High-dose chemotherapy in adult acute myeloid leukemia: rationale and results

Maximum supportive care, standard conditioning and allogeneic stem cell transplantation for elderly patients with acute myelogenous leukemia

Dose-intense conditioning (DIC) (myeloablative) regimens for allogeneic stem cell transplantation (alloSCT) were previously avoided in patients with acute myelogenous leukemia aged more than 55 years because of the fear of excessive morbidity and mortality. The introduction of reduced-intensity conditioning (RIC) alloSCT led to their increasing use in these patients because of their reduced toxicity. Significant disadvantages remain, however, including the late establishment of a posttransplant graft-versus-leukemia effect and an overrepresentation of poor prognostic factors in elderly patients, resulting in the risk of early relapse/progression before the graft-versus-leukemia effect being disproportionally large. Preliminary results suggest that DIC with maximum prophylaxis and support is safe for elderly patients up to age 70 years. We hypothesize that DIC may be important for the early control of leukemia in elderly patients, and that prospective, randomized trials comparing DIC and RIC-based transplants should be carried out, with the expectation that early transplant-related mortality will be no different.

The development of a novel protocol for the treatment of de novo childhood acute myeloid leukemia in a single institution in Taiwan

From November 1, 1995 to July 31, 2004, 49 children with de novo acute myeloid leukemia (AML) were treated at our institution. One patient who was treated by a different protocol was excluded. In total, 48 patients with de novo AML were enrolled in this study. Forty-two patients with AML other than acute promyelocytic leukemia (non-APL) were treated consecutively with 2 novel protocols: Mackay Memorial Hospital (MMH)-AML-96, designed as a pilot phase, and Taiwan Pediatric Oncology Group (TPOG)-AML-97A, on the basis of MMH-AML-96 with minor modifications. Six patients with APL were treated consecutively with 2 protocols, TPOG-APL-97 and APL-2001. As of July 31, 2006, the remission rates were 79%, 92%, and 98% after 1, 2, and 3 courses of induction therapy, respectively. The 5-year overall survival was 64%+/-6.9% (SE), and the 5-year event-free survival was 60%+/-7.1%; for non-APL AML, the rates were 62%+/-7.5% and 59%+/-7.6%; for APL, 83+/-15.2 and 67+/-19.3%. Among the factors analyzed, a complete remission achieved after 1 course of induction therapy, lactate dehydrogenase <500 IU/L at diagnosis, patients without invasive fungal infection during chemotherapy, and male sex were associated with a favorable outcome.

Trp53 loss during in vitro selection contributes to acquired Ara-C resistance in acute myeloid leukemia

OBJECTIVE

Chemoresistance remains a major clinical obstacle to curative chemotherapy of acute myeloid leukemia (AML), but the molecular mechanisms underlying resistance to chemotherapeutic agents used in AML are largely unknown. We have attempted to investigate genetic mechanisms causing resistance to Ara-C [1-beta-D-arabinofuranosyl-cytosine (cytarabine)], one mainstay in AML chemotherapy for decades.

MATERIAL AND METHODS

Highly Ara-C-resistant murine BXH-2 strain AML cell lines were generated, and their molecular changes were compared to their sensitive parental lines. The causative changes were confirmed using a genetic approach.

RESULTS

We derived nine highly Ara-C-resistant murine BXH-2 strain AML sublines via in vitro selection. p21Cip1 was dramatically downregulated and p53 protein accumulation induced by Ara-C treatment was impaired in one resistant line. In this line, repeated Ara-C exposure had selected for cells that harbor a genomic deletion affecting the splicing of Trp53 mRNA. This deletion produces an aberrant Trp53 mRNA, in which exon 4 is skipped, producing a protein lacking parts of both the transactivation and DNA-binding domains. Retroviral transduction of the sensitive parental cells with a dominant-negative Trp53 cDNA caused changes in the protein levels of p21Cip1, BAX, and cleaved caspase-3, but not bcl-XL, and rendered the cells more resistant to Ara-C. Unexpectedly, we found that pifithrin-alpha (PFTalpha), a compound that has been proposed to regulate p53 protein activity, induced apoptosis in both Ara-C-sensitive and -resistant lines, and decreased Ara-C resistance in cells with either normal or mutant Trp53 genes.

CONCLUSIONS

These data indicate that Trp53 loss-of-function could partly explain the acquisition of AML chemoresistance, and suggest that PFTalpha could be useful in treatment of relapsed AML.

Improved treatment results for childhood acute myeloid leukemia in Taiwan

To improve treatment results for children with de novo acute myeloid leukemia (AML), we introduced a novel protocol, Taiwan Pediatric Oncology Group-AML-97A, for AML other than acute promyelocytic leukemia (APL), for which modified conventional protocols were used. From January 1, 1997, to December 31, 2002, 141 children younger than 17 years old with de novo AML were enrolled. In total, 117 patients with non-APL AML were treated with induction therapy of idarubicin and cytarabine (Ara-C), postremission therapy with high-dose Ara-C - containing regimens for four monthly courses, and moderate-dose therapy with idarubicin and Ara-C for four monthly courses. The first 19 patients with APL were treated with all-trans retinoic acid, idarubicin and Ara-C, with the remaining five patients receiving all-trans retinoic acid and idarubicin, followed by maintenance therapy for 2 years. Stem cell transplantation was performed in 29 patients in first remission with a similar outcome as chemotherapy alone. The remission rate in the AML-97A study was 90%, the 5-year survival 51 +/- 5.3% (s.e.) and the 5-year event-free survival 50 +/- 4.8%; for APL, these were 100%, 86 +/- 7.0, and 75 +/- 9.8%. For the whole group, the 5-year survival was 57 +/- 4.7% and the 5-year event-free survival 54 +/- 4.4%. The AML-97A regimen was well tolerated.

Pharmacology of 5-Aza-2'-deoxycytidine (decitabine)

The preclinical pharmacology of 5-aza-2'-deoxycytidine (decitabine, 5AZA-CdR) is reviewed. 5AZA-CdR, an analogue of deoxycytidine, is a prodrug that requires metabolic activation by deoxycytidine kinase. The active inhibitor in the cell is its triphosphate form (5AZA-dCTP), which incorporates very readily into DNA to produce an inhibition of DNA methyltransferase. The mechanism responsible for the antileukemic action of 5AZA-CdR is related to its reversal of epigenetic silencing by aberrant DNA methylation of genes that suppress leukemiogenesis. 5AZA-CdR is an S-phase-specific agent. At concentrations in the range of micromolars this analogue can induce terminal differentiation and loss of clonogenicity of human leukemic cells. Drug resistance to 5AZA-CdR occurs primarily by reduction in deoxycytidine kinase activity or increase in the activity of cytidine deaminase, the enzyme that inactivates this analogue. 5AZA-CdR is a very potent antileukemic agent in animal models, more effective than the related antileukemic drug, cytosine arabinoside. In humans, 5AZA-CdR has a short half-life of 15 to 25 minutes due to rapid inactivation by liver cytidine deaminase. The major toxicity produced by 5AZA-CdR is myelosuppression. Preliminary clinical studies in patients with hematologic malignancies indicate that 5AZA-CdR is an active chemotherapeutic agent. The optimal dose-schedule for this interesting epigenetic agent with a novel mechanism of action remains to be determined. Translation of the pharmacology of 5AZA-CdR into therapeutic regimens based on scientific rationale can be used to obtain this objective.

High dose intermittent ARA-C (HiDAC) for consolidation of patients with de novo AML: a single center experience

High dose intermittent ARA-C (2x3 g/m(2) i.v., days 1, 3, 5)=HiDAC was introduced as consolidation in AML by the CALGB-group in 1994. We treated 44 de novo AML patients in CR with up to four cycles of HiDAC (four cycles: 56.8%; three cycles: 22.7%; two cycles: 6.8%; one cycle: 13.7%). Median duration of aplasia (ANC<0.5x10(9)/l) was 12 days. Neutropenic fever occurred in 38.6% of the patients during the first, 52.6% during the second, 45.7% during the third, and in 40% during the fourth cycle. Non-hematologic toxicity was tolerable. The median overall- and disease-free survival were 19.3 and 11.3 months, respectively. The best outcome was seen in patients aged <40 years. These results confirm that HiDAC is a safe and effective consolidation in AML.

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.

Acute Myeloblastic Leukemia: Management with High-Dose Cytosine Arabinoside, Daunorubicin and Marrow Transplantation; Malignancy; Current Clinical Practice

Combination high-dose cytosine arabinoside (ARA-C) and daunorubicin (DNR) for primary remission induction of patients with acute myeloblastic leukemia (AML) was evaluated in a single institution study. Patients aged 55 or less with an HLA-sibling received an allogeneic bone marrow transplant (alloBMT) in first remission; other responders were offered autologous BMT (autoBMT). For remission induction 93 patients aged less than 60 received DNR 45 mg/m(2) BSA x 3 and ARA-C 2 gm/m(2) BSA every 12 hours for 12 doses; 53 aged 60 or older DNR 25 mg/m(2) daily x 3 and ARA-C 1.5-2.0 gm/m(2) BSA every 12 hours for 12 doses. Consolidation doses of DNR were the same but ARA-C 100 mg/m(2) BSA/day x 5 was given by continuous intravenous infusion. The complete remission rate for patients less than 60 years was 69.9% (95% CI: 59.5-79.0%) and 47.2% (95% CI: 33.3-61.4%) for the older patients. The median duration of first remission for the younger patients was 13.0 months and of overall survival 17.9 months; for patients over 60 years 5.6 and 10.0 months respectively. Disease-free survival and overall survival of the 19 patients receiving alloBMT and the 13 patients undergoing autoBMT aged less than 55 years and in first or second complete remission were significantly increased compared with 22 patients in remission but not having BMT (p < 0.001 and p < 0.013). The results support the effectiveness of high-dose ARA-C for remission induction, a need for intensive consolidation therapy and a role for BMT in the management of AML.

Cardiac and pulmonary toxicity in patients undergoing high-dose chemotherapy for lymphoma and breast cancer: prognostic factors

We sought to define risk factors predisposing breast cancer and lymphoma patients to cardiac and pulmonary toxicity when undergoing high-dose chemotherapy (HDC) and autologous stem cell rescue (ASCR). Additionally, we evaluated in depth the predictive value of the ejection fraction measured prior to HDC in determining cardiac toxicity. In this retrospective analysis, 24 variables were examined in 138 patients undergoing HDC and ASCR from 1990 until 1995. Logistic regression models were used to model the probability of experiencing cardiac and pulmonary toxicity as a function of the 24 prognostic covariates. Cardiac toxicity occurred in 12% of patients and pulmonary toxicity in 24% of patients. Bivariate analyses showed that patients with lymphoma (as opposed to breast cancer) and those with a higher cardiac risk factor score were more likely to experience cardiac toxicity. Multivariate logistic regression models predicted lymphoma and older age to be risk factors for cardiac toxicity. History of an abnormal ejection fraction and higher doses of anthracyclines prior to HDC may also contribute to cardiac toxicity. Pulmonary toxicity occurred more commonly in lymphoma than breast cancer patients, likely due to the busulfan used in the HDC regimen. No other risk factors for pulmonary toxicity were identified. We conclude that older patients with lymphoma should be carefully evaluated prior to being accepted for HDC programs. Older patients with breast cancer may tolerate this procedure well. There is a trend towards cardiac toxicity in patients with a past history of low ejection fraction, although seemingly poor cardiac risk patients may fare well with HDC if carefully selected with the aid of a thorough cardiac evaluation.

Targeted superantigens for immunotherapy of haematopoietic tumours

With the exception of childhood common acute lymphoblastic leukaemia (cALL), treatment of other hematopoietic B cell lineage tumours such as non-Hodgkin's lymphoma (B-NHL), adult ALL and multiple myeloma (MM) is unsatisfactory. Similarly, the therapeutic outcome of acute and chronic myeloid leukaemia (AML, CML) is frequently dismal. At the same time, leukaemia/lymphoma cells represent ideal targets for immunotherapy. The present review summarizes our preclinical experience with a novel type of cytotoxic T cell based immunotherapy for B-lineage and myeloid tumours. Staphylococcal enterotoxin-derived superantigens (SAgs) are among the most potent T cell activators known, linking the T cell receptor to HLA-DR on natural target cells. SAgs were genetically engineered to reduce DR binding and were then fused to Fab parts of tumour-directed monoclonal antibodies (mAbs). Using these "targeted" SAgs, highly efficient lysis of B-lineage (B-NHL, B-CLL, ALL, MM) and myeloid (AML, CML) tumour cells by T-cells was achieved in vitro and in an animal model. We are entering an interesting era of innovative cancer therapy based on novel man-made biotherapeutic agents.

Antibody-directed superantigen-mediated T-cell killing of myeloid leukaemic cell line cells

Bacterial superantigens (SAgs) bound to MHC class II molecules on target cells are efficient activators of cytotoxic T cells expressing certain T cell receptor (TCR) Vbeta regions We described earlier that the specificity of the SAg Staphylococcus enterotoxin A (SEA) can be changed by introducing a D227A point mutation in the major MHC class II binding site and by genetically fusing the SEA mutant (SEAm) to protein A (PA). This SEAm-PA fusion protein can then be used to direct cytotoxic T cells to tumour cells coated with monoclonal antibodies (mAbs). In this communication, we tested the PA-SEAm fusion protein together with mAbs against the myeloid cell surface antigens CD13, CD15 and CD33. A SEA-reactive T cell line was used as effector cells against 10 different myeloid leukaemic cell lines. Optimal lysis of antigen positive leukaemic cells was obtained at a PA-SEAm concentration of 1 ng/ml and effector : target cell ratios of 15 : 1. No correlation between target cell sensitivity and the level of surface antigen expression could be seen. The 6 acute myeloid leukaemia (AML) cell lines tested appeared to be more sensitive than the 4 chronic myeloid leukaemia (CML) cell lines. The sensitivity of the AML cell line HL-60 could be improved further by stimulation with TNFalpha. This was accompanied by increased surface ICAM-1 expression whereas specific target molecule expression (CD13, CD33) was unchanged. This suggests that sensitivity to lysis is related to the leukaemic subtype and ICAM-1 expression but not to the tumour antigen density. Our results show that it is possible to direct cytotoxic T cells to myeloid leukaemia cells by using SAgs linked to mAbs, and encourage the construction and testing of a recombinant direct SAg-mAb fusion protein as a candidate drug for therapy of myeloid leukaemias.

Characterisation of genotoxic properties of 2',2'-difluorodeoxycytidine

The genotoxic properties of 2',2'-difluorodeoxycytidine (dFdC) were characterised using diploid, mortal low-passage fibroblasts (LPF cells) and the spontaneously transformed fibroblast cell line V79. In both cell types, incorporation of dFdC into the DNA led to an increase of DNA single-strand breaks evaluated by an in situ nick translation assay and to an accumulation of cells in the S-phase of the cell cycle. At concentrations below those leading to cell cycle arrest, dFdC neither induced sister chromatid exchange (SCE) nor structural chromosome aberrations in LPF cells, whereas V79 cells accumulated SCEs as well as chromosome breaks over a broad dose range. In LPF cells treated with dFdC, chromosomal alterations were detected by the micronucleus assay within a narrow concentration range, whereas in V79 cells, a dose-dependent increase in the appearance of micronuclei was seen up to cytotoxic concentrations. In addition, V79 cells went into apoptosis, as evaluated by nuclear fragmentation and condensation, whereas this phenomenon was not detectable in LPF cells.