T-Cadherin-Mediated Cell Growth Regulation Involves G[sub 2] Phase Arrest and Requires p21[sup CIP1/WAF1] Expression.

Members of the cadherin family have been implicated as growth regulators in multiple tumor types. Based on recent studies from our laboratory implicating T-cadherin expression in mouse brain tumorigenesis, we examined the role of T-cadherin in astrocytoma growth regulation. In this report, we show that T-cadherin expression increased during primary astrocyte physiologic growth arrest in response to contact inhibition and serum starvation in vitro, suggesting a function for T-cadherin in astrocyte growth regulation. We further demonstrate that transient and stable reexpression of T-cadherin in deficient C6 glioma cell lines results in growth suppression. In addition, T-cadherin-expressing C6 cell lines demonstrated increased homophilic cell aggregation, increased cell attachment to fibronectin, and decreased cell motility. Cell cycle flow cytometry demonstrated that T-cadherin reexpression resulted in G[sub 2] phase arrest, which was confirmed by mitotic index analysis. This growth arrest was p53 independent, as T-cadherin could still mediate growth suppression in p53[sup -/-] mouse embryonic fibroblasts. T-cadherin-expressing C6 cell lines exhibited increased p21[sup CIP1/WAF1], but not p27[sup Kip1], expression. Lastly, T-cadherin-mediated growth arrest was dependent on p21[sup CIP1/WAF1] expression and was eliminated in p21[sup CIP1/WAF1]-deficient fibroblasts. Collectively, these observations suggest a novel mechanism of growth regulation for T-cadherin involving p21[sup CIP1/WAF1] expression and G[sub 2] arrest. [ABSTRACT FROM AUTHOR]