Prognostic Significance of EVI1 Defects in MDS/AML with 3q21q26 Abnormalities.
Authors: Bernasconi Paolo , Dambruoso Irene , Boni Marina , Cavigliano Paola Maria , Calatroni Silvia , Giardini Ilaria , Rocca Barbara , Zappatore Rita , Caresana Marilena , Astori Cesare , Castagnola Carlo , Alessandrino Emilio Paolo , Lazzarino Mario 
Published: October 2019

Chromosome 3q defects, namely inv(3)(q21q26)/t(3,3)(q21;q26), are revealed in about 2.5% of AML and in rare MDS patients (pts), are associated with a normal/high platelet count, tri-lineage dysplasia, resistance to intensive chemotherapy and poor survival. In these disorders ectopic EVI1 expression is the pathogenetically relevant molecular lesion. However, several pts with 3q21q26 rearrangements lack EVI1 expression and 9% of those without 3q21q26 defects present EVI1 over-expression. In addition, FISH, which can be used as an alternative tool for or an adjunct to RT-PCR to discover any EVI1 rearrangement, revealed an important breakpoint heterogeneity within this chromosomal region. Based on the above data, FISH was used to investigate 12 pts (7 MDS and 5 AML) with 3q21q26 rearrangements on conventional cytogenetics (CC). The goals of our study were to establish the incidence of EVI1 defects and to reveal any difference in morphological features and disease outcome between pts with and without EVI1 defects. The 12 pts were 4 females and 8 males with a median age of 60 years (range 35–80). Median follow-up was 22 months (range. 2–40). According to WHO classification, 2 MDS pts were diagnosed as Refractory Cytopenia with Multilineage Dysplasia (RCMD) and 5 as Refractory Anemia with Excess of Blasts type 2 (RAEB-2). Four of these 7 pts progressed into AML. Considering the 5 AML pts, 2 were diagnosed as M2 and 3 as M4. On clinical diagnosis CC showed a standard t(3,3)(q21;q26) in 5 pts, a translocation of 3p material onto band 3q26 in 2, a 3q21 deletion in 2, a complex rearrangement of band 3q26 in one, an inv(3)(q21q26) in one and a translocation involving 3p21 and 3q21 in one. FISH, carried out on cytogenetic preparation, used BAC probes obtained from Welcome Trust Sanger Institute (Cambridge, UK). The probes applied were those of the literature (Lahortiga et al, Genes Chrom & Cancer 2004; Poppe et al, Genes Chrom & Cancer 2006) and other probes covering the RPN1, EVI1, MDS1 genes. EVI1 defects had an incidence of 50%. EVI1 gene was translocated in 4 t(3;3) pts (3 RAEB-2 and one AML), amplified along with MLL in a RAEB-2 pt and deleted in the 2 AML pts with a 3q21 deletion on CC. Interestingly, no EVI1 defect was discovered in a t(3;3) RAEB-2 pt and in an inv(3)(q21q26) RCMD pt. Tri-lineage dysplasia was observed in all MDS pts independently of any EVI1 defect. Median survival of the 5 pts with either EVI1 translocation or amplification was 6 months (range 2–32), that of the 7 pts without any EVI1 defect was 26 months (range 4–40). A progression in AML occurred in all the 3 MDS pts with EVI1 defects and in one of the 4 MDS pts without any defect. A total of 8 pts, including 3 of the 4 AML progressed from MDS, were submitted to intensive chemotherapy. A complete remission (CR) was achieved in only one of the 4 pts with EVI defects and in 3 of the 4 pts without any defect. Two CR pts, one with and one without any EVI1 defect, were submitted to allogeneic bone marrow transplantation (allo-BMT). The pt with the EVI1 translocation relapsed, but succeeded in entering a second CR. In conclusion, EVI1 defects

were revealed in 50% of pts, were not required for evoking the dysplastic changes associated with 3q21q26 rearrangements, were associated with a high risk of AML evolution in MDS pts, caused a short survival and resistant AML.