EVI-1 oncogene expression predicts survival in chronic phase CML patients resistant to imatinib Mustafa Daghistani Department of Haematology, Imperial College London at Hammersmith Hospital, Du Cane Road, London, UK
CML an overview A clonal myeloproliferative disorder of the pluripotent hematopoietic stem cell t(9;22)(q34;q11) 1 to 2 cases per 100,000 15% of all adult leukaemias Triphasic - indolent chronic phase, accelerated and terminal acute stage q34.1 9 der9 22 Ph q11.2 Philadelphia chromosome pathognomic marker BCR-ABL fusion - deregulated tyrosine kinase activity: rational target for therapy
Cum Survival CML therapy: conventional v s tyrosine kinase inhibitor (TKI) 1.0.9.8.7 Imatinib (STI571, Glivec).6.5.4 Interferon (CML 3 MRC).3.2.1 0.0 0 1000 2000 3000 4000 5000 6000 7000 (survival time from diagnosis) 20-30% patients imatinib resistant/intolerant KD mutations best-characterised resistance mechanism (30-50%) Other mechanisms unknown
Second-Generation (2G) TKIs Dasatinib Nilotinib CCR or MCR in up to 60% of imatinib resistant patients Dasatinib active against all mutations except T315I Resistance still a clinical challenge
Established and proposed mechanisms of TKI resistance Gastrointestinal absorption/first pass metabolism Plasma protein binding Cellular drug influx and efflux Enzymatic inactivation Increase in BCR-ABL expression BCR-ABL mutations Activation of BCR-ABL independent pathways
3q26 rearrangements in haematological malignancy EVI1 (EVI1/MDS1) gene Oncogene, PR-domain protein EVI-1 translocations are the primary events in aggressive myeloid malignancy inv(3), t(3;21)(q26;q22) etc inv(3)(q21q26) inv(3) 3 De Melo et al. Leukemia, 2007 Over expression in absence of 3q26 rearrangement 3 common der(3) in AML, CML: >60% AP/BC, 10% CP (Ogawa et al, 1996) der(21) We previously observed high frequency of 3q26 abnormality in BC patients resistant to 2G-TKI (AR at UKCCG 2008) Questions: 1) Can EVI1 expression be found in CP patients with imatinib resistance 2) What is the correlation with response to 2G-TKI.
Methods and patient materials 75 consecutive patients with Philadelphia (Ph) chromosome-positive CML in CP resistant to imatinib who were treated with dasatinib (n=61) or nilotinib (n=14) No patient harbored a 3q26 rearrangement in the Ph-positive clone The median follow up from starting 2G-TKI was 30 months; 95% of the patients were followed for at least one year. EVI-1 expression was measured using a multiplex TaqMan assay Granulocytes from 30 normal individuals showed no evidence of EVI1 expression by this method
Results EVI-1 expression was detected by real-time PCR in 8 (10.7%) of the 75 patients No association between EVI1 expression and any clinical/lab characteristics or characteristics commonly associated with progression to advanced phase none of the EVI1+ patients harboured a T315I mutation Retrospective analysis revealed that EVI-1 expression was not present in diagnostic samples of the 8 patients who were later found to express the protein or in a further 23 CML patients who were negative throughout disease
Probability of OS Probability of EFS EVI1 expression predicts for shorter survival in imatinib resistant CP patients Patients with positive EVI-1 expression at the onset of 2G-TKI therapy had a significantly lower 30 month EFS (43.7 vs 90.6%, p=0.0001), PFS (43.7 vs 93.8%, p<0.0001), OS (47.5 vs 95.2%, p=0.0003) and cumulative incidence of CCyR (12.0% vs 59.7%, p=0.05) 1.0 0.9 1.0 0.9 0.8 0.8 0.7 0.7 0.6 0.5 p=0.0003 0.6 0.5 p=0.0001 0.4 0.4 0.3 0.3 0.2 0.1 0.0 0 6 IM resistant, EVI-1-negative, n=67 IM resistant, EVI-1-positive, n=8 12 18 24 30 Months from start of 2G-TKI 0.2 0.1 0.0 0 6 12 18 24 Months from start of 2G-TKI 30 EVI1 expression remained an independent predictors for OS, EFS and PFS on multivariate analysis (along with achievement of at least a minor cytogenetic response (MiCyR) during the prior imatinib therapy)
Probability of OS After 3 months 1.0 0.9 0.8 0.7 p=0.003 p=0.01 MiCyR, n=42 No CyR, no EVI-1 expression, n=27 No CyR, EVI-1 expression, n=6 0.6 0.5 0.4 0.3 p=0.0001 0.2 0.1 0.0 0 6 12 18 24 30 Months from start of 2G-TKI
Summary EVI1 expression is detectable in approximately 10% of imatinib-resistant patients without 3q26 rearrangement Expression appears to be acquired over the course of the disease Detection of expression of the EVI-1 oncogene in imatinib-resistant CP CML patients at the start of 2G-TKI therapy is a strong predictor for disease progression and shorter survival. EVI1 expression may therefore be a marker of impending disease acceleration In patients who fail to achieve MiCyR after 3 months of 2G-TKI therapy, EVI-1 expression status may help to distinguish those patients with poor disease outcome from those who have a significantly higher chance of long-term progression-free survival. Measurement of EVI-1 expression at the point of imatinib failure may therefore identify patients who would fare badly on a 2G-TKI regimen and might be better served by early referral for transplant.
Acknowledgements Alistair Reid Jamshid Sorouri-Khorashad Valeria Melo Philippa May Letizia Foroni Gareth Gerrard Dragana Milojkovic David Marin John Goldman Jane Apperley Supported by Hammersmith Hospitals Trustees Research Committee