Multidrug resistance phenotype in patients with chronic lymphocytic leukemia as detected by immunofluorescence (FACS) and northern blot analysis

MDR-1 gene polymorphisms G2677T and C3435T in a case of Hodgkin's variant of Richter's syndrome

Richter's syndrome is defined as the transformation of low-grade lymphoma to a more aggressive high-grade malignant form, usually diffuse large B-cell lymphoma. Hodgkin's lymphoma variant of Richter transformation is relatively rare, and only approximately 100 cases have been reported in the literature. This study examined a case of a 53-year-old woman who developed Hodgkin's lymphoma almost 5 years after the diagnosis of chronic lymphocytic leukemia (CLL). The major points of interest regarding CLL with Hodgkin's transformation were also considered, such as the potential role of MDR-1 gene polymorphisms. The patient was evaluated for two MDR-1 gene polymorphisms, G2677T polymorphism in exon 21 and silent C3435T polymorphism in exon 26, to ascertain whether polymorphisms affect the risk of Hodgkin's lymphoma variant of Richter transformation and whether genomic polymorphisms provide prognostic information on the clinical progression of the disease. According to the data obtained, the analysis of polymorphisms in the MDR1 gene exons 21 and 26 revealed that the T2677T and T3435T alleles are not a predisposing factor to Richter transformation, while the presence of the wild-type genotype may be associated with a more favorable response to therapy.

MDR-1 polymorphisms (G2677T and C3435T) in B-chronic lymphocytic leukemia: an impact on susceptibility and prognosis

Patients with B-chronic lymphocytic leukemia present diverse clinical features, genetic abnormalities, variable response to treatment, and heterogeneous prognosis. Novel biological markers such as IgVH mutation, CD38, and ZAP-70 expression have shown to offer important prognostic information. An altered expression of the multidrug resistance 1 may represent an additional prognostic marker. Aim of our study was to evaluate two MDR-1 gene polymorphisms: G2677T polymorphism in exon 21 and C3435T polymorphism in exon 26, to evidence if polymorphisms influence the risk of development of B-CLL and whether genomic polymorphisms provide prognostic information on the clinical progression of the disease. A total of 125 patients with B-CLL and 125 healthy subjects were enrolled in this study. The mutant homozygous 2677 TT genotype was found to be associated with the occurrence of B-CLL and higher T allele frequency in patients with B-CLL when compared with controls was observed (P=0.009). When comparing the prognostic patients' characteristics, patients with 2677 GT genotype were statistically linked to the unmutated IgVH genes (r=0.209, P=0.01). Moreover, the same genotype was correlated with lymphocyte number (r=0.269, P=0.02). Finally for the 2677GT polymorphism, the heterozygous status was associated with higher hemoglobin levels (r=0.247, P=0.005). As far the C3435T MDR1 polymorphism, we were not able to identify any significant correlation with IgVH gene status or other variables. In conclusion, MDR1 gene polymorphism could be a factor predisposing to LLC. Moreover, our findings support the possibility of considering these genomic polymorphisms as prognostic markers in patients with B-CLL.

Hyperforin inhibits P-gp and BCRP activities in chronic lymphocytic leukaemia cells and myeloid cells

We showed previously that hyperforin (HF), a natural phloroglucinol, stimulated apoptosis in B cell chronic lymphocytic leukaemia cells (CLL) and displayed anti-angiogenic properties. In the present work, we investigated the effects of hyperforin on the activity of P-gp/MDR1, an ABC (ATP-binding cassette) transporter putatively involved in multidrug resistance (MDR). Ex vivo treatment of CLL cells with HF markedly impaired the activity of P-gp, as measured by the inhibition of the capacity of the treated cells to efflux the rhodamine 123 probe. In addition, most CLL cells expressed breast cancer resistance protein (BCRP), another ABC transporter. The activity of BCRP was also inhibited by HF, as assessed by the impaired capacity of HF-treated CLL cells to efflux the specific probe mitoxantrone. The capacity of HF to reverse P-gp and BCRP activity was confirmed in myeloid leukaemia cell lines, notably in HL-60/DNR cells selected for their resistance to daunorubicine and overexpressing P-gp. Our results therefore suggest that HF might be of interest in the therapy of CLL and other haematological malignancies through its potential capacity to revert MDR in addition to its pro-apoptotic properties.

MDR-1, but not MDR-3 gene expression, is associated with unmutated IgVH genes and poor prognosis chromosomal aberrations in chronic lymphocytic leukemia

Two P-glycoprotein (P-gp) genes, MDR-1 (ABCB1) and MDR-3 (ABCB4), have been identified in humans. This study was designed to investigate whether associations exist between expression of MDR-1 and MDR-3 P-gp and other markers of poor prognosis and/or prior exposure to therapeutic agents in chronic lymphocytic leukemia (CLL). IgVH mutational status, gene usage, CD38 positivity, FISH analysis and clinical information were available on all patients. Twenty-one of 101 patients tested showed MDR-3 P-gp positivity. Associations with markers of poor prognosis or prior chemotherapy did not reach statistical significance, but MDR-3 P-gp positive patients had significantly shorter survivals than MDR-3 P-gp negative patients. MDR-1 P-gp expression (18/25) showed a strong association with unmutated IgVH genes and adverse prognosis cytogenetics (p = 0.015, p = 0.014, respectively), but was independent of prior exposure to chemotherapeutic agents. These results suggest a role for MDR-1 and MDR-3 in chemoresistant disease. This study highlights the value of determining MDR phenotype in CLL patients prior to treatment, to allow the design of novel drug regimens containing agents that reverse MDR function.

In vitro evaluation of the efficacy of idarubicin in human tumour cells from patients with low-grade non-Hodgkin's lymphoma

Evaluating the potential benefit of the new anthracycline, idarubicin (Ida), in lymphoma, 58 tumour samples from patients suffering from low-grade non-Hodgkin's lymphoma (L-NHL), were analysed in vitro for their sensitivity to 0.5 microg/ml Ida. This was compared with the sensitivity to other anthracyclines (0.5 microg/ml), using the fluorometric microculture cytotoxicity assay. A total of 132 samples from patients with acute leukaemia and a cell-line panel representing different resistance mechanisms was included for comparison. The median cell survival of L-NHL cells did not differ after exposing the cells to Ida or daunorubicin (Dnr), whereas epirubicin, doxorubicin (Dox) and mitoxantrone (Mitox) were significantly less cytotoxic than Ida (P < 0.001). The median cell survival in L-NHL cells did not differ from that of acute leukaemia cells after exposure to 0.5 microg/ml Ida, Dnr, Dox and Mitox. Cells from previously treated patients with L-NHL had a higher median survival than cells from untreated patients after exposure to all drugs, except for Ida. In samples from previously untreated patients, Spearman rank correlations were high (Rho = 0.81-0.90) between cell survival after exposure to Ida and the other anthracyclines. The same pattern was observed in the cell-line panel (Rho = 0.78-0.91) (P < 0.05). In contrast, low correlations (Rho = 0.24-0.42) were observed among samples from previously treated patients. Our results indicate a potential benefit of Ida in previously drug-treated patients with L-NHL.

Multidrug resistance mechanisms in chronic lymphocytic leukaemia

We evaluated the presence of P-glycoprotein (P-gp)-170, multidrug resistance protein (MRP), lung resistance protein (LRP)-56 and Bcl-2 in CD19-positive cells from 100 cases of chronic lymphocytic leukaemia (CLL). P-gp-170 was found in 73% of the CLL cases with no significant difference regarding stage or previous treatment. LRP-56 protein was homogeneously distributed with no differences for stage or treatment. MRP protein was detected at a low level of expression in 49.4% of CLL patients with no differences for stage or treatment. Bcl-2 protein was expressed at a high level in all CLL patients and higher levels were found in the advanced stage. This leads us to conclude that P-gp, MRP, LRP-56 and Bcl-2 are frequently expressed in CLL. P-gp, MRP and LRP are not correlated to stage or previous treatment. Bcl-2 is higher in advanced-stage patients. The clinical and biological significance of these zMDR mechanisms in CLL remains to be fully explained.

Morphological and immunophenotypic features of chronic lymphocytic leukemia

In this review, we summarize the morphological features and immunophenotypic profile of chronic lymphocytic leukemia (CLL) cells, discuss the value of these investigations as front line diagnostic tests, and emphasize their correlation with the clinical features, disease progression, molecular genetics and pathogenesis of CLL. In CLL, the morphology of the circulating cells is characteristic and typical in the majority of cases. However, 15% of patients, either at diagnosis or during the course of the disease, show atypical morphology reflected by either (1) an increased (> 10%) number of circulating prolymphocytes, designated CLL/PL, or (2) an increased (> 15%) number of circulating lymphoplasmacytic and cleaved cells, designated 'atypical' CLL. There is strong evidence of a close association between atypical morphology (CLL/PL) and atypical (CLL) and clinical features, e.g. disease progression, advanced stage and survival, molecular genetics, particularly trisomy 12, but also the rare cases with t(11;14) or t(14;19), p53 abnormalities, unmutated immunoglobulin (Ig) VH genes and origin of the cell (naive, pregerminal center cell). CLL cells have a distinct immunological repertoire different from that of other lymphoproliferative disorders. The typical CLL phenotype is CD5+, CD23+, FMC7-, weak expression of surface Ig (sIg) and weak or absent expression of membrane CD22 and CD79b. The latter marker identifies an extracellular epitope of the B-cell receptor (BCR) beta chain and its weak or absent expression in CLL may derive from the expression of a truncated form. This, together with the low expression of CD22, might explain the abnormal signal transduction of CLL cells similar to that of anergic B lymphocytes. Because no single marker is specific for CLL, a composite phenotype considering this set of 5 or 6 markers compounded into a scoring system helps to distinguish CLL from the other B-cell malignancies. Immunophenotypic analysis has also been shown to be useful for minimal residual disease detection and adds valuable prognostic information because the expression of certain markers, such as FMC7 or CD38, seems to be associated with a poor outcome. In addition, CLL cells express a variety of Bcl-2 family proteins with a profile that favors inhibition of apoptosis which, together with the interaction with microenvironmental (e.g. stromal) cells and the release of cytokines, explains the long life span and subsequent accumulation of CLL cells in various organs. Despite controversies relating to the expression of adhesion molecules (selectins and integrins) in CLL cells, it appears that some of these molecules do play a role in the pathogenesis, biology and clinical patterns of the disease. In conclusion, morphology and immunophenotype are the two essential investigations, which must be carried out in all cases of CLL. Both provide relevant information in terms of diagnosis, course of the disease, prognosis and pathogenesis.

Effect on cell kill of addition of multidrug resistance modifiers cyclosporin A and PSC 833 to cytotoxic agents in chronic lymphocytic leukaemia

Expression of P-glycoprotein (Pgp), the drug efflux pump which mediates multidrug resistance (MDR), has been widely reported in chronic lymphocytic leukaemia (CLL) and improved accumulation of daunorubicin has been reported using the MDR reversing agent cyclosporin A (CSA). We have investigated the effects on cell kill of the addition of CSA and its analogue PSC 833 to daunorubicin, doxorubicin, idarubicin, mitozantrone and fludarabine in samples from 51 patients with CLL using an MTT [3(4,5-dimethylthaizol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Pgp expression was assessed by immunocytochemistry using the JSB-1 monoclonal antibody. Of the 51 samples, 10 (20%) were Pgp positive and all of these samples were from treated patients. With the exception of mitozantrone, the addition of CSA and PSC 833 to cytotoxic agents failed to significantly improve cytotoxicity, even in the Pgp positive group. With mitozantrone significant responses were seen in both Pgp positive and negative groups suggesting that the responses were due to direct cytotoxicity of the cytotoxic-modifier combination rather than reversal of MDR. Both CSA and PSC 833 showed significant direct cytotoxicity (P = 0.004 and 0.04 for PSC 833 at 1000 ng/ml and 500 ng/ml respectively; P < 0.001 for both concentrations of CSA). The responses were disappointing compared to the highly significant improvements in cytotoxicity seen using cells from the Pgp positive CEM VLB 100 acute myeloid leukaemia cell line, and it was not possible to demonstrate the superiority of PSC 833 over CSA which is also seen in cell lines. Our data do not support a role for Pgp modifiers in CLL. Further studies using larger numbers of Pgp positive CLL cells and higher doses of PSC 833 would be useful.

MDR1 and MRP expression in chronic B-cell lymphoproliferative disorders

The role of the MDR1 and MRP genes in drug resistance in patients with chronic lymphocytic leukaemia (CLL)/non-Hodgkin's lymphoma (NHL) is unclear. We hypothesized that any relationship between levels of expression and exposure to P-glycoprotein (P-gp) transportable drugs may become evident by using a measure of gene expression that combined the number of positive cells and the degree of positivity. 68 CLL/NHL patients were analysed using flow cytometry with MDR1 and MRP specific antibodies and were divided into subgroups, untreated (n = 31). treated with non P-gp transportable drugs (n = 26), those treated with low total doses of P-gp transportable drugs (n = 6) and patients treated with high total doses of P-gp transportable drugs (n = 5). The group exposed to high doses of P-gp transportable drugs had higher levels of MDR1 expression when compared to all other groups (P<0.05, ANOVA). A positive correlation between the level of MDR1 expression and the cumulative dose of P-gp transportable drugs was demonstrated (P=0.02). MRP expression was higher in those patients exposed to high doses of P-gp transportable drugs when compared to all other groups (P<0.05. ANOVA), although only a trend towards a linear dose correlation effect could be established (P=0.08). We concluded that MDR1 and MRP are involved in drug resistance but only in patients treated with P-gp transportable drugs.

Chronic lymphocytic leukemia: present status

Chronic lymphocytic leukemia (CLL) is the form of leukemia which occurs most frequently in Western countries. Its etiology is unknown, and no relationship with viruses or genes has been demonstrated. Epidemiological data suggest that genetic and ambiental factors might be of some significance. Clinical features of CLL are due to the accumulation of leukemic cells in bone marrow and lymphoid organs as well as the immune disturbances that accompany the disease. The prognosis of patients with CLL varies. Treatment is usually indicated by the risk of the individual patient, which is clearly reflected by the stage of the disease. In the early stage (Binet A, Rai O) it is reasonable to defer therapy until disease progression is observed. By contrast, because their median survival is less than five years, patients with more advanced stages require therapy. For almost 50 years, no major advances in the management of CLL, which has revolved around the use of alkylating agents, have been made. In recent years, the therapeutic approach in patients with CLL has changed as a result of the introduction of combination chemotherapy regimens and, in particular, purine analogues. The latter are already the treatment of choice for patients not responding to standard therapies, and their role as front-line therapy is being investigated. Bone marrow transplants are also being increasingly used. It is to be hoped that in years to come the outcome of patients with CLL will be improved by these advances.