TP53 deletions but not trisomy 12 are adverse in B-cell lymphoproliferative disorders

Karyotyping of diffuse large B-cell lymphomas: loss of 17p is associated with poor patient outcome

BACKGROUND

Cytogenetic studies of patients with diffuse large B-cell lymphoma (DLBCL) have revealed a large spectrum of chromosomal abnormalities, some of which may be clinically relevant. We wanted to evaluate possible associations between commonly acquired chromosome aberrations and prognosis in a large cohort of patients.

METHODS

All patients with DLBCL treated at our center during 1999-2010 with an abnormal G-banding karyotype determined on cells short-term cultured from diagnostic biopsies were included. Detailed information on staging, treatment, and outcome was available for all patients.

RESULTS

Of the 110 patients available for analysis, there were 48 deaths and 27 relapses after a median follow-up of 4.5 yr. Eleven different chromosomal abnormalities were detected in more than ten percent of patients. Of those, only loss of 17p, including the TP53 tumor suppressor gene, was significantly associated with inferior long-term prognosis. Five year overall and progression-free survival frequencies were 32% and 27% for patients with loss of 17p and 67% and 59% in patients without this abnormality.

CONCLUSION

In a relatively large cohort of patients with DLBCL analyzed by chromosome banding, loss of 17p was the only chromosomal abnormality associated with inferior survival in uni- and multivariate analysis.

The impact of trisomy 12, retinoblastoma gene and P53 in prognosis of B-cell chronic lymphocytic leukemia

PURPOSE

Routine cytogenetic analysis frequently fails to identify an abnormal clone in B-cell lymphocytic leukaemia (B-CLL) due to poor response to mitogen stimulation. Fluorescence in situ hybridization (FISH) suggest that chromosomal abnormalities occur more frequently, most commonly trisomy 12, retinoblastoma gene deletion (Rb1 gene) and P53 gene deletion.

PATIENTS AND METHODS

30 patients with B-CLL were enrolled in the trial from two centers in Cairo, Egypt during the period May 2000 to January 2002. Karyotyping and FISH assessment for possible chromosomal abnormalities (trisomy 12, Rb1 gene and P53 gene) were done at initial diagnosis. Results of cytogenetic abnormalities were correlated with clinical picture and survival.

RESULTS

The median age was 57.4 years (range 40-75). Karyotyping technique showed that no metaphase could be detected in 30%, metaphase with normal karyotyping was observed in 63% and cytogenetic abnormalities were detected in two cases (one trisomy 12 and one deletion in chromosome 13). FISH examination of interphase and metaphase nuclei revealed cytogenetic abnormalities in 15 cases (50%), trisomy 12 in 9 (30%), Rb1 gene deletion in 5 (17%) and P53 gene deletion in 3. At diagnosis, patients with trisomy 12 were significantly associated with advanced stage and absolute lymphocyte count of >or=30,000/mm(3). Univariate analysis showed that absolute lymphocyte count >or=30,000/mm(3) (p=0.004) and trisomy 12 (p=0.024) were associated with poor progression free survival.

CONCLUSION

Interphase and metaphase FISH studies improve the cytogenetic diagnosis of chromosomal abnormalities in B-CLL. Lymphocytosis and trisomy 12 may be a good indicator of poor prognosis.

6q deletion in Waldenström macroglobulinemia is associated with features of adverse prognosis

Fluorescence in situ hybridisation (FISH) is an effective technique for the cytogenetic analysis of Waldenström macroglobulinemia (WM), but the potential impact of molecular cytogenetics on disease evolution and as a prognostic marker is still unknown. Deletion of the long arm of chromosome 6 (6q-) is the most frequent cytogenetic abnormality in WM. This study analysed the prevalence of this aberration in 102 WM patients, and correlated it with disease characteristics. The incidence of 6q21 deletion was 7% by conventional cytogenetics and 34% when analysed by FISH (54% when cytoplasmic immunoglobulin M-FISH was used). Patients with deletion of 6q displayed features of adverse prognosis, such as higher levels of beta2-microglobulin and monoclonal paraprotein and a greater tendency to display anaemia and hypoalbuminemia. Interestingly, there was a correlation between the presence of 6q deletion and the International Staging System prognostic index (incidence of 6q- among patients stratified in stages 1, 2 and 3 was 24%, 42% and 67% respectively). Those patients diagnosed with smouldering WM who displayed the abnormality showed a trend to an earlier requirement of treatment. Finally, the survival analysis did not show differences between the two groups of patients, probably due to the short follow up of our series.

Interphase cytogenetic analysis in Argentinean B-cell chronic lymphocytic leukemia patients: association of trisomy 12 and del(13q14)

We have evaluated genomic aberrations by conventional cytogenetics and fluorescence in situ hybridization (FISH) analysis in a series of 57 Argentinean B-cell chronic lymphocytic leukemia (B-CLL) patients. The studies were performed on stimulated peripheral blood lymphocytes. FISH analysis for trisomy 12, 13q14 deletion, and monosomy of TP53 (also known as p53) was performed according to standard protocols. Our results showed 46.3% of patients with clonal chromosomal alterations by conventional cytogenetics and 80.7% by FISH. Trisomy 12 was found in 21.9% of patients by G-banding analysis and in 35% by FISH studies. Allelic loss of 13q14 was observed in 63.2% patients, most of them showing D13S319 and D13S25 deletion; 11% of patients showed TP53 monosomy. Coexistence of trisomy 12 and 13q14 deletion was found in 17.5% of patients. In this group, deletion 13q14 was the prevalent clone, with percentages 25-35% higher than those observed for trisomy 12, suggesting clonal evolution. The coexistence of trisomy 12 with deletion 13q14 was observed in a higher frequency than reported in the literature. A probable adverse prognosis is suggested for this group of patients, likely related to clonal evolution.

TP53 in hematological cancer: low incidence of mutations with significant clinical relevance

Inactivation of the wild-type p53 gene (TP53) by various genetic alterations is a major event in human tumorigenesis. More than 60% of human primary tumors exhibit a mutation in the p53 gene. Hematological malignancies present a rather low incidence of genetic alterations in this gene (10-20%). Nevertheless, epidemiological studies of the hematological malignancies indicate that the prognosis of patients with a mutation in the p53 gene is worse than those expressing the wild-type p53 protein. Correlations between drug resistance, altered apoptosis, and mutations in the p53 gene are found in hematological malignancies and leukemias. These issues, as well as the possibility of exploiting p53 and its various functions for new therapeutic strategies, are discussed in the present review.

Genetic imbalances in progressed B-cell chronic lymphocytic leukemia and transformed large-cell lymphoma (Richter's syndrome)

Chromosomal imbalances were examined by comparative genomic hybridization in 30 cases of B-cell chronic lymphocytic leukemia (CLL) at diagnosis, in sequential samples from 17 of these patients, and in 6 large B-cell lymphomas transformed from CLL [Richter's syndrome (RS)] with no available previous sample. The most common imbalances in CLL at diagnosis were gains in chromosome 12 (30%), and losses in chromosomes 13 (17%), 17p (17%), 8p (7%), 11q (7%), and 14q (7%). The analysis of sequential samples showed an increased number of chromosomal imbalances in 6 of 10 (60%) patients with clinical progression and in 2 patients with stable stage C disease. No karyotypic evolution was observed in four cases with stable stage A disease and in one RS clonally unrelated to the previous CLL. Gains of 2pter, and 7pter, and losses of 8p, 11q, and 17p were recurrent alterations associated with karyotype progression. RS showed a higher number of gains, losses, total alterations, and losses of 8p and chromosome 9 than CLL at diagnosis. 17p losses were associated with p53 gene mutations and with a significantly higher number of chromosomal imbalances than tumors with normal chromosome 17 profile. However, no relationship was observed between 9p deletions and p16(INK4a) gene alterations. Losses of 17p and an increased number of losses at diagnosis were significantly associated with a shorter survival. These findings indicate that CLL has frequent chromosomal imbalances, which may increase during the progression of the disease and transformation into large cell lymphoma. Genetic alterations detected by comparative genomic hybridization may also be of prognostic significance.

Typical and atypical chronic lymphocytic leukemia differ clinically and immunophenotypically

We compared the features of 17 cases of atypical chronic lymphocytic leukemia (aCLL) with those of a clinical control group of 24 cases of CLL. Quantitative flow cytometric data, available for 12 cases, were compared with an immunophenotypic control group of 58 cases using a relative fluorescence indexfor CD5, CD23, CD79b, and surface immunoglobulin light chain (sIg). Compared with the clinical control group, patients with aCLL had a higher mean WBC count and a lower platelet count. Patients with aCLL had a significantly higher probability of disease progression. Compared with an immunophenotypic control group of 58 CLL cases, 12 cases of aCLL demonstrated significantly higher expression of CD23. There was no significant difference in expression of sIg, CD79b, or CD5 between the groups. CD38 expression was noted in only 1 (9%) of 11 tested cases; 2 (18%) of 11 cases had trisomy 12. aCLL can be distinguished from typical CLL morphologically, clinically, and immunophenotypically. Atypical morphologic features in CLL seem to be a marker of aggressive clinical behavior.