Nur77 agonists induce proapoptotic genes and responses in colon cancer cells through nuclear receptor-dependent and nuclear receptor-independent pathways.
Nerve growth factor-induced Balpha (NGFI-Balpha, Nur77) is an orphan nuclear receptor with no known endogenous ligands; however, recent studies on a series of methylene-substituted diindolylmethanes (C-DIM) have identified 1,1-bis(3'-indolyl)-1-(phenyl)methane (DIM-C-Ph) and 1,1-bis(3'-indolyl)-1-(p-anisyl)methane (DIM-C-pPhOCH3) as Nur77 agonists. Nur77 is expressed in several colon cancer cell lines (RKO, SW480, HCT-116, HT-29, and HCT-15), and we also observed by immunostaining that Nur77 was overexpressed in colon tumors compared with normal colon tissue. DIM-C-Ph and DIM-C-pPhOCH3 decreased survival and induced apoptosis in RKO colon cancer cells, and this was accompanied by induction of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) protein. The induction of apoptosis and TRAIL by DIM-C-pPhOCH3 was significantly inhibited by a small inhibitory RNA for Nur77 (iNur77); however, it was evident from RNA interference studies that DIM-C-pPhOCH3 also induced Nur77-independent apoptosis. Analysis of DIM-C-pPhOCH3-induced gene expression using microarrays identified several proapoptotic genes, and analysis by reverse transcription-PCR in the presence or absence of iNur77 showed that induction of programmed cell death gene 1 was Nur77 dependent, whereas induction of cystathionase and activating transcription factor 3 was Nur77 independent. DIM-C-pPhOCH3 (25 mg/kg/d) also inhibited tumor growth in athymic nude mice bearing RKO cell xenografts. These results show that Nur77-active C-DIM compounds represent a new class of anti-colon cancer drugs that act through receptor-dependent and receptor-independent pathways.
Cho
Sung Dae
SD
Institute of Biosciences and Technology, Texas A&M University Health Science Center, College Station 77843-4466, USA.
Yoon
Kyungsil
K
Chintharlapalli
Sudhakar
S
Abdelrahim
Maen
M
Lei
Ping
P
Hamilton
Stanley
S
Khan
Shaheen
S
Ramaiah
Shashi K
SK
Safe
Stephen
S
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics*; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D004268:DNA-Binding Proteins / Q000819:agonists* / Q000096:biosynthesis; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D008297:Male; D008697:Methane / Q000031:analogs & derivatives / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists* / Q000096:biosynthesis; D011987:Receptors, Steroid / Q000819:agonists* / Q000096:biosynthesis; D014157:Transcription Factors / Q000819:agonists* / Q000096:biosynthesis; D023041:Xenograft Model Antitumor Assays
D004268:DNA-Binding Proteins; D007211:Indoles; C539821:NR4A1 protein, human; C539818:Nr4a1 protein, mouse; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D014157:Transcription Factors; D008697:Methane