Leukemia, lymphoma, and related disorders in families of children diagnosed with Wilms' tumor

Association of TP53 polymorphisms on the risk of Wilms tumor

BACKGROUND

Molecular factors influencing Wilms tumor (WT) development remain largely unknown. TP53 mutations seem to be restricted to the anaplastic WT subtype. However, TP53 polymorphisms do not have a defined role in the disease.

PROCEDURE

To assess the impact of TP53 mutations and polymorphisms (PIN2, PIN3, and PEX4) on risk of development, age at diagnosis, and survival in WT, we analyzed 46 blood DNA samples and 31 fresh tumor DNA samples from 52 patients with WT. Sequencing of TP53 exons 2-11 was performed.

RESULTS

Tumor DNA analysis revealed TP53 pathogenic missense mutations (p.V197M, p.R213Q, p.R248W, and p.R337C) in four samples (12.9%). Blood DNA samples revealed a novel intronic mutation, IVS2 + 37C > T, in one patient (2.2%). Bilaterality was associated with a twofold decrease in survival (P = 0.00037). Diffuse anaplasia also presented a lower survival probability compared to patients with non-anaplastic tumors, or with focal anaplasia (P = 0.045). Patients with a TP53 somatic mutation showed survival probability of 37.5% versus 85.0% for patients with no somatic mutations, although the difference was not statistically significant (P = 0.0706). PIN3 duplicated allele was associated with a 20-month later mean age at diagnosis (P = 0.0084). TP53 PEX4 C allele showed an increased risk for WT development (P = 0.0379). No relationship was found between survival and gender, age at diagnosis, or the less frequent alleles of PIN2, PIN3, and PEX4.

CONCLUSIONS

Our results demonstrate an association between PIN3 and age at diagnosis, as well as an association of PEX4 and risk of development of WT.

Is there an association with constitutional structural chromosomal abnormalities and hematologic neoplastic process? A short review

The occasional observation of constitutional chromosomal abnormalities in patients with a malignant disease has led to a number of studies on their potential role in cancer development. Investigations of families with hereditary cancers and constitutional chromosomal abnormalities have been key observations leading to the molecular identification of specific genes implicated in tumorigenesis. Large studies have been reported on the incidence of constitutional chromosomal aberrations in patients with hematologic malignancies, but they could not confirm an increased risk for hematologic malignancy among carriers of structural chromosomal changes. However, it is of particular interest that constitutional structural aberrations with breakpoints similar to leukemia-associated specific breakpoints have been reported in patients with hematologic malignancies. Because of insufficient data, it remains still unclear if these aberrations represent random events or are associated with malignancy. There has been a substantial discussion about mechanisms involved in constitutional structural chromosomal changes in the literature. The documentation of more patients with constitutional structural chromosomal changes could be of major importance. Most importantly, the molecular investigation of chromosomal regions involved in rearrangements could give useful information on the genetic events underlying constitutional anomalies, contributing to isolation of genes important in the development of the neoplastic process. Regarding constitutional anomalies in patients with hematologic disorders, a survey of the cytogenetic data of our cytogenetics unit is herein also presented.

Differential Expression of WT1 Gene Product in Non-Hodgkin Lymphomas

The tumor suppressor gene wt1 (Wilms tumor 1) encodes a zinc finger transcription factor reported to be expressed in many tumors, including mesotheliomas, carcinomas, and acute leukemias. However, WT1 expression in non-Hodgkin lymphomas (NHLs) has not been studied. The authors assessed for WT1 expression in six lymphoma/leukemia cell lines using Western blot methods after subcellular fractionation. We also assessed for WT1 expression in 167 NHLs using immunohistochemical methods. The B-cell NHLs analyzed were 18 diffuse large B-cell lymphomas, 13 marginal zone B-cell lymphomas, 9 small lymphocytic lymphomas, (DLBCLs), 8 follicular lymphomas, 6 mantle cell lymphomas, 5 Burkitt lymphomas, 3 lymphoplasmacytic lymphomas, and 2 B-cell lymphoblastic lymphomas. The T-cell NHLs analyzed were 43 anaplastic large cell lymphomas (ALCLs), 26 peripheral T-cell lymphomas unspecified, 13 angioimmunoblastic T-cell lymphomas, 6 cutaneous ALCLs, 6 cases of mycosis fungoides, 5 extranodal NK/T-cell lymphomas of nasal type, and 4 T-cell lymphoblastic lymphomas. WT1 levels were higher in cytoplasmic extracts than in nuclear extracts of the Karpas 299 and SU-DHL-1 lymphoma cell lines but were higher in nuclear extracts than in the cytoplasmic extracts of the Jurkat, HH, U-937, and K562 leukemia cell lines. In NHLs, WT1 was positive in 4 of 5 (80%) Burkitt lymphomas, 9 of 12 (75%) ALK-positive ALCLs, 3 of 6 (50%) lymphoblastic lymphomas (2 of 4 T-cell, 1 of 2 B-cell), 14 of 31 (45%) ALK-negative ALCLs, 6 of 18 (33%) DLBCLs, and 1 of 6 (17%) cutaneous ALCLs. WT1 was negative in all other NHLs tested. WT1 immunoreactivity was primarily cytoplasmic in all positive NHLs except T-cell lymphoblastic lymphoma. In conclusion, WT1 protein is frequently detected in the cytoplasm of a subset of high-grade NHLs.

A clinical overview of WT1 gene mutations

Mutations in the WT1 gene were anticipated to explain the genetic basis of the childhood kidney cancer, Wilms tumour (WT). Six years on, we review 100 reports of intragenic WT1 mutations and examine the accompanying clinical phenotypes. While only 5% of sporadic Wilms' tumours have intragenic WT1 mutations, > 90% of patients with the Denys-Drash syndrome (renal nephropathy, gonadal anomaly, predisposition to WT) carry constitutional intragenic WT1 mutations. WT1 mutations have also been reported in juvenile granulosa cell tumour, non-asbestos related mesothelioma, desmoplastic small round cell tumour and, most recently, acute myeloid leukemia.

No evidence of WT1 involvement in a Burkitt's lymphoma in a patient with Denys-Drash syndrome

BACKGROUND

We previously reported the case of a patient affected with Denys-Drash syndrome (DDS), who developed disseminated EBV-related Burkitt's lymphoma (BL) after kidney transplantation. Here, we describe the molecular characterisation of the WT1 gene in the constitutional and tumour DNA of this patient.

PATIENTS AND METHODS

WT1 exons 2 to 10 were sequenced in constitutional and tumour DNAs. By Southern blotting the latter was also investigated for the presence of gene rearrangements. Gene expression analysis in tumour cells was performed by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

A germline missense mutation affecting one of the zinc finger domains of the gene, and previously reported in other DDS cases, was observed. No alterations of the constitutionally wild-type WT1 allele and no expression of the gene were observed in BL cells. A small group of BLs from other paediatric patients showed a variable expression of WT1.

CONCLUSIONS

Our findings indicate that WT1 is unlikely to be involved in the onset of BL in our case. However, a possible role of the gene in at least a subset of these lymphoproliferative diseases may be suggested.

The Wilms tumour gene WT1 in leukaemia

The WT1 gene is essential for kidney development and is mutated in some Wilms tumours. It is also expressed at a high level in many acute leukaemias and in some haematopoietic progenitor cells, and mutations have been found in leukaemias. The function of WT1, which is a zinc finger protein and has domains characteristic of transcription factors, is not well understood. The level of expression is highest in leukaemias with immature phenotypes. Expression of WT1 is downregulated during differentiation of leukaemic cell lines and high levels of WT1 expression can cause cell cycle arrest and/or apoptosis. This may reflect a role in the control of normal haematopoiesis, which can be abrogated by mutations in the gene and form part of the pathway towards leukaemogenesis.