Abstract 1494: 5-methyltetrahydrofolate (5-MTHF) as a superior ligand for delivery of small RNAs for cancer therapy

Abstract

Abstract MicroRNAs (miRNAs) are small noncoding RNAs that regulate a wide array of genes. Because miRNA downregulate translation proteins associated with cancer progression, miRNA-based therapeutics have great potential as anticancer drugs. Nonetheless, the therapeutic potential of miRNA replacement is limited due to lack of safe and efficient delivery vehicles, and inability to target miRNAs to the intended cells/tissues. Thus, identifying molecules that are able to deliver therapeutic miRNA is of critical need. This could be achieved by targeting receptors that are overexpressed on target tumor cells. For example, the folate receptor (FR) is overexpressed on various tumor types including breast, lung, ovarian and brain tumors. Our laboratory has previously developed a unique strategy that directly links a miRNA mimic to the high affinity FR ligand, folate (FolamiRs). In the present work, to further improve the potency of FolamiRs, we introduce the reduced folate metabolite, 5-methyltetrahydrofolate (5-MTHF) that maintains nanomolar affinity for the FR at pH 7, but disengages from the FR at a significantly higher pH than that of folate, which is important when including an endosomal escape agent that typically disrupts endosomal acidification. We synthesize and conjugate 5-MTHF ligand to the potent tumor suppressor miRNA-34a (5-MTHF-miR-34a). We show that 5-MTHF-miR-34a uptake is specific to the cells overexpressing FR and represses target gene expression. Our data supports the use of 5-MTHF in combination with the endosomal escape agent, nigericin, to achieve robust cytosolic localization of therapeutically relevant miRNAs such as miR-34a. This work provides the foundation for future studies using 5-MTHF- conjugated therapeutic agents for targeting additional FR expressing cells, including myeloid derived suppressor cells (MDSCs) and macrophages. Collectively these studies will pave the way for developing 5-MTHF-based small RNA conjugates for treating FR-expressing cancers. The details of these intriguing results will be discussed in the poster. Citation Format: Sudarsan R. Kasireddy, Ahmed M. Abdelaal, Philip S. Low, Andrea L. Kasinski. 5-methyltetrahydrofolate (5-MTHF) as a superior ligand for delivery of small RNAs for cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1494.