The objective of this study was to determine potential mechanisms of apoptotic activity of
gemcitabine, a
pyrimidine nucleoside analogue, in the MM1.S
multiple myeloma (MM) cell line. A MM cell line that is sensitive to
glucocorticoids (MM1.S) was used for this study. Immunoblotting analysis, cell cycle assays, and
annexin V staining were performed to determine whether
gemcitabine induced apoptosis in this model. Furthermore, we attempted to delineate the apoptotic pathway by measuring
caspase-8 and -9 activity using fluorometric assays. Loss of mitochondrial membrane potential was measured by flow cytometry.
Gemcitabine treatment caused apoptosis in MM cell lines as measured by an increase in DNA cleavage, an increase in
annexin V binding, a decrease in the mitochondrial membrane potential, and activation of
caspase activity. Furthermore, cleavage of the
caspase substrate
poly(ADP-ribose) polymerase and
caspase-3 activation were documented as early
as 8 h
after treatment with
gemcitabine.
Caspase-8 and -9 were activated by
gemcitabine treatment in this cell line, suggesting several mechanisms of action including
death receptor pathway and mitochondrial damage. The addition of
interleukin 6 to MM1.S cells treated with
gemcitabine offered no protection against
gemcitabine-induced cell death.
Gemcitabine induced apoptosis in the MM1.S cell line, and its activity required
caspase activation. There is a suggestion that mitochondrial integrity is being affected with
gemcitabine in this system.
Gemcitabine acts independently of
interleukin 6, suggesting potential important therapeutic implications in MM patients.