title: Six1 promotes epithelial-mesenchymal transition and malignant conversion in human papillomavirus type 16-immortalized human keratinocytes.
abstract: Six1, a member of the Six family of homeodomain transcription factors, is overexpressed in various human cancers, and SIX1 overexpression is associated with tumor progression and metastasis. Six1 messenger RNA levels increase during in vitro progression of human papillomavirus type 16 (HPV16)-immortalized human keratinocytes (HKc/HPV16) toward a differentiation-resistant (HKc/DR) phenotype. In this study, we show that HKc/DR-overexpressing Six1 exhibited a more mesenchymal phenotype, as characterized by a fibroblastic appearance and increased invasion. We utilized Whole Human Genome Microarrays to explore the gene expression changes associated with Six1 overexpression in HKc/DR. We found that overexpression of Six1 downregulated epithelial-related genes and upregulated mesenchymal-related genes, which suggests that Six1 overexpression induces epithelial-mesenchymal transition (EMT). Pathway analysis of the microarray data showed alterations in the transforming growth factor-beta (TGF-β) pathway, including enhanced expression of the TGF-β receptor type II (TβRII), and activation of the mitogen-activated protein kinase (MAPK) pathway in HKc/DR-overexpressing Six1, suggesting that Smad-independent pathways of TGF-β signaling may be involved in Six1-mediated EMT. p38 MAPK activation was required for sustained Six1-induced EMT and TβRII overexpression. Finally, we determined that Six1 overexpression in HKc/DR resulted in malignant conversion and increased the cancer stem cell (CSC)-like population. Thus, Six1 overexpression promotes EMT, CSCs properties and malignant conversion in HKc/DR through MAPK activation, which supports the possible use of p38-TβRII inhibitors for the treatment of cancers overexpressing Six1.
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy and Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA and Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, Columbia, SC 29208, USA Present address: University of Wisconsin Biotechnology Center, Madison, WI 53706, USA.
authors.forename: Hanwen
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA and.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy and Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA and Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, Columbia, SC 29208, USA Present address: University of Wisconsin Biotechnology Center, Madison, WI 53706, USA.
authors.forename: Diego
authors.initials: D
authors.lastname: Altomare
authors.affiliation: Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA and.
authors.forename: Maria M
authors.initials: MM
authors.lastname: Peña
authors.affiliation: Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, Columbia, SC 29208, USA Present address: University of Wisconsin Biotechnology Center, Madison, WI 53706, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Wan
authors.affiliation: Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, Columbia, SC 29208, USA.
authors.forename: Lucia
authors.initials: L
authors.lastname: Pirisi
authors.affiliation: Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy and Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA and Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, Columbia, SC 29208, USA Present address: University of Wisconsin Biotechnology Center, Madison, WI 53706, USA creekk@sccp.sc.edu.
authors.forename: Kim E
authors.initials: KE
authors.lastname: Creek
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000473:pathology; D002472:Cell Transformation, Viral; D016000:Cluster Analysis; D004195:Disease Models, Animal; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D006367:HeLa Cells; D064593:Heterografts; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D052162:Human papillomavirus 16 / Q000502:physiology; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism* / Q000473:pathology* / Q000821:virology; D020935:MAP Kinase Signaling System; D051379:Mice; D014411:Neoplastic Stem Cells / Q000378:metabolism; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D047368:Tumor Burden / Q000235:genetics
chemical_list: D018398:Homeodomain Proteins; D018125:Receptors, Transforming Growth Factor beta; C099236:SIX1 protein, human; D051785:Smad Proteins; D016212:Transforming Growth Factor beta