Abstract 1463: Fxr1 is an oncogenic driver in ovarian cancer
Authors: George Jasmine , Kadamberi Ishaque P. , Geethadevi Anjali , Kumar Sudhir , Mittal Sonam , Rodriguez-Aguayo Cristian , Mangala Lingegowda S. , Sood Anil K. , Pradeep Sunila , Chaluvally-Raghavan Pradeep 
Published: April 2023

Introduction: Ovarian cancer is primarily driven by copy number variations, mutations in p53, BRCA1 or BRCA2 genes. Using the single nucleotide polymorphism (SNP) array data of The Cancer Genome Atlas (TCGA), we identified that FXR1 (Fragile X-Related protein 1), which is in the 3q26.3 chromosomal locus is either amplified or copy-gained in ~40% of ovarian cancer patients. As FXR1 plays a critical role in the pathogenesis of ovarian cancer, it is thought to be an attractive target for anticancer drugs. Nevertheless, till date, no specific chemical inhibitors are available that can target FXR1. Therefore, the goal of this study is to develop an agent that can knockdown the expression of FXR1.

Methods: We performed Surface sensing of translation (SUnSET) assay to demonstrate that FXR1 enhances the overall translation in cancer cells. RNA electromobility shift and proximity ligation assays were done to show that FXR1 binds to the AU Rich Elements (ARE) present within the 3'UTR of cMYC. Immunoprecipitation assay was performed to show interaction of FXR1 with translation initiation factors (eIFs). Western blotting was performed to evaluate the target specificity of customized FXR1-specific siRNAs FXR1. Flow cytometry analysis was then performed to see cell death and cell cycle arrest in ovarian cancer cells after siFXR1s (1-5) treatment. Live cell immunofluorescence was done to measure cellular uptake of siFXR1 labelled with Texas Red in cells. FXR1-specific siRNA incorporated DOPC was injected as 5 μg (200 μL) intraperitoneally twice a week starting 1 week after inoculation of cancer cells. The IVIS Lumina II Bioluminescence and Fluorescence Imaging System was used for in vivo bioluminescent imaging.

Results: Our previous data suggest that FXR1 is an important oncoprotein and has critical roles in the pathophysiology of ovarian cancer. We also found that FXR1 promoted the overall translation in cancer cells, which is a critical feature for oncogenesis. Our mechanistic investigation provided evidence that FXR1 upregulated cMYC protein levels by stabilizing cMYC mRNA via binding to AREs within its 3′UTR. We also found that FXR1 recruits eIFs to the translation initiation site. In our therapeutic approaches, we found that custom designed siRNAs against FXR1 shows maximum potency in reducing the FXR1 protein levels, induces G1-phase of cell cycle and apoptosis in ovarian cancer cells. Importantly, intraperitoneally delivery of siFXR1 incorporated in DOPC nanoliposomes inhibited ovarian tumor growth and prolonged survival of ovarian cancer bearing mice.

Conclusion: Our studies have identified that FXR1 is a critical molecule that is important for ovarian cancer progression. We discovered that cMYC is an important target of FXR1 required for FXR1-mediated oncogenesis. Moreover, DOPC encapsulation enhances the siFXR1 uptake, stability, efficiency of cellular delivery, biodistribution, and target-specific knockdown in vivo.

Citation Format: Jasmine George, Ishaque P. Kadamberi, Anjali Geethadevi, Sudhir Kumar, Sonam Mittal, Cristian Rodriguez-Aguayo, Lingegowda S. Mangala, Anil K. Sood, Sunila Pradeep, Pradeep Chaluvally-Raghavan. Fxr1 is an oncogenic driver in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1463.