title: Regulation of HIF-1 alpha by the proprotein convertases furin and PC7 in human squamous carcinoma cells.
abstract: Proprotein convertases (PC), a family of serine proteases, process cancer-related substrates such as growth factors, growth factor receptors, cell adhesion molecules, metalloproteinases, etc. HIF-1α is a major transcription factor involved in tumorigenesis by sensing intratumoral hypoxia. Furin (PCSK3) is one of the numerous target genes regulated by HIF-1α transactivation and its distribution into endosomal compartments and onto the cell surface can be triggered by hypoxia via HIF-1α. siRNAs to knockdown PCs were transfected into cells alone or in combination with different drug treatments. Protein and RNA expression levels were analyzed by Western blotting or RT-PCR, respectively. PC7 (PCSK7) and furin siRNAs upregulated HIF-1α protein under normoxic condition to a level similar to that obtained by cobalt chloride treatment, eventually leading to activation of VEGF-A synthesis in two human head and neck squamous cell carcinoma cell lines. The unchanged levels of HIF-1α mRNA expression under siRNA treatment and the additive HIF-1α induction of PC siRNAs and either cobalt chloride or the 26S ribosome inhibitor, MG-132, suggested a post-transcriptional PC-mediated regulation. Furthermore, cycloheximide chase showed that PC7/furin siRNA regulation occurred at the level of HIF-1α translation. A specific IGF-1R signaling inhibitor was able to attenuate the PC siRNA induction of HIF-1α, suggesting the involvement of the IGF-1R pathway. Thus, the data show that PCs regulate HIF-1α. Furin and PC7 siRNAs induced HIF-1α protein by increasing its translation, resulting in upregulation of VEGF-A. This finding may provide insight into intricate PC functions that seem to be independent from their substrate-processing activity.
authors.affiliation: Department of Pathology, Fox Chase Cancer Center, Philadelphia, Pennsylvania.|Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Jian
authors.initials: J
authors.lastname: Fu
authors.affiliation: Department of Pathology, Fox Chase Cancer Center, Philadelphia, Pennsylvania.|Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Jirong
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Pathology, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Yulan
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Department of Pathology, Fox Chase Cancer Center, Philadelphia, Pennsylvania.|Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Courtney Lyons
authors.initials: CL
authors.lastname: Testa
authors.affiliation: Department of Pathology, Fox Chase Cancer Center, Philadelphia, Pennsylvania.|Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Andres J
authors.initials: AJ
authors.lastname: Klein-Szanto
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D015536:Down-Regulation; D045683:Furin / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006258:Head and Neck Neoplasms / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D014176:Protein Biosynthesis; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D013381:Subtilisins / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D042461:Vascular Endothelial Growth Factor A; D007334:Insulin-Like Growth Factor I; C099101:PCSK7 protein, human; D013381:Subtilisins; D045683:Furin
keywords: HIF-1α regulation; PC7; cancer cells; furin; proprotein convertases