Aptamer-based Breast Cancer Targeted Therapy System And Multi-walled Carbon Nanotubes Indirect Toxicity In Vitro Studies

Breast cancer is the most common malignancy among women worldwide. HER2protein is an important target for breast cancer treatment, because a large proportion of breast cancers overexpress HER2. HER2-positive breast cancer is associated with increased invasiveness, higher recurrence, and poor prognosis. Trastuzumab (Herceptin) is approved for targeted treatment of HER2-positive breast cancer, but drug resistance is developed rapidly in virtually all patients. Thus, it is necessary to develop novel HER2-targeting therapeutic strategies. Aptamer-based tumor-targeted drug delivery is a promising approach that can increase the efficacy of chemotherapy and reduce the related toxicity. So far, however, aptamer-based HER2-targeting drug delivery system has not been reported. In this paper, we developed a novel HER2aptamer (HB5) and exploited its role as the targeting molecule for delivering doxorubicin (Dox) to HER2-positive breast cancer cells in vitro. The following are our findings:1. The selected aptamer (HB5) was86-nucleotide long and could bind to a HER2epitope with a Kdof18.9nM.2. The aptamer could also bind to the extracellular domain (ECD) of HER2protein, with minimal cross-reactivity to albumin or trypsin.3. The aptamer could preferentially bind to HER2-positive but not HER2-negative cells.4. An aptamer-doxorubicin complex (Apt-Dox) was formulated by intercalating Dox into the DNA structure of HB5. The Apt-Dox could selectively deliver Dox to HER2-positive cancer cells while reducing the drug intake by HER2-negative cells.5. Moreover, Apt-Dox retained the cytotoxicity of Dox against HER2-positive tumor cells, but reduced the toxicity of the drug against HER2-negative cells.The results indicate that HER2aptamers may potentially be utilized in targeted drug delivery to HER2-positive tumors. Since many types of malignancies including breast, ovarian, gastric, and lung cancers overexpress HER2protein, the study suggests a novel approach for developing targeted chemotherapeutics against these cancers. With the expansion of the potential applications of carbon nanotubes (CNT) in biomedical fields, the toxicity and biocompatibility of CNT have become issues of growing concern. Since the immune system often mediates tissue damage during pathogenesis, it is important to explore whether CNT can trigger cytotoxicity through affecting the immune functions. In the current study, we evaluated the influence of CNT on the cytotoxicity mediated by human lymphocytes in vitro. The results showed that while CNT at low concentrations (0.001to0.1μg/ml) did not cause obvious cell death or apoptosis directly, it enhanced lymphocyte-mediated cytotoxicity against multiple human cell lines. In addition, CNT increased the secretion of IFN-γ and TNF-a by the lymphocytes. CNT also upregulated the NF-κ B expression in lymphocytes, and the blockage of the NF-κB pathway reduced the lymphocyte-mediated cytotoxicity triggered by CNT. These results suggest that CNT at lower concentrations may prospectively initiate an indirect cytotoxicity through affecting the function of lymphocytes.