Cytogenetic studies in 77 patients with chronic lymphocytic leukemia: correlations with clinical, immunologic, and phenotypic data

Cytogenetic and flow cytometry evaluation of Richter syndrome reveals MYC, CDKN2A, IGH alterations with loss of CD52, CD62L and increase of CD71 antigen expression as the most frequent recurrent abnormalities

OBJECTIVES

Richter syndrome (RS) is a transformation of chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) into high-grade lymphoma. There are only limited data on flow cytometry (FCM) and cytogenetics in RS.

METHODS

In this study, FCM, classic cytogenetics (CC), and fluorescence in situ hybridization (FISH) were performed in eight RS cases.

RESULTS

Most cases of RS were characterized by a loss/decrease of CD52 and CD62L and increased CD71 expression. CC identified complex karyotypes, with losses of 9/9p and 17/17p as the most frequent in four of seven cases. Seven RS cases demonstrated MYC abnormalities. Disruptions of CDKN2A and IGH were identified in five of seven and four of seven RS cases, respectively.

CONCLUSIONS

Newly diagnosed RS is an oncologic emergency, and a quick diagnostic decision is crucial in clinical practice. Therefore, in patients with CLL/SLL and rapidly enlarging asymmetric lymphadenopathy and/or extranodal tumors, we strongly advise FCM of fine-needle aspiration biopsy (FNAB) material, including CD62L, CD52, and CD71 analysis as well as assessment of karyotype and at least MYC abnormalities by FISH of the same FNAB material. Loss of CD52 expression in RS most likely predicts resistance to alemtuzumab therapy, which is frequently used in CLL.

Predictive markers and driving factors behind Richter syndrome development

Transformation of chronic lymphocytic leukemia (CLL) to diffuse large B-cell lymphoma (DLBCL) is known as Richter syndrome (RS). In the entire CLL population, the cumulative prevalence of RS development steadily increases at a rate of 1% per year. Considering conventional predictors of CLL, patient subgroups at high risk of developing RS are characterized by the expression of CD38, absence of del13q14, and a lymph node size >3 cm. Novel risk factors for predicting RS development at CLL diagnosis have been recently identified and include: the host genotype of the CD38 locus and of other genes; telomere length of CLL cells; stereotyped B-cell receptor; and usage of specific immunoglobulin variable genes (IGHV4-39). Importantly, although some risk factors predict both CLL progression and transformation to RS, others (CD38 genotype, absence of del13q14, IGHV4-39 usage, stereotyped B-cell receptor) appear to specifically predict RS. The definition of RS encompasses at least two different conditions: DLBCLs that are clonally related to the pre-existing CLL (accounting for most cases), or DLBCL unrelated to the CLL clone. The transition from CLL to clonally related RS is accompanied by the acquisition of novel genetic alterations that may account for the chemorefractoriness of RS. Genome-wide studies that are currently ongoing are important for identifying novel molecular lesions implicated in RS that might represent a suitable target for future therapeutic strategies.

The genetics of Richter syndrome reveals disease heterogeneity and predicts survival after transformation

Richter syndrome (RS) represents the development of diffuse large B-cell lymphoma in the context of chronic lymphocytic leukemia. The scarcity of biologic information about RS has hampered the identification of molecular predictors of RS outcome. We addressed this issue by performing a comprehensive molecular characterization of 86 pathologically proven RS. TP53 disruption (47.1%) and c-MYC abnormalities (26.2%) were the most frequent alterations, whereas common genetic lesions of de novo diffuse large B-cell lymphoma were rare or absent. By multivariate analysis, lack of TP53 disruption (hazard ratio, 0.43; P = .003) translated into significant survival advantage with 57% reduction in risk of death. An algorithm based on TP53 disruption, response to RS treatment, and Eastern Cooperative Oncology Group performance status had 80.9% probability of correctly discriminating RS survival (c-index = .809). RS that were clonally unrelated to the paired chronic lymphocytic leukemia phase were clinically and biologically different from clonally related RS because of significantly longer survival (median, 62.5 months vs 14.2 months; P = .017) and lower prevalence of TP53 disruption (23.1% vs 60.0%; P = .018) and B-cell receptor stereotypy (7.6% vs 50.0%; P = .009). The molecular dissection of RS into biologically distinct categories highlights the genetic heterogeneity of this disorder and provides clinically relevant information for refining the prognostic stratification of patients.

Richter syndrome: molecular insights and clinical perspectives

Richter syndrome (RS) represents the clinico-pathologic transformation of chronic lymphocytic leukaemia (CLL) to an aggressive lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL). The clinical definition of RS is heterogeneous, and encompasses at least two biologically different conditions: (i) CLL transformation to a clonally related DLBCL, that accounts for the majority of cases; (ii) development of a DLBCL unrelated to the CLL clone. In clonally related RS, the pathogenetic link between the CLL and the DLBCL phases is substantiated by the acquisition of novel molecular lesions at the time of clinico-pathologic transformation. RS is not a rare event in the natural history of CLL, since the cumulative incidence of RS at 10 years exceeds 10%. Prompt recognition of RS is known to be clinically useful, and may be favoured by close monitoring of CLL patients harbouring clinical and/or biological risk factors of RS development. Conventional risk factors that are independent predictors of RS development at the time of CLL diagnosis include: (i) expression of CD38; (ii) absence of del13q14 and (iii) lymph node size > or =3 cm. Other risk factors of RS development include CD38 genotype and usage of specific immunoglobulin variable genes. The molecular pathogenesis of RS has been elucidated to a certain extent. Acquisition of TP53 mutations and/or 17p13 deletion is a frequent molecular event in RS, as it is in other types of transformation from indolent to aggressive B-cell malignancies. Additional molecular alterations are being revealed by genome wide studies. Once that transformation has occurred, RS prognosis may be predicted by the RS score, based on performance status, LDH, platelet count, tumour size and number of prior therapies. Depending on patient's age and RS score, the therapeutic options for RS may range from conventional immunochemotherapy to allogeneic bone marrow transplantation.

Recent advances in the diagnosis and therapy of richter’s syndrome

Richter's syndrome (RS) denotes the development of aggressive lymphoma that arises in patients with chronic lymphocytic leukemia (CLL). Presenting features typically include a rapid clinical deterioration with fever in the absence of infection, progressive lymph node enlargement, and an elevation in serum LDH. Diagnostic biopsy of affected sites usually reveals large cell lymphomas; however, Hodgkin variant cases have been described. Richter's transformation occurs in approx 5% of CLL patients and may be associated with infection with Epstein-Barr virus (EBV). Chromosome 11 and 14 abnormalities have also been described as well as tumor suppressor gene defects involving p53, p21, and p27. Treatment options for these patients are limited and include combination chemotherapy with or without the addition of monoclonal antibodies and stem cell transplantation. Response to therapy is variable and generally short-lived. Median survival is usually in the order of 5-8 mo. More effective management for RS is needed as well as prognostic models that will identify CLL patients at risk of transformation. This review will address the current status of RS and deal with the pathophysiology, diagnostic approach, and treatment of this challenging disease.

Richter syndrome: biology, incidence, and therapeutic strategies

Richter's transformation denotes the development of high-grade non-Hodgkin lymphoma, prolymphocytic leukemia, Hodgkin disease, or acute leukemia in patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma. A search of published articles in Medline (PubMed) and abstracts from professional meetings was performed. An electronic database search of patients with CLL at The University of Texas M. D. Anderson Cancer Center (Houston, TX) determined the incidence of Richter syndrome (RS) in patients with CLL between 1992 and 2002. RS occurs in approximately 5% of patients with CLL. The large cells of RS may arise through transformation of the original CLL clone or represent a new neoplasm. RS may be triggered by viral infections, such as Epstein-Barr virus. Trisomy 12 and chromosome 11 abnormalities are more frequent in patients with RS than in the overall population of patients with CLL. Multiple genetic defects, such as mutations of the p53 tumor suppressor gene, p16INK4A, and p21, loss of p27 expression, deletion of retinoblastoma, increased copy number of C-MYC, and decreased expression of the A-MYB gene, have been described. These abnormalities may cause CLL cells to proliferate and-by facilitating the acquisition of new genetic abnormalities-to transform into RS cells. Therapeutic strategies include intensive chemotherapy, monoclonal antibodies, and stem cell transplantation. The response rates range from 5% to 43% (complete response, 5-38%), and the median survival duration ranges from 5 months to 8 months. In conclusion, RS may be triggered by viral infections or by genetic defects. Current treatments are aggressive, but prognosis is poor. Novel curative treatment strategies are needed.

High-grade transformation of low-grade non-Hodgkin's lymphomas: mechanisms of tumor progression

In the natural history of low-grade non-Hodgkin's lymphomas (NHL) a prolonged indolent phase of the disease may be followed by clinical progression toward intermediate and high-grade disease. The abrupt appearance of diffuse large cell lymphoma (DLL) in patients with low-grade NHL is usually associated with an accelerated clinical course and shorter time of survival. The histologic transformation has been described for chronic lymphocytic leukemia or small lymphocytic lymphoma (CLL/SLL), follicular lymphoma (FL), mantle cell lymphoma (MCL) and lymphoma of mucosa-associated lymphoid tissue (MALT). Although the histological transformation of low-grade lymphomas are relatively frequent, the clonal relationship between the two neoplasms and pathogenetic mechanisms underlying the progression of the disease are widely debated. In this review, we will focus on the possible relationship between the low-grade and the transformed high-grade NHLs and genetic lesions that may be associated with the histologic transformation and clinical progression of the disease.

Trisomy 12 in B-cell chronic lymphocytic leukemia: correlation with advanced disease, atypical morphology, high levels of sCD25, and with refractoriness to treatment

In situ hybridization was performed to study the clinical significance of trisomy 12 in fifty patients with B-cell chronic lymphocytic leukemia at various stages of disease. Trisomy 12 was detected in 12%-65% (median 53%) of the circulating neoplastic cells in seven out of 20 patients with advanced Binet stage C disease. In contrast, 22 patients with Binet stage A and eight patients with Binet stage B disease were found to be negative for trisomy 12. As occurrence of trisomy 12 was associated with the presence of B-symptoms and hepatosplenomegaly, its association with advanced disease was further considered. In addition, atypical morphology was a common finding in trisomic patients who also displayed higher serum levels of soluble CD25 than patients without trisomy at Binet stage C. No significant differences were detected in serum levels of soluble CD8 and of soluble CD23. No correlation with a lymphocyte doubling time of < 12 months, marked lymphadenopathy, or prior treatment was apparent. However, refractoriness to treatment was evident more frequently in trisomic than in non-trisomic patients (p < .05). In conclusion, trisomy 12 in B-cell chronic lymphocytic leukemia appears to occur predominantly in advanced and symptomatic disease with atypical morphology. It could indicate a high risk for treatment failure thus serving as a marker of poor prognosis in this disease.

Origin of high-grade lymphomas in Richter syndrome

Patients with B cell chronic lymphocytic leukemia (CLL) occasionally develop high-grade B cell lymphomas that are associated with constitutional symptoms, rapidly progressive lymphadenopathy, and swift clinical deterioration. Now known as Richter syndrome, this symptom complex develops in approximately 5% of all patients with CLL. Structural and molecular analysis of the immunoglobulin (Ig) genes have allowed investigators to define the clonal relationship between the leukemia and lymphoma cells of a given patient. In most cases the aggressive lymphoma evolves from the original leukemia cell clone. However, in some cases the lymphoma apparently represents a second malignancy. Differentiation between these two types of lymphoma may have clinical significance. Further investigation is required to allow for identification of CLL patients who are at risk for developing Richter syndrome and to understand factors involved in its etiopathogenesis.

Cytogenetic studies in patients with Richter's syndrome

Cytogenetic studies in six patients with Richter's syndrome (RS) showed complex chromosome abnormalities and chromosomal instability in five. No specific chromosomal abnormality was detected. Chromosomes 14 and 11 were the most frequently involved. Neither deletion of 13q14 nor complete trisomy 12 was observed. Two patients had structural rearrangement of 12q with t(5;12)(q21-q22;q23-q24). The involvement of this region of chromosome 12 may be significant, although not specific for chronic lymphocytic leukemia. These results were compared to those found in cytogenetically studied RS patients from the literature.

Chromosomal analysis of purified B-chronic lymphocytic leukemia lymphocyte cultures: comparison with whole blood cultures and in situ hybridization

Chromosomal analysis of stimulated whole blood cells and purified B lymphocytes was performed in 13 stage A(0) and 1 stage C(IV) chronic lymphocytic leukemia (B-CLL) patients. Abnormal clones were found in 6 cases in purified B lymphocytes cultures and in a single one in whole blood cultures. In situ hybridization with a chromosome 12 probe was in accordance with the chromosomal analysis of purified B-CLL lymphocytes and not with the results obtained using whole blood culture. Cytogenetic analysis of isolated B cells is simple and sensitive. It enhances the detection of abnormal clones in B-CLL and applied to larger series of patients, it should allow a precise evaluation of the incidence of chromosomal abnormalities in CLL and of their clinical (prognostic) significance.

Establishment and characterization of the tumors of chronic lymphocytic leukemia cell line in nude and SCID mice

A new cell line, designated MO1043, was established from the peripheral blood (PB) of a patient with B-cell chronic lymphocytic leukemia (CLL). Both the PB leukemia cells and MO1043 were found to have an abnormal cytogenetic marker of trisomy 12, the most common cytogenetic abnormality in CLL. In addition, both the PB cells and MO1043 expressed a cell surface phenotype of typical B-CLLs. The MO1043 was efficiently transplanted into X-irradiated athymic nude mice by i.p. inoculation after it was subjected to serial passages in new born (1 week old) and irradiated adult nude mice. The tumor of a CLL cell line (termed CLL tumor) was also generated in the nude mice by s.c. inoculation of the cells. The MO1043 was inoculated i.p. into mice with severe combined immunodeficiency (SCID) which had not been subject to any preconditionings. The CLL tumor in the non-conditioned SCID mice was disseminated to various tissues in a manner more analogous to CLL tumors in patients as compared with nude mice, where the CLL tumors were not as widely disseminated. At each of four different tumor doses, i.e. 2 x 10(6), 6 x 10(6), 1.8 x 10(7) and 5.4 +/- 10(7) cells of MO1043, the transplantability was 100%. Titration experiments revealed a reciprocal relationship between survival and the number of tumor cells inoculated. FACS analysis showed that several cell surface markers of the parental MO1043 were maintained in CLL tumors from nude and SCID mice. Fluorescence in situ hybridization with novel DNA probes demonstrated that CLL tumors of both nude and SCID mice maintained trisomy 12. The CLL tumor models developed here, particularly the SCID mouse model, may be very useful for therapeutic studies of CLL.

Trisomy 12 in Epstein-Barr virus-transformed lymphoblastoid cell lines of normal individuals and patients with nonhematologic malignancies

Karyotypes of 36 lymphoblastoid cell lines established by Epstein-Barr virus (EBV) transformation of peripheral blood lymphocytes (PBL) of eight normal individuals and 28 patients with various nonhematologic malignancies were analyzed. In seven lines (19.4%), cells with trisomy 12 were noted, with clonality in two of these lines. In two of 11 metaphases with such trisomy, chromosome 12 was involved in structural rearrangements [t(8;12)(q12;p12) and t(12;12)(q11;q24)]. No cells with trisomy 12 were observed in phytohemagglutinin (PHA)-stimulated PBL cultures of these individuals. In 250 individuals (normal and with nonhematologic malignancies) examined in our laboratory in the last 5 years, extra copies of chromosome 12 in PHA-stimulated PBL cultures were observed in only five of 23,216 cells (0.02%). There were no cases of clonality in these samples. The frequency of an extra chromosome 12 was comparable to that of the other chromosomes except 21 and X, whose frequency of occurrence was 0.08% and 0.09%, respectively. These findings should be considered random events in PHA-stimulated PBL. On the contrary, in lymphoblastoid cell lines established by EBV transformation, trisomy of chromosome 12 was the most frequent numerical abnormality. It was observed in 64.7% of all cases with chromosome gains and therefore could not be considered a random occurrence. The specificity of this phenomenon for EBV transformation is supported by the results of cytogenetic analysis of eight lymphoblastoid cell lines established by an alternative procedure in our laboratory [1]. In 400 cells analyzed not a single cell with trisomy 12 was observed. We suggest that EBV transformation might either randomly induce formation of such cells in immortalized B-cell populations or show potentially blastomogenic cells or proneness to their formation in certain individuals who could be predisposed to develop lymphoproliferative diseases, especially chronic lymphocytic leukemia (CLL) in which trisomy of chromosome 12 is the most common alteration.

Chromosome analyses in chronic lymphocytic leukemia and related B-cell neoplasms

Chromosome analyses were performed by routine G-banding in 29 patients with B-cell chronic lymphocytic leukemia (B-CLL), six with immunocytoma (IC), three with centroblastic-centrocytic (cb-cc) lymphoma, and one with hairy cell leukemia (HCL). Ages of the patients were between 46 and 81 years (mean, 63 years). 12-O-tetradecanoyl-phorbol-13-acetate (TPA) was used as a mitogen to stimulate leukemic B-cells in 72-hour cultures. Twenty-one patients had one or more chromosomal abnormalities; and in 13 patients, they were clonal; 18 patients had a normal karyotype. Seven patients had trisomy 12 (three B-CLL, two IC, two cb-cc lymphoma); two (B-CLL) had it as the sole abnormality. One patient with B-CLL had trisomy 18 as the sole abnormality, and one with IC had trisomy 18 in combination with trisomy 19. One patient with B-CLL had t(1;6)(p36;p21) as a clonal structural abnormality. A t(11;14)(q13;q32) was consistently observed in one patient with cb-cc lymphoma together with inv(1) (p22p36), der(4)t(4;?)(p16;?), del(6)(q13) and other variable changes. One patient with morphologically atypical B-CLL had t(1;11)(p36;q13) together with der(X)t(X;?)(q26;?), der(3)t(3;?)(q29;?), der(8)t(4;8)(q12;q24.1) and additional variable changes. Both patients with these complex karyotypes were in an advanced stage of disease (Binet stage C) and died within 3-6 months after chromosome analysis.

Abnormalities involving chromosome 6 in newly diagnosed patients with non-Hodgkin's lymphoma. Nebraska Lymphoma Study Group

Several cytogenetic abnormalities involving chromosome 6 occurring in non-Hodgkin's lymphoma (NHL) have been described. We report 34 newly diagnosed patients with NHL who had an abnormal chromosome 6 on initial biopsy. Monosomies (n = 5), trisomies (n = 6), deletions of 6q (n = 13), and isochromosomes 6p (n = 9) were frequently observed and translocations were rare. As compared with 70 other NHL patients with cytogenetic abnormalities, the patients with an abnormal chromosome 6 had a higher frequency of immunoblastic lymphoma (p less than 0.001). These patients also were more likely to have B symptoms (p = 0.02). Patients with a breakpoint at 6q11-16 all had a deletion of the distal portion and also were more likely to have B symptoms (p less than 0.001). Most patients with breakpoints at 6q21-25 had a deletion associated with a lower frequency of stage IV disease (p = 0.03) and a higher complete remission (CR) rate (p = 0.03). The patients with an i(6p) had a lower frequency of stage IV disease (p = 0.03), and the patients with a trisomy 6 had a shorter median survival (p = 0.005). Our results suggest that chromosome 6, especially the long arm, carries important information for the clinical behavior of NHL. Future studies are necessary to resolve the molecular defects.

Chromosome aberrations in B-cell chronic lymphocytic leukemia. Pathogenetic and clinical implications

Chromosome analyses were performed on leukemic cells from 102 patients with B-CLL, of whom 84 were untreated. B-cell mitogen-induced CLL cells yielded suitable metaphases in 85 patients, and 55 showed clonal chromosomal aberrations. Trisomy 12 was found in 26 patients. In nine patients the + 12 was a single aberration. A 14q + chromosome or deletions of the long arm of chromosomes 6, 11, or 13 were other recurrent aberrations. Patients with Rai stage I or more had more frequently clonal aberrations than patients with stage 0 disease (p less than .02). Patients with clonal aberrations had poorer 5-year survival than those with a normal karyotype (p less than .05). Patients with a high percentage of abnormal metaphases in the sample had poorer prognosis than patients with high admixture of normal metaphases (p less than .01). Of the specific clonal aberrations those with 14q + or trisomy 12 tended to have slightly poorer and those with 6q- or structural aberrations involving the long arm of chromosome 13 tended to have better prognosis than patients with other chromosomal aberrations. A complex karyotype tended to be an adverse prognostic sign. Clonal evolution is rare: complex karyotypes are found at diagnosis and clones with single aberrations did not acquire additional chromosome aberrations despite progressive disease and treatment. Nine hundred and seventy-nine published cases are reviewed, and pathogenetic mechanisms, such as oncogenes and gene dosage, are discussed.

Clonal chromosomal changes in chronic lymphocytic leukemia

Cytogenetic analysis was carried out in 28 B-CLL patients (21 males and 7 females, 38-85 years old, with median age 64 years, disease stage O-IV). Peripheral nominator cells (1 x 10(7)) or isolated B-lymphocytes were incubated in vitro for 5-7 days. The cells were stimulated by pokeweed mitogen (PWM), or phorbol myristate-acetate (PMA), with or without 10% conditioned medium (CM) derived from a T cell leukemia line or 10% B-cell growth factor (BCGF). Twenty-two patients (79%) responded to PWM + CM; 5 out of 5 patients responded to PWM + BCGF. The average mitotic index (+/- S.E.M.) for PWM, PMA, PWM + CM, PMA + CM, PWM + BCGF were 0.13 +/- 0.01, 0.24 +/- 0.13, 0.51 +/- 0.11, 0.14 +/- 0.06 and 0.63 +/- 0.15, respectively. Cytogenetic analysis revealed the presence of abnormal karyotypes in 22 patients. Fourteen patients (50%) had clonal chromosome aberrations which included: monosomy 1, 9, 17, 18, 21, and X chromosome, and trisomy of chromosomes 7, 9, 20, 21 and 22. The clonal structural aberrations were i(6q), inv(12) (q15q24), del(5) (p13p15), del(10) (q24). No homogeneously staining regions (HSR) were observed. Four patients with resistance to anti-neoplastic drugs showed the presence of double minute chromosomes (dmin) ranging in frequency from 5 to 50%.

Cytogenetic and molecular changes in chronic B-cell leukemia

Cytogenetic studies using B-cell mitogens indicate that approximately 50% of patients with chronic B-cell leukemia (CLL) have chromosome abnormalities. The most common abnormality is an additional chromosome 12, either as the sole abnormality or in conjunction with other abnormalities such as 14q+, 6q-, and 11q-. In two instances, the 14q+ is a result of a translocation from either chromosome 11, t(11;14), or chromosome 19, t(14;19). These two translocations led to the identification of the bcl-1 and bcl-3 genes located on chromosomes 11 and 19, respectively. Very few instances of oncogene activation have been described and it does not seem to be an important mechanism in the pathogenesis of CLL. Further cytogenetic and molecular studies may provide clues for the identification of the genes involved in CLL.

Use of phorbol-12,13-dibutyrate as a mitogen in the cytogenetic analysis of tumors with low mitotic indexes

Solid tumors, particularly those involving the colon, breast, and lung, are the most common tumors in humans. However, many technical difficulties exist in obtaining analyzable chromosomes from these tumors, including the inability to stimulate cell division. Phorbol-12,13-dibutyrate (PDBu) is a tumor promoter that activates a variety of cellular responses, including proliferation. Using flow cytometry, we have demonstrated that PDBu acts as a mitogen in primary cultures of colon tumor cells. Based on these results, we developed a short-term culture technique that greatly improves the yield of analyzable metaphases from colon tumors. Stimulated cultures consistently contained at least ten times more metaphases than unstimulated cultures, and chromosome morphology was improved. By modifying this technique with the addition of the calcium ionophore A23187, we have successfully obtained analyzable chromosomes from the peripheral blood of normal individuals, chronic lymphocytic leukemia patients, and a nodular small cell lymphoma patient. These results demonstrate that mitogenic stimulation by PDBu is a valuable technique in the cytogenetic analysis of colon tumors. By using PDBu alone or in combination with other agents, this technique may also be applicable to many other tumors that are difficult to karyotype because of an inability to obtain mitoses.

Karyotypic stability in chronic B-cell leukemia

Twenty-one patients with B-cell chronic lymphocytic leukemia (B-CLL) have been followed for more than 2 years with serial cytogenetic studies, including 11 cases for more than 5 years and three others for more than 10 years. A chromosomally abnormal clone was present at the time of initial study in 10 of these patients, and neither these nor the 11 individuals with a normal karyotype had any cytogenetic evolution during the follow-up period, although clinical progression, requiring therapy, was observed in 13 cases. In an additional 12 B-CLL patients who had repeat chromosome studies but were followed for less than 2 years, two patients with advanced disease and multiple cytogenetic abnormalities developed minor additional karyotypic changes and died within 18 months, and two patients with a normal karyotype developed rapidly progressive disease associated with an emerging chromosomally abnormal clone and survived only 1 year. These results demonstrate that karyotypic evolution is rare in B-CLL. Its occurrence indicates a poor prognosis, but its rarity suggests that clinical progression in this disease is usually more dependent on other factors.

Progression of a human B cell chronic lymphocytic leukemia line in nude mice

Subcutaneous (s.c.) inoculation of the 85-4LN subline, derived from a lymph nodal metastasis of the Epstein-Barr virus (EBV) transformed human chronic lymphocytic leukemia (CLL) B cell line, EBV-CLL (1), produced progressively growing lethal tumors in 31/35 nonirradiated (88.6%) and 22/25 (88%) of whole-body irradiated (440 rad) nude mice. In contrast, EBV-CLL(1) could produce progressive tumors only in irradiated nude mice. All 85-4LN cells had Epstein-Barr virus nuclear antigen and reacted with pan B and anti-la antibodies. The morphology and ultrastructural features was consistent with the lymphoblastoid nature of the cells. In all s.c. tumor bearing mice, there was enlargement of the spleen and draining lymph nodes. Karyological studies revealed human cells in the spleen and draining nodes in all the mice investigated. Metastases in nonlymphoid organs were seen in 1/8 irradiated and 8/12 nonirradiated mice. The subline contained 77% cells with 47,XY, +12 and 23% cells with 45,XY karyotype. The clone with trisomy 12 did not have any growth advantage either in s.c. transplants or in splenic/lymph nodal metastases. Treatment with the maximum permissible doses of methotrexate (MTX) or chlorambucil (CBL) revealed xenografts to be more sensitive to MTX than CBL. A clone with a 1g+ marker, i.e., 46,XY,Dup(1) (q11----q32) appeared to be associated with resistance to CBL. We have not seen any previous report on the growth and dissemination of human CLL B cells in nonirradiated nude mice. The 85-4LN subline, thus, provides a model for studying the progression, dissemination and therapeutic response of human CLL-B cells.

Cytogenetic and immunologic characterization of mitotic cells in chronic lymphocytic leukaemia

Lymphocytes from 14 patients with chronic B-cell leukaemia (B-CLL) and one with chronic T-cell leukaemia (T-CLL) were studied by the MAC (Morphology, Antibodies, Chromosomes) method, which allows simultaneous analysis of the morphology, immunologic phenotype and karyotype of the same mitotic cell. Use of the MAC-method in present studies has yielded new information about the cytogenetics of CLL. Although most of the interphase cells from patients with B-CLL were positive for B-cell markers, many of the mitotic cells turned out to be T cells, supporting the notion that the cells studied by conventional chromosome analysis are often non-neoplastic T cells. In some B-CLL cases with normal karyotype in the conventional chromosome study, however, most of the mitotic cells were B cells, indicating that neoplastic B cells may also have a normal karyotype. The patient with T-CLL had normal karyotype even though most of the mitoses were T cells. The chromosome abnormalities found were restricted to cells with light chain clonality. Our results show that clonal chromosome abnormalities do occur in neoplastic B cells of patients with B-CLL.

Role of chromosomal abnormalities in chronic lymphocytic leukemia

Chromosomal aberrations occur in both B-CLL and T-CLL. The polyclonal B-cell mitogens, in particular Epstein-Barr virus and lipopolysaccharide from E. coli, have been used successfully to reveal chromosomal abnormalities in 40-60% of patients with B-CLL, while T-cell mitogens have shown chromosomal aberrations in T-CLL. The most common clonal chromosomal aberration in B-CLL is an extra chromosome 12, alone or together with other abnormalities. Other common aberrations are 14q+, structural aberrations on 6, 11, 12 and 13. Proto-oncogenes are frequently located close to breakpoints. The proto-oncogene c-K-ras is located on chromosome 12 and an abnormal transcript has recently been implicated in a subset of B-CLL-patients. An extra chromosome 12 as well as multiple chromosomal abnormalities in B-CLL appear to predict a less favourable prognosis. T-CLL is in most patients characterized by an inv(14), an extra 8q and structural abnormalities in chromosome 7. The genes for the specific T-cell receptor as well as the immunoglobulin heavy chain are located on these chromosomes. Chromosomal aberrations appear to have pathogenetic importance in both B-CLL and T-CLL.

B-chronic lymphocytic leukemia. Prognostic implication of bone marrow histology in 120 patients experience from a single hematology unit

The available staging systems for B-chronic lymphocytic leukemia (B-CLL) do not always predict the clinical course and the prognosis of the disease. In these systems, the pattern of bone marrow histology is not incorporated. In the current report we investigate the prognostic value of the diffuse or nondiffuse pattern of bone marrow involvement in 120 B-CLL patients in relation to their actuarial survival, and we compare these results with the actuarial survival based on the International Workshop system. In addition, we analyze the influence of the diffuse or nondiffuse pattern on the actuarial survival, in relation to the individual clinical stages (A, B, C). All patients were diagnosed and followed-up in the same Unit. Our patients were divided into Stage A (64), Stage B (22), and Stage C (34). They were also subdivided into those with a diffuse (46) and those with a nondiffuse (74) pattern of bone marrow histology. The difference in the actuarial survival in relation to their clinical stage (A, B, C) was statistically significant (P less than 0.025). A greater statistical difference (P less than 0.005) was found when the actuarial survival was analyzed in relation to the diffuse or nondiffuse pattern of bone marrow histology. No statistically significant differences could be found (P greater than 0.1), when the actuarial survival was calculated in every stage (A, B, C), on the basis of the diffuse or nondiffuse pattern of bone marrow histology. When our Stage A and B patients were analyzed for disease progression, in relation to the diffuse or nondiffuse bone marrow histology, it was found that 66.6% of the diffuse Stage A patients and 88% of the diffuse Stage B patients had disease progression as compared to only 8.6% for the nondiffuse Stage A patients and 33% for the nondiffuse Stage B patients. Our findings indicate that: the pattern of bone marrow histology in B-CLL patients is the single most important prognostic parameter in this disease; a clinicopathologic staging system for B-CLL may be justified; and the diffuse pattern of bone marrow histology could be considered as the best criterion for initiation of therapy in these patients.

Cytogenetic evidence for clonal evolution in B-cell chronic lymphocytic leukemia

Sequential cytogenetic studies were performed in eight of ten patients with B-cell chronic lymphocytic leukemia presenting with trisomy 12 as the sole chromosomal abnormality. Follow-up studies of peripheral blood lymphocytes revealed that the karyotypes retained the sole abnormality of trisomy 12 in five cases, trisomy 12 converted to a normal karyotype during remission in one case, additional chromosome changes (-X,14q-) along with trisomy 12 appeared in one patient and multiple chromosome changes with or without trisomy 12 appeared in the remaining patient. The findings indicate that other chromosome changes in addition to trisomy 12 may develop as a result of clonal evolution or dedifferentiation, though the possibility that in two patients these changes may be related to chemotherapy and/or irradiation could not be ruled out entirely.

Activation of malignant B-lymphocytes: pathophysiologic and clinical importance

Recent advances in clarifying the activation mechanisms of the normal immune system have provided the basis for successful experiments concerning the activation of malignant lymphocytes. Such studies with malignant cells, freshly sampled from patients with lymphoproliferative diseases, can be used for pathophysiological considerations, analysis of tumor evolution, classification of malignant subsets, and karyotyping. Of particular interest is the possibility of abrogating the maturation arrest in some clonally-restricted cells. This might lead to therapeutical implications, since the differentiation blockage plays a fundamental role in the clonal expansion and pathogenesis of tumors. Recently, it has been shown that interferon (IFN) can be a potent inducer of various degrees of transformation, differentiation and even proliferation in different subsets of normal and malignant B cells. This may be important in explaining the divergent results of IFN treatment in various malignant B-cell disorders.

Simultaneous presence of translocations t(14;18) and t(2;8) in a case of chronic lymphocytic leukemia

We report a patient with classical chronic lymphocytic leukemia of IgM kappa phenotype and a stable clinical course, in which repeated chromosome analyses of blood lymphocytes revealed the coexistence of t(14;18), a marker often associated with follicular low grade lymphocytic lymphomas, and t(2;8), a variant of the t(8;14) typically seen in Burkitt's lymphoma. Both these translocations involve immunoglobulin gene regions, the t(2;8) being almost always found in patients with kappa light chain restriction. However, in an EBV-immortalized cell line of this patient, most karyotypes contained t(14;18) alone, without the t(2;8). This suggests that t(14;18) was the primary cytogenetic event, and that t(2;8) evolved subsequently. As a secondary cytogenetic event, the t(2;8) may not share the grave clinical consequences of a primary t(2;8) as seen in Burkitt's lymphoma and related disorders.

Molecular analysis of the t(2;14) translocation of childhood chronic lymphocytic leukemia

Two rare cases of chronic lymphocytic leukemia (CLL) in children have been studied; both are associated with a previously undescribed chromosomal translocation [t(2;14) (p13;q32)]. In one patient the translocation was reciprocal and the breakpoint on chromosome 14 occurred just 5' of the C gamma 2 region on the productive immunoglobulin heavy-chain allele. The breakpoint on chromosome 2 does not involve the K locus but lies within an uncharacterized region that coincides with the position of a constitutive fragile site that occurs within normal lymphocytes. Data on the second patient are consistent with these findings and suggest that these cases represent a rare but distinct subgroup of CLL's with a specific cytogenetic change.

Trisomy 12 in B cells of patients with B-cell chronic lymphocytic leukemia

Trisomy 12 is the most frequently reported chromosome abnormality in patients with B-cell chronic lymphocytic leukemia, but only normal karyotypes are found in one third of patients with that disorder. Moreover, samples from patients with trisomy 12 also have many normal metaphases. To identify immunologically the cells in which both the trisomy 12 and the normal karyotypes occur, we studied two patients with B-cell chronic lymphocytic leukemia--one whose neoplastic cells demonstrated lambda light-chain clonality and one whose cells had kappa light-chain clonality. We used a recently developed cytogenetic method that allows simultaneous analysis of cell morphology, immunologic phenotype, and karyotype in the same mitotic cell. In cultures of blood cells stimulated with pokeweed mitogen and tetradecanoylphorbol acetate, all the mitotic cells with either the lambda or the kappa immunoglobulin had trisomy 12, whereas all the cells that lacked these light chains or that had T-cell markers (OKT8 or OKT4) had normal karyotypes. These results show that trisomy 12 in B-cell chronic lymphocytic leukemia occurs in the neoplastic B cells, but not in the T cells, and they thus provide an explanation for the common finding of mitoses with normal karyotypes in patients with B-cell chronic lymphocytic leukemia.

Chromosomal abnormalities in lymphoma and their correlations with nucleic acid flow cytometry

Cytogenetic studies were performed on 25 samples obtained from 25 patients with lymphoma. Fourteen of these were also simultaneously studied with nucleic acid flow cytometry to determine percent S-phase and DNA content (ploidy). In 17 cases (68%), evaluable metaphases were obtained. The evaluable metaphase rate was higher in previously untreated patients (15/19 or 79%). All but two cases showed abnormal karyotype. All five cases showing either the t(8;14) or t(8;22) abnormality were associated with extremely high percent S-phase values, ranging from 36% to 47%, which is in the range of high-grade lymphomas according to our previous experience. Four of these cases were diagnosed as Burkitt's lymphoma and one as diffuse large cell lymphoma. Further review of this latter case resulted in the pathologic diagnosis being changed to Burkitt's lymphoma. Three patients had either numerical or structural abnormalities of chromosome #21 [two cases of extra chromosomes and one i(21q)]. All three cases were diagnosed as diffuse large cell lymphoma. Four instances of trisomy 12 were identified. Only one of these was diagnosed as diffuse well-differentiated lymphocytic lymphoma. The remaining three were Burkitt's lymphoma in two and diffuse large cell lymphoma in one. Two instances of t(14;18) were observed. This is the characteristic abnormality of follicular lymphomas. One of these cases was a follicular large cell lymphoma. The second case had possibly originated from a follicular mixed lymphoma and had evolved into a diffuse mixed cell type. Both of these cases had low S-phase values in the range of low-grade lymphomas. The correlation between ploidy as determined by flow cytometry and cytogenetic analysis was good whenever the DNA index was elevated. However, when the DNA index was 1.0 (diploid), concordant measurements were observed in only five of eight cases. Flow cytometry detected one instance of clearly abnormal ploidy, which was thought to be diploid by cytogenetics. This case most likely represents a "false negative" cytogenetic determination.

The most common chromosome change in 86 chronic B cell or T cell tumors: a 14q32 translocation

Among 46 patients with chronic lymphocytic leukemia (CLL) (40 B cell, 6 T cell) and 40 patients with cutaneous T cell lymphoma (CTCL), a chromosomally abnormal neoplastic clone was identified in 43 cases. A translocation involving 14q32 was present in nine cases (five B-CLL, two T-CLL, two CTCL). The donor chromosomal site was 11q13 in four patients and 1q12, 4q25-27, 17q21-22, 18q21, and 22q11 in one case each. The next most frequent abnormalities were rearrangements involving 6q21-23 (four cases), and trisomy 12 (four cases, all B-CLL). In one CTCL patient, the t(11;14) translocation was present in one of three apparently unrelated T cell clones. Recent studies indicate that the selective advantage conferred by the 14q+ chromosome in B cell neoplasms appears to result from an oncogene being brought adjacent to a rearranged and transcriptionally active immunoglobulin heavy chain locus. The present findings suggest that similar mechanisms may operate in certain T cell neoplasms, although the activating gene is not necessarily the same.