Curcumin, a yellow component of turmeric or curry powder, has been demonstrated to exhibit anti-carcinogenic effects in vitro, in vivo, and in human clinical trials. One of its molecular targets is protein kinase C (PKC) which has been reported to play essential roles in apoptosis, cell proliferation, and carcinogenesis. In this study, PKC mRNA expression was significantly inhibited in curcumin-treated human hepatocellular carcinoma (HCC) Hep 3B cells identified using a kinase cDNA microarray. Furthermore, curcumin decreased total protein expression of all PKCs in a time-related manner by immunoblotting of whole cell lysates, nuclear, membrane, and cytosolic fractions. In cytosolic fraction, the expression of PKC-α was totally inhibited by curcumin. In contrast, the expression levels of PKC-ζ and -μ were dramatically increased. Increases in expression of PKC-δ and PKC-ζ in the membrane and nucleus, and PKC-ι in the membrane were detected. In summary, the changes in expression and distribution of subcellular PKC isoforms in curcumin-treated Hep 3B cells suggest possible PKC-associated anti-tumor mechanisms of curcumin and provide alternative therapies for human HCC.
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