Phase I clinical and laboratory evaluation of topotecan and cytarabine in patients with acute leukemia

Review : Topoisomerase I inhibitors: 1. Topotecan

Purpose. The primary objective of this article is to discuss the pharmacology, pharmacokinetics, clin ical use, and adverse effects of the approved topoisomerase I inhibitors. This is the first in a series of two articles and will focus on topotecan.

Data Sources. We reviewed the literature through a MEDLINE search of English language articles from 1985 through 1997. Relevant articles cited in the titles obtained from the MEDLINE search were also used. The following terms were used for purpose of conducting the MEDLINE search: topoisomerase inhibitors, topotecan, topo isomerase I, Hycamtin, SKF 104864.

Data Extraction. We reviewed the current literature in order to discuss the pharmacology, pharmacokinetics, clinical use, toxicity, drug inter actions, indications, formulation, dosage and ad ministration, and pharmaceutical issues surround ing the use of topotecan.

Data Synthesis. The topoisomerase I inhibi tors are new antineoplastic agents with a unique mechanism of action. Promising areas of applica tion include ovarian cancer, lung cancer, radiation sensitization, and refractory leukemias. Clinical tri als detailing its activity in these areas are pre sented.

Failure of three novel regimens to improve outcome for patients with relapsed or refractory acute myeloid leukaemia: a report from the Eastern Cooperative Oncology Group

The treatment of relapsed acute myeloid leukaemia (AML) remains unsatisfactory. We conducted a phase II randomized trial where patients received intermediate-dose cytarabine for 4 d followed by gemtuzumab ozogamicin on day 5 (Arm A), or combined with liposomal daunorubicin for 3 d (Arm B), or cytarabine given for 5 d combined with cyclophosphamide for 3 d and topotecan by continuous infusion for 5 d (Arm C). Eligible patients had primary refractory AML, a first relapse after a remission of <1 year, or a second or greater relapse. The primary objective of this trial was attainment of a conventional complete remission (CR) or a CR without platelet recovery (CRp) in at least 40% of patients. The CR/CRp rates for the 82 eligible patients were 3/26 (12%) in Arm A, 2/29 (7%) in Arm B, and 1/27 (4%) in Arm C. No patients who had relapsed within 6 months of initial CR or who had suffered multiple relapses responded. More than 95% of patients subsequently died of AML. No unexpected toxicities were encountered. We conclude that none of these three regimens were effective enough in the treatment of high-risk relapsed or refractory AML to warrant further study. This trial was registered at http://www.clinicaltrials.gov as #NCT00005962.

Sequential topoisomerase targeting and analysis of mechanisms of resistance to topotecan in patients with acute myelogenous leukemia

Resistance to topoisomerase I (TOP1)-targeting drugs such as topotecan often involves upregulation of topoisomerase II (TOP2), with accompanying increased sensitivity to TOP2-targeting drugs such as etoposide. This trial was designed to investigate sequential topoisomerase targeting in the treatment of patients with high-risk acute myelogenous leukemia. An initial cohort of patients received topotecan and cytosine arabinoside daily for 5 days. Serial samples of circulating mononuclear cells were examined to evaluate peak elevations of TOP2-alpha protein expression. In subsequent cohorts, etoposide was administered daily for 3 days, beginning 6 h after initiation of the topotecan infusion. The etoposide dose was escalated to determine a maximum-tolerated dose. Circulating mononuclear cells were analyzed for TOP1 mutations and ABCG2 protein expression. In addition, systemic and intracellular topotecan concentrations were measured. Thirty-one patients were enrolled. On the basis of TOP1-alpha protein levels in three patients with peripheral blast counts greater than 50%, etoposide administration began 6 h after initiation of the topotecan/cytosine arabinoside infusion. Using this schedule of administration, the maximum-tolerated dose of etoposide was 90 mg/m. No TOP1 mutations were identified, but increases in ABCG2 expression during the infusion were observed in mononuclear cells from two of four evaluable patients. Administration of etoposide 6 h after initiation of a topotecan/cytosine arabinoside infusion is feasible and is associated with clinical activity. Analysis of TOP2-alpha protein levels in this small number of patients indicated that peak increases occurred earlier than expected based on earlier publications. Upregulation of ABCG2 was detected in circulating cells and may represent an inducible form of drug resistance that should be investigated further.

Sequential administration of irinotecan and cytarabine in the treatment of relapsed and refractory acute myeloid leukemia

PURPOSE

Based on reported synergy of the topoisomerase-I (topo-I) inhibitor irinotecan with antimetabolites, irinotecan and cytarabine (Ara-C) were administered sequentially to patients with acute myeloid leukemia (AML) refractory to or relapsed following high-dose Ara-C and anthracycline therapy. Pharmacokinetic and pharmacodynamic studies were performed with the first irinotecan dose.

EXPERIMENTAL DESIGN

In vitro synergy of irinotecan followed by Ara-C was confirmed in a human AML cell line as a basis for the clinical trial. Irinotecan was administered daily for 5 days, with Ara-C 1 g/m2 12 h after each irinotecan dose. Irinotecan was initiated at 5 mg/m2, and the dose was escalated by 5 mg/m2 increments in cohorts of three patients and in individual patients. Pre-treatment samples were studied for topo-I activity and serial samples after the first irinotecan dose were analyzed for pharmacokinetics and for pharmacodynamic effects, including DNA damage and DNA synthesis rate.

RESULTS

The irinotecan dose reached 15 mg/m2 in three-patient cohorts without reaching the maximum tolerated dose, and reached 30 mg/m2 in individual patients. The AUC and Cmax of both irinotecan and its active metabolite SN38 increased linearly in proportion to dose, and the mean half-lives of irinotecan conversion to SN38 and SN38 elimination were 6.2 h (CV 171%) and 7.2 h (CV 48%). Irinotecan rapidly induced DNA damage, and DNA synthesis inhibition varied among patients and treatment cycles. All courses resulted in rapid cytoreduction, and two patients achieved complete remission. Topo-I activity did not predict response.

CONCLUSION

Irinotecan can be safely administered with Ara-C. This combination is active in refractory AML and warrants further study.

A phase I trial of gemcitabine and topotecan in previously treated ovarian or peritoneal cancer: a Gynecologic Oncology Group study

OBJECTIVE

To determine the maximum tolerated dose (MTD) of the combination of gemcitabine and topotecan in women with previously treated epithelial ovarian, peritoneal, or fallopian tube cancer.

METHODS

Patients with recurrent or persistent cancer after treatment with a platinum and paclitaxel-containing regimen were eligible for this study. Initial treatment was gemcitabine at a dose of 800 mg/m(2) on days 1, 8, and 15 and topotecan at a dose of 0.5 mg/m(2) on days 2-5, with cycles repeated every 28 days. Dose escalations were planned first for topotecan (Cohort I, Dose Levels 1-5) then for gemcitabine (Cohort II, Dose Levels 6-9) until the MTD was reached.

RESULTS

Ten patients received a total of 29 cycles. When none of the first four patients could complete therapy as prescribed due to toxicity, doses for each drug were reduced by 1 day. The next six patients were treated at the modified schedule of gemcitabine days 1 and 8 and topotecan days 2-4 (Dose Level -1). Despite this modification, dose-limiting toxicities including neutropenia, thrombocytopenia, and stomatitis occurred at Dose Level -1, and the study was closed early.

CONCLUSIONS

At both the initial dose schedule and an attenuated schedule, the combination of gemcitabine and topotecan produced dose-limiting toxicities in women with previously treated epithelial ovarian or peritoneal cancer.

The therapy of relapsed acute leukaemia in adults

Although the cure of acute leukaemia has improved significantly, many patients will still relapse and die. The unraveling of the molecular pathogenesis of acute leukaemia has lead to the identification of new prognostic factors and improved the detection of minimal residual disease. The treatment of relapsed acute leukaemia with chemotherapy remains unsatisfactory. Allogeneic or autologous blood and marrow transplant (BMT) can cure a subset of patients with relapsed acute leukaemia. The identification of the graft-vs-leukaemia (GVL) effect has lead to the development of donor lymphocyte infusions to re-induce remission in patients with relapsed leukaemia after allogeneic BMT and also stimulated the development of the less toxic nonmyeloablative allogeneic transplant approach. The identification of molecular targets of therapy and the development of monoclonal antibody-directed therapy has generated optimism. It is possible that combinations of chemotherapy, molecularly directed therapy, and immunotherapy may be combined to cure an increasing proportion of patients with acute leukaemia.

Phase I/II clinical study of topotecan and cytarabine in patients with myelodysplastic syndrome, chronic myelomonocytic leukemia and acute myeloid leukemia

Topotecan, a topoisomerase-I inhibitor is an active drug in the treatment of AML and MDS. To evaluate its toxicity and efficacy in a combination regimen with cytarabine, we conducted a clinical phase I/II trial in patients with relapsed acute myeloid leukemia (AML) or relapsed or newly diagnosed MDS RAEB, RAEB-t or CMML. Twenty-one patients (11 AML, 10 MDS/CMML) entered the study and were treated with 1.25 mg/m2 topotecan as continuous intravenous infusion daily for 5 days and cytarabine 1.0 g/m2 by infusion over 2 h daily for 5 days (TA). Cycles were repeated on day 28. The median observation time was 131 weeks (range: 36-196 weeks). A total of 37 cycles of TA were administered. In 1 patient, the dose of TA had to be reduced and in 1 patient, there was a treatment delay for the second cycle, both because of hematologic toxicity. The most frequent non-hematologic side-effect of TA was fever, which occurred in 17 patients (89%) with temperatures over 38 degrees C. None of the patients died due to any treatment-related toxicities, but 2 patients (10%) died within 1 month due to disease progression. A CR was achieved in 7 patients (33%), 3 of whom were MDS and 4 AML. A partial remission was reported in 8 patients (38%), no change of disease in 2 patients (10%) and progressive disease in 4 patients (19%). The median remission duration was 18 weeks (range 2-161 weeks) for MDS patients and 11 weeks (range 2-49 weeks) for AML patients. The time to progression for patients of 60 years and older (n = 10) was 16 weeks (range 2-49 weeks) and the survival was 32 weeks (range 2-119 weeks). TA is a feasible and efficacious chemotherapeutic combination for the treatment of MDS RAEB, RAEB-t, CMML and AML. For patients of 60 years and older, this regimen is also a safe option.

A phase II study of timed sequential therapy of acute myelogenous leukemia (AML) for patients over the age of 60: two cycle timed sequential therapy with topotecan, ara-C and mitoxantrone in adults with poor-risk AML

Acute myeloid leukemia (AML) in the elderly is a serious problem characterized by poor response to therapy and short survival. To improve response to therapy, a timed sequential therapy (TST) approach was designed utilizing topotecan, cytosine arabinoside (ara-C) and mitoxantrone based on multiple studies suggesting that topotecan and mitoxantrone are effective in older patients. Thirty-two adults, >or=60-year-old (median age 69) were included. None had favorable cytogenetics and 44% had and antecedent myelodysplastic syndrome (MDS) or 2 degrees AML. Fifty-nine percent achieved a complete response (CR). Median overall survival (OS) was 6.5 months (95% confidence interval (CI): 3.1-12.0 months; range, 15 days to 25.3 months). Disease-free survival (DFS) for the 19 patients achieving a CR was 7.7 months (95% CI: 6.1-13.7 months; range, 2.9-25.3 months). There were no differences in OS or DFS between cytogenetic or disease etiology groups. Although TST was well tolerated, long-term results in this group of patients are not satisfactory and new approaches are needed.

Adult acute myeloid leukaemia

The curability of acute myeloid leukaemia (AML) in a fraction of adult patients was demonstrated a long time ago. Currently, the probability of cure is consistently above fifty per cent in patients with de novo disease expressing favourable-risk associated cytogenetic features. Even better, the cure rate exceeds 75% in the acute promyelocytic subtype since the introduction of retinoic acid-containing regimens. In the meantime, continuing progress in supportive care systems and stem cell transplant procedures is making myeloablative therapies, when needed, somewhat less toxic-and thereby more effective-than in the recent past. Therefore, evidence is accumulating to indicate an improved therapeutic trend over the years, with the notable exception of older (>55 years) patients with adverse-risk chromosomal aberrations and/or leukemia secondary to myelodysplasia or prior cancer-related chemotherapy and/or radiotherapy. This review conveys the many facets of this progress, focusing on diagnostic subsets, risk classes, newer biological issues and conventional as well as innovative therapeutic interventions with or without autologous/allogeneic stem cell transplantation.

Phase II study of low-dose topotecan in myelodysplastic syndromes: a Hoosier Oncology Group (HOG) study

Topotecan has demonstrable activity in high-risk MDS and CMMoL. However, the significant toxicity of topotecan administered at a dose of 2mg/m2 i.v. daily for 5 days as a continuous infusion limits its use in older patients. Therefore, we studied topotecan 1.5mg/m2 per day i.v. over 2 h for three consecutive days in 20 patients with high-risk MDS (12 RAEB; 4 RAEB-T; 4 CMMoL). Cycles were given every 4-6 weeks. Fifteen patients were evaluable for response. Only one patient achieved a durable complete remission (CR). There were three deaths within the first cycle of therapy. Severe myelosuppression was the most common toxicity. Grades 3-4 infections were documented in four patients. We conclude that topotecan administered at this dose and schedule has no clinically significant activity.

Alterations in the apoptotic machinery and their potential role in anticancer drug resistance

Anticancer drugs can potentially kill cells in two fundamentally different ways, by interfering with cellular processes that are essential for maintenance of viability or by triggering an endogenous physiological cell death mechanism. Apoptosis is a form of physiological cell death mediated by caspases, a unique family of intracellular cysteine proteases. Zymogen forms of these proteases are found in virtually all somatic cells, but remain latent until their activation is induced by ligation of specific cell surface receptors (the so-called "death receptors"), by mitochondrial alterations that allow release of cytochrome c and other intermembrane components, or possibly by other mechanisms. Most anticancer drugs activate the mitochondrial pathway. This apoptotic pathway is regulated by pro- and antiapoptotic members of the Bcl-2 family of proteins. Once activated, certain caspases might also be controlled by the inhibitor of apoptosis (IAP) proteins. Alterations in apoptotic pathway components or their regulators have been detected in a variety of cancers, suggesting that loss of the ability of cells to undergo apoptosis might contribute to carcinogenesis. Because cancer therapies such as radiation, glucocorticoids, and chemotherapeutic drugs exert their beneficial effects, at least in part, by inducing apoptosis of cancer cells, the same alterations in apoptotic pathways would be predicted to contribute to resistance. A key issue is whether the direct toxic activity of these treatments is of benefit when neoplastic cells contain changes that diminish their ability to undergo apoptosis.

A new multidrug reinduction protocol with topotecan, vinorelbine, thiotepa, dexamethasone, and gemcitabine for relapsed or refractory acute leukemia

We report the results of a phase 2 nonrandomized single-arm trial of a combination therapy for relapsed or refractory leukemia. From January 1999 to June 2002, 28 patients with multiple relapsed or refractory acute leukemia received a combination of topotecan, vinorelbine, thiotepa, dexamethasone, and, for patients with an M3 marrow on day 7, gemcitabine. A total of 14 patients had pre-B-ALL (acute lymphoblastic leukemia), three had T-cell leukemia, nine acute myeloblastic leukemia (AML), and two biphenotypic leukemia. In all, 13 patients achieved a significant response (10 complete responses and three partial responses). Among the responders, five had pre-B-ALL, two had T-cell leukemias, five had AML, and one had biphenotypic leukemia. In total, 10 of these patients subsequently underwent hematopoietic stem cell transplantation, and four are alive without disease. One patient died, while in remission, of complications resulting from an episode of sepsis and pneumonia that occurred during topotecan, vinorelbine, thiotepa, dexamethasone, and gemcitabine (TVTG) reinduction. Other toxicities included grade 4 neutropenia in all patients and transient grade 2 hepatotoxicity in 10 patients (36%). In summary, we report that 47% of heavily pretreated pediatric patients with multiply relapsed or refractory leukemia achieved a significant response after therapy on the TVTG protocol. Further studies are warranted to evaluate the role of the TVTG combination in the treatment of leukemia.

Acute myeloid leukemia

In this chapter, Drs. Keating and Willman review recent advances in our understanding of the pathophysiology of acute myeloid leukemia (AML) and allied conditions, including the advanced myelodysplastic syndromes (MDS), while Drs. Goldstone, Avivi, Giles, and Kantarjian focus on therapeutic data with an emphasis on current patient care and future research studies. In Section I, Dr. Armand Keating reviews the role of the hematopoietic microenvironment in the initiation and progression of leukemia. He also discusses recent data on the stromal, or nonhematopoietic, marrow mesenchymal cell population and its possible role in AML. In Section II, Drs. Anthony Goldstone and Irit Avivi review the current role of stem cell transplantation as therapy for AML and MDS. They focus on data generated on recent Medical Research Council studies and promising investigation approaches. In Section III, Dr. Cheryl Willman reviews the current role of molecular genetics and gene expression analysis as tools to assist in AML disease classification systems, modeling of gene expression profiles associated with response or resistance to various interventions, and identifying novel therapeutic targets. In Section IV, Drs. Hagop Kantarjian and Francis Giles review some promising agents and strategies under investigation in the therapy of AML and MDS with an emphasis on novel delivery systems for cytotoxic therapy and on targeted biologic agents.

Caspase-mediated cell death in hematological malignancies: theoretical considerations, methods of assessment, and clinical implications

Apoptosis, the caspase-mediated cell death, plays an important role in the etiology, pathogenesis and therapy of a variety of diseases. Abnormalities of apoptosis regulation, resulting in either its inhibition or enhancement, play a key role in the development of various malignant hematological disorders. Several routine and new therapeutic strategies in Oncohematology are based on apoptosis modulation. Cytotoxic effects of most antineoplastic drugs are based on induction of apoptosis. The accurate estimate of incidence of apoptosis, therefore, is of importance in Oncohematology. In this review we provide an overview of the methods designed to measure the incidence of apoptosis, including the recently developed assays that are based on detection of caspases activation. We also review recent findings on the role of caspase-mediated cell death in hematological malignancies and discuss their clinical implications, including new therapeutical strategies that evolve from these findings.

Apoptosis in glioma cells: review and analysis of techniques used for study with focus on the laser scanning cytometer

Traditional approaches to the treatment of brain tumors are based on the hypothesis that tumors arise and grow because of the disordered regulation of cell proliferation. More recently, it has become apparent that tumor growth depends not only on the rate of cell proliferation but also on the rate of apoptosis (programmed cell death). Genomic alterations that occur in malignancy may limit the cell's ability to undergo apoptosis. Many new treatment strategies for gliomas stem from the use of techniques aimed at manipulating apoptosis. Being able to assess the efficacy of experimental treatments with refined techniques and being able to use instruments that can provide accurate measurements of the apoptotic markers will open the door for discovering novel strategies with the potential to induce effective and selective cytotoxicity. We discuss here in detail the major traditional techniques of assessing apoptosis. We provide an overview of cytometric techniques, including flow cytometry (FC), and will compare it with the laser scanning cytometer (LSC). This is a powerful new tool with potential for obtaining a fast and objective analysis of apoptosis through multiple mechanisms, as well as for assessing proliferation and DNA ploidy in solid malignant tumors.

Timed sequential therapy of acute myelogenous leukemia in adults: a phase II study of retinoids in combination with the sequential administration of cytosine arabinoside, idarubicin and etoposide

Clinical outcome in acute myeloid leukemia (AML) is unsatisfactory. One strategy to augment cytotoxicity is TST. All-trans retinoic acid (ATRA) down-regulates bcl-2 expression and heightens AML sensitivity to cytosine arabinoside (ara-C)-induced apoptosis in vitro. We designed a trial of ATRA plus ara-C-based TST in an attempt to enhance drug-induced apoptosis and clinical outcome. Between January 1998 and February 2000, 63 patients received induction TST (oral ATRA days 1-6, ara-C and idarubicin days 2-4, VP-16 days 9-11) followed by consolidation TST (ATRA, ara-C and idarubicin followed by a second ara-C infusion days 11-13). Complete remission (CR) was 60%, with higher rates for patients of <60 years (79%), de novo AML (70%), and non-adverse cytogenetics (81%). Median disease-free survival (DFS) for CR patients was 11.2 months (32% at 3+ years). For patients <60 years with de novo AML and non-adverse cytogenetics who underwent two-cycle TST, DFS was 67% at 3+ years. However, patients of age equal to 60 years and those with poor-risk disease features still have poor CR and DFS, despite the addition of ATRA.

A phase I and pharmacodynamic study of sequential topotecan and etoposide in patients with relapsed or refractory acute myelogenous and lymphoblastic leukemia

We designed a pharmacokinetic and pharmacodynamic phase I study of sequential topotecan (2.55-6.3mg/m2) by 72h infusion followed by five daily doses of etoposide for patients with refractory acute leukemia based upon synergistic anti-tumor activity of topoisomerase I and II inhibitors in vitro. Eight of the 29 patients achieved bone marrow aplasia and two patients achieved clinical remission. Common grade 3-4 toxicities included hepatic and gastrointestinal dysfunction, and correlated with increased steady-state plasma topotecan concentration. The predicted up-regulation of topoisomerase II activity by topoisomerase I inhibition was not observed at this dose and schedule and may provide insight into the modest anti-leukemia activity of the regimen.

The treatment of acute myeloid leukemia in first relapse: a comprehensive review of the literature

Twenty years of published literature was reviewed for chemotherapy regimens used to treat patients with acute myeloid leukemia (AML) in first relapse. Thirty-one trials containing at least 20 patients in first relapse and information on patient age, duration of first complete remission (CR1), and rate of second complete remission (CR2) were analyzed. These trials included 10 retrospective studies with CR2 rates ranging from 30 to 64%, two phase II single-agent studies with CR2 rates of 8 and 25%, 15 phase II combination-agent studies with CR2 rates ranging from 14 to 87%, and four phase III randomized studies with CR2 rates ranging from 40 to 89%. When reported, median duration of CR2 was < or = 14 months and overall median survival was < or = 12 months. The probability of 3-year survival ranged from 8 to 29%. Combination therapies resulted in higher CR2 rates but were associated with longer duration of myelosuppression and greater incidence of mucositis. None of the reviewed regimens provided durable remissions for the majority of AML patients in first relapse. The CR2 rates were closely associated with age and duration of CR1. Therefore, considering the poor clinical outcomes of patients with AML in first relapse, improved therapies need to be developed.

Treatment of acute myeloid leukemia: state-of-the-art and future directions

Despite major recent advances in the understanding of the molecular biology of the disease, the treatment of acute myeloid leukemia (AML) in adults remains challenging. For the 75% of AML patients older than 60 years, currently available treatments produce significant toxicity with poor overall response rates and survival. In younger patients, standard regimens using cytarabine and an anthracycline for induction followed by some form of intensive postremission therapy can produce response rates of 70% with 5-year relapse-free survival rates of 25% to 40%. Chromosomal analyses define three prognostic categories with favorable, intermediate, and unfavorable risk. In older adults, AML appears to be an intrinsically resistant disorder of proximal pluripotent hematopoietic stem cells. A variety of targeted therapies currently in development include modulators of MDR1-mediated drug resistance, immunotherapeutics, angiogenesis inhibitors, proapoptotic antisense oligonucleotides, and specific small molecule inhibitors of tyrosine kinase and farnesyltransferase. For example, oral farnesyltransferase inhibitors have demonstrated activity and tolerability in patients with refractory AML and are now in phase II testing. Such targeted therapeutics offer the promise of novel antileukemic activity combined with an improved therapeutic index.

Using flow cytometry to follow the apoptotic cascade

Flow cytometry has been extensively used to follow the apoptotic cascade and to enumerate apoptotic cells, both in cell cultures and, to a lesser extent, in tissue biopsies. An overview of the apoptotic cascade and how flow cytometric measurements can be used to observe the different elements of this process is presented.

Treatment of refractory acute leukemia with timed sequential chemotherapy using topotecan followed by etoposide + mitoxantrone (T-EM) and correlation with topoisomerase II levels

A phase I/II clinical study evaluated 17 patients with refractory/recurrent acute leukemia treated with 1.5 mg/m2/day topotecan on days 1-3 followed by etoposide (100 mg/m2/day)+mitoxantrone (10 mg/m2/day) on days 4, 5 and 9, 10. Timed sequential chemotherapy using the topoisomerase I-inhibitor topotecan before the topoisomerase II-inhibitors, etoposide+mitoxantrone (T-EM) treatment is proposed to induce topoisomerase II protein levels and potentiate the cytotoxic activity of the topoisomerase II-directed drugs. Fourteen patients had refractory and three had recurrent acute leukemia. The majority of patients were heavily pre-treated with greater than three re-induction chemotherapy regimens. Ten patients responded to T-EM treatment (59%). Four of seventeen (24%) had a complete remission and one had a partial remission. Four additional patients (24%) who scored complete leukemia clearance had no evidence of disease with complete white and red blood cell recovery but with platelet counts less than 100,000. The lack of platelet recovery in one patient having a partial response was scored as a partial leukemia clearance. The toxicity profile included major non-hematological toxicity including grade 3 mucositis (29%) and neutropenic fever (65%). Paired measurements of intracellular levels of topoisomerase II isoforms alpha and beta in leukemia blast cells (bone marrow) collected before (day 0) and after topotecan treatment (day 4) showed that a relative increase of topoisomerase IIalpha (Topo IIalpha) > or = 40% strongly correlated with response after T-EM treatment. Increased Topo IIalpha levels also corresponded to increased DNA fragmentation. Two patients who had an increase of Topo IIalpha of 20-25% had either a PR or PLC while patients with a < 10% increase showed no response to T-EM treatment. We conclude that timed sequential chemotherapy using topotecan followed by etoposide+mitoxantrone is an effective regimen for patients with refractory acute leukemia, and demonstrate Topo IIalpha protein level increases after topotecan treatment.

Intravenous bolus topotecan in patients with myelodysplastic syndrome

We treated 16 patients with myelodysplastic syndromes with 24 courses of bolus topotecan. Patients received topotecan as a daily 15 minute infusion for 5 days at 3 dose levels (4.0 mg/m2/d, 2.0 mg/m2/d or 2.5 mg/m2/d). There was one complete response and one partial response (overall response rate 12%). Toxicity included myelosuppression, diarrhea, ileus and mucositis. There were 3 treatment-related deaths. The results of this schedule of topotecan appeared to be inferior to that reported with infusional topotecan in patients with MDS.

Cytosine arabinoside, idarubicin and divided dose etoposide for the treatment of acute myeloid leukemia in elderly patients

Elderly patients with acute myeloid leukemia (AML) have an unfavourable prognoses due to low remission rates, short remission durations, and a high treatment related toxicity. Therefore, new chemotherapy regimens with curative potential, decreased toxicity, and applicability to the majority of these patients are still needed. For remission induction, AML patients > or = 61 years of age received one to three induction courses of the DIVA regimen (idarubicin 10 mg/m2/d days 1 and 3, etoposide 2 x 60 mg/m2/d every 12 hrs. days 2 to 5, and cytarabine 100 mg/m2/d as continuous i.v. infusion days 1 to 5). After achieving CR, patients received two additional courses of DIVA as consolidation therapy. Forty-two consecutive patients with de novo and secondary AML with a median age of 68 years were entered into this trial while six patients were judged ineligible for medical reasons. 62% of the patients achieved a CR, lasting for a median of 26 weeks. Toxicity was mainly hematologic with an early death rate of 12%. The median overall survival for all patients was 38 weeks, and 51 weeks for the 26 patients who achieved CR. Outcome was not significantly different for patients with de novo compared to secondary AML. In conclusion, DIVA showed a promising antileukemic activity and acceptable toxicity as remission induction therapy for de novo and secondary AML in this negligible selected group of elderly patients. However, relapse rate was high, indicating the need for novel approaches for consolidation and maintenance therapy.

Malignancy: A New Approach to the Analysis of Apoptosis in the Leukemic Subpopulation by Flow Cytometry Using a CD45 Gating Strategy

Bone marrow and peripheral blood are heterogeneous tissues containing cells of different hematopoietic lineages. It is possible to detect leukemic cells by flow cytometry using a gating strategy, which combines CD45 expression on the cell surface with right angle light scatter (SS). This approach was applied to 15 cases of AML. Myeloblasts had the lowest CD45 fluorescence intensity of any of the cells in the myeloid series and also had the lowest SS, approximately equivalent to monocytes, but greater than lymphoblasts and lymphocytes. Using this gating strategy in each sample we could identify up to 5 separate cell compartments. Our results showed good correlation between the flow differential and the manual differential cell count. However in some cases, especially when a sample became hypocellular, the flow differential was more sensitive in identifying leukemic blasts. Total apoptosis (i.e. apoptosis in all cell populations combined) varied during the treatment between 0-34%. In the blood, the highest percentage of total apoptotic cells usually occurred between day 3-5 of treatment. The percentage of apoptotic cells varied depending on the cell type on a percentage basis. The leukemic population was lesslikely to undergo apoptosis compared to the lymphocytes, monocytes and more mature myeloid cells. In normal cells, apoptosis occurred mostly in G(1) and S phases of the cell cycle. Apoptosis among CD45-blasts usually varied between 0-5%. Myeloblasts also had a tendency to undergo apoptosis in G(1) and S phases of the cell cycle. The CD45-blast apoptotic peak in the blood occurred between day 5-7 of treatment. Analysis of drug-induced apoptosis in bone marrow seems to provide more information than such measurements in peripheral blood.

Topotecan (hycamptin) and topotecan-containing regimens in the treatment of hematologic malignancies

Single-agent topotecan is an active drug in chemotherapy-naive MDS and CMML and, to a lesser degree, in refractory/relapsed acute leukemias, low-/intermediate-grade lymphoma, and myeloma. Its combination with cytosine arabinoside induces complete remissions in high-risk MDS/CMML. A triple-combination regimen of cyclophosphamide, cytosine arabinoside, and topotecan (CAT) was extensively tested in refractory/relapsed as well as in untreated AML. By proving effective in inducing complete remission in newly diagnosed AML at rates comparable to those achieved by anthracycline-cytosine arabinoside regimens, for example, CAT offers a useful treatment alternative. Topotecan combined with paclitaxel is promising in low-/intermediate-grade lymphomas. The activity of topotecan justifies further evaluation of topotecan-containing combination regimens, particularly in MDS/CMML and acute leukemias.

Evaluation of topotecan and etoposide for non-Hodgkin lymphoma: correlation of topoisomerase-DNA complex formation with clinical response

BACKGROUND

Topotecan, a topoisomerase I inhibitor, acts by stabilizing the topoisomerase DNA cleavage complex. Etoposide, a topoisomerase II inhibitor, mediates antitumor activity by stabilizing cleavage complex formed between topoisomerase II and DNA. These two agents have therapeutic activity in non-Hodgkin lymphoma. The authors report Phase I data of topotecan and etoposide combination for patients with recurrent or refractory non-Hodgkin lymphoma and correlation of topoisomerase-DNA complex formation to clinical response.

METHODS

Twenty-two patients with recurrent or refractory aggressive non-Hodgkin lymphoma were treated at four dose levels of topotecan (1 mg/m(2)/day to 2.5 mg/m(2)/day). Topotecan was given at a 30-minute infusion daily with etoposide 150 mg/m(2)/day, both for 5 days. Topoisomerase-DNA covalent complex formation was measured using in vivo link assay, whereas topoisomerase I, IIalpha, and IIbeta in RNA expression levels were determined by reverse transcription-polymerase chain reaction in blood samples. The relation of these levels to clinical response was studied.

RESULTS

The maximum tolerated dose of topotecan was 2.0 mg/m(2)/day for 5 days. Oropharyngeal mucositis was dose-limiting. Of 21 examinable patients, 3 patients achieved complete remission, and 5 patients achieved partial remission. Of six untreated patients who experienced a recurrence, three had complete remission, and the other three had partial remission. Drug-induced topoisomerase-DNA complex formation was observed throughout the treatment in blood samples of all the patients who responded. However, only 4 of 13 patients, who did not respond, formed covalent complex at all time points. This was statistically significant (P = 0.024). In all patients, expression levels of topoisomerase I and IIbeta mRNA remained similar to pretreatment levels, whereas topoisomerase IIalpha mRNA levels decreased dramatically by the third day.

CONCLUSION

The recommended Phase II dose of topotecan with etoposide of 150 mg/m(2)/day for 5 days was 2.0 mg/m(2)/day for 5 days. Topoisomerase-DNA complex formation correlated with response to treatment.

First line therapy with fludarabine combinations in 42 patients with either post myelodysplastic syndrome or therapy related acute myeloid leukaemia

Acute myeloid leukaemias (AML) evolving from a myelodysplastic syndrome (MDS) or secondary to chemoradiotherapy frequently display unfavorable biologic characteristics. This may explain the lower remission rate obtained with conventional chemotherapy. Recently, the association of Fludarabine with intermediate dose Ara-C has produced interesting results particularly in high risk AML patients. Here, we report on 42 secondary AML patients treated with a combination of Fludarabine, intermediate dose Ara-C, G-CSF with or without an antracycline (FLANG, FLAG-IDA or FLAG). Overall, complete remissions (CR) were documented in 14 patients (33%) and partial responses (PR) in 12 (29%), while 10 patients proved resistant (24%). Six patients (14%) died early. The presence of a prognostically unfavorable karyotype had a negative impact on the CR rate (20% compared to 50% for patients with an intermediate prognosis karyotype, p 0.05). Patients treated with FLAG, FLANG and FLAG-IDA had similar CR rates. At the time of this analysis, after a mean follow-up of 12 months, the mean duration of CR is 16 months (range 3-66) and the mean survival is 11 months (range 1-67). The median time to granulocyte recovery (neutrophils > 0.5 x 10(9)/l) was 20 days (range 12-39) and 50 x 10(9)/l platelets were reached at a median of 26 days (range 9-56). Taken together, these Fludarabine containing regimens proved to be an effective and tolerable treatment for patients with secondary AML. Patients above 70 years of age may also benefit from this therapy, however the problem of treating patients with adverse chromosomal abnormalities still remains unresolved.

Evaluation of Apaf-1 and procaspases-2, -3, -7, -8, and -9 as potential prognostic markers in acute leukemia

Recent studies have suggested that variations in levels of caspases, a family of intracellular cysteine proteases, can profoundly affect the ability of cells to undergo apoptosis. In this study, immunoblotting was used to examine levels of apoptotic protease activating factor-1 (Apaf-1) and procaspases-2, -3, -7, -8, and -9 in bone marrow samples (at least 80% leukemia) harvested before chemotherapy from adults with newly diagnosed acute myelogenous leukemia (AML, 42 patients) and acute lymphocytic leukemia (ALL, 18 patients). Levels of each of these polypeptides varied over a more than 10-fold range between specimens. In AML samples, expression of procaspase-2 correlated with levels of Apaf-1 (Rs = 0.52, P &lt; .02), procaspase-3 (Rs = 0.56,P &lt; .006) and procaspase-8 (Rs = 0.64, P &lt; .002). In ALL samples, expression of procaspases-7 and -9 was highly correlated (Rs = 0.90,P &lt; .003). Levels of these polypeptides did not correlate with prognostic factors or response to induction chemotherapy. In further studies, 16 paired samples (13 AML, 3 ALL), the first harvested before induction therapy and the second harvested at the time of leukemia regrowth, were also examined. There were no systematic alterations in levels of Apaf-1 or procaspases at relapse compared with diagnosis. These results indicate that levels of initiator caspases vary widely among different leukemia specimens but cast doubt on the hypothesis that this variation is a major determinant of drug sensitivity for acute leukemia in the clinical setting.

Evaluation of Apaf-1 and procaspases-2, -3, -7, -8, and -9 as potential prognostic markers in acute leukemia

Recent studies have suggested that variations in levels of caspases, a family of intracellular cysteine proteases, can profoundly affect the ability of cells to undergo apoptosis. In this study, immunoblotting was used to examine levels of apoptotic protease activating factor-1 (Apaf-1) and procaspases-2, -3, -7, -8, and -9 in bone marrow samples (at least 80% leukemia) harvested before chemotherapy from adults with newly diagnosed acute myelogenous leukemia (AML, 42 patients) and acute lymphocytic leukemia (ALL, 18 patients). Levels of each of these polypeptides varied over a more than 10-fold range between specimens. In AML samples, expression of procaspase-2 correlated with levels of Apaf-1 (Rs = 0.52, P < .02), procaspase-3 (Rs = 0.56,P < .006) and procaspase-8 (Rs = 0.64, P < .002). In ALL samples, expression of procaspases-7 and -9 was highly correlated (Rs = 0.90,P < .003). Levels of these polypeptides did not correlate with prognostic factors or response to induction chemotherapy. In further studies, 16 paired samples (13 AML, 3 ALL), the first harvested before induction therapy and the second harvested at the time of leukemia regrowth, were also examined. There were no systematic alterations in levels of Apaf-1 or procaspases at relapse compared with diagnosis. These results indicate that levels of initiator caspases vary widely among different leukemia specimens but cast doubt on the hypothesis that this variation is a major determinant of drug sensitivity for acute leukemia in the clinical setting.

Clinical use of topoisomerase I inhibitors in anticancer treatment

The camptothecin analogs topotecan and irinotecan have shown to be among the most effective anticancer agents and, as S-phase specific agents, their antitumor effect is maximized when they are administered in protracted schedules. The documented activity as single agents in many adult and pediatric malignancies has been followed by their use in combination with other anticancer agents. These studies have shown promising results, and have placed topotecan and irinotecan in the first line treatment for some malignancies. However, studies to better determine the optimal schedules and sequence of combinations are needed.

Cyclophosphamide, ara-C and topotecan (CAT) for patients with refractory or relapsed acute leukemia

Topotecan is a topoisomerase I inhibitor with significant activity in patients with myelodysplastic syndrome and chronic myelomonocytic leukemia. Pre-clinical data suggest a synergistic activity with DNA damaging agents such as cyclophosphamide, where topotecan might prevent the repair of cyclophosphamide-induced DNA damage. We thus designed a combination including cyclophosphamide 500 mg/m2 every 12 hours given on days 1 to 3; topotecan 1.25 mg/m2/day by continuous infusion on days 2 to 6, and cytosine arabinoside (ara-C) 2 g/m2 over 4 hours daily for 5 days on days 2 to 6 (CAT). Sixty six (63 evaluable) patients were treated. Fifty two patients had refractory (n=12) or relapsed (n=40) acute myelogenous leukemia (AML), and eleven had acute lymphocytic leukemia (ALL) (refractory n=3, relapsed n=8); their median age was 57 years (range, 18 to 79 years). Eleven patients (17%) achieved a complete remission (CR), and two patients (3%) had a hematologic improvement (HI; met all criteria for CR except for platelets < 100x10(9)/L), for an overall response rate of 20%. Responses occurred in 12 of 52 AML patients (23%), including 10 CR (19%) and 2 HI (4%), and in 1 of 11 patients with ALL (9%). Myelosuppression was universal; there were 23 episodes of pneumonia or sepsis and 18 episodes of fever of unknown origin complicating 74 courses of CAT. Non-hematologic toxicity was mostly gastrointestinal, including nausea, vomiting, diarrhea and mucositis, but was severe in only 8%. In summary, the CAT regimen is well tolerated and has significant anti-leukemia activity which warrants further investigation.

Topotecan and cytarabine is an active combination regimen in myelodysplastic syndromes and chronic myelomonocytic leukemia

PURPOSE

To evaluate the efficacy and safety of the combination of topotecan and cytarabine in patients with myelodysplastic syndromes (MDSs) and chronic myelomonocytic leukemia (CMML).

PATIENTS AND METHODS

Fifty-nine patients with MDSs and 27 with CMML were enrolled. They were either previously untreated (66%) or had received only biologic agents (14%) or chemotherapy with or without biologic agents (20%). Treatment consisted of topotecan 1.25 mg/m(2) by continuous intravenous infusion daily for 5 days and cytarabine 1. 0 g/m(2) by infusion over 2 hours daily for 5 days. Prophylaxis included antibacterial, antifungal, and antiviral agents. At a median follow-up of 7 months, all 86 patients were assessable for response and toxicity.

RESULTS

Complete remission (CR) was observed in 48 patients (56%; 61% with MDSs, 44% with CMML; P =.15). Similar CR rates were observed for patients with good-risk and poor-risk MDS (70% and 56%, respectively). The treatment effectively induced CR in patients with a poor-prognosis karyotype involving chromosomes 5 and 7 (CR, 71%) and secondary MDSs (CR, 72%). Fifty-four patients received one induction course, 25 patients received two, and the rest received more than two. The median number of continuation courses was two. The median overall duration of CR was 34 weeks (50 weeks for MDSs and 33 weeks for CMML). The median survival was 60 weeks for MDS and 44 weeks for CMML patients. CR and survival durations were longer in patients with refractory anemia with excess blasts (RAEB). Grade 3 or 4 mucositis or diarrhea was observed in three patients each. Fever was observed in 63%, and infections in 49% of patients. Six patients (7%) died during induction therapy.

CONCLUSION

Topotecan and cytarabine induced high CR rates in unselected patients with MDSs and CMML, particularly among patients with poor-prognosis cytogenetics and secondary MDSs. Topotecan-cytarabine is an active induction regimen in MDS and CMML patients, is well tolerated, and is associated with a low mortality rate.

Cell cycle disturbances and apoptosis induced by topotecan and gemcitabine on human lung cancer cell lines

Apoptosis is a major mode of cell death in response to cytotoxic drug treatment. A correlation between induction of apoptosis and chemosensitivity has been documented in some preclinical models. Topotecan (a topoisomerase I inhibitor) and gemcitabine (a deoxycytidine analogue), two active new drugs for the treatment of lung cancer, were evaluated for their growth inhibitory effect on human lung cancer cell lines and their effect on cell cycle perturbation, apoptosis and apoptosis-related genes. The cytotoxicities of topotecan and gemcitabine on the human lung cancer cell lines H460 (wild-type-p53) and H322 (mutant p53 were determined after 72 h drug exposure employing the MTT assay. The apoptotic index (AI) was assessed by three methods: analysis of morphological changes using May-Grünwald-Giemsa (MGG) staining, the TUNEL assay and FACS analysis. Cell cycle disturbances were studied by FACS and the number of cells expressing p53 and p21 were determined by immunohistochemistry. Both gemcitabine and topotecan had potent growth inhibitory effects in human lung cancer cell lines; combination treatment with these two drugs showed some additivity but no synergism. Induction of apoptosis after treatment was concentration- and time-dependent with both drugs and IC80 concentrations induced the highest values. The DNA histograms at 4, 24, 48 and 72 h indicate that topotecan at IC80 concentrations causes accumulation of cells in S and G2/M phases, whereas gemcitabine at IC80 concentrations causes, accumulation of cells in G1 phase. Both compounds induced p53 and p21 expression in the H460 cell line but not in the H322 cell line; the percentage of cells expressing p53 was highest at IC80 values, whereas the highest percentage of p21 positive cells could be induced with IC50 values. This could suggest that p53 induces cell cycle arrest at low drug concentrations, whereas p53 induces apoptosis at higher concentrations. In conclusion, p53-dependent and independent pathways of apoptosis exist in lung cancer cell lines. Activation of the p53 pathway depends on the induced cellular damage. Understanding the cell cycle disturbances induced by these drugs may help in the design of more rational treatment schedules.

Topotecan: a new topoisomerase I inhibiting antineoplastic agent

OBJECTIVE

To review the pharmacologic, pharmacokinetic, therapeutic, and safety aspects of topotecan, a new antineoplastic agent, and to assess its role in the treatment of cancer.

DATA SOURCES

MEDLINE database English language only, January 1990-March 1998; SmithKline Beecham Pharmaceuticals; published articles, books, and abstracts.

STUDY SELECTION

Studies in humans with cancer, clinical case reports, open clinical trials, and controlled clinical studies. Efficacy studies were limited primarily to trials with at least 20 evaluable patients:

DATA EXTRACTION

Relevant data were extracted only from published reports. Data were obtained from studies in both articles and abstracts. Only articles written in English were reviewed.

DATA SYNTHESIS

Topotecan is an effective second- or third-line therapy for patients with advanced ovarian cancer and is comparable to ifosfamide, liposomal doxorubicin, and paclitaxel. Activity in combination with other agents and as a first-line agent is yet to be determined. Limited data indicate activity in small-cell lung cancer, cancers of the breast and uterus, and in nonlymphocytic leukemia. The dose-limiting toxicity is myelosuppression.

CONCLUSIONS

Topotecan is an effective second-line agent for patients with unresponsive or relapsed cancer of the ovary. It appears to be similar to other active agents in patients with this disease status. Its ultimate role in ovarian cancer and other neoplasms awaits additional evaluation in combination with other agents and as first-line therapy.

Results of topotecan single-agent therapy in patients with myelodysplastic syndromes and chronic myelomonocytic leukemia

The activity of topotecan was evaluated in patients with myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML). Sixty patients with a diagnosis of MDS (n = 30) or CMML (n = 30) were treated. Their median age was 66 years, with 50 patients (83%) being over 60 years of age at time of study entry. Chromosomal abnormalities were present in 50% of patients and thrombocytopenia of less than 50 x 10(9)/L in 50%. Topotecan was administered as 2 mg/m2 by continuous infusion over 24 hours daily for five days (10 mg/m2 per course) every 4 to 6 weeks for two courses, then at maximum tolerated dose level (1-2 mg/m2 by continuous infusion over 24 hours daily for five days) once every 4-8 weeks for a maximum of 12 courses. Evaluation of outcome and of differences among subgroups was performed according to standard methods; the criteria for response were those used for acute leukemia. Nineteen patients (31%) achieved a complete response (CR). A CR was achieved in 11 of 30 patients with MDS (37%) and in eight of 30 with CMML (27%). A CR was achieved in 10 of 23 patients with previously untreated MDS (43%). Eight of 11 patients who presented with cytogenetic abnormalities (five of which involved chromosome 5 and/or 7 abnormalities) and achieved CR, were evaluated cytogenetically in CR: all were cytogenetically normal in CR. Characteristics associated with a higher CR rate were lack of previous chemotherapy, absence of ras oncogene mutations, and presence of less than 10% monocytes in either peripheral blood or bone marrow. In contrast, CR rates were similar by different agent groups, by different karyotype abnormalities, and by other pre-therapy peripheral blood counts. Non-myelosuppressive side effects were mucositis in 67% of patients (severe [grade 3-4] 23%), diarrhea in 38% (severe 17%), and nausea and vomiting in 28% (severe 5%). Febrile episodes during neutropenia occurred in 85% of patients and documented infections in 47 %. Mortality in the first four weeks was 20%. With a median follow-up duration of 31 months, the 12 month survival rate was 38%, median survival time 10.5 months, and median remission duration 7.5 months. In summary, topotecan has significant single-agent activity in MDS and CMML. Complete responses associated with topotecan therapy often involve the disappearance of abnormal, poor-prognosis karyotypes, which is particularly encouraging. Future strategies to optimize topotecan's role include combination regimens with topoisomerase II reactive agents, cytarabine, or hypomethylating agents (azacytidine and decitabine).

Clinical applications of the camptothecins

The camptothecin topoisomerase I-targeting agents are new class of antitumor drugs with demonstrated clinical activity in human malignancies, such as colorectal cancer and ovarian cancer. Currently, irinotecan and topotecan are the most widely used camptothecin analogs in clinical use and clinical trials are ongoing to better characterize their spectra of clinical activity, to determine their optimal schedules of administration and to define their use in combination with other chemotherapeutic agents. Newer camptothecin analogs in clinical development, such as 9-aminocamptothecin, 9-nitrocamptothecin, GI147211 and DX-8951f, are also being studied to determine if they have improved toxicity and efficacy profiles compared with existing analogs. Other potential clinical applications include the use of camptothecin derivatives as radiation sensitizers or as antiviral agents. The successful development of the camptothecins as antitumor agents highlights the importance of topoisomerase I as a target for cancer chemotherapy.

Use of the Microculture Kinetic Assay of Apoptosis to Determine Chemosensitivities of Leukemias

Chemotherapeutic agents exert their antitumor effects by inducing apoptosis. The microculture kinetic (MiCK) assay provides an automated, continuous means of monitoring apoptosis in a cell population. We used the MiCK assay to determine the chemosensitivities of the human promyelocytic HL-60 and lymphoblastic CEM cell lines and leukemia cells freshly isolated from patients with acute nonlymphocytic (ANLL) or acute lymphocytic (ALL) leukemias. Continuous monitoring of apoptosis in the MiCK assay permits determination of the time to the maximum apoptosis (Tm) and its two components which are initiation time (Ti) and development time (Td). Duration of the three timing components of apoptosis varies from hours to days depending on the drug, drug concentration, and type of target cells. In the MiCK assay, the extent of apoptosis is reported in kinetic units of apoptosis. Kinetic units are determined by the slope of the curve created when optical density caused by cell blebbing is plotted as a function of time. Using the leukemia cell lines, we define the relationship between kinetic units determined by the MiCK assay and the percentage of morphologically apoptotic cells in the culture. Flow cytometry analysis of apoptosis in Annexin-V-fluorescein isothiocyanate–labeled preparations of HL-60 and CEM cells was also used to compare with data obtained by the MiCK assay. The feasibility of the MiCK assay of apoptosis as a chemosensitivity test was confirmed by its comparison with a 3H-thymidine incorporation assay. We show that samples from 10 ANLL and ALL patients patients tested for sensitivity to various doses of idarubicin (IDR), daunorubicin (DNR), or mitoxantrone (MTA) gave the same percentages of apoptotic cells when calculated by the MiCK assay as when determined by morphological analysis. The MiCK assay was used for dose-response analyses of the sensitivities to IDR, DNR, and MTA of leukemia cells from 4 other patients (2 ANLL and 2 ALL). The results from both cell lines and patient samples indicate that ANLL cells are more sensitive than ALL cells to all three of these chemotherapeutic agents. However, for individual patients the chemosensitivities varied significantly among the three chemotherapeutic agents. These varying responses to IDR, DNR, and MTA indicate that the MiCK assay results can be of potential use in designing a treatment regimen for a specific patient with acute leukemia. Among several drugs of presumed similar efficacy, the MiCK assay can permit the selection of the specific chemotherapeutic agent that causes the most apoptosis in the patient's leukemic cells.

© 1998 by The American Society of Hematology.

Use of the Microculture Kinetic Assay of Apoptosis to Determine Chemosensitivities of Leukemias

Chemotherapeutic agents exert their antitumor effects by inducing apoptosis. The microculture kinetic (MiCK) assay provides an automated, continuous means of monitoring apoptosis in a cell population. We used the MiCK assay to determine the chemosensitivities of the human promyelocytic HL-60 and lymphoblastic CEM cell lines and leukemia cells freshly isolated from patients with acute nonlymphocytic (ANLL) or acute lymphocytic (ALL) leukemias. Continuous monitoring of apoptosis in the MiCK assay permits determination of the time to the maximum apoptosis (Tm) and its two components which are initiation time (Ti) and development time (Td). Duration of the three timing components of apoptosis varies from hours to days depending on the drug, drug concentration, and type of target cells. In the MiCK assay, the extent of apoptosis is reported in kinetic units of apoptosis. Kinetic units are determined by the slope of the curve created when optical density caused by cell blebbing is plotted as a function of time. Using the leukemia cell lines, we define the relationship between kinetic units determined by the MiCK assay and the percentage of morphologically apoptotic cells in the culture. Flow cytometry analysis of apoptosis in Annexin-V-fluorescein isothiocyanate–labeled preparations of HL-60 and CEM cells was also used to compare with data obtained by the MiCK assay. The feasibility of the MiCK assay of apoptosis as a chemosensitivity test was confirmed by its comparison with a 3H-thymidine incorporation assay. We show that samples from 10 ANLL and ALL patients patients tested for sensitivity to various doses of idarubicin (IDR), daunorubicin (DNR), or mitoxantrone (MTA) gave the same percentages of apoptotic cells when calculated by the MiCK assay as when determined by morphological analysis. The MiCK assay was used for dose-response analyses of the sensitivities to IDR, DNR, and MTA of leukemia cells from 4 other patients (2 ANLL and 2 ALL). The results from both cell lines and patient samples indicate that ANLL cells are more sensitive than ALL cells to all three of these chemotherapeutic agents. However, for individual patients the chemosensitivities varied significantly among the three chemotherapeutic agents. These varying responses to IDR, DNR, and MTA indicate that the MiCK assay results can be of potential use in designing a treatment regimen for a specific patient with acute leukemia. Among several drugs of presumed similar efficacy, the MiCK assay can permit the selection of the specific chemotherapeutic agent that causes the most apoptosis in the patient's leukemic cells.

© 1998 by The American Society of Hematology.

Cell cycle perturbations in acute myeloid leukemia samples following in vitro exposures to therapeutic agents

Cell cycle checkpoints establish the timing and strength of arrest, repair and apoptosis responses to damaging treatments. We designed flow cytometric assays to measure cell cycle arrest and apoptosis in acute myeloid leukemia (AML) samples treated in vitro with relevant therapeutic agents so as to functionally characterize checkpoints in these samples and to ask if checkpoint abnormalities are common in AML and contribute to therapeutic failures. We show here that cell cycle responses to daunomycin (DNR), cytosine arabinoside (ARA-C) and gamma irradiation (RAD) were reproducibly treatment agent- and dose-dependent and distinct in different myeloid cell lines. DNR treatments differentially induced cell accumulations in the gap 2 and mitosis (G2/M) phases of the cell cycle and/or in the gap 1 (G1) phase, as did RAD, while ARA-C induced accumulations in the DNA synthesis (S) phase or in the G1 phase. Flow cytometric gates were devised to exclude lymphocytes and mature neutrophils in analyses of primary myeloid cell samples. Cell subsets in bone marrow samples from normal donors were thus enriched for myeloid constituents and used as normal myeloid cell controls. Proliferating cell nuclear antigen (PCNA) immunostaining was used to further identify actively dividing cell subpopulations in primary cell samples. AML samples were similarly analyzed and the majority showed lower DNA synthesis cell cycle phase (S) fractions and lower PCNA-positive fractions than normal myeloid cells, suggesting that AMLs are generally less proliferative in these culture conditions. Exceptional AML samples with high S phase fractions had cytogenetic abnormalities associated with poor prognosis. Most AML samples mounted weak cell cycle responses relative to normal myeloid cells, while a minority showed robust, agent-specific cell cycle arrests. This non-responsiveness was not simply associated with lower cycling indices-neither the response patterns nor the degrees of response were correlated with untreated S phase fractions or with PCNA-positive fractions. Cell cycle responses were also not associated with clinical parameters including patient age, FAB class, or white blood cell count, nor with immunophenotypic features including CD34 status, nor with specific cytogenetic markers. This suggests that functional cell cycle response assays could provide unique diagnostic information in AML. These assays might also have prognostic value as ARA-C induced G1 arrests and DNR-specific G2/M arrests tended to be associated with failure to achieve clinical remission. In addition, G1 arrests after ARA-C and G2/M accumulations after DNR treatments tended to be more robust in samples that had previously been shown to be more highly immunopositive for bcl-2 expression. This data suggests that the association of bcl-2 expression with particular cell cycle responses to therapeutic agents may contribute to the association of bcl-2 with poor clinical responses in AML. These data provide the basis for further laboratory studies aimed at examining specific cell cycle arrests as mechanisms of therapeutic resistance and prospective studies aimed at rigorously assessing the prognostic utility of in vitro assays of checkpoint function.

Elevated Expression of the Apoptotic Regulator Mcl-1 at the Time of Leukemic Relapse

Bcl-2, Bcl-xL, and Mcl-1 are three related intracellular polypeptides that have been implicated as negative regulators of apoptosis. In contrast, the partner protein Bax acts as a positive regulator of apoptosis. Based on the observation that all four of these polypeptides are expressed in a variety of acute myelogenous leukemia (AML) and acute lymphocytic leukemia (ALL) cell lines, cellular levels of these polypeptides were examined by immunoblotting in bone marrow samples harvested from 123 adult AML patients and 36 adult ALL patients before initial antileukemic therapy. Levels of Bcl-2, Mcl-1, Bcl-xL, and Bax each varied over a more than 10-fold range in different pretreatment leukemia specimens. When the 54 AML and 23 ALL samples that contained greater than 80% malignant cells were examined in greater detail, it was observed that pretreatment levels of Bcl-2 and Mcl-1 correlated with each other (R = .44,P < .001 for AML and R = .79,P < .0001 for ALL). In addition, a weak negative correlation between Bax expression and age was observed in AML samples (R = −0.35, P < .02) but not ALL samples. There was no relationship between pretreatment levels of these polypeptides and response to initial therapy. However, examination of 19 paired samples (the first harvested before chemotherapy and the second harvested 23 to 290 days later at the time of leukemic recurrence) revealed a greater than or equal to twofold increase in Mcl-1 levels in 10 of 19 pairs (7 of 15 AML and 3 of 4 ALL) at recurrence. In contrast, 2 of 19 pairs contained twofold less Mcl-1 at the time of recurrence. Approximately equal numbers of samples showed twofold increases and decreases in Bcl-2 (5 increases, 3 decreases) and Bcl-xL (1 increase, 4 decreases) at recurrence. Bax levels did not show a twofold decrease in any patient. These results, coupled with recent observations that cells overexpressing Mcl-1 are resistant to a variety of chemotherapeutic agents, raise the possibility that some chemotherapeutic regimens might select for leukemia cells with elevated levels of this particular apoptosis inhibitor.

Elevated Expression of the Apoptotic Regulator Mcl-1 at the Time of Leukemic Relapse

Bcl-2, Bcl-xL, and Mcl-1 are three related intracellular polypeptides that have been implicated as negative regulators of apoptosis. In contrast, the partner protein Bax acts as a positive regulator of apoptosis. Based on the observation that all four of these polypeptides are expressed in a variety of acute myelogenous leukemia (AML) and acute lymphocytic leukemia (ALL) cell lines, cellular levels of these polypeptides were examined by immunoblotting in bone marrow samples harvested from 123 adult AML patients and 36 adult ALL patients before initial antileukemic therapy. Levels of Bcl-2, Mcl-1, Bcl-xL, and Bax each varied over a more than 10-fold range in different pretreatment leukemia specimens. When the 54 AML and 23 ALL samples that contained greater than 80% malignant cells were examined in greater detail, it was observed that pretreatment levels of Bcl-2 and Mcl-1 correlated with each other (R = .44,P < .001 for AML and R = .79,P < .0001 for ALL). In addition, a weak negative correlation between Bax expression and age was observed in AML samples (R = −0.35, P < .02) but not ALL samples. There was no relationship between pretreatment levels of these polypeptides and response to initial therapy. However, examination of 19 paired samples (the first harvested before chemotherapy and the second harvested 23 to 290 days later at the time of leukemic recurrence) revealed a greater than or equal to twofold increase in Mcl-1 levels in 10 of 19 pairs (7 of 15 AML and 3 of 4 ALL) at recurrence. In contrast, 2 of 19 pairs contained twofold less Mcl-1 at the time of recurrence. Approximately equal numbers of samples showed twofold increases and decreases in Bcl-2 (5 increases, 3 decreases) and Bcl-xL (1 increase, 4 decreases) at recurrence. Bax levels did not show a twofold decrease in any patient. These results, coupled with recent observations that cells overexpressing Mcl-1 are resistant to a variety of chemotherapeutic agents, raise the possibility that some chemotherapeutic regimens might select for leukemia cells with elevated levels of this particular apoptosis inhibitor.