Nur77 Activator Induces Proapoptotic Genes and Responses in Colon Cancer Cells Though Nuclear Receptor-Dependent Pathways
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Nerve gro때h factor-induced B (NGFI-B, Nur77) is an orphan nuclear receptor with no known endogenous Iigands , however‘ recent stuclies on a series of methylene -substituted diindolylmethanes (C-DIMs) have identified 1,l-bis(3’ - In dolyl) -l-(phenyl)methane (DIM-C-Ph) and l , l -bis(3’ indolyl)-l-(p-anisyl)methane (DIM-C-pPhOCHa) as Nur77 agonist Nur77 is expressed in several colon cancer cell lines (RKO, SW480, HCT-116, HT-29 and HCT-15) and we a lso observed by irnmunostaining that Nur77 was overexpressed in colon tumors compared to normal colon tIssue DIM-C-Ph and DlM-C-pPhOCH3 decreased survival and induced apoptosis in RKO colon cancer cells and this was accompanied by in ductdion of tumor nec rosis factor-related apoptosis-incluced ligand (TRAlL) protein, The induct ion of a poptosis and TRAlL by DIM-C-pPhOCH3 was significantly inhibited by a small inhibitory RNA for Nur77 (iNur77); however, it was evide nt from RNA in terference studies that DIM-C-pPhOCH3 a1so induced Nur77-independent apoptosis. Analysis o( DIM-C-pPhOCH3-induced gene expression using microarrays idontifiod sovoral proapoptotic genos and analysis by ro verse t ranscriptase PCR in the presence 0 1' absence of iNru77 showed that incluction of prograrnmed cell death gene 1 (PDcm) was Nur77-dependent‘ whereas induction of cystathionase (CSE) and activating transcription factor 3 (ATF3) was Nur77-independent, DIM-C-pPhOCHa (25 mg/kg/day) also inhi bited tumor growth in athymic nude mice bearing RKO cell xenograft, These results demonstrate that Nur77-active C-DIM compounds represent a new class of anti-colon cancer drugs that act through receptor- dependent and - independent pathway