Cigarette smoke components inhibited intercellular communication and differentiation in human pancreatic ductal epithelial cells.
Smoking is a well-documented risk factor for the development of pancreatic adenocarcinoma. Although the most abundant polycyclic aromatic hydrocarbons (PAHs) in cigarette smoke are methylated anthracenes and phenanthrenes, the epigenetic toxicity of these compounds has not been extensively studied. We previously showed that methylanthracenes, which possess a bay-like structure, affect epigenetic events such as an induced release of arachidonic acid, inhibition of gap junctional intercellular communication (GJIC) and induction of mitogen-activated protein kinases in a pluripotent rat liver epithelial stem cell line. Anthracenes with no bay-like structures were inactive. These biological effects are all molecular events associated with the promotional phase of cancer. A human immortalized, nontumorigenic pancreatic ductal epithelial cell line, H6c7, was examined to study the epigenetic toxicity of PAHs related to pancreatic cancer by using scrape-loading dye transfer, immunostaining, RT-PCR and telomerase assay methods. H6c7 cells were GJIC-incompetent and exhibited high telomerase activity when grown in growth factor and hormone-supplemented medium. In the presence of the cAMP elevating drugs (forskolin and IBMX) the cells became GJIC competent and expressed connexins. Telomerase activity was also decreased by cAMP elevating drug treatment. After induction of cAMP, 1-methylanthracene with bay-like structures inhibited GJIC, whereas the 2-methylanthracene lacking a bay-like structure had no effect on GJIC. Telomerase activity remained high in 1-methylanthracene treatment but not with 2-methylanthracene. These results indicate that a prominent component of cigarette smoke, namely methylanthracenes with distinct structural configurations, could be a potential etiological agent contributing to the epigenetic events of pancreatic cancer.
Tai
Mei-Hui
MH
Department of Physiology, Michigan State University, East Lansing, MI, USA. taimeihu@msu.edu
Upham
Brad L
BL
Olson
Lawrence Karl
LK
Tsao
Ming-Sound
MS
Reed
Donald N
DN
Trosko
James E
JE
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000873:Anthracenes / Q000633:toxicity*; D002450:Cell Communication / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D018031:Connexin 43 / Q000032:analysis / Q000235:genetics; D017630:Connexins / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects; D017629:Gap Junctions / Q000187:drug effects; D006801:Humans; D010183:Pancreatic Ducts / Q000166:cytology / Q000187:drug effects*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012906:Smoke / Q000009:adverse effects*; D019098:Telomerase / Q000378:metabolism; D014026:Nicotiana / Q000009:adverse effects*; D000097004:Gap Junction delta-2 Protein
D015056:1-Methyl-3-isobutylxanthine; D000873:Anthracenes; D005576:Colforsin; D018031:Connexin 43; D017630:Connexins; D012906:Smoke; D019098:Telomerase; D000097004:Gap Junction delta-2 Protein; C051246:1-methylanthracene; C051247:2-methylanthracene