Abstract 4096: Development of novel anticancer RNA therapeutics with dual-targeting siRNA that silences ubiquitin family members

Abstract Ubiquitination is a metabolic process in eukaryotic cells that modifies proteins with ubiquitin leading to protein degradation via the ubiquitin-proteosome pathway. Cellular levels of ubiquitin are driven by the expression of RPS27A, UBA52, UBB and UBC. In cancer, the dysregulation of ubiquitination can affect various aspects of tumor progression including cell cycle regulation and gene expression. Ubiquitin B (UBB) gene has been shown to be over-expressed in some tumor types, including NSCLC and cervical cancer, and under-expressed in other tumors, in particularly a subset of ovarian cancers. A role for ubiquitin C (UBC) in cancer has not been well established but UBC has been described as a biomarker in renal cancer and CLL. In recent studies, repression of UBB in ovarian cancer cells was associated with sensitivity to UBC knockdown and demonstrated a synthetic lethal relationship. Since both UBB and UBC show substantial sequence homology, we explored the possibility of developing dual targeting siRNA that would silence both UBB and UBC. We identified unique individual siRNA sequences that efficiently silenced both UBB and UBC and led to rapid cytotoxicity in several cancer cell lines including the colon cancer cell line HCT-116, the breast cancer cell line SK-BR3, and the prostate cancer cell line 22Rv1. Treatment with either UBB-specific or UBC-specific siRNA did not show the same lethal phenotype. Dose response assays using the dual targeting siRNA designated U21 indicated EC50 for cytotoxicity between 50–500 pM in several cancer lines. Treatment of cancer cell lines with U21 leads to rapid apoptosis and cell death. Chemical modifications to pharmacologically stabilize the U21 siRNA sequence did not change its activity. The efficient cytotoxic activity of the U21 siRNA sequence has been integrated into our SeekR™ platform to create aptamer-siRNA chimeras for targeted delivery of the lethal U21 payload to specific cancer cell types. Citation Format: David O. Azorsa, David W. Lee, Marvin O'Ketch, Nathalie A. Azorsa, Ioanna Papacharalampous, Lizette A. Castaño, Jeffrey A. Kiefer, Spyro Mousses. Development of novel anticancer RNA therapeutics with dual-targeting siRNA that silences ubiquitin family members [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 4096.