Project description:<p>Acute myeloid leukemia is an aggressive clonal malignancy of the bone marrow that is the direct result of sequential acquisition of mutations in a single lineage of cells. In this study, we investigate a model in which this mutational acquisition occurs serially in long-lived self-renewing hematopoietic stem cells eventually resulting in frank acute myeloid leukemia. Coding mutations in multiple AML patients were identified using exome sequencing followed by sanger sequencing validation. The level of these mutations was then assessed in residual hematopoietic stem cells from each patient using targeted deep sequencing. These population-level estimates of mutant allele burden were then validated in single cell assays targeted to the identified mutations. This allowed for determination of the order of acquisition of the mutations that preceded the development of the leukemia. The results of this study identify pre-leukemic hematopoietic stem cell clones that could contribute to patient relapse and outcome.</p>
Project description:The tracking of leukemic clones in acute myeloid leukemic promisses deeper insights into disease development and therapeutic options. We therefore established a fluorescent genetic barcoding (FGB) labeling approach that allows for flow cytomtric tracking of color-coded clones in vitro and in vivo. In Hoxa9 and Meis1 (H9M) dependent murine AML, we tracked the growth behavior of 24 clones in parallel and enriched for pre-leukemic clones as well as their de novo expanded counterparts and stably expanded clones from leukemic mice by fluorescence-activated cell sorting. These samples were subjected toRNA sequencing for the assessment of transcriptional changes underlying clonal maintenance and expansion.
Project description:Germline RUNX1 mutations are found in familial platelet disorders with predisposition to acute myelogenous leukemia (FPD/AML). This very rare disease is characterized by thrombocytopenia, platelet dysfunction and a 35% lifetime risk of developing MDS/AML and in rare cases also T-ALL. Here, we focus on a case of a man with a familial history of RUNX1 R174Q mutation who developed at the age of 42 years an EGIL T2-ALL and, two years after remission, an AML-M0. To investigate whether initial and relapsed leukemic blasts originated from the same clone, we performed CGH array and WES on both blasts populations. In both T2-ALL and AML-M0 samples, CGH array revealed loss of 1p36.32-23 and 17q11.2 and nine other small deletions. Both AML-M0 and T2-ALL blasts demonstrated clonal rearrangements of both TCRγ (Vγ9-Jγ1-1) and TCRδ (Dδ2-Jδ1 and Dδ2-Jδ3). 18 genes were found by WES to be mutated in both blasts at a frequency of more than 40%. Additional variants were identified only in T2-ALL or in AML-M0 evoking the existence of a common original clone, which gave rise to subclonal populations. MiSeq technology performed on peripheral blood-derived CD34+ cells five years prior T2-ALL development revealed only missense TET2 P1962T mutation at a frequency of 1% (which reaches a frequency of 50 % in fully transformed leukemic clone) suggesting that this mutation in association with germline RUNX1 R174Q mutation led to amplification of a hematopoietic clone susceptible to acquire other transforming alterations. Identification of clonal hematopoiesis with acquired mutations at low frequency in hematopoietic progenitors before leukemia development could clearly serve as a marker of pre-leukemic state and be helpful in patient care.
Project description:Germline RUNX1 mutations are found in familial platelet disorders with predisposition to acute myelogenous leukemia (FPD/AML). This very rare disease is characterized by thrombocytopenia, platelet dysfunction and a 35% lifetime risk of developing MDS/AML and in rare cases also T-ALL. Here, we focus on a case of a man with a familial history of RUNX1 R174Q mutation who developed at the age of 42 years an EGIL T2-ALL and two years after remission an AML-M0. To investigate whether initial and relapsed leukemic blasts originated from the same clone, we performed CGH array and WES on both blasts populations. In both T2-ALL and AML-M0 samples, CGH array revealed loss of 1p36.32-23 and 17q11.2 and nine other small deletions. Both AML-M0 and T2-ALL demonstrated clonal rearrangements of both TCR (V9-J1-1) and TCR (D2-J1 and D2-J3). 18 genes were found by WES to be mutated in the original clone at a frequency of more than 40%. Additional variants were identified only in T2-ALL or in AML-M0 evoking the existence of a common original clone. MiSeq technology performed on peripheral blood-derived CD34+ cells five years prior T2-ALL development revealed only missense TET2 P1962T mutation at a frequency of 1% suggesting that this mutation in association with germline RUNX1 R174Q mutation led to amplification of a hematopoietic clone susceptible to acquire other transforming alterations. Identification of clonal hematopoiesis with acquired mutations at low frequency in hematopoietic progenitors before leukemia development could clearly serve as a marker of pre-leukemic state and might be helpful in patient care.
Project description:Leukemogenesis is a stepwise progression from mutated, pre-neoplastic hematopoietic stem cells (HSCs) to full-blown leukemia. Our ability to prevent or treat de novo and secondary acute myeloid leukemia (AML) is limited by our incomplete understanding of the epigenetic disruption that is central to this process, including improper histone methylation. We performed a comprehensive analysis of 16 histone H3 genes in 434 primary acute myeloid leukemia (AML) samples and identified mutations in adult and pediatric cases (1.6%), with a higher incidence in secondary AML (s-AML) (9%). These included four novel amino acid substitutions (Q69H, A26P, R2Q and R8H) as well as K27M and K27I in H3.1 and H3.3 genes. These mutations are important early events in leukemogenesis as they were observed in pre-leukemic HSCs in two cases and were in the major clones in every sample. Consistent with a role in pre-leukemic HSC clonal expansion, the mutant histones increased functional human HSC frequency and altered differentiation along the erythroid and myeloid lineages, with activity dependent on the specific mutation (K27M, K27I and Q69H). In established human leukemia, the K27M/I mutant histones amplified leukemic aggressiveness, with increased proliferation, expansion of leukemic progenitor and blast cells, and superior competitiveness in vivo. This was associated with increased expression in genes involved in erythrocyte and myeloid differentiation, correlated with a corresponding decrease in histone H3 K27 tri-methylation and increase in K27 acetylation. While histone mutations can co-occur with alterations in RUNX1, we observed that the functional impact of histone mutations is independent of RUNX1 mutations. Taken together, these data establish the involvement of H3 mutations as early drivers of pre-leukemic HSC expansion and leukemogenesis.
Project description:YTHDF2 is overexpressed in a broad spectrum of human acute myeloid leukemias (AML). To study the role of YTHDF2 in leukemia, c-Kit+ cells from foetal livers of Ythdf2fl/fl;Vav-iCre (Ythdf2CKO) and Ythdf2fl/fl (Ythdf2CTL) 14.5 dpc embryos were transduced with Meis1 and Hoxa9 oncogenes and serially re-plated to generate pre-leukemic cells. Total RNA from Ythdf2CKO (n=5) and Ythdf2CTL (n=5) pre-leukemic cells were used for Affymetrix global gene expression analysis.
Project description:YTHDF2 is overexpressed in a broad spectrum of human acute myeloid leukemias (AML). To study the role of YTHDF2 on translation regulation in leukemia, c-Kit+ cells from foetal livers of Ythdf2fl/fl; Vav-iCre (Ythdf2CKO) and Ythdf2fl/fl (Ythdf2CTL) 14.5 dpc embryos were transduced with Meis1 and Hoxa9 oncogenes and serially re-plated to generate pre-leukemic cells. RIBO-seq libraries were then prepared from Ythdf2CKO (n=3) and Ythdf2CTL (n=3) pre-leukemic cells.
Project description:Understanding the contribution of abnormal genetic and epigenetic programs to acute myeloid leukemia (AML) is necessary for the integrated design of targeted therapies. To investigate this, we determined the effect of epigenetic reprogramming on leukemic behavior by generating induced pluripotent stem cells (iPSCs) from AML patient samples harboring MLL rearrangements. AML-derived iPSCs (AML-iPSCs) retained leukemic mutations, but reset leukemic DNA methylation/gene expression patterns and lacked leukemic potential. However, when differentiated into hematopoietic cells, AML-iPSCs reacquired the ability to give rise to leukemia in vivo and reestablished leukemic methylation/gene expression patterns, including an aberrant MLL signature, indicating that epigenetic reprogramming was insufficient to eliminate leukemic behavior. In one case, we identified distinct AML-iPSC KRAS mutant and wildtype subclones that demonstrated differential growth properties and therapeutic susceptibilities, predicting KRAS wildtype clonal relapse due to increased cytarabine resistance. Increased cytarabine resistance was further observed in a cohort of KRAS wildtype MLL-rearranged AML samples, demonstrating the utility of AML-iPSCs in predicting subclonal relapse and facilitating clonal targeting in AML. This SuperSeries is composed of the SubSeries listed below.
Project description:Understanding the contribution of abnormal genetic and epigenetic programs to acute myeloid leukemia (AML) is necessary for the integrated design of targeted therapies. To investigate this, we determined the effect of epigenetic reprogramming on leukemic behavior by generating induced pluripotent stem cells (iPSCs) from AML patient samples harboring MLL rearrangements. AML-derived iPSCs (AML-iPSCs) retained leukemic mutations, but reset leukemic DNA methylation/gene expression patterns and lacked leukemic potential. However, when differentiated into hematopoietic cells, AML-iPSCs reacquired the ability to give rise to leukemia in vivo and reestablished leukemic methylation/gene expression patterns, including an aberrant MLL signature, indicating that epigenetic reprogramming was insufficient to eliminate leukemic behavior. In one case, we identified distinct AML-iPSC KRAS mutant and wildtype subclones that demonstrated differential growth properties and therapeutic susceptibilities, predicting KRAS wildtype clonal relapse due to increased cytarabine resistance. Increased cytarabine resistance was further observed in a cohort of KRAS wildtype MLL-rearranged AML samples, demonstrating the utility of AML-iPSCs in predicting subclonal relapse and facilitating clonal targeting in AML.