scholarly journals Abrogation of the Postmitotic Checkpoint Contributes to Polyploidization in Human Papillomavirus E7-Expressing Cells

2009 ◽  
Vol 83 (6) ◽  
pp. 2756-2764 ◽  
Author(s):  
Susan A. Heilman ◽  
Joshua J. Nordberg ◽  
Yingwang Liu ◽  
Greenfield Sluder ◽  
Jason J. Chen
Keyword(s):  
Human Papillomavirus ◽  
High Risk ◽  
Epithelial Cells ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Early Event ◽  
Major Mechanism ◽  
Microtubule Disruption ◽  
Human Epithelial Cells ◽  
E6 And E7

ABSTRACT High-risk types of human papillomavirus (HPV) are considered the major causative agents of cervical carcinoma. The transforming ability of HPV resides in the E6 and E7 oncogenes, yet the pathway to transformation is not well understood. Cells expressing the oncogene E7 from high-risk HPVs have a high incidence of polyploidy, which has been shown to occur as an early event in cervical carcinogenesis and predisposes the cells to aneuploidy. The mechanism through which E7 contributes to polyploidy is not known. It has been hypothesized that E7 induces polyploidy in response to mitotic stress by abrogating the mitotic spindle assembly checkpoint. It was also proposed that E7 may stimulate rereplication to induce polyploidy. We have tested these hypotheses by using human epithelial cells in which E7 expression induces a significant amount of polyploidy. We find that E7-expressing cells undergo normal mitoses with an intact spindle assembly checkpoint and that they are able to complete cytokinesis. Our results also exclude DNA rereplication as a major mechanism of polyploidization in E7-expressing cells upon microtubule disruption. Instead, we have shown that while normal cells arrest at the postmitotic checkpoint after adaptation to the spindle assembly checkpoint, E7-expressing cells replicate their DNA and propagate as polyploid cells. Thus, abrogation of the postmitotic checkpoint leads to polyploidy formation in E7-expressing human epithelial cells. Our results suggest that downregulation of pRb is important for E7 to induce polyploidy and abrogation of the postmitotic checkpoint.

scholarly journals Human Papillomavirus Type 16 E6 induces cell competition

2021 ◽  
Author(s):  
Nicole Brimer ◽  
Scott Vande Pol
Keyword(s):  
Human Papillomavirus ◽  
High Risk ◽  
Epithelial Cells ◽  
Human Papillomaviruses ◽  
Cell Competition ◽  
Vitro Assay ◽  
Epithelial Tumors ◽  
E6 Oncoprotein ◽  
E6 And E7

High risk human papillomavirus (HPV) infections induce squamous epithelial tumors in which the virus replicates.  Initially, the virus-infected epithelial cells are untransformed, but expand in both number and area at the expense of normal squamous epithelial cells.  How this occurs is unknown, but is presumed to be due to viral oncogene expression.  We have developed an  in vitro  assay in which colonies of post-confluent HPV16 expressing cells outcompete confluent surrounding normal keratinocytes for surface area.   The enhanced cell competition induced by the complete HPV16 genome is conferred by E6 expression alone, and not by individual expression of E5 or E7.   In traditional oncogene assays, E7 is a more potent oncogene than E6, but such assays do not include interaction with normal surrounding cells.  These new results separate classic oncogenicity that is primarily conferred by E7, from cell competition that we show is primarily conferred by E6, and provides a new biological role for E6 oncoproteins from high risk human papillomaviruses.   Importance High risk papillomavirus infections induce epithelial tumors, some of which evolve into malignancies.   The development and maintenance of cancer is due to the virally encoded E6 and E7 oncoproteins.  How a virally infected keratinocyte out-competes normal uninfected keratinocytes has been unknown.  The present work shows that the enhanced competition of HPV16-infected cells is primarily due to the expression of the E6 oncoprotein and not the E7 or E5 oncoproteins.   This work shows the importance of measuring oncoprotein traits in the context of cell competition with uninfected cells, and shows the potential of papillomavirus oncoproteins to be novel genetic probes for the analysis of cell competition

scholarly journals The Human Papillomavirus Type 31 Late 3′ Untranslated Region Contains a Complex Bipartite Negative Regulatory Element

2002 ◽  
Vol 76 (12) ◽  
pp. 5993-6003 ◽  
Author(s):  
Sarah A. Cumming ◽  
Claire E. Repellin ◽  
Maria McPhillips ◽  
Jonathan C. Radford ◽  
J. Barklie Clements ◽  
...  
Keyword(s):  
Gene Expression ◽  
Human Papillomavirus ◽  
High Risk ◽  
Epithelial Cells ◽  
Regulatory Element ◽  
Capsid Proteins ◽  
Cellular Proteins ◽  
Late Gene Expression ◽  
Hpv 16 ◽  
Negative Regulatory Element

ABSTRACT The papillomavirus life cycle is tightly linked to epithelial cell differentiation. Production of virus capsid proteins is restricted to the most terminally differentiated keratinocytes in the upper layers of the epithelium. However, mRNAs encoding the capsid proteins can be detected in less-differentiated cells, suggesting that late gene expression is controlled posttranscriptionally. Short sequence elements (less than 80 nucleotides in length) that inhibit gene expression in undifferentiated epithelial cells have been identified in the late 3′ untranslated regions (UTRs) of several papillomaviruses, including the high-risk mucosal type human papillomavirus type 16 (HPV-16). Here we show that closely related high-risk mucosal type HPV-31 also contains elements that can act to repress gene expression in undifferentiated epithelial cells. However, the HPV-31 negative regulatory element is surprisingly complex, comprising a major inhibitory element of approximately 130 nucleotides upstream of the late polyadenylation site and a minor element of approximately 110 nucleotides mapping downstream. The first 60 nucleotides of the major element have 68% identity to the negative regulatory element of HPV-16, and these elements bind the same cellular proteins, CstF-64, U2AF65, and HuR. The minor inhibitory element binds some cellular proteins in common with the major inhibitory element, though it also binds certain proteins that do not bind the upstream element.

High-Risk Human Papillomavirus Affects Prognosis in Patients With Surgically Treated Oropharyngeal Squamous Cell Carcinoma

2006 ◽  
Vol 24 (36) ◽  
pp. 5630-5636 ◽  
Author(s):  
Lisa Licitra ◽  
Federica Perrone ◽  
Paolo Bossi ◽  
Simona Suardi ◽  
Luigi Mariani ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
High Risk ◽  
Oropharyngeal Cancer ◽  
Clinical Results ◽  
Hpv Dna ◽  
Additional Information ◽  
Second Tumors ◽  
E6 And E7 ◽  
Second Tumor ◽  
P16 Expression

Purpose Human papillomavirus (HPV) DNA tumors actively integrating the E6 and E7 oncogenes have a distinct biologic behavior resulting in a more favorable prognosis. To which extent the viral integration by itself, and/or the associated wild-type (wt) TP53 status, and/or a functional p16 contribute to prognosis is unclear. Patients and Methods To clarify how the presence of high-risk (HR) -HPV, TP53, and p16INK4a status interact with clinical outcome, we considered a retrospective series of 90 consecutive oropharyngeal cancer patients treated primarily with surgery. Results Seventeen (19%) patients showed integrated HPV 16 DNA (HPV positive), wt TP53 in all but two patients, normal p16INK4a in 15 assessable patients, and p16 expression in all 17 patients. Thirty-five patients (39%), two of whom were HPV positive, harbored TP53 mutations. p16INK4a deletion and p16 null immunophenotype occurred in 28 and 58 patients, respectively, and was similarly distributed in both patients with mutated TP53 (48% and 82%, respectively) and in patients with wt TP53 (46% and 77%, respectively). Statistical analysis showed that HPV-positive status significantly affects all investigated end points: overall survival (P = .0018), incidence of tumor relapse (P = .0371), and second tumor (P = .0152), whereas TP53 and p16INK4a status and p16 expression were not prognostic by themselves. Conclusion Our molecular and clinical results are in agreement with previous findings but provide additional information into the biologic mechanisms involved in HR-HPV oropharyngeal cancer in comparison to HPV-negative tumors. According to the reduced risk of relapse and second tumors associated with HR-HPV positivity of oropharyngeal cancer, the therapeutic strategy and follow-up procedures should be reviewed.

Restoration of telomeres in human papillomavirus-immortalized human anogenital epithelial cells

1994 ◽  
Vol 14 (2) ◽  
pp. 961-969
Author(s):  
A J Klingelhutz ◽  
S A Barber ◽  
P P Smith ◽  
K Dyer ◽  
J K McDougall
Keyword(s):  
Human Papillomavirus ◽  
Epithelial Cells ◽  
Telomere Length ◽  
Open Reading Frames ◽  
Population Doubling ◽  
Telomere Shortening ◽  
Human Papillomavirus Type 16 ◽  
Immortalized Cells ◽  
E6 And E7

Loss of telomeres has been hypothesized to be important in cellular senescence and may play a role in carcinogenesis. In this study, we have measured telomere length in association with the immortalization and transformation of human cervical and foreskin epithelial cells by the human papillomavirus type 16 or 18 E6 and E7 open reading frames. By using a telomeric TTAGGG repeat probe, it was shown that the telomeres of precrisis normal and E6-, E7-, and E6/E7-expressing cells gradually shortened with passaging (30 to 100 bp per population doubling). Cells that expressed both E6 and E7 went through a crisis period and gave rise to immortalized lines. In contrast to precrisis cells, E6/E7-immortalized cells generally showed an increase in telomere length as they were passaged in culture, with some later passage lines having telomeres that were similar to or longer than the earliest-passage precrisis cells examined. No consistent association could be made between telomere length and tumorigenicity of cells in nude mice. However, of the three cell lines that grew in vivo, two had long telomeres, thus arguing against the hypothesis that cancer cells favor shortened telomeres. Our results indicate that arrest of telomere shortening may be important in human papillomavirus-associated immortalization and that restoration of telomere length may be advantageous to cells with regard to their ability to proliferate.

scholarly journals Restoration of telomeres in human papillomavirus-immortalized human anogenital epithelial cells.

1994 ◽  
Vol 14 (2) ◽  
pp. 961-969 ◽  
Author(s):  
A J Klingelhutz ◽  
S A Barber ◽  
P P Smith ◽  
K Dyer ◽  
J K McDougall
Keyword(s):  
Human Papillomavirus ◽  
Epithelial Cells ◽  
Telomere Length ◽  
Open Reading Frames ◽  
Population Doubling ◽  
Telomere Shortening ◽  
Human Papillomavirus Type 16 ◽  
Immortalized Cells ◽  
E6 And E7

Loss of telomeres has been hypothesized to be important in cellular senescence and may play a role in carcinogenesis. In this study, we have measured telomere length in association with the immortalization and transformation of human cervical and foreskin epithelial cells by the human papillomavirus type 16 or 18 E6 and E7 open reading frames. By using a telomeric TTAGGG repeat probe, it was shown that the telomeres of precrisis normal and E6-, E7-, and E6/E7-expressing cells gradually shortened with passaging (30 to 100 bp per population doubling). Cells that expressed both E6 and E7 went through a crisis period and gave rise to immortalized lines. In contrast to precrisis cells, E6/E7-immortalized cells generally showed an increase in telomere length as they were passaged in culture, with some later passage lines having telomeres that were similar to or longer than the earliest-passage precrisis cells examined. No consistent association could be made between telomere length and tumorigenicity of cells in nude mice. However, of the three cell lines that grew in vivo, two had long telomeres, thus arguing against the hypothesis that cancer cells favor shortened telomeres. Our results indicate that arrest of telomere shortening may be important in human papillomavirus-associated immortalization and that restoration of telomere length may be advantageous to cells with regard to their ability to proliferate.

scholarly journals Decreased Migration of Langerhans Precursor-Like Cells in Response to Human Keratinocytes Expressing Human Papillomavirus Type 16 E6/E7 Is Related to Reduced Macrophage Inflammatory Protein-3α Production

2005 ◽  
Vol 79 (23) ◽  
pp. 14852-14862 ◽  
Author(s):  
Jennifer C. Guess ◽  
Dennis J. McCance
Keyword(s):  
Immune Response ◽  
Human Papillomavirus ◽  
High Risk ◽  
Immune Cells ◽  
Langerhans Cells ◽  
Inflammatory Protein ◽  
Infected Cells ◽  
Hpv Types ◽  
E6 And E7 ◽  
Macrophage Inflammatory Protein

ABSTRACT Infection with high-risk human papillomavirus (HPV) types, particularly types 16 and 18, contributes to 90% of cervical cancer cases. HPV infects cutaneous or mucosal epithelium, tissue that is monitored for microbial infection or damage by Langerhans cells. In lesions produced by HPV type 16, there is a reduction in numbers of immune cells, especially Langerhans cells. Langerhans precursor cells selectively express CCR6, the receptor for macrophage inflammatory protein 3α (MIP-3α), and function as potent immune responders to inflamed epithelium and initiators of the innate immune response. It has been reported that E6 and E7 of high-risk HPVs interfere with immune mediators in order to suppress the recruitment of immune cells and antiviral activities of infected cells. Here we show that, following proinflammatory stimulus, HPV-16 E6 and E7 inhibit MIP-3α transcription, resulting in suppression of the migration of immature Langerhans precursor-like cells. Interestingly, the E6 and E7 proteins from the low-risk HPV types also inhibited MIP-3α transcription. These results suggest that one mechanism by which HPV-infected cells suppress the immune response may be through the inhibition of a vital alert signal, thus contributing to the persistence of HPV infection.

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