2.
FLT- 3 Gene
fms related tyrosine
kinase 3
encodes a class III
receptor tyrosine kinase
that regulates
hematopoiesis.
3. Binding of the fms-related tyrosine kinase 3 ligand to the
extracellular domain
Induces homo-dimer formation in the plasma membrane
Auto-phosphorylation of the receptor
activated receptor kinase subsequently phosphorylates and
activates multiple cytoplasmic effector molecules
Apoptosis, Proliferation, and
Differentiation of hematopoietic cells in
bone marrow
4. Mutations that result in the constitutive activation of
this receptor result in acute myeloid leukemia and acute
lymphoblastic leukemia
6.
ITD Mutation
FLT3/ITD mutations
are in-frame
duplications that
invariably involve the
juxtamembrane
domain, a domain that
exerts a negative
regulatory function
over the kinase activity.
7.
8.
Prognostic significance
FLT3/ITD mutation is a poor prognostic factor,
which occurs frequently in AML, and is associated
with higher incidence of early disease relapse and
shorter overall survival.
9.
FLT3 ITD allelic ratio
Ratio of mutant and
wild type alleles of
FLT3
If ratio is <0.5 , outcome
will be favorable as
compared to others
having ratio more then
that.
10.
FLT3 Inhibitors
Compete with ATP for binding to the active pocket of the
kinases
Inability to auto-phosphorylate or phosphorylate substrate
proteins
Signal transduction initiated by the mutated RTK is interrupted
11. Relapsed samples and samples with a high mutant-to-wild type allelic ratio
were invariably more responsive to cytotoxicity from FLT3 inhibition
compared with the samples obtained at diagnosis or those with a low mutant
allelic ratio.
Drugs used are :
Quizartinib (AC220)
Sorafenib ,
Sunitinib
Lestaurtinib and
Midostaurin
12.
Methodology
DNA was extracted from EDTA peripheral blood sample
Polymerase chain reaction (PCR) was carried out using a set of primers
flanking 14 and 15 of the FLT3 gene
Capillary electrophoresis of the PCR product carried out in 3500 DX
automated genetic analyzer using LIZ600 size standard
FLT3-ITD allelic ratio was calculated as the ratio of the peak height of the
mutant product to the peak height of the wild-type product
13.
FLT3 wild type allele was detected at a computed
molecular size of 326 bp and with a peak height of
122364 RFU.
Along with this, two distinct FLT3 ITD molecular
variants, coded V1 and V2 were detected with a
molecular signature of 376 and 394 bp respectively
and with a peak height of 36037 and 36708 RFU
respectively.
Result
14. Allele type RFU Bp
FLT3 WILD TYPE 122364 326
FLT3 ITD (V1) 36037 376
FLT3 ITD (V2) 36708 394
The clonal variants carried a "mutant to wild type" allelic ratio value
of 0.295 & 0.299 for V1 and V2 respectively indicating favorable
prognosis as compared to have more then 0.5 allelic ratio .
15.
We hypothesize that successful treatment will
eventually eliminate either or both of the mutant
variants and conversely a resistant one will enrich
any one of them leading to identification of a
potential marker linked to therapeutic resistance.
Discussion
