The effect of CLAs on the expression of PKC isoforms and cell viability in breast cancer cell lines.
Crabb-Wyke, Rosemary H.
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Breast tumours make up 15% of the total cancer burden in the UK and around 8% of the total number of cancer related deaths. Protein kinase C (PKC) isoforms have been shown to be strongly modulated in many androgen sensitive tumour cell lines. Increased expression of some PKC isoforms has also been linked to immortality in many cancer cell lines. Conjugated linoleic acids(CLAs) are naturally occurring positional and geometric isomers of the fatty acid linoleic acid (LA). CLAs have been shown to reduce growth and increase apoptosis in breast cancer cells, and to alter their PKC expression both in animal models and in various human cell lines. We investigated the effect of CLA on the oestrogen sensitive MCF-7 cell line, and the oestrogen insensitive MDA-MB-231 cell line for 24 hours at two different concentrations of CLA (25Mu M and 50Mu M, optimum concentrations, previously shown in our lab). We measured the variations of three PKC isoforms (Alpha, Delta, and Iota) in the cytosol (inactive form) and the membrane (active form), as well as the mRNA expression of each in MCF-7 after 12 hours of treatment at 50Mu M concentrations. The activation of PKC was measured by Western Blot analysis, using PKC isoform specific antibodies and Beta-actin, or Claudin-3 as the housekeeping protein. Results indicate that the CLA isoforms used (the 911, 1012 and a 50/50 mix of the two) cause a decrease in cell viability in both cell lines. It was observed that the activation of PKC Alpha was decreased in MCF-7 cells, compared to the control, while the activation of PKC Delta and Iota was increased. In the MDA-MB-231 cell line PKC Iota activation was decreased at both concentrations, while PKC Alpha and Delta activation showed no particular pattern. mRNA expression of PKC Alpha and Iota was generally decreased after treatment with 50Mu M of CLA, while PKC Delta mRNA expression increased. These effects are similar (but not identical) to the ones seen in prostate cancer cell lines (LNCaP and PC3), which have been previously reported by our lab. It appears that CLA supplementation influences PKC isoform mRNA expression and protein activation in breast cancer cells. While the mRNA expression occurs in a pattern which appears to fit with that found in previous research the protein activation does not follow the trends suggested by work in other cell lines. It appears that the expression and activation of PKC isoforms are not just influenced by the interactions between CLA isoforms and the PKC genes in breast cancer cells.