5,5'-Dibromo-bis(3'-indolyl)methane induces Kruppel-like factor 4 and p21 in colon cancer cells.
Bis(3'-indolyl)methane (DIM) is a metabolite of the phytochemical indole-3-carbinol, and both compounds exhibit a broad spectrum of anticancer activities. We have developed a series of synthetic symmetrical ring-substituted DIM analogues, including 5,5'-dibromoDIM, which are more potent than DIM as inhibitors of cancer cell and tumor growth. In colon cancer cells, 5,5'-dibromoDIM decreased cell proliferation and inhibited G(0)-G(1)- to S-phase progression, and this was accompanied by induction of the cyclin-dependent kinase inhibitor p21 in HT-29 and RKO colon cancer cells. Mechanistic studies showed that induction of p21 in both RKO (p53 wild-type) and HT-29 (p53 mutant) cells by 5,5'-dibromoDIM was Krüppel-like factor 4 (KLF4) dependent, and induction of p53 in RKO cells was also KLF4 dependent. Analysis of the p21 promoter in p53-dependent RKO cells showed that 5,5'-dibromoDIM activated p21 gene expression through the proximal GC-rich sites 1 and 2, and chromatin immunoprecipitation assays showed that KLF4 and p53 bound to this region of the promoter, whereas in HT-29 cells unidentified upstream cis-elements were required for induction of p21. 5,5'-DibromoDIM (30 mg/kg/d) also inhibited tumor growth and induced p21 in athymic nude mice bearing RKO cells as xenografts, showing that ring-substituted DIM such as 5,5'-dibromoDIM represent a novel class of mechanism-based drugs for clinical treatment of colon cancer.
Cho
Sung Dae
SD
Institute of Biosciences and Technology, Texas A&M University Health Science Center, College Station, TX 77843-4466, USA.
Chintharlapalli
Sudhakar
S
Abdelrahim
Maen
M
Papineni
Sabitha
S
Liu
Shengxi
S
Guo
Jingjing
J
Lei
Ping
P
Abudayyeh
Ala
A
Safe
Stephen
S
D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
C512019:5,5'-dibromo-1,1-bis(3'-indolyl)methane; D050759:Cyclin-Dependent Kinase Inhibitor p21; D007211:Indoles; C000715467:KLF4 protein, human; C000715468:Klf4 protein, mouse; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D016159:Tumor Suppressor Protein p53