Chemosensitization of gemcitabine‐resistant human bladder cancer cell line both in vitro and in vivo using antisense oligonucleotide targeting the anti‐apoptotic gene,clusterin

OBJECTIVE

To characterize changes in clusterin (sCLU‐2) expression in bladder cancer cells after continuous treatment with gemcitabine and to determine whether knockdown of sCLU‐2 can re‐introduce sensitivity of gemcitabine‐resistant cells to treatment with gemcitabine.

MATERIALS AND METHODS

A human bladder cancer cell line, UM‐UC‐3, was continuously exposed to increasing doses of gemcitabine in vitro, and a gemcitabine‐resistant cell line UM‐UC‐3R was developed. The role of sCLU‐2 in chemoresistant phenotype acquired in both in vitro and in vivo was then analysed using antisense oligonucleotide targeting the sCLU‐2 gene (OGX‐011).

RESULTS

Treatment of parental UM‐UC‐3 cells (UM‐UC‐3P) with gemcitabine induced transient up‐regulation of sCLU‐2 protein. There was a sustained increase in sCLU‐2 expression levels in UM‐UC‐3R compared with UM‐UC‐3P cells (6.4‐fold). Treatment of UM‐UC‐3R cells with OGX‐011 resulted in a dose‐dependent and sequence‐ specific inhibition in sCLU‐2 expression. Furthermore, OGX‐011 chemo‐sensitized UM‐UC‐3R cells to gemcitabine in vitro with a reduction in the concentration that reduces the effect by 50% (IC₅₀) from 100 nm to 10 nm . Tumour volume and the incidence of metastasis in nude mice injected with UM‐UC‐3R cells was significantly greater than those of nude mice injected with UM‐UC‐3P cells; however, systemic administration of OGX‐011 plus a low dose of gemcitabine significantly suppressed tumour volume and the incidence of metastasis in both groups.

CONCLUSION

These findings suggest that sCLU‐2 plays a significant role in the acquisition of chemoresistant phenotype in bladder cancer cells and the knockdown of sCLU‐2 using OGX‐011 combined with a chemotherapeutic agent could be an attractive approach for advanced bladder cancer through the enhancement of chemosensitivity.