Susanna Akiki WMRGL 2009 Acute Promyelocytic Leukemia with t(15;17) (q22;q21) developing...

Susanna Akiki WMRGL 2009

Acute Promyelocytic Leukemia with t(15;17) (q22;q21)

developing inv(16)(p13q22) secondary AML


• 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


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


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


PML-RARA Monitoring

Level of PML/RARA normalised to ABL

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

01/0

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8

Ratioonlog

scale

PML/RARA:ABL

Sensitivity of detection


0.000001

0.00001

0.0001

0.001

0.01

0.1

1

01/0

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PML/RARA:ABL


t(15;17) predicts a favourable response


PML-RARA Monitoring

Re emergence is predictive of relapse


0.000001

0.00001

0.0001

0.001

0.01

0.1

1

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scale

PML/RARA:ABL



0.000001

0.00001

0.0001

0.001

0.01

0.1

1Ratioonlog

scale

PML/RARA:ABL


Early detection allows early

effective intervention

Failure to achieve remission


• 50 year old female presented with APML in Nov 2003

• 47,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


APML Diagnosed Nov2003

Good induction response

(4.7 log reduction, lab mean= 2.54)

? Relapse 31 months post consolidation


0.0000010.000010.00010.0010.010.1

110Ratio

onlog

scale

PML/RARA:ABL

Sensitivity of detectionLevel of PML/RARA normalised to ABL

0.0000010.000010.00010.0010.010.1

110

10/1

1/200

3

10/0

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PML/RARA:ABL


Remained PML-RARA negative


Diagnosis of secondary AML rather than relapsed APML considered

• 46,XX,inv(16)(p13q22)[15]

• CBFB/MYH11 type D fusion

900bp

203bp


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


Inv(16) retrospective analysis

? relapse

Level of CBFB/MYH11 normalised to ABL

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

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CBFB/MYH11:ABL


15 month plateau phase Exponential phase

APL diagnosis Inv (16)

9 months 27 months


Gilliland’s 2 hit hypothesisGilliland & Griffin Blood 2002

these mutations ‘cooperate’: the ‘2-hit’ model of leukaemogenesis


Model 1: Inv (16) pre existing clone ?Level of CBFB/MYH11 normalised to ABL

1E-12

1E-11

1E-10

1E-09

1E-08

1E-07

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

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CBFB/MYH11:ABL


treatment


Model 2: True secondary leukaemia?Level of CBFB/MYH11 normalised to ABL

1E-12

1E-11

1E-10

1E-09

1E-08

1E-07

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

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CBFB/MYH11:ABL


treatment


FLAG

Level of CBFB/MYH11 normalised to ABL

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

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/200

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/200

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/200

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9

Ratioonlog

scale

CBFB/MYH11:ABL


Patient Outcome

? APL Relapse – As0

2ndry AML diagnosed

100% mets <5% IF 0% IF

Flag-Ida


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


Acknowledgments

Mike GriffithsVal Davison

Fiona MacDonald

Molecular Oncology TeamJoanne Mason

Jane BryonMax Rindl

Rachel DoakSarah Whelton

Susanna Akiki WMRGL 2009 Acute Promyelocytic Leukemia with t(15;17) (q22;q21) developing...

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