Muc1 Aptamers Screening In Targeted Cancer Therapy Applied Research

Objective:Chemotherapy is a primary treatment for cancer, but its efficacy is often limited by the adverse effects of cytotoxic agents. Targeted drug delivery may reduce the non-specific toxicity of chemotherapy by selectively directing anticancer drugs to tumor cells. MUCl protein is an attractive target for tumor-specific drug delivery owning to its overexpression in most adenocarcinomas. Aptamers are single-strand oligonucleotides that can bind to target molecules with high affinity and specificity. Aptamers possess distinctive advantages as targeting ligand:high affinity for binding to most molecules, limited synthesis cost, low-immunogenicity, and small size that allows it to penetrate solid tumors. Due to these advantages, aptamers have been employed as novel targeting ligands in drug delivery systems. Here in this study, we developed a novel MUCl aptamer, and evaluated its capacity for delivering doxorubicin (Dox) to MUCl positive cancer cells in vitro.Methods:Using the SELEX technique and a peptide epitope of MUCl as target, we selected an86-base DNA aptamer (termed MA3). Flow cytometry was employed to monitor the bindings of the aptamer to albumin, MUC1-positive cancer cells (MCF7and A549), and MUC1-negative cells (HepG2å’ŒL02). To evaluate whether Dox was incorporated into MA3and formed an Apt-Dox complex, we made use of the phenomenon that the fluorescence from Dox would be quenched after intercalating into DNA, and measured the fluorescence spectrum of the complex. Confocal microscopy and flow cytometry were used to evaluate the uptake of Apt-Dox complex by either MUCl-positive (A549) or MUCl-negative (HepG2) cells. MTS assay was used to evaluate the cytotoxicity of Apt-Dox complex against MUC1-positive (A549) or MUC1-negative (HepG2) cells.Results:(1) We developed an86-base DNA aptamer (MA3) that bound to a peptide epitope of MUC1with a Kd of38.3nM and minimal cross reactivity to albumin.(2) Using A549lung cancer and MCF7breast cancer cells as MUCl-expressing models, MA3was found to preferentially bind to MUCl-positive but not MUCl-negative cells.(3) An aptamer-doxorubicin complex (Apt-Dox) was formulated by intercalating doxorubicin into the DNA structure of MA3. Apt-Dox was found capable of carrying doxorubicin into MUCl-positive tumor cells, while significantly reducing the drug intake by MUCl-negative cells.(4) Apt-Dox retained the efficacy of doxorubicin against MUC1-positive tumor cells, but lowered the toxicity to MUC1-negative cells (P<0.01).Conclusion:A novel MUCl aptamer MA3is developed in this study. The Apt-Dox complex could selectively deliver the cytotoxic agent doxorubicin to MUCl-positive cells, while reducing the drug uptake by MUCl-negative cells. Since MUCl is over-expressed in most adenocarcinomas, the aptamer may have potential utility as a guiding ligand for targeted chemotherapy against these malignancies.