Trisomy 12 in chronic lymphocytic leukemia. An interphase cytogenetic study by fluorescence in situ hybridization

Characterization of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) in Shanghai, China: molecular and cytogenetic characteristics, IgV gene restriction and hypermutation patterns

The clinical, cytogenetic and molecular features of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), a disease previously considered to be rare in Asia, were examined in consecutive series of 70 cases diagnosed by our laboratory over a 30-month period. Clonal abnormalities were observed in 80% of CLL/SLL cases using a combination of conventional cytogenetic and fluorescence in situ hybridization (FISH) analysis. Those involving 14q32/IGH were the most frequent (24 cases), followed by trisomy 12 and 11q abnormalities. IgV(H) gene usage was non-random with over-representation of V(H)4-34, V(H)3-23 and a previously unreported increase in V(H)3-48 gene use. Somatic hypermutation (SHM) of IgV(H) germline sequences was observed in 56.5% of cases with stereotyped patterns of SHM observed in V(H)4-34 heavy chain complimentary-determining (HCDR1) and framework region CFR2 sequences. These findings in a Chinese population suggest subtle geographical differences in IgV(H) gene usage while the remarkably specific pattern of SHM suggest that a relatively limited set of antigens may be involved in the development of this disease worldwide. IgV(H) gene mutation status was a significant predictor of initial survival in CLL/SLL. However, an influence of karyotype on prognosis was not observed.

Cytogenetic abnormalities in chronic B-cell lymphoproliferative disorders in Chinese patients

We analyzed the cytogenetic findings of 59 Chinese patients with chronic B-cell lymphoproliferative disorders. More than half of the patients (n = 36, 61%) had chronic lymphocytic leukemia. Cytogenetic abnormalities were demonstrated in 44.1% (26/59) of the patients. Trisomy 12 was the most frequent abnormality in chronic lymphocytic leukemia and was found in 27.8% (10/36) of the patients, indicating that the incidence of trisomy 12 in chronic lymphocytic leukemia in Chinese patients might not be low compared with the West as previously suggested. Structural abnormalities involving chromosomes 13 at band q14 were the next most common abnormalities in patients with chronic lymphocytic leukemia. Among the 11 patients with mantle cell lymphoma in leukemic phase, t(11;14) was seen in only 2 patients (18.2%). Several unusual cytogenetic abnormalities also were found.

Validation of primed in situ labeling (PRINS) for interphase analysis: comparative studies with conventional fluorescence in situ hybridization and chromosome analyses

Primed in situ labeling (PRINS) is a rapidly developing new technology with wide ranging clinical applications. To assess the sensitivity, specificity, and accuracy of PRINS, we carried out a retrospective study on cultured bone marrow cells to detect aneuploidy for chromosomes 7, 8, and 12. The results were then compared to the results of previous fluorescence in situ hybridization (FISH) and chromosome analyses (CA). In patients who showed aneuploidy with CA, both FISH and PRINS confirmed the aneuploidy in interphase cells. FISH and PRINS also showed excellent correlation with conventional cytogenetic analysis for the detection of mosaic aneuploidies. However, both FISH and PRINS showed significantly higher sensitivity in the detection of abnormal clones compared to CA. In 9 of the 17 cases, there were no significant differences in the detection rates between the two methods. Based on our studies, we conclude that PRINS is as sensitive as FISH in most cases for aneuploidy detection; and that PRINS, like FISH, is more sensitive than conventional CA for aneuploidy detection.

Genes and chromosomes in chronic B-cell leukemia

Cytogenetic analysis of patients with chronic B-cell leukemia (B-CLL) indicates that 50% have chromosome abnormalities, while fluorescence in situ hybridization (FISH) and molecular techniques reveal an even higher incidence. Trisomy 12 and deletions or translocation of chromosome 13q14 are the most common abnormalities, but in neither case has the gene or genes involved in the abnormalities been identified. Combined FISH and immunophenotyping studies suggest that both abnormalities are secondary events in B-CLL. Other recurring chromosome abnormalities include 6q-, 11q- and 12p-, but the genes involved in these abnormalities have not been identified. Involvement of the BCL1, BCL2, and BCL3 genes has been reported, but the numbers are low and the cases tend to be atypical. Trisomy 12 in association with complex karyotypic abnormalities is associated with a poor prognosis, and FISH studies show a strong correlation between trisomy 12, atypical morphology, and advanced disease. Ten to 15% of patients have mutations of p53 which is associated with advanced disease, resistance to treatment, and poor survival.

Assignment of the gene encoding type 1 gamma protein phosphatase catalytic subunit (PPP1CC) on human, rat, and mouse chromosomes

Using fluorescent in situ hybridization (FISH) method, a gene encoding the catalytic subunit of protein phosphatase type 1 gamma (PPP1CC) was mapped to human 12q24.1-q24.2, rat 7 q22, and mouse 10C. These results indicate that the PPP1CC is a member of conserved synteny group between rat chromosome 7, mouse chromosome 10 and human chromosome 12. These data and mapping data about other members of PP1 family show that in spite of the high identity of PP1 isoforms, each isoform is encoded by different genes which located on different chromosomes in human, rat, and mouse.

Hyperdiploid acute myeloid leukemia. Relationship between blast size and karyotype demonstrated by fluorescence in situ hybridization

Hyperdiploidy is a rare finding in acute myeloid leukemia (AML), and the cases described so far showed characteristic large and bizarre blasts. We further demonstrate this morphologic/karyotypic relationship in a case of hyperdiploid AML by fluorescence in situ hybridization. Together with previous observations, we propose that in myeloid leukemias, increase in DNA content is accompanied by a corresponding increase in blast size. If large and bizarre blasts are shown on morphologic analysis, polyploid metaphases on cytogenetic preparations should also be analyzed, as they may be derived from these cells.

Trisomy 8 in acute promyelocytic leukaemia: an interphase study by fluorescence in situ hybridization

Acute promyelocytic leukaemia (APL) is characterized by t(15;17)(q24;q21). Trisomy 8 is the commonest accompanying karyotypic aberration. We investigated 14 APL patients for trisomy 8 using fluorescence in situ hybridization (FISH). Conventional cytogenetic analysis showed trisomy 8 in two of nine successfully karyotyped cases. With FISH, a possible third case showing a subclone (1-2.5%) with trisomy 8 was found. The trisomy 8 clone size defined by karyotyping and FISH was concordant in one case and discordant in another, in which trisomy 8 was found in 100% of metaphases but only in 48% of leukaemic promyelocytes by FISH. Therefore trisomy 8 was mosaic in all the cases, suggesting that it had arisen from clonal evolution. All-trans-retinoic acid successfully induced morphologic remission in both cases with trisomy 8.

Refractory cytopenia with t(1;7),+8 abnormality and dysplastic eosinophils showing intranuclear Charcot-Leyden crystals: a fluorescence in situ hybridization study

A case of refractory cytopenia and marrow eosinophilia showing t(1;7) translocation and concomitant trisomy 8 is reported. The eosinophils were dysplastic, and showed the unique feature of intranuclear Charcot-Leyden crystal formation, giving rise to a 'lip-like' appearance. We speculate that this unusual cytologic feature resulted from abnormal precipitation of Charcot-Leyden crystal protein in the eosinophils. By fluorescence in situ hybridization using a chromosome 8 specific alpha-satellite probe, the abnormal eosinophils were shown to have derived from the abnormal clone. We postulate that the dysplastic clone might have retained a differentiation potential and be responsive to normal haemopoietic stimuli.

Involvement of eosinophils in acute myeloid leukaemia with monosomy 7 demonstrated by fluorescence in situ hybridization

Monosomy 7 is the commonest monosomy in acute myeloid leukaemia (AML). A patient with AML and monosomy 7 was investigated by fluorescence in situ hybridization. Monosomy 7 could be demonstrated in the blasts and also in mature eosinophils, but apparently not in lymphocytes. Monosomy 7 may occur in a multipotential myeloid progenitor cell as part of the multi-step leukaemogenic process.

The spectrum of chronic lymphoproliferative disorders in Chinese people. An analysis of 64 cases

BACKGROUND

Chronic lymphoproliferative disorders are considered rare in Oriental patients and are thought to constitute only 2% of all leukemias in these patients, compared to 20-30% in Western patients. We conducted a retrospective analysis of Chinese patients with chronic lymphoproliferative disorders to define the frequency and spectrum of these disorders.

METHODS

A consecutive series of Chinese patients with leukemia and lymphoproliferative disorders seen at two regional hospitals in Hong Kong were analyzed retrospectively. The diagnosis of chronic lymphoproliferative disorders was based on morphologic and immunologic criteria proposed by the French-American-British Cooperative Study Group.

RESULTS

Sixty-four Chinese patients with chronic lymphoproliferative disorders were identified, and these patients constituted 19% of a total of 342 cases of leukemia diagnosed in 3 years. Chronic lymphocytic leukemia was the most common form, occurring at a frequency of 12.5% of all leukemias. The clinicopathologic features of these patients were similar to those of Western patients, except that Chinese patients tended to present with more advanced (Rai's Stages III and IV; Binet's Stage C) and bulky (splenomegaly > 9 cm) disease, and expressed lambda light chain about six times more frequently. Other chronic lymphoproliferative disorders identified in this study included prolymphocytic leukemia, mantle zone lymphoma, hairy cell leukemia, splenic lymphoma with villous lymphocytes, large granular lymphocyte leukemia, and Sezary syndrome. The authors did not identify any case of human T-cell lymphotropic virus-I-related lymphoproliferative disorders within the study period.

CONCLUSION

In addition to providing the frequencies of various chronic lymphoproliferative disorders in southern Chinese people, this study also showed that these disorders no longer should be considered rare in this population. Inherent biologic differences between lymphoproliferative disorders in Chinese and Western patients also may exist.