The antitumor and antimetastatic effects of N-trimethyl chitosan-encapsulated camptothecin on ovarian cancer with minimal side effects

Abstract

Lymphatic metastasis plays a critical role in ovarian cancer, indicates poor prognoses and correlates to the majority of cancer deaths. Camptothecin derivatives exhibit promising activity for the treatment of solid tumors because of its specific inhibition of eukaryotic DNA topoisomerase I. Yet, its application is hindered due to extreme water insolubility and severe side effects. It is essential to establish an efficient and safe protocol for the administration of camptothecin versus tumor metastasis and growth. In the current research, we encapsulated camptothecin with N-trimethyl chitosan (CPT-TMC) to increase its water-solubility and lower its side effects, and tested it on a high potential lymphogenous metastatic model of human ovarian cancer. In the prophase study, we successfully transfected SKOV3 cells with VEGF-D recombinant plasmid DNA (pcDNA3.1(+)/VEGF-D) to construct a cell line named SKOV3/VEGF-D and establish a feasible lymphogenous metastatic model. The antitumor and antimetastatic activities of CPT-TMC were evaluated in nude mice subcutaneously inoculated with SKOV3/VEGF-D cells at the left hindlimb claw pad. The tumor-bearing mice were divided randomly into four groups and treated twice per week for three weeks. Evan's Blue Dye was used to delineate functional lymphatic vessels. Lymphatic metastasis rates were detected by hematoxylin and eosin (HE) staining. Expression of VEGF-D and MMP-9 were investigated by immunohistochemistry. In contrast to controls, administration of CPT-TMC achieved effective inhibition in primary tumor volume and lymphogenous metastasis, yet without apparent systemic toxic effects. These effects were associated with simultaneously down-regulated VEGF-D and MMP-9 expression, significantly decreased tumor-associated lymphatic and blood sprouts, tremendously reduced systemic toxic effects, dramatically increased tumor apoptotic index. Our data indicate that CPT-TMC is superior to CPT by maximizing its anticancer and antimetastatic activities with minimal toxicity on hosts. CPT-TMC may become a potentially therapeutic strategy against human advanced ovarian cancer.