Login to Access Video or Poster Abstract: MP98-18
Sources of Funding: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2012R1A1A2043965).

Introduction

Here we report the role of HSP90 in platinum resistance in human bladder cancer cells and synergistic antitumor effect of HSP90 inhibition on the combination therapy of NVP-BEZ245 and platinum in cisplatin-resistant human bladder cancer cells.

Methods

To evaluate differential gene expression according to different platinum sensitivity in human bladder cancer cells, we conducted microarray analysis-based gene expression profiling with cisplatin sensitive (T24) and resistant (T24R2) human bladder cancer cells and the results were validated by Western blot analysis. To test synergism between drugs combination index based on CCK-8 assay and also colony forming assay were used. To determine mechanisms underlying synergistic interaction between drugs, flow cytometry and Western blot analysis were performed.

Results

Gene expression profiling showed that the expression of 5,021 and 1,727 genes had more than two-fold and four-fold changes between T24 and T24R2 cells after platinum treatment. Especially Hsp90 (HSP90AA1, HSP90AA2) and RAS-MEK-MAPK and PI3K-AKT-mTOR signaling pathways showed significantly different expressions in the two cell lines. The combination of NVP-BEZ235 and satraplatin showed strong synergistic antitumor effect in cisplatin-resistant T24R2 cells. However, we found that both NVP-BEZ235 monotherapy and combination treatment with satraplatin caused increased phosphorylation of MEK1/2 and ERK1/2 despite of the suppression of PI3K/AKT signaling in T24R2 cells. The addition of 17-DMAG, HSP90 inhibitor to NVP-BEZ235 and satraplatin combination therapy down regulated both AKT and ERK signaling and synergistically enhanced antitumor effect in T24R2 cells through the caspase-dependent apoptosis and phase-specific cell cycle arrest.

Conclusions

The present study demonstrated that HSP90 plays important role for the platinum resistance in human bladder cancer cells. Also our findings suggest that through the inhibition of HSP90 activity, antitumor effect of PI3K/mTOR inhibitor and platinum combination therapy can be synergistically potentiated.

Funding

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2012R1A1A2043965).