Cyclooxygenase-2 (COX-2) overexpression is found in a wide variety of human cancers, including lung cancer.1–2 Elevated tumor COX-2 expression is associated with increased angiogenesis,3– tumor invasion,4–6 suppression of host immunity,7–8 and promotion of tumor cell resistance to apoptosis.9 To analyze COX-2-dependent gene expression and apoptosis, cell lines constitutively expressing COX-2 complementary DNA in sense and antisense orientations were created by transducing A549 and H157 non-small cell lung cancer (NSCLC) cell lines with retroviral constructs. We find that COX-2 overexpression and its product prostaglandin E2 (PGE2) increase the apoptosis threshold of NSCLC cells and genetic or pharmacologic inhibition of COX-2 sensitizes them to apoptotic signals. The expression of the antiapoptotic protein survivin correlated positively with COX-2 expression in parental, COX-2 sense and antisense cells. Immunohistochemical analysis of human NSCLC resection specimens revealed frequent co-expression of COX-2 and survivin. Survivin ubiquitination was significantly diminished in COX-2 sense and elevated in antisense cells, thus leading to enhanced survivin degradation in COX-2 antisense cells. A similar effect was elicited by exogenous PGE2 treatment of parental NSCLC cells. In contrast to previous studies in other cell types, survivin in NSCLC cells was expressed in a cell cycle-independent manner. Tumor development in SCID mice was assessed by inoculation of equal amounts of control and COX-2 sense or antisense NSCLC cells. Consistent with our in vitro findings, survivin levels were significantly lower in tumors that developed from COX-2 antisense cells and higher in COX-2 sense-derived tumors. Our results support the hypothesis that COX-2 overexpression and PGE2 overproduction inhibit survivin ubiquitination, which leads to its stabilization and prevents proteasomal degradation of survivin in NSCLC cells. Our findings provide evidence for the importance of COX-2 overexpression in the regulation of anti-apoptotic proteins and lung cancer cell survival.