Irsogladine malate up-regulates gap junctional intercellular communication between pancreatic cancer cells via PKA pathway.
BACKGROUND
Gap junctions (GJs) are intercellular channels that aid communication between coupling cells and may play a critical role in cell differentiation and growth. Connexins (Cxs) are structural proteins of GJs. Though several reports have demonstrated that Cx expression decreases in various malignant tumors, a pancreatic cancer cell line, PANC-1, was reported to express Cx43 mRNA. It is known that irsogladine malate (IM) can up-regulate gap junctional intercellular communication (GJIC). We examined the effects of IM on GJ between pancreatic cancer cells (PC cells) and the mechanism of GJ up-regulation.


METHODS
GJIC between PC cells (PANC-1) was evaluated by dye transfer methods. The expression of Cx43 was estimated by Western blot analysis with immunoprecipitation sample and immunohistochemical analysis. Intracellular cAMP level was estimated by enzyme-linked immunoassay.


RESULTS
IM increased cell coupling in a dose-dependent manner (0M-10 ). Western blot analysis of Cx43 revealed that PANC-1 cells expressed Cx43 protein. Treatment with IM was found to move localization of Cx43 immunoreactive spots from the cytoplasm to boundary lesions with neighboring cells, but no major change was seen in the phosphorylation state of Cx43. Intracellular cAMP level was increased by IM. The PKA inhibitor H-89 and adenylyl cyclase inhibitor SQ22536 inhibited the effects of IM.


CONCLUSIONS
These results suggest that IM up-regulates GJIC between PC cells via regulation of the PKA pathway. It also suggests a useful adjuvant of IM to pancreatic cancer therapy.
Kawasaki
Yousuke
Y
First Department of Internal Medicine, Hiroshima University School of Medicine, Hiroshima, Japan. ayanonyk@hiroshima-u.ac.jp
Tsuchida
Akira
A
Sasaki
Tamito
T
Yamasaki
Souichirou
S
Kuwada
Yukio
Y
Murakami
Masateru
M
Chayama
Kazuaki
K
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001692:Biological Transport; D002450:Cell Communication; D002460:Cell Line; D018031:Connexin 43 / Q000378:metabolism; D000242:Cyclic AMP / Q000032:analysis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004285:Dogs; D005456:Fluorescent Dyes / Q000378:metabolism; D017629:Gap Junctions / Q000502:physiology*; D010190:Pancreatic Neoplasms / Q000201:enzymology* / Q000378:metabolism / Q000503:physiopathology*; D015398:Signal Transduction; D014227:Triazines / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D000970:Antineoplastic Agents; D018031:Connexin 43; D005456:Fluorescent Dyes; D014227:Triazines; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C041836:irsogladine