Genetic polymorphism of N-acetyltransferase-2, glutathione S-transferase-M1, and cytochromes P450IIE1 and P450IID6 in the susceptibility to head and neck cancer

AIMS

To analyse the allele frequencies of DNA polymorphisms at the genes for cytochromes P450IIE1 and P450IID6, N-acetyltransferase-2, and glutathione S-transferase-M1 in patients with head and neck squamous cell carcinoma, in an attempt to define genetic factors involved in the susceptibility to this cancer, which is strongly associated with tobacco consumption.

METHODS

Determination of restriction fragment length polymorphism (RFLP) at cytochromes P450IIE1/P450IID6 and NAT2 genes, and the presence of homozygous deletion of the GSTM1 gene, in 200 controls and 75 head and neck cancer patients. Allelic frequencies between the two groups were compared using a chi 2 test, and odds ratio with 95% confidence intervals were calculated.

RESULTS

There was no evidence of an association between alleles of CYP2D6 and CYP2E1 and head and neck cancer in our population. Similarly, frequencies of individuals lacking the GSTM1 gene did not differ between controls and patients. However, individuals with the NAT2-SA phenotype were at higher risk of developing head and neck cancer. The frequencies of the most common SA genotype (homozygous for the NAT2*5 allele) were higher in patients than in controls (27% v 15%, respectively). Slow acetylators homozygous for the NAT2*6 allele, the second most common SA allele, were also more common in patients than in controls (11% v 5%, respectively).

CONCLUSIONS

Slow NAT2 activity is a risk factor possibly leading to the development of head and neck cancer in response to tobacco carcinogens.

Factor V Leiden (R506Q) and risk of venous thromboembolism: a case-control study based on the Spanish population

Resistance to activated protein C (APC) is a frequent cause of thrombophilia. Most patients showing APC-resistance have a G to A mutation at codon 506 of the factor V that converts arginine to glutamine. This mutation is present in populations worldwide with frequencies ranging from 0.01 to 0.05. Genotyping of 150 control individuals from the Spanish population showed that 3.33% of them carried the mutation. Several studies have measured resistance to APC (following a classical functional assay) and have determined the factor V genotype in a number of thrombophilic patients, in an attempt to compare the predictive value of both laboratory methods. To assess the incidence of the factor V mutation among Spanish thrombophilic patients, we genotyped 51 of these. The frequency of mutation carriers rose from 3.33% in the controls to 53% in the patients. We found significant differences for the thrombosis-free survival curves and for the age at the first thrombotic event between patients who carried or did not carry the mutation. Analysis of relatives of 16 patients who carried the factor V mutation suggests the existence of additional genes that modulate the effect of the factor V gene in the development of venous thrombosis among carriers of the G to A mutation.

A family with a milder form of adult dominant polycystic kidney disease not linked to the PKD1 (16p) or PKD2 (4q) genes

Autosomal dominant polycystic kidney disease (ADPKD) is a genetically heterogeneous disease. Most families show positive linkage to polymorphic markers around the PKD1 (16p13.3) or PKD2 (4q21-23) loci. The PKD1 and PKD2 genes have been cloned and mutations defined in a number of patients. Several clinical studies have described a milder phenotype for PKD2 patients. More recently, evidence for a third genetic locus has been found in one Portuguese, one French-Canadian, and one Italian family. We identified a Spanish family with negative linkage to the PKD1 and the PKD2 loci. This family showed a very mild clinical phenotype compared to the other forms of ADPKD, including the non-PKD1/non-PKD2 families previously described.

Deletion and methylation of the tumour suppressor gene p16/CDKN2 in primary head and neck squamous cell carcinoma

AIMS

To study the homozygous deletion and methylation status of the 5' CpG island of the p16 and p15 genes (9p21) in a set of primary advanced head and neck squamous cell carcinomas (SCC) and to test whether inactivation of these genes by these mechanisms contributes to head and neck SCC development.

METHODS

DNA was extracted from fresh tumours. Homozygous deletion was determined by the polymerase chain reaction (PCR) followed by hybridisation with the corresponding probe, radioactively labelled by the random priming method. Methylation status of the CpG island of the 5' region of these genes was assessed by digestion with the appropriate restriction enzymes followed by PCR and subsequent hybridisation with the corresponding probe. The presence of point mutations was determined by PCR-SSCP (single strand conformation polymorphism).

RESULTS

The p16 and p15 genes were homozygously deleted in 20% and 10% of the tumours, respectively. No point mutations were found at p16 and p15. The 5' CpG island at the p16 gene was methylated in 20% of the cases.

CONCLUSIONS

The tumour suppressor gene p16 is inactivated through homozygous deletion or methylation in a significant proportion of cases of head and neck SCC.

Mutation analysis of the p53, APC, and p16 genes in the Barrett's oesophagus, dysplasia, and adenocarcinoma

AIMS

To study the loss of heterozygosity and the presence of mutations at the p53, p16/CDKN2, and APC genes in Barrett's oesophagus, low grade dysplastic oesophageal epithelium, and adenocarcinoma of the oesophagus; to relate the presence of alterations at these genes with the progression from Barrett's oesophagus to adenocarcinoma.

METHODS

DNA was extracted from paraffin blocks containing tissue from Barrett's oesophagus (12 samples), low grade dysplasia (15 cases), and adenocarcinoma (14 cases). Loss of heterozygosity (LOH) at the p53, p16, and APC genes was determined by comparing the autoradiographic patterns of several microsatellite markers between the normal tissue and the malignant tissue counterpart. SSCP was used to determine the presence of mutations at p53 (exons 5 to 8), p16 (exon 2), and APC. Homozygous deletion of the p16 gene was defined through polymerase chain reaction followed by Southern blot.

RESULTS

LOH at the p53, p16, and APC genes was not observed in Barrett's oesophagus without dysplasia, and increased to 90% (p53), 89% (p16), and 60% (APC) in the adenocarcinomas. The p53 gene was mutated in only two adenocarcinomas (codons 175 and 245). In one case a mutation at the APC gene (codon 1297) was found. No patient had mutation at the second exon of p16. However, this gene was homozygously deleted in three of the 12 adenocarcinomas.

CONCLUSIONS

The tumour suppressor genes p53, p16, and APC are often deleted in adenocarcinomas derived from Barrett's oesophagus. Mutations at these genes are also found in the adenocarcinomas, including the homozygous deletion of the p16 gene. However, the absence of genetic alterations in the Barrett's oesophagus and the low grade dysplastic epithelia suggest that mutations at these genes develop later in the progression from Barrett's oesophagus to adenocarcinoma.

Loss of heterozygosity and mutation analysis of the p16 (9p21) and p53 (17p13) genes in squamous cell carcinoma of the head and neck

We analyzed allelic loss at the p53 gene (17p13) and at chromosome region 9p21 in 35 primary head and neck squamous cell carcinomas. Loss of heterozygosity (LOH) at p53 and 9p21 was found in 50 and 75% of informative cases, respectively. LOH at the p53 gene did not increase significantly with tumor stage, but was more frequent in moderately and poorly differentiated tumors than in well-differentiated tumors. LOH plus mutation or homozygous deletion of p53 was limited to advanced stage and poorly differentiated tumors. Allelic loss at 9p21 is frequent in early stage head and neck squamous cell carcinoma and is not significantly associated with LOH at p53. The second exon of the p16/MTS1/CDKN2 gene was found to be homozygously deleted in 1 of 19 cases showing LOH at 9p21, but direct sequencing did not show mutations in the remaining 18 cases. This suggests that p16 plays a limited role in the development of head and neck squamous cell carcinoma.

PCR-based study of the presence of Y-chromosome sequences in patients with Ullrich-Turner syndrome

The presence of Y chromosome sequences in Ullrich-Turner syndrome (UTS) patients has been suggested in previous work. Karyotype analysis estimated at about 60% of patients with a 45, X constitution and molecular analysis (Southern blot analysis with several Y chromosome probes and PCR of specific sequences) identified the presence of Y chromosome material in about 40% of 45, X patients. We have developed a very sensitive, PCR-based method to detect Y specific sequences in DNA from UTS patients. This protocol permits the detection of a single cell carrying a Y sequence among 10(5) Y-negative cells. We studied 18 UTS patients with 4 Y-specific sequences. In 11 patients we detected a positive amplification for at least one Y sequence. The existence of a simple and sensitive method for the detection of Y sequences has important implications for UTS patients, in view of the risk for some of the females carrying Y-chromosome material of developing gonadoblastoma and virilization. Additionally, some of the UTS associated phenotypes, such as renal anomalies, could be correlated with the presence of Y chromosome specific sequences.

DNA microsatellite analysis of families with autosomal dominant polycystic kidney disease types 1 and 2: evaluation of clinical heterogeneity between both forms of the disease

We studied 17 large families affected by adult dominant polycystic kidney disease (ADPKD). Ultrasonographic analysis was performed on all the family members. DNA microsatellite markers closely linked to PKD1 on 16p13.3 were analysed, and linkage of the disease to this locus was determined. Families showing a negative linkage value were evaluated for linkage to the PKD2 locus on 4q. Five of the 17 families showed negative linkage for the 16p13.3 markers. In these families significant linkage to 4q was obtained. Renal cysts developed at an earlier age in PKD1 mutation carriers, and end stage renal failure occurred at an older age in people affected with PKD2. Analysis of large families with ADPKD in a Spanish population indicates that this is a genetically heterogeneous disorder, but mutations at only two loci are responsible for the development of the disease in most if not all the families. Clinicopathological differences between both forms of the disease occur, with subjects with ADPKD2 having a better prognosis than those with mutations at PKD1.

[Cystic fibrosis in Asturias: an elevated frequency of the delta F508 mutation]

BACKGROUND

Cystic fibrosis (CF) is the most common autosomic-recessive inherited disorder. More than 300 different mutations in the CF gene (CFTR) have been described, being delta F508 and G542X the most common in the Spanish population. The frequencies of these mutations vary between the different European populations.

METHODS

We have studied the delta F508 and G542X mutations in 20 CF-patients from Asturias. These mutations were analysed through the polymerase chain reaction (PCR).

RESULTS

The frequency of the delta F508 mutation in Asturias was 77.5%, higher than those found in most of the other Spanish populations. The frequency found in Asturias is close to the frequency described for the Basque Country population. Patients homozygous for the delta F508 mutation showed clinical symptoms similar to those described in studies on other populations.

CONCLUSIONS

The high frequency of two mutations in the CFTR gene in Asturias makes possible the direct diagnostic in most families. The delta F508 mutation is associated to severe clinical manifestations, like early pancreatic insufficiency and Pseudomonas infection.

Gastric Castleman's disease with a lupus-like circulating anticoagulant

We report the case of a 13-yr-old patient with retarded growth and a 2-yr background of asthenia, anorexia, and fever, whose laboratory data revealed anemia, thrombocytosis, an elevated erythrocyte sedimentation rate, ferropenia, hyperglobulinemia, hyperfibrinogenemia, and presence of a lupus-like circulating anticoagulant. Clinical studies revealed a tumor-like overgrowth in the gastric wall, and surgery confirmed its subserosal localization in the gastric fundus. After total removal of the mass, the systemic manifestations disappeared. The pathological study revealed the existence of the hyaline-vascular variety of Castleman's disease. Having reviewed the medical literature, we have not found a single unquestionable case of gastric Castleman's disease, although three other cases have been described as gastric pseudolymphoma which, when analyzed, could correspond to typical cases of Castleman's disease. Likewise, this is the second case associated with a circulating anticoagulant of lupoid characteristics. We conclude that Castleman's disease should be included in the differential diagnosis of gastric lesions of lymphoid nature and in the series of processes associated with lupus anticoagulant.