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MPC-1-CD49e- immature myeloma cells include CD45+ subpopulations that can proliferate in response to IL-6 in human
R Fujii1, H Ishikawa, M S Mahmoud
1Department of Immunohaematology, Yamaguchi University School of Medicine, Ube, Japan.
Abstract:
Using three-colour phenotypic analysis, we detected five subpopulations of myeloma cells (CD38++) in the bone marrow mononuclear cells of human myeloma patients: MPC-1-CD45-CD49e-, MPC-1-CD45+CD49e-, MPC-1+CD45-CD49e-, MPC-1+CD45+CD49e- and MPC-1+CD45+CD49e+. Most of the myeloma cells did not express CD45 but a few MPC-1- immature myeloma cells and some MPC-1+ myeloma cells expressed CD45 and CD45RO but not CD45RA, whereas all of normal early plasma cells in the peripheral blood, lymph node plasma cells and bone marrow plasma cells expressed CD45 and CD45RA, CD45RB but not CD45RO. In order to clarify the biological character of these myeloma subpopulations, we examined the expression of Ki-67 antigen. Proliferating myeloma cells (Ki-67+) were found in the MPC-1- fractions and the MPC-1-CD45+ fractions rather than MPC-1-CD45- fractions. Next, in order to further clarify the biological difference of two immature subpopulations (MPC-1-CD45-CD49e- and MPC-1- CD45+CD49e-), determined cell viability and phenotypic change after culturing with interleukin 6 (IL-6) in vitro. In the presence of IL-6, MPC-1-CD45+ cells kept their viability more than MPC-1-CD45- cells and some MPC-1-CD45- cells could be converted to MPC-1-CD45+ cells. In conclusion, these data suggest that human myeloma cells are phenotypically subdivided into five subpopulations, and among these subpopulations MPC-1-CD45+CD49e- but not MPC-1-CD45-CD49e- immature cells contain proliferating cells in response to IL-6, and IL-6 can also induce expression of CD45 on MPC-1-CD45- subpopulation of immature myeloma cells.
Insights
Human myeloma cells exhibit five distinct subpopulations. Interleukin-6 (IL-6) promotes the proliferation and CD45 expression of specific immature myeloma cell subsets, offering insights into myeloma biology.
Area of Science:
- Immunology
- Hematology
- Cancer Biology
Background:
- Multiple myeloma is a heterogeneous plasma cell malignancy.
- Understanding myeloma cell subpopulations is crucial for targeted therapies.
- Phenotypic characterization of myeloma cells remains an active area of research.
Purpose of the Study:
- To identify and characterize distinct subpopulations of human myeloma cells.
- To investigate the biological behavior of these subpopulations, including proliferation and response to IL-6.
- To elucidate the role of CD45 expression in myeloma cell heterogeneity.
Main Methods:
- Three-color phenotypic analysis of bone marrow mononuclear cells from myeloma patients.
- Detection of myeloma cell subpopulations using markers like CD38, CD45, and CD49e.
- Assessment of cell proliferation using Ki-67 antigen expression.
- In vitro culture experiments with IL-6 to evaluate cell viability and phenotypic changes.
Main Results:
- Five distinct myeloma cell subpopulations (CD38++) were identified based on CD45 and CD49e expression.
- Most myeloma cells lacked CD45, while some immature (MPC-1-) and mature (MPC-1+) myeloma cells expressed CD45 isoforms.
- Proliferating myeloma cells (Ki-67+) were predominantly found in MPC-1- and MPC-1-CD45+ fractions.
- IL-6 treatment enhanced the viability of MPC-1-CD45+ cells and induced CD45 expression on MPC-1-CD45- cells.
Conclusions:
- Human myeloma cells are phenotypically diverse, comprising at least five subpopulations.
- The MPC-1-CD45+CD49e- immature subpopulation contains IL-6-responsive proliferating cells.
- IL-6 plays a role in modulating CD45 expression and promoting the survival of specific myeloma cell subsets.