Roles of PI3K/Akt and c-Jun Signaling Pathways in Human Papillomavirus Type 16 Oncoprotein-Induced HIF-1α, VEGF, and IL-8 Expression and In Vitro Angiogenesis in Non-Small Cell Lung Cancer Cells

Abstract

Background and ObjectivesHuman papillomavirus (HPV)-16 infection may be related to non-smoking associated lung cancer. Our previous studies have found that HPV-16 oncoproteins promoted angiogenesis via enhancing hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), and interleukin-8 (IL-8) expression in non-small cell lung cancer (NSCLC) cells. In this study, we further investigated the roles of PI3K/Akt and c-Jun signaling pathways in it.MethodsHuman NSCLC cell lines, A549 and NCI-H460, were stably transfected with pEGFP-16 E6 or E7 plasmids. Western blotting was performed to analyze the expression of HIF-1α, p-Akt, p-P70S6K, p-P85S6K, p-mTOR, p-JNK, and p-c-Jun proteins. VEGF and IL-8 protein secretion and mRNA levels were determined by ELISA and Real-time PCR, respectively. The in vitro angiogenesis was observed by human umbilical vein endothelial cells (HUVECs) tube formation assay. Co-immunoprecipitation was performed to analyze the interaction between c-Jun and HIF-1α.ResultsHPV-16 E6 and E7 oncoproteins promoted the activation of Akt, P70S6K, P85S6K, mTOR, JNK, and c-Jun. LY294002, a PI3K inhibitor, inhibited HPV-16 oncoprotein-induced activation of Akt, P70S6K, and P85S6K, expression of HIF-1α, VEGF, and IL-8, and in vitro angiogenesis. c-Jun knockdown by specific siRNA abolished HPV-16 oncoprotein-induced HIF-1α, VEGF, and IL-8 expression and in vitro angiogenesis. Additionally, HPV-16 oncoproteins promoted HIF-1α protein stability via blocking proteasome degradation pathway, but c-Jun knockdown abrogated this effect. Furthermore, HPV-16 oncoproteins increased the quantity of c-Jun binding to HIF-1α.ConclusionsPI3K/Akt signaling pathway and c-Jun are involved in HPV-16 oncoprotein-induced HIF-1α, VEGF, and IL-8 expression and in vitro angiogenesis. Moreover, HPV-16 oncoproteins promoted HIF-1α protein stability possibly through enhancing the interaction between c-Jun and HIF-1α, thus making a contribution to angiogenesis in NSCLC cells.

LMO4 is a prognostic marker involved in cell migration and invasion in non-small-cell lung cancer

“…LMO4 can inhibit the expression of the fusion proteinengrailed-LMO4 while suppressing cell growth, and can induce the apoptosis of breast cancer cells, indicating that LMO4 contributes to oncogenesis by similar mechanisms, thus enhancing cell survival and proliferation (19). AKT/PI3K activation is involved in the carcinogenesis and tumor progression of various solid tumors, including NSCLC (20,21). Lu et al reported that the transcriptional coactivator LMO4 modulated the cytostatic effects of TGF-beta in epithelial cells, and associated with and regulated a prototype Smad target promoter (14).…”

Activation of sonic hedgehog signaling enhances cell migration and invasion by induction of matrix metalloproteinase-2 and -9 via the phosphoinositide-3 kinase/AKT signaling pathway in glioblastoma

“…Accumulating evidence revealed that the PI3K/Akt pathway is activated in multiple types of cancer, including kidney, lung, liver and ovarian cancer, and has an important role in migration and invasion (26)(27)(28). Several studies reported that the PI3K/Akt pathway is mediated by the SHH pathway.…”

PDGF-BB/KLF4/VEGF Signaling Axis in Pulmonary Artery Endothelial Cell Angiogenesis

“…Previous studies have shown that PDGF is crucial for pulmonary vascular remodeling [16]. PDGF-mediated PAH involves multiple mechanisms, including the ERKl/2and PI3k/Akt signaling pathways [23, 24], both of which ultimately results in an over-expression of VEGF [25, 26]. Moreover, recent reports have revealed that tumor angiogenesis is driven by a complex interplay between the pro-angiogenic VEGF/ VEGFR and PDGF/PDGFR pathways within the tumor microenvironment [27].…”

“…Moreover, KLF4 promotes angiogenesis by activating VEGF signaling in endothelial cells [25, 26]. The Krüppel-like family is a group of transcription factors characterized by the presence of a three-zinc finger DNA-binding domain.…”