Association of kidney transplant failure and antibodies against MICA

Despite the progress in renal transplantation, acute rejection and graft failure still occur and chronic rejection continues to be the main problem in long-term allograft survival. Although kidney transplant rejection has been linked to anti-HLA antibodies, not all patients with failed kidney transplants have anti-HLA antibodies, indicating that other loci may be involved. Sera of 63 patients who experienced kidney rejection were compared against sera of 82 patients with functioning transplants. Sera were examined for IgG and IgM anti-HLA Class I and II antibodies. They were also tested by cytotoxicity against panels of 26 endothelial cell lines, 8 MHC class I chain-related gene A (MICA) recombinant cell lines, and 28 B lymphoblast cell lines. Among patients whose transplants failed, 65% had anti-HLA antibodies compared with 45% of those with functioning kidneys (p < 0.05). Similarly, among those whose transplants failed, 41% had anti-endothelial cell antibodies in contrast to 22% in functioning patients (p < 0.05). Among patients whose grafts failed, 52% had anti-MICA antibodies versus 21% of those with functioning grafts (p < 0.001). Eleven patients with failed grafts and 32 with functioning grafts were negative for all of the above. However, 6 of the former and 7 of the latter showed positive cytotoxicity against B lymphoblasts (p < 0.05). Taking all antibodies together, 92% of patients with graft failure had antibodies as opposed to 70% of patients with functioning grafts (p < 0.001). We postulate that antibodies against HLA, MICA, endothelial cells, and B lymphoblasts could be independently involved in the slow process of chronic graft failure.     

Prevalance of BRCA1 and BRCA2 mutations in familial breast cancer patients in Lebanon

Breast cancer is the most prevalent malignancy in women in Western countries, currently accounting for one third of all female cancers. Familial aggregation is thought to account for 5–10 % of all BC cases, and germline mutations in BRCA1 and BRCA2 account for less of the half of these inherited cases. In Lebanon, breast cancer represents the principal death-causing malignancy among women, with 50 % of the cases diagnosed before the age of 50 years.In order to study BRCA1/2 mutation spectra in the Lebanese population, 72 unrelated patients with a reported family history of breast and/or ovarian cancers or with an early onset breast cancer were tested. Fluorescent direct sequencing of the entire coding region and intronic sequences flanking each exon was performed.A total of 38 BRCA1 and 40 BRCA2 sequence variants were found. Seventeen of them were novel. Seven confirmed deleterious mutations were identified in 9 subjects providing a frequency of mutations of 12.5 %. Fifteen variants were considered of unknown clinical significance according to BIC and UMD-BRCA1/BRCA2 databases.In conclusion, this study represents the first evaluation of the deleterious and unclassified genetic variants in the BRCA1/2 genes found in a Lebanese population with a relatively high risk of breast cancer.     

Major oncogenes and tumor suppressor genes involved in epithelial ovarian cancer (review)

Ovarian cancer remains the leading cause of death from gynecologic malignancy in Western countries. This cancer results from a succession of genetic alterations involving oncogenes and tumor suppressor genes which have a critical role in normal cell growth regulation. Mutations and/or overexpression of three oncogenes, HER-2/neu, c-myc and K-ras, and of the tumor suppressor gene p53, have frequently been observed in sporadic ovarian cancer. In the context of high risk families, the most frequently involved genes are BRCA1 and BRCA2. We review the function of these different proteins, the incidence of mutations in their genes in carcinogenesis and as potential prognostic factors in sporadic and hereditary ovarian cancer.     

Breast cancer risk in BRCA1 and BRCA2 mutation carriers and polyglutamine repeat length in the AIB1 gene

Marked variation in phenotypic expression among BRCA1 and BRCA2 mutation carriers may be partly explained by modifier genes that influence mutation penetrance. Variation in CAG/CAA repeat lengths coding for stretches of glutamines in the C-terminus of the AIB1 protein (amplified in breast cancer 1, a steroid receptor coactivator) has been proposed to modify the breast cancer risk in women carrying germline BRCA1 mutations. We genotyped the AIB1 repeat length polymorphism from the genomic DNA of a group of 851 BRCA1 and 324 BRCA2 female germline mutation carriers to estimate an association with breast cancer risk modification. Hazard ratios (HR) were calculated using a Cox proportional hazards model. For BRCA1 and BRCA2 mutation carriers, analyzed separately and together, we found that women who carried alleles with 28 or more polyglutamine repeats had no increased risk of breast cancer compared to those who carried alleles with fewer repeats (HR for BRCA1/2 carriers = 0.88, 95% CI [confidence interval] = 0.75-1.04). Analyzing average repeat lengths as a continuous variable showed no excess risk of breast cancer (BC) in BRCA1 or BRCA2 mutation carriers (HR for average repeat length in BRCA1/2 carriers = 1.01, 95% CI = 0.92-1.11). These results strongly suggest that contrary to previous studies, there is no significant effect of AIB1 genetic variation on BC risk in BRCA1 mutation carriers and provide an indication that there is also no strong risk modification in BRCA2 carriers.     

GSTM1, smoking and lung cancer: a case-control study

BACKGROUND: We conducted a case-control study to examine the risk of lung cancer in relation to GSTM1 polymorphism and cigarette smoking (primarily of black tobacco) in a French population. METHODS: The 611 subjects were 301 incident lung cancer cases and 310 hospital controls. We were able to constitute a DNA bank for 547 subjects (89.5%) and gather detailed information on smoking history for all of them. Results presented here concern 247 cases and 254 controls. RESULTS: Taking non- or light smokers as the reference category, we estimated odds ratios (OR) of 4.2 (95% CI: 2.6-6.7) and 5.2 (95% CI: 3.3-8.3) for the medium and heavy smokers respectively. On the other hand we estimated that the crude OR associating GSTM1 with lung cancer was 1.3 (95% CI: 0.9-1.8). Furthermore our data do not depart significantly from a multiplicative model of the combined effects of smoking and GSTM1 deficiency. CONCLUSIONS: We conclude that smoking and the GSTM1 gene are each a risk factor for lung cancer, and that their combined effect does not differ significantly from that of a multiplicative model.     

Loss of heterozygosity at the ATM locus in colorectal carcinoma

Patients homozygous for mutation of the ATM gene exhibit constitutional genetic instability and have a high risk of cancer. A-T heterozygotes also have an increased tendency to develop adenocarcinomas. Colorectal cancer (CRC) is the second most common cancer in western populations, and tumors of the right colon are typically highly genetically unstable. The DNA mismatch repair genes mutated in most familial and some sporadic CRCs account for one route by which cells acquire additional oncogenic mutations during the progression of malignancy. Mismatch repair defects, however, do not seem to account for the majority of CRCs. Because of its role in maintaining genomic stability, and the high risk of cancer to homozygotes, ATM is a candidate gene for inactivation in the evolution of chromosomal instability in tumor cells. We have examined 114 CRC patients for loss of heterozygosity (LOH) using six microsatellite markers tightly linked to the ATM locus. Our data suggest that LOH of this region is not associated with cancer of the proximal colon. In the distal colon, LOH was found in 23-31% of cases, which is moderately elevated above the non-specific LOH reported in tumors of this tissue. No correlations were found with regard to clinicopathological variables aside from tumor location.     

The hereditary pancreatitis gene maps to long arm of chromosome 7

Hereditary pancreatitis (HP) is an autosomal dominant disorder with incomplete penetrance characterized by recurring episodes of severe abdominal pain often presenting in childhood. Although this disorder has only been recently described, about 100 families have been documented worldwide. The pathophysiology of this disorder is unknown. Here, a large French family of 147 individuals (47 of whom were affected) from a four-generation kindred with HP has been examined and a genome segregation analysis of highly informative microsatellite markers has been performed. Linkage has been found between HP and six chromosome 7q markers. Maximal two point lod scores between HP and D7S 640, D7S 495, D7S 684, D7S 661, D7S 676 and D7S 688 were 4.00 (theta = 0.143), 5.85 (theta = 0.143), 4.91 (theta = 0.156), 8.58 (theta = 0.077), 8.28 (theta = 0.060), 4.40 (theta = 0.169), respectively. Multipoint linkage data combined with recombinant haplotype analysis indicated that the most likely order is: D7S 640-D7S 495-D7S 684-D7S 661-D7S 676-D7S 688, with the HP gene situated in the underlined region. As in all families reported in the literature, the clinical presentation of the disease is identical to the presentation of sporadic cases, one could expect that the knowledge of the HP gene could be a clue to pancreatitis in general. Based on its map position, this is the first step towards the positional cloning of the Hereditary Pancreatitis Gene (HPG).      

The 1396del A mutation and a missense mutation or a rare polymorphism of the WRN gene detected in a French Werner family with a severe phenotype and a case of an unusual vulvar cancer. Mutations in brief no. 136. Online

The Werner's syndrome (WS) is a rare recessive disease characterized by an early onset of geriatric disorders. The Werner's syndrome gene (WRN) recently cloned, encodes for an helicase and therefore plays a role in DNA metabolism and DNA repair. Here, we report the study of a French family with two affected members and numerous cancers. Using the protein truncation test and sequencing, we identified a homozygous mutation in the WRN gene. This mutation generates a frame shift leading to a very short 391 amino acids truncated protein without the helicase motif. A particularly severe phenotype of the affected patient was associated with an unusual vulvar cancer traditionaly observed in elderly patients and therefore likely to be related to the Werner's syndrome. An additional substitution of G for A at nucleotidic position 1392 was also described. We suggest that a relation between genotype and phenotype could exist in the studied family.     

Genetic diversity of KIR natural killer cell markers in populations from France, Guadeloupe, Finland, Senegal and Réunion

Killer cell immunoglobulin-like receptors (KIRs) belong to a diverse family of natural killer (NK) cell receptors recognizing human leukocyte antigen (HLA) class I molecules. Due to this functional link, KIR molecules are expected to display a high polymorphism, such as their HLA ligands. Moreover, many studies conducted in mouse and human models have shown that NK-KIR receptors play an important role in haematopoietic stem cell transplantation (HSCT). A beneficial impact of peculiar KIR ligand (HLA) mismatching has been reported suggesting a role to this combinatory HLA-KIR polymorphism. It is thus important to investigate KIR diversity in various human populations. To this end, we used polymerase chain reaction-sequence-specific primers to evaluate KIR gene in five selected populations (France, Guadeloupe, Senegal, Finland and Réunion). Genotypic and haplotypic frequencies were computed, as well as genetic distances and dendrogram (phylip package). These data illustrate the genetic relationship of these five populations through the KIR polymorphism. Results revealed a wide diversity in KIR gene frequencies in Guadeloupe and Réunion, and a high specificity in Senegal. The obtained dendrogram indicated small genetic distances between France, Guadeloupe and Réunion as well as between France and Finland. Senegal showed a distant genetic relationship with the other countries and, interestingly, an inverted ratio of coding/non-coding (KIR2DS4/1D) alleles compared with Caucasians. These data expose the broad diversity in KIR genes worldwide and show that KIR genes are pertinent tools in human population genetics. If the role of KIR donor-recipient incompatibilities is confirmed, KIR diversity according to ethnicity should be taken into account during the selection of HSCT donors.