P-Glycoprotein Expression in Acute Myeloid Leukaemia Cells at Diagnosis: Its relationship to Daunorubicin or Idarubicin Induction Therapy and Survival.

We investigated the expression of P-glycoprotein (P-gp) in 50 adults with de novo diagnosed acute myeloid leukaemia (AML) and the relationship between presence of P-gp in leukaemic cells and efficacy, as remission induction and survival rate, of two different anthracyclines, daunorubicin (DNR) and idarubicin (IDR). We found that 30 out of 50 patients (60%) were negative (Group 1) and 20 (40%) were positive (Group 2) for P-gp expression evaluated by mean of MRK16 MoAb using a cut-off of 10% positive cells. Thirty-five out of 50 patients (70%) obtained complete remission (CR); depending on P-gp expression, the CR rate was 80% for group 1 and 45% for group 2 (p < 0.005). The median duration of overall survival was 20 months for patients in Group 1 as compared with 10 months for patients of Group 2 (p < 0.005). Regarding the anthracycline used, no significant difference in CR was observed in patients of Group 1 (75% of CR with DNR vs. 90% with IDR); Group 2 obtained 40% of CR with DNR vs. 70% with IDR (p < 0.005). The median duration of overall survival (OS) with the two regimens was comparable in Group 1, while it was significantly longer in patients of Group 2 treated with IDR compared with DNR regimen (p < 0.005). These results confirm the prognostic value of P-gp expression in AML at first appearance and we suggest that idarubicin could be a valid anthracycline drug in the treatment of AML to be evaluated as potential drug of choice in patients with primary or drug-induced multidrug resistance

Role of α1 Acid Glycoprotein in the In Vivo Resistance of Human BCR-ABL+ Leukemic Cells to the Abl Inhibitor STI571

Background: Chronic myeloid leukemia is caused by a chromosomal translocation that results in an oncogenic fusion protein, Bcr-Abl. Bcr-Abl is a tyrosine kinase whose activity is inhibited by the antineoplastic drug STI571. This drug can cure mice given an injection of human leukemic cells, but treatment ultimately fails in animals that have large tumors when treatment is initiated. We created a mouse model to explore the mechanism of resistance in vivo. Methods: Nude mice were injected with KU812 Bcr-Abl+ human leukemic cells. After 1 day (no evident tumors), 8 days, or 15 days (tumors >1 g), mice were treated with STI571 (160 mg/kg every 8 hours). Cells recovered from relapsing animals were used for in vitro experiments. Statistical tests were two-sided. Results: Tumors regressed initially in all STI571-treated mice, but all mice treated 15 days after injection of tumor cells eventually relapsed. Relapsed animals did not respond to further STI571 treatment, and their Bcr-Abl kinase activity in vivo was not inhibited by STI571, despite high plasma concentrations of the drug. However, tumor cells from resistant animals were sensitive to STI571 in vitro, suggesting that a molecule in the plasma of relapsed animals may inactivate the drug. The plasma protein α1 acid glycoprotein (AGP) bound STI571 at physiologic concentrations in vitro and blocked the ability of STI571 to inhibit Bcr-Abl kinase activity in a dose-dependent manner. Plasma AGP concentrations were strongly associated with tumor load. Erythromycin competed with STI571 for AGP binding. When animals bearing large tumors were treated with STI571 alone or with a combination of STI571 and erythromycin, greater tumor reductions and better long-term tumor-free survival (10 of 12 versus one of 13 at day 180; P<.001) were observed after the combination treatment. Conclusion: AGP in the plasma of relapsed animals binds to STI571, preventing this compound from inhibiting the Bcr/Abl tyrosine kinase. Molecules such as erythromycin that compete with STI571 for binding to AGP may enhance the therapeutic potential of this dru

Molecular purging of multiple myeloma cells by ex-vivo culture and retroviral transduction of mobilized-blood CD34+ cells

<p>Abstract</p> <p>Background</p> <p>Tumor cell contamination of the apheresis in multiple myeloma is likely to affect disease-free and overall survival after autografting.</p> <p>Objective</p> <p>To purge myeloma aphereses from tumor contaminants with a novel culture-based purging method.</p> <p>Methods</p> <p>We cultured myeloma-positive CD34⁺PB samples in conditions that retained multipotency of hematopoietic stem cells, but were unfavourable to survival of plasma cells. Moreover, we exploited the resistance of myeloma plasma cells to retroviral transduction by targeting the hematopoietic CD34⁺cell population with a retroviral vector carrying a selectable marker (the truncated form of the human receptor for nerve growth factor, ΔNGFR). We performed therefore a further myeloma purging step by selecting the transduced cells at the end of the culture.</p> <p>Results</p> <p>Overall recovery of CD34⁺cells after culture was 128.5%; ΔNGFR transduction rate was 28.8% for CD34⁺cells and 0% for CD138-selected primary myeloma cells, respectively. Recovery of CD34⁺cells after ΔNGFR selection was 22.3%. By patient-specific Ig-gene rearrangements, we assessed a decrease of 0.7–1.4 logs in tumor load after the CD34⁺cell selection, and up to 2.3 logs after culture and ΔNGFR selection.</p> <p>Conclusion</p> <p>We conclude that <it>ex-vivo </it>culture and retroviral-mediated transduction of myeloma leukaphereses provide an efficient tumor cell purging.</p