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Ras modifies proliferation and invasiveness of cells expressing human papillomavirus oncoproteins.

ABSTRACT: Infection by human papillomavirus (HPV) is a major risk factor for human cervical carcinoma. However, the HPV infection alone is not sufficient for cancer formation. Cervical carcinogenesis is considered a multistep process accompanied by genetic alterations of the cell. Ras is activated in approximately 20% of human cancers, and it is related to the metastatic conversion of tumor cells. We investigated how Ras activation was involved in the malignant conversion of HPV-infected lesions. The active form of H-ras was introduced into human primary keratinocytes expressing the HPV type 18 (HPV18) oncoproteins E6 and/or E7. We analyzed the keratinocytes' growth potentials and found that the activation of the Ras pathway induced senescence-like growth arrest. Senescence could be eliminated by high-risk E7 expression, suggesting that the pRb pathway was important for Ras-induced senescence. Then we analyzed the effect of Ras activation on epidermis development by using an organotypic "raft" culture and found that the E7 and H-ras coexpressions conferred invasive potential on the epidermis. This invasiveness resulted from the upregulation of MT1-MMP and MMP9 by H-ras and E7, respectively, in which the activation of the MEK/extracellular signal-regulated kinase pathway was involved. These results indicated that the activation of Ras or the related signal pathways promoted the malignant conversion of HPV-infected cells.

SUBMITTER: Yoshida S

PROVIDER: S-EPMC2519630 | biostudies-literature | 2008 Sep

REPOSITORIES: biostudies-literature

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Ras modifies proliferation and invasiveness of cells expressing human papillomavirus oncoproteins.

Yoshida Satoshi S Kajitani Naoko N Satsuka Ayano A Nakamura Hiroyasu H Sakai Hiroyuki H

Journal of virology 20080625 17

Infection by human papillomavirus (HPV) is a major risk factor for human cervical carcinoma. However, the HPV infection alone is not sufficient for cancer formation. Cervical carcinogenesis is considered a multistep process accompanied by genetic alterations of the cell. Ras is activated in approximately 20% of human cancers, and it is related to the metastatic conversion of tumor cells. We investigated how Ras activation was involved in the malignant conversion of HPV-infected lesions. The acti ...[more]

PMID: 18579583

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Project description:The E6 and E7 proteins are the major oncogenic drivers encoded by high-risk human papillomaviruses (HPVs). While many aspects of the transforming activities of these proteins have been extensively studied, there are fewer studies that have investigated how HPV E6/E7 expression affects the expression of cellular noncoding RNAs. The goal of our study was to investigate HPV16 E6/E7 modulation of cellular microRNA (miR) levels and to determine the potential consequences for cellular gene expression. We performed deep sequencing of small and large cellular RNAs in primary undifferentiated cultures of human foreskin keratinocytes (HFKs) with stable expression of HPV16 E6/E7 or a control vector. After integration of the two data sets, we identified 51 differentially expressed cellular miRs associated with the modulation of 1,456 potential target mRNAs in HPV16 E6/E7-expressing HFKs. We discovered that the degree of differential miR expression in HFKs expressing HPV16 E6/E7 was not necessarily predictive of the number of corresponding mRNA targets or the potential impact on gene expression. Additional analyses of the identified miR-mRNA pairs suggest modulation of specific biological activities and biochemical pathways. Overall, our study supports the model that perturbation of cellular miR expression by HPV16 E6/E7 importantly contributes to the rewiring of cellular regulatory circuits by the high-risk HPV E6 and E7 proteins that contribute to oncogenic transformation.ImportanceHigh-risk human papillomaviruses (HPVs) are the causative agents of almost all cervical cancers and many other cancers, including anal, vaginal, vulvar, penile, and oropharyngeal cancers. Despite the availability of efficacious HPV vaccines, it is critical to determine how HPVs cause cancer, as many people remain unvaccinated and the vaccine does not prevent cancer development in individuals who are already infected. Two HPV proteins, E6 and E7, are the major drivers of cancer development, and much remains to be learned about how the expression of these viral proteins reprograms infected cells, ultimately resulting in cancer development. Small, noncoding human RNAs, termed microRNAs (miRs), regulate gene expression and have been implicated in almost all human cancers, including HPV-associated cancers. Our study provides a comprehensive analysis of how E6 and E7 alter the expression of human miRs and how this potentially impacts cellular gene expression, which may contribute to cancer development.

Project description:BackgroundThe oncogenic activity of the high risk human papillomavirus type 16 (HPV16) is fully dependent on the E6 and E7 viral oncoproteins produced during viral infection. The oncoproteins interfere with cellular homeostasis by promoting proliferation, inhibiting apoptosis and blocking epithelial differentiation, driving the infected cells towards neoplastic progression. The causal relationship between expression of E6/E7 and cellular transformation allows inhibiting the oncogenic process by hindering the activity of the two oncoproteins. We previously developed and characterized some antibodies in single-chain format (scFvs) against the HPV16 E6 and E7 proteins, and demonstrated both in vitro and in vivo their antitumor activity consisting of protective efficacy against tumor progression of HPV16-positive cells.MethodsEnvisioning clinical application of the best characterized anti-HPV16 E6 and -HPV16 E7 scFvs, we verified their activity in the therapeutic setting, on already implanted tumors. Recombinant plasmids expressing the anti-HPV16 E6 scFvI7 with nuclear targeting sequence, or the anti-HPV16 E7 scFv43M2 with endoplasmic reticulum targeting sequence were delivered by injection followed by electroporation to three different preclinical models using C57/BL6 mice, and their effect on tumor growth was investigated. In the first model, the HPV16+ TC-1 Luc cells were used to implant tumors in mice, and tumor growth was measured by luciferase activity; in the second model, a fourfold number of TC-1 cells was used to obtain more aggressively growing tumors; in the third model, the HPV16+ C3 cells where used to rise tumors in mice. To highlight the scFv possible mechanism of action, H&E and caspase-3 staining of tumor section were performed.ResultsWe showed that both the anti-HPV16 E6 and HPV16 E7 scFvs tested were efficacious in delaying tumor progression in the three experimental models and that their antitumor activity seems to rely on driving tumor cells towards the apoptotic pathway.ConclusionBased on our study, two scFvs have been identified that could represent a safe and effective treatment for the therapy of HPV16-associated lesions. The mechanism underlying the scFv effectiveness appears to be leading cells towards death by apoptosis. Furthermore, the validity of electroporation, a methodology allowed for human treatment, to deliver scFvs to tumors was confirmed.

Project description:Glioma is one of the most common, rapidly progressive and fatal brain tumors, and accumulating evidence shows that microRNAs (miRNAs) play important roles in the development of cancers, including glioma. Therapeutic applications of miRNAs in Ras-driven glioma have been proposed; however, their specific functions and mechanisms are poorly understood. Here, we report that miR-1301-3p directly targets the neuroblastoma Ras viral oncogene homolog (N-Ras) and functions as a tumor-suppressor in glioma. Quantitative reverse transcription-PCR was applied to detect the expression of miR-1301-3p in glioma specimens. The direct target genes of miR-1301-3p were predicted by bioinformatic analysis and further verified by immunoblotting and luciferase assays. The effects of miR-1301-3p on the proliferation and cell cycle of glioma cells were analyzed by cell-counting kit 8, colony formation, 5-ethynyl-2-deoxyuridine (EDU) and flow cytometry assays. A xenograft model was used to study the effect of miR-1301-3p on tumor growth and angiogenesis. The expression levels of miR-1301-3p in glioma specimens were significantly downregulated. N-Ras was confirmed as a direct target of miR-1301-3p. MiR-1301-3p inhibited glioma cell growth and blocked the cell cycle to G1 by negatively regulating N-Ras and its downstream signaling pathway, MEK-ERK1/2. Furthermore, the inhibitory effects of miR-1301-3p could be rescued by the overexpression of N-Ras. The protein levels of N-Ras were up-regulated in clinical glioma specimens and were negatively correlated with miR-1301-3p expression levels (r=-056, P=0.0002). In vivo studies revealed that increased levels of miR-1301-3p delayed the growth of intracranial tumors, which was accompanied by decreased Ki67 and CD31 expression. Taken together, our results demonstrate that miR-1301-3p plays a significant role in inactivating the Ras signaling pathway through the inhibition of N-Ras, which may provide a novel therapeutic strategy for treatment of glioma and other Ras-driven cancers.

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Ras modifies proliferation and invasiveness of cells expressing human papillomavirus oncoproteins.

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Ras modifies proliferation and invasiveness of cells expressing human papillomavirus oncoproteins.

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