Evaluation of combination treatment benefits of nab-paclitaxel in experimental pancreatic cancer.

Abstract

170 Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive human cancers and is characterized by early tissue invasion, metastasis and high resistance to systemic therapies. Gemcitabine, a standard cytotoxic therapy for pancreatic cancer, has shown limited clinical benefits. Nanoparticle albumin-bound paclitaxel (nab-paclitaxel), an approved treatment for breast cancer, has shown efficacy as mono- and combination therapy in multiple tumor types including pancreatic, lung and ovarian cancer. We evaluated combination treatment benefits of nab-paclitaxel with gemcitabine in experimental pancreatic cancer. Methods: In vitro cell proliferation was evaluated by WST-1 assay in human PDAC cells. Animal survival studies were performed in murine xenografts. Results: Nab-paclitaxel inhibited in vitro proliferation of PDAC cell lines with IC50 levels of 7.6 mM, 208 nM, 519 nM and 526 nM for AsPC-1, BxPC-3, MIA PaCa-2 and Panc-1 cells. Nab-paclitaxel combination with gemcitabine had significant additive effect on inhibition of PDAC cell proliferation; 72-hour incubation demonstrated that nab-paclitaxel addition caused a 2.5, 2.5, 8.9 and 2.2-fold decrease in IC50 of gemcitabine in AsPC-1, BxPC-3, MIA PaCa-2 and Panc-1 cells, respectively. In an intraperitoneal murine xenograft model, 2-week therapy demonstrated that compared to controls (median survival: 23 days), animal survival increased after gemcitabine (27 days, p=0.05) and nab-paclitaxel monotherapy (35 days, p=0.0005). In a separate 3-week therapy experiment, animal survival was significantly longer in the nab-paclitaxel treated group (41 days, p<0.002 versus control and Gem) compared with gemcitabine (32 days, p=0.005 versus control), docetaxel (32 days, p=0.005) and controls (20 days). Animal survival in nab-paclitaxel / gemcitabine and docetaxel / gemcitabine sequential treatment group was 43 and 40 days, respectively. Conclusions: Nab-paclitaxel has significant antitumor activity as a single agent in experimental pancreatic cancer and can also enhance gemcitabine effects in combination. These findings provide a strong rationale for testing nab-paclitaxel in patients with pancreatic cancer.