P-cadherin overexpression occurs in about 30% of all
breast carcinomas, being a poor prognostic factor for
breast cancer patients. In a cellular background of wild-type
E-cadherin, we have previously shown that its expression promotes invasion, motility and migration of
breast cancer cells due to the induced secretion of
metalloproteases (
MMPs) to the extracellular medium and to the concomitant shedding of a pro-invasive soluble form of this
protein (sP-cad).
Azurin is secreted by Pseudomonas aeruginosa and induces in vitro and in vivo cytotoxicity after its preferential penetration in human
cancer cells relative to normal cells. Three different
breast cancer cell lines, MCF-7/AZ.Mock, MCF-7/AZ.Pcad and SUM149 were treated with sub-killing doses of
azurin. Invasion of these cells was measured using
Matrigel Invasion Assays and MTT assays were performed to determine cell viability upon treatment and the effects on
cadherins expression was determined by Western blot and Immunofluorescence.
Gelatin Zymography was used to determine activity of MMP2 in the
conditioned media of
azurin treated and untreated cells and the phosphorylation levels of
intracellular signaling proteins were determined by Western blot. The invasive phenotype of these
breast cancer cells was significantly reduced by
azurin.
Azurin (50-100 µM) also caused a specific decrease on
P-cadherin protein levels from 30-50% in MCF-7/AZ.Pcad and SUM149
breast cancer cell lines, but the levels of
E-cadherin remain unaltered. More, the levels of sP-cad and the activity of MMP2 were reduced in the extracellular media of
azurin treated cells and we also observed a decrease in the phosphorylation levels of both FAK and Src
proteins. Our data show that
azurin specifically targets
P-cadherin, not
E-cadherin, abrogating
P-cadherin-mediated invasive effects and signaling. Therefore,
azurin could possibly be considered a therapeutic tool to treat poor-prognosis
breast carcinomas overexpressing
P-cadherin in a wild type
E-cadherin context.