Abstract 4863: Targeting the NFAT1-MDM2-MDMX network for prostate cancer therapy

Abstract

Abstract The MDM2 and MDMX oncogenes are overexpressed in human prostate cancer, promoting tumor growth and metastasis. We recently demonstrate that the transcription factor NFAT1 activates MDM2 oncogene, independent of p53. The present study was designed to examine the effectiveness of targeting the NFAT1-MDM2-MDMX network for prostate cancer therapy. We identified a natural product NFAT1-MDM2 inhibitor, Inulanolide A (InuA) in the present study. The anticancer activity of InuA and its effects on the expression and stability of NFAT1, MDM2, and MDMX were examined in human prostate cancer cell lines with different genetic background, including LNCaP (p53 wild-type, AR positive), PC3 (p53 null, AR negative) and DU145 (p53 mutant, AR negative) cells. Our molecular docking studies predicted the binding ability and binding sites of InuA on NFAT1, MDM2, and MDMX. Its binding affinity and specificity were investigated using recombinant proteins and biotinylated InuA. To further demonstrate the specificity of InuA in targeting NFAT1-MDM2-MDMX network and the importance of NFAT1-MDM2-MDMX network in InuA's anticancer activity, the transient overexpression (OE) and knockdown (KD) experiments of these genes, as well as the pharmacological activators and inhibitors of NFAT1 signaling, were used. Our results indicated that InuA directly bound to the DNA binding domain of NFAT1, leading to a marked inhibition of MDM2 transcription. The compound also bound to the RING domains of MDM2 and MDMX with high affinity, inhibited the MDM2-MDMX binding, and enhanced MDM2 protein degradation. InuA inhibited the proliferation, migration, and invasion of prostate cancer cells, regardless of their p53 status and AR responsiveness. The expression of NFAT1, MDM2, and MDMX were important for InuA's anticancer activity, as demonstrated using the cancer cell lines with transient OE and KD of these genes. In conclusion, InuA represents a novel class of NFAT1-MDM2-MDMX inhibitor, and inhibiting the NFAT1-MDM2-MDMX network may be a promising strategy for prostate cancer therapy. (Supported by NIH R01 CA186662 and R01CA214019 and ACS RSG-15-009-01-CDD.) Citation Format: Jiang-Jiang Qin, Xin Li, Wei Wang, Ruiwen Zhang. Targeting the NFAT1-MDM2-MDMX network for prostate cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4863.