To investigate a putative involvement of
protein kinase C (PKC)
isoforms in supporting
neuroblastoma cell proliferation, SK-N-BE(2)
neuroblastoma cells were transfected with expression vectors coding for the C2 and V5 regions from different PKC
isoforms. These structures have been suggested to inhibit the activity of their corresponding PKC
isoform. The PKC fragments were fused to
enhanced green fluorescent protein to facilitate the detection of transfected cells. Expression of the C2 domain from a classical PKC
isoform (PKCalpha), but not of C2 domains from novel PKCdelta or PKCepsilon, suppressed the number of
neuroblastoma cells positive for
cyclin A and
bromodeoxyuridine incorporation. This indicates a role for a classical
isoform in regulating proliferation of these cells. Among the V5 fragments from PKCalpha, PKCbetaI, and PKCbetaII, the PKCbetaI V5 had the most suppressive effect on proliferation markers, and this fragment also displaced PKCbetaI from the nucleus. Furthermore, a PKCbeta-specific inhibitor,
LY379196, suppressed the
phorbol ester- and serum-supported growth of
neuroblastoma cells. There was a marked enhancement by
LY379196 of the growth-suppressive and/or cytotoxic effects of
paclitaxel and
vincristine. These results indicate that PKCbetaI has a positive effect on the growth and proliferation of
neuroblastoma cells and demonstrate that inhibition of PKCbeta may be used to enhance the effect of microtubule-interacting
anticancer agents on
neuroblastoma cells.