Molecular Markers in Acute Leukemia Dr Muhd Zanapiah Zakaria Hospital Ampang
Molecular Markers Useful at diagnosis Classify groups and prognosis Development of more specific therapies Application of risk-adjusted therapeutic approaches Monitoring responses Minimal Residual Disease Surveillance for relapse
AML Classification FAB Classification 2008 WHO Classification M0 M1 M2 M3 M4 M5 M6 M7 Minimally differentiated Without maturation With maturation Acute promyelocytic leukemia Acute myelomonocytic leukemia Acute monoblastic leukemia Acute erythroleukemia Acute megakaryoblastic leukemia
Cytogenetic Abnormalities Swerdlow et al. 2008 Prognostic Subgroup Cytogenetic Abnormality Favorable - t(15;17)/pml-rara - t(8;21) - inv(16)/t(16;16) Intermediat e - Normal karyotype - t(9;11) - Gains of whole chromosomes or loss of Y chromosome Unfavorable - t(6;9) - inv(3)/t(3;3) - Complex karyotype
Molecular markers in AML
Molecular markers in AML
Molecular Markers in AML
Prognostic Significance of Molecular Markers Favorable mutations Unfavorable mutations Unfavorable overexpression of single genes Established Likely Potential NPM1 CEBPA FLT3-ITD KIT FLT3-TKD MLL-PTD WT1 IDH BAALC ERG MN1 EVI1 HOXA9 MEIS1
Core Binding Factors (CBF) CBF complex : heterodimer composed of RUNX1( also called AML1) and CBFβ Essential role in haemotopoiesis 3 common translocations t(8;21)/runx1-runx1t1, t(3;21)/runx1-evi1 and inv(16) or t(16;16)
AML1 (RUNX1) rearrangements Expressed in all haematopoietic lineages Regulates expression of several genes spefically linked to haematopoiesis Chimeric protein AML1-ETO (RUNX1-RUNX1T1) result from t(8;21) Most achieve CR and benefits from postremission therapy high dose Cytarabine Frequent a/w c-kit mutations-adverse outcome Favourable outcome & target for MRD detection
CBFβ-MYH11 Inv(16)(p13;q32) or t(16;16)(p13;q32)- common detected in AML qrt-pcr allows monitoring CR 10 different CBFβ-MYH11 transcripts have been reported Favourable prognosis Frequently a/w c-kit and FLT3 mutations- worse prognosiis
c-kit KIT: proto oncogene located on chromosome band 4q11-12 Confer unfavourable prognosis with higher relapse risk Encodes a transmembrane glycoprotein member of type III receptor tyrosine kinase family c-kit mutations have been found variable but frequent in patients with CBF AML
KIT Mutations in CBF AMLs 10-20% of the CBF AMLs have KIT mutations While the cytogenetic abnormalities that define CBF AMLs normally confer a good prognosis, those with KIT mutations do poorly inv(16) t(8;21) Paschka et al., J Clin Oncol, 2006
CEBPA Mutations CCAAT/enhancer binding alpha protein Transcription factor whose function is crucial for the development and differentiation of granulocytes from hematopoietic precursors Mutations lead to a loss of function, and thought to promote leukemogenesis by blocking granulocyte differentiation 15% of CN-AML have CEBPA mutations Variety of mutations occur throughout the coding region, but fall into two major types: N-terminal frameshift truncation of protein C-terminal in-frame impaired dimerization and DNA binding Identification of mutations requires DNA sequencing Majority of mutations are biallelic, compound heterozygous mutations
CEBPA Mutations Only double mutations are associated with a favorable outcome A series of cases with silencing of CEBPA have been identified, and associated with a distinctly poor prognosis Standard induction chemo followed by 3-4 cycles of high-dose cytarabine is the recommended therapy Patients may not be considered candidates for allogeneic HSCT in first complete remission
FLT3 Mutations Member of the the class III receptor tyrosine kinase family Important role in proliferation, survival, and differentiation of hematopoietic progenitor cells Mutations result in constitutive activation of FLT3 30% of CN-AML have mutations in FLT3 ITDs result from duplication and tandem insertion of small, variably sized (3-400 nt) gene fragments TKDs are point mutations, small insertions, or deletions that occur in activation loop in the carboxyterminal lobe, mainly at codons 835 and 836 Identification of the ITD mutation involves a PCR-based assay that can detect the larger PCR products indicative of duplication
FLT3 Mutations Prognosis of CN-AML with FLT3- ITD is significantly inferior compared with FLT3-ITD negative CN-AML Prognostic relevance of FLT3-TKD is not as well-established, but also appears to be unfavorable Therapeutically, there is accumulating evidence that allogeneic HSCT is an attractive option, given the poor outcome with standard chemotherapy Randomized phase III trials evaluating FLT3 inhibitors are underway
NPM1 Mutations Multifunctional phosphoprotein that travels between nuclear compartments and the cytoplasm Normally, predominantly located in the nucleolus Implicated in ribosome assembly and regulation of ARF and p53 tumor suppressor function Mutations were first discovered by IHC because of cytoplasmic mislocation of the mutated NPM1 protein 50-60% of CN-AML show NPM1 mutations Detection of the mutations involves a PCR-based assay >40 mutations have been identified within exon 12 of the gene, but virtually all lead to a net insertion of 4 nt
NPM1 Mutations Prognostic implications due to NPM1 mutations must be made in the context of FLT3 mutations Only NPM1 mut /FLT3-ITD neg are associated with achievement of complete remission and favorable outcome Potential marker for disease monitoring Standard induction chemo followed by 3-4 cycles of highdose cytarabine is the recommended therapy Patients may not be considered candidates for allogeneic HSCT in first complete remission May become important marker for disease monitoring
PML-RARα AML-M3 : characterized by t(15;17) Involves retionic acid receptor gene on chromosome 17 and PML gene on chromosome 15 Results in PML-RARαgene, detected by RT-PCR Provides rapid diagnosis MRD monitoring
More molecular markers under investigation Unfavorable recurrent genetic abnormalities IDH1, IDH2 WT1 MLL-PTD NRAS KRAS TP53 Unfavorable overexpression of single genes BAALC ERG EVI1 MN1 TET2 ASXL2 RUNX1 DNMT3A
Acute lymphoblastic Leukemia mainly a disease of childhood arises from recurrent genetic insults that block precursor B and T cell differentiation drive aberrant cell proliferation and survival
B-ALL
BCR-ABL Ph Chromosome resulting from t(9;22)(q34;q11) BCR-ABL fusion protein: main 2 distinct molecular weight : p210 and p190 Targeted therapy : TKIimatinib, dasatinib plus chemotherapy Monitor MRD Adult Ph+ B ALL: 33% p210, 66% p190 Childhood Ph+ b ALL: 90% p190
T-ALL
Summary Acute leukemia is heterogeneous group Molecular markers : useful in diagnosis, classify in groups, prognosis, targeted therapy, riskadapted strategy and monitoring
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