Orphan nuclear receptor NR2E3 and its small-molecule agonist induce cancer cell apoptosis through regulating p53, IFNα and MYC pathways

Orphan nuclear receptor NR2E3 activates p53 and induces cancer cell apoptosis. Further studies on p53-dependent and -independent functions of wild-type and mutated NR2E3 are needed. Herein, we showed that NR2E3 enhanced p53-DNA interactions in diverse cancer cells and up-regulated p53 and IFN pathways while down-regulating MYC pathway in cervical cancer cells. Studies of "All of Us" and TCGA databases showed NR2E3 nonsynonymous mutations associating with four cancers. We stratified NR2E3 SNVs for their cancer implications with the p53 reporter. A cancer-associated NR2E3R97Hmutation not only lost the wild-types tumor-suppressing functions but also prohibited the wild-type from enhancing p53 acetylation. These observations implicated the potential for pharmaceutically activating NR2E3 to suppress cancer. Indeed, NR2E3s small-molecule agonist 11a repressed 2-D and 3-D cultures of primary cells and cell lines of cervical cancer, in which screening FDA-approved anti-cancer drugs identified HDAC-1/2 inhibitor Romidepsin operating synergistically with 11a. The underlying molecular mechanisms included 11as down-regulating the transcription of Multidrug Resistance Protein ABCB1 that Romidepsin up-regulated. Transcriptomics studies revealed three synergy modes: (1) "sum-up" mode that the p53 pathway activated individually by 11a and Romidepsin got stronger by the combo; (2) "antagonism" mode that Romidepsin counteracted the activation of the Kras pathway by 11a; and (3) "de novo" mode that the combo instead of each individual drug repressed the MYC pathway. Conclusively, our experiments provide new data supporting tumor-suppressor like functions for wild-type NR2E3, reveal roles of mutated NR2E3 in cancer, and address values of NR2E3s agonist 11a in cancer therapy alone and combined.