Zoledronic acid down-regulates adhesion molecules of bone marrow stromal cells in multiple myeloma: a possible mechanism for its antitumor effect.
BACKGROUND
Myeloma plasma cells interact with the bone marrow microenvironment which, in turn, supports their growth and protects them from apoptosis. In vitro studies have demonstrated the antitumor potential of zoledronic acid (ZOL) on myeloma cell lines, but few data are available on its effects on bone marrow stromal cells (BMSCs). The aim of the current study was to evaluate the antiproliferative and apoptotic effect of ZOL on BMSCs, as well as its effect on the expression of adhesion molecules.


METHODS
BMSCs, obtained from bone marrow mononucleated cells of 8 patients with multiple myeloma, were treated with increasing concentrations of ZOL for 3 days. Cytotoxic effect was analyzed by 3-(4-5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide; thiazolyl blue (MTT) assay whereas the induction of apoptosis was evaluated by flow cytometric detection of fluorescein isothiocyanate-labeled annexin V, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, and nuclear changes. Moreover, expression of CD106, CD56, CD50, CD49d, CD44, and CD40 was analyzed by flow cytometry. Data were evaluated by the Friedman test.


RESULTS
After 3 days of exposure at concentrations of 10(-4) to 10(-5) M, ZOL induced a decrease in proliferation (P < 0.0001) and an increase in apoptosis (P < 0.002). Analysis of culture supernatants showed that myeloma BMSCs expressed interleukin (IL)-6, negligible levels of tumor necrosis factor-alpha, and no IL-1beta. In vitro exposure to the lowest concentrations of ZOL decreased IL-6 production by BMSCs. Among the adhesion molecules, CD106, CD54, CD49d, and CD40, which were strongly expressed at baseline, showed a statistically significant reduction compared with controls after exposure to ZOL.


CONCLUSIONS
ZOL interfered with myeloma BMSCs by reducing proliferation, increasing apoptosis, and modifying the pattern of expression of adhesion molecules, especially those involved in plasma cell binding. These effects on BMSCs might explain the antitumor activity of ZOL.
Corso
Alessandro
A
Division of Hematology, IRCCS Policlinico San Matteo, University of Pavia, Pavia, Italy. a.corso@smatteo.pv.it
Ferretti
Eleonora
E
Lunghi
Monia
M
Zappasodi
Patrizia
P
Mangiacavalli
Silvia
S
De Amici
Mara
M
Rusconi
Chiara
C
Varettoni
Marzia
M
Lazzarino
Mario
M
D017209:Apoptosis / Q000187:drug effects; D001854:Bone Marrow Cells / Q000187:drug effects* / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004164:Diphosphonates / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D010950:Plasma Cells / Q000187:drug effects; D017154:Stromal Cells / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured; D000077211:Zoledronic Acid
D015815:Cell Adhesion Molecules; D004164:Diphosphonates; D007093:Imidazoles; D000077211:Zoledronic Acid