trans-10,cis-12 conjugated linoleic acid inhibits the G1-S cell cycle progression in DU145 human prostate carcinoma cells.
Conjugated linoleic acid (CLA) is a group of positional and geometric isomers of linoleic acid, and has evidenced anti-cancer activities in experimental animal cancer models and in vitro studies. The two predominant isomers of CLA are cis-9,trans-11 CLA (c9t11) and trans-10,cis-12 CLA (t10c12). The present study was performed to study the effect of the individual CLA isomers on DU145 cell growth. The cells were incubated in serum-free medium with different concentrations of the fatty acids. Treatment of cells with t10c12 (at 2.5-10 micromol/L) resulted in a dose-dependent reduction in the numbers of viable cells, whereas c9t11 CLA at a concentration of 5 micromol/L slightly increased viable cell numbers at 3 days (P < .05). DNA flow cytometric analysis revealed that the treatment of DU145 cells with t10c12 for 24 hours induced a small but significant increase in the number of cells in the G1 phase, accompanied by a complementary decrease in cells in the S phase. c9t, however, had no effect on cell cycle progression. To determine the molecular mechanisms underlying t10c12-induced G1 arrest, the levels of cell cycle regulatory proteins were estimated by western blot analyses. t10c12 induced a marked increase in p21(CIP1/WAF1) protein levels in a dose-dependent manner. p27(KIP1) was not affected by t10c12. t10c12 moderately decreased cyclin A and cyclin D1 protein levels (P > .05). However, t10c12 did not affect the expression of cyclin-dependent kinase (CDK) 2, CDK4, or cyclin E. t10c12 increased p21(CIP1/WAF1) bound to CDK2 and attenuated CDK2 activity. These results indicate that t10c12-induced p21(CIP1/WAF1) binds to CDK, and inhibits the activity of this enzyme, which results in the observed decrease in the G1-S progression in DU145 cells.
Kim
Eun Ji
EJ
Silver Biotechnology Research Center, Hallym University, Chuncheon, Republic of Korea.
Shin
Hyun-Kyung
HK
Cho
Jin Sun
JS
Lee
Sang Kon
SK
Won
Moo Ho
MH
Kim
Jong Woo
JW
Park
Jung Han Yoon
JH
D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000032:analysis; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000032:analysis; D016193:G1 Phase / Q000187:drug effects*; D006801:Humans; D044243:Linoleic Acids, Conjugated / Q000494:pharmacology*; D008297:Male; D011471:Prostatic Neoplasms / Q000737:chemistry / Q000201:enzymology / Q000473:pathology*; D016196:S Phase / Q000187:drug effects*
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D044243:Linoleic Acids, Conjugated; C503589:cis-9, trans-11-conjugated linoleic acid; C496197:trans-10,cis-12-conjugated linoleic acid; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051357:Cyclin-Dependent Kinase 2