Abstract
The ability of cancer cells to migrate and invade into surrounding tissues is one of the fundamental hallmarks of cancer progression. The process of cancer cell invasion is not well understood leaving a gap in knowledge of potential cancer therapies. Peroxidasin, a peroxidase enzyme secreted to the extracellular matrix, has been found to be upregulated in numerous types of cancers. High expression of peroxidasin has been linked to a more invasive phenotype within melanoma cancer cell lines and our research project aimed to investigate whether this is also the case within breast cancer cell lines. We also investigated whether the modulation of peroxidasin activity and protein expression, using a peroxidasin inhibitor and short interfering RNAs, respectively, affects the ability of breast cancer cells to migrate and invade.
Three breast cancer cell lines representing the different genetically distinct hormone receptor subtypes were chosen, namely the triple negative MDA-MB-231, the hormone receptor positive MCF-7 and the HER2 positive SKBR-3 cell line. Data analysis of peroxidasin expression in a breast cancer patient cohort from The Cancer Genome Atlas showed increased levels of peroxidasin in triple negative and human epidermal growth factor 2 amplified breast cancers compared to estrogen receptor positive. We determined peroxidasin protein expression and established that MDA-MB-231 expressed the highest levels of peroxidasin using a peroxidasin specific ELISA assay and Western blotting. These results are in line with the cancer cohort analysis. MDA-MB-231 also showed the highest migratory and invasive ability of the three cells lines in both 2D and 3D migration and invasion assays, corroborating our hypothesis of high expression of peroxidasin being connected to high invasive ability.
Inhibition of the catalytic activity of peroxidasin using an inhibitor showed no effect on 2D migration, but showed reduced invasion in the 3D invasion assay in all three of the cell lines. The effect of short interfering RNAs, which resulted in reduced peroxidasin protein expression, was also investigated and showed a trend of reduced invasiveness for MDA-MB-231.
Our results confirmed high peroxidasin expression in the breast cancer cell line with the highest invasive potential. Modulation of peroxidasin did show a slight decrease in the invasiveness of the cell lines but this needs to be further explored to determine significance. Our results showed that peroxidasin levels may be indicative of breast cancer invasiveness and may therefore be exploited as a diagnostic, prognostic or therapeutic tool and warrants further investigation.