Tumor necrosis factor-alpha stimulates attachment of small cell lung carcinoma to endothelial cells

Tumor cell attachment to endothelial cells (ECs) is an important step in th e metastasis of small cell lung carcinoma (SCLC). Tumor necrosis factor-or (TNF-a) stimulation of ECs increases the attachment of some malignant cell types to ECs by affecting the expression of cell adhesion molecules (CAMs), Similarly, the inhibition of EC protein kinase C (PKC) and tyrosine kinase (TK) pathways modulates TNF-alpha-mediated effects on CAM expression. We h ypothesized that TNF-alpha would increase SCLC attachment to ECs by affecti ng CAM expression through activation of PKC and TK pathways. To test this h ypothesis, human umbilical vein endothelial cells (HUVECs) were stimulated with TNF-alpha (0 to 500 U/mL) for variable time periods (1 to 24 hours), a nd the attachment of H82 cells (an SCLC cell line) to the HUVECs was quanti fied. TNF-alpha stimulation of the HUVECs increased H82 attachment from 28. 1% +/- 1.6% to 48.8% +/- 1.7% (P < .05). Preincubation of HUVECs with the P KC inhibitors bis-indolylmaleimide (BIN) or calphostin C or the TK inhibito rs genistein or herbimycin A (HMA) blocked the TNF-alpha-induced increase i n H82 cell attachment. The addition of antibodies to vitronectin (Vn) or be ta(1)-integrin to TNF-alpha-activated HUVECs before the addition of the H82 cells also significantly decreased H82 attachment, whereas the addition of antibodies to E-selectin, P-selectin, vascular cell adhesion molecule (VCA M), intercellular adhesion molecule (ICAM), neural cell adhesion molecule ( NCAM), sialyl-Lewis(x), fibronectin (Fn), alpha(v)-integrin, alpha(3)-integ rin, alpha(4)-integrin, or alpha(5)-integrin had no effect on SCLC attachme nt. In summary, the TNF-alpha-mediated increase in SCLC attachment to ECs a ppears to be mediated by the activation of EC PKC and TK pathways as well a s through effects on the function or expression of EC Vn and beta(1) integr in.