ALBERT

Description: AMLs constitute an heterogeneous group of hematopoietic stem cell disorders of rather poor prognosis. Abnormal activation of signaling pathways including STAT, MAPK and NF-KB have been described in AMLs and could constitute new targets for therapy. In this study, we focused on the PI3K/AKT and mTOR/P70S6K activity in primary blast cells purified from the bone marrow of patients with primary (n = 54) or secondary (n =10) AMLs. Patients with de novo AMLs were issued from the AML2001 French Multicenter Trial directed by the GOELAMS. The FAB classification was the following: M0 (n = 8), M1 (n = 10) M2 (n = 21), M4 (n = 10), M4eo (n = 2), M5 (n = 11), unknown AML (n = 2). In 58% of these patients, a constitutive activation of PI3K/AKT was detected in blast cells by western blot analysis showing AKT and FOXO3a phosphorylation, and confirmed by immunofluorescence confocal microscopy and flow cytometry analysis in CD34+ blast cells. Constitutive GAB1/2 phosphorylation was detected in all PI3K+ patients. However, we did not find any correlation between PI3K activation and FLT3 gene mutations. PTEN and SHIP-1 expression was normal in all tested PI3K+ patients. Proliferation (3H thymidine incorporation) was significantly increased in PI3K+ samples compared to PI3K- samples (p=0.001). The mTOR/P70S6K pathway was activated and the mTOR inhibitor rapamycin selectively reduced proliferation of PI3K+ samples. We determined the expression of the alpha, beta and delta isoforms of the catalytic sub-unit of PI3K (p110) in leukemic cells and found that p110 delta was the only consistently expressed isoform. In 8 PI3K+ samples tested, IC87114 (ICOS Corporation), a specific p110delta inhibitor compound used at 10μM totally suppressed AKT and FOXO3a phosphorylation. IC87114 inhibited proliferation of PI3K+ leukemic cells whereas it did not induce apoptosis. IC87114 did not significantly impaired the proliferation of PI3K- blast cells. Interestingly, IC87114 did not inhibit the proliferation or clonogenicity of CD34+ cord blood cells cultured in SCF, FLT3L and TPO used as controls. Overall, our results report, a/ a constitutive activation of PI3K in 58% of AML, b/ no correlation between FLT3 gene mutations and PI3K positivity, c/ no implication of PTEN or SHIP-1 phosphatases in PI3K activation, d/ a major role of the p110 delta isoform of PI3K in leukemic cell proliferation, e/ a potential therapeutic value of inhibiting mTOR and P110 delta activity.

Description: It has been shown that all-trans retinoic acid (ATRA) at doses of 45 to 100 mg/m2/d induces complete remission (CR) of acute promyelocytic leukemia (APL) by a differentiation process. To date, ATRA dose-ranging studies have not yet been evaluated. Thus, we initiated in May 1990 a multicenter study with ATRA at a lower dose of 25 mg/m2/d until CR. Thirty patients with APL were treated with ATRA, of whom 12 were previously untreated, 14 were in first relapse, and 4 had failed after conventional first induction chemotherapy. Twenty-four of 30 achieved CR, 3 failed, and 3 died before day 30. Median time to CR was 45 days. Hyperleucocytosis (14 to 43 x 10(9) white blood cells per liter) was observed in 9 patients between days 10 and 23. Clinical complications that may have been related to the retinoic acid syndrome were observed in 8 patients, of whom 3 died. Pharmacokinetics studies were performed in 5 patients. Peak plasma concentrations and mean area under the concentration-time curve were not lower than previous levels obtained under the 45 mg/m2 dose. Overall, our study shows that there is no difference in terms of therapeutic efficacy, triggering of hyperleukocytosis, or retinoic acid syndrome and pharmacokinetic results with ATRA at 25 or 45 mg/m2/d.

Description: It has been shown that all-trans retinoic acid (ATRA) at doses of 45 to 100 mg/m2/d induces complete remission (CR) of acute promyelocytic leukemia (APL) by a differentiation process. To date, ATRA dose-ranging studies have not yet been evaluated. Thus, we initiated in May 1990 a multicenter study with ATRA at a lower dose of 25 mg/m2/d until CR. Thirty patients with APL were treated with ATRA, of whom 12 were previously untreated, 14 were in first relapse, and 4 had failed after conventional first induction chemotherapy. Twenty-four of 30 achieved CR, 3 failed, and 3 died before day 30. Median time to CR was 45 days. Hyperleucocytosis (14 to 43 x 10(9) white blood cells per liter) was observed in 9 patients between days 10 and 23. Clinical complications that may have been related to the retinoic acid syndrome were observed in 8 patients, of whom 3 died. Pharmacokinetics studies were performed in 5 patients. Peak plasma concentrations and mean area under the concentration-time curve were not lower than previous levels obtained under the 45 mg/m2 dose. Overall, our study shows that there is no difference in terms of therapeutic efficacy, triggering of hyperleukocytosis, or retinoic acid syndrome and pharmacokinetic results with ATRA at 25 or 45 mg/m2/d.