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Roles of the PDZ-binding motif of HPV 16 E6 protein in oncogenic transformation of human cervical keratinocytes.

ABSTRACT: The high-risk human papillomavirus E6 proteins have been shown to interact with and lead to degradation of PDZ-domain-containing proteins through its carboxy-terminal motif. This PDZ-binding motif plays important roles in transformation of cultured cells and carcinogenesis of E6-transgenic mice. However, its biological effects on the natural host cells have not been elucidated. We have examined its roles in an in vitro carcinogenesis model for cervical cancer, in which E6 and E7 together with activated HRAS (HRASG12V ) can induce tumorigenic transformation of normal human cervical keratinocytes. In this model, E6?151 mutant, which is defective in binding to PDZ domains, almost lost tumorigenic ability, whereas E6SAT mutant, which is defective in p53 degradation showed activity close to wild-type E6. Interestingly, we found decreased expression of PAR3 in E6-expressing cells independently of E6AP, which has not been previously recognized. Therefore, we knocked down several PDZ-domain containing proteins including PAR3 in human cervical keratinocytes expressing E7, HRASG12V and E6?151 to examine whether depletion of these proteins can restore the tumorigenic ability. Single knockdown of SCRIB, MAGI1 or PAR3 significantly but partially restored the tumorigenic ability. The combinatorial knockdown of SCRIB and MAGI1 cooperatively restored the tumorigenic ability, and additional depletion of PAR3 further enhanced the tumorigenic ability surpassing that induced by wild-type E6. These data highlight the importance of the carboxy-terminal motif of the E6 protein and downregulation of PAR3 in tumorigenic transformation of human cervical keratinocytes.

SUBMITTER: Yoshimatsu Y

PROVIDER: S-EPMC5497797 | biostudies-other | 2017 Jul

REPOSITORIES: biostudies-other

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Roles of the PDZ-binding motif of HPV 16 E6 protein in oncogenic transformation of human cervical keratinocytes.

Yoshimatsu Yuki Y Nakahara Tomomi T Tanaka Katsuyuki K Inagawa Yuki Y Narisawa-Saito Mako M Yugawa Takashi T Ohno Shin-Ichi SI Fujita Masatoshi M Nakagama Hitoshi H Kiyono Tohru T

Cancer science 20170605 7

The high-risk human papillomavirus E6 proteins have been shown to interact with and lead to degradation of PDZ-domain-containing proteins through its carboxy-terminal motif. This PDZ-binding motif plays important roles in transformation of cultured cells and carcinogenesis of E6-transgenic mice. However, its biological effects on the natural host cells have not been elucidated. We have examined its roles in an in vitro carcinogenesis model for cervical cancer, in which E6 and E7 together with ac ...[more]

PMID: 28440909

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Project description:PurposeHigh-risk human papillomaviruses (HR HPV) cause cervical cancer, and in these cancers, HPV type 16 is the most common HR type. The HR viral oncogenes E6 and E7 partner with cellular proteins to drive cancer and modulate immune pathways; previously, we demonstrated in keratinocytes that HPV 16 E6 and high expression of the endogenous host protein partner NFX1-123 led to the increased expression of multiple genes, including Notch1, secretory leukocyte peptidase inhibitor (SLPI), and retinoic acid early transcript 1G (RAET1G). The present study was conducted to determine if NFX1-123 was highly expressed in cervical cancer and if genes increased by NFX1-123 and 16E6 in keratinocytes were also increased in cervical cancers.Materials and methodsThe Cancer Genome Atlas (TCGA) database and The Human Protein Atlas database were used to compare relative mRNA and protein gene expression, respectively, in the normal cervix and cervical cancers. Formalin-fixed paraffin-embedded (FFPE) normal cervix and HPV 16 positive cervical cancer samples were analyzed for relative protein expression by immunohistochemical staining. Protein expression of a subset of regulated genes was quantified by Western blot of HPV positive and negative cell lines.ResultsImmunohistochemical staining of HPV 16 positive cervical dysplasias and cancers revealed high NFX1-123, Ki67, and Notch1 expression. NFX1 and NFX1L1 mRNA levels were increased in cervical cancers compared to normal cervix in the TCGA database. Fourteen genes previously identified as upregulated in keratinocytes with 16E6 and overexpressed NFX1-123 also had high mRNA expression and selected genes had high protein expression in cervical cancers and cell lines.ConclusionIn cervical cancer, NFX1-123 is highly expressed, and 16E6 and NFX1-123 together alter the expression of a wide set of genes. The involvement of these genes in cell proliferation, differentiation, invasion, and metastasis provides further insight into potential ways that HR HPVs promote cancer initiation and maintenance.

Project description:Background The in vivo properties of HR-HPV E6 and E7 oncoproteins have been previously evaluated through the generation and characterization of HPV transgenic mouse strains. Although K14E6 transgenic mice develop spontaneous tumors of the skin epithelium, no spontaneous reproductive tract malignancies arise, unless the transgenic mice were treated chronically with 17β-estradiol. Taken together, these findings suggest that E6 performs critical functions in normal adult cervix and skin, highlighting the need to define E6-controlled transcriptional programs in these tissues. We evaluated the different expression profile of 14,000 genes in skin or cervix from young K14E6 transgenic mice compared with corresponding tissues from non-transgenic (FVB) mice. Result Microarray analysis identified a total of 676 and 1154 genes that were significantly up and down-regulated, respectively, in skin from K14E6 transgenic mice. On the other hand, in cervix from K14E6 transgenic mice we found that only 97 and 252 genes were significantly up and down-regulated, respectively. One of the most affected processes in the skin from K14E6 transgenic mice was the cell cycle. We also found that skin from transgenic mice showed down-regulation in pro-apoptotic genes expression, particularly in those related to the extrinsic apoptotic pathway. In contrast, we observed up-regulation of anti-apoptotic genes. Another pathway that was severely affected in skin was the immune response. In cervix from transgenic mice, we could not find affected any gene related to the cell cycle and apoptosis pathways. Interestingly, we observed alterations in the expression of immune response genes in cervix from K14E6 transgenic mice. Pathways such as angiogenesis, cell junction, cytoskeleton, keratinocyte differentiation and epidermis development, showed different gene expression in skin or cervix from K14E6 transgenic mice. Conclusion Alterations in gene expression identified in the current study might partially explain why our K14E6 transgenic mice present a more aggressive phenotype in the skin than in the cervix. Expression of the HPV16 E6 oncoprotein alters expression of genes that fell into several functional groups providing insights into pathways by which E6 deregulate cell cycle progression, apoptosis and the host resistance to infection and immune function, providing new opportunities for early diagnostic markers and therapeutic drug targets. Keywords: Human_papillomavirus, transgenic mice, expression profile

Project description:High-risk human papillomavirus (HPV) is a major risk factor for oral and pharyngeal cancers (OPCs), yet the detailed mechanisms by which HPV promotes OPCs are not understood. Forkhead box M1B (FoxM1B) is an oncogene essential for cell cycle progression and tumorigenesis, and it is aberrantly overexpressed in many tumors. We previously showed that FoxM1B was the putative target of an epithelial-specific transcription factor, Grainyhead-like 2 (GRHL2). In the current study, we demonstrate that HPV type 16 (HPV-16) E6 induces FoxM1B in human oral keratinocytes (HOKs) and tonsillar epithelial cells (TECs) in part through GRHL2. FoxM1B was barely detectable in cultured normal human oral keratinocytes (NHOKs) and progressively increased in immortalized HOKs harboring HPV-16 genome (HOK-16B) and tumorigenic HOK-16B/BaP-T cells. Retroviral expression of HPV-16 E6 and/or E7 in NHOKs, TECs, and hypopharyngeal carcinoma cells (FaDu) revealed induction of FoxM1B and GRHL2 by the E6 protein but not E7. Both GRHL2 and FoxM1B were strongly induced in the epidermis of HPV-16 E6 transgenic mice and HPV+ oral squamous cell carcinomas. Ectopic expression of FoxM1B led to acquisition of transformed phenotype in HOK-16B cells. Loss of FoxM1B by lentiviral short hairpin RNA vector or chemical inhibitor led to elimination of tumorigenic characteristics of HOK-16B/BaP-T cells. Luciferase reporter assay revealed that GRHL2 directly bound and regulated the FoxM1B gene promoter activity. Using epithelial-specific Grhl2 conditional knockout mice, we exposed wild-type (WT) and Grhl2 KO mice to 4-nitroquinolin 1-oxide (4-NQO), which led to induction of FoxM1B in the tongue tissues and rampant oral tumor development in the WT mice. However, 4-NQO exposure failed to induce tongue tumors or induction of FoxM1B expression in Grhl2 KO mice. Collectively, these results indicate that HPV-16 induces FoxM1B in part through GRHL2 transcriptional activity and that elevated FoxM1B level is required for oropharyngeal cancer development.

Dataset Information

Roles of the PDZ-binding motif of HPV 16 E6 protein in oncogenic transformation of human cervical keratinocytes.

Publications

Roles of the PDZ-binding motif of HPV 16 E6 protein in oncogenic transformation of human cervical keratinocytes.

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