Uncovering the importance of lipofection for aptamer-mediated therapeutic oligonucleotide delivery in a HER2+ SKBR3 breast cancer cell line.

The human epidermal growth factor receptor 2 (HER2) plays an important role as a transmembrane receptor, contributing to signaling activities implicated in cellular proliferation, differentiation, and survival. Across select tumor types, HER2 is pro-oncogenic, facilitating cancer initiation, progression and metastatic spread, leading towards treatment resistance. Further, cell surface presentation and signaling activity of HER2 has led to the development of precision oncology therapeutic approaches. In this study, a HER2-targeting DNA aptamer was modified into a novel chimeric sequence with an RNA sense strand that was hybridized with a complementary antisense RNA or DNA sequence for aptamer-mediated HER2 cellular uptake in a representative HER2 positive (+) SKBR3 breast cancer cell line. The incorporation of antisense oligonucleotide (ASO) and short interfering (si) RNA within the chimeric HER2-aptamer elicited favorable hybrid duplex secondary structures and thermal stability profiles for biological activity. Enzymatic (Ribonuclease H, RNase H) digestion of the RNA sense strand made the chimeric HER2-aptamer:ASO hybrid applicable for antisense and with siRNA for RNA interference (RNAi) gene silencing activities against the stress-inducible oncoprotein, Glucose Regulated Protein 78, GRP78, as a key regulator of cancer cell survival and apoptosis. The chimeric ASO and siRNA conjugated aptamer demonstrated cellular binding and uptake activities directly in the HER2 presenting SKBR3 cell line and downstream GRP78 silencing (siRNA) activity that was dependent on a Lipofectamine-based formulation, underscoring the importance of the transfection agent for cellular delivery of genetic therapies.