Previous studies have demonstrated that exposure to polycyclic aromatic hydrocarbons (PAHs) and its derivatives is associated with an increased risk of skin cancers, and the carcinogenic effect of PAHs is thought to involve both tumor initiation and promotion. Whereas PAH tumor initiation is well characterized, the mechanisms involved in the tumor promotion of PAHs remain elusive. In the present study, we investigated the effects of PAHs on vascular endothelial growth factor 6 -8). 5-MCDE has also been found to be a strong complete carcinogen (9 -11). Therefore, PHAs are important compounds in the etiology of human cancers. Carcinogenesis is a multistage process that consists of initiation, promotion, and progression (13). Initiation is a rapid and irreversible course, whereas promotion is a long term process requiring chronic exposure to a certain compound with tumor promotion activities (14). It is very likely that PAHs contribute to carcinogenesis through involvement at these multiple stages (15, 16). The mutagenic effects of PAHs, which are responsible for tumor initiation, have been extensively documented (5, 9 -12). However, their tumor promotion effects, which are mainly mediated by activation of transcription factors, are not well understood. It is thought that the rate-limiting steps in multistage carcinogenesis occur during tumor promotion and tumor progression. Thus, the identification of signaling pathways involved in PAH tumor promotion is not only essential for understanding the tumorigenesis of PAH compounds, but also in providing useful information for tumor chemoprevention. So it is practically important to compare among the parental PAHs, their derivatives as well as their analogs, the potential effects on various signaling pathways and downstream target genes. Because vascular endothelial growth factor (VEGF) is one of the key growth factors involved in carcinogenesis, we here investigate the effects of subgroups of PAHs, including B[a]P and its derivative B[a]PDE, 5-MCDE, and its analog CDE, on VEGF induction, as well as the signaling pathways leading to this induction. * This work was supported in part by Grants CA112557, CA103180, and CA094964 from the NCI, National Institutes of Health and Grants ES012451, ES000260, and ES010344 from the NIEHS, National Institutes of Health. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. -7,8-diol-9,10-epoxide; CDE, chrysene-1,2-diol-3,4-epoxide; 5-MCDE, (Ϯ)-anti-5-methylchrysene-1,2-diol-3,4-epoxide; FBS, fetal bovine serum; MEM, Eagle's minimal essential medium; PI-3K, phosphatidylinositol 3-kinase; EMSA, electrophoretic mobility shift assay; PBS, phosphate-buffered saline; RT, reverse transcriptase.