Login to Access Video or Poster Abstract: MP83-19
Sources of Funding: Sanofi-Aventis GmbH, Frankfurt, Germany

Introduction

In leukemia and glioblastoma cells, a significant increase of apoptosis rates has been observed in vitro under cytostatic therapy by activation of the µ-opioid receptor with methadone. This study investigated the effect of opioid receptor activation in prostate cancer cells in presence of different cytotoxic drugs.

Methods

The prostate cancer cell lines PC-3, DU145 and LNCaP as well as control cell lines RCC-26 and A172 (renal cell carcinoma and glioblastoma) were incubated with different concentrations of the cytostatic drugs cabazitaxel and doxorubicin and the number of cells in apoptosis after 3 and 5 days was analyzed using flow cytometry (with annexin V-APC and 7AAD staining). In addition, the cells were incubated with various concentrations of L-methadone (0-100 µg/ml). Furthermore, gene expression analysis was performed using microarrays (Affymetrix GeneChip Prime View, ca. 49,000 transcripts) to detect changes in cell biology caused by methadone treatment.

Results

Incubation of PC-3 cells with 10 nM cabazitaxel resulted in 53% apoptosis after 5 days. This rate remained constant under co-incubation with L-methadone. Incubation with 0.3 µM doxorubicin resulted in 37% apoptosis after 5 days. In this setting, co-incubation with L-methadone showed a dose-dependent increase of apoptosis rate up to 88% (2.4-fold increase). Control experiments with fentanyl and naloxone instead of methadone showed no influence on apoptosis rate. Comparable and partly even clearer results were achieved with DU145, LNCaP, RCC-26 and A172 cells: the cabazitaxel-induced apoptosis rates remained stable under L-methadone, the doxorubicin-induced apoptosis was significantly increased by L-methadone (up to 3.8-fold increase). Microarray analysis revealed 128 upregulated and 398 downregulated genes (≥2-fold change of expression level, p<0.05) caused by L-methadone in PC-3 cells.

Conclusions

Stimulation of the µ-opioid receptors by L-methadone enhances the therapeutic effect of cytostatic drugs in prostate carcinoma cells and in other tumor cell lines. The increase of cytostatic effect depends on the combination of cell line and cytostatic agent. The combination of L-methadone with certain cytotoxic drugs can be a promising new approach to increase the therapeutic efficacy in hormone-refractory prostate carcinoma.

Funding

Sanofi-Aventis GmbH, Frankfurt, Germany