Characterization of specific IgE response in vitro against protein and drug allergens using atopic and normal donors

BACKGROUND

As the incidence of allergy to different compounds increases in society, the need to understand and characterize specific IgE responses becomes obvious. Different cell culture systems have been evaluated for their ability to support such IgE secretion.

METHODS

One system employed human peripheral lymphocytes (PBL) from normal donors stimulated with anti-CD3 activated T cells with or without the presence of allergens like benzylpenicillin (BP) and Phlenum pratense (PP). Secretion of IgE was analyzed in ELISA and compared to the IgG response to the nonallergenic antigen tetanus toxoid (TT). Another system employed stimulation of T and B cells with a heterotope, consisting of a T helper cell epitope derived from TT, and a B cell allergen epitope derived from BP. The specific IgE secretion was compared, using lymphocytes from normal as well as BP-allergic donors.

RESULTS

Anti-CD3 stimulated T cells supported BP-specific IgE secretion in six of 11 normal donors. This response was inhibited in four donors and enhanced in two donors by the addition of the BP-allergen to the culture. In contrast, addition of the protein allergen (PP) or antigen (TT) to the same culture system inhibited both IgE and IgG synthesis in all experiments. Cells from the majority (10/16) of the BP-allergic donors failed to produce BP-specific IgE in vitro, when cultured in the presence of allergen.

CONCLUSIONS

An allergen specific immune response is readily generated in vitro. The differential response against benzylpenicillin between different donor categories most probably reflects the level of pre-exposure to this allergen in vivo.

High frequency of LOH, MSI and abnormal expression of FHIT in gastric cancer

The FHIT gene is a putative tumour suppressor gene. In this study, we analysed a set of 50 gastric tumours for alterations of FHIT, and found 38 of 45 tumours (84%) exhibiting loss of heterozygosity (LOH) within the FHIT gene. We used both nested Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) and single step RT-PCR to analyse the FHIT transcripts and found 34 of 39 (87%) tumours and seven of the 11 (64%) corresponding non-cancerous tissues showed low or aberrant expression of FHIT mRNA and the appearance of the aberrant FHIT transcripts depended on the conditions of the RT-PCR. In these aberrant transcripts, frequent deletions and/or insertions were detected by direct sequencing. All breakpoints for deletions and insertions were at splicing sites. All insertions came from the adjacent introns, whose appearance was completely in accordance with the 'GU-AG' rule for pre-mRNA splicing. It may be suggested that an alternative splicing mechanism functions in the formation of these aberrant transcripts. The fragile nature of FRA3B within the FHIT gene could be responsible for the formation of the aberrant mRNA. Negative or reduced Fhit expression was detected in 39 of 50 tumours (78%). Moreover, an association was found between abnormal Fhit expression and positive node status (P=0.012). Thirteen of 48 tumours (27%) displayed microsatellite instability (MSI), among which 10 tumours also showed MSI within the FHIT gene. Furthermore, we detected an association between MSI and negative node status (P=0.02). We conclude that the abnormalities of FHIT, presumably associated with the unstable nature of FRA3B within the FHIT gene, are involved in the carcinogenesis of gastric cancer, and lack of mismatch repair (MMR) could possibly promote its alteration in a subset of gastric tumours.

CD40 employs p38 MAP kinase in IgE isotype switching

IgE switching requires the prior induction of C epsilon germline transcripts which is mediated by the concerted binding of STAT-6 and NF kappa B to the C epsilon promoter. These transcription factors are regulated by IL-4 and CD40, respectively. However the latter can effect other signaling pathways and the present study explores the role of p38 MAPK in induction of C epsilon germline transcripts. CD40 and IL-4, both alone and in synergy, were initially shown to activate the C epsilon promoter in a B cell lymphoma cell line. Under the same conditions CD40 caused activation of p38 MAPK, whereas IL-4 was ineffective. The p38 MAPK inhibitor, SB203580, and a dominant negative form of p38 MAPK decreased the CD40 activation of the C epsilon promoter by reducing the ability of CD40 to increase the transactivation potential of NF kappa B. This study suggests that p38 MAPK is crucially important in mediating CD40 activation of NF kappa B which acts to induce C epsilon germline transcripts, ultimately facilitating IgE switching.

Alterations of the FHIT gene in breast cancer: association with tumor progression and patient survival

Our previous results on breast tumors show that LOH (loss of heterozygosity) at the FHIT locus is associated with reduced Fhit protein expression. We have also shown that LOH at this locus is significantly higher in tumors from patients carrying the BRCA2 999de15 mutation than in tumors without this mutation, presumably because of lack of DNA repair. Here, our aim was to determine the relationship of FHIT LOH with breast tumor progression. Five microsatellite markers located within the FHIT gene were typed in 239 breast tumors and corresponding normal tissue, and the LOH results were compared with clinicopathologic factors and LOH at other chromosome regions. LOH at FHIT is associated with estrogen- and progesterone-negative breast tumors, high S-phase fraction, reduced patient survival, and LOH at chromosome regions 6q, 7q, 8p, 9p, 11p, 11q, 13q, 16q, 17p, 17q, 18q, and 20q. A multivariate analysis shows that LOH at FHIT results in a 60% increased relative risk of dying. We conclude that the loss of FHIT results in growth advantage of breast tumor cells, is associated with unstable genome, and may be of prognostic value.

FHIT alterations in breast cancer

The FHIT gene encodes a diadenosine hydrolase and may be involved in growth control pathways of the cell. Studies on protein-protein interactions, cell lines, including tumourigenicity tests, and knockout mice suggest that the Fhit protein is involved in cell proliferation and apoptosis, and might act as a tumour suppressor. In several different cancers, including breast cancer, alterations in the FHIT gene have been detected in high frequency. The most common alterations are: deletions, DNA hypermethylation, abnormal transcripts and reduced expression at RNA and protein level. The FHIT gene is located at the FRA 3B fragile site at chromosome 3p 14.2, and alterations in the FHIT gene and Fhit protein have been found associated with genome instability, particularly in BRCA 2 mutated breast tumours. This paper will focus on some of the functional aspects of the Fhit protein with respect to tumour pathogenesis and on aberrations detected in breast cancer.

Similar regions of human chromosome 3 are eliminated from or retained in human/human and human/mouse microcell hybrids during tumor growth in severe combined immunodeficient (SCID) mice

By passaging microcell hybrids (MCHs) containing human chromosome 3 (chr3) on A9 mouse fibrosarcoma background through severe combined immunodeficient (SCID) mice (elimination test), we have previously defined a 1-Mb-long common eliminated region 1 (CER1) at 3p21.3, a second eliminated region (ER2) at 3p21.1-p14 and a common retained region (CRR) at 3q26-qter. In the present work, chr3 was transferred by microcell fusion into the human nonpapillary renal cell carcinoma line KH39 that contained uniparentally disomic chr3. Four MCHs were generated. Compared with KH39, they developed fewer and smaller tumors, which grew after longer latency periods in SCID mice. The tumors were analyzed in comparison with corresponding MCHs by chr3 arm-specific painting, 19 fluorescent in situ hybridization (FISH) probes, and 27 polymorphic markers. Three MCHs that maintained the intact exogenous chr3 in vitro lost one 3p copy in all 11 tumors. Seven of 11 tumors lost the exogenous 3p, whereas four tumors contained mixed cell populations that lacked either the exogenous or one endogenous KH39 derived 3p. In one MCH the exogenous chr3 showed deletions within CER1 and ER2 already in vitro. It remained essentially unchanged in 8/9 derived tumors. The third, exogenous copy of the 3q26-q27 region (part of CRR) was retained in 16/20 tumors. It can be concluded that the human/human MCH-based elimination test identifies similar eliminated and retained regions on chr3 as the human/murine MCH-based test.

Low-frequency magnetic noise in micron-scale magnetic tunnel junctions

We have observed low-frequency noise due to quasiequilibrium thermal magnetization fluctuations in micron-scale magnetic tunnel junctions (MTJs). This strongly field-dependent magnetic noise occurs within the magnetic hysteresis loops, either as 1/f or Lorentzian (random telegraph) noise. We attribute it to the thermally excited hopping of magnetic domain walls between pinning sites. Our results show that magnetic stability is a crucial factor in reducing the low-frequency noise in small MTJs.

Rapid polarization of Th2 cells during induction of antigen-specific IgE antibodies in vitro

BACKGROUND

Type 2 T-helper cells (Th2) are involved in the regulation of the humoral immune response against antigens and allergens and directly affect which isotype will be produced. The mechanism that regulates antigen-specific IgE secretion and immune deviation is still not known.

OBJECTIVES

To delineate mechanisms behind antigen-specific IgE secretion we have used in vitro immunization and focused on T-cell phenotype and the activation status of the transcription factor NFkappaB.

METHODS

Peripheral blood lymphocytes (PBMC) from seronegative donors were immunized in vitro with a peptide consisting of both a T-cell and a B-cell epitope.

RESULTS

Antigen-specific IgE antibodies could be detected after a primary immunization, during which T-helper cells secreted type 2 cytokines. Specific IgE was also detected in the secondary immunization, but due to a rapid polarization from Th2 to Th1 phenotype, exogenous IL-4 was required for the specific IgE secretion. Analysis of NFkappaB activation in B and T cells during primary and secondary immunization showed that NFkappaB could be detected in both B and T cells during primary immunization, but was dependent on exogenous IL-4 in the secondary immunization.

CONCLUSION

This is the first evidence of antigen-specific IgE induction in vitro using naive B cells, demonstrating the involvement of T-helper cell phenotype and NFkappaB and demonstrates the usefulness of in vitro cultures to study the effect of antigens on human immunocytes.

Analysis of the fragile histidine triad (FHIT) gene in lobular breast cancer

The fragile histidine triad (FHIT) gene is a candidate tumour suppressor gene in breast and other cancers. We investigated deletions within the FHIT gene in lobular breast cancer and found that 16% of cases showed loss of heterozygosity (LOH) within the gene. We compared LOH within FHIT in lobular and ductal breast tumours and found a significant association between LOH at FHIT and the ductal histological type (P<0.001). To determine whether genomic alteration of the FHIT gene in lobular breast cancer leads to Fhit inactivation we have assessed the level of Fhit expression by immunohistochemical detection and determined that 27% (15 of 55) consecutive sporadic lobular tumours showed negative or reduced Fhit expression. A significant association was found between LOH at the FHIT gene and reduced Fhit expression in lobular and ductal tumours (P=0.025 and P=0.001, respectively). Thus, genetic alterations within the FHIT gene, leading to loss of Fhit protein, may play an important role in the carcinogenesis of a significant number of sporadic lobular breast cancers, even though the apparent frequency of genomic alterations within the gene is lower than in ductal breast cancer.

Altered expression of E-cadherin in breast cancer. patterns, mechanisms and clinical significance

Reduced cell adhesion brought about by altered surface expression of E-cadherin has been implicated in invasive and metastatic malignant growth. We investigated the patterns of immunohistochemical E-cadherin expression in 120 breast carcinomas. Furthermore, we analysed DNA from the same samples for loss of heterozygosity (LOH) using three separate microsatellite markers on chromosome 16q22.1. Finally, the clinical outcome was ascertained for 108 patients. 19% (18/97) of infiltrating ductal carcinomas showed complete loss of E-cadherin expression compared with 64% (9/14) of infiltrating lobular carcinomas. LOH was detected in 46% (24/52) of infiltrating ductal carcinomas and 89% (8/9) of infiltrating lobular carcinomas. In the infiltrating lobular carcinomas, LOH was associated with complete loss of cell membrane expression of E-cadherin, although a cytoplasmic expression pattern was evident. In contrast, this association was not seen in the infiltrating ductal carcinomas. In a multivariate analysis, loss of E-cadherin expression was shown to be a significant independent risk factor for a poorer disease-free survival (P=0.019), in particular in the node-negative subset of patients (P=0.029). Significance was also approached for breast cancer corrected survival (P=0.056). We conclude that different mechanisms are involved in the altered E-cadherin expression seen in different subtypes of breast carcinomas. Furthermore, we implicate loss of E-cadherin, regardless of the genetic causes, as an independent prognostic marker for disease recurrence, especially in node-negative breast cancer patients, irrespective of the histological type.

Chromosome 8p alterations in sporadic and BRCA2 999del5 linked breast cancer

Chromosomal losses involving the short arm of chromosome 8 are frequent in a variety of tumour types, including breast cancer, suggesting the presence of one or more tumour suppressor genes in this region. In this study, we have used 11 microsatellite markers to analyse loss of heterozygosity (LOH) at chromosome 8p in 151 sporadic breast tumours and 50 tumours from subjects carrying the BRCA2 999del5 mutation. Fifty percent of sporadic tumours compared to 78% of BRCA2 linked tumours exhibit LOH at one or more markers at 8p showing that chromosome 8p alterations in breast tumours from BRCA2 999del5 carriers are more pronounced than in sporadic breast tumours. The pattern of LOH is different in the two groups and a higher proportion of BRCA2 tumours have LOH in a large region of chromosome 8p. In the total patient material, LOH of 8p is associated with LOH at other chromosome regions, for example, 1p, 3p, 6q, 7q, 9p, 11p, 13q, 17p, and 20q, but no association is found between LOH at 8p and chromosome regions 11q, 16q, 17q, and 18q. Furthermore, an association is detected between LOH at 8p and positive node status, large tumour size, aneuploidy, and high S phase fraction. Breast cancer patients with LOH at chromosome 8p have a worse prognosis than patients without this defect. Multivariate analysis suggests that LOH at 8p is an independent prognostic factor. We conclude that chromosome 8p carries a tumour suppressor gene or genes, the loss of which results in growth advantage of breast tumour cells, especially in carriers of the BRCA2 999del5 mutation.

Population studies and validation of paternity determinations by six microsatellite loci

A single locus system of 6 microsatellite markers was evaluated for paternity testing. A nonradioactive method based on peroxidase labeling of a DNA probe was used to estimate the allele frequency of markers D1S216, D3S1217, D7S480, D9S157, D13S153, and D16S422 by genotyping 1134-1698 chromosomes. The number of detected alleles were 22, 15, 23, 10, 16, and 19, respectively, and the allele frequency varied from 0.001 to 0.317. The genotype of 87 families, consisting of mother, father, and child was determined. The probability that a random individual will give a positive paternity was evaluated. We conclude that the markers can be reliably typed and give sufficient and reliable information for paternity testing.

Immature B cells in bone marrow express Fas/FasL

Negative selection is a process by which autoreactive lymphocytes are eliminated from the developing antigen receptor repertoire. The mechanisms regulating negative selection of immature B lymphocytes in the bone marrow are poorly elucidated. Human bone marrow cells were examined in order to investigate the presence of the members of the Fas (APO-1/CD95) system. Here we demonstrate the expression of Fas in immature B lymphocytes (CD10/CD19+/CD40+/sIg+), and the presence of Fas natural ligand (FasL) in CD19+ bone marrow cells. The observed expression of apoptosis-related molecules might indicate how negative selection of autoreactive B cells can occur in human bone marrow.

Human interdigitating dendritic cells induce isotype switching and IL-13-dependent IgM production in CD40-activated naive B cells

Interdigitating dendritic cells (IDC) represent a mature progeny of dendritic cells (DC) in vivo and are exhibiting a strong lymphocyte stimulatory potential. Because of the restricted localization to secondary lymphoid organs where decisive cellular interactions take place in the initial events of immunity, IDC regulatory function was addressed in relation to naive B cells. In this study, we demonstrate that human tonsillar IDC induce a dual response from CD40-activated IgD+/CD38- naive B lymphocytes. IDC direct naive B cells toward either isotype switching or an IL-13-dependent IgM secretion. IDC-dependent proliferation, isotype switching, and Ig production are all strictly mediated by soluble factors, suggesting that such skewing in B cell activation is the result of differential cytokine expression. Moreover, IDC-expressed IL-13 represents a novel source of a cytokine with recently established effects in Th2 induction as well as in immunological disorders resulting in allergic reactions.

The effect of mismatch repair deficiency on tumourigenesis; microsatellite instability affecting genes containing short repeated sequences

We have investigated microsatellite instability (MSI) in colorectal, gastric, endometrial and ovarian cancer as a result of mismatch repair (MMR) deficiency. We detected frameshift mutations in several genes that carry short repeated sequences and are important in cell fidelity and growth control; hMSH3, hMSH6, BAX, IGFIIR, TGFbetaIIR, E2F4 and BRCA2. Accumulation of mutations was heterogeneous and mainly restricted to tumours showing MSI at several loci (MSI-H). Both insertions and deletions were evident and occasional intratumour heterogeneity was evident with more than one different additional allele in the tumour. Most MSI-H tumours had acquired mutations in more than one gene and longer repeated sequences were more frequently targets for mutations. The TGFbetaIIR gene was mutated in 62%, the hMSH3 gene in 43%, the E2F4 gene in 35%, the hMSH6 in 32%, the BAX gene in 32%, the IGFIIR gene in 26%, and the BRCA2 gene in 2% of the MSI-H tumours. Homozygous mutations or mutation of both alleles were evident in all genes except BRCA2, in total 23/105 mutated cases, varying from 7% for BAX to 50% for E2F4. E2F4 mutations were exclusively found in colon tumours and E2F4 polymorphisms was found in 8% of cases. No difference in mutation prevalence was noted between cancer types apart from TGFbetaIIR mutations, which were frequently found in colon and gastric tumours but not in endometrial tumours, suggesting that endometrial tumours progress by a different route where TGFbetaIIR mutations are less favourable.

Chromosome alterations and E-cadherin gene mutations in human lobular breast cancer

We have studied a set of 40 human lobular breast cancers for loss of heterozygosity (LOH) at various chromosome locations and for mutations in the coding region plus flanking intron sequences of the E-cadherin gene. We found a high frequency of LOH (100%, 31/31) at 16q21-q22.1. A significantly higher level of LOH was detected in ductal breast tumours at chromosome arms 1p, 3p, 9p, 11q, 13q and 18q compared to lobular breast tumours. Furthermore, we found a significant association between LOH at 16q containing the E-cadherin locus and lobular histological type. Six different somatic mutations were detected in the E-cadherin gene, of which three were insertions, two deletions and one splice site mutation. Mutations were found in combination with LOH of the wild type E-cadherin locus and loss of or reduced E-cadherin expression detected by immunohistochemistry. The mutations described here have not previously been reported. We compared LOH at different chromosome regions with E-cadherin gene mutations and found a significant association between LOH at 13q and E-cadherin gene mutations. A significant association was also detected between LOH at 13q and LOH at 7q and 11q. Moreover, we found a significant association between LOH at 3p and high S phase, LOH at 9p and low ER and PgR content, LOH at 17p and aneuploidy. We conclude that LOH at 16q is the most frequent chromosome alteration and E-cadherin is a typical tumour suppressor gene in lobular breast cancer.

Molecular genetics of breast cancer progression

Somatic changes in the genome of breast cancer cells include amplifications, deletions and gene mutations. Several chromosome regions harboring known oncogenes are found amplified in breast tumors. Despite the high number of chromosome regions deleted in breast tumors the functional relationship to known genes at these locations and cancer growth is mainly undiscovered. Mutations in two tumor suppressor genes (TSG) have been described in a subset of breast carcinomas. These TSG are the TP53, encoding the p53 transcription factor, and the CDH1, encoding the cadherin cell adhesion molecule. Breast tumors of patients with a germ-line mutation in the BRCA1 or BRCA2 gene have an increase of additional genetic defects compared with sporadic breast tumors. This higher frequency of genetic aberrations could pinpoint genes that selectively promote tumor progression in individuals predisposed to breast cancer due to BRCA1 or BRCA2 germ-line mutations. Accumulation of somatic genetic changes during tumor progression may follow a specific and more aggressive pathway of chromosome damage in these individuals. Although the sequence of molecular events in the progression of breast tumor is poorly understood the detected genetic alterations fit the model of multistep carcinogenesis in both sporadic and hereditary breast cancer. This review will focus on the genetic lesions within the breast cancer cell.

The Brca1 and Brca2 proteins and tumor pathogenesis

Germline alterations of the BRCA1 or BRCA2 genes result in susceptibility to breast and ovarian cancer. Protein-protein interaction studies, transcription activity and mouse knockout experiments have suggested that the Brca1 and Brca2 proteins are of importance in DNA repair and maintenance of genome integrity, possibly due to the transactivation function of Brca1 or Brca2. Subsequently, tumors in individuals carrying germline mutation in either BRCA1 or BRCA2 gene show instability at chromosomal and gene level. Chromosomal and gene alterations are more pronounced in tumors from BRCA1 and BRCA2 mutation carriers than in sporadic tumors. Furthermore, BRCA1 and BRCA2 mutated breast tumors differ from sporadic tumors in respect to histological phenotype. Typically, a higher grade of malignancy is observed in familial tumors. This review summarizes the putative functions of the Brca1 and Brca2 proteins and pathogenesis in tumors of BRCA1 and BRCA2 mutation carriers.

Reduced Fhit expression in sporadic and BRCA2-linked breast carcinomas

Evidence for alteration of the FHIT gene in a significant fraction of breast carcinomas has been reported, in apparent concordance with loss of heterozygosity (LOH) at chromosome region 3p14.2 in breast cancer and benign proliferative breast disease. A significantly higher frequency of LOH at the FHIT locus was reported for BRCA2-/- tumors, possibly due to misrepaired double-strand breaks at this common fragile region. To determine whether such genomic alterations lead to Fhit inactivation, we have assessed the level of Fhit expression by immunohistochemical detection in sporadic tumors and cancers occurring in BRCA2 999del5 carriers. To determine whether Fhit inactivation may have prognostic significance, we have also assessed expression of breast cancer markers and clinical features in sporadic tumors relative to Fhit expression. Of 40 consecutive sporadic breast carcinomas studied for tumor markers, 50% showed reduced Fhit expression. In these sporadic cancers, loss of Fhit expression was not correlated significantly with the presence or absence of other tumor markers. In a study of 58 sporadic and 34 BRCA2 999del5 Icelandic invasive cancers, there was a significant association of LOH at 3p14.2 with reduced expression of Fhit (P = 0.001); also the lower expression of Fhit and higher LOH at 3p14.2 in BRCA2 999del5 tumors relative to sporadic cancers was significant (P = 0.002). Thus, genetic alteration at the fragile site within the FHIT gene leads to loss of Fhit protein in a significant fraction of sporadic breast cancers and a much larger fraction of familial breast cancers with an inherited BRCA2 mutation, consistent with the idea that loss of BRCA2 function affects stability of the FHIT/FRA3B locus.

Replication error in colorectal carcinoma: association with loss of heterozygosity at mismatch repair loci and clinicopathological variables

Instability of microsatellite DNA or replication error (RER) is characteristic of tumours caused by mismatch repair (MMR) deficiency. Germline mutations in MMR genes are associated with Hereditary non-polyposis colorectal carcinoma (HNPCC) and somatic mutations in these genes are also found in a substantial fraction of colorectal cancers (CRC). In this study we concurrently screened colorectal tumours for the RER phenotype and loss of heterozygosity (LOH) at MMR gene loci. The RER phenotype was evident in 47/197 (24%) tumours. RER was more commonly detected in young patients (< 50 years) and in tumours located in the proximal colon. RER was positively associated with LOH at the hMSH2/hMSH6 loci on chromosome 2p, where LOH was observed in 46% of the RER+ tumours. LOH at hMLH1 and hPMS1 loci was more frequent in the younger patients (< 50 years). RER was not associated with clinicopathological parameters, such as Duke's stage and tumour differentiation (grade). The RER phenotype was associated with better overall survival, but there was a trend towards significance when multivariate analysis was used. This indicates that loss of MMR genes generate a less aggressive phenotype, and raises the question about RER being a useful indicator of prognosis for CRC patients.

Co-ligation of CD44 on naive human tonsillar B cells induces progression towards a germinal center phenotype

The precise signaling pathways to induce a germinal center (GC) phenotype and somatic mutations in human B cells are presently not understood. Major phenotypical hallmarks of a human GC B cell are up-regulated expression of CD10 and CD95 together with a heterogeneous expression of CD77. Activation of resting human tonsillar B cells using anti-CD40 and anti-IgM antibodies normally only induces up-regulation of CD38 and CD71 but has no effect on the typical GC markers. However, we show here that an additional co-ligation of the glycoprotein CD44 on such tonsillar B cells up-regulated the typical human GC markers CD10, CD38, CD77 and CD95, and down-regulated CD24 and CD39 as well as induced progression towards apoptosis in these cells; all characteristics of GC B cells. These data indicate a functional role of CD44 during activation of human naive B lymphocytes and in the generation of GC B cells.

Loss of heterozygosity at chromosome 1p in different solid human tumours: association with survival

The distal half of chromosome 1p was analysed with 15 polymorphic microsatellite markers in 683 human solid tumours at different locations. Loss of heterozygosity (LOH) was observed at least at one site in 369 cases or 54% of the tumours. LOHs detected ranged from 30-64%, depending on tumour location. The major results regarding LOH at different tumour locations were as follows: stomach, 20/38 (53%); colon and rectum, 60/109 (55%); lung, 38/63 (60%); breast, 145/238 (61%); endometrium, 18/25 (72%); ovary, 17/31 (55%); testis, 11/30 (37%); kidney, 22/73 (30%); thyroid, 4/14 (29%); and sarcomas, 9/14 (64%). High percentages of LOH were seen in the 1p36.3, 1p36.1, 1p35-p34.3, 1p32 and 1p31 regions, suggesting the presence of tumour-suppressor genes. All these regions on chromosome 1p show high LOH in more than one tumour type. However, distinct patterns of LOH were detected at different tumour locations. There was a significant separation of survival curves, with and without LOH at chromosome 1p, in the breast cancer patients. Multivariate analysis showed that LOH at 1p in breast tumours is a better indicator for prognosis than the other variables tested in our model, including nodal metastasis.

Replication error in human breast cancer: comparison with clinical variables and family history of cancer

Replication errors (RER) at microsatellite repeats indicate genomic instability in hereditary nonpolyposis colorectal cancer (HNPCC) and in some sporadic cancers. We have studied genomic instability in 313 sporadic breast tumors and in 106 tumors from BRCA2, 999del5 carriers at 43 genomic loci on 13 chromosomes. RER was observed in 8/419 (1.9%) of the cases at one or more chromosomal loci. The frequencies of type I and type II RER were similar. The majority of RER+ tumors showed ER+, PgR+, high S-phase fraction, tumor size >2 cm and LOH at 2p, 2q and 3p. All 8 RER+ tumors were of the ductal histotype. The breast cancer cases with RER are not part of an HNPCC syndrome and a family history of colorectal cancer growth is not detected in relatives, with the exception of one case. However, four of the RER+ cases are from individuals carrying the BRCA2, 999del5 mutation. We conclude that RER is a rare somatic event during human breast carcinogenesis and may be associated with progression of breast carcinomas.

Mapping loss of heterozygosity at chromosome 13q: loss at 13q12-q13 is associated with breast tumour progression and poor prognosis

Several chromosome regions exhibit loss of heterozygosity (LOH) in human breast carcinoma and are thought to harbour tumour suppressor genes (TSG). At chromosome 13q, two TSGs have been identified, RB1 at 13q14 and BRCA2 at 13q12-q13. In this study, 139 sporadic breast tumours were analysed with 18 polymorphic microsatellite markers for detailed mapping of LOH at chromosome 13q and evaluation of an association with known progression factors. LOH with at least one marker was observed in 71 (51%) of the tumours analysed. The deletion mapping indicated three LOH target regions, 13q12-q13, 13q14 and 13q31-q34. LOH at chromosome 13q12-q13 was associated with low progesterone receptor content, a high S phase fraction and aneuploidy. Multivariate analysis adjusting for lymph node involvement and S phase fraction showed that patients with tumours exhibiting LOH at 13q12-q13 have a 3-4-fold increased risk of recurrence and death compared with other patients. Our results suggest there are at least three separate LOH target regions at chromosome 13q and inactivation of one or more genes at chromosome 13q12-q13 results in poor prognosis for breast cancer patients.

High incidence of loss of heterozygosity in breast tumors from carriers of the BRCA2 999del5 mutation

Germ-line mutation in the BRCA2 gene confers an increased risk of breast cancer. An elevation of additional genetic defects in tumors of patients with germ-line mutation in the BRCA2 gene compared with sporadic breast tumors has been reported. To evaluate the nature of the difference, we did detailed mapping of chromosomes 1p, 3p, 6q, 11, 13q, 16q, 17, and 20q, using microsatellite markers. We found that the frequency of loss of heterozygosity was similar at some chromosomal regions in the BRCA2 999del5 and sporadic tumors but significantly different at others. These others include chromosomal arms 3p, 6q, 11p, 11q, 13q, and 17p. Loss of heterozygosity mapping suggests that the same chromosome regions are involved in both tumor groups but at elevated frequencies in BRCA2 999del5 tumors. This higher frequency of genetic aberrations could pinpoint genes that selectively promote tumor progression in individuals predisposed to breast cancer due to the BRCA2 999del5 germ-line mutation. Accumulation of somatic genetic changes during tumor progression may follow a specific and more aggressive pathway of chromosome damage in these individuals.

High frequency of LOH at chromosome 18q in human breast cancer: association with high S-phase fraction and low progesterone receptor content

Human primary breast cancers were analysed for somatic loss of heterozygosity (LOH) at chromosome 18 with 15 polymorphic microsatellite markers. LOH was observed in 148 of the 228 cases analyzed, (65%). Three smallest common deletion regions (SCDR) were detected on the long arm of chromosome 18. The marker D18S51 at the region 18q22 showed the highest LOH (42%). Tumors with and without LOH at 18q were tested for association with clinico-pathological features of the tumors, such as estrogen and progesterone receptor content, age at diagnosis, tumor size, node status, histological type, S-phase fraction, DNA ploidy and LOH at other chromosomal regions. A significant association was found between LOH at 18q and high S-phase fraction (99.9% confidence interval) and low progesterone receptor content (99% confidence interval). Furthermore, an association was found between LOH at 18q and LOH at 1p, 7q, 9p, 13q and 17q. We conclude that there are three separate LOH target regions at chromosome 18q, and that inactivation of one or more genes at these regions might be important for human breast carcinogenesis.

High incidence of loss of heterozygosity at chromosome 17p13 in breast tumours from BRCA2 mutation carriers

Breast tumours from BRCA1 and BRCA2 mutation carriers are genetically instable and display specific patterns of chromosomal aberrations, suggestive of distinct genetic pathways in tumour progression. The frequency of abnormalities affecting chromosome 17p and the TP53 gene was determined in 27 breast tumours from 26 female patients carrying the Icelandic BRCA2 founder mutation (999del5). Loss of heterozygosity (LOH) was detected in 23 of the 27 tumours (85%). The majority of tumours manifesting LOH had lost a large region on 17p, although a more restricted loss, including the TP53 locus was seen in a few tumours. Positive p53 immunostaining was observed in 18 of 26 tumours (69%). However, mutations in the TP53 gene were detected in only three tumours (11%), including a missense (codon 139) and a nonsense mutation (codon 306) in two tumours with moderate p53 expression and a frameshift deletion (codon 182) in a tumour with no detectable p53 expression. Positive p53 immunostaining, mainly weak, was observed in 16 of the 24 tumours (66%) without TP53 mutation. The high frequency of LOH at chromosome 17p13 suggests that one or more genes from this region are involved in the development of BRCA2-induced breast cancer. The frequent finding of weak overexpression of, presumably wild type p53 protein, suggests an alternative mechanism of TP53 involvement specific to these tumours.

Chromosome imbalance at the 3p14 region in human breast tumours: high frequency in patients with inherited predisposition due to BRCA2

Our previous studies have indicated that genetic aberrations in the 3p14 region are more frequent in malignant tumours from hereditary breast cancer patients than sporadic breast cancers. The main purpose of this study was to test if BRCA2 susceptibility alleles contribute to imbalance in the 3p14 region. We mapped allelic imbalance at 3p14 in tumours from Icelandic sisters affected with breast cancer using a set of 10 microsatellite markers (tel-D3S1295-D3S1234-D3S1300-D3S1600-D3S1233+ ++-D3S1217-D3S1261-D3S1296-D3S1210- D3S1284-cen). The patients were of known carrier status with respect to the 999del5 mutation in BRCA2 which is the most common cause of hereditary breast cancer in Iceland. Of 103 patients, 32 in the group were mutation carriers. A high degree of imbalance was observed in tumours from BRCA2 mutation carriers, ranging from 44 to 88% for individual markers. This was significantly higher than the percentage of imbalance in tumours from non-carriers, where the frequency ranged from 25 to 43%. In both groups, we noted elevated 3p14 imbalance in patients with bilateral disease. Allelic imbalance was most commonly observed near the marker D3S1210 (3p14.1-p12) and the FHIT gene (3p21.1-p14.2) for both groups. We conclude that genomic aberrations in 3p14 are especially frequent in tumours with BRCA2 gene defects, and suggest that this is caused by regional loss of chromosome stability rather than selection.

Distinct somatic genetic changes associated with tumor progression in carriers of BRCA1 and BRCA2 germ-line mutations

BRCA1 and BRCA2 mutations confer increased risk for development of breast cancer, but a number of additional, currently largely unknown, somatic genetic defects must also accumulate in the breast epithelial cells before malignancy develops. To evaluate the nature of these additional somatic genetic defects, we performed a genome-wide survey by comparative genomic hybridization on breast cancers from 21 BRCA1 mutation carriers, 15 BRCA2 mutation carriers, and 55 unselected controls. The total number of genetic changes was almost two times higher in tumors from both BRCA1 and BRCA2 mutation carriers than in the control group. In BRCA1 tumors, losses of 5q (86%), 4q (81%), 4p (64%), 2q (40%), and 12q (40%) were significantly more common than in the control group (7-13%). BRCA2 tumors were characterized by a higher frequency of 13q (73%) and 6q (60%) losses and gains of 17q22-q24 (87%) and 20q13 (60%) as compared to the prevalence of these changes in the control group (12-18%). In conclusion, accumulation of somatic genetic changes during tumor progression may follow a unique pathway in individuals genetically predisposed to cancer, especially by the BRCA1 gene. Activation or loss of genes in the affected chromosomal regions may be selected for during tumor progression in cells lacking functional BRCA1 or BRCA2. Identification of such genes could provide targets for therapeutic intervention and early diagnosis.

Loss of heterozygosity at chromosome 7q in human breast cancer: association with clinical variables

In this study 238 human primary breast cancers were analysed with 9 polymorphic microsatellite markers specific to region 7q21-q35 on chromosome 7. LOH was observed at one or more marker in 82 cases or (34%). The deletions were evenly distributed throughout the region. Patients were divided into two groups according to whether LOH was observed in their tumours or not, and tested for association with overall survival, the clinicopathological features: steroid receptor content, tumour size, node status, DNA ploidy and S-phase fraction, and LOH at other chromosomal regions. An association was found between 7q LOH and high S-phase fraction. An association was found between LOH at 7q and LOH at 1p, 3p, 9p, 13q and 17q. These results suggest the location of a putative tumour suppressor gene at chromosome 7q21-q35 that, in combination with other deletions, might enhance tumour growth.

Loss of heterozygosity on chromosome arm 3p in nasopharyngeal carcinoma

We have examined 17 primary undifferentiated nasopharyngeal carcinoma biopsies for allelic loss on 3p, comparing the findings in tumors with those in normal lymphocyte DNA from the same patients. Ten polymorphic microsatellite markers were used between 3p13 and 3p26. Allelic loss was observed in 12 samples (70%). Two loci were most frequently affected: D3S1067 (3p21.1-14.3) in 60% and D3S1217 (3p14.2-14.1) in 58%. One tumor seemed to have a homozygous deletion at 3p26, detected by the D3S1297 marker. Analysis of the clinical data showed that an increased number of aberrations in 3p was correlated with more advanced tumor stages.

High prevalence of the 999del5 mutation in icelandic breast and ovarian cancer patients

Studies on Icelandic breast cancer families have shown that most of them segregate a 999del5 BRCA2 mutation. Here, we report the frequency of the 999del5 BRCA2 mutation in an Icelandic control population and four different groups of cancer patients diagnosed with (a) breast cancer; (b) ovarian cancer; (c) prostate cancer (patients younger than 65 years); and (d) other cancer types. The proportions of individuals carrying the mutation were 0.4% in the control population and in the patient groups 8.5%, 7.9%, 2.7%, and 1.0%, respectively. Our results indicate that BRCA2 confers a very high risk of breast cancer and is responsible for a substantial fraction of breast and ovarian cancer in Iceland, but only a small proportion of other cancers.

Frequent occurrence of BRCA2 linkage in Icelandic breast cancer families and segregation of a common BRCA2 haplotype

Cloning of a breast cancer-predisposing gene (BRCA2) on chromosome 13Q12-14 has been reported recently. We analyzed seven large Icelandic breast cancer families with markers from the BRCA2 region. Five families showed strong evidence of linkage. The maximum two-point LOD scores for the five BRCA2-linked families ranged from 1.06 to 3.19. Haplotype analyses revealed a region with identical allele sizes between the families, suggesting that they have inherited the mutation from a common ancestor. Cancer types other than breast cancer occur in individuals, segregating the affected haplotype within these families. This suggests that mutations in the gene may also confer some risk of other malignancies in both males and females.

Loss of heterozygosity on chromosome 9 in human breast cancer: association with clinical variables and genetic changes at other chromosome regions

Primary breast tumors were tested for loss of heterozygosity (LOH), on chromosome 9p with microsatellite markers restricted to a 28 cM region including the MTS1 gene. LOH was found with at least 1 marker in 38% of the 201 cases analyzed. A high frequency of deletions was detected at the 9p23-p21 region, indicating a tumor suppressor gene(s) important for breast cancer tumorigenesis. Tumors with and without LOH on 9p were compared with respect to clinico-pathological factors using chi 2 analysis. Tumors with 9p LOH were significantly associated with high S-phase status and aneuploidy, but not with type, node status, estrogen and progesterone receptor content or age of the patients at diagnosis. Survival analysis showed that LOH at 9p did not significantly affect the survival rate of breast cancer patients. Our results indicate that the aberrations on 9p detected in this study are not of independent prognostic value. A significant association was found between LOH at 9p and LOH at chromosomal arms 3p and 6q, which is an additional contribution toward understanding the genetic events in breast tumor pathogenesis.

Different tumor types from BRCA2 carriers show wild-type chromosome deletions on 13q12-q13

In this study we examined loss of heterozygosity (LOH) on chromosome 13q12-13 in 50 tumors from BRCA2 carriers in five families showing strong evidence of linkage to BRCA2. In addition to high frequency of LOH in female breast cancer, LOH was observed in tumors of the prostate, ovary, cervix, colon, male breast, and ureter. All detected losses involved the wild-type chromosome. These results suggest that BRCA2 is a tumor suppressor gene and may be involved in the tumorigenesis of several cancer types in addition to breast cancer.

Linkage analysis and allelic imbalance in human breast cancer kindreds using microsatellite markers from the short arm of chromosome 3

Eight Icelandic breast cancer kindreds were subjected to linkage analyses with respect to 28 microsatellite loci dispersed along the short arm of chromosome 3. Breast tumors derived from these kindreds were concurrently scored for allelic imbalance with ten of the markers. Linkage to most markers could be excluded on the basis of negative LOD scores and haplotype analyses, although some moderately positive LOD scores resulted. A high frequency of imbalance in the familial tumors was seen with two of the markers in comparison with results obtained from sporadic material. The highest frequency (68%) of imbalance was detected with the marker D3S1217, which is located on 3p14.2-p14.1. Imbalance at the D3S1211 locus, which is more telomeric (3p24.2-p22), was not significantly elevated in the familial tumors. We suggest that the genetic defect responsible for breast cancer susceptibility in these families either promotes instability in the 3p14.2-p14.1 region or enhances the selective advantage of such changes.

Loss of heterozygosity at chromosome 11 in breast cancer: association of prognostic factors with genetic alterations

We examined DNA from 116 female and four male breast cancer patients for loss of heterozygosity (LOH). DNA was analysed by polymerase chain reaction using ten microsatellite markers on chromosome 11. Three distinct regions of LOH were identified: 11p15.5, 11q13 and 11q22-qter with a LOH frequency of 19, 23 and 37-43% respectively. The marker D11S969 showing the highest frequency of LOH (43%) is located at the 11q24.1-q25 region. No previous molecular genetic studies have shown frequent LOH at the region telomeric to q23 on chromosome 11. Southern analysis revealed that LOH at 11q13 was due to amplification, whereas LOH at 11q22qter was due to deletion. LOH at 11p15.5 was associated with paucity of hormone receptor proteins, high S-phase and positive node status. An association was found between LOH at 11q13 and positive node status. LOH at the 11q22-qter region correlated with a high S-phase fraction. A significant association was found between LOH at 11p15 and chromosome regions 17q21 (the BRCA1 region) and 3p.

Stimulation of human peripheral lymphocytes via CD3 and soluble antigen abrogates specific antibody production by reducing memory B cell numbers

Human B cells are polyclonally activated in vitro by T cells stimulated with immobilized anti-CD3 monoclonal antibodies. We have analysed the effect of CD3 ligation on the production of antigen-specific antibodies, using peripheral blood lymphocytes from tetanus toxoid vaccinated blood donors. High levels of antigen-specific antibodies were obtained after stimulation with anti-CD3 antibodies for 7 days. Addition of soluble recall antigen did not affect the total amount of Ig produced, but dramatically decreased the antigen-specific response. The addition of IL-2, IL-4, and anti-CD40 or anti-CD28 antibodies or the removal of antigen did not restore the B cell response. Analysis using limiting dilution of B cells showed that the frequency of antigen-specific memory B cells decreased significantly in cultures stimulated with antigen. The antigen-specific B cell response could be completely restored only if the soluble antigen was cross-linked on the surface of the B cells. These results suggested that peripheral memory B cells were eliminated or anergized in the presence of soluble antigen.

Identification of a breast tumor with microsatellite instability in a potential carrier of the hereditary non-polyposis colon cancer trait

Allelic expansion at microsatellite loci in colorectal tumor DNA indicates a genomic instability caused by defects in DNA mismatch repair. This is observed in a high proportion of tumors from individuals affected by hereditary non-polyposis colorectal carcinoma, but to a lesser extent in sporadic colorectal tumors. In this study we screened 46 colorectal tumors for replication errors (RER). Tumors from six patients were found to be RER positive, two of which had a marked family history of colon cancer. In both cases the RER + phenotype was detected in colon tumors from other family members, suggesting a germline mutation in mismatch repair genes. Additionally, RER + phenotype, distinct from that of the colon and sporadic breast tumors, was found in malignant breast tissue from the mother of one proband.

Antigen-specific activation of B cells in vitro after recruitment of T cell help with superantigen

BACKGROUND

Human B cells can proliferate in vitro after stimulation with anti-Ig and via the CD40 molecule. Superantigens like SEA which bind to MHC class II antigens on, e.g. B cells can polyclonally activate T cells via interaction with their TcR. The activated T cell subsequently activates the B cells to proliferation and Ig-production.

OBJECTIVES

To investigate whether superantigen could be used to direct polyclonal T cell help to human B cells stimulated by antigen in a restricted manner resulting in production of antigen-specific antibodies in vitro.

STUDY DESIGN

Purified B cells were preincubated with the antigen in manners allowing crosslinking of surface-Ig. The antigen exposed B cells were then cultured together with autologous CD4+ helper T cells and in the presence of various concentrations of SEA. Antibody production was measured by ELISA after 7-12 days of culture.

RESULTS

Antigen-specific activation of B cells could be obtained after stimulating the B cells with antigen or anti-surface-Ig antibodies in the presence of T helper cells and SEA. The degree of B cell activation (proliferation as well as antibody production) depended on the dose of antigen as well as on the dose of SEA used. Increased crosslinking of surface-Ig on antigen-specific B cells enhanced Ig production. Specific antibody production to a secondary recall antigen (tetanus toxoid) and to primary antigens (DNP and GM2) were obtained. The specific B cell response was dependent on contact between T and B cells.

CONCLUSION

the results obtained demonstrate that the superantigen SEA can recruit T cell help to human B cells specifically stimulated by antigens, resulting in production of antigen reactive antibodies in vitro.

Chromosomal assignment of retinoic acid receptor (RAR) genes in the human, mouse, and rat genomes

The human genes encoding the alpha and beta forms of the retinoic acid receptor are known to be located on chromosomes 17 (band q21.1:RARA) and 3 (band p24:RARB). By in situ hybridization, we have now localized the gene for retinoic acid receptor gamma, RARG, on chromosome 12, band q13. We also mapped the three retinoic acid receptor genes in the mouse, by in situ hybridization, on chromosomes 11, band D (Rar-a); 14, band A (Rar-b); and 15, band F (Rar-g), respectively, and in the rat, using a panel of somatic cell hybrids that segregate rat chromosomes, on chromosomes 10 (RARA), 15 (RARB), and 7 (RARG), respectively. These assignments reveal a retention of tight linkage between RAR and HOX gene clusters. They also establish or confirm and extend the following homologies: (i) between human chromosome 17, mouse chromosome 11, and rat chromosome 10 (RARA); (ii) between human chromosome 3, mouse chromosome 14, and rat chromosome 15 (RARB); and (iii) between human chromosome 12, mouse chromosome 15, and rat chromosome 7 (RARG).