Susanna Akiki WMRGL 2009 Acute Promyelocytic Leukemia with t(15;17) (q22;q21) developing inv(16)(p13q22) secondary AML

Susanna Akiki WMRGL 2009 Leukemia clonal neoplasia, consequence of an accumulation of genetic damage Specific leukemia’s associated with very specific genetic events Mutation arises in a single cell Emerges as a substantial population of cells

Susanna Akiki WMRGL 2009 Acute Myeloid Leukemia Consequence of acquired somatic mutations in haematopietic progenitors- myeloid lineage Typically involve translocations Target is often a transcription factor involved in haemopoiesis Create a novel gene fusion Implicated in leukemiagenesis Gillilands 2 hit hypothesis of co operating mutations in the pathogenesis of AML two distinct classes of mutation required to induce leukaemia Mutations that block cellular differentiation Mutations that increase cell proliferation & survival Genetic event occur well characterised & identify specific subsets with prognostic significance

Susanna Akiki WMRGL 2009 Acute Promyelocytic Leukemia APL subtype of AML characterised by Specific recurrent translocation t(15;17) Chimeric PML-RARA fusion encodes a novel protein Acts as a transcriptional repressor APL particularly sensitive to treatment Maturation block overcome by Retinoic acid Highly effective in combination with chemo Prolonged remission achieved in ~ 80% patients

Susanna Akiki WMRGL 2009 PML-RARA Monitoring t(15;17) predicts a favourable response

Susanna Akiki WMRGL 2009 PML-RARA Monitoring Re emergence is predictive of relapse Early detection allows early effective intervention Failure to achieve remission

Susanna Akiki WMRGL year old female presented with APML in Nov ,XX, +8, t(15;17)(q22;q21) RT-PCR confirmed a PML/RARA (bcr3) gene fusion consistent with the diagnosis of APML, M3. Case history

Susanna Akiki WMRGL 2009 APML Diagnosed Nov2003 Good induction response (4.7 log reduction, lab mean= 2.54) ? Relapse 31 months post consolidation Remained PML-RARA negative

Susanna Akiki WMRGL 2009 Diagnosis of secondary AML rather than relapsed APML considered 46,XX,inv(16)(p13q22)[15] CBFB/MYH11 type D fusion 900bp 203bp

Susanna Akiki WMRGL 2009 Kinetics of emergence cDNA banked as a consequence of APL monitoring Retrospective analysis for CBFB/MYH11 First appearance of inv(16) clone Study kinetics of disease emergence

Susanna Akiki WMRGL 2009 Inv(16) retrospective analysis ? relapse 15 month plateau phaseExponential phase APL diagnosis Inv (16 ) 9 months27 months

Susanna Akiki WMRGL 2009 Gilliland’s 2 hit hypothesis Gilliland & Griffin Blood 2002 these mutations ‘cooperate’: the ‘2-hit’ model of leukaemogenesis

Susanna Akiki WMRGL 2009 Model 1: Inv (16) pre existing clone ? treatment

Susanna Akiki WMRGL 2009 Model 2: True secondary leukaemia? treatment

Susanna Akiki WMRGL 2009 FLAG Patient Outcome ? APL Relapse – As0 2ndry AML diagnosed 100% mets <5% IF 0% IF Flag-Ida

Susanna Akiki WMRGL 2009 Summary Novel opportunity to study the biology of AML It is possible the inv(16) clone was a pre existing clone, present at the time of diagnosis with APL with a second mutation arising following APL therapy Alternatively this case represents a true secondary AML arising as a consequence of APL therapy with both the CBFB-MYH11 and presumed tyrosine kinase hit induced during different treatment cycles Retrospective analysis suggests biphasic kinetics of inv(16) clone supporting Gilliland's 2 hit hypothesis of the pathogenesis of acute leukaemia

Susanna Akiki WMRGL 2009 Acknowledgments Mike Griffiths Val Davison Fiona MacDonald Molecular Oncology Team Joanne Mason Jane Bryon Max Rindl Rachel Doak Sarah Whelton