Biomedical subjects

I W Flinn

Publications and source records attributed to I W Flinn.

At least 19 recordsLinked to original sources

PubMed2005

Filgrastim and alemtuzumab (Campath-1H) for refractory chronic lymphocytic leukemia.

Alemtuzumab (anti-CD52; Campath-1H) is effective in fludarabine-refractory chronic lymphocytic leukemia (CLL), but is associated with infection and early onset neutropenia. To reduce toxicity, filgrastim (G-CSF) was administered concurrently with alemtuzumab. In total, 14 CLL patients (median age 59) with a median of 3.5 prior regimens (range 1--12) received i.v. alemtuzumab, stepped up from 3 to 30 mg the first week, then 30 mg thrice weekly for 12 weeks. Filgrastim 5 microg/kg was administered daily 5 days before and throughout alemtuzumab therapy. Six patients developed cytomegalovirus (CMV) reactivation 3--6 weeks into treatment; six patients developed fever, three neutropenia, and one pneumonia. The patient with CMV pneumonia died; ganciclovir cleared CMV in the other patients. Five patients developed early neutropenia (weeks 2--5). Four patients developed delayed neutropenia (weeks 10--13) unassociated with CMV reactivation. Nine patients ceased therapy because of infectious and hematologic toxicity. Five partial responses were noted, all in patients with lymph nodes>cm, lasting a median of 6.5 months (range 5--13). Filgrastim and alemtuzumab were given concurrently with manageable infusion toxicity and clinical activity, but the efficacy of this regimen was limited by delayed neutropenia of unclear etiology and CMV reactivation. Filgrastrim should not be administered prophylactically during alemtuzumab therapy outside clinical trials.

Aged↗

PubMed2001

Long-term results of blood and marrow transplantation for Hodgkin's lymphoma.

PURPOSE: To evaluate the long-term outcome after allogeneic (allo) and autologous (auto) blood or marrow transplantation (BMT) in patients with relapsed or refractory Hodgkin's lymphoma (HL). PATIENTS AND METHODS: We analyzed the outcome of 157 consecutive patients with relapsed or refractory HL, who underwent BMT between March 1985 and April 1998. Patients <or= age 55 with HLA-matched siblings were prioritized toward allo BMT. The median age was 28 years (range, 13 to 52 years) for the 53 allo patients and 30.5 years (range, 11 to 62 years) for the 104 auto patients. RESULTS: The median follow-up after BMT for surviving patients was 5.1 years (range, 1 to 13.8 years). For the entire group, the probabilities of event-free survival (EFS) and relapse at 10 years were 26% (95% confidence interval [CI], 18% to 33%) and 58% (95% CI, 48% to 69%), respectively. According to multivariate analysis, disease status before BMT (sensitive relapse if responding to conventional-dose therapy or resistant disease if not) (hazard ratio [HR] = 0.39, P < .0001) and date of BMT (HR = 0.93, P = .004) were independent predictors of EFS, whereas only disease status (HR = 0.35, P < .0001) influenced relapse. There was a trend for probability of relapse in sensitive patients to be less after allo BMT at 34% (range, 8% to 59%) versus 51% (range, 36% to 67%) for the auto patients (HR = 0.51, P = .17). There was a continuing risk of relapse or secondary acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) for 12 years after auto BMT, whereas there were no cases of secondary AML/MDS or relapses beyond 3 years after allo BMT. CONCLUSION: There seems to be a clinical graft-versus-HL effect associated with allo BMT. Allo BMT for HL also seems to have a lower risk of secondary AML/MDS than auto BMT. Thus, allo BMT warrants continued study in HL.

Adolescent↗

PubMed2001

Rituximab using a thrice weekly dosing schedule in B-cell chronic lymphocytic leukemia and small lymphocytic lymphoma demonstrates clinical activity and acceptable toxicity.

PURPOSE: Rituximab has been reported to have little activity in small lymphocytic lymphoma (SLL)/chronic lymphocytic leukemia (CLL) and to be associated with significant infusion-related toxicity. This study sought to decrease the initial toxicity and optimize the pharmacokinetics with an alternative treatment schedule. PATIENTS AND METHODS: Thirty three patients with SLL/CLL received dose 1 of rituximab (100 mg) over 4 hours. In cohort I (n = 3; 250 mg/m(2)) and cohort II (n = 7; 375 mg/m(2)) rituximab was administered on day 3 and thereafter three times weekly for 4 weeks using a standard administration schedule. Cohort III (n = 23; 375 mg/m(2)) administered rituximab similar to cohort II for the first two treatments and then over 1 hour thereafter. RESULTS: A total of 33 CLL/SLL patients were enrolled; only one patient discontinued therapy because of infusion-related toxicity. Thirteen patients developed transient hypoxemia, hypotension, or dyspnea that were associated with significant changes in baseline interleukin-6, interleukin-8, tumor necrosis factor alpha, and interferon gamma compared with those not experiencing such reactions. Infusion-related toxicity occurred more commonly in older (median age 73 v 62 years; P =.02) patients with no other pretreatment clinical or laboratory features predicting occurrence of these events. The overall response rate was 45% (3% CR, 42% PR; 95% CI 28% to 64%). Median response duration for these 15 patients was 10 months (95% CI, 6.8-13.2; range, 3 to 17+). CONCLUSION: Rituximab administered thrice weekly for 4 weeks demonstrates clinical efficacy and acceptable toxicity. Initial infusion-related events seem to be cytokine mediated and resolve by the third infusion making rapid administration possible. Future combination studies of rituximab with other therapies in CLL seem warranted.

Aged↗

PubMed2001

Gemcitabine demonstrates in vitro activity against human B-cell chronic lymphocytic leukemia.

B-cell chronic lymphocytic leukemia (CLL) is the most common type of leukemia diagnosed in the Western Hemisphere and remains incurable with currently available therapy. In an attempt to identify new potential therapy for CLL, we explored the pre-clinical activity of gemcitabine in human B-CLL cells (n =11). Mononuclear cell isolates were exposed to varying concentrations of gemcitabine (0.01-100 microM) for 4, 24, and 96 h. Viability, as determined by the tetrazolium salt (MTT) assay, after a 4 h incubation with gemcitabine declined in 6 of 8 (75%) evaluable patients at a concentration < 30 microM (a physiologically attainable level), and 3 of 8 of the B-CLL cells had an LC50 (concentration where 50% loss of viability is observed) < 30 microM. At 4 days of drug exposure, 82% (9/11) of patients had an LC50 < 30 microM. Annexin-V/propidium iodine staining demonstrated apoptosis in CLL cells exposed to 30 microM of gemcitabine. Examination of changes in apoptosis related proteins demonstrated no significant change in bcl-2, bax or p53 protein expression with gemcitabine (23 microM) at 4, 24, or 48 h. These data demonstrate that gemcitabine has pre-clinical activity in B-CLL and supports its exploration as a single agent and in combination with other active agents in this disease.

Antimetabolites, Antineoplastic↗

PubMed2001

UCN-01 induces cytotoxicity toward human CLL cells through a p53-independent mechanism.

OBJECTIVES: UCN-01, a novel protein kinase C inhibitor, is currently being tested in phase I clinical trials after being noted to induce apoptosis in lymphoid cell lines. We sought to study the in vitro activity of UCN-01 against human chronic lymphocytic leukemia (CLL) cells and potential mechanisms of action for inducing this cytotoxicity. METHODS: Detailed in vitro studies were performed from tumor cells derived from patients with CLL cells following attainment of written informed consent. RESULTS: The 50% loss of viability (LC(50)) in mononuclear cells from CLL patients (n = 10) following exposure to UCN-01 for 4 days was 0.4 microM (95% CI +/- 0.21; range 0.09-1.16). Loss of viability in human CLL cells correlated with early induction of apoptosis. Exposure of CLL cells to 0.4 and 5.0 microM of UCN-01 resulted in decreased expression of p53 protein. We therefore investigated the dependence of UCN-01 on intact p53 by exposing splenocytes from wild-type (p53(+/+)) and p53 null (p53(-/-)) mice, which demonstrated no preferential cytotoxicity when compared to the marked differential induced by F-Ara-A and radiation. CONCLUSIONS: UCN-01 has significant in vitro activity against human CLL cells that appears to occur independent of p53 status. While demonstration of in vitro cytotoxicity does not establish in vivo efficacy, the findings described support the early introduction of UCN-01 into clinical trials for patients with B-CLL.

Alkaloids↗

PubMed2001

Allogeneic bone marrow transplantation in patients with sensitive low-grade lymphoma or mantle cell lymphoma.

PURPOSE: To report survival outcomes of allogeneic BMT in patients with low-grade lymphoma or mantle cell lymphoma (MCL). PATIENTS AND METHODS: Thirty-five patients with low-grade lymphoma (48%), chronic lymphocytic leukemia (26%), or MCL (26%) underwent myeloablative allogeneic BMT from HLA-identical siblings at the Johns Hopkins Oncology Center. Patients had a median age of 46 years, a median of 2 prior treatments, and 31% were in complete remission at the time of transplantation. The preparative regimen was cyclophosphamide/total body irradiation for most patients. All grafts were T-cell depleted by counter flow centrifugal elutriation with CD34+ augmentation. RESULTS: The incidence of acute GVHD grade >2 was 6% and of grades 1 to 2 was 37%. The incidence of chronic GVHD was 6%. The median follow-up time was 25 months. The rate of event-free survival (EFS) was 50% (95% confidence interval [CI], 33%-66%). Only 1 patient relapsed. The transplantation-related mortality (TRM) was 46% for all patients. The TRM was 86% for patients with resistant disease and 14% for patients with sensitive disease and <2 prior treatments; rates of EFS were 0% (95% CI, 0%-0%) and 79% (95% CI, 47%-93%), respectively. CONCLUSION: These data show that, with T-cell depletion, the TRM and relapse rates are modest for patients with sensitive disease and <2 prior treatment courses. Thus, if there is a role for allogeneic BMT in the management of patients with these tumors, it is early in the course of the disease.

Adult↗

PubMed2001

Monoclonal antibodies and autologous stem cell transplantation for lymphoma.

The introduction of monoclonal antibodies into the clinic has paved the way for new approaches to stem cell transplantation for patients with lymphoma. These approaches include the development of new high-dose regimens with radiolabeled antibodies, in vivo purging techniques with the unlabeled antibodies, and post-transplant adjuvant immunotherapy. Numerous trials have demonstrated the feasibility of these approaches. However, questions remain regarding the application of these antibodies including the ultimate efficacy. The recent results of the incorporation of monoclonal antibodies into stem cell transplantation and current research directions are reviewed.

Antibodies, Monoclonal↗

PubMed2001

New approaches to blood and marrow transplantation for patients with low-grade lymphomas.

Low-grade lymphomas are generally considered incurable diseases with current standard therapies. Blood or marrow transplantation may be the exception. Nevertheless, the role of bone marrow transplantation in low-grade lymphomas has been limited by the usual indolent course of this heterogeneous group of diseases and the historically high rates of transplant-related mortality associated with most transplant procedures. This review discusses the current issues pertaining to bone marrow transplantation and comments on investigational approaches such as the use of monoclonal antibodies as in vivo purging mechanisms and nonmyeloablative and radioimmunoconjugated antibodies as alternate preparative regimens.

Antibodies, Monoclonal↗

PubMed2000

Characterization of Epstein-Barr virus-infected B cells in patients with posttransplantation lymphoproliferative disease: disappearance after rituximab therapy does not predict clinical response.

Post-transplantation lymphoproliferative disease (PTLD) is associated with Epstein-Barr virus (EBV). Quantitative and qualitative differences in EBV in peripheral blood mononuclear cells (PBMCs) of PTLD patients and healthy controls were characterized. A quantitative competitive polymerase chain reaction (QC-PCR) technique confirmed previous reports that EBV load in PBMCs is increased in patients with PTLD in comparison with healthy seropositive controls (18 539 vs 335 per 10(6) PBMCs, P =.0002). The average frequency of EBV-infected cells was also increased (271 vs 9 per 10(6) PBMCs, P =.008). The distribution in numbers of viral genome copies per cell was assessed by means of QC-PCR at dilutions of PBMCs. There was no difference between PTLD patients and healthy controls. Similarly, no differences in the patterns of viral gene expression were detected between patients and controls. Finally, the impact of therapy on viral load was analyzed. Patients with a past history of PTLD who were disease-free (after chemotherapy or withdrawal of immunosuppression) at the time of testing showed viral loads that overlapped with those of healthy seropositive controls. Patients treated with rituximab showed an almost immediate and dramatic decline in viral loads. This decline occurred even in patients whose PTLD progressed during therapy. These results suggest that the increased EBV load in PBMCs of PTLD patients can be accounted for by an increase in the number of infected B cells in the blood. However, in terms of viral copy number per cell and pattern of viral gene expression, these B cells are similar to those found in healthy controls. Disappearance of viral load with rituximab therapy confirms the localization of viral genomes in PBMCs to B cells. However, the lack of relationship between the change in viral load and clinical response highlights the difference between EBV-infected PBMCs and neoplastic cells in PTLD.

Adult↗

PubMed2000

Long-term follow-up of remission duration, mortality, and second malignancies in hairy cell leukemia patients treated with pentostatin.

The nucleoside analogue, pentostatin, has demonstrated high complete response rates and long relapse-free survival times in patients with hairy cell leukemia, a disease that historically had been unresponsive to treatment. Long-term data on duration of overall survival and relapse-free survival and incidence of subsequent malignancies with this agent are lacking. Patients completing the treatment phase of a randomized, intergroup study who received pentostatin as an initial treatment or who crossed over after failure of interferon alpha were followed for survival, relapse, and diagnosis of subsequent malignancies. Two hundred forty-one patients treated with pentostatin as initial therapy (n = 154) or who crossed over after failure of interferon alpha (n = 87) were followed for a median duration of 9.3 years. Estimated 5- and 10-year survival rates (95% confidence interval) for all patients combined were 90% (87%-94%) and 81% (75%-86%), respectively. In the 173 patients with a confirmed complete response to pentostatin treatment, 5- and 10-year relapse-free survival rates were 85% (80%-91%) and 67% (58%-76%), respectively. Survival curves for patients initially treated with pentostatin and those crossed over were similar. Only 2 of 40 deaths were attributed to hairy cell leukemia. The mortality rate and incidence of subsequent malignancies were not higher than expected in the general population. Pentostatin is a highly effective regimen for hairy cell leukemia that produces durable complete responses. Subsequent malignancies do not appear to be increased with pentostatin treatment.

Adult↗

PubMed2000

Fludarabine and cyclophosphamide with filgrastim support in patients with previously untreated indolent lymphoid malignancies.

To evaluate the response rate and potential toxicities, a phase II trial was conducted of fludarabine and cyclophosphamide with filgrastim support in patients with previously untreated low-grade and select intermediate-grade lymphoid malignancies. Symptomatic patients with preserved end organ function received cyclophosphamide 600 mg/m(2) intravenous (iv) day 1 and fludarabine 20 mg/m(2) iv days1 through 5, followed by filgrastim 5 microg/kg subcutaneous starting approximately day 8. Treatment was repeated every 28 days until maximum response or a maximum of 6 cycles. Sixty patients, median age 53.5 years, were enrolled. Thirty-seven patients with non-Hodgkin lymphoma (NHL) were stage IV and 6 were stage III. Eleven of 17 patients with chronic lymphocytic leukemia (CLL) were Rai intermediate risk and 6 were high risk. The overall complete response (CR) rate was 51% and the partial response (PR) rate was 41%. Of patients with CLL, 47% achieved a CR and the remaining 53% achieved a PR. Of patients with follicular lymphoma, 60% achieved CR and 32% achieved a PR. Although the toxicity of this regimen was mainly hematologic, significant nonhematologic toxicities, including infections, were seen. Twenty-four patients subsequently received an autologous or allogeneic stem cell transplant. Engraftment was rapid, and there were no noticeable procedure toxicities in the immediate posttransplant period attributable to the fludarabine and cyclophosphamide regimen. Fludarabine, cyclophosphamide, and filgrastim make up a highly active and well-tolerated regimen in CLL and NHL.

Adult↗

PubMed2000

Application of the ELISPOT assay to the characterization of CD8(+) responses to Epstein-Barr virus antigens.

CD8(+) cells have an important role in controlling Epstein-Barr virus (EBV) infection. We adapted the interferon-gamma ELISPOT assay to the quantitative analysis of EBV-specific CD8(+) cells. Using peripheral blood mononuclear cells (PBMCs) from healthy donors, we measured both the aggregate response to the virus, using EBV-transformed lymphoblastoid cell lines (LCLs) as stimulators, and the specific responses to 2 A2-restricted peptide epitopes: the subdominant latency membrane protein-2 (LMP2) peptide CLGGLLTMV and the early lytic BMLF1 peptide GLCTLVAML. LCL-responsive CD8(+) cells were detected in all EBV-seropositive donors (range 954 to 37 830 spots/10(6) CD8(+) cells). LMP2 peptide-responsive CD8(+) cells were detected in 10 of 11 healthy seropositive A2 donors (range 11 to 83 spots/10(6) PBMC). BMLF1 peptide-responsive CD8(+) cells were detected in all seropositive A2 donors examined (range 13 to 943 spots/10(6) PBMC). Cytotoxic T-lymphocyte (CTL) lines generated with weekly stimulation of LCLs for therapeutic purposes were also studied. Relative to PBMCs, these CTL lines showed a marked increase in the level of LCL-responsive and LMP2 peptide-responsive CD8(+) cells and a lesser degree of expansion of BMLF1 peptide-responsive CD8(+) cells. Finally, we applied the ELISPOT assay to monitor adoptive infusion of EBV CTL lines. In 2 patients examined, a transient increase in LCL-responsive CD8(+) cells could be detected after infusion. Thus, the ELISPOT assay can be applied to the analysis of CD8(+) responses to EBV antigens in PBMCs, in ex vivo expanded CTL lines, and in PBMCs from patients treated with ex vivo expanded CTL lines. (Blood. 2000;95:241-248)

Amino Acid Sequence↗

PubMed2000

Immunotherapy with rituximab during peripheral blood stem cell transplantation for non-Hodgkin's lymphoma.

Peripheral blood stem cell grafts from patients with lymphoma are often contaminated with neoplastic cells. Administration of a lymphoma-specific monoclonal antibody before collecting stem cells may be one way of reducing the contamination. Similarly, an antibody after transplantation at a time of minimal residual disease may increase the efficacy of the procedure. The objective of this study was to determine the safety of using rituximab as both an in vivo purging agent and a posttransplantation adjuvant. Eligible patients with lymphoma received 375 mg/m2 rituximab intravenously IV) on day 1, 2.5 g/m2 cyclophosphamide IV on day 4, and 10 microg/kg per day filgrastim starting on day 5 and continuing until completion of leukapheresis. Patients subsequently received a standard preparative regimen and then received 375 mg/m2 rituximab IV 7 days after platelet independence was achieved. Twenty-five patients (14 men, 11 women; median age, 51 years) were enrolled. Of the 25 patients, 23 received transplants after at least 2.0 x 10(6) CD34+ cells/kg were harvested. As determined with a sensitive polymerase chain reaction assay, 6 of 7 stem cell products tested were free of tumor contamination. All patients engrafted promptly, and the rituximab infusions were well tolerated. Transient neutropenia of uncertain etiology occurred in 6 patients a median of 99.5 days post-transplantation. An additional patient developed progressive pancytopenia. Rituximab used as an in vivo purging agent and adjuvant immunotherapy with peripheral blood stem cell transplantation for non-Hodgkin's lymphoma is a well-tolerated regimen. However, the ultimate determination of efficacy will require the results of ongoing studies.

Adult↗

PubMed2000

A dose-finding study of liposomal daunorubicin with CVP (COP-X) in advanced NHL.

BACKGROUND: Standard therapy for lymphoma consists of a cyclophosphamide (C), doxorubicin, vincristine (V), and prednisone (P) (CHOP) combination regimen. Liposomal daunorubicin (DaunoXome) is an alternative to doxorubicin for patients with lymphoma because of its more favorable safety profile and potentially more selective uptake in lymphoma. The objectives of this study were to determine the maximum tolerated dose (MTD) of liposomal daunorubucin with CVP (COP-X) and the tolerability of the regimen in patients with indolent lymphoma. PATIENTS AND METHODS: Patients with low-grade and intermediate-grade lymphoma having adequate cardiac, hepatic, and renal function were enrolled. Patients received C 750 mg/m2, V 1.4 mg/m2 (maximum 2.0 mg), and liposomal daunorubicin 50-100 mg/m2 i.v. on day 1 and P 100 mg p.o. on days 1-5. MTD was the liposomal daunorubicin dose associated with 20% dose-limiting toxicity (ANC < 500/mm3 for > 5 days or febrile neutropenia). RESULTS: Twenty patients, median age 59 years, were treated. The liposomal daunorubicin MTD combined with CVP was 70-80 mg/m2, depending on patient population. No significant non-hematologic toxicity occurred. Response rate was 44% (2 complete and 5 partial responses). CONCLUSIONS: A liposomal daunorubicin dose of 80 mg/m2 in the COP-X regimen was well tolerated with little nonhematologic toxicity.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2000

Theophylline, pentostatin (Nipent), and chlorambucil: a dose-escalation study targeting intrinsic biologic resistance mechanisms in patients with relapsed lymphoproliferative disorders.

In spite of the chemosensitivity seen with the initial treatment of malignant lymphoid disorders, relapse is common and death most often occurs as a result of disease progression. This is related to a multitude of resistance mechanisms associated with the various lymphoproliferative disorders. As a result, therapies targeting intrinsic drug-resistance mechanisms are evolving and have become an active area of research. In vitro studies of human chronic lymphocytic leukemia cells incubated with theophylline, a phosphodiesterase inhibitor, resulted in downregulation of bcl-2 concomitant with induction of apoptosis. We describe the preclinical basis for a novel combination therapy involving pentostatin (Nipent; SuperGen, San Ramon, CA), chlorambucil, and theophylline in the treatment of patients with relapsed chronic lymphoproliferative disorders. An ongoing study based on such justification, which is currently accruing patients, is also described. Results from this trial appear promising, and a phase II study is now being planned.

Antibiotics, Antineoplastic↗

PubMed2000

New approaches to treating malignances with stem cell transplantation.

Stem cell transplantation has been successfully used to treat a wide variety of hematologic malignancies. New and exciting strategies being developed for use in conjunction with transplant will be useful in overcoming tumor resistance. It is now clear that a significant part of the antitumor effect of allogeneic stem cell transplantation is derived from the graft itself and is independent of the preparative regimen. Immune therapy derived from the donor's graft is uniquely suited for killing chemoresistant tumor cells and may prove to be an invaluable tool for decreasing the risk of relapse in patients with advanced disease. Among patients who have relapsed after allogeneic bone marrow transplantation (BMT), an immunologically based antitumor effect may be obtained simply by transfusing T cells obtained by leukopheresis of the original bone marrow donor. Referred to as donor leukocyte infusion (DLI), this technique has been used to obtain complete remissions in relapsed acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), multiple myeloma, non-Hodgkin's lymphoma, myelodysplastic syndrome (MDS), and chronic myeloid leukemia (CML). Another approach that uses the donor's graft to obtain a potent antitumor effect is the combination of nonmyeloablative BMT followed by immunotherapy with DLI. Numerous investigators are exploring ways of combining autologous BMT with immune therapy. Animal studies using tumor vaccines in conjunction with autologous transplantation offer a promising method for eliminating tumor. Patients undergoing autologous transplantation may have marrow that has been contaminated with tumor, which places them at a higher risk of relapse. Attempts have been made to eliminate contaminating tumor from the marrow by purging.

Bone Marrow Purging↗

PubMed1999

Depsipeptide (FR901228): a novel therapeutic agent with selective, in vitro activity against human B-cell chronic lymphocytic leukemia cells.

Therapy of B-cell chronic lymphocytic leukemia (CLL) has been limited by both the nonselectivity of therapeutic agents toward normal residual immune cells and inherent drug resistance. Identification of agents that spare normal immune effector cells, thus facilitating addition of immune-based therapies, and that modulate factors associated with drug resistance in CLL might represent a major therapeutic advance. Depsipeptide (FR901228) is a novel agent entering clinical trials that has selective in vitro activity against resistant leukemia cell lines. To assess its in vitro activity in CLL, we exposed peripheral mononuclear cells from CLL patients (n = 10) to varying concentrations of this agent. Viability of the CLL cells was reduced by 50% (LC(50)) at 4 hours, 24 hours, and 4 days at depsipeptide concentrations of 0.038, 0.024, and 0.015 micromol/L, respectively. Depsipeptide had marked selective cytotoxicity when compared with normal blood mononuclear cells, in which the LC(50) was 3.44 micromol/L at 4 hours (P =.03), 0.965 micromol/L at 24 hours (P =.01), and 0.0318 micromol/L at 96 hours (P =.04). Inhibition of bone marrow progenitor cell growth was also minimal after incubation with 0.015 micromol/L (19% inhibition of colony forming unit-granulocyte-macrophage [CFU-GM]; 17% inhibition burst forming unit-erythroid [BFU-E]) and 3.44 micromol/L (24% inhibition of CFU-GM; 57% inhibition BFU-E) of depsipeptide for 4 hours, followed by a 14-day incubation period. Expression of apoptotic proteins after depsipeptide exposure (0.015 micromol/L) included no change in bcl-2, elevation of bax, and decreased expression of p27. These data demonstrate that depsipeptide has significant selective in vitro activity against human CLL cells concurrent with favorable alterations of the bcl-2:bax protein ratio and decrease in p27 expression. Such findings strongly support the early introduction of depsipeptide into clinical trials for patients with CLL.

Anti-Bacterial Agents↗

PubMed1998

Flavopiridol induces apoptosis in chronic lymphocytic leukemia cells via activation of caspase-3 without evidence of bcl-2 modulation or dependence on functional p53.

Flavopiridol has been reported to induce apoptosis in lymphoid cell lines via downregulation of bcl-2. The in vitro activity of flavopiridol against human chronic lymphocytic leukemia (CLL) cells and potential mechanisms of action for inducing cytotoxicity were studied. The in vitro viability of mononuclear cells from CLL patients (n = 11) was reduced by 50% at 4 hours, 24 hours, and 4 days at a flavopiridol concentration of 1.15 micromol/L (95% confidence interval [CI] +/-0.31), 0.18 micromol/L (95% CI +/-0.04), and 0.16 micromol/L (95% CI +/-0.04), respectively. Loss of viability in human CLL cells correlated with early induction of apoptosis. Exposure of CLL cells to 0.18 micromol/L of flavopiridol resulted in both decreased expression of p53 protein and cleavage of the caspase-3 zymogen 32-kD protein with the appearance of its 20-kD subunit. Contrasting observations of others in tumor cell lines, flavopiridol cytotoxicity in CLL cells did not correlate with changes in bcl-2 protein expression alterations. We evaluated flavopiridol's dependence on intact p53 by exposing splenocytes from wild-type (p53(+/+)) and p53 null (p53(-/-)) mice that demonstrated no preferential cytotoxicity as compared with a marked differential with F-ara-a and radiation. Incubation of CLL cells with antiapoptotic cytokine interleukin-4 (IL-4) did not alter the LC50 of flavopiridol, as compared with a marked elevation noted with F-ara-a in the majority of patients tested. These data demonstrate that flavopiridol has significant in vitro activity against human CLL cells through activation of caspase-3, which appears to occur independently of bcl-2 modulation, the presence of IL-4, or p53 status. Such findings strongly support the early introduction of flavopiridol into clinical trials for patients with B-CLL.

Animals↗