Mutated and non-mutated TP53 as targets in the treatment of leukaemia.

TP53 is mutated in 10-20% of cases of chronic lymphocytic leukaemia (CLL) and 3-8% of cases of acute myeloid leukaemia (AML). Recently, two classes of compounds that restore the function of p53 in tumours have been described. PRIMA-1 (p53-dependent reactivation and induction of massive apoptosis) restores the wild-type conformation of mutant TP53, whereas RITA (reactivation of p53 and induction of tumour cell apoptosis) increases intracellular levels of p53. We evaluated the effects of RITA alone and in combination with PRIMA-1 or conventional cytostatics on leukaemic cells isolated from AML and CLL patients. AML samples with -17, which are more resistant to daunorubicin and cytarabine compared with samples without -17, were effectively killed by PRIMA-1. RITA, which stabilizes the function of wild-type p53, induced apoptosis in AML cells. In contrast to that seen with PRIMA-1, AML patient samples without -17 were significantly more sensitive to RITA. Similarly, RITA exerted dose-dependent apoptosis and cytotoxicity in CLL cells, which was significantly more pronounced in samples without hemizygous TP53 deletion. Notably, a synergistic effect was observed in all CLL samples with RITA and fludarabine in combination. In both AML and CLL cells exposure to RITA resulted in induction of intracellular p53. We conclude that small molecules targeting p53 might be of clinical importance in the future for treating drug-resistant leukaemia.

P-Glycoprotein inhibitor valspodar (PSC 833) increases the intracellular concentrations of daunorubicin in vivo in patients with P-glycoprotein-positive acute myeloid leukemia.

PURPOSE: The aim of the present study was to evaluate the effect of the cyclosporine derivative valspodar (PSC 833; Amdray, Novartis Pharma, Basel, Switzerland) on the concentration of daunorubicin (dnr) in leukemic blast cells in vivo during treatment. PATIENTS AND METHODS: Ten patients with acute myeloid leukemia (AML) were included. Leukemic cells from seven of the patients were P-glycoprotein (Pgp)-positive. dnr 100 mg/m(2) was given as a continuous infusion over 72 hours. After 24 hours, a loading dose of valspodar was given, followed by a 36-hour infusion of 10 mg/kg per 24 hours. Blood samples were drawn at regular intervals, and concentrations of dnr and its main metabolite, daunorubicinol, in plasma and isolated leukemic cells were determined by high-pressure liquid chromatography. RESULTS: The mean dnr concentrations in leukemic cells 24 hours after the start of infusion (before valspodar) were 18.8 micromol/L in Pgp-negative samples and 13.5 micromol/L in Pgp-positive samples. After 8 hours of valspodar infusion, these values were 25.8 and 24.0 micromol/L, respectively. The effect of valspodar was evaluated from the ratio of the area under the curve (AUC) for dnr concentration versus time in leukemic cells to the AUC for dnr concentration against time in the plasma. For the seven patients with Pgp-positive leukemia, the mean ratio increased by 52%, from 545 on day 1 to 830 on day 2 (P<.05) when valspodar was given. In the three patients with Pgp-negative leukemia, no significant difference was observed. CONCLUSION: These results strongly suggest that valspodar, by interacting with Pgp, can increase the cellular uptake of dnr in leukemic blasts in vivo.

In vitro chemosensitivity testing in acute non lymphocytic leukemia using the bioluminescence ATP assay.

The ATP assay is a short term in vitro chemosensitivity assay where the amount of viable cells are determined by their content of ATP. The aim of the study was to compare the in vitro results of six cytostatic drugs to the clinical outcome in 83 acute non-lymphocytic leukemia (ANLL) patients. The secondary ANLL at diagnosis showed an in vitro resistance to daunorubicin that was significantly higher compared to de novo ANLL at diagnosis (P<0.003). De novo ANLL at diagnosis that achieved complete remission (CR) were significantly more sensitive to daunorubicin compared to those who didn't achieve CR (P<0.05). There was an vitro correlation between topoisomerase II active drugs but not between these drugs and ara-C. In vitro ara-C sensitivity (< or = the median of the de novo ANLL at diagnosis) was correlated to poor overall survival (P = 0.02). In vitro sensitivity to daunorubicin and mitoxantrone was associated with prolonged disease free survival (P = 0.03 and P = 0.04). We conclude that despite significant correlation to clinical parameters for daunorubicin and mitoxantrone the predictive value of the ATP assay in this material was insufficient for directing therapy.

Expression of topoisomerase IIalpha in the G0/G1 cell cycle phase of fresh leukemic cells.

Topoisomerase IIalpha (topo IIalpha) is the target enzyme for several antineoplastic drugs. Correlation between low expression of topo IIalpha and drug resistance has been shown in vitro, but there is limited evidence of a correlation to initial response to treatment or to overall prognosis. Normal cells express topo IIalpha in S/G2/M phase of the cell cycle but not in G0/G1 phase. However, some data suggest that topo IIalpha could be expressed in G0/G1 phase in malignant cells. We have investigated the expression of topo IIalpha in leukemic cells from 25 patients with acute leukemia by flow cytometry, separating cells of different cell cycle phases. We demonstrated that 9/25 samples showed >50% positive cells in G0/G1, and another five samples showed >20%. This finding could possibly provide an explanation to previous difficulties in correlating topo IIalpha expression with clinical outcome. Six of eight patients, where >20% of the cells in G0/G1 were positive for topo IIalpha, entered CR, compared to one of five patients with <20% topo IIalpha positive cells in G0/G1. We suggest that topo IIalpha expression in G0/G1 in leukemic cells may be of predictive value for clinical response to cytostatic drugs.

Interactions between P-glycoprotein and drugs used in the supportive care of acute myeloid leukemia patients.

Multidrug resistance due to overexpression of P-glycoprotein (Pgp) leads to reduced intracellular drug accumulation and makes the cells resistant to chemotherapy. In this study we focused on how drugs used in the supportive care of acute myeloid leukemia (AML) patients interfere with Pgp. The effect on intracellular accumulation of the fluorescent dye Rhodamine 123 (Rh 123) was studied in the human promyelocytic leukemia cell line HL-60 and two anthracycline resistant, Pgp expressing, sublines. Each drug was used at two different concentrations: plasma peak concentration and half the plasma peak concentration. Drugs which increased the Rh 123 uptake by > 10% were included in the second part of the study where the cytotoxic effect was tested in combination with daunorubicin. In the Rhodamine assay none of the tested drugs had any significant effect on the Rh 123 efflux in the resistant cell lines. Amphotericin B, cefuroxime, erythromycin and dixyrazin had minor effects on Rh 123 uptake but showed a significant additive effect to the toxicity of daunorubicin suggesting other mechanisms of action than reversal of Pgp. In conclusion this in vitro model where Rh 123 uptake was studied in an anthracycline resistant leukemia cell line could not demonstrate any significant interactions with Pgp for the tested drugs.

Incidence and prognostic significance of karyotypic subgroups in older patients with acute myeloid leukemia: the Swedish population-based experience.

The Swedish population-based acute myeloid leukemia registry contains data from 3251 patients (excluding acute promyelocytic leukemia) diagnosed between 1997 and 2006. Informative cytogenetic data from 1893 patients were retrospectively added, including 1054 patients aged between 60 and 79 years. Clonal abnormalities were found in 57% of the informative karyotypes. Karyotypic patterns differed by age: t(8;21), inv(16) and t(11q23) were more common in younger patients, whereas loss of 5q, 7q and 17p, monosomal karyotype (MK) and complex karyotypes were more common in older patients. Loss of 5q, 7q and 17p often occurred together within MK. Patients with 5 chromosome abnormalities had worse overall survival than those with fewer abnormalities or normal karyotype in all age groups. Loss of 5q, 7q and/or 17p had, in contrast to MK, a further negative impact on survival. Multivariable Cox regression analyses on risk factors in patients <80 years with cytogenetic abnormalities and intensive treatment revealed that age and performance status had the most significant impact on survival (both P<0.001), followed by sex (P=0.0135) and a karyotype including -7/del(7q) (P=0.048).

Limited clinical efficacy of azacitidine in transfusion-dependent, growth factor-resistant, low- and Int-1-risk MDS: Results from the nordic NMDSG08A phase II trial.

This prospective phase II study evaluated the efficacy of azacitidine (Aza)+erythropoietin (Epo) in transfusion-dependent patients with lower-risk myelodysplastic syndrome (MDS). Patients ineligible for or refractory to full-dose Epo+granulocyte colony stimulation factors for >8 weeks and a transfusion need of 4 units over 8 weeks were included. Aza 75 mg m(-2) d(-1), 5/28 days, was given for six cycles; non-responding patients received another three cycles combined with Epo 60 000 units per week. Primary end point was transfusion independence (TI). All patients underwent targeted mutational screen for 42 candidate genes. Thirty enrolled patients received one cycle of Aza. Ten patients discontinued the study early, 7 due to adverse events including 2 deaths. Thirty-eight serious adverse events were reported, the most common being infection. Five patients achieved TI after six cycles and one after Aza+Epo, giving a total response rate of 20%. Mutational screening revealed a high frequency of recurrent mutations. Although no single mutation predicted for response, SF3A1 (n=3) and DNMT3A (n=4) were only observed in non-responders. We conclude that Aza can induce TI in severely anemic MDS patients, but efficacy is limited, toxicity substantial and most responses of short duration. This treatment cannot be generally recommended in lower-risk MDS. Mutational screening revealed a high frequency of mutations.

Continuing high early death rate in acute promyelocytic leukemia: a population-based report from the Swedish Adult Acute Leukemia Registry.

Our knowledge about acute promyelocytic leukemia (APL) patients is mainly based on data from clinical trials, whereas population-based information is scarce. We studied APL patients diagnosed between 1997 and 2006 in the population-based Swedish Adult Acute Leukemia Registry. Of a total of 3897 acute leukemia cases, 3205 (82%) had non-APL acute myeloid leukemia (AML) and 105 (2.7%) had APL. The incidence of APL was 0.145 per 100,000 inhabitants per year. The median age at the time of diagnosis was 54 years; 62% were female and 38% male. Among younger APL patients, female sex predominated (89% of patients <40 years). Of the 105 APL patients, 30 (29%) died within 30 days (that is, early death (ED)) (median 4 days) and 28 (26%) within 14 days from diagnosis. In all, 41% of the EDs were due to hemorrhage; 35% of ED patients never received all-trans-retinoic acid treatment. ED rates increased with age but more clearly with poor performance status. ED was also associated with high white blood cells, lactate dehydrogenase, creatinine, C-reactive protein and low platelet count. Of non-ED patients, 97% achieved complete remission of which 16% subsequently relapsed. In total, 62% are still alive at 6.4 years median follow-up. We conclude that ED rates remain very high in an unselected APL population.

PRIMA-1 induces apoptosis in acute myeloid leukaemia cells with p53 gene deletion.

The p53 tumour suppressor gene located on chromosome 17p13 is the most frequently mutated gene in human tumours. About 5-8% of cases with acute myeloid leukaemia (AML) carry the p53 mutation. Recently, the compound p53-dependent reactivation and induction of massive apoptosis (PRIMA-1) has been shown to induce cytotoxic effects and apoptosis in human tumour cells by restoration of the transcriptional activity of mutated p53. This is believed to be mediated by a change in the conformation of mutated p53 protein, restoring DNA binding and activation of p53 target genes. We studied the effects of PRIMA-1 and commonly used antileukaemic drugs on AML cells from 62 patients. Cells were obtained from peripheral blood or bone marrow and were exposed to PRIMA-1, cytarabine, daunorubicin, chlorodeoxyadenosine and fludarabine. This study showed that PRIMA-1 had cytotoxic effects on AML cells. Conventional AML drugs were less effective in cells with hemizygous p53 deletion. Interestingly, our data indicated that PRIMA-1 was more effective in this subgroup of patients compared with patients with normal chromosome 17. Our data suggest that the concept of restoration of p53 protein by PRIMA-1 or a PRIMA-1-based new drug may increase the efficacy of AML treatment in patients with p53 mutations.

High single dose of mitoxantrone and cytarabine in acute non-lymphocytic leukemia: a pharmacokinetic and clinical study.

In a phase I-II study, the authors evaluated the intracellular pharmacokinetics, toxicity, and efficiency of a high dose of mitoxantrone given as first induction in acute non-lymphocytic leukemia. Twenty-two patients with previously untreated de novo ANLL were included and received 30 or 40 mg/m2 mitoxantrone on day 1 by intravenous infusion over 1 hour and 500 mg/m2 ara-C twice a day for 5 days. If there was no complete remission (CR), a second induction with ara-C, etoposide, and amsacrine was given. The CR rate after two courses with this regimen was 77%. Median duration of severe neutropenia was 18 days in the 30-mg/m2 group and 25 days in the 40-mg/m2 group. Two patients had fatal lung complications probably unrelated to mitoxantrone. A third patient had a possible mitoxantrone-induced reversible lung complication. In the leukemic cells, we found a high accumulation of mitoxantrone which, in contrast to the plasma concentration, remained stable during the 48 hours studied. Compared with previous results with 12 mg/m2 mitoxantrone, the AUC for intracellular concentrations versus time for the first 20 hours studied was increased by 150% to 0.638 nmol/mg cell protein x hour with 30 mg/m2 mitoxantrone and by 260% to 1.103 nmol/mg cell protein x hour with 40 mg/m2 mitoxantrone. In conclusion, a high dose of mitoxantrone results in a high intracellular exposure of the leukemic cells, which may be an advantage in improving survival of these patients.

Effects of PRIMA-1 on chronic lymphocytic leukaemia cells with and without hemizygous p53 deletion.

The tumour suppressor gene p53 is the most commonly mutated gene in solid tumours. Although less common in haematological malignancies, 10-15% of B-cell chronic lymphocytic leukaemia (B-CLL) cases carry a p53 mutation. Recently, the compound P53-dependent reactivation and induction of massive apoptosis (PRIMA-1) has been shown to induce cytotoxic effects and apoptosis in human tumour cells by restoration of the transcriptional activity of mutated p53. This is believed to be mediated by a change in the conformation of mutated p53 protein, restoring DNA binding and activation of p53 target genes. We studied the effects of PRIMA-1 and commonly used anti-leukaemic drugs on B-CLL cells from 14 patients with and without hemizygous p53 deletion. Cells obtained from peripheral blood or bone marrow were exposed to PRIMA-1 and fludarabine alone or in combination. PRIMA-1 showed cytotoxic effects on B-CLL cells from samples with and without hemizygous p53 deletion. Furthermore, conventional B-CLL drugs were less effective in cell samples with hemizygous p53 deletion and the response depended on the size of the p53 deleted clone. Finally, we found evidence for synergistic and additive effects of PRIMA-1 in combination with fludarabine.