CRC. The SNP rs12299484 showed an association with CRC risk after Bonferroni correction. We replicate the association between the T allele of the LIPC SNP rs1800588 and higher serum high-density lipoprotein levels. Weak associations between selected polymorphism in the LIPC and PPARG genes and BMI were observed. A path analysis based on structural equation modelling showed a direct effect of LIPC gene polymorphisms on colorectal carcinogenesis as well as an indirect effect mediated through serum lipid levels. Genetic polymorphisms in the hepatic lipase gene have a potential role in colorectal carcinogenesis, perhaps though the regulation of serum lipid levels.