Reduced expression of both classical and
desmosomal cadherins has been associated with different types of
carcinomas, including
prostate cancer. This study aims to provide a comprehensive view of the role and regulation of cell-cell adhesion in
prostate cancer aggressiveness by examining the functional implications of both
E-cadherin and
Desmoglein 2 (DSG2).
E-cadherin expression was first examined using immunofluorescence in 50 normal prostate tissues and in a cohort of 414
prostate cancer patients. Correlation and survival analyses were performed to assess its clinical significance. In primary
prostate cancer patients, reduced expression of both
E-cadherin and DSG2 is significantly associated with an earlier biochemical recurrence. Transgenic DU145
E-cadherin knockdown and constitutively active AKT overexpression lines were generated. Functional implications of such genetic alterations were analyzed in vitro and in vivo, the latter by using
tumorigenesis as well as extravasation and metastatic
tumor formation assays. We observed that loss of
E-cadherin leads to impaired primary and metastatic
tumor formation in vivo, suggesting a
tumor promoter role for
E-cadherin in addition to its known role as a
tumor suppressor. Activation of AKT leads to a significant reduction in
E-cadherin expression and nuclear localization of Snail, suggesting a role for the PI3K/AKT signaling pathway in the transient repression of
E-cadherin. This reduced expression may be regulated by separate mechanisms as neither the loss of
E-cadherin nor activation of AKT significantly affected DSG2 expression. In conclusion, these findings illustrate the critical role of cell-cell adhesion in the progression to aggressive
prostate cancer, through regulation by the PI3K pathway.