title: Ochratoxin A-induced cell proliferation and tumor promotion in mouse skin by activating the expression of cyclin-D1 and cyclooxygenase-2 through nuclear factor-kappa B and activator protein-1.
abstract: Our prior studies have indicated that ochratoxin A (OTA), a mycotoxin, has skin tumor initiating activity. In the present investigation, skin tumor promoting activity of OTA and the mechanism/(s) involved therein was undertaken. A single topical application of OTA (100 nmol/mouse) caused significant enhancement in short-term markers of skin tumor promotion such as ornithine decarboxylase activity, DNA synthesis, hyperplasia as well as expression of cyclin-D1 and COX-2 in mouse skin. In a two-stage mouse skin tumorigenesis protocol, twice-weekly exposure of OTA (50 nmol/mouse) to 7,12-dimethylbenz[α]anthracene (120 nmol/mouse) initiated mice skin for 24 weeks leads to tumor formation. Further, exposure of primary murine keratinocytes (PMKs) with non-cytotoxic dose of OTA (5.0 µM) caused (i) significant enhancement of DNA synthesis, (ii) enhanced phosphorylation and subsequent activation of epidermal growth factor receptor (EGFR) and its downstream signaling pathways viz Akt, ERK1/2, p38 and JNK mitogen-activated protein kinases (MAPKs), (iii) overexpression of c-jun, c-fos, cyclin-D1 and COX-2 and (iv) increased binding of nuclear factor-kappaB (NF-κB) and AP-1 transcription factors to the promoter region of cyclin-D1 and COX-2 genes. It was also observed that knocking down the messenger RNA expression of NF-κB, c-jun, c-fos, cyclin-D1 and COX-2 results in significant inhibition in OTA-induced PMKs proliferation. These results suggest that OTA has cell proliferative and tumor-promoting potential in mouse skin, which involves EGFR-mediated MAPKs and Akt pathways along with NF-κB and AP-1 transcription factors and that cyclin-D1 and COX-2 are the target genes responsible for tumor-promoting activity of OTA.
authors.affiliation: Food, Drug and Chemical Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Mahatma Gandhi Marg, PO Box 80,  Lucknow 226001, Uttar Pradesh, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Kumar
authors.forename: Shamshad
authors.initials: S
authors.lastname: Alam
authors.forename: Bhushan P
authors.initials: BP
authors.lastname: Chaudhari
authors.forename: Premendra D
authors.initials: PD
authors.lastname: Dwivedi
authors.forename: Swatantra K
authors.initials: SK
authors.lastname: Jain
authors.forename: Kausar M
authors.initials: KM
authors.lastname: Ansari
authors.forename: Mukul
authors.initials: M
authors.lastname: Das
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D002273:Carcinogens / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000235:genetics* / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics* / Q000378:metabolism; D004789:Enzyme Activation; D004817:Epidermis / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D055785:Gene Knockdown Techniques; D006965:Hyperplasia / Q000139:chemically induced / Q000378:metabolism; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D009793:Ochratoxins / Q000494:pharmacology*; D009955:Ornithine Decarboxylase / Q000378:metabolism; D010766:Phosphorylation; D061251:Primary Cell Culture; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012878:Skin Neoplasms / Q000139:chemically induced / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism* / Q000502:physiology; D015533:Transcriptional Activation / Q000187:drug effects
chemical_list: D002273:Carcinogens; C530105:Ccnd1 protein, mouse; D016328:NF-kappa B; D009793:Ochratoxins; D034741:RNA, Small Interfering; D018808:Transcription Factor AP-1; D019938:Cyclin D1; C025589:ochratoxin A; D015127:9,10-Dimethyl-1,2-benzanthracene; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D009955:Ornithine Decarboxylase