Contributions
Abstract: LB2605
Type: Oral Presentation
Presentation during EHA23: On Sunday, June 17, 2018 from 12:15 - 12:30
Location: Room A1
Background
Clonal hematopoiesis of indeterminate potential (CHiP) is associated with age and an increased risk of myeloid malignancies and cardiovascular disease. Previous studies have shown that during allogeneic stem cell transplantation (allo-HSCT) pre-existing donor CHiP clones can engraft and clonally evolve within the recipient.
Aims
In this study, we set out to investigate the potential role of CHiP in long-term survivors of allo-HSCT and their respective related donors.
Methods
Based on long-term survival, we recruited recipients (n=45) and their respective donors (n=45) who underwent related allo-HSCT between 1983 and 2006 and collected peripheral blood for DNA extraction. Mutation analysis was performed using targeted next-generation sequencing (NGS) with unique molecular identifiers (UMI) on granulocyte DNA. Mutations were called using VarScan (VAF≥0.01, mean coverage: 6’833). Detected variants were confirmed by ultra-deep amplicon NGS (mean coverage: 55’116). Furthermore, we assessed all variants detected in granulocyte DNA also in FACS-sorted monocytes, B cells, T cells and in myeloid CFUs (>2’000) derived from CD34+ HSPCs isolated from peripheral blood of study subjects. Moreover, telomere length in granulocytes was measured using MM-qPCR.
Results
With a median follow-up time since allo-HSCT of 16 years (11-34 years post allo-HSCT), we found a total of 47 mutations in 27 of a total of 90 (30%) study subjects. 11/45 (24.4%) donors, and 16/45 (35.6%) recipients carried mutations in at least one known driver gene. 13 study subjects carried >1 mutation suggesting presence of clonal evolution or multiple independent subclones, respectively. Mutations in DNMT3A (14 mutations) and TET2 (9 mutations) accounted for 23/47 (48.9%) of all mutations. The remaining mutations affected further commonly mutated genes in CHiP and myeloid malignancies. Variant allele frequency (VAF) did not differ between donors and recipients. However, VAFs were significantly higher for TET2 than for any other mutation. Monocytes had significantly higher VAFs than granulocytes, B and T cells. Furthermore, there was a positive correlation between VAFs in granulocytes and frequency of mutated myeloid CFUs. Moreover, individuals with CHiP were significantly older than those without CHiP. We found significantly higher RDW and significantly lower platelet and lymphocyte counts in individuals with CHiP, irrespective of donor or recipient status. Telomere length was significantly shorter in granulocytes from recipients as compared to donors. Importantly, 5/45 (11.1%) recipients had donor-derived CHiP (13-21 years post allo-HSCT) and VAFs in these study subjects were slightly but significantly higher in recipients as compared to donors. Notably, one case of donor-derived CHiP evolved into MDS.
Conclusion
More data are needed to increase our understanding of CHiP in the context of HSCT. However, in summary, our results from the so far largest long-term follow-up cohort of donors and recipients assessed for CHiP demonstrate that CHiP is a relatively common condition when targeted NGS protocols with high coverage and a threshold for mutation calling of VAF≥0.01 were used. Despite an increase of VAFs in recipients affected by donor-derived CHiP, this clonal expansion in recipients as compared to their donors is relatively modest, and post allo-HSCT HSPC expansion does not seem to strongly select for detected CHiP clones.
Session topic: 23. Stem cell transplantation - Clinical
Keyword(s): Allogeneic hematopoietic stem cell transplant, mutation analysis, Long-term follow-up, Clonality
Abstract: LB2605
Type: Oral Presentation
Presentation during EHA23: On Sunday, June 17, 2018 from 12:15 - 12:30
Location: Room A1
Background
Clonal hematopoiesis of indeterminate potential (CHiP) is associated with age and an increased risk of myeloid malignancies and cardiovascular disease. Previous studies have shown that during allogeneic stem cell transplantation (allo-HSCT) pre-existing donor CHiP clones can engraft and clonally evolve within the recipient.
Aims
In this study, we set out to investigate the potential role of CHiP in long-term survivors of allo-HSCT and their respective related donors.
Methods
Based on long-term survival, we recruited recipients (n=45) and their respective donors (n=45) who underwent related allo-HSCT between 1983 and 2006 and collected peripheral blood for DNA extraction. Mutation analysis was performed using targeted next-generation sequencing (NGS) with unique molecular identifiers (UMI) on granulocyte DNA. Mutations were called using VarScan (VAF≥0.01, mean coverage: 6’833). Detected variants were confirmed by ultra-deep amplicon NGS (mean coverage: 55’116). Furthermore, we assessed all variants detected in granulocyte DNA also in FACS-sorted monocytes, B cells, T cells and in myeloid CFUs (>2’000) derived from CD34+ HSPCs isolated from peripheral blood of study subjects. Moreover, telomere length in granulocytes was measured using MM-qPCR.
Results
With a median follow-up time since allo-HSCT of 16 years (11-34 years post allo-HSCT), we found a total of 47 mutations in 27 of a total of 90 (30%) study subjects. 11/45 (24.4%) donors, and 16/45 (35.6%) recipients carried mutations in at least one known driver gene. 13 study subjects carried >1 mutation suggesting presence of clonal evolution or multiple independent subclones, respectively. Mutations in DNMT3A (14 mutations) and TET2 (9 mutations) accounted for 23/47 (48.9%) of all mutations. The remaining mutations affected further commonly mutated genes in CHiP and myeloid malignancies. Variant allele frequency (VAF) did not differ between donors and recipients. However, VAFs were significantly higher for TET2 than for any other mutation. Monocytes had significantly higher VAFs than granulocytes, B and T cells. Furthermore, there was a positive correlation between VAFs in granulocytes and frequency of mutated myeloid CFUs. Moreover, individuals with CHiP were significantly older than those without CHiP. We found significantly higher RDW and significantly lower platelet and lymphocyte counts in individuals with CHiP, irrespective of donor or recipient status. Telomere length was significantly shorter in granulocytes from recipients as compared to donors. Importantly, 5/45 (11.1%) recipients had donor-derived CHiP (13-21 years post allo-HSCT) and VAFs in these study subjects were slightly but significantly higher in recipients as compared to donors. Notably, one case of donor-derived CHiP evolved into MDS.
Conclusion
More data are needed to increase our understanding of CHiP in the context of HSCT. However, in summary, our results from the so far largest long-term follow-up cohort of donors and recipients assessed for CHiP demonstrate that CHiP is a relatively common condition when targeted NGS protocols with high coverage and a threshold for mutation calling of VAF≥0.01 were used. Despite an increase of VAFs in recipients affected by donor-derived CHiP, this clonal expansion in recipients as compared to their donors is relatively modest, and post allo-HSCT HSPC expansion does not seem to strongly select for detected CHiP clones.
Session topic: 23. Stem cell transplantation - Clinical
Keyword(s): Allogeneic hematopoietic stem cell transplant, mutation analysis, Long-term follow-up, Clonality