Clonality in context: hematopoietic clones in their marrow environment

Area of Science:

• Hematology
• Genetics
• Oncology
• Evolutionary Biology

Background:

• Clonal hematopoiesis, the expansion of hematopoietic stem cells with specific mutations, is observed with aging and in various diseases, including myeloid cancers and bone marrow failure.
• The significance of somatic mutations in clonal hematopoiesis, particularly their role in leukemogenesis in seemingly healthy individuals or post-recovery from aplastic anemia, remains uncertain.
• Current understanding often focuses on deterministic processes, potentially overlooking the influence of environmental factors on clonal development.

Purpose of the Study:

• To re-evaluate the understanding of clonal evolution in hematopoiesis, emphasizing the principles of natural selection.
• To highlight the critical role of the bone marrow microenvironment and the broader organismal context in shaping clonal hematopoiesis.
• To provide a framework for interpreting genomic findings in the context of clonal selection and evolution.

Main Methods:

• Conceptual review and synthesis of existing knowledge on clonal hematopoiesis, somatic mutations, and leukemogenesis.
• Analysis of clonal hematopoiesis in specific models: aging, bone marrow failure, and post-chemotherapy states.
• Emphasis on evolutionary principles, particularly natural selection, to explain clonal dynamics.

Main Results:

• Clonal hematopoiesis is a natural phenomenon, particularly prevalent in aging individuals and in disease states.
• The development and behavior of hematopoietic clones are significantly influenced by selective pressures within the bone marrow and the organism.
• Recurrent somatic mutations in specific genes are hallmarks of malignant clones but their direct link to leukemogenesis requires careful consideration of evolutionary context.

Conclusions:

• A paradigm shift towards understanding clonal hematopoiesis through the lens of natural selection is necessary.
• The bone marrow microenvironment and organismal factors are key selective forces driving clonal evolution.
• Caution is advised against over-interpreting genomic test results without a comprehensive understanding of clonal selection and evolutionary dynamics.