Acute lymphoblastic leukemia (ALL) is characterized by the presence of chromosomal changes, including numerical changes, translocations and deletions, which are often associated with additional single nucleotide mutations. In this study we used single-cell targeted DNA sequencing to determine the clonal heterogeneity of B-cell ALL at diagnosis and during chemotherapy treatment. With a customly designed DNA amplicon library targeting the most common mutations (in 110 genes) present in ALL, we analyzed bone marrow samples and/or blood samples from 12 B-ALL cases at diagnosis. For 4 cases where we detected multiple mutational clones at diagnosis, we also studied blood samples during the first weeks of chemotherapy treatment. This study shows that B-ALL cases with either a ETV6-RUNX1 or a BCR-ABL1 fusion have a low mutational burden, while cases with PAX5 alterations or hyperdyploidy have multiple clones at diagnosis, often with mutations in the JAK-STAT signaling pathway and the RAS signaling pathway. As expected, it can be observed that these clones disappear during treatment of the ... (Show More)

Acute lymphoblastic leukemia (ALL) is characterized by the presence of chromosomal changes, including numerical changes, translocations and deletions, which are often associated with additional single nucleotide mutations. In this study we used single-cell targeted DNA sequencing to determine the clonal heterogeneity of B-cell ALL at diagnosis and during chemotherapy treatment. With a customly designed DNA amplicon library targeting the most common mutations (in 110 genes) present in ALL, we analyzed bone marrow samples and/or blood samples from 12 B-ALL cases at diagnosis. For 4 cases where we detected multiple mutational clones at diagnosis, we also studied blood samples during the first weeks of chemotherapy treatment. This study shows that B-ALL cases with either a ETV6-RUNX1 or a BCR-ABL1 fusion have a low mutational burden, while cases with PAX5 alterations or hyperdyploidy have multiple clones at diagnosis, often with mutations in the JAK-STAT signaling pathway and the RAS signaling pathway. As expected, it can be observed that these clones disappear during treatment of the leukemia with almost no mutated cells left after two weeks of treatment.

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