Association of bcl-2, bax, bcl-xL and interleukin-1 beta-converting enzyme expression with initial response to chemotherapy in acute myeloid leukemia.

Bcl-2 expression is able to confer drug resistance to chemotherapy-induced programmed cell death. Bax, a partner protein of bcl-2 with extensive aminoacid homology, is a promoter of apoptosis. Apparently the equilibrium of bcl-2 and bax hetero- and homodimers is important for the susceptibility of cells for stimuli inducing apoptosis. In this study we determined the role of bcl-2 to bax expression ratio, bcl-xL and ICE expression level for predicting clinical response to chemotherapy in acute myelold leukemia (AML). Bone marrow samples from 14 patients with AML were examined using an immunophosphatase staining method. Initial bone marrow blast portion was over 80% in all cases. Clinical response was defined by bone marrow aspiration 4 weeks after treatment initiation. There was a significant correlation between bcl-2 to bax expression ratio and clinical response (P < 0.005). No patients with a bcl-2/bax ratio >1.0 achieved complete remission after induction therapy. No significant correlation between bcl-2- and p-glycoprotein-expression was observed in this group. Conversely a high expression of ICE indicated a good clinical response (P < 0.01), whereas expression of bcl-xL had no influence on therapeutic success in this group.

Bcl-2, bax and bcl-xL expression in human sensitive and resistant leukemia cell lines.

With the growing understanding of cytostatic drug-induced programmed cell death new drug-resistance mechanisms based on the altered ability of cells to die by apoptosis have been defined. At first, the sensitive and P-glycoprotein (P-gp)-related resistant cell lines were tested to induce apoptosis by a non-P-gp transported drug, such as cytosine arabinoside (ara-C). It was demonstrated that ara-C induces apoptosis in sensitive as well as in P-gp-related resistant cell lines, as expected. Furthermore, the role of bcl-2 and bcl-xL apoptosis inhibitors as well as bax expression (apoptosis inducer) in human sensitive leukemic cell lines (CCRF-CEM and HL-60) as compared to their resistant variants such as CCRF-CEM/ACT400, CCRF-CEM/VCR1000, HL-60/IDA40, HL-60/DNR250 was evaluated. In addition to the P-gp-related resistance, a possible multidrug resistance-associated protein (MRP) and the lung resistance protein (LRP)-related resistance were assessed by flow cytometry using the monoclonal antibodies 4E3.16, MRPr1 and LRP56. Furthermore, the function of P-gp was determined with the rhodamine-123 (R-123) accumulation test. Bcl-2 and bax were analyzed by both flow cytometry and ECL Western blot, bcl-xL by ECL-Western blot alone. Comparison of the two sensitive cell lines demonstrated different bcl-2, bax and bcl-xL patterns. The common characteristic was the increased expression of one of the apoptosis inhibitor proteins, such as bcl-2 or bcl-xL. The sensitive CCRF-CEM showed a high bax level, where a decrease of about 75% in resistant variants was measured. Compared to their sensitive counterpart HL-60, a low bax expression was analyzed, which increased in the resistant variant. The common characteristic of all resistant cell lines was the decreased expression of bax compared to bcl-2 or bcl-xL. In the P-gp-related resistant HL-60/DNR250 only an increase in bcl-xL was seen, whereas in the LRP-expressing as well as P-gp and MRP negative resistant HL-60/IDA40 both apoptotic inhibitor proteins bcl-2 and bcL-xL showed maximum increase, compared to the other resistant cell lines. The P-gp-related resistant cell lines CCRF-CEM/ACT400 and CCRF-CEM/VCR1000 also showed an increased expression of both bcl-2 and bcl-xL. Summarizing these results, it was shown that the examined sensitive human leukemic cell lines and their resistant variants demonstrated a different pattern of markers for preventing and promoting apoptosis. An association between P-gp and possible LRP-expressing leukemic cells as well as apoptosis-preventing markers (bcl-2, bcl-xL) seems to exist. The clinical relevance of the coexpression of various resistance mechanisms remains to be confirmed in large leukemia patient groups.

Functional P-gp expression in multiple myeloma patients at primary diagnosis and relapse or progressive disease.

In this study, 25 multiple myeloma (MM) patients at primary diagnosis and 18 MM patients at relapse or progressive disease (PD) were examined in order to investigate the incidence of P-glycoprotein (P-gp) expression at initial diagnosis and relapse or PD. Furthermore, P-gp expression in relation to VAD regimen response was determined. P-gp expression in the myeloma cells was determined using monoclonal antibody 4E3.16 and the rhodamine 123 functional test. The percentage of patients with P-gp overexpression at primary diagnosis ranged between 0 and 41% in the literature vs 32% in our study. The percentage of P-gp positive patients at relapse or PD ranged between 29 and 59% in the literature vs 33% in this analysis. All P-gp positive patients had a functional P-gp, ie a pumping P-gp. A significant difference concerning response (50 vs 58.3%) to VAD treatment and median survival (10 vs 12.5 months) between P-gp positive and P-gp negative patients could not be determined. Six of 12 P-gp negative MM patients at relapse or PD developed after VAD therapy a relapse combined with P-gp overexpression. These results do not confirm the suggestions that P-gp overexpression influences response to VAD treatment. However, the results described in the literature and our own emphasize the need for careful accompanying research programmes aimed at detecting the complexity of chemotherapy resistance in the light of developing a risk-adapting therapy for MM patients.

P-glycoprotein expression in patients with acute leukemia-clinical relevance.

P-glycoprotein (P-gp) is a crucial factor in the development of chemotherapy resistance in malignant disorders. Between 1989 and 1995, P-gp expression was studied in bone marrow blast cells of 322 (239 AML; 83 ALL) acute leukemia patients. 166 AML patients with the AML-6 protocol (EORTC), containing daunorubicin, vincristine and conventional-dose cytarabine (ara-C), and 63 AML patients treated with intermediate-does Ara-C plus amsacrine. Further 71 ALL patients were treated according to a German standard polychemotherapy protocol (BMFT04/1989). P-gp was determined by using monoclonal antibodies C219 and 4E3, and the cutoff point for P-gp overexpression was set at >/= 10%. A significant (P < 0.06) difference in P-gp overexpression was demonstrated between AML (21.6%) and ALL (10.2%) patients at primary diagnosis and between primary diagnosis and relapse/refractoriness in AML (21.6%; 51.0%) and ALL (10.2%; 27.2%) patients. According to FAB classification P-gp overexpression was detected in AML patients significantly (P < 0.05) more frequently in classes M4, M5a and M5b and less frequently in M3, as compared to other types. For AML patients with P-gp overexpression at primary diagnosis or early relapse/refractoriness, the predictive value for nonresponse to the AML-6 protocol was 91 and 95%, respectively, while late-relapsed AML patients with P-gp overexpression had a significantly (P < 0.05) lower predictive value of 73% for nonresponse. Additionally, in refractory and late-relapsed P-gp--overexpressing AML patients treated with intermediate-dose ara-C plus amsacrine the predictive values for nonresponse were 44 and 39%, respectively, significantly (P < 0.05) lower as compared to AML-6 protocol-treated refractory or late-relapsed AML patients. In P-gp-overexpressing treated ALL patients the predictive values of 50 and 55% for non-response were calculated at primary diagnosis and late relapse, respectively. We conclude that P-gp overexpression is a common phenomenon in AML patients at primary diagnosis or relapse, has an inverse influence on AML-6 treatment outcome and should be taken into consideration in the development of new therapy strategies.

Drug-induced apoptosis in chronic lymphocytic leukemia.

Glucocorticoids and fludarabine are able to induce typical features of apoptosis in CLL lymphocytes. Cysteinyl aspartate specific proteases (caspases) play a key biochemical role in the apoptotic pathway. Caspase activation following cytotoxic stimuli leads to highly specific proteolytic cleavage of functionally important cellular enzymes. One of them is poly ADP-ribose) polymerase (PARP). To some extent caspase activation seems to be under the control of the Bcl-2 family of interacting proteins. We determined the role of Bcl-2-family proteins Bcl-2 (anti-apoptotic) and Bax (pro-apoptotic), activation of caspase-3 (CPP32/Yama) and activation of PARP in CLL apoptosis. All 21 analyzed CLL samples expressed Bcl-2 and Bax. Four of 13 (31%) samples with a low Bcl-2/Bax ratio exhibited in vitro prednisolone resistance, whereas eight of nine (88%) samples with a high Bcl-2/Bax ratio were in vitro resistant (

In vitro efficacy of known P-glycoprotein modulators compared to droloxifene E and Z: studies on a human T-cell leukemia cell line and their resistant variants.

P-glycoprotein(P-gp)- related resistance is one of the major obstacles in treating leukemia patients. Therefore, it is of clinical interest to find new potential modulators and compare their P-gp-modulating efficacy. The present analysis investigated the influence of P-gp modulators, such as verapamil, tamoxifen, droloxifene E, droloxifene Z, SDZ PSC 833 (PSC 833) and dexniguldipine in a leukemic T-cell line (CCRF-CEM) and its P-gp-resistant counterparts (CCRF-CEM/ACT400 and CCRF-CEM/VCR1000). P-gp expression was assessed with an immunocytological technique using the monoclonal antibody 4E3.16. It was characterized as the percentage of P-gp positive cells and also expressed as a D value by using the Kolmogorov Smirnov statistic. The efficacy of P-gp modulators was determined with the rhodamine-123 accumulation test and the MTT test. An in vitro modulator concentration between 0.1 microM and 3 microM was determined, where no genuine antiproliferative effect was apparent. The modulators PSC 833 and dexniguldipine were the significant (p

Expression and functional activity of P-glycoprotein in adult acute myelogenous leukemia patients.

Expression and functional activity of P-glycoprotein (P-gp) were measured in 182 acute myelogenous leukemia (AML) patients: 136 patients were treated with the AML-6 protocol (EORTC), containing daunorubicin, vincristine, and conventional-dose cytarabine (ara-C), and 21 patients received idarubicin, vepeside, and conventional-dose ara-C (ICE-AML-10 protocol/EORTC). An additional 25 patients were treated with a dose of idarubicin and ara-C, modified as compared with the ICE protocol, but with the same dose of etopside (ICE-I protocol). P-gp was determined using monoclonal antibody 4E3.16 and functional activity using the rhodamine 123 accumulation test. P-gp positivity was defined as a Kolmogorov Smirnov (KS) D value > or = 0.15, P-gp negativity as a KS D value < 0.15. P-gp activity was defined as a ratio of mean rhodamine 123 accumulation with/without verapamil. In AML patients at primary diagnosis and early relapse/refractoriness a significant (p < 0.05) difference between P-gp-positive and P-gp-negative patients was ascertained using the AML-6 protocol; the difference corresponded to the complete remission rate. For ICE- and ICE-I-treated AML patients at primary diagnosis this significance was not shown. Compared with AML patients at primary diagnosis and patients at early relapse or refractoriness, a significantly (p < 0.05) increased incidence of non-pumping P-gp and a trend (p = 0.054) to a higher percentage of non-P-gp-related mechanisms in AML patients at late relapse was determined. When the AML-6 protocol is used, age, activated P-gp, and CD34 expression are independent prognostic factors in AML patients. A test system which determines a functional P-gp overexpression is a major tool for identifying a group of AML patients with a poor prognosis. In order to effectively use so-called P-gp modulator substances, the degree of P-gp expression, the activated or nonactivated P-gp condition, and detection of non-P-gp-related resistance mechanisms are of utmost interest for optimal design and analysis of P-gp modulator trials and for understanding the complexity of chemotherapy-related resistance mechanisms in patients.

Clinical importance of P-glycoprotein-related resistance in leukemia and myelodysplastic syndromes--first experience with their reversal.

P-glycoprotein (P-gp) expression in mononuclear bone marrow cells was analyzed in 119 patients, including 60 with chronic myelogenous leukemia (CML), 48 with myelodysplastic syndromes (MDS), and 11 with acute myelogenous leukemia (AML). For P-gp measurement an immunocytological method using monoclonal antibodies C219, 4E3, and MRK 16 and the reverse transcription-polymerase chain reaction technique were applied. According to our results obtained in healthy volunteers using the immunocytological method, the limit for P-gp overexpression was set at > or = 10% P-gp-positive mononuclear bone marrow cells and at > or = 30% P-gp-positive mononuclear peripheral blood cells. All 42 CML patients in chronic phase had normal P-gp expression. P-gp overexpression was demonstrated in four of six patients in accelerated myelogenous blast cell phase and in four of 12 CML-BC patients. Of eight CML patients in blast crisis (BC) with normal P-gp expression, partial remission was achieved in three and minor response in five after prednisone/vindesine therapy. All four of the 12 CML-BC patients with P-gp overexpression did not respond to this therapy. Normal P-gp expression was seen in 41 (85.4%) of 48 untreated MDS patients. While P-gp overexpression did not develop during therapy in any of the myelodysplastic syndrome patients treated with low-dose ara-C alone, four of eight treated with low-dose ara-C plus GM-CSF and four of 11 treated with low-dose ara-C and IL-3 developed P-gp overexpression after therapy. Furthermore, 11 AML patients at primary diagnosis, including five AML patients with P-gp overexpression, who were treated with idarubicin, vepesid, and cytarabine V (ara-C) showed a complete remission. Additionally, one daunorubicin-cytarabine-pretreated refractory AML patient was treated with the oral form of the P-gp modulator drug dexniguldipine and achieved complete remission for a duration of 7 months. Our results suggest that in CML patients in BC, P-gp expression influences outcome after therapy. Further more, studies in a larger series of patients are necessary to prove the efficacy and toxicity of idarubicin/vepesid and cytardbine--or dexniguldipine-containing--therapy in relation to P-gp expression of AML patients.

Idarubicin monotherapy in multiply pretreated leukemia patients: response in relation to P-glycoprotein expression.

The aim of the study was to test whether fractionated (weekly) idarubicin administration to multiply pretreated leukemia patients is effective and tolerable for outpatient treatment, and whether idarubicin alone can overcome P-glycoprotein (P-gp)-related resistance. P-gp was assessed with an immunocytological technique using the monoclonal antibody 4E3.16. P-gp. expression was characterized as a percentage of P-gp-positive blasts. Additionally, the function of P-gp was determined with the rhodamine-123 (R-123) accumulation test in combination with or without verapamil and expressed as the R123 accumulation ratio. Fractionated idarubicin (12 mg/m2/week) was given to 36 acute myelogenous leukemia (AML) patients, 12 acute lymphoblastic leukemia (ALL) patients, and eight chronic myelogenous leukemia (CML) patients in blast crisis. Furthermore, 11 AML and four ALL patients were treated with fractionated daunorubicin at a dose of 50 mg/m2/week. All patients had been pretreated with drugs inducing P-gp-related resistance including daunorubicin and/or doxorubicin or vindesine (CML patients). Of 71 pretreated patients, 51 (72%) had a P-gp value between 25 and 98%. Six of these patients with increased P-gp expression had a nonpumping P-gp; four of them were CD34 positive. Of 51 patients with increased P-gp expression, 30 (59%) were CD34 positive. With regard to idarubicin monotherapy, overall response was 33/56 (59%) patients, and 23/33 (70%) responding patients showed a P-gp expression between 25 and 95%. All idarubicin-responding patients with high P-gp expression before treatment showed a clear reduction of P-gp-positive blasts. No patients with P-gp expression between 34 and 85% treated with fractionated daunorubicin showed response or reduction of P-gp-positive blasts in bone marrow. This study demonstrates that P-gp-related resistance can be overcome in multiply pretreated leukemia patients with idarubicin alone, and that the protocol used here is tolerable for outpatient treatment.