Molecular genetics of human cervical cancer: role of papillomavirus and the apoptotic cascade

Episome partitioning and symmetric cell divisions: Quantifying the role of random events in the persistence of HPV infections

Human Papillomaviruses (HPV) are one of the most prevalent sexually transmitted infections (STI) and the most oncogenic viruses known to humans. The vast majority of HPV infections clear in less than 3 years, but the underlying mechanisms, especially the involvement of the immune response, are still poorly known. Building on earlier work stressing the importance of randomness in the type of cell divisions in the clearance of HPV infection, we develop a stochastic mathematical model of HPV dynamics that combines the previous aspect with an explicit description of the intracellular level. We show that the random partitioning of virus episomes upon stem cell division and the occurrence of symmetric divisions dramatically affect viral persistence. These results call for more detailed within-host studies to better understand the relative importance of stochasticity and immunity in HPV infection clearance.

Every year, infections by Human Papillomaviruses (HPV) are responsible for a large share of infectious cancers. The prevalence of HPVs is very high, which makes it a major public health issue. Fortunately, most HPV infections (80 to 90%) are cleared naturally within three years. Among the few that persist into chronic infections, the majority also naturally regress. Hence for a given HPV infection, the risk of progression towards cancerous status is low. The immune response is often invoked to explain HPV clearance in non-persisting infections, but many uncertainties remain. Besides immunity, randomness was also suggested to play an important role. Here, we examine how random events occurring during the life cycle of the virus could alter the persistence of the virus inside the host. We develop a mechanistic model that explicitly follows the dynamic of viral copies inside host cells, as well as the dynamics of the epithelium. In our model, infection extinction occurs when all viral copies end up in differentiated cells and migrate towards the surface. This can happen upon cell division during the random allocation of the episomes (i.e. independent circular DNA copies of the viral genome) or when a stem cell divides symmetrically to generate two differentiated cells. We find that the combination of these random events drastically affects infection persistence. More generally, the importance of random fluctuations could match that of immunity and calls for further studies at the within-host and the epidemiological level.

Exploration of the molecular mechanisms of cervical cancer based on mRNA expression profiles and predicted microRNA interactions

The molecular mechanisms of cervical cancer have been minimally explored with multi-omics data. In the present study, mRNA expression profiles were analyzed and combined with predicted miRNA interactions to contribute to the characterization of the underlying regulatory mechanisms of cervical cancer. A total of 92 significantly differentially expressed genes (DEGs) were identified in 33 tumor samples by comparison with 29 normal samples. mRNA-miRNA interaction network analysis revealed that 16 out of the 92 DEGs, including checkpoint kinase 1 (CHEK1), SRY-box 17 (SOX17), centrosomal protein 55, cyclin dependent kinase inhibitor 2A (CDKN2A), and inhibitor of DNA binding 4, were the targets of 4 miRNAs which were previously reported to be involved in the regulation of cervical cancer. Tumor and normal samples could be distinctly classified into two groups based on the expression of the 16 DEGs. Furthermore, survival analysis using the SurvExpress database indicated that the 16 DEGs could individually significantly differentiate low- and high-risk cervical cancer groups. Overall, multiple biological processes are likely to participate in the progression of cervical cancer based on the pathway and function enrichment identified for the DEGs. The dysregulation of SOX17 is associated with the regulation of embryonic development, the determination of cell fate and likely promotes cancer cell transformation. The dysregulation of CHEK1 and CDKN2A further promote cancer cell proliferation by affecting the cell cycle checkpoint in response to DNA damage. The identification of critical genes and biological processes associated with cervical cancer may be beneficial for the exploration of the molecular mechanisms.

Human papilloma virus: Apprehending the link with carcinogenesis and unveiling new research avenues (Review)

Human papilloma viruses (HPV) are a small group of non‑enveloped viruses belonging to the Papillomaviridae family with strong similarities to polyoma viruses. The viral particles consist of a genome in the form of a circular double‑stranded DNA, encompassing eight open reading frames, as well as a non‑enveloped icosahedral capsid. HPV infection is considered the most common sexually transmitted disease in both sexes and is strongly implicated in the pathogenesis of different types of cancer. 'High‑risk' mucosal HPV types, predominantly types 16, 18, 31, 33 and 35, are associated with most cervical, penile, vulvar, vaginal, anal, oropharyngeal cancers and pre‑cancers. Screening for HPV is necessary for the prognosis and for determining treatment strategies for cancer. Novel HPV markers, including proteomic and genomic markers, as well as anti‑papillomavirus vaccines are currently available. The aim of this comprehensive review was to thoroughly present the updated information on virus development, cancer occurrence, treatment and prevention strategies, in an attempt to shed further light into the field, including novel research avenues.

FOXM1 (Forkhead box M1) in tumorigenesis: overexpression in human cancer, implication in tumorigenesis, oncogenic functions, tumor-suppressive properties, and target of anticancer therapy

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor and is also intimately involved in tumorigenesis. FOXM1 stimulates cell proliferation and cell cycle progression by promoting the entry into S-phase and M-phase. Additionally, FOXM1 is required for proper execution of mitosis. In accordance with its role in stimulation of cell proliferation, FOXM1 exhibits a proliferation-specific expression pattern and its expression is regulated by proliferation and anti-proliferation signals as well as by proto-oncoproteins and tumor suppressors. Since these factors are often mutated, overexpressed, or lost in human cancer, the normal control of the foxm1 expression by them provides the basis for deregulated FOXM1 expression in tumors. Accordingly, FOXM1 is overexpressed in many types of human cancer. FOXM1 is intimately involved in tumorigenesis, because it contributes to oncogenic transformation and participates in tumor initiation, growth, and progression, including positive effects on angiogenesis, migration, invasion, epithelial-mesenchymal transition, metastasis, recruitment of tumor-associated macrophages, tumor-associated lung inflammation, self-renewal capacity of cancer cells, prevention of premature cellular senescence, and chemotherapeutic drug resistance. However, in the context of urethane-induced lung tumorigenesis, FOXM1 has an unexpected tumor suppressor role in endothelial cells because it limits pulmonary inflammation and canonical Wnt signaling in epithelial lung cells, thereby restricting carcinogenesis. Accordingly, FOXM1 plays a role in homologous recombination repair of DNA double-strand breaks and maintenance of genomic stability, that is, prevention of polyploidy and aneuploidy. The implication of FOXM1 in tumorigenesis makes it an attractive target for anticancer therapy, and several antitumor drugs have been reported to decrease FOXM1 expression.

The biology and life-cycle of human papillomaviruses

Human papillomaviruses (HPVs) comprise a diverse group, and have different epithelial tropisms and life-cycle strategies. Many HPVs are classified as low-risk, as they are only very rarely associated with neoplasia or cancer in the general population. These HPVs typically cause inapparent/inconspicuous infections, or benign papillomas, which can persist for months or years, but which are eventually resolved by the host's immune system. Low-risk HPVs are difficult to manage in immunosuppressed people and in individuals with genetic predispositions, and can give rise to papillomatosis, and in rare instances, to cancer. The high-risk HPV types are, by contrast, a cause of several important human cancers, including almost all cases of cervical cancer, a large proportion of other anogenital cancers and a growing number of head and neck tumours. The high-risk HPV types constitute a subset of the genus Alphapapillomavirus that are prevalent in the general population, and in most individuals cause only inconspicuous oral and genital lesions. Cancer progression is associated with persistent high-risk HPV infection and with deregulated viral gene expression, which leads to excessive cell proliferation, deficient DNA repair, and the accumulation of genetic damage in the infected cell. Although their life-cycle organisation is broadly similar to that of the low-risk HPV types, the two groups differ significantly in their capacity to drive cell cycle entry and cell proliferation in the basal/parabasal cell layers. This is thought to be linked, at least in part, to different abilities of the high- and low-risk E6 proteins to modulate the activity of p53 and PDZ-domain proteins, and the differential ability of the E7 proteins to target the several different members of the retinoblastoma protein family. This article forms part of a special supplement entitled "Comprehensive Control of HPV Infections and Related Diseases" Vaccine Volume 30, Supplement 5, 2012.

Amplification of the human telomerase gene in liquid-based preparations is associated with cervical dysplasia and carcinoma

The aim of this study was to analyze the amplification of the human telomerase gene (TERC) in cervical specimens by fluorescence in situ hybridization (FISH), and FISH findings were compared with cytologic and histologic diagnoses. Slides prepared from 123 liquid-based preparations from cervical specimens with cytologic diagnoses of negative for squamous intraepithelial lesion or malignancy (n=20), atypical squamous cells of undetermined significance (n=22), low-grade squamous intraepithelial lesion (n=55), high-grade squamous intraepithelial lesion (n=21), or invasive cervical carcinomas (n=5) were analyzed for the amplification of TERC using a 2-color FISH probe. The results of the cytologic analysis and those of concurrent or subsequent biopsies were compared with the FISH findings. Results showed that amplification of TERC was significantly associated with both cytologic and histologic diagnoses (P<0.05). Patients with high-grade squamous intraepithelial lesion or squamous cell carcinoma cytology diagnoses had significantly higher percentages of cells with the amplification of TERC than did patients with low-grade squamous intraepithelial lesion, ASC-US, and negative for squamous intraepithelial lesion or malignancy (P<0.005). FISH can be performed on cervical liquid-based preparations to detect the amplification of TERC. This test may be an adjunct to cytology screening, early detection of cervix neoplasm, and may determine the progressive potential of individual lesions, especially in high-risk patients.

Clinical significance of hTERC gene amplification detection by FISH in the screening of cervical lesions

This study evaluated the clinical significance of hTERC gene amplification detection by fluorescence in situ hybridization (FISH) in the screening of cervical lesions. Cervical specimens of 50 high risk patients were detected by thin liquid-based cytology. The patients whose cytological results were classified as ASCUS or above were subjected to the subsequent colposcopic biopsies. Slides prepared from these 50 cervical specimens were analyzed for hTERC gene amplification using interphase FISH with the two-color hTERC probe. The results of the cytological analysis and those of subsequent biopsies, when available, were compared with the FISH-detected hTERC abnormalities. It was found that the positive rates of hTERC gene amplification in NILM, ASCUS, LSIL, HSIL, and SCC groups were 0.00, 28.57%, 57.14%, 100%, and 100%, respectively. The positive rates of hTERC gene amplification in HSIL and SCC groups were significantly higher than those in NILM, ASCUS and LSIL groups (all P<0.05). The mean percentages of cells with hTERC gene amplification in NILM, ASCUS, LSIL, HSIL, and SCC groups were 0.00, 10.50%, 36.00%, 79.00%, and 96.50%, respectively. Patients with HSIL or SCC cytological diagnoses had significantly higher mean percentages of cells with hTERC gene amplification than did patients with NILM, ASCUS or LSIL cytological diagnoses (all P<0.05). It was concluded that two-color interphase FISH could detect hTERC gene amplification to accurately distinguish HSIL and ISIL of cervical cells. It may be an adjunct to cytology screening, especially high-risk patients.

Requirement for estrogen receptor alpha in a mouse model for human papillomavirus-associated cervical cancer

The majority of human cervical cancers are associated with the high-risk human papillomaviruses (HPV), which encode the potent E6 and E7 oncogenes. On prolonged treatment with physiologic levels of exogenous estrogen, K14E7 transgenic mice expressing HPV-16 E7 oncoprotein in their squamous epithelia succumb to uterine cervical cancer. Furthermore, prolonged withdrawal of exogenous estrogen results in complete or partial regression of tumors in this mouse model. In the current study, we investigated whether estrogen receptor alpha (ERalpha) is required for the development of cervical cancer in K14E7 transgenic mice. We show that exogenous estrogen fails to promote either dysplasia or cervical cancer in K14E7/ERalpha-/- mice despite the continued presence of the presumed cervical cancer precursor cell type, reserve cells, and evidence for E7 expression therein. We also observed that cervical cancers in our mouse models are strictly associated with atypical squamous metaplasia (ASM), which is believed to be the precursor for cervical cancer in women. Consistently, E7 and exogenous estrogen failed to promote ASM in the absence of ERalpha. We conclude that ERalpha plays a crucial role at an early stage of cervical carcinogenesis in this mouse model.

Viral Helicases

Helicases are motor proteins that use the free energy of NTP hydrolysis to catalyze the unwinding of duplex nucleic acids. Helicases participate in almost all processes involving nucleic acids. Their action is critical for replication, recombination, repair, transcription, translation, splicing, mRNA editing, chromatin remodeling, transport, and degradation (Matson and Kaiser-Rogers 1990; Matson et al. 1994; Mendonca et al. 1995; Luking et al. 1998).

Induction of SiHa cells apoptosis by nanometer realgar suspension and its mechanism

The effects of nanometer realgar suspension on proliferation and apoptosis of human uterine cervix cancer cell line SiHa cells and oncogenic genes HPV16E6/E7 were investigated. A "micro-jet efflux" strategy was used for the preparation of nanometer realgar suspension. SiHa cells were treated with nanometer Realgar suspension in various concentrations (6.25, 12.5, 25 and 50 mg/L) for different durations (12, 24, 48 and 72 h). The inhibitive effect of nanometer realgar suspension on growth of SiHa cells was detected by MTT method. Special morphological changes of apoptosis were observed by transmission electron microscopy (TEM) and DNA fragments electrophoresis. The apoptotic rate was quantified by flow cytometry (FCM). The expression of HPV16E6/E7 mRNA and protein was assayed by RT-PCR and Western blot respectively. The results showed after being treated with 25 50 mg/L nanometer realgar suspension for 48 h, the survival rate of SiHa cells was decreased, and apoptotic rate markedly increased in a time-and concentration-dependent manner. TEM and DNA electrophoresis revealed the special morphological changes of apoptosis. The apoptotic rate of SiHa cells treated with nanometer realgar suspension was significantly higher than in the control group (P<0.01), and G(0)/G(1) phase arrest appeared following treatment with nanometer realgar suspension in 25 and 50 mg/L for 48 h. RT-PCR and Western blot assay indicated that nanometer realgar suspension reduced the HPV16E6/E7 gene expression. Nanometer realgar suspension could inhibit the proliferation and induce apoptosis of SiHa cells. The mechanism may be related to the down-regulation of the HPV16E6/E7 gene expression.

Gain of the 3q26 region in cervicovaginal liquid-based pap preparations is associated with squamous intraepithelial lesions and squamous cell carcinoma

BACKGROUND

Chromosomal aberrations have been documented in cervical carcinomas, especially chromosome 3q. The human telomerase RNA gene (hTERC) is located in the chromosome 3q26 region, and its product, telomerase, is involved in the maintenance of chromosome length and stability. Upregulation of telomerase is in general associated with tumorigenesis. In this study, cervicovaginal specimens were analyzed by fluorescence in situ hybridization (FISH) for gain of chromosome 3q26 containing hTERC, and FISH findings were compared with the cytologic and histologic diagnoses.

METHODS

Slides prepared from 66 liquid-based preparations from cervical specimens with cytologic diagnoses of negative for squamous intraepithelial lesion or malignancy (NILM, n=4), atypical squamous cells of undetermined significance (ASC-US, n=15), low-grade squamous intraepithelial lesion (LSIL, n=20), high-grade squamous intraepithelial lesion (HSIL, n=24), or cervical squamous cell carcinoma (SCCA, n=3) were analyzed for aberrations of 3q26 using a commercially available two-color FISH probe. The results of the cytologic analysis and those of concurrent or subsequent biopsies, when available, were compared with the FISH-detected 3q26 abnormalities. The Wilcoxon rank-sum test was used to assess associations between 3q26 gains and diagnoses.

RESULTS

Gain of 3q26 was significantly associated with the cytologic diagnosis (p<0.0001). Patients with HSIL or SCCA cytology diagnoses had significantly higher percentages of cells with 3q26 gain than did patients with NILM or ASC-US cytologic diagnoses.

CONCLUSIONS

FISH can be performed on cervicovaginal liquid-based preparations to detect gain of 3q26. Gain of 3q26 is associated with HSIL and SCCA. This test may be an adjunct to cytology screening, especially high-risk patients.

Cellular binding partners of the human papillomavirus E6 protein

The high-risk strains of human papillomavirus (HR-HPV) are known to be causative agents of cervical cancer and have recently also been implicated in cancers of the oropharynx. E6 is a potent oncogene of HR-HPVs, and its role in the progression to malignancy has been and continues to be explored. E6 is known to interact with and subsequently inactivate numerous cellular proteins pivotal in the mediation of apoptosis, transcription of tumor suppressor genes, maintenance of epithelial organization, and control of cell proliferation. Binding of E6 to these proteins cumulatively contributes to the oncogenic potential of HPV. This paper provides an overview of these cellular protein partners of HR-E6, the motifs known to mediate oncoprotein binding, and the agents that have the potential to interfere with E6 expression and activity and thus prevent the subsequent progression to oncogenesis.

HeLa cells treated with phytoglycoprotein (150 kDa) were killed by activation of caspase 3 via inhibitory activities of NF-kappaB and AP-1

The Solanum nigrum Linne (SNL) has been traditionally used as a herbal agent in folk medicine for various cancers in Korea. We found that the SNL glycoprotein consists of carbohydrate (69.74%) and protein content (30.26%), which has mainly the hydrophobic amino acids containing glycine and proline. With respect to its characters, we evaluated the apoptotic effects of glycoprotein isolated from SNL in human cervical cancer cell. In the activity of the apoptotic related proteins [cytochrome c, caspase 8, 3 and poly (ADP-ribose) polymerase (PARP)], the results showed that SNL glycoprotein (50 microg/ml) has a stimulatory effect on cytochrome c release into cytosol, caspase 8, 3 activation and PARP cleavage in HeLa cells. To verify the possible mechanism for apoptotic activity of SNL glycoprotein in HeLa cells, the binding activities of transcription factors (NF-kappaB and AP-1) and nitric oxide (NO) production was evaluated. The activities of NF-kappaB and AP-1 significantly decreased after SNL glycoprotein (50 microg/ml) treatment for 4 h, compare to the control. Interestingly, there was no difference of the DNA binding activity between NF-kappaB and AP-1. Also, nitric oxide (NO) production was significantly declined at 50 microg/ml SNL glycoprotein for 4 h. Therefore, we speculated that SNL glycoprotein exhibits inhibitory effect on HeLa cells via apoptosis, and it may be a potential candidate in field of anticancer drug discovery.

Fatores associados ao câncer do colo uterino em Propriá, Sergipe, Brasil

O câncer do colo uterino apresenta uma alta incidência nas regiões pobres dos países em desenvolvimento. Relaciona-se a fatores ligados ao estilo de vida que levam à infecção pelo Papilomavirus humano (HPV). O objetivo do estudo foi avaliar quais os fatores que favoreciam a infecção pelo HPV e ao desenvolvimento do carcinoma do colo uterino no Município de Própria, Sergipe, Brasil. Para o desenvolvimento da pesquisa, realizou-se um estudo de caso-controle, pareando-se quatro controles para cada caso quanto à idade, procedência e condição sócio-econômica. Foram identificadas vinte mulheres portadoras de carcinoma do colo uterino e oitenta controles. As mulheres do grupo casos apresentaram maior número de gestações e freqüência menor de realização de exame preventivo de rotina. Verificou-se também que as mulheres nos dois grupos tinham conhecimento pobre sobre o câncer e as suas formas de prevenção, alto índice de analfabetismo e os seus companheiros tinham múltiplas parceiras sexuais. O estudo concluiu que no Município de Própria, o maior número de gestações e a não realização de exames preventivos de rotina associaram-se à ocorrência de carcinoma do colo uterino.