Adaptive evolution of the tumour suppressor BRCA1 in humans and chimpanzees. Australian Breast Cancer Family Study

Mutations in BRCA1 (ref. 1) confer an increased risk of female breast cancer. In a genome-wide scan of linkage disequilibrium (LD), a high level of LD was detected among microsatellite markers flanking BRCA1 (ref. 3), raising the prospect that positive natural selection may have acted on this gene. We have used the predictions of evolutionary genetic theory to investigate this further. Using phylogeny-based maximum likelihood analysis of the BRCA1 sequences from primates and other mammals, we found that the ratios of replacement to silent nucleotide substitutions on the human and chimpanzee lineages were not different from one another (P=0.8), were different from those of other primate lineages (P=0.004) and were greater than 1 (P=0.04). This is consistent with the historic occurrence of positive darwinian selection pressure on the BRCA1 protein in the human and chimpanzee lineages. Analysis of genetic variation in a sample of female Australians of Northern European origin showed evidence for Hardy-Weinberg (HW) disequilibrium at polymorphic sites in BRCA1, consistent with the possibility that natural selection is affecting genotype frequencies in modern Europeans. The clustering of between-species variation in the region of the gene encoding the RAD51-interaction domain of BRCA1 suggests the maintenance of genomic integrity as a possible target of selection.

HRAS1 rare minisatellite alleles and breast cancer in Australian women under age forty years

BACKGROUND

A recent meta-analysis of 23 studies supported the empirically derived hypothesis that women who lack one of the four common minisatellite alleles at the HRAS1 locus are at increased risk of breast cancer. These studies relied on visual sizing of alleles on electrophoretic gels and may have underreported rare alleles. We determined whether this hypothesis applied to early-onset breast cancer by using a new method to size minisatellite alleles.

METHODS

We conducted a population-based, case-control-family study of 249 Australian women under 40 years old at diagnosis of a first primary breast cancer and 234 randomly selected women, frequency matched for age. We sized HRAS1 minisatellite alleles with an Applied Biosystems model 373 automated DNA sequencer and GENESCAN(TM) software. All P values are two-sided.

RESULTS

We found no association of rare alleles with breast cancer, before or after adjustment for risk factors and irrespective of how their effects were modeled (crude odds ratio = 1.04; 95% confidence interval [CI] = 0.071-1.53; P =.8). The rare allele frequency was 0. 173 (95% CI = 0.149-0.197), three times the pooled estimate of 0.058 (95% CI = 0.050-0.066) from previous studies (P<.001), and was similar for case subjects, 0.177 (95% CI = 0.143-0.221), and control subjects, 0.169 (95% CI = 0.135-0.203) (P =.7).

CONCLUSION

There was no support for an association between rare HRAS1 alleles and the risk of early-onset breast cancer, despite 80% power to detect effects of the magnitude of those associations (1.7-fold) previously suggested.

IMPLICATIONS

The question of whether cancer risk is associated with rare minisatellite HRAS1 alleles needs to be revisited with the use of new methods that have a greater ability to distinguish rare alleles from similarly sized common alleles.

Population-based estimate of the average age-specific cumulative risk of breast cancer for a defined set of protein-truncating mutations in BRCA1 and BRCA2. Australian Breast Cancer Family Study

The average breast cancer risk for carriers of a germ-line mutation in BRCA1 or BRCA2 (penetrance) has been estimated from the multiple-case families collected by the Breast Cancer Linkage Consortium (BCLC) to be approximately 80% to age 70. However, women now being tested for these mutations do not necessarily have the intense family history of the BCLC families. Testing for protein-truncating mutations in exons 2, 11, and 20 of BRCA1 and exons 10 and 11 of BRCA2 was conducted in a population-based sample of 388 Australian women with breast cancer diagnosed before age 40. Onset of breast cancer was analyzed in the known and potential mutation-carrying first- and second-degree female relatives of cases found to carry a mutation. Of the 18 mutation-carrying cases (9 BRCA1 and 9 BRCA2), only 5 (1 BRCA1 and 4 BRCA2) had at least one affected relative, so family history of breast cancer was not a strong predictor of mutation status in this setting. The risk in mutation carriers was, on average, 9 times the population risk [95% confidence interval (CI), 4-23; P < 0.001]. Penetrance to age 70 was 40% (95% CI, 15-65%), about half that estimated from BCLC families. By extrapolation, approximately 6% (95% CI, 2-20%) of breast cancer before age 40 may be caused by protein-truncating mutations in BRCA1 or BRCA2. Breast cancer risk in BRCA1 or BRCA2 mutation carriers may be modified by other genetic or environmental factors. Genetic counselors may need to take into account the family history of the consultand.

Androgen receptor exon 1 CAG repeat length and breast cancer in women before age forty years

BACKGROUND

We conducted a population-based, case-control-family study to determine whether androgen receptor (AR) exon 1 polymorphic CAG repeat length (CAGn) was a risk factor for early-onset breast cancer in the Australian population.

METHODS

Case subjects under 40 years of age at diagnosis of a first primary breast cancer and age-matched control subjects were interviewed to assess family history and other risk factors. AR CAGn length was determined for 368 case subjects and 284 control subjects. Distributions in the two groups were compared by linear and logistic regression, allowing adjustment for measured risk factors. All statistical tests were two-tailed.

RESULTS

When analyzed as either a continuous or a dichotomous variable, there was no association between CAG, length and breast cancer risk, before or after adjustment for risk factors. Mean (95% confidence interval [CI]) CAGn lengths were 22.0 (21.8-22.2) for case subjects and 22.0 (21.7-22.3) for control subjects (P = .9). The frequency (95% CI) of alleles with 22 or more CAGn repeats was 0.531 (0.494-0.568) for case subjects and 0.507 (0.465-0.549) for control subjects (P = .4). After adjustment, the average effect on log OR (odds ratio) per allele was 0.16 (95% CI = -0.03 to 0.40; P = .2), and the effect of any allele was equivalent to an OR of 1.40 (95% CI = 0.94-2.09; P = .1). Stratification by family history also failed to reveal any association. Similar results were obtained when alleles were defined by other cutoff points.

CONCLUSION

We found no evidence for an association between AR exon 1 CAGn length and breast cancer risk in women under the age of 40, despite having 80% power to detect modest effects.

Distinct molecular pathogeneses of early-onset breast cancers in BRCA1 and BRCA2 mutation carriers: a population-based study

Breast cancers arising in women with and without a germline mutation in the BRCA1 or BRCA2 gene display different histological features, which suggests unique mechanisms of molecular pathogenesis: We used a molecular pathological analysis to define the genetic abnormalities relevant to these specific pathogeneses. Tumor material was studied from 40 women with breast cancer diagnosed before 40 years of age, sampled from a population-based study and stratified by BRCA1 and BRCA2 germline mutation status. Cases were not selected for family history or ethnic origin, and none were known to be genetically related. Thus, germline mutation itself is likely to impact on the molecular pathogenesis of these tumors, with no substantial influence due to modifying genetic or environmental factors. Breast cancers occurring in BRCA1 mutation carriers had significantly higher levels of p53 expression, including the preinvasive (carcinoma in situ) stage of disease, compared with cancers occurring in BRCA2 mutation carriers or women with no detectable germline mutation. These cancers also had a higher proliferation rate as measured by Ki-67 antibody. Expression of the prognostic factors c-erbB-2, cyclin D1, and estrogen receptor was significantly less common in BRCA1 mutation carriers. Lower levels of cyclin D1 were also found in cancers from BRCA2 mutation carriers compared with non-mutation carriers. Direct p53 mutation analysis revealed mutations in 18% of all of the early-onset breast cancers within the study and included rare insertion and deletional mutations in cancers from BRCA1 mutation carriers. Our data indicate that a BRCA1 breast cancer phenotype may be recognized by an exceptionally high proliferation rate and early and frequent p53 overexpression but infrequent selection for overexpression of several other prognostic factor proteins known to be involved in breast oncogenesis. In contrast, breast cancers arising in BRCA2 mutation carriers have a more heterogeneous phenotypic profile.

BRCA1 mutations and other sequence variants in a population-based sample of Australian women with breast cancer

The frequency, in women with breast cancer, of mutations and other variants in the susceptibility gene, BRCA1, was investigated using a population-based case-control-family study. Cases were women living in Melbourne or Sydney, Australia, with histologically confirmed, first primary, invasive breast cancer, diagnosed before the age of 40 years, recorded on the state Cancer Registries. Controls were women without breast cancer, frequency-matched for age, randomly selected from electoral rolls. Full manual sequencing of the coding region of BRCA1 was conducted in a randomly stratified sample of 91 cases; 47 with, and 44 without, a family history of breast cancer in a first- or second-degree relative. All detected variants were tested in a random sample of 67 controls. Three cases with a (protein-truncating) mutation were detected. Only one case had a family history; her mother had breast cancer, but did not carry the mutation. The proportion of Australian women with breast cancer before age 40 who carry a germline mutation in BRCA1 was estimated to be 3.8% (95% CI 0.3-12.6%). Seven rare variants were also detected, but for none was there evidence of a strong effect on breast cancer susceptibility. Therefore, on a population basis, rare variants are likely to contribute little to breast cancer incidence.

The histologic phenotypes of breast carcinoma occurring before age 40 years in women with and without BRCA1 or BRCA2 germline mutations: a population-based study

BACKGROUND

Women with breast carcinoma diagnosed before age 40 years have a greater prevalence of germline BRCA1 and BRCA2 mutations than women with breast carcinoma diagnosed at older ages. Several recognizable histologic characteristics have been identified in breast carcinoma from studies of BRCA1/2 mutation carriers who belong to multiple-case families. The authors attempted to determine whether breast carcinoma occurring before age 40 years in BRCA1 or BRCA2 mutation carriers who were not selected for family history could be distinguished histologically from one another and from breast carcinoma in women of a similar age without a germline BRCA1 or BRCA2 mutation.

METHODS

The study undertook a histologic assessment of breast carcinomas diagnosed before age 40 years identified from a population-based study.

RESULTS

Breast carcinoma in BRCA1 mutation carriers was associated with a distinct histologic appearance; these tumors were high grade, and had exceptionally high mean mitotic counts, a syncytial growth pattern, pushing margins, and confluent necrosis. Atypical medullary carcinoma was overrepresented in BRCA1 mutation carriers. All low grade tumors and tumors with low mitotic rates belonged to the group without BRCA1 or BRCA2 mutations. Pleomorphic lobular carcinomas and extensive intraduct carcinomas were more common in BRCA2 mutation carriers.

CONCLUSIONS

Breast carcinoma occurring in women with a germline BRCA1 or BRCA2 mutation have recognizable histologic phenotypes, which may be useful in identifying individuals more likely to carry germline mutations. Histologic examination of breast carcinoma should become an important part of the evaluation of women seeking genetic testing for germline mutations in these breast carcinoma susceptibility genes.

Expression of the P2Y6 purinergic receptor in human T cells infiltrating inflammatory bowel disease

The human P2Y6 receptor is a member of the G-protein-coupled P2Y purinergic receptor family that responds to extracellular uridine diphosphate (UDP). In previous work, we cloned the human P2Y6 receptor from an activated T-cell library, and others have shown that it is expressed as a 1.9-kb transcript in several lymphoid tissues. This suggests a role for P2Y6 in T-cell function. However, the precise cellular expression pattern and regulation of P2Y6 in immune cells have not yet been established. In this study, we have examined the expression of P2Y6 in a range of tissues containing leukocytes by a combination of in situ hybridization (ISH), Northern blot analysis, and RT-PCR. Northern hybridization revealed that activated peripheral T cells show increased levels of P2Y6 mRNA. Furthermore, RT-PCR analysis of CD4+ and CD8+ subsets illustrated strong expression in both activated CD4+ and CD8+ T cells. Stimulation of resting and activated T cells with the P2Y6 ligand UDP caused a rise in the intracellular free calcium concentration in only the activated subset, indicating the presence of functional receptor. By ISH, P2Y6 expression was detected in the T cells of the thymic medulla and spleen, whereas no signal was detected in the bone marrow, fetal liver, or lymph nodes. T cells are thought to play an important role in the pathogenesis of inflammatory bowel disease (IBD), and because a recent finding has suggested a role for extracellular nucleotides in mediating colonic epithelial cell damage in IBD, we speculated that the P2Y6 nucleotide receptor may be expressed in the T cells infiltrating IBD. ISH results reveal that P2Y6 is highly expressed in the T cells infiltrating active IBD, whereas P2Y6 expression was absent from the T cells of unaffected bowel. These results demonstrate expression and regulation of P2Y6 expression in T cells, and suggest a role for P2Y6 in the pathogenesis of IBD-mediated intestinal damage.

CFTR deltaF508 carrier status, risk of breast cancer before the age of 40 and histological grading in a population-based case-control study

There has been recent interest in the risk of various cancers in cystic fibrosis (CF) patients and carriers of cystic fibrosis transmembrane conductance regulator (CFTR) mutations. It has been proposed that a CFTR mutation may protect against breast cancer, based on evidence that elevated extracellular adenosine triphosphate (ATP) is known to inhibit breast cancer cell line growth and that CFTR pumps ATP out of epithelial cells. A CFTR mutation would therefore result in higher concentrations of serum ATP. A CFTR knockout mouse model had high serum concentrations of ATP and showed reduced breast tumour implantibility and decreased breast cancer growth rates. We have evaluated the relationship between the deltaF508 CFTR mutation and the risk of breast cancer before the age of 40. The deltaF508 CFTR mutation carrier rate in 272 cases (2.2%) was no different from the carrier rate observed in 171 controls (1.8%). If there was a protective effect resulting from the postulated elevation in serum ATP levels, tumours arising in deltaF508 CFTR carriers would have been expected to be generally less aggressive. When the histological features of the breast cancers with a deltaF508 CFTR mutation were reviewed and graded using a combined architectural and cytological grading system, all were found to be grade III, poorly differentiated tumours, contrary to the predictions. A combination of our data with other large population-based samples of cases and controls is required to resolve this issue.

Estrogen receptor polymorphism at codon 325 and risk of breast cancer in women before age forty

BACKGROUND

The estrogen receptor (ER) protein is believed to play a role in the development and progression of breast cancer. In a previously published U.S. clinic-based study, a polymorphism in the ER gene (codon 325, CCC --> CCG) was found to be more common in 34 case subjects with a family history of breast cancer than in 154 case subjects without such a history (mean allele frequencies +/- standard error = 0.28+/-0.05 versus 0.11+/-0.02; P<.001). To determine whether this polymorphism is a risk factor for early-onset breast cancer, we conducted a population-based, case-control-family study in Australia.

METHODS

Case subjects under the age of 40 years with a first primary breast cancer and control subjects, frequency-matched to the case subjects on the basis of age, and their relatives were interviewed to assess the family history of breast cancer. Polymorphism status of the ER gene was determined for 388 case subjects and 294 control subjects. All statistical tests were two-tailed.

RESULTS

There was no association between ER gene polymorphism status and breast cancer, before or after adjustment for risk factors. There was no difference in allele frequencies between case subjects and control subjects (0.232+/-0.015 versus 0.209+/-0.017; P = .4) or between women with and without a family history of breast cancer (P = .3), irrespective of case-control status. The findings were not altered when different definitions of family history of breast cancer were used and when allele frequencies were adjusted for residence and country of birth.

CONCLUSION

We found no evidence that the ER codon 325 polymorphism is associated with breast cancer before the age of 40 years or with a family history of breast cancer, despite ample power to detect effects half the magnitude of those previously reported.

Chromosomal localization of the human P2y6 purinoceptor gene and phylogenetic analysis of the P2y purinoceptor family

The G-protein-coupled P2Y purinoceptors mediate a variety of physiological effects in response to extracellular nucleotides. With the recent discovery of several new members from a variety of species, the P2Y purinoceptor family now encompasses types P2Y1 to P2Y6. By fluorescence in situ hybridization and utilization of the National Center for Biotechnology Information (NCBI) database, the human P2Y6 gene was localized to chromosome 11q13.5, between polymorphic markers D11S1314 and D11S916. NCBI database analysis of the remaining human P2Y purinoceptor genes revealed that P2Y2 and P2Y6 mapped to within less than 4 cM, and thus constitute the first described chromosomal clustering of this gene family. Phylogenetic analysis of the P2Y purinoceptor family demonstrated the presence of five evolutionary branches and suggests the occurrence of an ancient gene duplication event.

Coexistent T-cell lymphoblastic lymphoma and an atypical myeloproliferative disorder associated with t(8;13)(p21;q14)

This report describes a neoplasm exhibiting both lymphoid and myeloid differentiation associated with an acquired balanced translocation between chromosomes 8 and 13 occurring in a 10-year-old boy. Serial lymph node biopsies revealed the presence of both lymphoblastic lymphoma and an atypical myeloproliferative disorder within the same node. Immunophenotyping was consistent with the presence of an immature T-cell population within the nodal biopsy specimens. Cytogenetic analysis of the bone marrow and lymph node biopsy specimens revealed a unique translocation, t(8;13) (p21;q14). Molecular analysis revealed rearrangement of the immunoglobulin heavy chain gene and germline configuration of the T-cell receptor gene. The patient had a poor response to classical T-cell acute lymphocytic leukemia/lymphoma therapy and was changed to a myeloid leukemia protocol with good response. He underwent bone marrow transplantation but died soon after of overwhelming graft-versus-host disease. We found five similar cases in the literature, suggesting the existence of a subset of mixed lymphoid/myeloid disorders with 8p;13q translocations, in which the clinical picture is dictated by the myeloid element.

Spatiotemporally exact cDNA libraries from quail embryos: a resource for studying neural crest development and neurocristopathies

The neural crest is of fundamental importance in the developments of the head and peripheral nervous system, in the evolution of the vertebrates, and clinically because it gives rise to developmental abnormalities and neoplasms in humans. We have established a resource for studying the development of the neural crest by systematically constructing cDNA libraries from spatiotemporally exact neural crest and related cell populations. Neural crest populations were obtained from vagal and thoracic axial levels and from branchial arches, at premigratory and early and late migratory stages, at localization stages, and after differentiation into dorsal root ganglion cells, Schwann cells, sympathetic neurons, adrenal medullary cells, and melanocytes. Libraries were constructed using several methods developed to approach the issue of making representative libraries from small amounts of tissue. The fidelity and usefulness of the libraries were tested, and this revealed that they expressed a variety of sequences such as integrins, CAMs, growth factors and their receptors, protein-tyrosine kinases, and phosphatases. Differential display also revealed a unique combination of cDNA species. We then selected libraries spatiotemporally appropriate for epithelium-mesenchyme transformation and probed for TGF-beta-related sequences. As anticipated, we confirmed the presence of TGF-beta 2 and dorsalin-1 but could not detect TGF-beta 1. We also revealed new expression sites, defined by the origin of the libraries, of receptors known to be expressed elsewhere (Tsk 7l; TBRII). We anticipate that this collection of cDNA libraries will be of use in studying normal and abnormal neural crest development, by both homology searches and differential expression approaches, with spatiotemporal expression information being inherent in the initial screen.

Molecular cloning and sequencing of a novel human P2 nucleotide receptor

A novel human P2 nucleotide receptor has been cloned from a T-cell cDNA library. The predicted amino acid sequence shows characteristics of a G-protein-coupled receptor, and shares 88% homology with a recently characterised rat P2 nucleotide receptor sequence. Distinctive features include an extremely short cytoplasmic tail with only one putative protein kinase C phosphorylation site. Northern blot analysis revealed a 1.9 kb transcript expressed in the placenta.

EWS/FLI-1 fusion transcript detection and MIC2 immunohistochemical staining in the diagnosis of Ewing's sarcoma

Ewing's sarcoma (ES) and other primitive peripheral neuroectodermal tumors (pPNETs) can present a significant diagnostic problem, as they may morphologically resemble other small round cell tumors (SRCTs) of childhood. However, ES/pPNET is known to carry a characteristic t(11;22)(q24;q12), the detection of which may aid diagnosis. The recent identification of the EWS and FLI-1 genes flanking the translocation break point has enabled reverse transcriptase-polymerase chain reaction (RT-PCR) to be used to detect the putative chimeric transcription factor mRNA produced by the fusion gene. We have assessed the RT-PCR method of detection by examining 40 cases of ES for the presence of EWS/FLI-1 transcripts. Twenty-six (76%) of the 34 cases with intact mRNA yielded fusion transcripts. Four different transcript sizes were detected and two tumors contained two transcripts of different size. No transcripts were detected in a control group of non-ES/pPNET SRCTs. Eight cases with intact mRNA were transcript negative. The MIC2 cell surface antigen, which is reported to be present in over 95% of ES/pPNETs, was present in 32 of 33 tumors (97%), including all 24 EWS/FLI-1 transcript-positive cases examined. Hence MIC2 is a useful screen for ES, with RT-PCR detection of t(11;22) being the optimal method for confirming the diagnosis.

Primary cutaneous Ewing's sarcoma/peripheral primitive neuroectodermal tumors in childhood. A molecular, cytogenetic, and immunohistochemical study

Childhood cutaneous and subcutaneous malignancies are rare and include metastatic tumors of diverse histogenesis as well as primary lesions, such as sweat gland carcinomas. Some cutaneous malignancies exhibit a small round cell tumor morphology with few definitive differentiating features; they can thus pose a significant diagnostic problem. We describe two primary malignancies of the skin and superficial subcutis, which were originally diagnosed as sweat gland carcinomas on the basis of their morphological features. A cytogenetic analysis performed on one of these lesions showed the t(11;22)(q24;q12) rearrangement, believed to be unique to the Ewing's sarcoma/peripheral primitive neuroectodermal tumor (ES/pPNET) group of neoplasms. In view of this unexpected result, reverse transcriptase-polymerase chain reaction analysis was performed on both lesions and showed that they expressed EWS/FLI-1 fusion gene mRNA transcripts, the molecular equivalent of t(11;22)(q24;q12). The two tumors also had an immunohistochemical profile suggesting ES/pPNET, including strong expression of the MIC2 antigen. Both patients were treated with wide local excision, and one was given a course of chemotherapy. Neither patient showed evidence of tumor elsewhere after follow-up periods of 2 years and 16 years. These findings suggest that these tumors are indeed a form of primary ES/pPNET arising in the skin or superficial subcutis, which may be of low-grade malignancy and curable by local surgery.

Disseminated, multiclonal Epstein-Barr virus-associated lymphoproliferative disease in a patient with hematological and immunological anomalies. Molecular analysis correlates with morphological appearance

We report a case of a 21-year-old woman with hematopoietic, immunological, and congenital dysmorphic abnormalities, who died following rapidly progressive, disseminated Epstein-Barr virus (EBV)-associated lymphoproliferative disease (LPD). Polymerase chain reaction (PCR) amplification of formalin-fixed paraffin-embedded tissue showed differences in the clonality of each separate lymphoproliferative lesion examined, as determined by immunoglobulin heavy chain (IgH) gene rearrangement. PCR analysis also demonstrated that all lesions contained EBV genome. Since DNA had been extracted from paraffin blocks, a direct comparison of morphology and clonality could be made in each individual lesion. The evidence from this study indicates that the monoclonal tumors arose de novo in multiple sites and that the polyclonal background observed in some lesions reflected a substantial concomitant inflammatory response.

Regulation of membrane-associated tyrosine phosphatases in UMR 106.06 osteoblast-like cells

Protein tyrosine phosphatases play an important role in cell metabolism. Three distinct protein tyrosine phosphatase activities have been identified in an osteoblast-like cell line, UMR 106.06. These activities comprised two membrane-associated phosphatases and one cytosolic phosphatase of apparent molecular mass > 153 kDa, 80 kDa and 40 kDa respectively, estimated by gel filtration. On the basis of differences in apparent molecular mass, proteolytic-digestion profiles, substrate specificities and responses to a range of extracellular influences and inhibitor molecules, the two membrane-associated tyrosine phosphatases are distinct proteins. Tyrosine phosphatase activity in UMR 106.06 cells was sensitive to cell density. Cells at confluence contained membrane protein tyrosine phosphatase with specific activity 9-fold higher than cells at medium or low cell density. This elevation in membrane tyrosine phosphatase activity was due specifically to an increase in the high-molecular-mass enzyme. This phosphatase was also responsive to extracellular matrix components. This activity was elevated in cells grown on a collagen type-I matrix independently of cell density. Membrane and cytosolic protein tyrosine phosphatases were differentially regulated by a variety of agents including phorbol 12-myristate 13-acetate, parathyroid hormone, epidermal growth factor, okadaic acid and transforming growth factor beta. These observations suggest that regulatory influences control tyrosine phosphorylation in UMR 106.06 cells including cell-cell contact, cell-matrix contact and signal transduction involving tyrosine and serine/threonine phosphorylation events.

Lymphoproliferative disease of donor origin arising in patients after orthotopic liver transplantation

BACKGROUND

Lymphoproliferative disease is a well recognized complication of organ transplantation and in many cases is associated with Epstein-Barr virus (EBV) infection. It is widely though that posttransplantation lymphoproliferative disease (PTLPD) arises from recipient lymphoid cells. However, solid organ allografts are likely to include donor lymphoid tissue around or within the transplanted organ. Therefore, it is possible that transplanted donor lymphocytes may proliferate to form PTLPD:

METHODS

The genetic origin of tumor cells was determined by microsatellite DNA fingerprinting using the polymerase chain reaction (PCR). Their EBV association and clonality were established by PCR amplification of DNA extracted from formalin fixed, paraffin embedded tissue using primers to conserved regions of the EBV genome and the immunoglobulin heavy chain gene, respectively.

RESULTS

The authors have demonstrated two cases of lymphoproliferative disease that were derived from donor lymphocytes in orthotopic liver transplant recipients. In both cases, the proliferating cells were EBV DNA positive. Furthermore, the PTLPD was restricted to allograft tissue around the porta hepatis. However, the two cases differed in their clonal properties and response to treatment: one case was oligoclonal and regressed after antiviral therapy and a modest reduction of immunosuppression, whereas the other contained two clonal populations and was controlled only after treatment with antineoplastic chemotherapy.

CONCLUSION

This study has demonstrated two cases of PTLPD that were derived from donor lymphoid tissue. Although both cases were associated with EBV and remained localized to allograft tissue, their clonality and response to therapy differed.

Active tyrosine phosphatase in immunoprecipitates of multiple isoforms of Ly-5

Using tumour cell lines expressing specific isoforms of murine Ly-5 (molecular weights of 180,000, 200,000 and 240,000) we find that all forms of Ly-5 and immuno-affinity purified forms of Ly-5 contain tyrosyl phosphatase activity. These results demonstrate that these isoforms of Ly-5 belong to the same family of functional receptor-linked tyrosine phosphatases as the human leukocyte common antigen. CD45.