Abstract 495: Targeting undruggable transcription factor HOXB13 in metastatic prostate cancer by CRISPR/Cas13d-based nanoparticle therapy
Authors: Cui Zhifen , Huang Furong , Fang Kun , Yan Jingyue , Zhou Yufan , Everitt Jeffrey , Zhao Yue , Hankey William , Chen Zhong , Wang Hongyan , Jin Victor X. , Dong Yizhou , Wang Qianben 
Published: March 2024

Abstract
Background: The oncogenic transcription factor HOXB13, which is highly expressed in castration-resistant prostate cancer (CRPC), has been shown to promote CRPC growth and metastasis. However, HOXB13 is considered untargetable by traditional small-molecule-based drug design. Gene therapy is critical alternative strategy with potential to directly target such traditionally undruggable genes.
Methods: Selective cell in organ targeting (SCORT) nanoparticles for precise delivery of nanoparticles to metastatic cancer cells in an organ were constructed and characterized by the NanoAssemblr Spark, Zetasizer Nano ZS, and transmission electron microscopy (TEM); Cas13d mRNA with pseudouridine modification was synthesized using in vitro transcription; Hemi-spleen injection of CRPC cells was performed to build CRPC liver metastatic models; RNA-seq was employed to evaluate off-target effects of Cas13d targeting.
Results: By incorporating a prostate cancer-specific E3 aptamer to functionalized lipid-like nanoparticles (FTT5 LNP-E3), we have successfully constructed SCORT nanoparticles that enable preferential delivery of mRNAs to metastatic CRPC cells in the liver, as opposed to various normal cells in the surrounding liver tissue. We demonstrated that Cas13d-pre-gHOXB13 mediates highly effective and specific HOXB13 mRNA knockdown in CRPC cells. Significantly, systemic treatment of SCORT nanoparticles carrying Cas13d-pre-gHOXB13 mRNA decreased HOXB13 expression in the metastatic tumors, inhibited metastasis, and prolonged survival of mice bearing androgen receptor (AR)-positive (AR+) or negative (AR-) tumors. Notably, long term (6 and a half weeks) administration of SCORT nanoparticle-Cas13d-pre-gHOXB13 did not significant alter body weight, hepatic and renal function, chemokines and cytokines, and other factors, effectively highlighting its safety.
Conclusions: This study is the first to demonstrate that undruggable oncogenic transcription factors can be targeted using nanoparticle-delivered gene therapy based on CRISPR/Cas13 RNA-targeting. The SCORT-CRISPR/Cas13d system is a highly flexible technology that would impact the larger field of translational science by allowing the design of Cas13d-based, cancer cell-specific delivered nanoparticles targeting other previously-undruggable oncogenic transcription factors in metastatic prostate cancer and other solid tumors.
Citation Format: Zhifen Cui, Furong Huang, Kun Fang, Jingyue Yan, Yufan Zhou, Jeffrey Everitt, Yue Zhao, William Hankey, Zhong Chen, Hongyan Wang, Victor X. Jin, Yizhou Dong, Qianben Wang. Targeting undruggable transcription factor HOXB13 in metastatic prostate cancer by CRISPR/Cas13d-based nanoparticle therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 495.