Folic acid-coupled nano-paclitaxel liposome reverses drug resistance in SKOV3/TAX ovarian cancer cells

Chemotherapy could be used as an effective treatment for ovarian cancer and subsequent peritoneal metastasis. Administration of chemoagents in a targeted manner may bring the advantage of higher efficiency and lower drug resistance. In the present study, folate receptor (FR)-targeted nano-paclitaxel formulations were generated and tested for cytotoxicity in a peritoneal xenograft model of paclitaxel-resistant ovarian cancer and SKOV3/TAX cell lines. Immunocytochemical staining confirmed the expression of FR in both SKOV3 and SKOV3/TAX cells. The enrichment of the folic acid-coupled PEGylated nano-paclitaxel liposome (FA-NP) in FR-positive cells was visualized with fluorescence. The uptake of the FA-NP peaked at 4 h and was more robust than nontargeted PEGylated nano-paclitaxel liposome (NP). FA-NP but not NP markedly inhibited the growth of ovarian cancer cells and induced a two-fold increase in the doubling time. The cytotoxic effects of FA-NP were more potent than NP in both SKOV3 cells [50% of inhibition concentration (IC50), 5.67 vs. 50.2 g/ml, FA-NP vs. NP] and SKOV3/TAX cells (IC50, 0.38 vs. >200 g/ml, FA-NP vs. NP). FA-NP caused more G2-M cell cycle arrest and apoptotic changes in ovarian cancer cells than NP or regular paclitaxel. However, these effects were blunted in the presence of free FA, which competitively inhibited the receptor-mediated uptake of FA-NP particles. Intraperitoneal (i.p.) administration of FA-NP but not regular paclitaxel, NP, or vehicle significantly prolonged the survival and reduced tumor nodule number (2.9 +/- 0.3) in BALB/c nude mice. FA-NP also markedly enhanced the percentage of apoptotic cells in peritoneal xenografts of paclitaxel-resistant ovarian cancer cells (44.6 +/- 8.5 vs. 3.2 +/- 1.1% for vehicle, 22.4 +/- 5.9% for regular paclitaxel, and 35.2 +/- 7.7% for NP; P<0.05). However, intravenous administration of FA-NP at the same dose failed to induce apoptosis (20.1 +/- 6.2%; P<0.05) and inhibit tumor nodule number to the same extent as intraperitoneal administration. FA-NP reversed the drug resistance in paclitaxel-resistant SKOV3/TAX ovarian cancer cells both in vitro and in vivo. Localized and targeted administration of the FR-targeted chemoagents might prolong the survival time in patients with drug-resistant ovarian cancer.