The poor overall survival rate of pancreatic ductal adenocarcinoma (PDAC), less than 10% over 5 years, is largely due to the majority of patients presenting with overt metastatic burden or post-surgical recurrence of micrometastases. Due to these factors, new treatment methods are needed to effectively target both primary and metastatic tumors.

We have previously established that the mRNA binding protein Human antigen R (HuR), is an important molecule for PDAC progression. In a tumor microarray of matched normal and malignant patient tissues, we found active HuR staining in 79% of tumor samples, which was not seen in normal pancreatic tissue (n=70). We have shown that homozygous CRISPR knock-out of HuR results in xenograft lethality, as well as sensitization of PDAC cell lines to standard-of-care chemotherapy. Therefore, in the current experiments we have utilized a targeted 3DNA nanocarrier for the delivery of an RNA silencer against HuR in order to enhance tumor susceptibility to chemotherapy. Treatment of PDAC cell lines with this 3DNA nanocarrier was highly effective in knocking down both HuR and established HuR targets (DCK, IDH1, PIM1).

To increase the specificity of the 3DNA nanocarrier, we sought to discover targeting moieties specifically upregulated in PDAC. We found increased folic acid receptor (FAR) expression in HS 766T, MIA PaCa-2, and PANC-1 PDAC cell lines with an average fold change of 2.6, in comparison to normal pancreatic cells. Additionally, patient tissue samples showed elevated FAR levels in 100% of tumors (n=80). Thus, by attaching folic acid to the 3DNA nanocarrier (FA-3DNA), we were able to target the nanocarrier specifically to tumors, both primary and metastatic. This was detected by tagging FA-3DNA with Alexa750 fluorophore and monitoring its movement in mice bearing luciferase expressing-MIA PaCa-2 tumors. FA-3DNA had a longer half-life and increased delivery to tumors, as compared to non-targeted 3DNA.

We also demonstrated that treatment of mice with FA-3DNA conjugated with an RNA silencer for HuR (FA-3DNA-siHuR) led to a significant decrease in HuR mRNA and protein, in comparison to mice treated with 3DNA containing a control RNA silencer (FA-3DNA-siControl). Subsequent in vivo experiments showed prolong survival of mice treated with FA-3DNA-siHuR, as compared to mice treated with FA-3DNA-siControl (p=0.04).

Our previous work has established HuR as a promising therapeutic target in PDAC. In both in vitro and in vivo models, we have shown FA-3DNA-siHuR is capable of targeting tumors directly for the inhibition of HuR. These results suggest treatment with FA-3DNA-siHuR will sensitize tumors to standard of care chemotherapy, which can be introduced systemically or incorporated into the 3DNA nanocarrier for direct delivery. The latter could potentially increase the efficiency of the chemotherapy, and also of critical importance, reduce the toxic adverse effects of systemic chemotherapy.

Citation Format: Grace McCarthy, Christopher Schultz, Aditi Jain, Teena Dhir, Charles Yeo, Jessica Bowers, Lou Casta, Kelly Rhodes, Lori Getts, Robert Getts, Trevor Baybutt, Adam Snook, Jonathan Brody. Targeted 3DNA-siHuR nanocarrier therapy for pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3614.