Panoply™ Human RORC Over-expressing Stable Cell Line

Triple-negative breast cancer (TNBC) is a heterogeneous disease characterized by poor response to standard therapies and consequently a dismal clinical prognosis. ROR nuclear receptors are multifunctional transcription factors that play important roles in circadian rhythm pathways and other processes, including immunity and tumorigenesis. Nobiletin (NOB), a natural compound known to have anticancer properties, has previously been shown to activate RORs, thereby enhancing circadian rhythms and promoting physiological health in mice. Here, cell-based and xenograft experiments demonstrated that NOB significantly inhibited the proliferation and migration of TNBC cells in vitro and in vivo. ROR loss- and gain-of-function studies revealed that the NOB-ROR axis has a synergistic effect on the growth of MDA-MB-231 cells. Mechanistically, NOB activates ROR binding to the ROR response element (RRE) of the IκBα promoter and strongly inhibits the nuclear translocation of p65. Transcriptome analysis revealed that cancer and NF-κB signaling pathways are the primary pathways altered by NOB. Consistent with this, induction of p65 expression abolished the NOB effects, suggesting that NF-κB inhibition plays a crucial role in mediating the anti-TNBC effects of NOB. Finally, in vivo xenograft studies in mice demonstrated that NOB, alone or in combination with the chemotherapeutic agent docetaxel, enhanced the antitumor efficacy of mammary fat pad-transplanted TNBC. Together, these studies reveal a mechanism by which ROR-NOB inhibits TNBC by inhibiting NF-κB signaling, suggesting novel preventive and chemotherapeutic strategies for this devastating disease.

Here, the researchers constructed RORA or RORC overexpressing MDA-MB-231 cells (RORA:231 and RORC:231). NOB inhibited cell proliferation in a dose-dependent manner in MDA-MB-231 cells transfected with an empty vector. Compared with the control group, the expression of both RORA and RORC significantly reduced the proliferation of MDA-MB-231 cells (Figure 1A), and NOB further reduced the proliferation of RORA or RORC overexpressing MDA-MB-231 cells. Compared with the control group, the migration rate (Figure 1B) and colony formation rate (Figure 1C) were also significantly reduced in RORA or RORC overexpressing cells. Notably, NOB exhibited a strong effect in these ROR-expressing cells, highlighting the important role played by the NOB-ROR axis in TNBC cells.

Figure 1. Combination of NOB and ROR ectopic expression in MDA-MB-231 cells suppresses cell growth and motility. (Kim E, et al., 2022)