Fludarabine-mediated repair inhibition of cisplatin-induced DNA lesions in human chronic myelogenous leukemia-blast crisis K562 cells: induction of synergistic cytotoxicity independent of reversal of apoptosis resistance

A Drug Repurposing Screen Identifies Fludarabine Phosphate as a Potential Therapeutic Agent for N-MYC Overexpressing Neuroendocrine Prostate Cancers

Neuroendocrine prostate cancer (NEPC) represents a highly aggressive form of prostate tumors. NEPC results from trans-differentiated castration-resistant prostate cancer (CRPC) with increasing evidence indicating that the incidence of NEPC often results from the adaptive response to androgen deprivation therapy. Recent studies have shown that a subset of NEPC exhibits overexpression of the MYCN oncogene along with the loss of tumor suppressing TP53 and RB1 activities. N-MYC is structurally disordered with no binding pockets available on its surface and so far, no clinically approved drug is available. We adopted a drug-repurposing strategy, screened ~1800 drug molecules, and identified fludarabine phosphate to preferentially inhibit the proliferation of N-MYC overexpressing NEPC cells by inducing reactive oxygen species (ROS). We also show that fludarabine phosphate affects N-MYC protein levels and N-MYC transcriptional targets in NEPC cells. Moreover, enhanced ROS production destabilizes N-MYC protein by inhibiting AKT signaling and is responsible for the reduced survival of NEPC cells and tumors. Our results indicate that increasing ROS production by the administration of fludarabine phosphate may represent an effective treatment option for patients with N-MYC overexpressing NEPC tumors.

Reduced-Intensity Conditioning with Fludarabine, Melphalan, and Total Body Irradiation for Allogeneic Hematopoietic Cell Transplantation: The Effect of Increasing Melphalan Dose on Underlying Disease and Toxicity

Disease relapse and toxicity are the shortcomings of reduced-intensity conditioning (RIC) for allogeneic hematopoietic cell transplantation (alloHCT). We hypothesized that adding total body irradiation (TBI) to and decreasing melphalan (Mel) from a base RIC regimen of fludarabine (Flu) and Mel would increase cytoreduction and improve disease control while decreasing toxicity. We performed a phase II trial of Flu 160 mg/m², Mel 50 mg/m², and TBI 400 cGy (FluMelTBI-50, n = 61), followed by a second phase II trial of Flu 160 mg/m², Mel 75 mg/m², and TBI 400cGy (FluMelTBI-75, n = 94) as RIC for alloHCT. Outcomes were compared with a contemporaneous cohort of 162 patients who received Flu 125 mg/m² and Mel 140 mg/m². Eligibility criteria were equivalent for all 3 regimens. All patients were ineligible for myeloablative/intensive conditioning. The median (range) follow-up for all patients was 51 (15 to 103) months. Day 100 donor lymphoid chimerism and transplant-related mortality, neutrophil and platelet engraftment, acute and chronic graft versus host disease incidence, overall survival (OS), and progression-free survival (PFS) were equivalent between FluMel, FluMelTBI-50, and FluMelTBI-75. Stomatitis wasdecreased for FluMelTBI versus FluMel (P < .01). PFS for patients not in complete remission on alloHCT was improved for FluMelTBI-75 versus FluMel (P = .03). On multivariate analysis, OS (P = .05) and PFS (P = .05) were significantly improved for FluMelTBI-75 versus FluMel. FluMelTBI-75 is better tolerated than FluMel, with improved survival and disease control.

Effects of Novel Dinuclear Cisplatinum(II) Complexes on the Electrical Properties of Human Molt-4 Leukemia Cells

The aim of this study was to determine the influence of cisplatin and novel dinuclear platinum(II) complexes on the membrane electrical properties and lipid peroxidation levels of the Molt-4 human leukemia cell line. Changes in cell function may affect the basal electrical surface properties of cell membranes. These changes can be detected using electrokinetic measurements. Surface charge densities of Molt-4 cells were measured as a function of pH. A four-component equilibrium model was used to describe the interaction between the ions in solution and on cell membrane surfaces. Agreement was found between the experimental and theoretical charge variation curves of the leukemia cells at pH 2.5–9. Lipid peroxidation was estimated by measuring levels of 8-iso-prostaglandine F2α [isoprostanes]. Acid and base functional group concentrations and average association constants with hydroxyl ions were smaller in cisplatin- or dinuclear platinum(II) complex-treated leukemia cell membranes compared to those in untreated cancer cells, and the average association constants with hydrogen ions were higher. Levels of lipid peroxidation products in cisplatin- or dinuclear platinum(II) complex-treated leukemia cell were higher than those found in untreated cancer cells.

The repair capacity of lung cancer cell lines A549 and H1299 depends on HMGB1 expression level and the p53 status

Elucidation of the cellular components responsive to chemotherapeutic agents as cisplatin rationalizes the strategy for anticancer chemotherapy. The removal of the cisplatin/DNA lesions gives the chance to the cancer cells to survive and compromises the chemotherapeutical treatment. Therefore, the cell repair efficiency is substantial for the clinical outcome. High mobility group box 1 (HMGB1) protein is considered to be involved in the removal of the lesions as it binds with high affinity to cisplatin/DNA adducts. We demonstrated that overexpression of HMGB1 protein inhibited cis-platinated DNA repair in vivo and the effect strongly depended on its C-terminus. We registered increased levels of DNA repair after HMGB1 silencing only in p53 defective H1299 lung cancer cells. Next, introduction of functional p53 resulted in DNA repair inhibition. H1299 cells overexpressing HMGB1 were significantly sensitized to treatment with cisplatin demonstrating the close relation between the role of HMGB1 in repair of cis-platinated DNA and the efficiency of the anticancer drug, the process being modulated by the C-terminus. In A549 cells with functional p53, the repair of cisplatin/DNA adducts is determined by а complex action of HMGB1 and p53 as an increase of DNA repair capacity was registered only after silencing of both proteins.

A phase I study of fludarabine, cytarabine, and oxaliplatin therapy in patients with relapsed or refractory acute myeloid leukemia

PURPOSE

The combination of cytarabine and fludarabine was associated with superior clinical outcomes compared with those of high-dose cytarabine in relapse acute myeloid leukemia (AML). We conducted a phase I study combining oxaliplatin with cytarabine and fludarabine therapy for patients with relapsed or refractory AML.

PATIENTS AND METHODS

Between January 2008 and November 2009, 27 patients were registered in the study. Patients had histologically confirmed disease, performance status 0 to 2, and adequate organ function. The treatment regimen consisted of increasing doses of oxaliplatin (25, 30, or 35 mg/m(2)/d) on days 1 to 4 (escalation phase), and fludarabine (30 mg/m²) and cytarabine (500 mg/m²) on days 2 to 6, every 28 days for ≤ 6 cycles. The dose-limiting toxicity was defined as any symptomatic grade ≥ 3 nonhematologic toxicity lasting ≥ 3 days and involving a major organ system.

RESULTS

Of 27 patients, 12 were treated in the dose-escalation phase and 15 at the maximum tolerated dose for oxaliplatin (30 mg/m²; expansion phase). All patients were evaluable for toxicity and response. Only 1 patient received the second cycle; the remaining patients received no further study treatment, owing to slow recovery from toxicities or physician decision. Grade 3-4 drug-related toxicities included diarrhea (grade 4) and elevated levels of bilirubin (grade 3) and aspartate transaminase (grade 3). In all, 3 patients had a complete remission and 2 patients complete response without platelet recovery.

CONCLUSION

Oxaliplatin, cytarabine, and fludarabine therapy had antileukemic activity in patients with poor-risk AML, but it was associated with toxicity. Different schedules and doses may be better tolerated.

Phase I-II clinical trial of oxaliplatin, fludarabine, cytarabine, and rituximab therapy in aggressive relapsed/refractory chronic lymphocytic leukemia or Richter syndrome

BACKGROUND

To improve outcomes of patients with Richter syndrome (RS) and relapsed/refractory chronic lymphocytic leukemia (CLL), we modified the OFAR1 regimen (oxaliplatin and cytarabine doses of the oxaliplatin, fludarabine, cytarabine, and rituximab) for this phase I-II study (OFAR2).

PATIENTS AND METHODS

OFAR2 consisted of oxaliplatin at 30 mg/m(2) on days 1 to 4, fludarabine at 30 mg/m(2), cytarabine at 0.5 g/m(2), rituximab at 375 mg/m(2) on day 3, and pegfilgrastim at 6 mg on day 6. Fludarabine and cytarabine were given on days 2 and 3 (cohort 1), days 2 to 4 (cohort 2), or days 2 to 5 (cohort 3) every 4 weeks. Phase II followed the "3 + 3" design of phase I.

RESULTS

The 102 patients (CLL, 67; RS, 35) treated had heavily pretreated high-risk disease. Twelve patients were treated in phase I; cohort 2 was the phase II recommended dose. The most common toxicities were hematologic. Response rates (phase II) were 38.7% for RS (complete response [CR], 6.5%) and 50.8% for relapsed/refractory CLL (CR, 4.6%). The median survival durations were 6.6 (RS) and 20.6 (CLL) months. Among 9 patients who underwent allogeneic stem cell transplantation (SCT) as post-remission therapy, none has died (median follow-up, 15.9 months).

CONCLUSION

OFAR2 had significant antileukemic activity in RS and relapsed/refractory CLL. Patients undergoing SCT as post-remission therapy had favorable outcomes.

DNA damage and repair in human cancer: molecular mechanisms and contribution to therapy-related leukemias

Most antitumour therapies damage tumour cell DNA either directly or indirectly. Without repair, damage can result in genetic instability and eventually cancer. The strong association between the lack of DNA damage repair, mutations and cancer is dramatically demonstrated by a number of cancer-prone human syndromes, such as xeroderma pigmentosum, ataxia-telangiectasia and Fanconi anemia. Notably, DNA damage responses, and particularly DNA repair, influence the outcome of therapy. Because DNA repair normally excises lethal DNA lesions, it is intuitive that efficient repair will contribute to intrinsic drug resistance. Unexpectedly, a paradoxical relationship between DNA mismatch repair and drug sensitivity has been revealed by model studies in cell lines. This suggests that connections between DNA repair mechanism efficiency and tumour therapy might be more complex. Here, we review the evidence for the contribution of carcinogenic properties of several drugs as well as of alterations in specific mechanisms involved in drug-induced DNA damage response and repair in the pathogenesis of therapy-related cancers.

Treatment of relapsed or refractory chronic lymphocytic leukemia

BACKGROUND

Recent advances in the treatment of chronic lymphocytic leukemia (CLL) have moved beyond the traditional use of alkylating agents and purine analogs into regimens combining these two chemotherapy classes with monoclonal antibodies.

METHODS

This article reviews treatments options for patients with relapsed or refractory CLL.

RESULTS

Several studies have investigated novel agents in treating patients with 17p deletion, TP53 mutation, and fludarabine-refractory CLL, as well as patients with suboptimal response to intense treatment. These investigational agents include rituximab, alemtuzumab, ofatumumab, bendamustine, high-dose methylprednisolone, lenalidomide, lumiliximab, cyclin-dependent kinase inhibitors, small modular immunopharmaceuticals, Bcl-2 inhibitors, and histone deacetylase inhibitors. While these newer drugs and combination therapies have shown promise as treatment options for CLL, additional studies are needed to determine the immunosuppression, toxicities, and infections associated with their use.

CONCLUSIONS

Despite improvement in initial overall response rates, most patients relapse and require further treatment. CLL remains incurable with standard therapies due to development of disease refractoriness. As such, novel approaches such as those noted above warrant continued research to improve outcomes for patients with CLL.

Synergistic effects of combination with fludarabine and carboplatin depend on fludarabine-mediated inhibition of enhanced nucleotide excision repair in leukemia

Overcoming drug resistance remains a major obstacle to curing relapsed or refractory lymphoma and obtaining a beneficial long-term prognosis for patients, despite the introduction of several salvage regimens to date. Our ultimate purpose is to establish a standard second-line salvage chemotherapy regimen for curing relapsed/refractory lymphoma. In this basic pre-clinical study, we evaluated a combination regimen consisting of 9-β-D: -arabinofuranosyl-2-fluoroadenine (F-araA) and carboplatin that targeted nucleotide excision repair (NER) of DNA in five representative leukemia lineages in vitro. Isobologram analysis demonstrated that simultaneous exposure to these two drugs produced synergistic interactions in U937 and K562 cells, in which lines showed enhanced NER activity by the measurement of UV or drug-induced DNA strand break (comet assay), or quantitation of ERCC1 mRNA (RT-PCR), a key enzyme for NER. Histone γH2AX formation was synergistically induced, but no such formation was observed after exposure to either agent alone in K562 cells. In summary, we synergistically inhibited the NER activity of leukemia cells by treating them with a combination of F-araA and carboplatin, suggesting that this combinatory regimen could be used as a novel salvage therapy for refractory or drug-resistant lymphoma.

Mechanism of action: the unique pattern of bendamustine-induced cytotoxicity

Bendamustine has demonstrated substantial efficacy in the treatment of hematologic malignancies and continues to distinguish itself from other alkylating agents with regard to its activity in tumor cells. The mechanistic and clinical differences associated with bendamustine may be directly related to its unique structural features. Although the precise mechanisms of action are still poorly understood, bendamustine is associated with extensive and durable DNA damage. The increased potency of bendamustine may be due to secondary mechanisms such as inhibition of mitotic checkpoints, inefficient DNA repair, and initiation of p53-dependent DNA-damage stress response, all of which lead to mitotic catastrophe and apoptosis. It has also been hypothesized that the presence of a benzimidazole ring in addition to the nitrogen mustard group may influence the way bendamustine interacts with DNA and/or confer antimetabolite properties. Further elucidation of the mechanisms of action for bendamustine and the signaling pathways involved in the response to bendamustine-induced DNA damage is essential to maximize its therapeutic potential, identify biomarkers for response, and understand the potential for synergy with other agents involved in DNA damage and inhibition of DNA repair. This review will discuss the current understanding and hypotheses regarding bendamustine mechanisms of action and suggest future investigations that would shed light on the many unanswered questions.

Determination of genes and microRNAs involved in the resistance to fludarabine in vivo in chronic lymphocytic leukemia

BACKGROUND

Chronic lymphocytic leukemia (CLL) cells are often affected by genomic aberrations targeting key regulatory genes. Although fludarabine is the standard first line therapy to treat CLL, only few data are available about the resistance of B cells to this purine nucleoside analog in vivo. Here we sought to increase our understanding of fludarabine action and describe the mechanisms leading to resistance in vivo. We performed an analysis of genomic aberrations, gene expression profiles, and microRNAs expression in CLL blood B lymphocytes isolated during the course of patients' treatment with fludarabine.

RESULTS

In sensitive patients, the differentially expressed genes we identified were mainly involved in p53 signaling, DNA damage response, cell cycle and cell death. In resistant patients, uncommon genomic abnormalities were observed and the resistance toward fludarabine could be characterized based on the expression profiles of genes implicated in lymphocyte proliferation, DNA repair, and cell growth and survival. Of particular interest in some patients was the amplification of MYC (8q) observed both at the gene and transcript levels, together with alterations of myc-transcriptional targets, including genes and miRNAs involved in the regulation of cell cycle and proliferation. Differential expression of the sulfatase SULF2 and of miR-29a, -181a, and -221 was also observed between resistant and sensitive patients before treatment. These observations were further confirmed on a validation cohort of CLL patients treated with fludarabine in vitro.

CONCLUSION

In the present study we identified genes and miRNAs that may predict clinical resistance of CLL to fludarabine, and describe an interesting oncogenic mechanism in CLL patients resistant to fludarabine by which the complete MYC-specific regulatory network was altered (DNA and RNA levels, and transcriptional targets). These results should prove useful for understanding and overcoming refractoriness to fludarabine and also for predicting the clinical outcome of CLL patients before or early during their treatment.

Treatment of fludarabine-refractory chronic lymphocytic leukemia

The development of resistance to purine analogs defines a poor-risk subset of patients with chronic lymphocytic leukemia (CLL). Although in recent years chemoimmunotherapeutic combinations such as fludarabine, cyclophosphamide, and rituximab have induced response rates of 95% in previously untreated patients and increased the rates of failure-free survival, CLL remains incurable for many patients because of a lack of disease response or the development of refractoriness to fludarabine. Fludarabine-refractory disease is defined as CLL that does not respond to fludarabine or that recurs within 6 months of treatment with a fludarabine-containing regimen. The natural course of the disease is associated with poor survival. Salvage therapeutic strategies include alemtuzumab-containing regimens, targeted agents, and allogeneic stem cell transplantation. Single-agent alemtuzumab induces response in up to 40% of patients with fludarabine-refractory CLL, but responses are not durable, and the median survival is approximately 1 to 2 years. Alemtuzumab is also combined with fludarabine, cyclophosphamide, and/or rituximab, and other agents such as lenalidomide and flavopiridol, as well as targeted agents, and used in fludarabine-refractory CLL. Cumulative evidence suggests that allogeneic stem cell transplantation is an efficacious therapeutic strategy for patients who do not respond to fludarabine or who develop disease recurrence within 12 months after purine analog treatment. In conclusion, chemoimmunotherapy regimens that include alemtuzumab and/or rituximab and allogeneic stem cell transplantation improve the prognosis of this disease, but there is a continued need for novel, more effective therapies.

Role of histone deacetylase inhibitor-induced reactive oxygen species and DNA damage in LAQ-824/fludarabine antileukemic interactions

The role of reactive oxygen species (ROS) production on DNA damage and potentiation of fludarabine lethality by the histone deacetylase inhibitor (HDACI) LAQ-824 was investigated in human leukemia cells. Preexposure (24 h) of U937, HL-60, Jurkat, or K562 cells to LAQ-824 (40 nmol/L) followed by fludarabine (0.4 micromol/L) dramatically potentiated apoptosis (>or=75%). LAQ-824 triggered an early ROS peak (30 min-3 h), which declined by 6 h, following LAQ-824-induced manganese superoxide dismutase 2 (Mn-SOD2) upregulation. LAQ-824/fludarabine lethality was significantly diminished by either ROS scavengers N-acetylcysteine or manganese (III) tetrakis (4-benzoic acid) porphyrin or ectopic Mn-SOD2 expression and conversely increased by Mn-SOD2 antisense knockdown. During this interval, LAQ-824 induced early (4-8 h) increases in gamma-H2AX, which persisted (48 h) secondary to LAQ-824-mediated inhibition of DNA repair (e.g., down-regulation of Ku86 and Rad50, increased Ku70 acetylation, diminished Ku70 and Ku86 DNA-binding activity, and down-regulated DNA repair genes BRCA1, CHEK1, and RAD51). Addition of fludarabine further potentiated DNA damage, which was incompatible with cell survival, and triggered multiple proapoptotic signals including activation of nuclear caspase-2 and release of histone H1.2 into the cytoplasm. The latter event induced activation of Bak and culminated in pronounced mitochondrial injury and apoptosis. These findings provide a mechanistic basis for understanding the role of early HDACI-induced ROS generation and modulation of DNA repair processes in potentiation of nucleoside analogue-mediated DNA damage and lethality in leukemia. Moreover, they show for the first time the link between HDACI-mediated ROS generation and the recently reported DNA damage observed in cells exposed to these agents.

Phase I-II Study of Oxaliplatin, Fludarabine, Cytarabine, and Rituximab Combination Therapy in Patients With Richter's Syndrome or Fludarabine-Refractory Chronic Lymphocytic Leukemia

Purpose

Richter's syndrome (RS) and fludarabine-refractory chronic lymphocytic leukemia (CLL) are associated with poor clinical outcomes. We conducted a phase I-II trial of oxaliplatin, fludarabine, cytarabine, and rituximab (OFAR) in these diseases.

Patients and Methods

The OFAR regimen consisted of increasing doses of oxaliplatin (17.5, 20, or 25 mg/m2/d) on days 1 to 4 (phase I), fludarabine 30 mg/m2 on days 2 to 3, cytarabine 1 g/m2 on days 2 to 3, rituximab 375 mg/m2 on day 3 of cycle 1 and day 1 of subsequent cycles, and pegfilgrastim 6 mg on day 6, every 4 weeks for a maximum of six courses. Dose-limiting toxicity (DLT) was defined as any nonhematologic, treatment-related toxicity ≥ grade 3.

Results

Fifty patients were treated (20 patients had RS, and 30 had CLL). The highest tolerated oxaliplatin dose was 25 mg/m2, which was the highest dose tested. DLT was not observed. Pharmacodynamic analyses demonstrated enhanced leukemia cell killing by oxaliplatin in the presence of fludarabine and cytarabine. The overall response rates were 50% in RS and 33% in fludarabine-refractory CLL. The overall response rate in 14 patients with age ≥ 70 years was 50%. Responses were achieved in seven (35%) of 20 patients with 17p deletion, two (29%) of seven patients with 11q deletion, all four patients with trisomy 12, and two (40%) of five patients with 13q deletion. The median response duration was 10 months. Toxicities were mainly hematologic; prolonged myelosuppression was not observed.

Conclusion

The OFAR regimen is highly active in RS and has activity in fludarabine-refractory patients with CLL. This regimen warrants further investigation in the treatment of these disorders.

Contributions of DNA interstrand cross-links to aging of cells and organisms

Impaired DNA damage repair, especially deficient transcription-coupled nucleotide excision repair, leads to segmental progeroid syndromes in human patients as well as in rodent models. Furthermore, DNA double-strand break signalling has been pinpointed as a key inducer of cellular senescence. Several recent findings suggest that another DNA repair pathway, interstrand cross-link (ICL) repair, might also contribute to cell and organism aging. Therefore, we summarize and discuss here that (i) systemic administration of anti-cancer chemotherapeutics, in many cases DNA cross-linking drugs, induces premature progeroid frailty in long-term survivors; (ii) that ICL-inducing 8-methoxy-psoralen/UVA phototherapy leads to signs of premature skin aging as prominent long-term side effect and (iii) that mutated factors involved in ICL repair like ERCC1/XPF, the Fanconi anaemia proteins, WRN and SNEV lead to reduced replicative life span in vitro and segmental progeroid syndromes in vivo. However, since ICL-inducing drugs cause damage different from ICL and since all currently known ICL repair factors work in more than one pathway, further work will be needed to dissect the actual contribution of ICL damage to aging.

Recent insights into platinum drug resistance in cancer

Cisplatin and its analogs have become important components of chemotherapeutic regimens for the treatment of solid tumors, however, their overall effectiveness is limited by the emergence of drug-resistant tumor cells. Resistance to the platinum drugs is multifactorial consisting of mechanisms that prevent the formation of lethal platinum-DNA adducts and mechanisms that operate downstream of the drug/target interaction to promote cell survival. Continued progress in the study of the drug resistance phenotype as well as the development of new platinum analogs may eventually lead to improved therapies and increased survival rates.

Fludarabine-mediated suppression of the excision repair enzyme ERCC1 contributes to the cytotoxic synergy with the DNA minor groove crosslinking agent SJG-136 (NSC 694501) in chronic lymphocytic leukaemia cells

In this study, we set out to establish whether fludarabine could enhance the DNA interstrand crosslinking capacity of SJG-136 in primary human chronic lymphocytic leukaemia (CLL) cells and thereby offer a rationale for its clinical use in combination with SJG-136. SJG-136 rapidly induced DNA crosslinking in primary CLL cells which was concentration-dependent. Further, the level of crosslinking correlated with sensitivity to SJG-136-induced apoptosis (P=0.001) and higher levels of crosslinking were induced by the combination of SJG-136 and fludarabine (P=0.002). All of the samples tested (n=40) demonstrated synergy between SJG-136 and fludarabine (mean combination index (CI)=0.54±0.2) and this was even retained in samples derived from patients with fludarabine resistance (mean CI=0.62±0.3). Transcription of the excision repair enzyme, ERCC1, was consistently increased (20/20) in response to SJG-136 (P<0.0001). In contrast, fludarabine suppressed ERCC1 transcription (P=0.04) and inhibited SJG-136-induced ERCC1 transcription when used in combination (P=0.001). Importantly, the ability of fludarabine to suppress ERCC1 transcription correlated with the degree of synergy observed between SJG-136 and fludarabine (r²=0.28; P=0.017) offering a mechanistic rationale for the synergistic interaction. The data presented here provides a clear indication that this combination of drugs may have clinical utility as salvage therapy in drug-resistant CLL.

Synthesis and mass spectroscopy kinetics of a novel ternary copper(II) complex with cytotoxic activity against cancer cells

The X-ray structure of the [Cu(I-hip)(phen)2](+).(I-hip-).(H2O)7 complex (1) (where I-hipH is referred to o-iodohippuric acid and phen is 1,10-phenanthroline) and its binary synthetic intermediate [Cu(I-hip)2(H2O)3].(H2O)2 (2) have been solved and characterized by different techniques. This ternary [Cu(I-hip)(phen)2]+.(I-hip-).7H2O complex generates the copper(I) complex [Cu(phen)2]+ in aqueous solution without the addition of any external reductant, possibly by an intramolecular red-ox process in the presence of oxygen; the ESI-HRMS spectra (electrospray ionization-high resolution mass spectroscopy) detect these species and 24h after the solution, [Cu(phen)2]+ is the main product. The complex 1 is capable of cleaving DNA. To evaluate the biological properties, we carried out: cell culture, cell proliferation assays, cell cycle analysis, and electrophoresis (SDS-PAGE) and immunoblotting. Complex 1 induced apoptosis of A549 cells at low nanomolar and induced marked decreases of cancer cells at concentrations that did not change adipocyte survival. These data indicate that the parent complex is a potential anticancer drug.

STAT1 signaling is associated with acquired crossresistance to doxorubicin and radiation in myeloma cell lines

The myeloma cell line RPMI 8226/S and its doxorubicin resistant subline 8226/Dox40 were used as models to explore the potential importance of the STAT1 signaling pathway in drug and radiation resistance. The 40-fold doxorubicin resistant subline 8226/Dox40 was found to be crossresistant to single doses of 4 and 8 Gy of radiation. A genome-wide mRNA expression study comparing the 8226/Dox40 cell line to its parental line was performed to identify the underlying molecular mechanisms. Seventeen of the top 50 overexpressed genes have previously been implicated in the STAT1 signaling pathway. STAT1 was over expressed both at the mRNA and protein level. Moreover, analyses of nuclear extracts showed higher abundance of phosphorylated STAT1 (Tyr 701) in the resistant subline. Preexposure of the crossresistant cells to the STAT1 inhibiting drug fludarabine reduced expression of overexpressed genes and enhanced the effects of both doxorubicin and radiation. These results show that resistance to doxorubicin and radiation is associated with increased STAT1 signaling and can be modulated by fludarabine. The data support further development of therapies combining fludarabine and radiation.

Fludarabine increases oxaliplatin cytotoxicity in normal and chronic lymphocytic leukemia lymphocytes by suppressing interstrand DNA crosslink removal

Oxaliplatin and fludarabine have different but potentially complementary mechanisms of action. Previous studies have shown that DNA repair is a major target for fludarabine. We postulate that potentiation of oxaliplatin toxicity by fludarabine may be due to the inhibition by fludarabine of the activity of the DNA excision repair pathways activated by oxaliplatin adducts. To test this, we investigated the cytotoxic interactions between the 2 drugs in normal and chronic lymphocytic leukemia (CLL) lymphocytes. In each population, the combination resulted in greater than additive killing. Analysis of oxaliplatin damage revealed that fludarabine enhanced accumulation of interstrand crosslinks (ICLs) in specific regions of the genome in both populations, but to a lesser extent in normal lymphocytes. The action of fludarabine on the removal of oxaliplatin ICLs was explored to investigate the mechanism by which oxaliplatin toxicity was increased by fludarabine. Lymphocytes from patients with CLL have a greater capacity for ICL unhooking compared with normal lymphocytes. In the presence of fludarabine the extent of repair was significantly reduced in both populations, more so in CLL. Our findings support a role of fludarabine-mediated DNA repair inhibition as a mechanism critical for the cytotoxic synergy of the 2 drugs.

A phase I and pharmacodynamic study of fludarabine, carboplatin, and topotecan in patients with relapsed, refractory, or high-risk acute leukemia

PURPOSE

A novel regimen designed to maximize antileukemia activity of carboplatin through inhibiting repair of platinum-DNA adducts was conducted in poor prognosis, acute leukemia patients.

EXPERIMENTAL DESIGN

Patients received fludarabine (10 to 15 mg/m(2) x 5 days), carboplatin (area under the curve 10 to 12 by continuous infusion over 5 days), followed by escalated doses of topotecan infused over 72 hours (fludarabine, carboplatin, topotecan regimen). Twenty-eight patients had acute myelogenous leukemia (7 untreated secondary acute myelogenous leukemia, 11 in first relapse, and 10 in second relapse or refractory), 1 patient had refractory/relapsed acute lymphoblastic leukemia, and 2 patients had untreated chronic myelogenous leukemia blast crisis. Six patients had failed an autologous stem cell transplant. Patients ranged from 19 to 76 (median 54) years. Measurement of platinum-DNA adducts were done in serial bone marrow specimens.

RESULTS

Fifteen of 31 patients achieved bone marrow aplasia. Clinical responses included 2 complete response, 4 complete response with persistent thrombocytopenia, and 2 partial response. Prolonged myelosuppression was observed with median time to blood neutrophils >/=200/microl of 28 (0 to 43) days and time to platelets >/=20,000/microl (untransfused) of 40 (24 to 120) days. Grade 3 or greater infections occurred in all of the patients, and there were 2 infection-related deaths. The nonhematologic toxicity profile was acceptable. Five patients subsequently received allografts without early transplant-related mortality. Maximum tolerated dose of fludarabine, carboplatin, topotecan regimen was fludarabine 15 mg/m(2) x 5, carboplatin area under the curve 12, and topotecan 2.55 mg/m(2) over 72 hours. An increase in bone marrow, platinum-DNA adduct formation between the end of carboplatin infusion and 48 hours after the infusion correlated with bone marrow response.

CONCLUSIONS

Fludarabine, carboplatin, topotecan regimen is a promising treatment based on potential pharmacodynamic interactions, which merits additional study in poor prognosis, acute leukemia patients.

Synergistic interaction between platinum-based antitumor agents and demethylcantharidin

A novel series of TCM-platinum complexes [Pt(C8H8O5)(NH2R)2] 1-5, designed from incorporating demethylcantharidin, a modified component from a traditional Chinese medicine (TCM) with a platinum moiety was found to circumvent cisplatin resistance in mouse leukemia and human hepatocellular carcinoma. These properties are most likely due to the inclusion of the protein phosphatase 2A (PP2A)-inhibiting demethylcantharidin in the novel compounds. We have investigated the potential synergistic effect of combining demethylcantharidin with a platinum-based antitumor agent, such as cisplatin, carboplatin, or oxaliplatin in vitro against L1210 mouse leukemia and SK-Hep-1 human hepatocellular carcinoma, and in vivo against a SK-Hep-1 subcutaneous-inoculated xenograft in nude mice, using median effect analysis. Demethylcantharidin and the platinum antitumor agents were synergistic in all cell lines tested in vitro, and the most effective antiproliferative regimen was when demethylcantharidin was added 24 h before cisplatin. Synergistic antitumor activity was also demonstrated in vivo without undue toxicity; no excessive loss in mouse body weight or overt pathology were observed at the effective doses. The results support a new approach for augmenting cytotoxic effect of established Pt-based drugs with demethylcantharidin in treating human hepatocellular carcinoma and other solid tumors.

Nonmyeloablative stem cell transplantation for lymphoma

High-dose chemotherapy and allogeneic stem cell transplantation is a potentially curative therapy for younger patients with non-Hodgkin's lymphoma (NHL). The benefits of this therapy, however, are largely offset by the high rate of treatment-related mortality, exceeding 40% in many studies. Risks increase with comorbidities, advanced age, histocompatibility, and disease-related prognostic factors. Given the potential efficacy of graft-versus-malignancy effects against many lymphoid malignancies, we evaluated an alternative strategy utilizing less toxic, nonmyeloablative conditioning regimens to allow engraftment of donor cells, and then exploit the graft-versus-lymphoma (GVL) effects of allogeneic transplantation as the primary therapy. This strategy involved fludarabine-based preparative regimens +/- high-dose rituximab, graft-versus-host disease (GVHD) prophylaxis for 6 months, and donor lymphocyte infusion (DLI) only for progressive or nonresponding disease. Results from these trials confirm the full potential on nonmyeloablative transplantation for patients with NHL.

Chronic myelogenous leukemia as a paradigm of early cancer and possible curative strategies

The chronological history of the important discoveries leading to our present understanding of the essential clinical, biological, biochemical, and molecular features of chronic myelogenous leukemia (CML) are first reviewed, focusing in particular on abnormalities that are responsible for the massive myeloid expansion. CML is an excellent target for the development of selective treatment because of its highly consistent genetic abnormality and qualitatively different fusion gene product, p210(bcr-abl). It is likely that the multiple signaling pathways dysregulated by p210(bcr-abl) are sufficient to explain all the initial manifestations of the chronic phase of the disease, although understanding of the circuitry is still very incomplete. Evidence is presented that the signaling pathways that are constitutively activated in CML stem cells and primitive progenitors cooperate with cytokines to increase the proportion of stem cells that are activated and thereby increase recruitment into the committed progenitor cell pool, and that this increased activation is probably the primary cause of the massive myeloid expansion in CML. The cooperative interactions between Bcr-Abl and cytokine-activated pathways interfere with the synergistic interactions between multiple cytokines that are normally required for the activation of stem cells, while at the same time causing numerous subtle biochemical and functional abnormalities in the later progenitors and precursor cells. The committed CML progenitors have discordant maturation and reduced proliferative capacity compared to normal committed progenitors, and like them, are destined to die after a limited number of divisions. Thus, the primary goal of any curative strategy must be to eliminate all Philadelphia positive (Ph+) primitive cells that are capable of symmetric division and thereby able to expand the Ph+ stem cell pool and recreate the disease. Several highly potent and moderately selective inhibitors of Bcr-Abl kinase have recently been discovered that are capable of killing the majority of actively proliferating early CML progenitors with minimal effects on normal progenitors. However, like their normal counterparts, most of the CML primitive stem cells are quiescent at any given time and are relatively invulnerable to the Bcr-Abl kinase inhibitors as well as other drugs. We propose that survival of dormant Ph+ stem cells may be the most important reason for the inability to cure the disease during initial treatment, while resistance to the inhibitors and other drugs becomes increasingly important later. An outline of a possible curative strategy is presented that attempts to take advantage of the subtle differences in the proliferative behavior of normal and Ph+ stem cells and the newly discovered selective inhibitors of Bcr-Abl. Leukemia (2003) 17, 1211-1262. doi:10.1038/sj.leu.2402912

DNA repair mechanisms involved in gemcitabine cytotoxicity and in the interaction between gemcitabine and cisplatin

The influence of DNA repair mechanisms on the interaction between gemcitabine and cisplatin was studied using a panel of Chinese hamster ovary (CHO) cell lines deficient in one of the following repair pathways: base excision repair (BER), nucleotide excision repair (NER), homologous recombination (HR) and non-homologous end joining (NHEJ). NER and HR are known to be involved in platinum-DNA adduct repair. Single agent experiments demonstrated that each of the repair deficient cell lines had a similar sensitivity towards gemcitabine as the parental cell lines, whereas the NER- and HR-deficient lines showed increased sensitivity towards cisplatin. Furthermore, in the parental cell lines, the administration sequence cisplatin followed by gemcitabine was synergistic, whereas the reversed schedule showed additivity and simultaneous administration revealed antagonistic cytotoxicity. In the repair deficient cell lines, using this synergistic schedule of cisplatin followed by gemcitabine, loss of synergy was observed in the NER- and HR-deficient cell lines. However, the magnitude of the effect in the NER-deficient cells was small. The sensitivity to the combination of cisplatin and gemcitabine shown by the BER- and NHEJ-deficient cell lines did not differ significantly from that of the parental cell line. Cellular accumulation of platinum as well as the formation of GG- and AG-intrastrand adducts in the parental line and in the HR-deficient line were not affected by gemcitabine. In conclusion, our results indicate that BER, NER, HR, and NHEJ are most likely incapable of modulating the cytotoxicity of gemcitabine, and that HR is involved in the synergistic interaction between cisplatin and gemcitabine in our cell system.

DNA-based drug interactions of cisplatin

The interactions of cisplatin with other anti-cancer agents on the DNA level have been studied extensively in pre-clinical experiments. In general, combination of cisplatin with an antimetabolite, taxane, or topoisomerase inhibitor, can result in a modulation of platinum pharmacology on the DNA, for example, enhanced retention of the platinum-DNA adducts. These interactions are mostly sequence and cell type dependent. In cell line models, antimetabolites can enhance the number of platinum-DNA adducts, probably by inhibition of DNA repair pathways. However, in clinical trials, the opposite effect has been observed, with a reduction of these adducts upon combined treatment. For the taxanes it has been shown that they can inhibit the formation of platinum-DNA adducts, whereas topoisomerase I inhibitors increase the number of adducts, resulting in strong synergistic cytotoxicity. For this last interaction a mechanistic model has recently been proposed, in which the topoisomerase I enzyme directly binds to the platinum-DNA adduct. Thereafter, the topoisomerase I inhibitor binds to this complex, which yields large stabilised lesions to the DNA that are probably difficult to repair. Ongoing studies will proceed to elucidate the exact mechanism underlying the interactions between cisplatin and other anti-neoplastic agents on the DNA level. Such increased understanding might help in designing new and more effective treatment regimens for cancer. In this paper, we review the pre-clinical and clinical studies investigating the observed interactions between cisplatin, the antimetabolites, taxanes, and topoisomerase inhibitors on the DNA level.

Non-myeloablative hematopoietic stem cell transplantation (NST) in the treatment of human malignancies: from animal models to clinical practice

NST is becoming a widely accepted method for allogeneic HSCT. Much experience has been gained, and the biology, indications and limitations are becoming clearer. Nonmyeloablative conditioning allows consistent engraftment of allografts from matched related, unrelated, and even partially matched donors. NST has been able to reduce the toxicity of allogeneic HSCT. The better immediate outcome produces better overall DFS. NST was feasible in elderly patients with almost no upper age limit, and in patients with organ dysfunction or other comorbidities precluding standard ablative conditioning. NST has also reduced the regimen-related toxicity of allogeneic HSCT in high-risk setting such as HSCT in heavily pretreated patients or following failure of a prior transplant procedure and in the unrelated setting. NST is rapidly becoming the treatment of choice in these indications where toxicity of standard ablative therapy is unacceptable. In certain malignancies such as in NHL, Hodgkin's disease and multiple myeloma, standard ablative NST has been reported to result in exceptionally high treatment related mortality, and NST is being investigated as a more reasonable alternative. NST may reduce the toxicity of the procedure even in younger patients who are eligible for ablative HSCT as well, however the long-term impact on patient outcome in this group is not yet established, and NST merits further investigation in prospective comparative trials. As described above, the known susceptibility of the underlying malignancy to GVT, the response to prior chemotherapy and bulk of residual disease, and the type of donor are other factors to consider when considering NST, and when selecting a regimen. The optimal preparative regimen needs to be defined. Ultimately less chemotherapy will be used and more specific immune-modulation, rather than intense nonspecific immunosuppression, will be used to achieve HVG tolerance. Preliminary animal models using costimulation blockade for specific induction of tolerance are promising steps towards achievement of this goal. Although much progress has been achieved with consistent achievement of engraftment with NST, GVHD and disease recurrence remain major obstacles to successful treatment. Existing clinical data suggest that NST does limit the incidence and severity of GVHD. Limitation of regimen-related toxicity, and bilateral transplantation tolerance afforded by mixed chimerism, are believed to have a major role in limiting GVHD. However GVHD remains the primary cause of treatment-related mortality. The development of techniques to separate GVHD and GVL are essential for further improvement of NST outcome. Better understanding of the biology and targets of GVHD and GVL may allow the elimination of alloreactive T-cells responsible for GVHD from the graft while retaining T-cells with GVL and infection control potential. Recurrence of the underlying malignancy is a major complication when NST is attempted in patients with chemo-refractory diseases and with high tumor bulk. Reduced toxicity regimens such as the FB/ATG regimen have been somewhat more successful in controlling disease progression until a potent GVT effect is established. However novel approaches are urgently required. NST serves as a platform for cellular immunotherapy. Judicious use of pre-emptive DLI needs to be explored. DLI may be amplified by activation of donor lymphocytes with IL-2 or in vivo administration of IL-2. Identification of tumor antigens will lead the way to ex-vivo generation and expansion of tumor specific cytotoxic T-lymphocytes to be used as potent immunotherapy without the hazards of GVHD. Allogeneic transplantation is rapidly changing from administration of supralethal doses of chemotherapy and radiation, trying to physically eliminate the 'last tumor cell', to the more subtle and tolerated sophisticated immunotherapy. This effort will focus on specific induction of HVG tolerance followed by induction of tumor-specific GVT effect to cure the underlying malignancy.

In vitro search for synergy and antagonism: evaluation of docetaxel combinations in breast cancer cell lines

The use of combination chemotherapy is the accepted standard for most human malignancies but little attention has been paid to drug interactions. A combination of drugs may be synergistic, additive, or antagonistic in cytotoxic activity. This study evaluated combinations of agents with docetaxel, one of the most active agents in human breast cancer, using a median effects model to look at synergy or antagonism in vitro as a potential predictor of clinical outcome. Three human breast cancer cell lines, MCF7/wt, MCF7/adr (multiply drug resistant), and BT474 were grown to confluence, plated into 96 well dishes, and incubated with combinations of drugs for 72h. Cytotoxic effect was measured by the MTT assay. Median effect analysis was used to calculate the combination index (CI) with values less than 1 indicating synergism, 1 additive effects, and greater than 1 antagonism. Potentially useful combinations for clinical study which were identified included docetaxel with vinorelbine, docetaxel with dexrazoxane, docetaxel with cis-retinoic acid, docetaxel with disulfiram and either doxorubicin or epirubicin, and docetaxel with dexrazoxane and epirubicin.

Cisplatin, fludarabine, and cytarabine: a novel, pharmacologically designed salvage therapy for patients with refractory, histologically aggressive or mantle cell non-Hodgkin's lymphoma

BACKGROUND

Based on in vitro synergism, the combination of cytarabine (ara-C) and cisplatin is the basis of many salvage regimens for patients with aggressive non-Hodgkin lymphoma (NHL). However, patients with previously refractory disease are significantly less likely to respond, stimulating the search for novel salvage regimens. In vitro, fludarabine enhances the cytotoxicity of both ara-C and cisplatin, increasing ara-C incorporation into DNA and inhibiting repair of platinum/DNA adducts, suggesting that the combination of cisplatin, fludarabine, and ara-C (PFA) may have clinical utility.

METHODS

A Phase-II study of a 96 hour continuous infusion of cisplatin with two timed-sequential couplets of fludarabine and ara-C together with granulocyte colony stimulating factor was performed in 45 patients with previously refractory, histologically aggressive or mantle cell NHL.

RESULTS

Patients had predominantly diffuse large cell and/or immunoblastic NHL or its variants (80%), or they had mantle cell lymphoma (18%). Overall, 93% of patients had previously refractory disease, with a median International Prognostic Index score of 3. A median of 2 cycles per patient were delivered (range, 1-4 cycles) with significant myelosuppression; there were medians of 2 days of neutropenia < 0.5 x 10(9)/L (range, 0-12 days) and 3 days of thrombocytopenia < 20 x 10(9)/L (range, 0-24 days). This was more severe in older patients and was cumulative with successive cycles. Thirty-five percent of cycles were complicated by infections, nausea and emesis were prominent, but other nonhematologic toxicity was mild. Peripheral blood progenitor cells were mobilized adequately after the first cycle, but collections were impaired after more prolonged therapy. The overall response rate was 48% (7% of patients had complete responses, and 41% of patients had partial responses), with one toxic death due to tumor-lysis syndrome. Patients with mantle cell lymphoma were more likely to respond than patients with other histologies (88% vs. 39%, respectively; P = 0.019), although three of eight patients had relapsed rather than refractory disease. The median remission duration was 4 months, with 28% of potentially eligible patients able to proceed to subsequent high dose therapy. The actuarial 2 year survival rates were 20% +/- 6% overall and 50 +/- 18% for patients with mantle cell lymphoma.

CONCLUSIONS

Given the adverse outlook for these patients, the results are promising, particularly for patients with mantle cell lymphoma, and suggest that the addition of fludarabine as a potential biochemical modulator may enhance the activity of cisplatin and ara-C. This is associated with significant cumulative (but manageable) myelosuppression. This paradigm, in which a nucleoside analogue is used to inhibit the repair of platinum/DNA adducts, also may be applicable for the treatment of patients with other types of platinum-sensitive tumors.

Limiting transplantation-related mortality following unrelated donor stem cell transplantation by using a nonmyeloablative conditioning regimen

A nonmyeloablative conditioning regimen was investigated in 47 patients with hematological malignancy receiving allogeneic progenitor cells from matched, unrelated donors. The median patient age was 44 years. The majority of patients had high-risk features, including having failed a prior transplantation (29 individuals). Twenty of the transplants were mismatched for HLA class I and/or class II alleles. Recipient conditioning consisted of 20 mg CAMPATH-1H on days -8 to -4, 30 mg/m(2) fludarabine on days -7 to -3, and 140 mg/m(2) melphalan on day -2. Graft-versus-host disease (GVHD) prophylaxis was with cyclosporine A alone. Primary graft failure occurred in only 2 of 44 evaluable patients (4.5%). Chimerism studies in 34 patients indicated that the majority (85.3%) attained initial full donor chimerism. Only 3 patients developed grade III to IV acute GVHD, and no patients have yet developed chronic extensive GVHD. The estimated probability of nonrelapse mortality at day 100 was 14.9% (95% confidence interval [CI], 4.7%-25.1%). With a median follow-up of 344 days (range, 79-830), overall and progression-free survivals at 1 year were 75.5% (95% CI, 62.8%-88.2%) and 61.5% (95% CI, 46.1%-76.8%), respectively. In summary, a nonmyeloablative regimen incorporating in vivo CAMPATH-1H is effective in promoting durable engraftment in most patients and in reducing the risk of severe GVHD following matched unrelated donor transplantation.

Inhibition of nucleotide excision repair and sensitisation of cells to DNA cross-linking anticancer drugs by F 11782, a novel fluorinated epipodophylloid

F 11782, or 2',3'-bis-pentafluorophenoxyacetyl-4',6'-ethylidene-beta-D-glucoside of 4'-phosphate-4'-dimethylepipodophyllotoxin 2-N-methyl glucamine salt, a novel dual catalytic inhibitor of topoisomerases I and II, was identified as a potent inhibitor of nucleotide excision repair (NER) by screening procedures using the in vitro 3D (DNA damage detection) assay. F 11782 was then shown predominantly to inhibit the incision rather than the repair synthesis step, using two new methodologies derived from this 3D assay, effectively ruling out any inhibition of polymerases delta/var epsilon. Moreover, data from two other in vitro assays showed an absence of any effect of F 11782 on: (i) the DNA damage binding of the XPA-RPA complex, and (ii) on SV40 large T-antigen helicase activity. Therefore, the inhibitory activity of F 11782 on NER may involve an inhibition of the ERCC1-XPF or XPG endonuclease activity. Moreover, inhibition of DNA repair by F 11782 was confirmed in human A549 cells by monitoring unscheduled DNA synthesis following mechlorethamine treatment. Such an inhibition provides an explanation for the highly synergistic cytotoxicity observed against cultured A549 lung tumour cells, when F 11782 was combined with cross-linking agents, such as cisplatin or mitomycin C. These results emphasise the unique mode of action of this novel molecule in inhibiting NER and provide a basis for its evaluation in clinical trials in combination with DNA cross-linking agents.

Melphalan and purine analog-containing preparative regimens: reduced-intensity conditioning for patients with hematologic malignancies undergoing allogeneic progenitor cell transplantation

A reduced-intensity preparative regimen consisting of melphalan and a purine analog was evaluated for allogeneic transplantation in 86 patients who had a variety of hematologic malignancies and were considered poor candidates for conventional myeloablative therapies because of age or comorbidity. Seventy-eight patients received fludarabine 25 mg/m(2) daily for 5 days in combination with melphalan 180 mg/m(2) (n = 66) or 140 mg/m(2) (n = 12). Eight patients received cladribine 12 mg/m(2) continuous infusion for 5 days with melphalan 180 mg/m(2). The median age was 52 years (range, 22-70 years). Disease status at transplantation was either first remission or first chronic phase in 7 patients, untreated first relapse or subsequent remission in 16 patients, and refractory leukemia or transformed chronic myelogenous leukemia in 63 patients. Nonrelapse mortality rates on day 100 were 37.4% for the fludarabine/melphalan combination and 87.5% for the cladribine/melphalan combination. The median percentage of donor cells at 1 month in 75 patients was 100% (range, 0%-100%). The probability of grade 2-4 and 3-4 acute graft-versus-host disease was 0.49 (95% CI, 0.38-0.60) and 0.29 (95% CI, 0.18-0.41), respectively. Disease-free survival at 1 year was 57% for patients in first remission or chronic phase and 49% for patients with untreated first relapse or in a second or later remission. On multivariate analysis the strongest predictor for disease-free survival was a good or intermediate risk category. In summary, fludarabine/melphalan combinations are feasible in older patients with associated comorbidities, and long-term disease control can be achieved with reduced-intensity conditioning in this population.

Melphalan and purine analog–containing preparative regimens: reduced-intensity conditioning for patients with hematologic malignancies undergoing allogeneic progenitor cell transplantation

A reduced-intensity preparative regimen consisting of melphalan and a purine analog was evaluated for allogeneic transplantation in 86 patients who had a variety of hematologic malignancies and were considered poor candidates for conventional myeloablative therapies because of age or comorbidity. Seventy-eight patients received fludarabine 25 mg/m2 daily for 5 days in combination with melphalan 180 mg/m2 (n = 66) or 140 mg/m2 (n = 12). Eight patients received cladribine 12 mg/m2 continuous infusion for 5 days with melphalan 180 mg/m2. The median age was 52 years (range, 22-70 years). Disease status at transplantation was either first remission or first chronic phase in 7 patients, untreated first relapse or subsequent remission in 16 patients, and refractory leukemia or transformed chronic myelogenous leukemia in 63 patients. Nonrelapse mortality rates on day 100 were 37.4% for the fludarabine/melphalan combination and 87.5% for the cladribine/melphalan combination. The median percentage of donor cells at 1 month in 75 patients was 100% (range, 0%-100%). The probability of grade 2-4 and 3-4 acute graft-versus-host disease was 0.49 (95% CI, 0.38-0.60) and 0.29 (95% CI, 0.18-0.41), respectively. Disease-free survival at 1 year was 57% for patients in first remission or chronic phase and 49% for patients with untreated first relapse or in a second or later remission. On multivariate analysis the strongest predictor for disease-free survival was a good or intermediate risk category. In summary, fludarabine/melphalan combinations are feasible in older patients with associated comorbidities, and long-term disease control can be achieved with reduced-intensity conditioning in this population.

Therapeutic potential of purine analogue combinations in the treatment of lymphoid malignancies

The main purine analogues with activity against lymphoid malignancies are fludarabine, cladribine and pentostatin, all of which are active against slowly proliferating cells through their inhibition of DNA repair and therefore have significant synergistic activity with cytotoxic agents which cause DNA damage. Combinations of purine analogues and alkylating agents or platinum compounds result in markedly increased activity but at the expense of more severe haematological toxicity, while evidence of synergy with anthracyclines/anthracenediones is apparent in the treatment of malignant lymphoma. Interaction between fludarabine or cladribine with deoxycytidine kinase results in a significant enhancement of the activity of cytarabine. Unexpected evidence of clinical synergy is also apparent in combinations of purine analogues and anti-CD20 monoclonal antibodies.

Allogeneic hematopoietic transplantation for acute and chronic myeloid leukemia: non-myeloablative preparative regimens and induction of the graft-versus-leukemia effect

High-dose chemoradiotherapy with allogeneic blood or bone marrow transplantation is an effective and potentially curative treatment for advanced or high-risk hematologic malignancies, but it has been associated with significant morbidity and mortality resulting from toxicity of the preparative regimen, graft-versus-host disease, and the immunodeficient state that accompanies the procedure. Development of safer and less toxic treatment has been the subject of much research. This review summarizes the current understanding of the mechanisms by which allogeneic transplants cure leukemia and the rationale for non-myeloablative preparative regimens. Experience of the authors is related with 116 patients diagnosed with acute or chronic myeloid leukemia who underwent allogeneic hematopoetic transplantation with two non-ablative regimens that differed in intensity.

In vitro cytotoxic effects of fludarabine (2-F-ara-A) in combination with commonly used antileukemic agents by isobologram analysis

Fludarabine phosphate (2-F-ara-AMP) is an adenine nucleoside analogue that shows significant activity against chronic lymphocytic leukemia and indolent lymphoma. We assessed the cytotoxic interaction produced by the combination of the active metabolite of fludarabine phosphate, fludarabine (9-beta-D-arabinofuranosyl-2-fluoroadenine, 2-F-ara-A), and some commonly used antileukemic agents against human hairy cell leukemia cell line JOK-1, human chronic lymphocytic leukemia cell line SKW-3, and adult T cell leukemia cell lines ED-40810 (-) and SALT-3. The leukemia cells were exposed simultaneously to 2-F-ara-A and to the other agents for 4 days. Cell growth inhibition was determined using MTT reduction assay. The isobologram method of Steel and Peckham was used to evaluate the cytotoxic interaction. 2-F-ara-A and cytarabine showed synergistic effects in SKW-3 cells, additive and synergistic effects in JOK-1 and SALT-3 cells, and additive effects in ED-40810(-) cells. 2-F-ara-A and doxorubicin showed additive effects in SKW-3, ED-40810(-) and SALT-3 cell lines, and additive and synergistic effects in JOK-1 cells. 2-F-ara-A showed additive effects with etoposide, 4-hydroperoxy-cyclophosphamide, and hydroxyurea in all four cell lines. 2-F-ara-A showed antagonistic effects with methotrexate and vincristine in all four cell lines. Our findings suggest that the simultaneous administration of fludarabine phosphate with cytarabine, doxorubicin, etoposide, cyclophosphamide, or hydroxyurea would be advantageous for cytotoxic effects. Among these agents, cytarabine may be the best agent for the combination with fludarabine phosphate. The simultaneous administration of fludarabine phosphate with methotrexate or vincristine would have little cytotoxic effect, and this combination may be inappropriate. These findings may be useful in clinical trials of combination chemotherapy with fludarabine phosphate and these agents.

DNA interactions of cisplatin tethered to the DNA minor groove binder distamycin

Modifications of natural DNA in a cell-free medium using cisplatin tethered to the AT-specific, minor groove binder distamycin, were studied using various methods of biochemical analysis or molecular biophysics. These methods include: binding studies using differential pulse polarography and flameless atomic absorption spectrophotometry, mapping DNA adducts using a transcription assay, use of ethidium bromide as a fluorescent probe for DNA adducts of platinum, measurement of DNA unwinding by gel electrophoresis, measurement of CD spectra, an interstrand cross-linking assay using gel electrophoresis under denaturing conditions, measurement of melting curves with the aid of absorption spectrophotometry and the use of terbium ions as a fluorescent probe for distorted base pairs in DNA. The results indicate that attachment of distamycin to cisplatin changes several features of the DNA-binding mode of the parent platinum drug. Major differences comprise different conformational alterations in DNA and a considerably higher efficiency of the conjugated drug to form in DNA interstrand cross-links. Cisplatin tethered to distamycin, however, coordinates to DNA with similar base sequence preferences as the untargeted platinum drug. The results point to a unique profile of DNA binding for cisplatin-distamycin conjugates, suggesting that tethering cisplatin to minor groove oligopeptide binders may also lead to an altered biological activity profile.