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 (
DSG
2). 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
DSG
2 is significantly associated with an earlier biochemical recurrence. Transgenic
DU
145 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
PI
3K/
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
DSG
2 expression. In conclusion, these findings illustrate the critical role of cell–cell adhesion in the progression to aggressive prostate cancer, through regulation by the
PI
3K pathway.