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J C Byrd

Publications and source records attributed to J C Byrd.

At least 19 recordsLinked to original sources
PubMed2006

Alemtuzumab induces caspase-independent cell death in human chronic lymphocytic leukemia cells through a lipid raft-dependent mechanism.

Alemtuzumab is a humanized IgG1 kappa antibody directed against CD52, a glycosyl-phosphatidylinositol linked cell-membrane protein of unknown function. Herein, we demonstrate that alemtuzumab promotes rapid death of chronic lymphocytic leukemia (CLL) cells in vitro, in a complement and accessory cell free system. Using minimal detergent solubilization of CLL membranes, we found that CD52 colocalizes with ganglioside GM-1, a marker of membrane rafts. Fluorescence microscopy revealed that upon crosslinking CD52 with alemtuzumab+anti-Fc IgG, large patches, and in many cases caps, enriched in CD52 and GM-1 formed upon the CLL cell plasma membrane. Depletion of membrane cholesterol or inhibition of actin polymerization significantly diminished the formation of alemtuzumab-induced caps and reduced alemtuzumab-mediated CLL cell death. We compared alemtuzumab-induced direct cytotoxicity, effector cell-mediated toxicity and complement-mediated cytotoxicity of CLL cells to normal T cells. The direct cytotoxicity and observed capping was significantly greater for CLL cells as compared to normal T cells. Cell-mediated and complement-mediated cytotoxicity did not significantly differ between the two cell types. In summary, our data support the hypothesis that alemtuzumab can initiate CLL cell death by crosslinking CD52-enriched lipid rafts. Furthermore, the differential direct cytotoxic effect suggests that CD52 directed antibodies could possibly be engineered to more specifically target CLL cells.

Actins↗
PubMed2005

High-dose busulfan, cyclophosphamide, and etoposide does not improve outcome of allogeneic stem cell transplantation compared to BuCy2 in patients with acute myeloid leukemia.

SUMMARY: To reduce relapse following allogeneic transplantation for AML, intensification of high-dose busulfan/cyclophosphamide using additional agents has been investigated but with few reported comparisons. We compared an intensified regimen of etoposide (60 mg/kg), busulphan (14 mg/kg), and cyclophosphamide (120 mg/kg) (BuCyVP) with BuCy2 in 237 AML patients. No significant difference in overall outcome was observed following BuCyVP (n=127) or BuCy2 (n=110). The 5-year survival was 27.3 and 30.1% following BuCyVP and BuCy2, respectively (P=0.48). Similarly, the 5-year cumulative incidence of relapse (CIR) was 28.3 and 34.8% with BuCyVP and BuCy2 (P=0.45), respectively. On multivariable analysis, patients transplanted in CR1 (P=0.002) and from related donors (P=0.013) had longer survival, while disease status at transplant was the only factor predicting CIR (P=0.002). In a separate analysis of CR1 patients (n=56), there was no significant difference in survival (P=0.37) or CIR (P=0.87) between the two regimens. However, for more advanced disease, there was a trend towards less relapse with BuCyVP (P=0.08), which was balanced by a higher cumulative incidence of transplant-related deaths (P=0.03) compared to BuCy2, resulting in similar survival. Overall, our results do not support the use of the more intensive BuCyVP regimen over BuCy2 in either early or more advanced disease AML patients.

Acute Disease↗
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↗
PubMed2005

The evolving role of alemtuzumab in management of patients with CLL.

New insights into prognostic markers and the pathophysiology of chronic lymphocytic leukemia (CLL) are beginning to change the concept of CLL treatment. Alemtuzumab has evolved as a potent and effective therapeutic option for patients with CLL. Specifically, alemtuzumab has demonstrated substantial efficacy in fludarabine-refractory patients and has shown impressive responses when administered subcutaneously in first-line therapy. A group of experts gathered to discuss new data related to the use of alemtuzumab in CLL and to assess its place in the rapidly changing approach to treating patients with this disease. The main goals of this program were to update the management guidelines that were previously developed for alemtuzumab-treated patients and to provide community oncologists with guidance on the most effective way to integrate alemtuzumab into a CLL treatment plan.

Alemtuzumab↗
PubMed2004

Modern diagnostics in chronic myeloproliferative diseases (CMPDs).

According to the new WHO classification a group of chronic myeloproliferative diseases (CMPDs) were defined: chronic myeloid leukemia (CML), chronic neutrophilic leukemia (CNL), chronic eosinophilic leukemia and hypereosinophilic syndrome (CEL/HES), polycythemia vera (PV), chronic idiopathic myelofibrosis (with extramedullary hematopoiesis, CIMF), essential thrombocythemia (ET), and so called CMPD/unclassifiable. As clinical features and laboratory findings differ widely between these diseases several diagnostic approaches are mandatory at diagnosis for classification and are needed also for follow up studies, especially for the measurement of minimal residual disease (MRD). We here outline the laboratory set up at diagnosis and during follow up in CMPDs with specific focus on the respective therapeutical consequences. Only by using a comprehensive diagnostic panel including cytomorphology, cytogenetics, and molecular genetic methods establishing the correct diagnosis, optimizing treatment as well as evaluating treatment response is possible in CMPDs today.

Blood Cell Count↗
PubMed2004

The histone deacetylase inhibitor MS-275 induces caspase-dependent apoptosis in B-cell chronic lymphocytic leukemia cells.

MS-275 is a histone deacetylase (HDAC) inhibitor that has been reported to mediate its cytotoxic effect through generation of reactive oxygen species (ROS) in proliferating hematopoietic cell lines. We examined efficacy of MS-275 in nonproliferating chronic lymphocytic leukemia (CLL) cells from patients. In these cells, MS-275 demonstrated an in vitro LC(50) that was one log lower than for normal mononuclear cells. Following MS-275 treatment, histones H3 and H4 showed increased acetylation and HDAC enzymatic activity was reduced. Caspase-8, -9, and -3 were activated, and caspase substrates PARP and BID were cleaved. Additionally, FLICE-inhibitory protein (FLIP) was downmodulated following MS-275 incubation. MS-275 treatment caused detectable ROS generation after 15 h of incubation, which was blocked by the caspase inhibitor Z-VAD-fmk. Overexpression of Bcl-2 protein protected against MS-275-induced apoptosis. These data demonstrate that MS-275 is a promising therapy for the treatment of CLL, but that in contrast to previous reports, ROS generation does not precede commitment to apoptosis. Similar to many other therapeutic targets, MS-275-mediated apoptosis is reduced by overexpression of Bcl-2, justifying strategies to combine HDAC inhibitors with Bcl-2 antagonists.

Apoptosis↗
PubMed2003

A phase II study of cladribine treatment for fludarabine refractory B cell chronic lymphocytic leukemia: results from CALGB Study 9211.

Cladribine has been reported to have little activity in fludarabine- refractory chronic lymphocytic leukemia (CLL). We sought to determine whether resistance to therapy with cladribine in fludarabine-refractory CLL patients represented primary drug resistance or the inability to tolerate the myelosuppression associated with this therapy. Patients with fludarabine refractory CLL patients without severe thrombocytopenia (platelets >/=50 x 10(9)/l) or granulocytopenia (neutrophils >1.5 x 10(9)/l) were enrolled. All patients received cladribine (0.14 mg/kg) as a 2-h intravenous infusion daily for 5 days, repeated every 4 weeks. Patients received up to six cycles of therapy. Twenty-eight patients enrolled; 13 had intermediate (Rai stage I or II) and 15 high (Rai stage III and IV) risk stages. No patient had a complete remission, but nine (32%; 95% confidence interval, 15-49%) attained a partial remission when assessed using the modified NCI criteria (1996). The median time to relapse for responders was 12 months, while median progression-free survival for the entire group was 9 months (95% confidence interval, 4-14 months). The median overall survival was 2.2 years (95% confidence interval, 0.8-3.1 years). Response was predicted by pre-treatment Rai status with seven of 13 (54%) intermediate risk vs two of 15 (13%) high-risk patients responding (P = 0.04). Toxicity was myelosuppression and infections (grade 3-5: neutropenia 75%, thrombocytopenia 68%, and infections 43%). Cladribine has modest clinical activity and considerable toxicity in a very selected group of patients with fludarabine-refractory CLL lacking pre-treatment neutropenia and thrombocytopenia.

Adult↗
PubMed2003

Depsipeptide (FR 901228) promotes histone acetylation, gene transcription, apoptosis and its activity is enhanced by DNA methyltransferase inhibitors in AML1/ETO-positive leukemic cells.

In t(8;21) acute myeloid leukemia (AML), the AML1/ETO fusion protein promotes leukemogenesis by recruiting histone deacetylase (HDAC) and silencing AML1target genes important for hematopoietic differentiation. We hypothesized that depsipeptide (FR901228), a novel HDAC inhibitor evaluated in ongoing clinical trials, restores gene transcription and cell differentiation in AML1/ETO-positive cells. A dose-dependent increase in H3 and H4 histone acetylation was noted in depsipeptide-treated AML1/ETO-positive Kasumi-1 cells and blasts from a patient with t(8;21) AML. Consistent with this biological effect, we also showed a dose-dependent increase in cytotoxicity, expression of IL-3, here used as read-out for silenced AML1-target genes, upregulation of CD11b with other morphologic changes suggestive of partial cell differentiation in Kasumi-1 cells. Some of these biologic effects were also attained in other myeloid leukemia cell lines, suggesting that depsipeptide has differentiation and cytotoxic activity in AML cells, regardless of the underlying genomic abnormality. Notably, the activity of depsipeptide was enhanced by 5-aza-2'-deoxycytidine, a DNA methyltransferase inhibitor (DNMT). These two agents in combination resulted in enhanced histone acetylation, IL-3 expression, and cytotoxicity, suggesting HDAC and DNMT activities as a potential dual target in future therapeutic strategies for AML1/ETO and other molecular subgroups of AML.

Acetylation↗
PubMed2003

Mitochondria control of cell death induced by anti-HLA-DR antibodies.

We have previously reported that crosslinking HLA-DR directly induces programmed cell death of malignant B cells. The present study further characterizes the biochemical mechanism for HLA-DR-mediated programmed cell death of tumor cells. Phosphatidylserine exposure on the plasma membrane and propidium iodide incorporation occur with very rapid kinetics and are observed as early as 10 min after the induction of cell death with anti-HLA-DR. In striking contrast to anti-CD95, we observe no activation of caspase-3, -8, or -9 upon anti-HLA-DR addition. Furthermore, the irreversible caspase inhibitor Z-VAD.fmk also failed to inhibit anti-HLA-DR-mediated cell death, further supporting the conclusion that HLA-DR induces cell death via a caspase-independent mechanism. We demonstrate that anti-HLA-DR-induced cell death is instead associated with a rapid disruption of the inner mitochondrial transmembrane potential, DeltaPsi(m), a process that is significantly inhibited by Bcl-2 overexpression. Furthermore, we find that DeltaPsi(m) disruption results in the selective release of apoptosis-inducing factor (AIF) from the mitochondria. We propose that AIF is acting to initiate the morphological and biochemical changes observed in HLA-DR-mediated cell death.

Antibodies, Monoclonal↗
PubMed2002

Human herpesvirus 8 genome is not found in whole bone marrow core biopsy specimens of patients with plasma cell dyscrasias.

Recently, molecular evidence of the gamma herpesvirus, human herpesvirus 8 (HHV-8), was found in the nonmalignant bone marrow stromal cells of patients with multiple myeloma using a polymerase chain reaction (PCR)-based assay. Other investigators have been unable to confirm either the presence of HHV-8 using molecular techniques or serologic evidence of prior infection with HHV-8. In order to maximize the likelihood of detection of small quantities of the virus and minimize the risk of potential nucleic acid contamination, we used entire bone marrow biopsy core specimens for DNA extraction and amplification. These specimens included both malignant plasma cells and bone marrow stromal cells and were subjected to minimal manipulation prior to DNA extraction and PCR. We tested eight patients with various plasma cell dyscrasias and compared them to negative controls with non-Hodgkin's lymphoma using standard PCR assays utilizing the KS330(233)primers and probe for HHV-8. This assay is reproducibly positive in Kaposi's sarcoma tissue. We found no evidence of HHV-8 DNA in either the lymphoma controls or the samples from patients with the plasma cell dyscrasias using these methods. We conclude that HHV-8 is unlikely to play a major role in the pathogenesis of the plasma cell dyscrasias in the majority of patients with these diseases. This report adds to the body of evidence that HHV-8 is not associated with plasma cell dyscrasias like multiple myeloma.

Adult↗
PubMed2001

Relation of gene expression phenotype to immunoglobulin mutation genotype in B cell chronic lymphocytic leukemia.

The most common human leukemia is B cell chronic lymphocytic leukemia (CLL), a malignancy of mature B cells with a characteristic clinical presentation but a variable clinical course. The rearranged immunoglobulin (Ig) genes of CLL cells may be either germ-line in sequence or somatically mutated. Lack of Ig mutations defined a distinctly worse prognostic group of CLL patients raising the possibility that CLL comprises two distinct diseases. Using genomic-scale gene expression profiling, we show that CLL is characterized by a common gene expression "signature," irrespective of Ig mutational status, suggesting that CLL cases share a common mechanism of transformation and/or cell of origin. Nonetheless, the expression of hundreds of other genes correlated with the Ig mutational status, including many genes that are modulated in expression during mitogenic B cell receptor signaling. These genes were used to build a CLL subtype predictor that may help in the clinical classification of patients with this disease.

Gene Expression↗
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

Concurrent pernicious anemia and myelodysplastic syndrome.

Megaloblastic anemia (MA) due to vitamin B12 deficiency is a reversible form of ineffective hematopoiesis. Myelodysplastic syndrome (MDS) is an acquired, irreversible disorder of ineffective hematopoiesis, characterized by stem cell dysfunction as a consequence of DNA damage manifested in part by karyotype anomalies. Importantly, MA and MDS are generally considered mutually exclusive diagnoses. We report the case of a 73-year-old woman with a profound macrocytic anemia, monocytosis and neurologic symptoms. Low cobalamin levels and the presence of anti-intrinsic-factor antibodies definitively established a diagnosis of pernicious anemia. Replacement therapy resulted in resolution of neurologic findings and macrocytosis; however, the anemia and monocytosis persisted. Bone marrow biopsy revealed trilineage myelodysplasia, which together with the peripheral monocytosis suggested a diagnosis of chronic myelomonocytic leukemia. Karyotype analysis revealed a clone with 45, XX, +der(1;7)(q10;p10)-7 [20]. Eighteen months after documented vitamin B12 replenishment her MDS transformed to terminal acute myeloid leukemia with the same clonal abnormality. Reversible cytogenetic abnormalities have been observed with MA, occasionally including karyotypes typically associated with MDS or myeloid leukemias. These abnormalities, like the anemia, resolve with vitamin replacement. This case suggests that MA and MDS can occur simultaneously; clinicians should be aware that this phenomenon occurs. Whether acquired karyotype abnormalities from the MA were related to the MDS and subsequent myeloid leukemia in this woman is a speculative but intriguing consideration that is discussed.

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

Antibody therapy of acute and chronic leukemias.

The development of antibody-based therapies for the treatment of both acute and chronic leukemias have undoubtedly been one of the most important advances in the treatment of leukemia. The importance of these novel agents lies not only in their unique mechanisms of action, but also their improved side effect profile which allows patients of advanced age or with significant co-morbid medical conditions to receive potentially beneficial therapies. Advances in therapeutic applications of monoclonal antibodies have come from a greater understanding of the biological characteristics of the antibody, as well as the target antigen, both of which impact the potential efficacy of a particular antibody. In the following review we will discuss the clinical development and potential roles of monoclonal antibodies in the treatment of both acute and chronic leukemias.

Acute Disease↗