Effect of hyperbaric oxygenation and gemcitabine on apoptosis of pancreatic ductal tumor cells in vitro

Background: Gemcitabine is first-line therapy for advanced pancreatic ductal adenocarcinoma (PDAC) with a poor survival and response rate. Hyperbaric oxygenation (HBO) enhances delivery of oxygen to hypoxic tumor cells and increases their susceptibility to cytotoxic effects of chemotherapy. We hypothesized that the anticancer activity of gemcitabine (GEM) may be enhanced if tumor cells are placed in an oxygen-rich environment. The present study evaluated the effects of gemcitabine, HBO and their combination on apoptosis of tumor cells. Materials and Methods: PANC-1 and AsPc-1 PDAC tumor cell lines were used. Cultured tumor cells were treated with GEM at its growth-inhibitory concentration (IC50) , HBO at 2.5 ATA for 90 min, a combination of both (HBO before GEM [HBO-GEM] and GEM before HBO [GEM-HBO]) and with the administration at the same time of GEM and HBO (GEM+HBO). In the control group (Ctrl) the tumor cells were treated with PBS (as placebo) equal in quantity to that used to dissolve gemcitabine for administering to the experimental samples. Twenty-four hours later, apoptotic cells in each group were analyzed and the apoptotic index (AI) was calculated. Results: PANC-1 cell line: HBO alone had no effect on AI: 6.5±0.1 vs. 5.9±0.1. HBO before and after gemcitabine did not further increase AI: 8.2±0.1 (HBO-GEM), 8.5±0.1 (GEM-HBO) vs. 8.1±0.1 (GEM). The combination of HBO and gemcitabine significantly increased AI: 10.7±0.02 (p<0.001 vs. all groups). AsPc-1 cell line:HBO-alone had no effect on AI: 5.9±0.1 vs. 5.9±0.1. HBO before and after gemcitabine did not further increase AI: 8.2±0.1 (HBO-GEM), 8.4±0.1 (GEM-HBO) vs. 8.0±0.1 (GEM). The combination of HBO and gemcitabine significantly increased AI: 9.7±0.1 (p<0.001 vs. all groups). Conclusion: HBO-alone, whether administered before and after gemcitabine has no effect on apoptosis of PDAC cells in vitro. HBO significantly enhanced gemcitabine-induced apoptosis when administered during gemcitabine. Our findings suggest that the time window would be critical for using HBO as adjuvant to chemotherapy.