Abstract 275: Development of RNAi-dendrimer-based Twist1 inhibitors to reduce metastasis and recurrence in ovarian cancer.

Abstract

Abstract Background/Objective: Epithelial ovarian cancer (EOC) is the most lethal gynecologic cancer, with the vast majority of patients eventually developing a recurrence. One promising novel therapeutic target is Twist1, a basic helix-loop-helix transcription factor that acts as a master regulator of epithelial to mesenchymal transition (EMT), an important step in metastasis, of which loss of E-cadherin is the hallmark. Furthermore, Twist1 is a key component in the differentiation of EOC stem cells into metastatic cancer cells. Methods: We investigated the effectiveness of three siTwist-candidates and two types of Poly (amidoamine) (PAMAM) dendrimers on intracellular delivery of siRNA to ovarian cancer cell lines. The EOC cell lines TOV112D, TARA R182 (immortalized primary EOC cells) and A2780R (cisplatin-resistant derivatives of the A2780 EOC cell line) were used. Two types of PAMAM dendrimers, Generation 5 (G5) and a new G3 dendrimer (YTZ3-15) were examined, which differ based on the numbers of surface amines. We complexed multiple Twist1-specific siRNA constructs to PAMAM dendrimers to protect fragile RNA and facilitate delivery. We loaded G5 and YTZ3-15 dendrimers with Cy3-labeled siTwist-506 and transfected TOV112D cells with these complexes. Quantitative real-time PCR (QPCR) and Western blotting were used to evaluate Twist1 knockdown in four EOC cell lines following transfection with siTwist. Results: Bright field and fluorescent microscopy analysis showed that ∼95-98% of TOV112D cells contained Cy3 label, indicating that both the G5 and YTZ3-15 dendrimers can penetrate the cell membranes of EOC cells. Cy3-labeled siTwist-506 led to a 50% reduction in Twist1 mRNA in these cells. Further analysis revealed that novel siRNA sequences siTwist-419 and 494 significantly reduced Twist1 protein expression compared to siTw506 and non-transfected controls, and real-time RT-PCR analysis revealed a 80% reduction in Twist1 mRNA in both TARA R182 and A2780R EOC cells. This suggests that siTwist-419 and 494 can lead to optimal Twist1 silencing. Conclusions: Our data support the feasibility of using siTwist-dendriplex approaches to knock down Twist1 expression in EOC cells, by circumventing a major obstacle to the targeting of transcription factors with dendrimer technology. Further studies are needed to prove whether the prevention of Twist1 production will reduce EOC metastases, and prevent recurrences by arresting EOC stem cells in an undifferentiated state. Citation Format: Cai Roberts, James Finlay, Gina Lowe, Thanh H. Dellinger, Ernest Han, Carlotta Glackin. Development of RNAi-dendrimer-based Twist1 inhibitors to reduce metastasis and recurrence in ovarian cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 275. doi:10.1158/1538-7445.AM2013-275