PPARgamma is involved in mesalazine-mediated induction of apoptosis and inhibition of cell growth in colon cancer cells.
OBJECTIVE
Mesalazine has been identified as a candidate chemopreventive agent in colon cancer prophylaxis because of its pro-apoptotic and anti-proliferative effects. However, the precise mechanisms of action are not entirely understood. The aim of our study was to investigate the involvement of peroxisome proliferator-activated receptor gamma (PPARgamma) in mesalazine's anticarcinogenic actions in colorectal cancer cells.


METHODS
The effects of mesalazine on cell cycle distribution, cell count, proliferation and caspase-mediated apoptosis were examined in Caco-2, HT-29 and HCT-116 cells used as wild-type, dominant-negative PPARgamma mutant and empty vector cultures. We focused on caspase-3 activity, cleavage of poly(ADP-ribose) polymerase (PARP), caspase-8 and caspase-9, as well as on expression of survivin, X-linked inhibitor of apoptosis (Xiap), phosphatase and tensin homolog deleted from chromosome ten (PTEN) and c-Myc. Techniques employed included transfection assays, immunoblotting, flow cytometry analysis, colorimetric and fluorometric assays.


RESULTS
Mesalazine caused a time- and dose-dependent decrease in both cell growth and proliferation. Growth inhibition was accompanied by a G1/G0 arrest, a significant increase in PTEN, caspase-3 activity, cleavage of PARP and caspase-8, whereas the expressions of Xiap, survivin and c-Myc were decreased simultaneously. Cleavage of caspase-9 was not observed. Moreover, PPARgamma expression and activity were elevated. The growth-inhibitory effect of mesalazine was partially reduced in dominant-negative PPARgamma mutant cells, whereas the expression of c-Myc was not affected. Mesalazine-mediated increased caspase-3 activity, the expression of PTEN, cleavage of PARP and caspase-8 as well as reduced levels of survivin and Xiap were completely abolished in the PPARgamma mutant cell lines.


CONCLUSIONS
This study clearly demonstrates that mesalazine-mediated pro-apoptotic and anti-proliferative actions are regulated via PPARgamma-dependent and -independent pathways in colonocytes.
First Department of Medicine-ZAFES, Johann Wolfgang Goethe-University Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany. m.schwab@med.uni-frankfurt.de
Markus
M
Schwab
Veerle
V
Reynders
Stefan
S
Loitsch
Yogesh M
YM
Shastri
Dieter
D
Steinhilber
Oliver
O
Schröder
Jürgen
J
Stein
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D018938:Caco-2 Cells; D053148:Caspase 3 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D053181:Caspase 8 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D048708:Cell Growth Processes / Q000187:drug effects / Q000502:physiology; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015536:Down-Regulation / Q000187:drug effects; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000096:biosynthesis / Q000235:genetics; D019804:Mesalamine / Q000494:pharmacology*; D047495:PPAR gamma / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000096:biosynthesis / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction; D015854:Up-Regulation / Q000187:drug effects
D051034:Inhibitor of Apoptosis Proteins; C489427:MYC protein, human; D047495:PPAR gamma; D016271:Proto-Oncogene Proteins c-myc; D019804:Mesalamine; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D053148:Caspase 3; D053181:Caspase 8