Effect of protein kinase C inhibitors on invasiveness of human melanoma clones expressing different levels of protein kinase C isoenzymes.
The involvement of protein kinase C (PKC) in the mechanism of chemotaxis and invasiveness of human melanoma has been studied in 6 clones of 665/2 cell line characterized by a different integrin profile, differentiation grade and in vitro invasive ability. The levels of total protein kinase C activity revealed a direct correlation with the chemotactic and invasive ability of these clones. Protein kinase C inhibitors, sphingosine and staurosporine, reduced chemotaxis and invasiveness of the highly invasive clone 2/60, while 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H7) was ineffective. Immunofluorescence analysis revealed high levels of protein kinase C alpha in clone 2/60, while the less invasive clone 2/21 expressed low levels of protein kinase C alpha and beta, but surprisingly appreciable levels of protein kinase C gamma. Downregulation with phorbol 12-myristate 13-acetate (TPA) did not affect invasiveness of clone 2/60 unless the compound was present during the assay. H7 strongly increased invasiveness of clone 2/21 and was able to reverse the inhibitory effect of TPA on clone 2/60. Preliminary experiments showed higher levels of diacylglycerol in clones with lower protein kinase C, suggesting a constitutive downregulation of the enzyme in low invasive clones. Our results support a role for protein kinase C in the invasion process, but point out the complexity of the mechanism which might involve the proteolytic fragment of the enzyme, protein kinase M.
Mapelli
E
E
Division of Experimental Oncology, Istituto Nazionale Tumori, Milan, Italy.
Banfi
P
P
Sala
E
E
Sensi
M
M
Supino
R
R
Zunino
F
F
Gambetta
R A
RA
D000470:Alkaloids / Q000494:pharmacology; D002465:Cell Movement; D004075:Diglycerides / Q000032:analysis; D006801:Humans; D007527:Isoenzymes / Q000032:analysis / Q000502:physiology*; D008545:Melanoma / Q000201:enzymology* / Q000473:pathology*; D009361:Neoplasm Invasiveness; D011493:Protein Kinase C / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000470:Alkaloids; D004075:Diglycerides; D007527:Isoenzymes; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate