Extracellular matrix inhibits apoptosis and enhances endothelial cell differentiation by a NF kappa B-dependent mechanism

Hormonal and environmental factors that control the growth, differentiation , and regression of the vasculature are of fundamental importance in tumori genesis and in the choice of therapeutic strategies. To test the hypothesis that estradiol (E-2) and basement membrane proteins would affect the survi val of vascular endothelial cells (EC), immortalized human umbilical vein e ndothelial cells (ECV304) were examined for their response to the chemother apeutic drugs taxol and etoposide. ECV cell apoptosis was inhibited by E-2 (taxol only) or attachment to extracellular matrix (ECM) (taxol or etoposid e). E-2 increased ECV growth, while ECM binding resulted in growth arrest a nd differentiation. Apoptosis was associated with decreased levels of Bcl-2 and p21 proteins. E-2 prevented down-regulation of p21 and Bcl-2 induced b y taxol but did not prevent the down-regulation of p21 induced by etoposide , consistent with the failure of E-2 to inhibit etoposide-induced cell deat h. However, ECM prevented p21 and Bcl-2 down-regulation induced by taxol or etoposide. Persistent activation of NF kappa B occurred after attachment o f ECV cells to ECM, suggesting a role in survival or differentiation. I kap pa B alpha levels were not affected by taxol but were reduced by etoposide treatment while I kappa B beta levels did not change with drug treatment. E 2 did not alter the levels of I kappa B alpha or I kappa B beta. Interestin gly, levels of I kappa B alpha and I kappa B beta declined in etoposide-tre ated ECV cells on ECM concomitant with the elevation of NF kappa B, suggest ing that in these cells degradation of I kappa B may be responsible for NF kappa B activation. In agreement with these data, anti-sense NF kappa B tre atment of ECV cells inhibited differentiation on ECM, but did not affect ce ll survival. In conclusion, culture of ECV cells on ECM or treatment with E -2 inhibited apoptosis. NF kappa B activation by ECM was necessary for cell ular differentiation, rather than inhibition, of apoptosis. J. Cell. Bioche m. 73:321-331, 1999. Published 1999 Wiley-Liss, Inc.dagger