Tobacco-specific carcinogen enhances colon cancer cell migration through alpha7-nicotinic acetylcholine receptor.
OBJECTIVE
To study the mechanism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-enhanced migration of colon cancer cells.


BACKGROUND
Long-term cigarette smoking increases the risk of colorectal cancer mortality. Tobacco-specific carcinogen, NNK, was reported to increase DNA synthesis of colon cancer cells. Since metastasis is the major cause of cancer death, the influence of NNK on the migration of colon cancer cells remains to be determined.


METHODS
Receptor for NNK in colon cancer cells was identified by polymerase chain reaction (PCR) and real-time PCR. The influence of NNK on migration of colon cancer cells was evaluated by transwell and wound-healing assay. Receptor-mediated migration was studied by both inhibitor and small interfering RNA.


RESULTS
alpha7 nicotinic acetylcholine receptor, alpha7-nAChR, was identified in 2 colon cancer cell lines, HT29 and DLD-1. NNK enhanced HT29 cell migration in both transwell and wound-healing assays. NNK also enhanced DLD-1 cell migration in dose dependent manner. We used inhibitor and siRNA to demonstrate that alpha7-nAChR mediated NNK-enhanced colon cancer cell migration and downregulation of E-cadherin were involved in NNK-enhanced migration of colon cancer cells. Furthermore, Snail and ZEB1, 2 major transcription repressors of E-cadherin in colon cancers, were induced by NNK treatment.


CONCLUSIONS
Tobacco specific carcinogen, NNK, enhanced colon cancer metastasis through alpha7-nAChR and E-cadherin--one of the hallmarks of epithelial mesenchymal transition--and its transcription repressors. Therefore, smoking should be avoided in the patients with colorectal cancer.
Wei
Po-Li
PL
Graduate Institute of Clinical Medicine, College of Medicine, School of Medicine, Taipei Medical University and Hospital, Taipei, Taiwan.
Chang
Yu-Jia
YJ
Ho
Yuan-Soon
YS
Lee
Chia-Hwa
CH
Yang
Yi-Yuan
YY
An
Jane
J
Lin
Shyr-Yi
SY
D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D015820:Cadherins / Q000378:metabolism; D002273:Carcinogens / Q000494:pharmacology*; D018929:Cell Culture Techniques; D002465:Cell Movement / Q000187:drug effects; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology*; D019073:HT29 Cells / Q000187:drug effects; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D009602:Nitrosamines / Q000494:pharmacology*; D011978:Receptors, Nicotinic / Q000502:physiology*; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000378:metabolism; D000071799:Zinc Finger E-box-Binding Homeobox 1; D064569:alpha7 Nicotinic Acetylcholine Receptor
D015820:Cadherins; D002273:Carcinogens; C579167:Chrna7 protein, human; D018398:Homeodomain Proteins; D009602:Nitrosamines; D011978:Receptors, Nicotinic; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; C486307:ZEB1 protein, human; D000071799:Zinc Finger E-box-Binding Homeobox 1; D064569:alpha7 Nicotinic Acetylcholine Receptor; C016583:4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone