Endothelial progenitor cells display clonal restriction in multiple myeloma

Area of Science:

• Hematology
• Oncology
• Vascular Biology

Background:

• Multiple myeloma (MM) is characterized by increased neoangiogenesis, crucial for tumor growth and progression.
• Elevated endothelial progenitor cells (EPCs) contribute to MM neoangiogenesis and correlate with disease activity.
• The origin and function of increased EPCs in MM remain incompletely understood.

Purpose of the Study:

• To investigate the clonality of EPCs in multiple myeloma patients.
• To determine if EPCs in MM are genetically linked to the neoplastic clone.
• To elucidate the role of clonal EPCs in MM-associated neoangiogenesis.

Main Methods:

• X-chromosome inactivation (XCI) patterns were analyzed in EPCs and hair root cells using the human androgen receptor assay (HUMARA) in female MM patients.
• Immunoglobulin heavy-chain (IGH) gene rearrangement was assessed in EPCs and bone marrow cells via PCR.
• Patients studied were treatment-naive MM patients.

Main Results:

• Significant XCI skewing, indicative of clonality, was observed in 64% of EPC samples analyzed by HUMARA.
• Extreme XCI skewing was noted in 4 patients, contrasting with random XCI in hair root cells.
• IGH gene rearrangement, shared with bone marrow cells, was detected in EPCs of 71% of tested patients, suggesting a clonal relationship.

Conclusions:

• EPCs in a substantial subpopulation of multiple myeloma patients are related to the neoplastic clone.
• This clonal relationship of EPCs represents a key mechanism for enhanced tumor neovascularization in MM.
• Findings suggest therapeutic strategies targeting clonal EPCs could impact MM progression.