Relation of P-glycoprotein expression with spontaneous in vitro apoptosis in B-cell chronic lymphocytic leukemia.

Prolonged lifespan of monoclonal lymphocytes in B-cell lymphocytic leukemia (B-CLL) arises from their resistance to programmed cell death. In contrast, when cultured in vitro, B-CLL tumour cells rapidly undergo apoptosis. There is mounting evidence that P-glycoprotein (P-gp), an adenosine triphosphate-binding cassette (ABC) family transporter, plays a significant role in the regulation of apoptosis induced by various stimuli. Since P-gp is commonly expressed in B-CLL cells, we aimed to establish whether its expression level influences resistance to spontaneous apoptosis in B-CLL. For that purpose, P-gp expression by UIC2 antibody staining and P-gp activity by rhodamine 123 (Rh123) efflux in presence or absence of P-gp inhibitor verapamil were studied in peripheral blood lymphocytes obtained from 43 previously untreated B-CLL patients. Simultaneously, the percentage of cells undergoing spontaneous in vitro apoptosis (apoptotic index, AI) by means of activation of caspases and annexin-V-based assays was evaluated. The AI were higher in B-CLL cells than in normal peripheral blood mononuclear cells (medians of AI 27.7% vs 3.9%, p=0.0001 and 34.7% vs 7.4%, p=0.0038, in 24 and 48-hour culture respectively). The AI were also higher among female patients as compared to male patients (medians: 29.7 vs 19.2 p=0.048). Interestingly, we found moderate inverse correlation between P-gp protein expression and AI after 24-hour culture in analysed B-CLL samples (r= -0.36, p=0.019). Moreover, P-gp positive B-CLL samples expressed significantly higher AI than P-gp negative samples with an arbitrary cut-off at Kolmogorov-Smirnov statistics D-value 0.2 (medians of AI 18.4% vs 29.7%, p=0.026). Based on these results we suggest that P-gp expression has some protective effect on B-CLL cell survival in vitro. The difference in the rates of spontaneous apoptosis among male and female patients may contribute to gender-dependent variations in clinical outcome in B-CLL.

The treatment of acute myeloid leukemia with mitoxantrone, etoposide and low-dose cytarabine in elderly patients - a report of Polish Acute Leukemia Group (PALG) phase II study.

The common dilemma in the treatment of elderly patients with acute myeloid leukemia (AML) is whether to use intensive myelosuppresive therapy with higher risk of treatment related mortality (TRM), but a chance for complete remission (CR), or to treat less intensively in order to prolong survival time with a better quality of life. The aim of this prospective, phase II study was to assess the efficacy and toxicity of low dose combination induction treatment consisted of cytarabine at a dose of 10 mg/m2 every 12 h s.c. for 7 days, VP-16 at a dose of 100 mg/day p.o. for 7 days and mitoxantrone at a dose of 6 mg/m2 i.v daily on days 1-3. Two induction courses were planned. In the group of 44 patients 12 (27%) achieved CR, 4 (9%) patients were in PR and there were 9 (20%) early deaths (ED). Age, performance status, preceding myelodysplastic syndrome, karyotype, WBC and % of blasts in bone marrow were not significant prognostic factors for CR probability. The following initial factors appeared to be related to a shorter duration of survival time from the start of treatment: age >70 (p<0.03), poor performance status (p<0.03), and % of BM blasts 50 (p<0.05). We conclude that, despite promising results in the pilot study the efficacy of this induction treatment is not better than the efficacy of other regimens. The hematological toxicity of this treatment seems to be comparable with "3+7" regimen.