Clusterin expression is highly up-regulated in several normal and malignant tissues undergoing apoptosis. Although recent studies have demonstrated a protective role of
clusterin expression against various kinds of apoptotic stimuli, the functional role of
clusterin in the acquisition of a
therapy-resistant phenotype in
bladder cancer remains unknown. The objectives of this study were to determine whether antisense (AS)
oligodeoxynucleotide (ODN) targeting the
clusterin gene enhances apoptosis induced by
cisplatin and to evaluate the usefulness of combined treatment with AS
clusterin ODN and
cisplatin in the inhibition of KoTCC-1
tumor growth and
metastasis in a human
bladder cancer KoTCC-1 model. We initially revealed the dose-dependent and sequence-specific inhibition of
clusterin expression by AS
clusterin ODN treatment in KoTCC-1 cells at both
mRNA and
protein levels.
Clusterin mRNA was increased in a dose-dependent manner by
cisplatin treatment at concentrations < or =10 mg/ml, and
clusterin mRNA up-regulation induced by 10 mg/ml
cisplatin peaked by 48-h post-treatment and began decreasing by 72-h post-treatment. Although there was no significant effect on growth of KoTCC-1 cells, AS
clusterin ODN treatment significantly enhanced
cisplatin chemosensitivity of KoTCC-1 cells in a dose-dependent manner, reducing the IC(50) by >50%. Characteristic apoptotic
DNA ladder formation and cleavage of
poly(ADP-ribose) polymerase protein were detected after combined treatment with AS
clusterin ODN and
cisplatin but not either agent alone. In vivo systemic administration of AS
clusterin and
cisplatin significantly decreased the s.c. KoTCC-1
tumor volume compared with mismatch control ODN plus
cisplatin. Furthermore, after the orthotopic implantation of KoTCC-1 cells, combined treatment with AS
clusterin and
cisplatin significantly inhibited the growth of primary KoTCC-1
tumors, as well as the incidence of
lymph node metastasis. Collectively, these findings demonstrated that
clusterin helps confer a chemoresistant phenotype through inhibition of apoptosis and that combined AS
clusterin ODN may be useful in enhancing the effects of cytotoxic
chemotherapy in patients with
bladder cancer.