PMID: 25750277Mar 10, 2015Paper

Ectopic expression of protein kinase C-β sensitizes head and neck squamous cell carcinoma to diterpene esters

Anticancer Research
Ryan A AdamsGlen M Boyle

Abstract

The objective of this study was to examine the effect of specific Protein kinase C (PKC) isoform re-expression in solid malignancies, particularly head and neck squamous cell carcinoma cell lines, and the impact this may have on treatment with known activators of PKC. The constitutive expression of PKC isoforms were determined in six head and neck squamous cell carcinoma (SCC) cell lines. Cytotoxicity of the prototypic phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) and the novel diterpene ester PEP005 was established. Viral transduction to re-express PKCβ isoforms in two of these cell lines was performed, and its effect on the sensitivity to the compounds was quantified. Tongue and hypopharyngeal SCC cell lines were resistant to both TPA and PEP005, with the concentration required to inhibit growth by 50% (IC50) being >1,000 ng/ml. CAL-27 (tongue SCC) and FaDu (hypopharyngeal SCC) cell lines re-expressing PKCβI and -βII isoforms demonstrated IC50 of 1-5 ng/ml with TPA or PEP005. Re-expression of PKCβ in head and neck SCC cell lines leads to cells one thousand-times more sensitive to the cytotoxic effects of phorbol or diterpene esters in culture. This highlights the importance of the isoform in tumor progression and ...Continue Reading

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