Expression of E-cadherin and specific CXCR3 isoforms impact each other in prostate cancer.

BACKGROUND

Carcinoma cells shift between epithelial and mesenchymal phenotypes during cancer progression, as defined by surface presentation of the cell-cell cohesion molecule E-cadherin, affecting dissemination, progression and therapy responsiveness. Concomitant with the loss of E-cadherin during the mesenchymal transition, the predominant receptor isoform for ELR-negative CXC ligands shifts from CXCR3-B to CXCR3-A which turns this classical G-protein coupled receptor from an inhibitor to an activator of cell migration, thus promoting tumor cell invasiveness. We proposed that CXCR3 was not just a coordinately changed receptor but actually a regulator of the cell phenotype.

METHODS

Immunoblotting, immunofluorescence, quantitative real-time PCR and flow cytometry assays investigated the expression of E-cadherin and CXCR3 isoforms. Intrasplenic inoculation of human prostate cancer (PCa) cells with spontaneous metastasis to the liver analyzed E-cadherin and CXCR3-B expression during cancer progression in vivo.

RESULTS

We found reciprocal regulation of E-cadherin and CXCR3 isoforms. E-cadherin surface expression promoted CXCR3-B presentation on the cell membrane, and to a lesser extent increased its mRNA and total protein levels. In turn, forced expression of CXCR3-A reduced E-cadherin expression level, whereas CXCR3-B increased E-cadherin in PCa. Meanwhile, a positive correlation of E-cadherin and CXCR3-B expression was found both in experimental PCa liver micro-metastases and patients' tissue.

CONCLUSIONS

CXCR3-B and E-cadherin positively correlated in vitro and in vivo in PCa cells and liver metastases, whereas CXCR3-A negatively regulated E-cadherin expression. These results suggest that CXCR3 isoforms may play important roles in cancer progression and dissemination via diametrically regulating tumor's phenotype.