Antitumor activity of nanoparticle albumin-bound paclitaxel in experimental gastric cancer.

Abstract

33 Background: Gastric cancer is the second most common cause of cancer related death worldwide and lacks highly effective adjuvant or definitive systemic treatment for advanced disease. Nab-paclitaxel is a novel microtubule-targeting cytotoxic agent and not tested in gastric cancer as of yet. Methods: Human gastric cancer cell lines AGS, NCI-N87 and SNU16 were studied for treatment effects on cell proliferation, mitotic arrests and apoptosis in vitro and vivo. Tumor growth and survival studies were performed in murine xenografts. Results: Nab-paclitaxel inhibited cell proliferation with an IC50 of 2.01 nM in SNU16, 23.3 nM in AGS and 48.69 nM in NCI-N87 cells after 72-hour treatment, which was lower than that of oxaliplatin (1.05 μM to 1.51μM) and epirubicin (0.12 μM to 0.25 μM). Nab-paclitaxel treatment caused increased expression of the mitotic-spindle associated phospho-stathmin, nuclear fragmentation or karyopyknosis, and apoptotic events as confirmed through increased expression of cleaved-PARP and caspase-3. After a two-week nab-paclitaxel, oxaliplatin or epirubicin treatment, the local tumor growth inhibition rate was 77, 17.2 and 21.4 percent, respectively (p=0.002). Effects of therapy on tumoral proliferative and apoptotic indices corresponded with tumor growth inhibition data, while expression of phospho-stathmin also increased in tissues. There was an increase in median animal survival after nab-paclitaxel treatment (86 days) compared to controls (24 days, p=0.0004) or to oxaliplatin therapy (37.5 days, p=0.0005). Conclusions: The strong antitumor activity of nab-paclitaxel in experimental gastric cancer supports such microtubule-targeting therapy for clinical application. Nab-paclitaxel benefits were observed independent from phosphorylated stathmin expression at baseline, putting into question the consideration of nab-paclitaxel use in gastric cancer based on this putative biomarker.