Mechanisms of resistance in acute promyelocytic leukaemia failing treatment with oral arsenic trioxide

Dr Singh, Gill Harinder Harry   (Principal Investigator (PI))

Professor Leung Anskar Yu Hung   (Co-Investigator)

Professor Kwong Yok Lam   (Co-Investigator)

3

2015-09-01

2015-11-30

43000

Mechanisms of resistance in acute promyelocytic leukaemia failing treatment with oral arsenic trioxide

Acute promyelocytic leukaemia, Oral arsenic trioxide, Resistance

Blood/Hematology,Cancer

201509159007

Seed Fund for PI Research – Basic Research

2015

Completed

ABSTRACT Background. Acute promyelocytic leukaemia (APL) is a distinct subgroup of acute myeloid leukaemia (AML) characterized by translocation t(15;17) (q22;q12). Up to 20% of patients relapse after initial remission. Arsenic trioxide (As2O3) is highly effective for relapsed APL and is increasingly used as frontline treatment for newly diagnosed APL. It is anticipated that an increasing number of patients will be exposed to As2O3-based therapy and drug resistance to As2O3 is a consequent emerging clinical problem in the modern management of APL. We have developed an oral formulation of As2O3 and it is currently the standard of care for maintenance after first complete remission (CR1) and re-induction for relapsed APL in Hong Kong. Despite its efficacy as maintenance after CR1 and as re-induction in relapsed APL, subsequent relapse after oral As2O3-based treatment has been observed in up to 40% of patients and is associated with a dismal outcome. The presence of fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) was significantly associated with relapse during oral As2O3. We hypothesize that FLT3-ITD confers resistance to As2O3 and FLT3-ITD+ APL clones persist during As2O3. Clonal selection and progression occurs leading to subsequent relapse. Objectives. To prove this hypothesis, we have designed a series of experiments that may enable us to understand the mechanisms of resistance to As2O3, using FLT3-ITD as an example. The following issues will be addressed: Will FLT3-ITD in APL confer resistance to As2O3? Will FLT3-ITD+ APL clones exhibit differences in leukemia-initiating activity? What are the genome-wide changes in APL that demonstrate resistance to As2O3? Methods and Plans. FLT3-ITD will be transfected to the human APL cell line NB4 to establish an in-vitro model of FLT3-ITD+ APL. Changes in cellular morphology, differentiation, apoptosis, proliferation, clonogenic activity associated with FLT3-ITD will be evaluated. Leukemia-initiating activity of FLT3-ITD and FLT3 wild-type APL will be evaluated by xenogeneic transplantation into NSG-3GS mice. Retrospective and prospective patients with APL will be serially evaluated for FLT3 mutations during oral As2O3-based therapy and on subsequent relapse. Genome-wide changes on primary APL cells relapsing after exposure to As2O3 will be evaluated using exome sequencing. Significance. The original clinical observation that the presence FLT3-ITD in APL patients is associated with oral As2O3-based treatment failure has provided a solid foundation for this proposal. Preliminary studies have been performed to ensure technical feasibility of the proposal. The proposal will provide important insight to the mechanism of resistance to arsenic trioxide.