RESUMO
BMI-1 and EZH2 are polycomb group (PcG) proteins that maintain self-renewal of stem cells, and are overexpressed in leukemia. To investigate the potential of PcG proteins as leukemia-associated antigens, and as targets for graft-versus-leukemia (GVL) effects, we studied cells obtained from 86 patients with chronic myeloid leukemia (CML) and 25 human leukocyte antigen (HLA)-A*0201(+) sibling donors collected before allogeneic stem cell transplantation (SCT). Although BMI-1 overexpression in CD34(+) cells of CML patients treated with pharmacotherapy is associated with poor prognosis, we found, conversely, that in CML patients treated with SCT, a higher expression of BMI-1, and correspondingly a lower expression of its target for repression, CDKN2A, is associated with improved leukemia-free survival. Cytotoxic T-lymphocyte (CTL) responses to the BMI-1 peptide were detected in 5 of 25 (20%) donors, and in 8 of 19 (42%) HLA-A*0201(+) CML patients. BMI-1 generated more total and high-avidity immune responses, and was more immunogenic than EZH2. PcG-specific CTLs had a memory phenotype, were readily expanded in short-term cultures and were detected after SCT in recipients of PcG-specific CTL-positive donors. A higher BMI-1 expression in CML CD34(+) progenitors was associated with native BMI-1 immune responses. These immune responses to PcG proteins may target leukemia stem cells and have relevance for disease control by GVL.
Assuntos
Doença Enxerto-Hospedeiro/prevenção & controle , Leucemia Mielogênica Crônica BCR-ABL Positiva/imunologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/terapia , Proteínas Nucleares/imunologia , Proteínas Nucleares/metabolismo , Proteínas Proto-Oncogênicas/imunologia , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Repressoras/imunologia , Proteínas Repressoras/metabolismo , Transplante de Células-Tronco , Linfócitos T Citotóxicos/imunologia , Antígenos CD34/metabolismo , Estudos de Coortes , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteína Potenciadora do Homólogo 2 de Zeste , Ensaio de Imunoadsorção Enzimática , Antígenos HLA-A , Antígeno HLA-A2 , Humanos , Imunofenotipagem , Leucemia Mielogênica Crônica BCR-ABL Positiva/metabolismo , Proteínas Nucleares/genética , Fragmentos de Peptídeos/imunologia , Fragmentos de Peptídeos/metabolismo , Complexo Repressor Polycomb 1 , Complexo Repressor Polycomb 2 , Proteínas Proto-Oncogênicas/genética , RNA Mensageiro/genética , Proteínas Repressoras/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Taxa de Sobrevida , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transplante Homólogo , Resultado do TratamentoRESUMO
The cure of chronic myeloid leukemia (CML) patients following allogeneic stem cell transplantation (SCT) is attributed to graft-versus-leukemia (GVL) effects targeting alloantigens and/or leukemia-associated antigens (LAA) on leukemia cells. To assess the potential of LAA-peptide vaccines in eliminating leukemia in CML patients, we measured WT1, PR3, ELA2 and PRAME expression in CD34+ progenitor subpopulations in CML patients and compared them with minor histocompatibility antigens (mHAgs) HA1 and SMCY. All CD34+ subpopulations expressed similar levels of mHAgs irrespective of disease phase, suggesting that in the SCT setting, mHAgs are the best target for GVL. Furthermore, WT1 was consistently overexpressed in advanced phase (AdP) CML in all CD34+ subpopulations, and mature progenitors of chronic phase (CP) CML compared to healthy individuals. PRAME overexpression was limited to more mature AdP-CML progenitors only. Conversely, only CP-CML progenitors had PR3 overexpression, suggesting that PR1-peptide vaccines are only appropriate in CP-CML. Surface expression of WT1 protein in the most primitive hematopoietic stem cells in AdP-CML suggest that they could be targets for WT1 peptide-based vaccines, which in combination with PRAME, could additionally improve targeting differentiated progeny, and benefit patients responding suboptimally to tyrosine kinase inhibitors, or enhance GVL effects in SCT patients.
Assuntos
Antígenos de Neoplasias/análise , Células-Tronco Hematopoéticas/imunologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/imunologia , Células-Tronco Neoplásicas/imunologia , Antígenos CD34 , Vacinas Anticâncer/química , Estudos de Casos e Controles , Efeito Enxerto vs Leucemia/imunologia , Humanos , Imunoterapia/métodos , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Antígenos de Histocompatibilidade Menor/análise , Proteínas de Neoplasias/análiseRESUMO
Natural killer (NK) cells are the first lymphocytes to recover after allogeneic stem cell transplantation (SCT) and can exert powerful graft-versus-leukemia (GVL) effects determining transplant outcome. Conditions governing NK cell alloreactivity and the role of NK recovery in sibling SCT are not well defined. NK cells on day 30 post-transplant (NK30) were measured in 54 SCT recipients with leukemia and donor and recipient killer immunoglobulin-like receptor (KIR) genotype determined. In univariate analysis, donor KIR genes 2DL5A, 2DS1, 3DS1 (positive in 46%) and higher numbers of inhibitory donor KIR correlated with higher NK30 counts and were associated with improved transplant outcome. NK30 counts also correlated directly with the transplant CD34 cell dose and inversely with the CD3+ cell dose. In multivariate analysis, the NK30 emerged as the single independent determinant of transplant outcome. Patients with NK30 >150/microl had less relapse (HR 18.3, P=0.039), acute graft-versus-host disease (HR 3.2, P=0.03), non-relapse mortality (HR 10.7, P=0.028) and improved survival (HR 11.4, P=0.03). Results suggest that T cell-depleted SCT might be improved and the GVL effect enhanced by selecting donors with favorable KIR genotype, and by optimizing CD34 and CD3 doses.
