Clonal hematopoiesis in hematological disorders: Three different scenarios

Area of Science:

• Hematology
• Oncology
• Genetics

Background:

• Clonality studies determine the single-cell origin of tumors, distinguishing malignant/premalignant from reactive polyclonal processes.
• Detection methods include lineage-specific sequences or disease-specific somatic mutations.
• Historically, clonal hematopoiesis was defined by X-chromosome inactivation patterns in circulating cells.

Purpose of the Study:

• To differentiate clonal malignant and premalignant processes from reactive polyclonal processes using clonality studies.
• To understand the characteristics and implications of clonal hematopoiesis, including myeloproliferative neoplasms (MPNs), chronic lymphocytic leukemia (CLL), and clonal hematopoiesis of undetermined potential (CHIP).

Main Methods:

• Analysis of cell lineage-specific sequences.
• Identification of disease-specific somatic mutations.
• Application of X-chromosome inactivation principles.
• Whole-genome sequencing for CHIP detection in healthy individuals.

Main Results:

• In MPNs, nearly all circulating blood cells originate from a single mutated stem cell, coexisting with polyclonal T lymphocytes.
• CLL originates in a B cell, with normal T and B cells diluted by the expanded CLL clone.
• CHIP involves specific somatic mutations in a small proportion of leukocytes in healthy individuals, without obvious normal stem cell suppression.

Conclusions:

• Clonality studies are crucial for diagnosing hematological malignancies and understanding their origins.
• Further research is needed to define CHIP clones, their persistence, and their transformation potential into hematological malignancies.