Targeted cancer therapy aims to selectively kill cancer cells while avoiding healthy cells. Employing therapeutics including small molecules and antibody drug conjugates, while effective, exhibit complications, notably suboptimal targeting of cells. Thus, it is imperative to develop effective approaches for disease-targeted therapies. DNA origami (DO) is a molecular self-assembly process that allows for construction of custom designed complex nanostructures. This is achieved by folding a long strand of scaffold DNA with several short DNA strands into a pre-desired shape. Among its many uses, DO can act as a nanocarrier for chemotherapy drugs. However, DO can still bind to non-cancerous cells. To enhance targeting, we have retrofitted DO with antibodies (Abs). Prior research has explored the addition of antibodies to DO to program interactions with cells. Here, we are focused on developing this combination as a platform for selective killing of target cells in a complex blood cell population. We employ a previously designed rod-shaped DO, called the Horse, to selectively bind and internalize into only specific cells by targeting CD37. CD37 is a transmembrane protein expressed on myeloid and B cells. CD37 is an ideal target for Acute Myeloid Leukemia (AML) due to selective uptake via robust internalization properties in myeloid cells. We hypothesized that the incorporation of 1 or 2 anti-CD37 Abs onto the end of Horse-DO would target CD37⁺cells. Well-formed Horse-DO and Abs attachment was confirmed with gel electrophoresis and electron microscopy. Fluorophore-labeled anti-CD37-Horse-DO having 1 or 2 anti-CD37 Abs showed time dependent fluorescence increases in binding to CD37⁺ target THP1 AML cells, through flow cytometry and fluorescence microscopy, with an observed anti-CD37-(2)-Horse-DO mediated enhancement. Control experiments with Horse-DO and Horse-DO conjugated to 1 or 2 isotype control Abs showed little to no binding. This CD37 targeting effect was not observed in CD37-deficient (CD37^-) THP1 cells in single cell culture. Co-culture experiments with CD37⁺ and CD37^- THP1 AML cells confirmed selective binding and uptake into only target CD37⁺ populations. These findings suggest that anti-CD37-Horse-DO exhibits effective AML cell targeting and uptake in an antigen-specific manner. We are currently evaluating selective targeting in human blood sample. Next steps include loading these DO with chemotherapeutic drugs to study selective AML cell killing.

Kaitlin Morse

Appearances