title: Nimbolide, a limonoid triterpene, inhibits growth of human colorectal cancer xenografts by suppressing the proinflammatory microenvironment.
abstract: OBJECTIVE
  Extensive research over the past decade has revealed that the proinflammatory microenvironment plays a critical role in the development of colorectal cancer. Whether nimbolide, a limonoid triterpene, can inhibit the growth of colorectal cancer was investigated in the present study.
  
  
  METHODS
  The effect of nimbolide on proliferation of colorectal cancer cell lines was examined by MTT assay, apoptosis by caspase activation and poly-ADP ribose polymerase cleavage, NF-κB activation by DNA-binding assay, and protein expression by Western blotting. The effect of nimbolide on the tumor growth in vivo was examined in colorectal cancer xenografts in a nude mouse model.
  
  
  RESULTS
  Nimbolide inhibited proliferation, induced apoptosis, and suppressed NF-κB activation and NF-κB-regulated tumorigenic proteins in colorectal cancer cells. The suppression of NF-κB activation by nimbolide was caused by sequential inhibition of IκB kinase (IKK) activation, IκBα phosphorylation, and p65 nuclear translocation. Furthermore, the effect of nimbolide on IKK activity was found to be direct. In vivo, nimbolide (at 5 and 20 mg/kg body weight), injected intraperitoneally after tumor inoculation, significantly decreased the volume of colorectal cancer xenografts. The limonoid-treated xenografts exhibited significant downregulation in the expression of proteins involved in tumor cell survival (Bcl-2, Bcl-xL, c-IAP-1, survivin, and Mcl-1), proliferation (c-Myc and cyclin D1), invasion (MMP-9, ICAM-1), metastasis (CXCR4), and angiogenesis (VEGF). The limonoid was found to be bioavailable in the blood plasma and tumor tissues of treated mice.
  
  
  CONCLUSIONS
  Our studies provide evidence that nimbolide can suppress the growth of human colorectal cancer through modulation of the proinflammatory microenvironment.
authors.affiliation: Cytokine Research Laboratory, Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Subash C
authors.initials: SC
authors.lastname: Gupta
authors.forename: Sahdeo
authors.initials: S
authors.lastname: Prasad
authors.forename: Dhanya R
authors.initials: DR
authors.lastname: Sethumadhavan
authors.forename: Mangalam S
authors.initials: MS
authors.lastname: Nair
authors.forename: Yin-Yuan
authors.initials: YY
authors.lastname: Mo
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Aggarwal
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D004195:Disease Models, Animal; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D036701:Limonins / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D050796:STAT3 Transcription Factor / Q000378:metabolism; D047368:Tumor Burden / Q000187:drug effects; D059016:Tumor Microenvironment / Q000187:drug effects* / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D036701:Limonins; D016328:NF-kappa B; D050796:STAT3 Transcription Factor; C042198:nimbolide