Haematologica 2004;89: supplement no. 6 - Supplements ...

VIII Congress of the Italian Society of Experimental Hematology, Pavia, September 14-16, 200443association with a partial tandem duplication (PTD)of the MLL gene, reported in 20% to 73% of the cases.This rearrangement leads to in-frame fusion of aportion of the proto-oncogene with itself, and thisseems to represent a new genetic mechanism forleukemogenesis. Self-fusion of the MLL gene hasbeen also observed in patients with normal karyotype,although at a much lower frequency. Internaltandem duplication (ITD) has been demonstrated asa oncogene-activating mechanism also in anothergene involved in AML, namely the FLT3 gene, whichencode for a receptor tyrosine kinase widelyexpressed in hemopoietic cells and precursors. FLT3-ITD occurs in approximately 20% of unselected denovo adult AMLs, with a higher frequency in patientswith normal cytogenetics and is associated with poorprognosis in most series. Coduplication of MLL andFLT3 has been first observed by Jamal (Genes ChromCancer 2001) in two cases of AML, one also showingtrisomy 11.Aim of the study: to evaluate the presenceand the possible association of the MLL andFLT3 tandem duplication in 20 patients with myeloidmalignancies carrying a trisomy 11 as a primaryanomaly. Methods: Karyotype was analyzed bothwith standard cytogenetics and FISH with centromericprobe for chromosome11 and double-colorprobe for MLL gene. Southern blot was used to evaluateMLL rearrangement, and MLL-PTD was confirmedby RT-PCR (Caligiuri MA, Cancer Res 1996).FLT3-ITD was analyzed by RT-PCR (Nakao M et al. ,Leukemia 1996). Results: Diagnosis was AML, eitherde novo or secondary, in 15 patients; MDS in 4 cases;myeloproliferative disorder in accelerated phasein one case. We observed a MLL duplication in 41%of the patients with +11 (54% of AML patients). FLT3internal tandem duplication was observed in 31% ofthe patients with trisomy 11 (38.5% of AMLpatients), with a overall incidence similar to thatobserved in patients with normal karyotype. However,4 out of 5 (80%) of the FLT3-ITD + cases alsoshowed MLL-PTD, in contrast to FLT3-ITD negativecases where MLL-PTD was observed in 3/11 (27.3%).Median survival was 14.5 months for the wholegroup of +11 cases, 18 months for the patients negativefor the MLL-PTD and only 6 months for thepatients who had a MLL-PTD. Conclusions: Trisomy11 is associated with a group of AML and MDS characterizedby a poor clinical outcome; more than 40%of these patients also show the internal duplicationof MLL, and these cases have an extremely poorprognosis. FLT3-ITD appears to be quite common inpatients with MLL self-fusion and coexpression ofthe two anomalies could be explained on the basisof a common pathogenetic mechanism and/or similarresponse to genotoxic stress. FLT3 duplicationmay cooperate in determining the poor outcomeobserved in patients with trisomy 11.CO-39COMBINED ANALYSIS OF BCL-2 AND MDR1 PROTEIN IN 256CASES OF ACUTE MYELOID LEUKEMIAMazzone C, Maurillo L, Del Poeta G, Del Principe I,Venditti A, Panetta P, Cox C, Neri B, Ottaviani L,Amadori SCattedra-Divisione di Ematologia, Osp. S. Eugenio,Università di Rome "Tor Vergata", ItalyChemotherapy failure due to cellular drug resistanceis a major problem in the treatment of acutemyeloid leukemia (AML). The objectives of the studywas to investigate the coordinate expression ofMDR1 and bcl-2 proteins in de novo AML. Theexpression of the two proteins was analyzed by flowcytometry in a large series of 256 consecutive casesof AML. The results were achieved as percentage ofpositivity and relative mean fluorescence intensity(rMFI). To determine individual protein levels, anindex which equals the product of the percentage ofpositive cells and rMFI, was also generated. Using acut-off of 800 and 300 of index value for bcl-2 andMDR1, respectively, we identified 4 different classesof AML: 1) double neg; 2) single pos[bcl-2 + MDR1 − ];3) single pos[bcl-2-MDR1 + ]; 4) double pos. The highestincidence of double neg cases was observed inthe M2 class whereas double pos cases occurredmore frequently in the M4, M5 and M6 subgroups.Seventy-eight percent and 71% of M0 and M1,respectively, belonged to the single pos[bcl-2+MDR1-] group (p = 0.00001). Accordingly, therewas a significant association between single pos[bcl-2 + MDR1 − ] pattern and CD34 expression (p =0.00001). In the double pos group, 57% of the caseshad a poor prognosis karyotype, 37% intermediate,and only 6% of the patients had a good prognosiskaryotype (p = 0.04). Twenty-eight percent ofpatients belonging to the double pos categoryachieved CR, whereas for double neg, single pos[bcl-2 + MDR1 − ] and single pos[bcl-2-MDR1 + ] category,the CR rate was 69%, 52% and 56%, respectively (p= 0.00038). In multivariate analysis, the double posstatus independently affected frequency of CR (p =0.008). In conclusions, the combined analysis of bcl-2 and MDR1 allowed different classes of AML to beidentified. Bcl-2 is over-expressed in immature AML,conversely, MDR1 is over-expressed in terminally differentiatedAML. However, the occurrence of the twoproteins is not mutually exclusive since their coordinateexpression defines a distinct subset of AMLwith a very poor prognosis.haematologica vol. 89[suppl. n. 6]:september 2004