Transforming doxorubicin into a cancer stem cell killer via EpCAM aptamer-mediated delivery.

Chemotherapy-resistant cancer stem cells (CSCs) are a major obstacle to the effective treatment of many forms of cancer. To overcome CSC chemo-resistance, we developed a novel system by conjugating a CSC-targeting EpCAM aptamer with doxorubicin (Apt-DOX) to eliminate CSCs. Incubation of Apt-DOX with colorectal cancer cells resulted in high concentration and prolonged retention of DOX in the nuclei. Treatment of tumour-bearing xenograft mice with Apt-DOX resulted in at least 3-fold more inhibition of tumour growth and longer survival as well as a 30-fold lower frequency of CSC and a prolonged longer tumourigenic latency compared with those receiving the same dose of free DOX. Our data demonstrate that a CSC-targeting aptamer is able to transform a conventional chemotherapeutic agent into a CSC-killer to overcome drug resistance in solid tumours.