Contributions
Abstract: EP1266
Type: E-Poster Presentation
Session title: Stem cell transplantation - Clinical
Background
Allogeneic hematopoietic stem cell transplantation (HSCT) is an important treatment for the hematological malignancies. Relapse is the leading cause after transplantation. The immunological principle of recurrence is different, but HLA down regulation may be important.
Aims
study the change of HLA expression when relapse post allogeneic hematopoietic stem cell transplantation, and the relationship of HLA down regulation with MRD duration.
Methods
A total of 2581 patients received allogeneic hematopoietic stem cell transplantation(allo-HSCT) in Hebei Yanda Ludopei Hospital from 2018 to 2020, of which 32 patients with recurrent acute leukemia after transplantation were selected for HLA antigen expression analysis. Male: female was 23:9, median age was 17 years old (2-51 years old), including 18 cases of AML, 7 cases of B-ALL, 5 cases of T-ALL and 2 cases of MPAL. Among them, there were 23 cases of haplo-identical transplantation, 5 cases of related matched transplantation and 4 cases of unrelated matched transplantation. Bone marrow samples were taken at the time of initial diagnosis and recurrence, and the expression of HLA-II proteins (HLA-DR and/or HLA-DRDPDQ) in tumor cells were detected by multi-parameter flow cytometry. HLA-I proteins HLA-ABC were detected in 6 cases simultaneously. 52 kinds of common fusion genes and 58 kinds of gene mutation were monitored at the same time for all patients by real-time quantitative polymerase chain reaction (RT-PCR) and next generation sequencing (NGS), as well as chromosome examination. 34% (11/32) of the patients were analyzed for HLA gene sites in the HLA region by NGS or PCR according to the proportion of tumor cells at relapse. Median follow-up were 722 days (0-1950 days), and MRDs were detected using multicolor flow cytometry at regular intervals. SPSS 25 software was used to analyze the changes in HLA antigen expression intensity between initial diagnose and relapse after transplantation, as well as the correlation between HLA expression and persistence of MRD.
Results
Among the 32 patients, the median recurrence time was 239 days (30-1290 days). Compared with the initial diagnose, the HLA-II antigen expression was down-regulated in 43.75% of patients after transplantation (P=0.01), which was consistent with the results of NGS. And the down-regulated degree of HLA-II was positively correlated with the duration of MRD (R2=0.9996). 50% (5/10) of AML involved chromosome 3 at initial diagnose, and such patients were more prone to down-regulation of HLA class II protein expression. 77% of patients with relapse after transplantation were associated with new chromosomal abnormalities, but flow cytometry showed no correlation between down-regulation of HLA-II antigen expression and new chromosomal abnormalities after the relapses, and no significant correlation with gene mutation and fusion genes. Due to the small number of cases, no correlation was found between ALL. Three patients showed HLA-loss, including one case of HLA-I (haplo-allo-HSCT), one case of HLA II (haplo-allo-HSCT), and one case of loss of both HLA II and class I sites (related matched allo-HSCT).
Conclusion
The HLA-II protein expression is prone to be down-regulated in relapsed patients after transplantation, which may be one of the important immunological reasons for the recurrence of hematologic tumors. The down-regulation degree of HLA II protein level is significantly positively correlated with the duration of MRD. Patients with AML that initially involved chromosome 3 were more likely to have down-regulated HLA class II protein expression.
Keyword(s): Flow cytometry, HLA, Relapse, Stem cell transplant
Abstract: EP1266
Type: E-Poster Presentation
Session title: Stem cell transplantation - Clinical
Background
Allogeneic hematopoietic stem cell transplantation (HSCT) is an important treatment for the hematological malignancies. Relapse is the leading cause after transplantation. The immunological principle of recurrence is different, but HLA down regulation may be important.
Aims
study the change of HLA expression when relapse post allogeneic hematopoietic stem cell transplantation, and the relationship of HLA down regulation with MRD duration.
Methods
A total of 2581 patients received allogeneic hematopoietic stem cell transplantation(allo-HSCT) in Hebei Yanda Ludopei Hospital from 2018 to 2020, of which 32 patients with recurrent acute leukemia after transplantation were selected for HLA antigen expression analysis. Male: female was 23:9, median age was 17 years old (2-51 years old), including 18 cases of AML, 7 cases of B-ALL, 5 cases of T-ALL and 2 cases of MPAL. Among them, there were 23 cases of haplo-identical transplantation, 5 cases of related matched transplantation and 4 cases of unrelated matched transplantation. Bone marrow samples were taken at the time of initial diagnosis and recurrence, and the expression of HLA-II proteins (HLA-DR and/or HLA-DRDPDQ) in tumor cells were detected by multi-parameter flow cytometry. HLA-I proteins HLA-ABC were detected in 6 cases simultaneously. 52 kinds of common fusion genes and 58 kinds of gene mutation were monitored at the same time for all patients by real-time quantitative polymerase chain reaction (RT-PCR) and next generation sequencing (NGS), as well as chromosome examination. 34% (11/32) of the patients were analyzed for HLA gene sites in the HLA region by NGS or PCR according to the proportion of tumor cells at relapse. Median follow-up were 722 days (0-1950 days), and MRDs were detected using multicolor flow cytometry at regular intervals. SPSS 25 software was used to analyze the changes in HLA antigen expression intensity between initial diagnose and relapse after transplantation, as well as the correlation between HLA expression and persistence of MRD.
Results
Among the 32 patients, the median recurrence time was 239 days (30-1290 days). Compared with the initial diagnose, the HLA-II antigen expression was down-regulated in 43.75% of patients after transplantation (P=0.01), which was consistent with the results of NGS. And the down-regulated degree of HLA-II was positively correlated with the duration of MRD (R2=0.9996). 50% (5/10) of AML involved chromosome 3 at initial diagnose, and such patients were more prone to down-regulation of HLA class II protein expression. 77% of patients with relapse after transplantation were associated with new chromosomal abnormalities, but flow cytometry showed no correlation between down-regulation of HLA-II antigen expression and new chromosomal abnormalities after the relapses, and no significant correlation with gene mutation and fusion genes. Due to the small number of cases, no correlation was found between ALL. Three patients showed HLA-loss, including one case of HLA-I (haplo-allo-HSCT), one case of HLA II (haplo-allo-HSCT), and one case of loss of both HLA II and class I sites (related matched allo-HSCT).
Conclusion
The HLA-II protein expression is prone to be down-regulated in relapsed patients after transplantation, which may be one of the important immunological reasons for the recurrence of hematologic tumors. The down-regulation degree of HLA II protein level is significantly positively correlated with the duration of MRD. Patients with AML that initially involved chromosome 3 were more likely to have down-regulated HLA class II protein expression.
Keyword(s): Flow cytometry, HLA, Relapse, Stem cell transplant