| Abstract |
Multiple myeloma is a neoplasm derived from abnormal plasma cells
exhibiting excessive proliferation either within or outside of the bone
marrow. While the majority of myelomas are classified into distinct types
based on the production of different classes of immunoglobulins, a small
percentage of these tumor cells fail to exhibit immunoglobulin secretion
and are classified as nonsecretory myelomas. The nonsecretory type is
further subdivided into the intracytoplasmic immunoglobulin producer and
nonproducer types. Notably, recent studies detected a novel form of
myeloma, oligosecretory myeloma, which comprises a portion of the
nonsecretory type. While the prevalence of the oligosecretory type
increases with disease progression, the mechanism underlying the
development of these cells remains unclear. Likewise, oligosecretory
myeloma cell lines remain rare. Here, we describe the development of a
new myeloma cell line, designated THK-72, from the pleural effusion of a
myeloma patient initially diagnosed with IgG kappa type myeloma, which
subsequently transformed to oligosecretory myeloma. THK-72 cells
proliferated in single suspension culture without any feeder layer or IL-6
supplementation, and no immunoglobulin secretion was detected in the
supernatant of these cells by immunoelectrophoresis analysis.
Morphological analyses indicated that THK-72 cells had plasmacytoid
appearance, while PCR and flow cytometry analyses demonstrated that the
cells were negative for B-cell marker and EBV-infection, thereby
indicating that THK-72 comprises a 'true' myeloma cell line.
Interestingly, contrary to the bortezomib resistance observed during the
clinical course, the THK-72 cells were sensitive to bortezomib in vitro.
As THK-72 arose from a classical myeloma, this oligosecretory myeloma
cell line will be useful for studies regarding the biological nature of
plasma cell neoplasms.
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