Download Loss of Mismatched HLA in Leukemia after Stem

Loss of Mismatched HLA in Leukemia
after Stem-Cell Transplantation
N Engl J Med 2009;361:478-88
R2 Jung Kook Wi / prof. Kyung Sam Cho
Background
Transplantation of hematopoietic stem cells
– from a haploidentical family donor
– Curative option for patients with high-risk hematologic cancers
The major limitation of this strategy
– the risk of severe GVHD
– alloreactions mediated by donor T cells
– against the recipient’s unshared HLA haplotype
The feasibility & efficacy of infusions of
haploidentical donor T cells
Background
The infusion of donor T cells
Rapid reconstitution of the immune system
The graft-versus-leukemia
Relapse still ??? Mechanism ???
Genomic loss
Of the recipient’s mismatched HLA haplotype
Mechanism of tumor escape from the selective pressure
of a patient-specific graft-versus-leukemia reaction
Methods
Patients
Retrospectively
– Hematologic cancers
– One or more haploidentical hematopoietic stem-cell transplantations
– At the San Raffaele Hospital in Milan ( 2002 - 2007 )
All (43 patient) : high-risk hematologic myeloid cancers
– 36 with AML & 7 with high-risk MDS
– 26 with transplantation & 17 more than one
Methods
Chimerism Analyses
Monthly in samples of bone marrow aspirate
– short-tandem-repeat amplification (STR)
– genomic HLA typing
Loss of Heterozygosity
– The use of polymerase-chainreaction amplification of 12 highly
polymorphic short-tandem-repeat markers spanning the entire length
of chromosome 6
– The Illumina Human CNV370-Quad Bead Array
– The Affymetrix Human SNP Array 6.0 single-nucleotidepolymorphism (SNP) array
Methods
In Vitro Evaluation of Graft-versus-Leukemia Effect
Separated peripheral-blood mononuclear cells
– from the stem-cell donor for Patient 16
– from Patient 16
• 85 days after the first hematopoietic stem-cell transplantation
• 96 days after the second transplantation
– from a healthy HLA-mismatched subject
Cells plated with irradiated mononuclear cells
The function of responder cells from the mixed lymphocyte culture
– tested after each stimulation
– the use of 51Cr-release, enzyme-linked immunospot (ELISpot)
– [3H] thymidine-incorporation assays
Results
Clinical Observations
Studies of donor–host hematopoietic chimerism
– carried out monthly after transplantation in all 43 patients
– short-tandem-repeat amplification and HLA typing
– looking for a reappearance of the host hematopoiesis in the BM
– often predicts relapse
In all 17 patients, relapse was confirmed
– host origin on the basis of short-tandem-repeat chimerism
Surprisingly, in five of these patients,
genomic HLA typing of BM cells did not detect host-specific HLA alleles.
Figure 1
Identification of Mutant Variants of Leukemic Cells Not Detected by Chimerism
Analysis with HLA Typing.
Figure 2. Genomic Loss of the Patient-Specific HLA Haplotype
by Leukemic Cells after Transplantation in Patient 16.
Figure 3 . Loss of the Patient-Specific HLA Haplotype through Extensive Rearrangements
in Chromosome 6, Leading to Acquired Uniparental Disomy.
Figure 3 . Loss of the Patient-Specific HLA Haplotype through Extensive Rearrangements
in Chromosome 6, Leading to Acquired Uniparental Disomy.
Functional Study of the Graft-versusLeukemia Response
Conclusions
After transplantation of haploidentical hematopoietic stem cells
and infusion of donor T cells,
leukemic cells can escape from the donor’s anti - leukemic T cells
through
the loss of the mismatched HLA haplotype.
This event leads to relapse.