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

VIII Congress of the Italian Society of Experimental Hematology, Pavia, September 14-16, 2004191completed on December 2003.After therapy heachieved a complete remission of the lymphoproliferativedisorder and a partial remission of CMML.Patient is presently alive and without treatment, incontinous complete remission for lymphoma but withall the features of chronic myelomonocitic leukemia,without transfusion requirement. Associationbetween lymphoma and CMML is rare. Only three arethe published cases until to-day. Two of them are T-lineage lymphomas, and the remaining a breast B-lymphoma. Coexisting untreated lymphoproliferativedisease and myelodisplasia has been reported ascasual in a serie of 1198 patients affected by myelodysplasias(Forlensa, Leukemia and Lymphoma 1996).Only in 5 diagnosed CMMLs concomitant lymphoidand myeloid disease was found. However, all lymphomaswere B cell low grade NHLs. This is, at ourknowledgment, the first report of a B cell high gradeNHL coexisting at diagnosis with CMML.PO-210ABERRANT SOMATIC HYPERMUTATION OF PROTO-ONCOGENESIN POST-TRANSPLANT LYMPHOPROLIFERATIVE DISORDERSCerri M, 1 Capello D, 1 Muti G, 2 Rambaldi A, 3 PaulliM, 4 Gloghini A, 5 Berra E, 1 Deambrogi C, 1 Rossi D, 1Vendramin C, 1 Morra E, 2 Pasqualucci L, 6 Carbone A, 5Gaidano G 11Hematology Unit, Department of Medical Sciences& IRCAD, Amedeo Avogadro University of EasternPiedmont, Novara; 2 Division of Hematology, OspedaleNiguarda Ca' Granda, Milan; 3 Division of Hematology,Ospedali Riuniti, Bergamo; 4 Department ofPathology, IRCCS Policlinico San Matteo/Universityof Pavia; 5 Division of Pathology, Centro di RiferimentoOncologico, Istituto Nazionale Tumori, IRCCS,Aviano, Italy; 6 Institute for Cancer Genetics, ColumbiaUniversity, New York, USAPost-transplant lymphoproliferative disorders (PTLD)are a heterogeneous group of lymphoproliferationsarising in solid organ transplant recipients recivingimmunosuppresive therapy. To date, only few molecularlesions of the cellular genome have been associatedto the pathogenesis of PTLD. It has been recentlyshown in diffuse large B-cell lymphoma (DLBCL) ofthe immunocompetent host and in HIV-non-Hodgkinlymphoma that aberrant somatic hypermutation(SHM) activity can affect multiple genetic loci, includingthe proto-oncogenes PAX-5, Rho/TTF, PIM-1 andc-MYC. Mutations involve 5' untranslated regions aswell as coding sequences, are independent of chromosomaltranslocations to the immunoglobulin (Ig)genes and display features and distribution typical ofIgV SHM, suggesting that this process is malfunctioningin lymphoma. The knowledge that PTLD derive fromGC-related B-cells that have been exposed to the SHMprocess prompted our analysis of aberrant somatichypermutation in PTLD. Twenty-five monoclonal B-cellPTLD classified into polymorphic PTLD (P-PTLD; n=5)and monomorphic lymphoma including DLBCL (n=18),and BL/BLL (n=2) formed the basis of our study. Mutationalanalysis was performed by amplification anddirect sequencing of a region spanning up to 1.5 Kbfrom the transcription start site and previously shownto harbor over 90% of the mutations. Mutations targetingat least one of the 4 proto-oncogenes werefound in 7/25 (28%) PTLD. All mutated cases were representedby DLBCL (7/18; 38.8%). One single case harboredmutations in more than one gene. PAX-5 wasmutated in 4/25 (16%) PTLD, c-MYC was mutated in3/25 (12%) PTLD, Rho/TTF was mutated in 1/25 ( 4%)PTLD, while PIM-1 was not mutated in any case. Mutationswere independent of EBV infection since aberranthypermutation occurred in 3/13 EBV positive PTLD and4/12 EBV negative PTLD. The mutation frequency ofeach gene in mutated cases ranged from 0.4 to 8.5×10 -3bp. Mutations were of somatic origin, as confirmedby analysis of normal DNA from the same patient inselected cases. Mutations were heterozygous andshared features of IgV SHM process. These included: i)the predominance of single base pair substitutions(n=29), with only one deletion; and ii) a preference fortransitions (n=16) over transvertions (n=13), with ahigher than expected transition/transvertion ratio(observed=1.23; expected=0.5). In the case of c-MYC,one mutation was located in the coding exons leadingto a Ile129Val aminoacid substitution affecting thetransactivation domain of the c-MYC protein and carryingpotential functional consequences. Based onnonparametric statistical analysis (Kruskal Wallis andMann-Whitney test with Bonferroni adjustment formultiple comparison), the frequency of aberrant hypermutationin PTLD/DLBCL did not differ from that ofAIDS-DLBCL but was lower than that reported in DLB-CL of immunocompetent hosts (p