HER2 Equivocal (Score = 2+) Breast Carcinoma Cases Identified by Immunohistochemistry at a South African Hospital. What is the Impact of Fluorescent In Situ Hybridization Testing?

The American Society of Clinical Oncology and the College of American Pathologists (ASCO/CAP) guidelines are used for human epidermal growth factor receptor 2 (HER2) reporting in breast carcinoma. Cases that demonstrate weak to moderate complete membrane immunohistochemical staining in >10% of the tumor are scored as 2+ (equivocal). This study aimed to determine what proportion of HER2 immunohistochemistry (IHC) score = 2+ breast carcinomas were confirmed to be positive by HER2 fluorescent in situ hybridization (FISH). There were 241 HER2 IHC score = 2+ breast carcinomas included. Most (74.3%) carcinomas were estrogen and progesterone receptor-positive. Invasive breast carcinoma of no special type (89.2%) was the commonest histologic subtype. Most tumors were grade 2 (64.3%). As per the FISH report, at the time of diagnosis, 27 cases (11.2%) were HER2 FISH positive. All HER2 FISH equivocal cases and one FISH positive case assessed using the 2013 ASCO/CAP HER2 criteria were reclassified to HER2 FISH negative when the 2018 criteria were applied. There was a high level of agreement (κ = 0.979) between HER2 FISH results obtained using the 2013 and the 2018 criteria. This study provides insight into the frequency of HER2 FISH positivity (11.2%) among HER2 IHC score = 2+ breast carcinomas and the impact of modifications to the ASCO/CAP HER2 guidelines. Elimination of the HER2 FISH equivocal category by the 2018 guidelines has reduced the need for repeat testing and simplified clinical management. Reclassification of previous HER2 FISH positive to negative has resulted in some patients being ineligible for costly anti-HER therapy.

T-cell lymphoblastic leukaemia: The Johannesburg state-sector experience

Background: T-cell lymphoblastic leukaemia (T-ALL) is a malignancy of immature T-cells which is reported to comprise 7% – 23% of cases of lymphoblastic leukaemia (ALL), making up a larger proportion of adult ALL than childhood cases. It is characterised by an increased risk for early relapse but reportedly has superior outcomes as compared to B-cell ALL amongst adult patients. The frequency and clinical behaviour of T-ALL in Africa are unknown.Aim: This study aimed to assess the prevalence and selected clinicopathological features of T-ALL in Johannesburg, South Africa (SA).Setting: The Johannesburg state sector.Methods: All cases of ALL diagnosed by flow cytometry in the state-sector hospitals of Johannesburg over 42 months between 2016 and 2019 were identified and pertinent data recorded from the laboratory information system.Results: One hundred and eighty-one cases of ALL were identified, of which 59 (32.6%) were of T-cell lineage. The proportion of adult and paediatric ALL made up by T-ALL was similar (19/54 [35.2%] vs 40/127 [31.5%] respectively). Crude survival rates were very poor, with 80.0% having demised at the time of data collection. The mortality rate was overall significantly poorer amongst patients with T-ALL (80.0%) as compared to those with B-ALL (53.8%; p = 0.005) but was similarly poor in adults with B-ALL (83.3%) vs T-ALL (86.7%) (p = 0.53). The mortality rate did not differ between those with low-risk versus high-risk clinical features (77.8% vs 80.6%; p = 1.00).Conclusion: T-cell lymphoblastic leukaemia makes up a larger proportion of ALL in Johannesburg than is reported elsewhere, and it is a high-risk disease that is not well stratified by conventional risk factors.

Oral versus extra-oral plasmablastic lymphoma: A comparative analysis of 101 cases

AIMS

Originally described exclusively orally in HIV-infected patients, plasmablastic lymphoma (PBL) is increasingly described extra orally and in non-HIV-infected persons. The study comparatively analysed the clinico-pathologic features of oral PBLs (n = 55) to previously published extra-oral PBLs (n = 45 + 1) diagnosed over a seven-year period at the same institution in an HIV prevalent setting in South Africa in order to clarify any distinction between oral and extra-oral PBLs.

METHODS AND RESULTS

Tumours were assessed histologically and immunohistochemically with CD45 (LCA), CD3, CD20, CD79a, PAX5, CD138, MUM1, BLIMP1, VS38c, Ki-67, BCL6 and CD10 using standard protocols. Age ranged from 22 to 76 years (oral) and 9 and 59 years (extra-oral). Most PBL patients were HIV positive [oral (84%); extra-oral (65%)]. Male:female ratio was 2.7:1 for oral and 1.4:1 for extra-oral PBLs. Favoured oral and extra-oral sites were the maxilla and anus. PBLs displayed an indistinguishable immunohistochemical profile with unusually high CD45 expression (oral: 98%, extra-oral: 84%). EBV assessed by chromogenic in situ hybridisation (ISH) showed positivity in all oral PBLs and 95% extra-oral PBLs. MYC rearrangements (fluorescence ISH MYC break-apart probe) were similar in all the PBLs.

CONCLUSIONS

Extra-oral PBL is identical to its oral counterpart in gender and age distribution, HIV status, morphological appearances, immunophenotypic profile and EBV association. PBL should be regarded as the same tumour irrespective of oral or extra-oral site of origin.

Processing and Analysis of Tissue Samples from Esophageal Cancer Patients in an African Setting

Although infectious diseases continue to present a major health care problem in Africa, the incidence of cancer is increasing rapidly on the African continent and this merits an increased investment in cancer research in low to medium resource settings. Esophageal squamous cell carcinoma (ESCC) has a high incidence in Eastern and Southern Africa, with late clinical presentation and a very poor prognosis. There is limited research on the molecular pathology of this cancer in Africa, partly as a result of a lack of infrastructure for biobanking and sample processing in many African countries. The aim of this study was to establish a practical and robust workflow to collect, store, and process esophageal cancer samples such that both the tissue architecture and quality of the samples would be preserved and suitable for future genomic research. We developed a workflow that allows storage of fresh biopsy tissue in sterile Eppendorf tubes containing RNAlater, an efficient RNAse inhibitor. We collected 142 ESCC biopsy samples and showed that storage in RNAlater for up to 18 months did not alter tissue morphology, thus allowing histologic assessment by experienced pathologists and determination of tumor content in each biopsied sample. DNA and RNA extracted from tissue samples was assessed for purity, molecular size, and yield. The quantity and quality of nucleic acids obtained were suitable for genomic applications, and whole-exome sequencing of DNA from tumor tissues produced sequence data with a high proportion of both usable reads and correct base calling. We conclude that this workflow may be applicable to a wide range of malignancies for future genomic research in low-resource settings.

MYC status in HIV-associated plasmablastic lymphoma: dual-colour CISH, FISH and immunohistochemistry

AIMS

We utilised chromogenic and fluorescence in-situ hybridisation (CISH and FISH) to evaluate MYC gene copy numbers and rearrangements within HIV-associated plasmablastic lymphomas (PBLs). Thereafter, clinicopathological features were explored retrospectively.

METHODS AND RESULTS

Sixty-seven (n = 67) patients were included and the HIV seropositive status was confirmed in 98% (63 of 64) with a median viral load of 55 587 (IQR 273 582) copies/ml and median CD4 count of 170 (IQR 249) cells/µl. The mean age was 41 ± 10.1 years and females comprised 54%. PBL was documented predominantly at extra-oronasal topographic regions. Starry-sky (SS) appearance was evident in 33% in association with monomorphic morphology (P-value 0.02). c-MYC protein was expressed in 81% and latent EBV infection was detected in 90%. EBER ISH-positive status and MYC rearrangement occurred in 67% of HIV PBL. MYC aberrations included MYC rearrangement (70%), low-level increase in MYC gene copy numbers (43%), concurrent MYC rearrangement and increased MYC gene copy numbers (49%) as well as low-level chromosome 8 polysomy (6%). MYC aberrations in HIV PBLs were significantly associated with SS appearance (P -0.01), monomorphic morphology (P - 0.03), c-MYC protein expression ≥40% (P - 0.03) and mortality (P - 0.03). There was advanced stage (Ann Arbor III/IV) at presentation (77%) and the median overall survival for HIV PBL was 75 days (95% CI 14-136).

CONCLUSION

Majority of the HIV-associated PBL tumours harbour MYC aberrations. Due to the persistently inferior survival outcome of HIV-associated PBL in the era of antiviral treatment, targeted and/or intensified therapy of oncogenic MYC may need to be explored in future.

Genomic Characterization of HIV-Associated Plasmablastic Lymphoma Identifies Pervasive Mutations in the JAK–STAT Pathway

Plasmablastic lymphoma (PBL) is an aggressive B-cell non-Hodgkin lymphoma associated with immunodeficiency in the context of Human Immunodeficiency Virus (HIV) infection or iatrogenic immunosuppression. While a rare disease in general, the incidence is dramatically increased in regions of the world with high HIV prevalence. The molecular pathogenesis of this disease is poorly characterized. Here, we defined the genomic features of PBL in a cohort of 110 patients from South Africa (15 by whole exome sequencing and 95 by deep targeted sequencing). We identified recurrent mutations in genes of the JAK-STAT signaling pathway, including STAT3 (42%), JAK1 (14%) and SOCS1 (10%), leading to its constitutive activation. Moreover, 24% of cases harbored gain-of-function mutations in RAS family members (NRAS and KRAS). Comparative analysis with other B-cell malignancies uncovered PBL-specific somatic mutations and transcriptional programs. We also found recurrent copy number gains encompassing the CD44 gene (37%), which encodes for a cell surface receptor involved in lymphocyte activation and homing, and was found expressed at high levels in all tested cases, independent of genetic alterations. These findings have implications for the understanding of the pathogenesis of this disease and the development of personalized medicine approaches.

Landscape of copy number aberrations in esophageal squamous cell carcinoma from a high endemic region of South Africa

Background

Esophageal squamous cell carcinoma (ESCC) is an aggressive cancer with one of the highest world incidences in the Eastern Cape region of South Africa. Several genome wide studies have been performed on ESCC cohorts from Asian countries, North America, Malawi and other parts of the world but none have been conducted on ESCC tumors from South Africa to date, where the molecular pathology and etiology of this disease remains unclear. We report here tumor associated copy number changes observed in 51 ESCC patients’ samples from the Eastern Cape province of South Africa.

Methods

We extracted tumor DNA from 51 archived ESCC specimens and interrogated tumor associated DNA copy number changes using Affymetrix® 500 K SNP array technology. The Genomic Identification of Significant Targets in Cancer (GISTIC 2.0) algorithm was applied to identify significant focal regions of gains and losses. Gains of the top recurrent cancer genes were validated by fluorescence in situ hybridization and their protein expression assessed by immunohistochemistry.

Results

Twenty-three significant focal gains were identified across samples. Gains involving the CCND1, MYC, EGFR and JAG1 loci recapitulated those described in studies on Asian and Malawian cohorts. The two most significant gains involved the chromosomal sub-bands 3q28, encompassing the TPRG1 gene and 11q13.3 including the CTTN, PPFIA1and SHANK2 genes. There was no significant homozygous loss and the most recurrent hemizygous deletion involved the B3GAT1 gene on chromosome 11q25. Focal gains on 11q13.3 in 37% of cases (19/51), consistently involved CTTN and SHANK2 genes. Twelve of these cases (23,5%), had a broader region of gain that also included the CCND1, FGF19, FGF4 and FGF3 genes. SHANK2 and CTTN are co-amplified in several cancers, these proteins interact functionally together and are involved in cell motility. Immunohistochemistry confirmed both Shank2 (79%) and cortactin (69%) protein overexpression in samples with gains of these genes. In contrast, cyclin D1 (65%) was moderately expressed in samples with CCND1 DNA gain.

Conclusions

This study reports copy number changes in a South African ESCC cohort and highlights similarities and differences with cohorts from Asia and Malawi. Our results strongly suggest a role for CTTN and SHANK2 in the pathogenesis of ESCC in South Africa.

Extraoral plasmablastic lymphomas in a high human immunodeficiency virus endemic area

AIMS

Plasmablastic lymphoma (PBL) occurs mainly in immunocompromised individuals, usually secondary to human immunodeficiency virus (HIV) infection. It classically occurs intraorally, but has been described in extraoral locations. The aim of this study was to define the immunophenotype and Epstein-Barr virus (EBV) status in a large single-centre cohort of extraoral PBL (EPBL) in South Africa, a high-prevalence HIV setting.

METHODS AND RESULTS

This retrospective study of 45 EPBLs included patients' age, gender, race, HIV status, and site. Cases were reviewed histologically, and classified morphologically as pure plasmablastic or plasmablastic with plasmacytic differentiation, and assessed immunohistochemically with antibodies against CD45, CD20, CD79a, PAX5, CD138, MUM1/IRF4, BLIMP1, VS38c, Ki67, bcl-6, CD10, cyclin D1, and human herpesvirus-8, by the use of standard automated procedures. EBV was assessed by the use of chromogenic in-situ hybridisation. Tumours were assessed with a fluorescence in-situ hybridisation (FISH) MYC break-apart probe. Twenty-seven PBLs showed pure plasmablastic morphology, and 18 showed plasmacytic differentiation. The male/female ratio was 1.5:1. The anus was the favoured extraoral site (31.1%), followed by lymph nodes (15.6%). All 29 patients with known HIV status were HIV-positive. The immunohistochemical profile recapitulated that reported for oral PBLs and EPBLs in HIV-positive and HIV-negative patients. EBV was positive in 92.5% of PBLs. FISH analysis showed MYC rearrangement in 48% of cases.

CONCLUSION

This study showed a strong association of EPBLs with HIV and EBV infection, similarly to the previously described oral PBL. The strong EBV association together with other clinicopathological parameters and an immunohistochemical profile that includes CD45, CD20, MUM1/IRF4, CD138 and Ki67 may be used in distinguishing PBL from diffuse large B-cell lymphoma and plasma cell myeloma.

Treatment Outcomes in CML Patients Treated With Tyrosine Kinase Inhibitors at a Tertiary Teaching Hospital in South Africa

BACKGROUND

Chronic myeloid leukemia (CML) has become one of the most treatable hematologic neoplasms since the advent of the tyrosine kinase inhibitors (TKIs), but it was not known if similar treatment outcomes could be achieved in a resource-limited country. We tested the hypothesis that, despite challenges to access to second-generation TKIs, excellent responses could be replicated in the setting of limited resources.

PATIENTS AND METHODS

Records of 58 patients with newly diagnosed CML in the chronic phase treated with TKIs at a tertiary teaching hospital in Cape Town, South Africa between 2003 and 2012 were reviewed and assessed according to European LeukemiaNet (ELN) criteria.

RESULTS

After a median follow-up of 60.5 months, progression-free survival at 60 and 96 months was 79.98% and 68.4%, respectively. Overall survival at 60 and 96 months was 92.9% and 83.6%, respectively. Progression to blast phase at 60 months was associated with poorer survival (P = .0002) but progression to accelerated phase was not (P = .1456). Attainment of a complete cytogenetic response at 12 months (P = .28) or major molecular response at 18 months (P = .268) did not have prognostic significance.

CONCLUSION

Despite delays in achievement of the target responses defined according to ELN criteria, the use of imatinib mesylate as a first-line treatment can still result in treatment outcomes comparable with those in developed countries. These data suggest opportunities for improvement and success might be even greater with uninterrupted access to second-generation or newer TKIs.

Hepatosplenic T-cell lymphoma: A case series

Hepatosplenic T-cell lymphoma (HSTCL) is a rare type of Non-Hodgkin Lymphoma (NHL), grouped under the mature or peripheral T-cell lymphomas. It is characterised by extranodal infiltration and proliferation of malignant T-cells within the sinusoids of the liver, sinuses and red pulp of the spleen, and the bone marrow. The tumour cells express CD2 and CD3, but are CD4, CD5 and CD8 negative and express a clonally restricted gamma-delta (or less commonly alpha-beta) T-cell receptor. The disease has an aggressive clinical course associated with a poor prognosis. We highlight and report three patients from South Africa with HSTCL, all of whom had hepatosplenomegaly and cytopaenias, and despite being HIV seronegative and immunocompetent, had a poor outcome, with a mean survival of 7.5 months in the two evaluable patients. This rare entity has not previously been reported from South Africa and as yet needs to be adequately characterised in a population where lymphoma is the most common haematological malignancy in adults, and where approximately two thirds of the adult lymphoma population are HIV seropositive.

Challenges in lymphoma diagnosis in HIV positive patients in the South African setting

An increase in high grade B-cell lymphomas has been noted in HIV infection. Sub-Saharan Africa is the epicentre of the epidemic and in Gauteng, South Africa >90% of patients with high grade lymphoma tested positive for HIV infection. The diagnosis of lymphoma may be challenging in HIV because of reactive conditions which mimic lymphomas, the atypical clinical presentation and the atypical histological findings. The WHO classification divides lymphomas into discrete categories. Despite this, tumours in HIV positive patients commonly show atypical morphological, immunophenotypic, molecular and cytogenetic features, making exact classification difficult. This has lead to an increase in the diagnosis of the highly aggressive B-cell lymphoma, unclassifiable with features intermediate between DLBCL and BL. It appears likely that HIV-associated lymphomas represent a continuum of disease.

Molecular characterisation of gastrointestinal stromal tumours in a South African population

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the digestive tract. Pathogenesis is linked to activating mutations identified in two proto-oncogenes, v-kit Hardy/Zuckerman 4 feline sarcoma viral oncogene homologue KIT (KIT) and the platelet-derived growth factor α (PDGFRα). In addition, these mutations affect response to treatment with tyrosine kinase inhibitors. In the present study, we report on the molecular characterisation of GISTs in the South African population. Tumour DNA was extracted from 46 GIST samples, followed by cycle sequencing of KIT exons 11, 13 and 17 and PDGFRα exons 12, 14 and 18. Fragment length analysis was used to detect a 6-bp duplication in KIT exon 9. Wild-type duplications were analysed further by PCR and sequencing of additional KIT and PDGFRα exons was performed. Overall, 78.3% of the samples had a mutation in KIT or PDGFRα. Of these, mutations were detected in KIT exon 11 (88.9%), PDGFRα exon 18 (8.3%) and KIT exon 9 (2.8%). Mutations varied from simple substitutions and duplications to large deletions (some with nucleotide insertions) resulting in missense mutations. In addition, seven single nucleotide polymorphisms were detected in 17 patients, one of which appears novel. The incidence of mutations in KIT exon 11 and PDGFRα exon 18 is consistent with the literature, however, the low incidence of KIT exon 9 mutations detected was unexpected. In contrast to previous western and Asian studies, this mutation appears to be rare in the South African population. The present study contributes to the molecular understanding of GISTs in the South African population.

Recommendations for the management of adult chronic myeloid leukaemia in South Africa

INTRODUCTION

Chronic myeloid leukaemia (CML) is a chronic myeloproliferative disorder characterised by a chromosomal translocation between the long arms of chromosomes 9 and 22 [corrected] resulting in the formation of the BCR-ABL fusion gene. The management of CML has undergone major changes over the past decade. Novel treatment approaches have had a dramatic impact on patient outcomes and survival. Nevertheless, these outcomes can only be achieved in the context of expert management, careful monitoring of disease response, appropriate management of adverse events and timeous adjustments to therapy when responses are not achieved within stated time-frames.

AIM

With the advent of novel treatments providing molecular responses, both the monitoring and management of CML have become more complicated. The aim of these recommendations was to provide a pragmatic yet comprehensive roadmap to negotiate these complexities.

METHODS

Recommendations were developed based on local expert opinion from both the academic and private medical care arenas after careful review of the relevant literature and taking into account the most widely used international guidelines. About five meetings were held at which these recommendations were discussed and debated in detail.

RESULTS

A comprehensive set of recommendations was compiled with an emphasis on diagnosis, investigation, treatment and monitoring of disease. Careful attention was given to circumstances unique to South Africa, funding constraints, availability and access to laboratory resources, as well as the effects of concurrent HIV infection.

CONCLUSION

Most patients with CML can live a reasonably normal life if their disease is appropriately managed. These recommendations should be of value to all specialists involved in the treatment of haematological disorders.

Dominant genetic aberrations and coexistent EBV infection in HIV-related oral plasmablastic lymphomas

We present common cytogenetic features in the largest cohort of plasmablastic lymphoma (PBL) of the oral cavity published to date. This cohort included 45 patients, 32 of whom had a known HIV status, of which 31 were HIV positive. Ninety eight per cent of all PBL cases were known to be EBV positive. In line with previous studies, we found that rearrangements of the MYC gene was the most common genetic abnormality seen in 60% of cases with the immunoglobulin heavy chain (IGH) locus as a partner in 51% of cases. Additional complex genetic aberrations were frequent, in particular, an increased copy number of the CCND1 gene was seen in 41% of cases with true amplification of CCND1 in 15% of cases. Aneuploidy was also observed for the BCL6 gene in 28% of cases. Interestingly, rearrangements of both IGH genes were detected in 16% of cases with t(14;18) and t(11;14) respectively involved in conjunction with a t(8;14) in two cases. These bi-allelic IGH rearrangements have not been described before in oral PBL. Our results reinforce the notion that EBV infection and MYC rearrangements are important events in the pathogenesis of oral PBL. The genetic diversity and complexity observed in these cases, underlines the importance to genetically characterise PBL patients at presentation as this may inform the choice of more effective treatment modalities.

Genomic imbalances in esophageal carcinoma cell lines involve Wnt pathway genes

AIM: To identify molecular markers shared across South African esophageal squamous cell carcinoma (ESCC) cell lines using cytogenetics, fluorescence in situ hybridization (FISH) and single nucleotide polymorphism (SNP) array copy number analysis.

METHODS: We used conventional cytogenetics, FISH, and multicolor FISH to characterize the chromosomal rearrangements of five ESCC cell lines established in South Africa. The whole genome copy number profile was established from 250K SNP arrays, and data was analyzed with the CNAT 4.0 and GISTIC software.

RESULTS: We detected common translocation breakpoints involving chromosomes 1p11-12 and 3p11.2, the latter correlated with the deletion, or interruption of the EPHA3 gene. The most significant amplifications involved the following chromosomal regions and genes: 11q13.3 (CCND1, FGF3, FGF4, FGF19, MYEOV), 8q24.21(C-MYC, FAM84B), 11q22.1-q22.3 (BIRC2, BIRC3), 5p15.2 (CTNND2), 3q11.2-q12.2 (MINA) and 18p11.32 (TYMS, YES1). The significant deletions included 1p31.2-p31.1 (CTH, GADD45α, DIRAS3), 2q22.1 (LRP1B), 3p12.1-p14.2 (FHIT), 4q22.1-q32.1 (CASP6, SMAD1), 8p23.2-q11.1 (BNIP3L) and 18q21.1-q21.2 (SMAD4, DCC). The 3p11.2 translocation breakpoint was shared across four cell lines, supporting a role for genes involved at this site, in particular, the EPHA3 gene which has previously been reported to be deleted in ESCC.

CONCLUSION: The finding that a significant number of genes that were amplified (FGF3, FGF4, FGF19, CCND1 and C-MYC) or deleted (SFRP2 gene) are involved in the Wnt and fibroblast growth factor signaling pathways, suggests that these pathways may be activated in these cell lines.

Chromosomal radiosensitivity of HIV positive individuals

PURPOSE

Radiosensitivity in relation to the human immunodeficiency virus (HIV) status is important in South Africa as the prevalence of HIV infections is high. In this study the in vitro chromosomal radiosensitivity of HIV positive individuals was investigated and compared with that of HIV negative individuals.

MATERIALS AND METHODS

Blood samples from 59 HIV positive and 39 HIV negative individuals were exposed in vitro to doses of 6MV X-rays ranging from 1-4 Gy. Chromosomal radiosensitivity was assessed with the micronucleus assay. Micronuclei are a measure of chromosomal damage and were quantified in at least 500 binucleated lymphoblasts (BN) per sample. Un-irradiated control samples from each donor were also analysed.

RESULTS

In 47% of HIV positive individuals difficulties with cell stimulation by adding phytohaemagglutinin (PHA) to blood cultures were noticed which resulted in insufficient yield of BN for microscopic analysis. Micronuclei frequencies were consistently higher in irradiated lymphocytes obtained from HIV positive individuals compared to that observed in cells from HIV negative donors. Data for both groups were fitted to the linear-quadratic equation Y = alphaD + betaD(2) where Y is the number of micronuclei in 500 binucleated cells and D is the dose in Gy. The fitted parameters for respectively HIV positive and HIV negative lymphocytes are alpha = 80.17 Gy(-1), beta = 14 Gy(-2) and alpha = 54.5 Gy(-1), beta = 16.2 Gy(-2). The confidence ellipses of these parameters are separated indicating that the increase in radiosensitivity is statistically significant.

CONCLUSION

T-lymphocytes of HIV infected individuals were considerably more sensitive to X-rays compared to that of HIV negative donors. This may have implications for normal tissue tolerance during radiotherapy as well as for the radiological health of radiation workers.

A novel approach to simultaneously scan genes at fragile sites

BACKGROUND

Fragile sites are regions of the genome sensitive to replication stress and to exposure to environmental carcinogens. The two most commonly expressed fragile sites FRA3B and FRA16D host the histidine triad (FHIT) and WW domain containing oxidoreductase (WWOX) genes respectively. There is growing evidence that both genes contribute to cancer development and they are frequently altered by allelic and homozygous deletions in a variety of tumors. Their status is linked to prognosis in several malignancies and they are thought to be involved in early tumorigenesis. The loci for FHIT and WWOX both span over a megabase but the genes encode for small transcripts. Thus the screening of intragenic deletion can be difficult and has relied on loss of heterozygosity LOH assays, or genomic arrays.

METHODS

Multiplex ligation dependent probe amplification MLPA, allows for the detection of deletions/duplications and relative quantification of up to 40 specific probes in a single assay. A FHIT/WWOX MLPA assay was designed, applied and validated in five esophageal squamous cell carcinoma ESCC, cell lines established in South Africa where this cancer is of high prevalence. Sixteen probes covered all FHIT exons and 7 probes covered WWOX.

RESULTS

Both homozygous and hemizygous deletions were detected in FHIT, in four of the cell lines with a preferential deletion of exons 5 and 4. Chromosome 3 short arm was present in normal copy number indicating that deletions were site specific. In contrast WWOX was not altered in any cell lines. RT-PCR expression pattern paralleled the pattern of deletions. Ten primary ESCC tumor specimens were subsequently screened with this assay. FHIT exon deletions were found in four of them.

CONCLUSION

This method offers an alternative to loss of heterozygosity studies. Simultaneous scanning of FHIT and WWOX exons in the context of early tumorigenesis and tumor progression, may help clarify the mechanistic events related to cancer development which are not revealed by immuno histochemistry assays. The presence of site specific deletions of FHIT in these cell lines and primary tumors support its possible role in South African ESCC and justifies a wider screening.

Granulocytic sarcoma in children with acute myeloblastic leukemia and t(8;21)

BACKGROUND

Granulocytic sarcomas (GS) have been associated with t(8;21). The prognosis of patients with GS is generally regarded as being less favorable than of patients with acute myeloblastic leukemia (AML). GS occurs relatively commonly in Africa and has been reported to affect 10-25% of black children presenting with AML. We sought to establish the incidence of GS in our pediatric population, to determine whether an association with t(8;21) existed, and to report on the outcome of these cases in a single series.

PROCEDURE

The records of consecutive pediatric patients treated for de novo AML in Johannesburg between January 1985-December 1995 were reviewed. Fifteen cases of GS among a total of 88 cases of AML presented to the Paediatric Haematology/Oncology Clinics of the Johannesburg and Baragwanath Hospitals. Fourteen (93%) of these patients were black male children.

RESULTS

All 9 cases of orbital GS (60%) and almost all cases with concurrent AML M2 had t(8;21). This translocation was present in only 4 n(8.5%) of the remaining 47 AML cases without GS for which cytogenetic data were available. One case presented with a complex chromosomal translocation not previously associated with GS. The median disease-free survival of the GS patients, using conventional chemotherapy treatment protocols, was significantly better than for the patients with AML and no GS (P = 0.0004).

CONCLUSIONS

Our data support a strong association between orbital GS, t(8;21), and AML M2 in the pediatric population. This entity occurred virtually exclusively in black male children at presentation. One third of these children who presented with AML had a GS. The favorable prognosis noted in our GS patients on standard induction and intensification therapy without local irradiation conflicts with some previous reports but is consistent with the favorable outcome documented in AML with t(8;21).

12p rearrangement and DNA amplification mapped by comparative genomic hybridization in a patient with secondary myeloid leukemia

Rearrangements of the short arm of chromosome 12 (12p) are a common finding in hematologic malignancies. There has recently been considerable interest in chromosome 12 abnormalities in view of the mapping of the TEL gene to 12p13 and frequent 12p interstitial deletions. Overrepresentation of 12p sequences is, on the other hand, a consistent finding in testicular germ cell tumor (TGCT), and the 12p11.2-p12.1 subregion has been found to be specifically involved. We have studied a secondary leukemic patient whose cells contained 12p rearrangements with a view to clarifying the underlying molecular events. Fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH) have revealed the presence of 12p11 breakpoints on both 12 homologs as well as amplification of 12p11-p12-derived sequences. Six YACs and a cosmid probe have been used in an attempt to map the amplification unit on 12p. The two YACs contigs WC-1468 and WC-985 were not amplified, and our results suggested a small amplicon localized in the 12p11.2-p12 subregion. We speculate that this region harbors gene(s) which are critical in tumor formation and could be involved in both TGCT and our patient. Whether the same gene(s) are involved in both amplification and translocation is unknown.

1;17 translocations and other chromosome 17 rearrangements in human primary neuroblastoma tumors and cell lines

We report on the finding of a t(1;17) in two primary neuroblastomas. Subsequent fluorescence in situ hybridization (FISH) analysis revealed the presence of 1;17 translocations in four out of nine neuroblastoma cell lines. The chromosome 1 short arm breakpoints were determined using region-specific probes. FISH screening also demonstrated or confirmed the presence of 11;17 translocations in three cell lines and other chromosome 17 rearrangements in those cell lines that did not carry a t(1;17) or t(11;17). Our data extend previous cytogenetic findings and suggest that, in addition to the known involvement of chromosome 1, one or more genes on chromosome 17 also play a role in neuroblastoma development.

Lack of involvement of T-lymphocytes in the leukaemic population during prolonged chronic phase of Philadelphia chromosome positive chronic myeloid leukaemia

Nine patients with prolonged (> 2 years) chronic phase chronic myeloid leukaemia (CML) were investigated for the presence of T-cell involvement in the leukemic clone. Pure populations of peripheral blood T-cell populations were obtained by culturing separated mononuclear cells in the presence of pokeweed mitogen and IL2, until cultures showed > 99% pure T-cells. Purified T-cells and bone marrow and peripheral blood hematopoietic precursors were analysed for the presence of bcr-abl mRNA transcripts following RNA extraction and message amplification using polymerase chain reaction. In none of the 9 patients was bcr-abl mRNA found in T-lymphocytes while in all cases such transcripts were found in bone marrow and peripheral blood hematopoietic cells. Failure to detect T-cell involvement in patients with prolonged chronic phase CML using techniques designed to enhance even low level involvement of these cell populations supports the view that acquisition of the Ph chromosome abnormality does not occur in the totipotent stem cells but in more committed precursor cell/s with multilineage capacity but which only rarely retain the capacity for T-cell differentiation.

Derivative (11)t(7;11)(q11;q24) in a child with acute megakaryoblastic leukemia

We document the clinical, morphologic, and cytogenetic findings in a 2 1/2-year-old patient with acute megakaryoblastic leukemia. Cytogenetic analysis of peripheral blood leukemic cells revealed the presence of a der(11)t(7;11)(q11;q24). Chromosome 7 involvement is observed in nearly half of all cases of megakaryoblastic leukemias, however, the type of abnormality differs widely from one case to another. The der(11)t(7;11)(q11;q24) described here is the first reported to our knowledge.

Translocation t(1;7) revisited. Report of three further cases and review

Three white patients, two with myelofibrosis and one with refractory anemia, presented with a t(1;7). The clinical and cytogenetic findings are discussed in the context of 45 cases already published. Rather than the specific association of t(1;7) with a particular hematologic disorder, a review of the literature strongly suggests correlation with therapeutic or environmental exposure to toxic substances. The proposed mechanisms to explain the origin of t(1;7) are briefly reviewed.