The HPV E7 oncoprotein inhibits tumor necrosis factor α-mediated apoptosis in normal human fibroblasts

Da, Thompson; Zacny, Valerie; Belinsky, Glenn S.; Classon, Marie; Jones, D. Leanne; Schlegel, Robert; Münger, Karl

doi:10.1038/sj.onc.1204483

Cited by 49 publications

(43 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…E7-immortalized human fibroblasts are also resistant against TNF-a mediated cell death and the suppression of E7 by RNA interference causes apoptosis. 61,62 In addition to TNF-a, previous studies have shown a consistent result that the E6 and E7 oncoproteins have the potential to synergize with activated PKB/AKT signaling to prompt cell immortalization. In support of these observations, in this study, we have further demonstrated that HPV16 E7 upregulated DYRK1A is critically involved in the regulation of subsequent cellular changes such that knockdown Dyrk1a in the HPV immortalized cells led to increased BAD protein and apoptosis.…”

Section: Discussionmentioning

confidence: 82%

Increased expression of Dyrk1a in HPV16 immortalized Keratinocytes enable evasion of apoptosis

Chang

Lin

Yang

et al. 2007

Intl Journal of Cancer

View full text Add to dashboard Cite

Immortalization is a critical event in virus-related oncogenesis. No enough information, however, is currently available to elucidate the changes that occur in cellular molecules during immortalization. To identify potential cellular markers or regulators involving in immortalization, a paired-cell model of primary foreskin keratinocytes (FK) and HPV16 immortalized foreskin keratinocytes were established. Using mRNA differential display, RT-PCR and Northern blot methods, we have identified and confirmed that Dyrk1a (dual-specificity tyrosine-phosphorylated and regulated kinase 1A) is present and increased in HPV16 immortalized cells, but is absent in primary keratinocytes. Moreover, transfection of E7 siRNA oligo into immortalized cells leads to a diminishing E7 expression and the eventual disappearance of Dyrk1a. Similar results of Dyrk1a expressional differences could also be seen when tissue specimens were compared using LCM/real-time PCR and immunohistochemistry analysis; malignant cervical lesions contain significantly more DYRK1A than normal tissue. It was also demonstrated that raised DYRK1A could rearrange the cellular localization of FKHR (forkhead in rhabdomyosarcoma), an apoptosis activator, and suppress BAD. Importantly, this phenomenon can be reversed when endogenous Dyrk1a was knocked down in immortalized cells by RNA interference. These results suggest that the raised Dyrk1a in HPV16 immortalized keratinocytes and cervical lesions may serve as a candidate antiapoptotic factor in the FKHR regulated pathway and initiate immortalization and tumorigenesis gradually. ' 2007 Wiley-Liss, Inc.Key words: HPV16; keratinocytes; Dyrk1a; immortalization; apoptosis Mammalian cells have a limited life span and proliferating capacity when cultivated in vitro. Replicate senescence or the terminal arrest state, has been found to be accompanied by several molecular changes that lead to an activated suppression of the cell cycle and the shortening of the telomeres. 1 Similar to apoptosis, cellular senescence is thought to be a mechanism of tumor suppression because it prevents the outgrowth of cells that have acquired mutations in genes rendering them cancerous. Consistent with this model, several tumor suppressor genes (such as, overexpressed p16 or ZNF217, activated p53 and deregulated Rassf1a or c-myc, etc) or their products have been reported and shown to be associated in parallel with telomere irregularities at the onset of cellular senescence. 2 Telomere shortening has been shown to generate unstable DNA leading to p53 activation and the subsequent transcriptional induction of the cdk inhibitor p21 CIP13 that moves cells into senescence state. Therefore, preventing telomere erosion by ectopic expression of telomerase is sufficient to immortalized primary cells in vitro and thus extend life span. [4][5][6] Although it works in human fibroblast, telemorase alone, however, is not sufficient to induce immortalization in human keratinocytes and mammary epithelial cells. 7 To identify other factors that are involved ...

show abstract

Section: Discussionmentioning

confidence: 82%

Increased expression of Dyrk1a in HPV16 immortalized Keratinocytes enable evasion of apoptosis

Chang

Lin

Yang

et al. 2007

Intl Journal of Cancer

View full text Add to dashboard Cite

show abstract

“…In one paper in which the entire HPV 18 sequence was present, the authors found that it conferred resistance to TNF. 71 E7, on the other hand, has been reported both to protect 72 and to sensitize 73 human fibroblasts or keratinocytes, respectively, from TNF. Our own results with the CaSki and SiHa cells (Figure 1) are consistent with the E6 dose-dependent response we have worked out in greater molecular detail in the U2OS cells, and it may be that dosage effects are important for viral proteins other than E6.…”

Section: Discussionmentioning

confidence: 99%

The human papillomavirus 16 E6 protein can either protect or further sensitize cells to TNF: effect of dose

et al. 2005

View full text Add to dashboard Cite

High-risk strains of human papillomavirus, including HPV 16, cause human cervical carcinomas, due in part to the activity of their E6 oncogene. E6 interacts with a number of cellular proteins involved in host-initiated apoptotic responses. Paradoxically, literature reports show that E6 can both protect cells from and sensitize cells to tumor necrosis factor (TNF). To examine this apparent contradiction, E6 was transfected into U2OS cells and stable clones were treated with TNF. Intriguingly, clones with a high level of E6 expression displayed an increased sensitivity to TNF by undergoing apoptosis, while those with low expression were resistant. Furthermore, TNF treatment of cells in which the expression of E6 was regulated by the addition of doxycycline demonstrated clearly that while low levels of E6 protect cells from TNF, high levels sensitize cells. Together, these results demonstrate that virus-host interactions can be complex and that both quantitative and qualitative aspects are important in determining outcome.

show abstract

“…The role of high-risk HPV E7 in apoptosis is more controversial and the mechanism is not well defined. On the one hand, E7-immortalized human fibroblasts are resistant against TNF-a/CHX-mediated cell death (Thompson et al, 2001) and suppression of E7 expression in cervical carcinoma cells by RNA interference causes apoptosis (Jiang and Milner, 2002). On the other hand, E7 expression in keratinocyte sensitizes cells to TNF-a-mediated apoptosis (Stoppler et al, 1998) and predisposes human fibroblast to serum starvation-mediated apoptosis (Jones et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

“…Cells (5 Â 10 4 /well) were cotransfected with 0.1 mg of a c-IAP2 promoter controlled-luciferase construct (À900 LUC), 0.002 mg of pRL-SV40 Renilla luciferase control vector, 0.4 mg lacZ or 0.2 mg HPV16 E6 and 0.2 mg HPV16 E7 plasmids, luciferase assay was performed as in Figure 2. As a positive control, cells cotransfected with lacZ and À900 LUC reporter were treated with 20 ng/ml TNF-a in the last 4 h of transfection c-IAP2 upregulation by HPV E6 and E7 H Yuan et al (Thompson et al, 2001). Ectopic c-IAP2 expression was confirmed by Western blot using both anti-HA and antic-IAP2 antibodies (Figure 4a).…”

Section: Ectopic Expression Of C-iap2 Protected Nhok From Tnf-a/cyclomentioning

confidence: 99%

Human papillomavirus type 16 E6 and E7 oncoproteins upregulate c-IAP2 gene expression and confer resistance to apoptosis

Yuan

Zhuo

et al. 2005

Oncogene

View full text Add to dashboard Cite

The HPV E7 oncoprotein inhibits tumor necrosis factor α-mediated apoptosis in normal human fibroblasts

Cited by 49 publications

References 51 publications

Increased expression of Dyrk1a in HPV16 immortalized Keratinocytes enable evasion of apoptosis

Increased expression of Dyrk1a in HPV16 immortalized Keratinocytes enable evasion of apoptosis

The human papillomavirus 16 E6 protein can either protect or further sensitize cells to TNF: effect of dose

Human papillomavirus type 16 E6 and E7 oncoproteins upregulate c-IAP2 gene expression and confer resistance to apoptosis

Contact Info

Product

Resources

About