Lenalidomide targets clonogenic side population in multiple myeloma: pathophysiologic and clinical implications

Area of Science:

• Hematology
• Cancer Biology
• Stem Cell Biology

Background:

• Multiple myeloma (MM) recurrence post-therapy suggests the presence of tumor-initiating stem-like cells.
• Identifying and targeting these subpopulations is crucial for improving treatment outcomes.

Purpose of the Study:

• To investigate the existence and characteristics of stem-like side population (SP) cells in multiple myeloma.
• To evaluate the effect of lenalidomide and bone marrow stromal cells (BMSCs) on MM SP cells.

Main Methods:

• Flow cytometry using Hoechst 33342 staining to identify and isolate SP cells.
• Analysis of SP cell characteristics, including proliferation, clonogenicity, and gene expression (ABCG2).
• Assessment of lenalidomide and BMSC interactions with SP cells, including phosphorylation changes.

Main Results:

• MM SP cells exhibit stem-like features, including higher proliferation, clonogenicity, and tumorigenicity.
• SP cells express CD138 and have higher ABCG2 transporter activity.
• Lenalidomide reduced SP cell percentage and clonogenicity, altering key signaling pathways.
• BMSCs enhanced SP cell viability and proliferation, an effect abrogated by lenalidomide and thalidomide.

Conclusions:

• Multiple myeloma contains stem-like SP cells contributing to therapeutic resistance and recurrence.
• Lenalidomide demonstrates a novel mechanism by targeting the SP cell fraction.
• These findings support developing new therapeutic strategies focused on eliminating MM stem-like cells.