Inhibition of pancreatic cancer and potentiation of gemcitabine effects by the extract of Pao Pereira

Lack of effective therapy is a major problem in the treatment of pancreatic cancer. In the present study, we investigated a natural product, the extract of Pao Pereira (Pao), for its anti-pancreatic cancer effect in vitro and in vivo, either alone or in combination with the first-line chemotherapeutic drug gemcitabine (Gem). Pao induced dose-dependent apoptosis to all five tested pancreatic cancer cell lines. The combination of Pao and Gem had a synergistic effect in the inhibition of cell growth, with combination indices (CIs) <1 by Chou-Talalay's median effect analysis based on the isobologram principle. Adding Pao to Gem treatment reduced the concentration of Gem to produce an equitoxic effect on pancreatic cancer cells. In an orthotopic pancreatic xenograft mouse model, mice bearing PACN-1 tumors were treated with Pao and Gem, either alone or in combination. The progression of tumors was monitored longitudinally by imaging of live animals. While Gem did not provide significant inhibition, Pao treatment significantly suppressed tumor growth by 70-72%. Combined Pao and Gem treatment further enhanced the tumor inhibitory effect compared to Gem alone, and markedly reduced metastatic lesions in the peritoneum. Collectively, these data suggest that the extract of Pao possesses anti-pancreatic cancer activity and can enhance the effects of Gem in vitro and in vivo.