Diacylglycerols and the protein kinase inhibitor H-7 suppress cell polarity and locomotion of Walker 256 carcinosarcoma cells.
We show that diacylglycerols, like phorbol myristate acetate (PMA), suppress cell polarity and locomotor activity of Walker carcinosarcoma cells in a dose-dependent fashion in vitro. OAG and diC8 show significant activity at concentrations above 3 x 10(-5) M. The inhibitory effect on locomotion is due to a reduction in the proportion of locomoting cells rather than gradual lowering of the speed of individual cells. Measurement of protein kinase C (PKC) activity in isolated fractions showed a substantial reduction of the total cellular PKC activity and of the activity in the cytosolic fraction following incubation of cells with 10(-8) M PMA for 30 min. In contrast, the total and relative PKC activity associated with the membrane fraction was increased by PMA. The effect of H-7, an inhibitor of PKC as well as of cAMP-dependent kinase, has been tested. H-7 suppressed cell polarity of "unstimulated" control cells (ID50 = 6.5 microM H-7), colchicine-stimulated cells (ID50 = 92 microM H-7) or cells treated with both PMA and colchicine (ID50 = 15 microM H-7), in a dose-dependent fashion. The locomotor activity of the cells was also suppressed. LTB4 had no clearcut activity in this system. Our findings suggest that diacylglycerols and H-7 are of interest as physiological or pharmacological stop signals for tumor-cell locomotion. Contrary to our expectations, PMA and diacylglycerols vs. H-7 did not produce opposing or antagonistic effects on cell polarity and locomotion. This similarity may be due to down-regulation of PKC by PMA and inhibition of PKC by H-7. However, the mechanisms underlying these novel effects of diacylglycerols and of H-7 on cell polarity and locomotion may be even more complex; they require further studies.
Keller
H U
HU
Institute of Pathology, University of Bern, Switzerland.
Zimmermann
A
A
Niggli
V
V
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D002279:Carcinoma 256, Walker / Q000473:pathology*; D002451:Cell Compartmentation / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects*; D003078:Colchicine / Q000494:pharmacology; D004075:Diglycerides / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005989:Glycerides / Q000494:pharmacology*; D007546:Isoquinolines / Q000494:pharmacology*; D007975:Leukotriene B4 / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D004075:Diglycerides; D005989:Glycerides; D007546:Isoquinolines; D010879:Piperazines; D007975:Leukotriene B4; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D003078:Colchicine