A novel therapeutic strategy utilizing EpCAM aptamer-conjugated gemcitabine for targeting bladder cancer and cancer stem cells

Abstract

Gemcitabine (GEM) is a first line chemotherapy drug for bladder cancer (BCa). GEM's lack of specificity has led to disadvantages, resulting in low efficiency, especially when combined with the targeted treatment of BCa stem cells (CSCs), which is considered the cause of BCa recurrence and progression. To enhance the anti-cancer effect and reduce the side effects of GEM targeting of BCa cells/CSCs, an aptamer drug conjugate (ApDC) targeted delivery system was used to improve the efficiency of GEM in BCa therapy using EpCAM aptamer-GEM conjugates based on the epithelial cell adhesion molecule (EpCAM), which is highly expressed on the cell membrane of BCa cells/CSCs. We designed and synthesized EpCAM aptamer gemcitabine conjugates (EpCAM-GEMs, one aptamer carried three GEMs). The targeting effect of EpCAM-GEMs was examined in a xenograft model using an in vivo imaging system. To evaluate the antitumor activity and mechanism of EpCAM-GEMs, Cell Counting Kit-8, apoptosis and colony formation assays; BCa CSC xenotransplantation; xenotransplantation of subcutaneous tumors; a lung metastasis model; an in situ model; and biosafety assessment were used in vitro and in vivo. EpCAM is highly expressed on the surface of BCa cells/CSCs. EpCAM-GEMs were automatically synthesized using a DNA synthesizer, were stable in serum, and selectively delivered GEM to kill BCa cells/CSCs. EpCAM-GEMs entered BCa cells via macropinocytosis, released GEM to inhibit DNA synthesis, and degraded all BCa cells under the action of a BCa cell intracellular phosphatase; however, they did not kill normal cells because of their low EpCAM expression. EpCAM-GEMs inhibited BCa growth and metastasis in three bladder tumor models, with good biosafety. These results demonstrated the targeted anti-tumor efficiency and good biosafety of EpCAM-GEMs in BCa treatment, which will provide a new therapeutic strategy in BCa biomarker targeted therapy.