Novel HER2 Aptamer Selectively Delivers Cytotoxic Drug to HER2-positive Breast Cancer Cells in Vitro

Abstract

BackgroundAptamer-based tumor targeted drug delivery system is a promising approach that may increase the efficacy of chemotherapy and reduce the related toxicity. HER2 protein is an attractive target for tumor-specific drug delivery because of its overexpression in multiple malignancies, including breast, gastric, ovarian, and lung cancers.MethodsIn this paper, we developed a new HER2 aptamer (HB5) by using systematic evolution of ligands by exponential enrichment technology (SELEX) and exploited its role as a targeting ligand for delivering doxorubicin (Dox) to breast cancer cells in vitro.ResultsThe selected aptamer was an 86-nucleotide DNA molecule that bound to an epitope peptide of HER2 with a Kd of 18.9 nM. The aptamer also bound to the extracellular domain (ECD) of HER2 protein with a Kdof 316 nM, and had minimal cross reactivity to albumin or trypsin. In addition, the aptamer was found to preferentially bind to HER2-positive but not HER2-negative breast cancer cells. An aptamer-doxorubicin complex (Apt-Dox) was formulated by intercalating Dox into the DNA structure of HB5. The Apt-Dox complex could selectively deliver Dox to HER2-positive breast cancer cells while reducing the drug intake by HER2-negative cells in vitro. Moreover, Apt-Dox retained the cytotoxicity of Dox against HER2-positive breast cancer cells, but reduced the cytotoxicity to HER2-negative cells.ConclusionsThe results suggest that the selected HER2 aptamer may have application potentials in targeted therapy against HER2-positive breast cancer cells.

Biodistribution of Novel 68Ga-Radiolabelled HER2 Aptamers in Mice

“…This may explain the lower uptake of the 68 Ga-radiolabelled aptamers in the MDA-MB-231 tumours. These results also demonstrate the importance of analysing the xenografted tumours by 18 FDG PET.…”

“…These results suggest that tumour uptake was more related to the tumour composition factors (such as cellular composition, EC matrix, vascular network, lymphatic system and necrosis) than to the expression of HER2. 18 FDG PET scanning revealed heterogeneous 18 FDG uptake due to tumour necrosis. We observed more often necrotic centres in the MDA-MB-231 tumours versus SKOV3 tumours.…”

“…Figure 2 shows the experimental set-up, including tumour cell injections, 18 F-FDG PET/CT scan and 68 Ga-radiolabelled HER2 aptamer PET/MRI scan. All mice were analysed at the same age.…”

“…Aptamers possess several advantages over antibodies and proteins such as easy and inexpensive chemical synthesis, low immunogenicity and non-toxicity. Several aptamers targeting HER2 have been reported [11][12][13][14][15][16][17][18]. So far, only one of these aptamers has been radiolabelled (with 99mTc) and its biodistribution was evaluated ex vivo [19,20].…”

HER2/neu: an increasingly important therapeutic target. Part 1: basic biology & therapeutic armamentarium

“…Additionally, bispecific antibodies targeting HER2/neu have been developed [123][124][125][126][127] taking advantage of the intrinsic immunologic function of antibodies recognizing HER2/neu. Finally, aptamers selected for recognition and binding to the HER2/neu molecule can deliver cytotoxic agents to HER2/neu-positive cells as an alternative to antibody-based delivery [128].…”