T-Cadherin-Mediated Cell Growth Regulation Involves G₂ Phase Arrest and Requires p21^CIP1/WAF1 Expression

Abstract

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 G₂ 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 ^−/− mouse embryonic fibroblasts. T-cadherin-expressing C6 cell lines exhibited increased p21^CIP1/WAF1, but not p27^Kip1, expression. Lastly, T-cadherin-mediated growth arrest was dependent on p21^CIP1/WAF1 expression and was eliminated in p21^CIP1/WAF1-deficient fibroblasts. Collectively, these observations suggest a novel mechanism of growth regulation for T-cadherin involving p21^CIP1/WAF1 expression and G₂ arrest.

ACKNOWLEDGMENTS

We gratefully appreciate the comments and the technical assistance of Amy L Boyet in The Flow Cytometry Core Facility at Washington University for processing the cell cycle analysis data. We thank Wen Li in our laboratory for technical assistance and Michaela L. Bajenaru, Anthony Apicelli, and Kathy Lee for helpful discussions.

This work was supported by funding from The National Institutes of Health (NS41097 to D.H.G.) and The American Cancer Society (D.H.G.).