Protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinases, plays a cardinal role in malignancy (1 -5 ). PKC isozymes can be categorized into three groups: Group A or conventional (c) PKC: α, βI, βII, and γ; Group B or novel (n) PKC: δ, ε, η, θ, and �, and Group C or atypical (a) PKC: ζ and λ (ι) (1 ,3 ,4 ). Whereas cPKCs require Ca2+ and diacylglycerol (DAG) phorbol esters for their activities, nPKCs and aPKCs are Ca2+ -independent. aPKCs are also insensitive to diacylglycerol and phorbol esters (1 ,3 ,4 ).
