p53-Independent Abrogation of a Postmitotic Checkpoint Contributes to Human Papillomavirus <i>E6</i>-Induced Polyploidy

Liu, Yingwang; Heilman, Susan Ann; Illanes, Diego; Sluder, Greenfield; Chen, Jason J.

doi:10.1158/0008-5472.can-06-3436

Cited by 46 publications

(81 citation statements)

References 43 publications

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“…Primary human keratinocytes (PHKs) were derived from neonatal human foreskin epithelium obtained from the University of Massachusetts Hospital, as described previously (24). Spontaneously immortalized human keratinocyte NIKS cells were described previously (24).…”

Section: Methodsmentioning

confidence: 99%

“…PHK, NIKS, and RPE1 cells expressing HPV-16 E6, HPV-16 E6 mutant F2V (bearing a mutation of Phe-2 to Val), or vector were established by retrovirus-mediated infection using the pBabe-puro-based retroviral vector as described previously (24). The cells were maintained in puromycin and used within 8 passages.…”

Section: Methodsmentioning

confidence: 99%

“…We have previously identified several HPV-16 E6 mutants that are defective for p53 degradation and yet competent for attenuating the postmitotic checkpoint (24). The ability of E6 mutants to abrogate the postmitotic checkpoint was demonstrated in PHKs.…”

Section: Expression Of Postmitotic Checkpoint-related Proteins In Hpvmentioning

confidence: 99%

“…However, p21 is expressed in a subset of HPV-positive cervical intraepithelial neoplasia (CIN) and cervical tumor tissues (22,23). We have previously identified a p53-independent function of E6 in attenuating the postmitotic checkpoint (24). This observation is biologically relevant.…”

mentioning

confidence: 98%

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Role of Cdk1 in the p53-Independent Abrogation of the Postmitotic Checkpoint by Human Papillomavirus E6

Zhang

Liu

Zhao

et al. 2015

J Virol

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Specific types of human papillomavirus (HPV) are strongly associated with the development of cervical carcinoma. The HPV E6 oncoprotein from HPV degrades p53 and abrogates cell cycle checkpoints. Nonetheless, functional p53 has been observed in cervical cancer. We have previously identified a p53-independent function of E6 in attenuating the postmitotic G 1 -like checkpoint that can lead to polyploidy, an early event during cervical carcinogenesis that predisposes cells to aneuploidy. How E6 promotes cell cycle progression in the presence of p53 and its target, p21, remains a mystery. In this study, we examined the expression of cell cycle-related genes in cells expressing wild-type E6 and the mutant that is defective in p53 degradation but competent in abrogating the postmitotic checkpoint. Our results demonstrated an increase in the steady-state levels of G 1 -and G 2 -related cyclins/Cdks in E6-expressing keratinocytes. Interestingly, only Cdk1 remained active in E6 mutant-expressing cells while bypassing the postmitotic checkpoint. Furthermore, the downregulation of Cdk1 impaired the ability of both wild-type and mutant E6 to induce polyploidy. Our study thus demonstrated an important role for Cdk1, which binds p21 with lower affinity than Cdk2, in abrogating the postmitotic checkpoint in E6-expressing cells. We further show that E2F1 is important for E6 to upregulate Cdk1. Moreover, reduced nuclear p21 localization was observed in the E6 mutant-expressing cells. These findings shed light on the mechanisms by which HPV induces genomic instability and hold promise for the identification of drug targets. IMPORTANCEHPV infection is strongly associated with the development of cervical carcinoma. HPV encodes an E6 oncoprotein that degrades the tumor suppressor p53 and abrogates cell cycle checkpoints. Nonetheless, functional p53 has been observed in cervical cancer. We have recently demonstrated a p53-independent abrogation of the postmitotic checkpoint by HPV E6 that induces polyploidy. However, the mechanism is not known. In this study, we provide evidence that Cdk1 plays an important role in this process. Previously, Cdk2 was thought to be essential for the G 1 /S transition, while Cdk1 only compensated its function in the absence of Cdk2. Our studies have demonstrated a novel role of Cdk1 at the postmitotic G 1 -like checkpoint in the presence of Cdk2. These findings shed light on the mechanisms by which HPV induces genomic instability and hold promise for the identification of drug targets. G enomic instability in the form of polyploidy, the state in which cells have more than two sets of chromosomes, has been suggested to play a causal role in tumorigenesis (1). Polyploidy can lead to numerical and structural chromosome abnormalities by increasing the rate of DNA breakage and damage (2). Tetrasomy in basal keratinocytes has been found in low-grade, squamous intraepithelial lesions of the cervix infected with high-risk but not low-risk human papillomavirus (HPV) types (3). Significantly, tetraploidy ...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Expression Of Postmitotic Checkpoint-related Proteins In Hpvmentioning

confidence: 99%

mentioning

confidence: 98%

See 2 more Smart Citations

Role of Cdk1 in the p53-Independent Abrogation of the Postmitotic Checkpoint by Human Papillomavirus E6

Zhang

Liu

Zhao

et al. 2015

J Virol

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“…In this instance, all the cultures had a slightly higher incidence of floating cells, and this was reflected by median clone-size of eight cells, seven cells, seven cells, and nine cells for empty vector-, wild-type-, progerin-, and L647R lamin A-transduced cells, respectively. This suggests that p53 may be involved in suppressing clonal outgrowth in progerin-and L647R-expressing cells, although E6 is reported to have p53-independent functions as well (Klingelhutz et al, 1996;Liu et al, 2007). In contrast, when AG13353 cells expressing HPV E7 were transduced with the lamin A mutants and assayed for clone-size distribution, we found only a marginal restoration of the clone-size distribution for progerin-and L647R-expressing cells ( Figure 5D and Table 1), suggesting that pRB function is not required for the impaired clonal outgrowth observed in progerin-or L647R-expressing cells.…”

Section: Pathways Altered During Cellular Immortalization Control Clomentioning

confidence: 99%

Suppression of Proliferative Defects Associated with Processing-defective Lamin A Mutants by hTERT or Inactivation of p53

Kudlow

Stanfel

Burtner

et al. 2008

MBoC

115

118

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Hutchinson-Gilford progeria syndrome (HGPS) is a rare, debilitating disease with early mortality and rapid onset of aging-associated pathologies. It is linked to mutations in LMNA, which encodes A-type nuclear lamins. The most frequent HGPS-associated LMNA mutation results in a protein, termed progerin, with an internal 50 amino acid deletion and, unlike normal A-type lamins, stable farnesylation. The cellular consequences of progerin expression underlying the HGPS phenotype remain poorly understood. Here, we stably expressed lamin A mutants, including progerin, in otherwise identical primary human fibroblasts to compare the effects of different mutants on nuclear morphology and cell proliferation. We find that expression of progerin leads to inhibition of proliferation in a high percentage of cells and slightly premature senescence in the population. Expression of a stably farnesylated mutant of lamin A phenocopied the immediate proliferative defects but did not result in premature senescence. Either p53 inhibition or, more surprisingly, expression of the catalytic subunit of telomerase (hTERT) suppressed the early proliferative defects associated with progerin expression. These findings lead us to propose that progerin may interfere with telomere structure or metabolism in a manner suppressible by increased telomerase levels and possibly link mechanisms leading to progeroid phenotypes to those of cell immortalization. INTRODUCTIONThe nuclear lamins are broadly expressed and constitute the only intermediate filament proteins localized to the nucleus (Smith et al., 2005;Bridger et al., 2007;Dechat et al., 2008). Given the ability of lamins to form stable polymers resulting from coiled-coil interactions, they have typically been ascribed a structural role in the nucleus (McKeon et al., 1986;Lammerding et al., 2004Lammerding et al., , 2006; however, a variety of regulatory roles have also been proposed (Spann et al., 1997;Spann et al., 2002;Frock et al., 2006;Ivorra et al., 2006;Nitta et al., 2006Nitta et al., , 2007Scaffidi and Misteli, 2008). The two classes of lamins, B-type and A-type (of which lamin A and lamin C are the most prominent), have different patterns of expression. Whereas, isoforms of lamin B are expressed in all cells throughout development, lamins A and C (lamin A/C) are not expressed early in development. Instead, their expression begins during midgestation and is most prominent in differentiating and terminally differentiated cells (Rober et al., 1989).Mutations in LMNA (encoding all A-type lamins) are associated with at least 12 different human genetic disorders (Kudlow et al., 2007). Of these, at least three have features reminiscent of premature aging. The most common LMNAassociated premature aging-like syndrome, Hutchinson-Gilford progeria syndrome (HGPS), is often caused by a single nucleotide change in exon 11 of the LMNA gene (Cao and Hegele, 2003;De Sandre-Giovannoli et al., 2003;Eriksson et al., 2003). This mutation, generally referred to as G608G, is silent with regard to the coded a...

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Decreased local immune response and retained HPV gene expression during chemoradiotherapy are associated with treatment resistance and death from cervical cancer

Cosper

McNair

González

et al. 2019

Intl Journal of Cancer

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More than one-third of patients with locally advanced cervical cancer do not respond to chemoradiation therapy (CRT). We aimed to characterize the transcriptional landscape of paired human cervical tumors before and during CRT in order to gain insight into the evolution of treatment response and to elucidate mechanisms of treatment resistance. We prospectively collected cervical tumor biopsies from 115 patients both before and 3 weeks into CRT. RNA-sequencing, Gene Set Enrichment Analysis and HPV gene expression were performed on 20 paired samples that had adequate neoplastic tissue mid-treatment. Tumors from patients with no evidence of disease (NED) at last follow-up had enrichment in pathways related to the immune response both pretreatment and mid-treatment, while tumors from patients dead of disease (DOD) demonstrated enrichment in biosynthetic and mitotic pathways but not in immune-related pathways. Patients DOD had decreased expression of T-cell and cytolytic genes and increased expression of PD-L2 mid-treatment compared to patients NED. Histological and immunohistochemical analysis revealed a decrease in tumor-associated lymphocytes (TAL) during CRT in all patients but tumors from patients DOD had a significantly more pronounced decrease in TALs and CD8+ cells mid-treatment, which was validated in a larger mid-treatment cohort. Finally, patients DOD retained more HPV E6/E7 gene expression during CRT and this was associated with increased expression of genes driving mitosis, which was corroborated in vitro. Our results suggest that decreased local immune response and retained HPV gene expression may be acting together to promote treatment resistance during CRT in patients with cervical cancer.Additional Supporting Information may be found in the online version of this article.

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p53-Independent Abrogation of a Postmitotic Checkpoint Contributes to Human Papillomavirus E6-Induced Polyploidy

Cited by 46 publications

References 43 publications

Role of Cdk1 in the p53-Independent Abrogation of the Postmitotic Checkpoint by Human Papillomavirus E6

Role of Cdk1 in the p53-Independent Abrogation of the Postmitotic Checkpoint by Human Papillomavirus E6

Suppression of Proliferative Defects Associated with Processing-defective Lamin A Mutants by hTERT or Inactivation of p53

Decreased local immune response and retained HPV gene expression during chemoradiotherapy are associated with treatment resistance and death from cervical cancer

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