Sequence analysis of the human kallikrein gene locus identifies a unique polymorphic minisatellite element.

Minisatellites are repetitive sequences of DNA that are present throughout the genome. Although the origin and function of these minisatellites is still unknown, they found clinical applications as markers of many diseases, including cancer. Also, they are useful tools for DNA fingerprinting and linkage analysis. Kallikreins are serine proteases that appear to be involved in many diseases including brain disorders and malignancy. We have recently characterized the human kallikrein gene locus on chromosome 19q13.4, which includes 15 kallikrein genes. In this study, we examined the kallikrein locus ( approximately 300 Kb) for all known repeat elements. About 50% of this genomic area is occupied by different repeat elements. We also identified unique minisatellite elements that are restricted to chromosome 19q13. Ten clusters of these minisatellites are distributed along the locus on either DNA strand. The clusters are located in the promoters and enhancers of genes, in introns, and in untranslated regions of the mRNA. Analysis of these elements indicates that they are polymorphic, thus they can be useful in linkage analysis and DNA fingerprinting. Our preliminary results indicate also that the distribution of the different alleles of these minisatellites might be associated with malignancy.

Codon 89 polymorphism in the human 5 alpha-reductase gene in primary breast cancer.

The enzyme human steroid 5-alpha reductase type II (SRD5A2) and androgen receptor (AR) are critical mediators of androgen action, suggesting a potential role in hormonally related cancers. The SRD5A2 gene harbours two frequent polymorphic sites, one in the coding region, at codon 89 of exon 1, where valine is substituted by leucine (V89L) and the other in the 3' untranslated region (3' UTR) where a variable number of dinucleotide TA repeat lengths exists. The V89L polymorphism is known to alter the activity of this enzyme. In the present study we examined 144 sporadic breast tumours from Italian patients for the V89L and TA polymorphisms by sequence and fragment analysis, respectively. Tumour extract prostate specific antigen (PSA) concentration as well as a number of well-established clinical and pathological parameters were evaluated. The results show that 53% of the tumours were homozygous for VV alleles, 37% were heterozygous for VL alleles and 10% were homozygous for LL alleles. TA(0) repeats were found in tumours with VV, LL and VL genotypes. TA(9) repeats were only found in VV homozygotes and were totally absent from either LL homozygotes or VL heterozygotes. PSA expression was significantly elevated in tumours with VV genotype. The presence of LL alleles in breast tumours is associated with earlier onset and shorter disease-free (RR = 2.65;P = 0.013) and overall survival (RR = 3.06;P = 0.014) rates. The VV genotype is associated with a more favourable prognosis. Our study suggests that the polymorphism in codon 89 of exon 1 of the human 5 alpha-reductase gene is related with TA repeat genotypes, PSA expression and breast cancer prognosis. More specifically, we found that the LL genotype is also associated with earlier onset and more aggressive forms of breast cancer. Long-term-outcome studies are needed to investigate the relevance of this polymorphism to breast cancer susceptibility.

Breast cancer prognostic significance of a single nucleotide polymorphism in the proximal androgen response element of the prostate specific antigen gene promoter.

Prostate Specific Antigen (PSA) expression by breast epithelial cells is associated with favorable breast cancer prognosis. In preliminary studies, we found that a nucleotide variation (G-->A) at position -158 in the androgen response element (ARE-1) of the PSA promoter was present in four out of 9 breast tumors examined and in a breast carcinoma cell line. We have now determined the nucleotide composition at position -158 of DNA extracted from 148 well-characterized breast tumors and compared tumor genotype with that of controls without cancer, with tumor PSA concentration and with clinicopathological variables, overall survival and disease free survival. The G-->A base change at position -158 is a polymorphism. Allelotypes were similarly distributed in breast cancer patients and controls. The Mann-Whitney U Test showed a significantly higher tumor PSA concentration in tumors that presented a homozygous G as opposed to homozygous A genotype. Genotype at position -158 was not associated with clinicopathological variables in contingency table analysis. Univariate Cox regression models showed a 28% reduction in risk for death in patients with homozygous G genotype compared to those with homozygous A genotype (P = 0.03). However, ARE-1 genotype did not significantly add to the prognostic power in the multivariate model of overall survival. In summary, the base change at position -158 is a polymorphism that may affect breast cancer prognosis, but further studies are required to confirm this possibility and to investigate the relevance of this polymorphism in terms of breast cancer susceptibility.

TA repeat polymorphism of the 5alpha-reductase gene and breast cancer.

There is increasing evidence that androgens play a significant role in the development and progression of breast cancer. 5alpha-Reductase (SRD5A2) is an enzyme that is expressed in androgen-dependent tissues, and it catalyzes the reduction of testosterone to its more bioactive form, dihydrotestosterone, which then transactivates a number of genes. One of these genes encodes for prostate-specific antigen (PSA), a favorable prognostic factor in breast cancer. The 3' untranslated region of the SRD5A2 gene contains either no TA repeats [(TA)0] or 9 [(TA)9] or 18 [(TA)18] repeats. Variations in the length of these dinucleotide repeats have been reported to influence the enzymatic activity of SRD5A2. In this study, we determined the TA genotypes in DNA from 141 well-characterized breast tumors and in DNA from whole blood of 70 women without cancer. The presence of TA genotypes was then associated with tumor cytosolic PSA concentrations and with clinicopathological variables, including disease-free survival and overall survival. Three genotypes, (TA)0 homozygote, (TA)0/(TA)9 heterozygote, and (TA)9 homozygote, were identified. No (TA)18 alleles were detected in any of the two patient groups. A statistically significant association between high PSA concentrations and (TA)0/(TA)9 or (TA)9 genotypes was observed (P = 0.004). (TA)0/(TA)9 or (TA)9 genotypes were found less frequently in patients at stage III or IV disease. TA genotypes were not associated with other clinicopathological variables by contingency table analysis. Patients with (TA)0/(TA)9 or (TA)9 repeats, when compared to those with genotypes homozygous for the (TA)0 allele, showed a significant reduction in the risk for relapse (P = 0.043). Long-term studies are needed to investigate the relevance of this polymorphism to breast cancer susceptibility.

Shorter CAG repeat length in the androgen receptor gene is associated with more aggressive forms of breast cancer.

The androgen receptor (AR) is a transcription factor mediating the action of androgens. The AR gene is localized on chromosome X and it contains a series of CAG trinucleotide repeats. The length of the CAG repeats varies among individuals and this polymorphism is believed to be related to AR transcriptional activity. Studies have shown that fewer CAG repeats are associated with an increased risk as well as more aggressive forms of prostate cancer. Although AR is expressed in breast cancer and the impact of androgen and AR on breast cancer has been recognized, the role of the CAG repeats in breast cancer remains unknown. In this study, we measured the CAG repeats in breast cancer tissue using a PCR-based method. Of the 133 patients with primary breast cancer, 102 were heterozygous and 31 were homozygous. The mean CAG repeat number for homozygous women was 21; for heterozygous women the repeat number mean was 20 for the short allele and 24 for the long allele. The length of CAG repeats either in one allele or in both alleles was inversely correlated with the histological grade of breast cancer (r = -0.23 or -0.26, respectively, p < 0.05). An association between positive lymph nodes and fewer CAG repeats in both alleles was also suggested (p = 0.06). Furthermore, survival analysis indicated that the total number of CAG repeats in both alleles was associated with patient overall survival. With every CAG repeat increase, there was a 6% reduction in the risk of death (RR = 0.94, p = 0.03). The association remained significant after controlling for the homozygous and heterozygous status (RR = 0.92, p = 0.01). The association became no longer significant when clinical and pathological variables were adjusted in the analysis but this could be due to the reduction of sample size in the multivariate analysis. CAG heterozygosity and difference in number of CAG repeats between the two alleles were not associated with either disease features or patient survival. Our results suggest that longer CAG repeats may occur more frequently in less aggressive cancer and that the CAG repeats may play a role in breast cancer progression.

p53 gene mutation, tumor p53 protein overexpression, and serum p53 autoantibody generation in patients with breast cancer.

OBJECTIVES: Autoantibodies against the p53 tumor suppressor protein have been detected in the serum of a proportion of patients with various cancers. The generation of such antibodies has been proposed to be due to either tumor p53 protein accumulation or to the type of p53 gene mutation. These hypotheses are examined in the present study. DESIGN AND METHODS: Using immunofluorometric assays, we studied 195 patients with primary breast cancer for the presence of p53 antibodies in serum and p53 protein accumulation in the corresponding tumor. Seventeen patients (9%) were p53 antibody-positive and 77 (40%) overexpressed p53. Ten of the 17 p53 antibody-positive patients had tumor p53 accumulation and 7 were negative for p53. Statistical analysis revealed a weak association between the presence of p53 antibodies and p53 protein accumulation (p = 0.05). Direct DNA sequencing of exons 1-11 of the p53 gene was performed for 16 p53 antibody-positive and 16 p53 antibody-negative patients. RESULTS: Five of the seropositive and eight of the seronegative patients had a p53 gene mutation. Four of the five mutations in the p53 antibody-positive patients affected a Tyr residue, whereas none of the gene abnormalities in the seronegative patients had such an effect. CONCLUSIONS: We conclude that p53 antibodies tend to develop in patients with tumor p53 accumulation, but p53 accumulation is neither sufficient nor necessary for the generation of the immune response. Further, p53 antibody-positive patients do not have higher frequency of p53 gene mutations than p53 antibody-negative patients, but the former patient group is associated with a Tyr substitution in the protein product.

Rapid and accurate determination of (CAG)n repeats in the androgen receptor gene using polymerase chain reaction and automated fragment analysis.

OBJECTIVES: To develop and evaluate a new method for determination of the CAG repeat length in Exon 1 of the androgen receptor gene. DESIGN AND METHODS: The method is based on PCR amplification of a DNA region encompassing the repeats and analysis of the length of the PCR product on a sequencing gel. One of the PCR primers was labeled with Cy5.5 fluorescent dye to facilitate detection after laser excitation. We used a fully automated system for electrophoretic separation of the PCR product and accurate sizing of the length of the PCR product using fragment analysis. RESULTS: The major advantages of the new technique are its simplicity, speed, accuracy, and reproducibility. Analysis of the CAG repeats in genomic DNAs from 18 males indicated that they were all hemizygous with a mean CAG repeat number of 22 (range 20-30 repeats). Among 60 DNAs from females, 16 were homozygous and 44 were heterozygous. The repeat length ranged from 17-30 with a mean of 22. In both males and females, the distribution of CAG repeats was bimodal. CONCLUSION: We anticipate that this improved method for CAG repeat analysis will find applications in clinical studies involving prostate and breast cancer patients.

Immunofluorometric assay of p53 protein versus sequencing of p53 exons 5 to 9 for the detection of p53 abnormalities in ovarian carcinoma.

p53 alteration, detected as mutation of the p53 gene or as accumulation of mutant p53 protein, is a common feature of most malignancies, including ovarian carcinoma, and may identify patients with unfavorable prognosis and resistance to chemotherapy. Tumor tissues from 55 patients with well or poorly differentiated (grades 1 or 3) primary epithelial ovarian carcinoma were assessed both for p53 protein overexpression by a sensitive time-resolved immunofluorometric assay employing DO-1 and CM-1 antibodies, and for genetic p53 abnormalities by direct sequencing of PCR-amplified exons 5 to 9. Sixteen p53 mutations (29%), including 3 deletions causing frameshifts as well as one nonsense and 12 missense point mutations were found in all exons except exon 9. Overexpression of p53 protein, defined as a concentration exceeding the 75th percentile, was found in 15 cases (27%), 10 of which had missense mutations (P < 0.01). Tumors with nonsense and frameshift mutations were p53-negative by immunoassay. Both p53 mutation (P = 0.04) and p53 protein accumulation (P < 0.01) were associated with stage III-IV disease, while p53 mutation was more closely related to grade 3 lesions (P = 0.04) and serous histotype (P = 0.01). These results indicate that p53 protein accumulation correlates well with missense point mutation in carcinoma of the ovary and, together with other evidence that p53 abnormality may be prognostic of outcome in this disease, suggest that the immunoassay of p53 protein may have clinical value.

Rapid sequencing of the p53 gene with a new automated DNA sequencer.

p53 is the most commonly mutated gene in human cancers. Approximately 90% of the p53 gene mutations are localized between domains encoding exons 5 to 8. Sequencing methods currently available are tedious and time-consuming and are not suitable for routine laboratory testing. In an effort to identify a simple and rapid sequencing method, we analyzed 16 preselected breast tumors and 18 preselected ovarian tumors, using a newly developed automated DNA sequencer. p53 gene mutations had been previously identified in these tumors, using a conventional automated sequencing procedure. Exons 5 to 8 were amplified by PCR, and the PCR products were subsequently subjected to cycle sequencing with the Sanger chain termination method, using Cy5.5-labeled primers. The sequencing mixture was then resolved on a newly developed automated DNA sequencer that can sequence approximately 300 bases of DNA in 30 min. Of these 16 breast tumors, two had mutations in exon 5, four in exon 6, three in exon 7, and three in exon 8. Of the 18 ovarian tumors, two had mutations in exon 5, five in exon 6, two in exon 7, and three in exon 8. In all cases, we identified the same mutations by both the new and the conventional sequencing procedures. Most mutations affected an arginine codon. These data demonstrate that the new method has the capability to provide accurate sequencing information in a fraction of the time and labor in comparison with current automated sequencing techniques. When such procedures are used, DNA sequencing may become a routine tool for identifying clinically important mutations for diagnosis and prognosis of patients with genetic, malignant, infectious, and other diseases.

Change in serum cholinesterase activity in Jamaican diabetics.

This study investigates the alteration of serum cholinesterase levels in diabetics and its possible relationship to blood glucose, insulin, triglyceride, and cholesterol levels. Fourteen phasic insulin-dependent diabetes mellitus patients were compared with 10 insulin-dependent diabetes mellitus, 10 noninsulin-dependent diabetes mellitus, and 10 normal controls. Each group was matched for age, sex, body mass index, and duration of diabetes. Mean age was 56.7 +/- 2.5 years; mean body mass index, 24.0 +/- 0.8 kg/m2; and mean duration of diabetes, 14.2 +/- 2.2 years. Serum acetylcholinesterase, insulin, triglyceride, and cholesterol levels as well as fasting blood sugar were all assayed using standard techniques. Results suggest an associated increase of serum acetylcholinesterase with triglyceride levels in diabetics and may point to a possible association between increased serum acetylcholinesterase and vascular complications in Jamaican diabetics.

Ascorbic acid and reduced glutathione concentration of human fetal tissues in relation to gestational age, fetal size and maternal nutritional status.

Studies were carried out on ascorbic acid and glutathione concentration in human fetal tissues with the progress of gestation. The glutathione concentration in human fetal liver and adrenal showed a decline during late gestation, the decline in the brain being earlier. This is consistent with the fall in ascorbic acid concentration in all tissues during late gestation. Glutathione concentration and glutathione/ascorbic acid ratio was significantly lower in the low income group than the high income group, confirming previous observations that state of nutrition may influence cellular glutathione.

Identification and isolation of three acetylcholinesterase inactivating fractions in the venom of Dendroaspis angusticeps.

Three fractions were isolated from the venom of Dendroaspis angusticeps by column chromatography on CM-Sephadex C-25. All the three fractions were shown to possess acetylcholinesterase inhibiting activity. The toxicity of the fractions as tested on mice were variable. Although the toxic signs were identical, fraction DaVI was highly lethal (LD50 1.9 microgram/g) whereas fractions DaIV and T39 were less lethal, the LD50 being 3.6 micrograms/g and 4.1 micrograms/g respectively. The three fractions significantly inhibited true acetylcholinesterase to the extent of 91-95%.

Gonadal and plasma testosterone and cholesterol in scorbutic guinea pigs.

Testes of pre- and post-pubertal guinea pigs were examined histologically and biochemically to see if ascorbic acid deficiency brought about any changes in their structure or function. Apart from a slight but significant fall in gonadal cholesterol there was no apparent change in the histology or testosterone content in scorbutic guinea pigs. Plasma cholesterol and testosterone were also similar in the control and scorbutic animals.