Men at risk of being a mutation carrier for hereditary breast/ovarian cancer: an exploration of attitudes and psychological functioning during genetic testing

Males with a BRCA1/BRCA2 mutation are not at greatly increased risk for cancer, whereas their (grand)daughters, and other female relatives who carry the mutation, are. Males from BRCA1/BRCA2 families may opt for genetic testing to confirm whether or not they may have transmitted the mutation to their children and, if so, to inform them at an appropriate age about the genetic risk and its implications. The psychological implications of genetic testing for men at risk of being a BRCA1/BRCA2 mutation carrier have received little attention. We report on 28 men requesting BRCA1 or BRCA2 testing, and their partners. Men were at 25% (n =4) or 50% risk (n =24) of being a mutation carrier, the majority with daughters and half of them with daughters aged over 20 years. Levels of psychological distress were assessed several weeks before and after disclosure of the test result. In addition, we investigated the level of intrusive thoughts and feelings about breast and ovarian cancer and the tendency to avoid these. By means of interviews and questionnaires, participants could report on (expected) emotional implications of genetic testing for themselves and their children, on experiences with cancer in the family and on personality trait optimism. Distress levels prior to the result in tested men and their partners were low. Many men and partners expected the test result to affect their children's, but not their own level of problems. Men without daughters and those with an optimistic personality had especially low distress prior to disclosure. Most men reported that they did not actively avoid the issue. Only four of the 28 men were identified as mutation carriers. High distress after disclosure of the result was reported by one mutation carrier and by three non-mutation carriers. Verbatim transcripts from interviews showed a large variation of psychological reactions in male mutation carriers (eg regarding guilt feelings). Low pre-test distress in males does not necessarily indicate avoidance of the issue. Future studies may indicate which psychological reactions occur in male mutation carriers when the problem becomes more acute, eg when a daughter is found to carry the mutation and/or is diagnosed with breast or ovarian cancer.

Nearly all hereditary paragangliomas in the Netherlands are caused by two founder mutations in the SDHD gene

Hereditary paragangliomas or glomus tumors are usually benign slow-growing tumors in the head and neck region. The inheritance pattern of hereditary paraganglioma is autosomal dominant with imprinting. Recently, we have identified the SDHD gene encoding subunit D of the mitochondrial respiratory chain complex II as one of the genes involved in hereditary paragangliomas. Here, we demonstrate that two founder mutations, Asp92Tyr and Leu139Pro, are responsible for paragangliomas in 24 and 6 of the 32 independently ascertained Dutch paraganglioma families, respectively. These two mutations were also detected among 20 of 55 isolated patients. Ten of the isolated patients had multiple paragangliomas, and in eight of these SDHD germline mutations were found, indicating that multicentricity is a strong predictive factor for the hereditary nature of the disorder in isolated patients. In addition, we demonstrate that the maternally derived wild-type SDHD allele is lost in tumors from mutation-carrying patients, indicating that SDHD functions as a tumor suppressor gene.

Effect of a tongue-tie on upper airway mechanics in horses during exercise

OBJECTIVE

To determine the effect of a tongue-tie on upper airway mechanics in exercising horses.

ANIMALS

5 Standardbreds.

PROCEDURE

Peak inspiratory and expiratory tracheal and pharyngeal pressures and airflow were measured while horses exercised on a treadmill with and without a tongue-tie. Respiratory rate was also measured. Horses ran at speeds that corresponded to 50 (HR50), 75, 90 (HR90), and 100% of maximal heart rate. The tongue-tie was applied by pulling the tongue forward out of the mouth as far as possible and tying it at the level of the base of the frenulum to the mandible with an elastic gauze bandage. Peak inspiratory and expiratory tracheal, pharyngeal, and translaryngeal resistance, minute ventilation, and tidal volume were calculated. Data were analyzed by use of 2-way repeated-measures ANOVA. For post hoc comparison of significant data, the Student-Newman-Keuls test was used.

RESULTS

We were unable to detect significant differences between groups for peak inspiratory or expiratory tracheal or pharyngeal resistance, peak pressure, peak expiratory flow, tidal volume, respiratory rate, or minute ventilation. Horses that ran with a tongue-tie had significantly higher peak inspiratory flows, compared with horses that ran without a tongue-tie. In the post hoc comparison, this effect was significant at 4 m/s, HR50, and HR90.

CONCLUSION AND CLINICAL RELEVANCE

Application of a tongue-tie did not alter upper respiratory mechanics in exercising horses and may be beneficial in exercising horses with certain types of obstructive dysfunction of the upper airways. However, application of a tongue-tie does not improve upper airway mechanics in clinically normal horses.

Atypical HNPCC owing to MSH6 germline mutations: analysis of a large Dutch pedigree

Hereditary non-polyposis colorectal cancer (HNPCC) is the most common genetic susceptibility syndrome for colorectal cancer. HNPCC is most frequently caused by germline mutations in the DNA mismatch repair (MMR) genes MSH2 and MLH1. Recently, mutations in another MMR gene, MSH6 (also known as GTBP), have also been shown to result in HNPCC. Preliminary data indicate that the phenotype related to MSH6 mutations may differ from the classical HNPCC caused by defects in MSH2 and MLH1. Here, we describe an extended Dutch HNPCC family not fulfilling the Amsterdam criteria II and resulting from a MSH6 mutation. Overall, the penetrance of colorectal cancer appears to be significantly decreased (p<0.001) among the MSH6 mutation carriers in this family when compared with MSH2 and MLH1 carriers (32% by the age of 80 v >80%). Endometrial cancer is a frequent manifestation among female carriers (six out of 13 malignant tumours). Transitional cell carcinoma of the urinary tract is also relatively common in both male and female carriers (10% of the carriers). Moreover, the mean age of onset of both colorectal cancer (MSH6 v MSH2/MLH1 = 55 years v 44/41 years) and endometrial carcinomas (MSH6 v MSH2/MLH1 = 55 years v 49/48 years) is delayed. As previously reported, we confirm that the pattern of microsatellite instability, in combination with immunohistochemical analysis, can predict the presence of a MSH6 germline defect. The detailed characterisation of the clinical phenotype of this kindred contributes to the establishment of genotype-phenotype correlations in HNPCC owing to mutations in specific mismatch repair genes.

Prediction of a mismatch repair gene defect by microsatellite instability and immunohistochemical analysis in endometrial tumours from HNPCC patients

Instability of microsatellite repeat sequences has been observed in colorectal carcinomas and in extracolonic malignancies, predominantly endometrial tumours, occurring in the context of hereditary non-polyposis colorectal cancer (HNPCC). Microsatellite instability (MSI) as a feature of human DNA mismatch repair (MMR)-driven tumourigenesis of the uterine mucosa has been studied primarily in sporadic tumours showing predominantly somatic hypermethylation of MLH1. The present study shows that all endometrial carcinomas (n=12) from carriers of MLH1 and MSH2 germline mutations demonstrate an MSI-high phenotype involving all types of repeat markers, while in endometrial carcinomas from MSH6 mutation carriers, only 36% (4 out of 11) demonstrate an MSI-high phenotype. Interestingly, an MSI-high phenotype was found in endometrial hyperplasias from MSH2 mutation carriers, in contrast to hyperplasias from MLH1 mutation carriers, which exhibited an MSI-stable phenotype. Instability of only mononucleotide repeat markers was found in both endometrial carcinomas and hyperplasias from MSH6 mutation carriers. In 29 out of 31 (94%) endometrial tumour foci, combined MSI and immunohistochemical analysis of MLH1, MSH2, and MSH6 could predict the identified germline mutation. The observation of MSI in endometrial hyperplasia and of altered protein staining for the MMR genes supports the idea that inactivation of MMR genes is an early event in endometrial tumourigenesis. A correlation was found between the variation in the extent and level of MSI and the age of onset of carcinoma, suggesting differences in the rate of tumour progression. A high frequency of MSI in hyperplasias, found only in MSH2 mutation carriers, might indicate a more rapid tumour progression, correlating with an earlier age of onset of carcinoma. The present study indicates that assessment of altered protein staining combined with MSI analysis of endometrial tumours might direct the mutational analysis of MMR genes.

Loss of heterozygosity mapping at chromosome arm 16q in 712 breast tumors reveals factors that influence delineation of candidate regions

Loss of heterozygosity (LOH) at the long arm of chromosome 16 occurs in at least half of all breast tumors and is considered to target one or more tumor suppressor genes. Despite extensive studies by us and by others, a clear consensus of the boundaries of the smallest region of overlap (SRO) could not be identified. To find more solid evidence for SROs, we tested a large series of 712 breast tumors for LOH at 16q using a dense map of polymorphic markers. Strict criteria for LOH and retention were applied, and results that did not meet these criteria were excluded from the analysis. We compared LOH results obtained from samples with different DNA isolation methods, ie., from microdissected tissue versus total tissue blocks. In the latter group, 16% of the cases were excluded because of noninterpretable LOH results. The selection of polymorphic markers is clearly influencing the LOH pattern because a chromosomal region seems more frequently involved in LOH when many markers from this region are used. The LOH detection method, i.e., radioactive versus fluorescence detection, has no marked effect on the results. Increasing the threshold window for retention of heterozygosity resulted in significantly more cases with complex LOH, i.e., several alternating regions of loss and retention, than seen in tumors with a small window for retention. Tumors with complex LOH do not provide evidence for clear-cut SROs that are repeatedly found in other samples. On disregarding these complex cases, we could identify three different SROs, two at band 16q24.3 and one at 16q22.1. In all three tumor series, we found cases with single LOH regions that designated the distal region at 16q24.3 and the region at 16q22.1. Comparing histological data on these tumors did not result in the identification of a particular subtype with LOH at 16q or a specific region involved in LOH. Only the rare mucinous tumors had no 16q LOH at all. Furthermore, a positive estrogen content is prevalent in tumors with 16q LOH, but not in tumors with LOH at 16q24.3 only.

PCR artifacts in LOH and MSI analysis of microdissected tumor cells

Polymerase chain reaction (PCR) analysis to study loss of heterozygosity (LOH) and microsatellite instability (MSI) in tumors is widely used. Microdissection techniques are applied to obtain tumor-specific tissue cells. By microdissection, however, the amount of template DNA extracted may vary considerably and interfere with optimal PCR amplification. To circumvent LOH and MSI misinterpretations due to low DNA input, we have assessed the critical level of DNA input for reliable PCR analysis. PCR analysis was performed by using 18 polymorphic markers (mono-, di-, tri-, and tetranucleotide) on DNA derived from both paraffin-embedded, formalin-fixed, and fresh frozen tumor specimens at template input levels ranging from 0.05 to 25.0 ng. We show a highly significant relation between DNA input and the occurrence of LOH and MSI artifacts. Furthermore, for DNA extracted from paraffin-embedded material, the percentage of LOH artifacts is significantly higher compared with DNA extracted from frozen tissue. For reliable PCR analyses using a mono-, di-, tri-, or tetranucleotide marker, a minimum of 10.0 ng DNA is required when DNA is isolated from formalin-fixed, paraffin-embedded tissue and 5.0 ng when isolated from fresh frozen tissue. HUM PATHOL 31:1414-1419.

[From gene to disease; from BRCA1 or BRCA2 to breast cancer]

Hereditary breast cancer is a heterogeneous syndrome, both phenotypically and genetically. It affects about 5% of all breast cancer patients. The presence of ovarian cancer or breast cancer in males defines important subtypes. BRCA1 and BRCA2 are involved in all hereditary breast cancer syndromes in varying degrees. Both genes confer strongly elevated breast and ovarian cancer risks in mutation carriers, but these risks may be subject to modifying effects by other factors (genetic and/or environmental) at the individual level. In the Netherlands, DNA testing is offered under the national health insurance programme and has led to the identification of over 500 families with either a BRCA1 or BRCA2 mutation. The results of the test are being used widely by Dutch women in the decision for or against prophylactic surgery.

Genetic analysis of a breast-ovarian cancer family, with 7 cases of colorectal cancer linked to BRCA1, fails to support a role for BRCA1 in colorectal tumorigenesis

Mutations in the BRCA1 gene cause strongly elevated risks of breast and ovarian cancers but may also confer a 3-fold increased risk for colorectal cancer. To address the relationship between BRCA1 carriership and colorectal tumorigenesis, we studied the genetics of a breast-ovarian cancer family with 7 cases of colorectal cancer. A germline 3938insG mutation in BRCA1 was found in 5 breast-cancer patients, 1 with ductal carcinoma in situ, ovarian cancer and an adenoma of the colon, and in 4/5 colorectal-cancer patients investigated. However, the youngest patient, diagnosed at age 23, was a non-carrier. Loss of the wild-type BRCA1 allele was observed in 3/3 breast tissues (2 breast carcinomas and 1 ductal carcinoma in situ) but in 0/6 colorectal tissues (5 carcinomas and 1 adenoma), suggesting that BRCA1 loss is not critical for colorectal tumorigenesis. To examine the possibility that an as yet unknown gene linked to BRCA1 was involved in the colorectal cancers, chromosome 17 segregation was studied with 7 polymorphic markers encompassing a 20 cM region including BRCA1. None of these markers showed complete allele sharing among all 5 colorectal-cancer patients studied. Clinical history, mutation analysis and microsatellite instability analysis excluded a role for any of the known colorectal-cancer susceptibility genes. In 4 other Dutch families carrying the same BRCA1 mutation, only 1 colorectal-cancer case was reported, of which the carrier status is unknown.

Near-haploidy and subsequent polyploidization characterize the progression of peripheral chondrosarcoma

Chondrosarcomas are malignant cartilaginous tumors arising centrally in bone (central chondrosarcoma), or secondarily within the cartilaginous cap of osteochondroma (peripheral chondrosarcoma). We previously used DNA flow cytometry to demonstrate that near-haploidy is relatively frequent in peripheral chondrosarcomas. We performed fluorescence in situ hybridization (FISH) to interphase nuclei using centromeric probes, a genome wide loss of heterozygosity (LOH) analysis, and comparative genomic hybridization on five peripheral chondrosarcomas. We demonstrated near-haploidy in two low-grade tumors with only one copy and LOH of most chromosomes. Few chromosomes are disomic, with retention of heterozygosity and overrepresentation at comparative genomic hybridization. One tumor contains both a near-haploid clone with chromosomes in monosomic and disomic state, and an exactly duplicated clone. Two high-grade tumors clearly demonstrate polyploidization because most chromosomes show LOH and two copies at FISH, whereas few chromosomes have four copies with retention of heterozygosity. Using DNA from a relative, we demonstrate that chromosome loss is random regardless of parental origin. Using FISH on paraffin slides, we exclude near-haploidy to result from meiosis-like division in binucleated cells, characteristic for chondrosarcoma. In conclusion, our results indicate that near-haploidy characterizes the progression from osteochondroma toward low-grade chondrosarcoma. Moreover, further progression toward high-grade chondrosarcoma is characterized by polyploidization.

Prediction of a mismatch repair gene defect by microsatellite instability and immunohistochemical analysis in endometrial tumours from HNPCC patients

Instability of microsatellite repeat sequences has been observed in colorectal carcinomas and in extracolonic malignancies, predominantly endometrial tumours, occurring in the context of hereditary non-polyposis colorectal cancer (HNPCC). Microsatellite instability (MSI) as a feature of human DNA mismatch repair (MMR)-driven tumourigenesis of the uterine mucosa has been studied primarily in sporadic tumours showing predominantly somatic hypermethylation of MLH1. The present study shows that all endometrial carcinomas (n=12) from carriers of MLH1 and MSH2 germline mutations demonstrate an MSI-high phenotype involving all types of repeat markers, while in endometrial carcinomas from MSH6 mutation carriers, only 36% (4 out of 11) demonstrate an MSI-high phenotype. Interestingly, an MSI-high phenotype was found in endometrial hyperplasias from MSH2 mutation carriers, in contrast to hyperplasias from MLH1 mutation carriers, which exhibited an MSI-stable phenotype. Instability of only mononucleotide repeat markers was found in both endometrial carcinomas and hyperplasias from MSH6 mutation carriers. In 29 out of 31 (94%) endometrial tumour foci, combined MSI and immunohistochemical analysis of MLH1, MSH2, and MSH6 could predict the identified germline mutation. The observation of MSI in endometrial hyperplasia and of altered protein staining for the MMR genes supports the idea that inactivation of MMR genes is an early event in endometrial tumourigenesis. A correlation was found between the variation in the extent and level of MSI and the age of onset of carcinoma, suggesting differences in the rate of tumour progression. A high frequency of MSI in hyperplasias, found only in MSH2 mutation carriers, might indicate a more rapid tumour progression, correlating with an earlier age of onset of carcinoma. The present study indicates that assessment of altered protein staining combined with MSI analysis of endometrial tumours might direct the mutational analysis of MMR genes.

Prevalence of BRCA1 in a hospital-based population of Dutch breast cancer patients

The prevalence of disease-related BRCA1 mutations was investigated in 642 Dutch breast cancer patients not selected for family history or age at diagnosis. They were tested for germline mutations in the BRCA1 gene using an assay which detects small deletions and insertions (DSDI), as well as the two major genomic founder deletions present in the Dutch population. Data on family history and bilateral breast cancer were obtained retrospectively. Ten protein truncating mutations were detected and one in-frame deletion with an unknown relation to disease risk. Four patients carried the Dutch founder deletion of exon 22. Based on these results the estimated prevalence of breast cancer in the general population in the Netherlands attributable to BRCA1 mutations is 2.1%. Under 40 years-of-age and under 50 years-of-age this prevalence is 9.5% and 6. 4%, respectively. All mutation carriers were under 50 years-of-age at diagnosis of the first breast cancer, and five did not have any relative with breast cancer. The proportions of bilateral breast cancer in the mutation carriers and non-carriers did not differ from each other. These data indicate that in the general Dutch breast cancer population the great majority of BRCA1 mutations will be found in women diagnosed under 50 years-of-age.

Distinction between HLA class I-positive and -negative cervical tumor subpopulations by multiparameter DNA flow cytometry

BACKGROUND

The study of the molecular-genetic basis of heterogeneity of HLA class I expression in solid tumors is hampered by the lack of reliable rapid cell-by-cell isolation techniques. Hence, we studied the applicability of a flow cytometric approach (Corver et al.: Cytometry 2000;39;96-107).

METHODS

Cells were isolated from five fresh cervical tumors and simultaneously stained for CD45 or vimentin (fluorescein isothiocyanate fluorescence), Keratin (R-phycoerythrin fluorescence), HLA class I (APC fluorescence), and DNA (propidium iodide fluorescence). A dual-laser flow cytometer was used for fluorescence analysis. Tissue sections from the corresponding tumors were stained for HLA class I antigens, keratin, vimentin, or CD45.

RESULTS

Flow cytometry enabled the simultaneous measurement of normal stromal cells (vimentin positive), inflammatory cells (CD45 positive), epithelial cells (keratin positive), and DNA content readily. Normal stromal/inflammatory cells served as intrinsic HLA class I-positive as well as DNA-diploid references. Good DNA histogram quality was obtained (average coefficient of variation < 4%). Intratumor keratin positive subpopulations differing in HLA class I expression as well as DNA content could be clearly identified. Losses of allele-specific HLA class I expression found by immunohistochemistry were also detected by flow cytometry.

CONCLUSIONS

We conclude that multiparameter DNA flow cytometry is a powerful tool to study loss of HLA class I expression in human cervical tumors. The method enables flow-sorting of discrete tumor and normal cell subpopulations for further molecular genetic analysis.

Allelotype analysis of flow-sorted breast cancer cells demonstrates genetically related diploid and aneuploid subpopulations in primary tumors and lymph node metastases

Flow cytometric DNA content measurements have demonstrated extensive DNA ploidy heterogeneity in primary breast carcinomas. However, little is known at the molecular level about the clonal relationship between these tumor cell subpopulations, or about the molecular genetic changes associated with aneuploidization. We have used flow cytometric cell sorting to dissect some of this complexity by isolating clonal subpopulations in breast carcinomas for comparative molecular genetic analysis. Clonal subpopulations were isolated from 12 primary breast carcinomas and 5 lymph node metastases from 4 cases based on DNA content and cytokeratin 8/18 labeling. DNA from these clones was screened for allelic imbalances with 92 polymorphic microsatellite markers mapped to 39 different chromosome arms. Diploid and aneuploid populations were concurrently present in 11 out of 12 primary tumors. The DNA ploidy status of primary tumors was identical to that of the related lymph node metastases. Allelic imbalance was present in 10 out of 11 diploid clones (mean, 3.4 +/- 4.2). All allelic imbalances observed in the diploid clones recurred in the cognate aneuploid clones, but were, in the latter, accompanied by additional allelic imbalances at other loci and/or chromosome arms (mean, 10.9 +/- 5.8). In only two of the four metastatic cases did the allelotypes of metastatic clones show small differences relative to their cognate primary tumors. The primary diploid tumor clone recurred in all lymph node metastases. This study indicates that the majority of allelic imbalances in breast carcinomas are established during generation of DNA ploidy diversity. Recurrence of the allelic imbalances in diploid clones in the aneuploid clones suggests linear tumor progression, whereas the simultaneous presence of early diploid and advanced aneuploid clones in both primary and metastatic tumor sites suggests that acquisition of metastatic propensity can be an early event in the genetic progression of breast cancer.

Concentration of cardiac troponin I in a horse with a ruptured aortic regurgitation jet lesion and ventricular tachycardia

An 18-year-old Thoroughbred gelding was evaluated because of sudden onset of ventricular tachycardia and signs of colic. Three years earlier, a diastolic decrescendo murmur, consistent with aortic regurgitation, had been detected, but the horse continued to perform well and compete successfully. Cardiac ultrasonographic examination revealed a defect in the interventricular septum below the aortic root, and serum concentrations of cardiac troponin I (cTnI) were higher than those measured in clinically normal horses. Repeated development of tachyarrhythmia during hospitalization prompted a decision to euthanatize the horse. A ruptured endocardial jet lesion below the aortic valve with formation of a cleft into the interventricular septum was found on necropsy. This report of increased serum cTnI concentrations in a horse with myocardial disease and our other findings suggest that assessment of cardiac troponin concentrations may be a useful tool in the evaluation of horses with suspected myocardial disease.

Three germline mutations in the TP53 gene

Three germline mutations in the TP53 tumor-suppressor gene are reported, two of which are not reported previously. A missense mutation at codon 265 of TP53 was found in three patients of a family that complied with the definition of the Li-Fraumeni syndrome. A nonsense mutation in codon 306 was found in a woman who had had a rhabdomyosarcoma at age 4 and a subsequent breast cancer at age 22. She was part of a Li-Fraumeni-like family, but the parental origin of the mutation could not be traced. Finally, while screening for somatic alterations in TP53 in a series of 141 sporadic breast tumors, we detected a constitutional missense mutation in codon 235 in a woman diagnosed with breast cancer at age 26 and a recurrence 4 years later. The recurrence, but not the primary tumor, showed an additional missense mutation at codon 245 as well as loss of the wild-type allele. This suggests that the 245 mutation was particularly important for tumor progression and that there might exist heterogeneity in terms of cancer predisposition potential among the various germline TP53 mutations.

Estimation of growth rate in patients with head and neck paragangliomas influences the treatment proposal

BACKGROUND

Extraadrenal paragangliomas of the head and neck are tumors with variable clinical behavior. Because tumor growth as well as surgery can cause disabling loss of function, knowledge of the natural history of paragangliomas is important for the development of treatment strategies.

METHODS

The tumor volume, growth rate, and tumor doubling time of 48 paragangliomas at different anatomic locations in the head and neck region were estimated retrospectively using sequential radiologic imaging.

RESULTS

During a mean follow-up period of 4.2 years, a volume increase of > 20% was observed in 60% of the paragangliomas. In these cases the median growth rate was 1.0 mm/year and the median tumor doubling time was 4. 2 years. More growing tumors were observed in intermediate size tumors than in very small or large paragangliomas, suggesting a biphasic growth pattern.

CONCLUSIONS

The majority of head and neck paragangliomas have a very low growth rate. Although management of paragangliomas also is determined by other parameters, preoperative estimation of the tumor doubling time may influence the treatment proposal. A "wait and scan" policy must be considered in all cases.

Allelotype analysis of flow-sorted breast cancer cells demonstrates genetically related diploid and aneuploid subpopulations in primary tumors and lymph node metastases

Flow cytometric DNA content measurements have demonstrated extensive DNA ploidy heterogeneity in primary breast carcinomas. However, little is known at the molecular level about the clonal relationship between these tumor cell subpopulations, or about the molecular genetic changes associated with aneuploidization. We have used flow cytometric cell sorting to dissect some of this complexity by isolating clonal subpopulations in breast carcinomas for comparative molecular genetic analysis. Clonal subpopulations were isolated from 12 primary breast carcinomas and 5 lymph node metastases from 4 cases based on DNA content and cytokeratin 8/18 labeling. DNA from these clones was screened for allelic imbalances with 92 polymorphic microsatellite markers mapped to 39 different chromosome arms. Diploid and aneuploid populations were concurrently present in 11 out of 12 primary tumors. The DNA ploidy status of primary tumors was identical to that of the related lymph node metastases. Allelic imbalance was present in 10 out of 11 diploid clones (mean, 3.4 +/- 4.2). All allelic imbalances observed in the diploid clones recurred in the cognate aneuploid clones, but were, in the latter, accompanied by additional allelic imbalances at other loci and/or chromosome arms (mean, 10.9 +/- 5.8). In only two of the four metastatic cases did the allelotypes of metastatic clones show small differences relative to their cognate primary tumors. The primary diploid tumor clone recurred in all lymph node metastases. This study indicates that the majority of allelic imbalances in breast carcinomas are established during generation of DNA ploidy diversity. Recurrence of the allelic imbalances in diploid clones in the aneuploid clones suggests linear tumor progression, whereas the simultaneous presence of early diploid and advanced aneuploid clones in both primary and metastatic tumor sites suggests that acquisition of metastatic propensity can be an early event in the genetic progression of breast cancer.

A sporadic breast tumor with a somatically acquired complex genomic rearrangement in BRCA1

Germ-line mutations in BRCA1 cause a substantial proportion of inherited breast cancer, and most result in inactivated BRCA1 proteins upon translation. Tumours developing in BRCA1 mutation carriers generally show loss of the wild-type allele. However, acquired inactivating mutations in BRCA1 in non-inherited breast tumours showing loss of heterozygosity at the gene locus have not been detected so far. Here we provide evidence that such mutations can be detected in a small proportion of breast tumours. Prompted by recent reports of Alu-mediated large genomic rearrangements in BRCA1, we have investigated whether such rearrangements might occur in sporadic breast cancer as well and have been missed thus far by traditional PCR-based mutation screening technology. To this end, we performed Southern blot analysis of 81 apparently sporadic breast tumours using probes covering exons 6-24 and 3 restriction enzymes. We identified 1 case with an acquired rearrangement (1.2%), indicating that BRCA1 inactivation through changes in the primary genomic sequence of the gene is uncommon in breast cancer. Genes Chromosomes Cancer 27:295-302, 2000.

Mutations in SDHD, a mitochondrial complex II gene, in hereditary paraganglioma

Hereditary paraganglioma (PGL) is characterized by the development of benign, vascularized tumors in the head and neck. The most common tumor site is the carotid body (CB), a chemoreceptive organ that senses oxygen levels in the blood. Analysis of families carrying the PGL1 gene, described here, revealed germ line mutations in the SDHD gene on chromosome 11q23. SDHD encodes a mitochondrial respiratory chain protein-the small subunit of cytochrome b in succinate-ubiquinone oxidoreductase (cybS). In contrast to expectations based on the inheritance pattern of PGL, the SDHD gene showed no evidence of imprinting. These findings indicate that mitochondria play an important role in the pathogenesis of certain tumors and that cybS plays a role in normal CB physiology.

Four-color multiparameter DNA flow cytometric method to study phenotypic intratumor heterogeneity in cervical cancer

BACKGROUND

Multiparameter DNA flow cytometry using a one-laser bench-top flow cytometer has been restricted to three different colors. The two laser FACSCalibur has recently been introduced, allowing four-color analysis. Therefore, we optimized and extended our three-color method (Corver et al., 1994, Corver et al. 1996) to a four-color analysis of phenotypic intra-tumor heterogeneity using a bench-top flow cytometer.

METHODS

First, the effect of a range of different propidium iodide (PI) and TO-PRO-3 iodide (TP3) concentrations on the coefficient of variation (CV) of the DNA histograms was measured using paraformaldehyde-fixed lysolecithin-permeabilized peripheral blood lymphocytes (PBLs) and SiHa and HeLa cervical cancer cells. Second, labeling freshly isolated cervical cancers from solid tumors was optimized with a mixture of anti-keratin antibodies. Third, the FACSCalibur hardware was modified, thereby allowing the simultaneous measurement of allophycocyanin (APC) fluorescence (FL4) in combination with FL3 pulse processing (FL3-W vs. FL3-A). The optimized procedure was then applied to cell suspensions from four different human cervical cancers to study phenotypic intratumor heterogeneity. Cell suspensions were simultaneously stained for DNA (PI, fluorescence) and three cellular antigens: (a) the epithelial cell-adhesion molecule (Ep-CAM; APC fluorescence), (b) keratin (R-phycoerythrin [RPE] fluorescence) to identify the epithelial fraction, and (c) vimentin (fluorescein-isothiocyanate [FITC] fluorescence) to label stromal cells.

RESULTS

Overall, PI produced better CVs than did TP3. The optimal concentration of PI was 50-100 microM for all cells tested. Average CVs were 1.76% (PBL), 3.16% (HeLa), and 2.50% (SiHa). Optimal TP3 concentrations were 0.25-2.0 microM. Average CVs were 2. 58% (PBL), 5.16% (HeLa), and 3.96% (SiHa). Inter- or intra-DNA stem line heterogeneity of Ep-CAM expression was observed in the keratin-positive fractions. Vimentin-positive, keratin-negative cells were restricted to the DNA diploid fraction.

CONCLUSIONS

PI is a superior DNA stain to TP3 when using intact normal PBL and human cancer cells. Four-color high-resolution multiparameter DNA flow cytometry allows the identification of intratumor subpopulations using PI as DNA stain and FITC, RPE, and APC as reporter molecules. The FACSCalibur bench-top flow cytometer can be used for this purpose, allowing the application of this technique in clinical laboratories.

Molecular genetic characterization of both components of a dedifferentiated chondrosarcoma, with implications for its histogenesis

Dedifferentiated chondrosarcoma is defined as a high-grade, anaplastic sarcoma adjacent to a low-grade malignant cartilage-forming tumour. Controversy remains as to whether the anaplastic and cartilaginous components are derived from a common precursor cell, or whether they represent separate genotypic lineages (collision tumour). Both components of a case of dedifferentiated chondrosarcoma were therefore separately investigated by loss of heterozygosity (LOH) analysis, comparative genomic hybridization (CGH), DNA flow cytometry, and p53 analysis. Both showed p53 overexpression and an identical somatic 6 bp deletion in exon 7 of p53. Combination of the CGH and LOH results revealed that both components had lost the same copy of chromosome 13. These results provide compelling evidence in this case for a common origin, instead of the 'collision tumour' theory. Certain genotypic alterations were not shared. The anaplastic component showed severe aneuploidy, LOH at additional loci, and amplification and deletion of several chromosome parts. In contrast, the cartilaginous component had lost chromosomes 5, 22, 17p and part of 16p and revealed an amplification of 17q. The LOH and CGH results further demonstrated that the two components had lost a different copy of chromosome 4. Thus, a substantial number of genetic alterations have occurred after the diversion of the two components, indicating that the separation of the two clones, derived from a single precursor, was a relatively early event in the histogenesis of this case of dedifferentiated chondrosarcoma.

Screening for BRCA2 mutations in 81 Dutch breast-ovarian cancer families

We have analysed 81 families with a history of breast and/or ovarian cancer for the presence of germline mutations in BRCA2 with a number of different mutation screening techniques. The protein truncation test (PTT) for exons 10 and 11 detected four different frame-shifting mutations in six of these families. Four of the remaining 75 families had given positive linkage evidence for being due to BRCA2. In these families the entire coding region was analysed by single-strand conformational polymorphism, leading to the detection of a non-sense and a splice-site mutation in two of them. While these studies were in progress, Southern analysis of BRCA1 revealed that in our study-population of 81 families, 15 families were segregating either the exon 13 or exon 22 deletion in BRCA1 (Petrij-Bosch et al (1997) Nat Genet 17: 341-345). This prompted us to examine BRCA2 in the remaining 58 families by Southern analysis, using two different restriction enzymes. No aberrations were found in the restriction patterns. Thus, contrary to BRCA1, large genomic rearrangements within the BRCA2 gene do not represent a major mutation mechanism among Dutch breast cancer families.

Mutations in exons 5-8 of the p53 gene, independent of their type and location, are associated with increased apoptosis and mitosis in invasive breast carcinoma

In breast cancer, mutations located in the zinc-binding functional domains of the p53 gene have been reported to predict a worse prognosis and a worse response to treatment with doxorubicin, compared with mutations in other parts within exons 5-8 of the gene. Similarly, mutations in residues of p53 that directly contact DNA have been associated with a poor prognosis. To investigate whether these specific p53 mutations are associated with differences in the rate of apoptosis and/or mitosis, or expression of the anti-apoptotic Bcl-2 protein, these parameters were evaluated in 89 invasive breast cancers with a confirmed p53 mutation in exons 5-8 and in 99 tumours without a p53 mutation in exons 5-8. Neither mutations located in the zinc-binding functional domains nor mutations in residues that directly contact DNA were associated with alterations in mitotic or apoptotic activity. However, compared with the wild-type p53 tumours, both apoptotic and mitotic indices showed an approximately two-fold increase in the mutant p53 group ( p< 0. 001). The presence of a p53 mutation was also associated with the presence of tumour necrosis ( p< 0.001), high tumour grade ( p< 0. 001) and low expression of Bcl-2 ( p< 0.001). Our data support the concept that in invasive breast carcinoma, loss of p53 function is involved in enhanced proliferation rather than decreased apoptosis and that the resulting acceleration of cell turnover may enhance clonal evolution and tumour progression.