Liposome encapsulation reduces cantharidin toxicity.

Several reports have demonstrated that cantharidin is a strong anticancer compound in vitro; however,
its in vivo usefulness is often limited due to its high systemic toxicity. In this study, we encapsulated cantharidin
into pegylated liposomes and studied its activity against human breast cancer MCF-7 cells
in vitro and its systemic toxicity in mice. Another two methods were also used to reduce the dosage of
cantharidin, including labeling liposomal cantharidin with octreotide and exposing cells to hyperbaric
oxygen. The cytotoxic activity of pegylated liposomal cantharidin was drastically reduced compared with
free cantharidin in vitro. Octreotide-labeled pegylated liposomal cantharidin induced cell death by specifically
targeting somatostatin receptors in MCF-7 cells. Cell death was augmented with a low dose of
cantharidin under hyperbaric oxygen. Liposomal cantharidin had significantly less systemic toxicity than
free cantharidin in vivo and also exhibited a high efficacy against antitumor growth in nude mice. These
results suggest that the systemic toxicity of cantharidin can be mitigated by liposome encapsulation;
however, that did not decrease its antitumor activity.