Correspondence
1991
Coexistence of AML1/RUNX1 and BCR-ABL point mutations in an imatinib-resistant form of CML Leukemia (2005) 19, 1991–1992. doi:10.1038/sj.leu.2403931; published online 8 September 2005 TO THE EDITOR
CML is a myeloproliferative disorder characterised by the presence of the Philadelphia chromosome and the formation of the BCR-ABL fusion gene resulting in an enhanced tyrosine kinase (TK) activity. CML prognosis has been radically improved by the use of the TK inhibitor imatinib mesylate (IM). Despite the achievement of complete cytogenetic remissions in more than 75% of patients1 treated with IM, some patients are primary resistant or may relapse. Among different mechanisms of resistance described, mutations in the active TK site of the BCR-ABL gene have been frequently reported.2,3 Molecular mechanisms underlying progression from chronic phase to blast crisis are not well understood. Blast crisis is characterised by the acquisition of chromosomal and molecular abnormalities favoured by genomic instability that lead to enhanced survival and differentiation arrest of the malignant clone. Several mechanisms have been described to contribute to these features, and, in particular, downregulation of C/EBPa and upregulation of HOXA9 and EVI1.4 We report here the case of a 56-year-old man for whom CML in chronic phase was diagnosed on 5 September 2002. In his medical history, we noted a prostate adenoma, arterial
hypertension and hypercholesterolemia. He was initially asymptomatic. Leukocytes were at 213 G/L (blasts 2%, basophils 0%) and platelets at 111 G/L. Sokal prognostic score was intermediate. Cytogenetic analysis did not show additional abnormalities, and molecular analysis revealed the M-BCR form of BCR-ABL (p210). He was first treated with hydroxyurea. A well-tolerated combination of interferon and cytarabin started on 25 November 2002 has led to complete haematological remission. However, a haematological relapse (leukocytes 38.800 g/l, blasts 2%, basophils 1%) occurred on 14 February 2003. We then started IM at 400 mg/day. This treatment was also well tolerated and a second haematological remission was obtained within a month. However, BCR-ABL transcript levels after 3 months of this treatment remained stable. At 4 months after the onset of IM, the complete haematological response continued, but cytogenetic analysis concluded in the persistence of 100% cells bearing the Philadelphia chromosome and in the emergence of an additional trisomy 21 (10 June 2003). IM was increased to 600 mg/day. In August 2003, the accelerated phase disease was confirmed by the presence of 13% of blasts in peripheral blood and 12% of blasts in bone marrow aspiration. He underwent HLA-identical sibling peripheral blood stem cell transplantation on 4 September 2003 with an attenuated conditioning regimen consisting of busulphan (2 mg/kg/day, 2 days), fludarabine (30 mg/m2/day, 4 days) and antithymoglobulin (ATG 5 mg/kg/day, 2 days). CD34 þ cell dose was
Figure 1 Evolution of leukocytosis (solid line) and of BCR-ABL transcript levels (determined by quantitative RT-PCR) (solid line with circles), with regard to treatments, cytogenetic analysis and findings of the AML1/RUNX1 and BCR-ABL mutations. (HU: hydroxyurea, IM: imatinib mesylate, Bus: busulphan, IFN: interferon, AraC: cytarabine, allo-SCT: allogeneic stem cell transplantation, Ph: chromosome Philadelphia, Mut: mutation).
Correspondence: Dr C Preudhomme, Laboratoire d’He´matologie A, Hoˆpital Calmette, CHRU de Lille, France; Fax: þ 33 320 44 55 10; E-mail:
[email protected] Received 24 June 2005; accepted 27 July 2005; published online 8 September 2005 Leukemia
Correspondence
1992
Leukemia
7.5 106/kg of recipient weight. He recovered from neutropenia 12 days after reinjection and we observed a rapid elevation of the leukocytes (mature granulocytes without blast excess) with a full recipient chimaerism phenotype. IM therapy at 400 mg/day during 10 days followed by busulphan treatment at 2 mg/day during 1 month, combined with the withdrawal of the immunosuppressive therapy, allowed haematological remission. Chimaerism was then converted to full-donor phenotype. The evolution was marked with undetectable levels of BCR-ABL transcripts (Figure 1), and by the onset of a grade IV cutaneous GVH controlled by reintroduction of an immunosuppressive therapy. At the time of emergence of the trisomy 21, screening for a mutation in the AML1/RUNX1 gene by direct sequencing revealed a missense mutation R139P within the runt domain. This mutation is known to confer loss of function of this gene (impaired DNA binding and transactivation). The same findings were noted on accelerated phase samples and the retrospective analysis of samples from diagnosis demonstrated the presence of this mutation in a heterozygous form. Furthermore, we identified by direct sequencing a BCR-ABL M244V mutation at the time of IM resistance and acceleration. This mutation was not present in previous samples, and in particular was not found at the diagnosis of the disease. AML1 is a major gene contributing to definitive haematopoiesis. Clustered mutations in the AML1 runt terminal region were mainly described in (i) AML-M0 (often biallelic mutations), (ii) familial platelet disorder (inherited AML1 heterozygous mutation leading to AML predisposition), (iii) haematological malignancies with trisomy 21, and (iiii) MDS/AML secondary to ionising radiation or chemotherapeutic agents exposition.5–7 More recently, mutations in the C-terminal region of the gene have been described, especially in MDS/AML.8 To our knowledge, it is the first time that an AML1/RUNX1 mutation is described in CML in chronic phase. Here, we observed the acquisition of a trisomy 21 in the Ph1 þ clone, which is a rare event in the course of CML. The duplication of chromosome 21 bearing the mutated AML1 gene occurred only 2 months before the accelerated phase and may have contributed to the differentiation arrest associated with the progression of CML. As a result of its low IC50 assessed by biochemical analysis,9 the BCR-ABL M244V mutation probably does not induce an effective resistance to IM. Nevertheless, both BCR-ABL and AML1/RUNX1 mutations may reflect genomic instability, and the further acquisition of trisomy 21 and subsequent duplication of the mutated AML1/RUNX1 allele could represent a major event responsible for the progression of CML. This observation underlies the possible molecular heterogeneity of CML at diagnosis. Factors that could define more precisely the disease at diagnosis (such as microarray analysis or the screen for mutation in some defined genes, such as AML1/ RUNX1 when trisomy 21 is observed) may be complementary to
the classical scores (such as Sokal and Hasford scores) for therapeutic decision adjustment.
Acknowledgements This work was supported by the Fondation de France (Comite´ Leuce´mie), the Ligue contre le Cancer (Comite´ Nord) and the Canceropoˆle (Axe Onco-he´matologie). 1 S Corm1,3,4 INSERM Unite´ 524, Institut de Recherche sur le 1,4 Cancer de Lille, Lille Cedex, France; V Biggio 2 Laboratoire de Ge´ne´tique Me´dicale, C Roche-Lestienne1,4 1,2 Hoˆpital Jeanne de Flandre, CHRU de Lille, J-L Laı¨ Lille Cedex, France; I Yakoub-Agha3 3 Service des Maladies du Sang, Hoˆpital Huriez, N Philippe4 CHRU de Lille, Lille Cedex, France; F-E Nicolini5 4 Laboratoire d’He´matologie A, Hoˆpital Calmette, T Facon3 CHRU de Lille, Lille Cedex, France; and C Preudhomme1,4 5
Service d’He´matologie Clinique, Hoˆpital Edouard Herriot, Lyon, France
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