The human papillomavirus E6 and E7 inducible oncogene, hWAPL, exhibits potential as a therapeutic target

WAPL induces cervical intraepithelial neoplasia modulated with estrogen signaling without HPV E6/E7

Since cervical cancer still afflicts women around the world, it is necessary to understand the underlying mechanism of cervical cancer development. Infection with HPV is essential for the development of cervical intraepithelial neoplasia (CIN). In addition, estrogen receptor signaling is implicated in the development of cervical cancer. Previously, we have isolated human wings apart-like (WAPL), which is expected to cause chromosomal instability in the process of HPV-infected precancerous lesions to cervical cancer. However, the role of WAPL in the development of CIN is still unknown. In this study, in order to elucidate the role of WAPL in the early lesion, we established WAPL overexpressing mice (WAPL Tg mice) and HPV E6/E7 knock-in (KI) mice. WAPL Tg mice developed CIN lesion without HPV E6/E7. Interestingly, in WAPL Tg mice estrogen receptor 1 (ESR1) showed reduction as compared with the wild type, but cell growth factors MYC and Cyclin D1 controlled by ESR1 expressed at high levels. These results suggested that WAPL facilitates sensitivity of ESR1 mediated by some kind of molecule, and as a result, affects the expression of MYC and Cyclin D1 in cervical cancer cells. To detect such molecules, we performed microarray analysis of the uterine cervix in WAPL Tg mice, and focused MACROD1, a co-activator of ESR1. MACROD1 expression was increased in WAPL Tg mice compared with the wild type. In addition, knockdown of WAPL induced the downregulation of MACROD1, MYC, and Cyclin D1 but not ESR1 expression. Furthermore, ESR1 sensitivity assay showed lower activity in WAPL or MACROD1 downregulated cells than control cells. These data suggested that WAPL increases ESR1 sensitivity by activating MACROD1, and induces the expression of MYC and Cyclin D1. Therefore, we concluded that WAPL not only induces chromosomal instability in cervical cancer tumorigenesis, but also plays a key role in activating estrogen receptor signaling in early tumorigenesis.

Clinical significance of hWAPL polymorphisms in the risk of cervical carcinogenesis

To investigate the clinical significance of human wings apart-like (hWAPL) genetic polymorphisms in cervical carcinogenesis. hWAPL polymorphisms and human papillomavirus (HPV) types were examined in 175 cervical smears of exfoliated cervical cell samples using a real-time polymerase chain reaction system. A significant difference was detected in the frequency of the CC genotype between the HPV(+) low-grade squamous intraepithelial lesion (LSIL) and high-grade squamous intraepithelial lesion (HSIL) groups [Odds ratio 0.21, 95% confidence interval (CI) 0.0723-0.61; P = 0.0029]. A significant difference was noted in the frequency of the CC genotype between the high-risk HPV-positive LSIL and HSIL groups (odds ratio 0.2955, 95% CI 0.0893-0.9771; P = 0.0414). The CC genotype of hWAPL gene promoter polymorphism may be associated with cervical carcinogenesis.

TAT-mediated si-hWAPL inhibits the invasion and metastasis of cervical cancer stem cells

Human wings apart-like (hWAPL) is reported to have an association with cervical cancer. In the present study, the role of hWAPL in cervical cancer stem cells (CCSCs) was evaluated. Cervical tumorspheres were generated from cervical cancer tissues cultured in stem cell medium, and the expression of hWAPL by the tumorspheres was detected using immunohistochemistry. hWAPL expression levels in the tumorspheres were then upregulated using hWAPL adenoviral vectors or downregulated via the TAT-mediated knockdown of hWAPL and the effects on the tumorspheres were evaluated using colony formation, cell invasion and western blotting assays. The results demonstrated that the expression of hWAPL and human papillomavirus (HPV) was associated with the pluripotency of CCSCs, with hWAPL expression decreasing following the differentiation of cervical tumorspheres. Knockdown of hWAPL expression decreased HPV E6 expression and inhibited tumor invasion and colony formation. TAT-mediated knockdown of hWAPL with short interfering RNA significantly reduced tumor growth in nude mice. These results suggest that hWAPL is a marker of CCSC proliferation and is potentially a therapeutic target for cervical carcinoma through the downregulation of HPV E6.

Human wings apart-like gene is specifically overexpressed in cervical cancer

Cervical cancer is the third most commonly diagnosed cancer in women. The human wings apart-like (hWAPL) gene, which is 30,793 bp long and located on 10q23.2., is a human homologue of the WAPL gene in Drosophila melanogaster. hWAPL has the characteristics of an oncogene in uterine cervical cancer. The present study investigated the expression of the hWAPL gene in tissues, including 9 common cancers, consisting of cervical, gastric and lung cancers, liver, bladder, esophageal, endometrial, renal and rectal carcinomas, cervical intraepithelial neoplasia (CIN) and benign squamous epithelia. The immunohistochemical analysis was conducted using paraffin-embedded tissues obtained from 413 patients, consisting of 27 benign squamous epithelial tissue samples, and 47 cervical cancer, 30 cervical intraepithelial neoplasia (CIN)I, 33 CINII, 38 CINIII, 29 gastric cancer, 28 liver carcinoma, 26 bladder carcinoma, 35 esophageal carcinoma, 25 endometrial, 26 renal carcinoma, 36 rectal carcinoma and 33 lung cancer tissues. The expression of hWAPL mRNA was evaluated by reverse transcription-quantitative polymerase chain reaction in 8 benign squamous epithelia and 11 cervical cancer tissues. Compared to benign squamous epithelia and the 8 other cancers, hWAPL protein was significantly increased in cervical cancer (P<0.001). The expression of the hWAPL protein in cervical cancer and CINIII tissues was markedly increased compared to the expression in CINI and CINII tissues (P<0.001). Despite the significant difference in the staining scores (P<0.001), no significant difference was observed in the percentage of tissues expressing hWAPL (P=0.102) between cervical cancer and CINIII. The hWAPL gene may therefore be specifically overexpressed in cervical cancer. The overexpression of hWAPL may play an important role in occurrence and development of cervical cancer.

C3-Luc Cells Are an Excellent Model for Evaluation of Cellular Immunity following HPV16L1 Vaccination

C3 and TC-1 are the two model cell lines most commonly used in studies of vaccines and drugs against human papillomavirus (HPV) infection. Because C3 cells contain both the HPV16 E and L genes, but TC-1 cells contain only the HPV16 E genes, C3 cells are usually used as the model cell line in studies targeting the HPV16 L protein. However, expression of the L1 protein is difficult to detect in C3 cells using common methods. In our study, Short tandem repeat analysis (STR) was used to demonstrate that C3 cells are indeed derived from mice, PCR results show that HPV16 L1, E6 and E7 genes were detected in C3 genomic DNA, and RT-PCR results demonstrated that L1 transcription had occurred in C3 cells. However, the expression of C3 protein was not found in the results of western blot and immunohistochemistry (IHC). Growth and proliferation of C3 were inhibited by mice spleen lymphocytes that had been immunized with a vaccine against HPV16L1. The luciferase gene was integrated into C3 cells, and it was confirmed that addition of the exogenous gene had no effect on C3 cells by comparing cell growth and tumor formation with untransformed cells. Cells stably expressing luciferase (C3-luc) were screened and subcutaneously injected into the mice. Tumors became established and were observed using a Spectrum Pre-clinical in Vivo Imaging System. Tumor size of mice in the different groups at various time points was calculated by counting photons. The sensitivity of the animals to the vaccine was quantified by statistical comparison. Ten or 30 days following injection of the C3-luc cells, tumor size differed significantly between the PBS and vaccine groups, indicating that C3 cells were susceptible to vaccination even after tumors were formed in vivo.

Relationship between hWAPL polymorphisms and cervical cancer susceptibility

PURPOSE

To analyze the correlation of the polymorphisms of human wing-apart like (hWAPL) gene (rs7083506 and rs11202058) with the susceptibility to cervical cancer. Besides, the relationship of haplotypes between the polymorphisms with cervical cancer susceptibility was analyzed.

METHODS

Taqman probe genotyping method was adopted to detect the genotype distribution of hWAPL rs7083506 and rs11202058 polymorphisms in 117 cervical cancer patients and 128 healthy controls. Linkage disequilibrium and haplotypes were analyzed by Haploview software. χ(2) test was utilized to analyze the differences of genotype, allele and haplotype frequencies between the case and control groups.

RESULTS

Correlation analysis of hWAPL rs7083506 and rs11202058 polymorphisms with cervical cancer susceptibility was based on the five genetic models. TT genotype of rs7083506 increased the susceptibility of cervical cancer in TT vs. CC model and TT vs. CT+TT model (OR=2.249, 95% CI=1.018-4.970; OR=2.287, 95% CI=1.069-4.896). For rs11202058, the A allele increased the cervical cancer susceptibility (A vs. G, OR=1.502, 95% CI=1.005-2.245). No significant correlation was observed between rs11202058 genotypes and cervical cancer susceptibility. We performed the haplotype analysis between the two polymorphisms, and found that T-A haplotype significantly correlated with cervical cancer, the susceptibility of cervical cancer increased to 1.78 times.

CONCLUSIONS

Rs7083506 and rs11202058 polymorphisms of hWAPL and their haplotype T-A were associated with cervical cancer.

Transcriptional gene silencing of HPV16 E6/E7 induces growth inhibition via apoptosis in vitro and in vivo

OBJECTIVE

Transcriptional silencing of HPV oncogenes using short interfering RNA (siRNA) blocks E6/E7 expression. Our objective was to estimate the effective value of E6/E7 specific siRNA-induced transcriptional gene silencing as a potential therapeutic strategy for cervical cancer.

METHODS

In vitro studies were performed by employing two categories of siRNA targeting promoter of E6/E7 gene and E7 transcript, respectively, and inhibitory effect of both siRNAs was further observed in vitro and on xenograft in BALB/c mice that were inoculated with siRNA transfected SiHa cells and parental SiHa cells followed by siRNA intratumoral injection in vivo. Tumor volume and growth curves were assessed. Furthermore, cellular proliferation and apoptosis of inoculated tumors were determined by immunohistochemistry staining and TUNEL assay.

RESULTS

The two most active siRNA sequences specifically knockdown E6/E7 expressions at mRNA level in HPV16 positive Siha cells, increased p53 and decreased p16 expressions at protein level, inhibited cell proliferation, and induced cell apoptosis in vitro. Furthermore, both siRNAs effectively inhibited tumor formation and growth no matter in mice with siRNA transfected cells in vitro or with siRNA intratumoral injection in vivo. TUNEL staining and FCM assay consistently showed that tumor retardation was through induction of cellular apoptosis.

CONCLUSION

RNAi targeting the promoter of HPV16 E6/E7 acts effectively in vitro and in vivo, especially through intratumoral delivery, and may be a candidate therapeutic strategy for cervical cancer.

Cornelia de Lange syndrome, cohesin, and beyond

Cornelia de Lange syndrome (CdLS) (OMIM #122470, #300590 and #610759) is a dominant genetic disorder with multiple organ system abnormalities which is classically characterized by typical facial features, growth and mental retardation, upper limb defects, hirsutism, gastrointestinal and other visceral system involvement. Mutations in three cohesin proteins, a key regulator of cohesin, NIPBL, and two structural components of the cohesin ring SMC1A and SMC3, etiologically account for about 65% of individuals with CdLS. Cohesin controls faithful chromosome segregation during the mitotic and meiotic cell cycles. Multiple proteins in the cohesin pathway are also involved in additional fundamental biological events such as double-strand DNA break repair and long-range regulation of transcription. Moreover, chromosome instability was recently associated with defective sister chromatid cohesion in several cancer studies, and an increasing number of human developmental disorders is being reported to result from disruption of this pathway. Here, we will discuss the human disorders caused by alterations of cohesin function (termed 'cohesinopathies'), with an emphasis on the clinical manifestations of CdLS and mechanistic studies of the CdLS-related proteins.

Gene silencing with siRNA targeting E6/E7 as a therapeutic intervention in a mouse model of cervical cancer

OBJECTIVE

Selective silencing of HPV oncogenes using short interfering RNA (siRNA) blocks E6/E7 expression and restores normal p53 and Rb function. Our objective was to determine if siRNA targeting E6/E7 would inhibit the growth of established tumors in a mouse model of cervical cancer.

METHODS

In vitro studies were performed using unique siRNA sequences to confirm their ability to target and reduce E6/E7 mRNA and restore functioning p53. Next, siRNA targeting lamin was injected daily for three days into tumors established from HPV 16 positive CaSki human cervical cancer cells. Immunohistochemistry and branched DNA gene quantification were used to determine distribution and duration of activity of these siRNA. For our therapeutic studies tumors were directly injected with siRNA targeting E6/E7, non-targeting control siRNA, or saline. In preliminary experiments injections were daily or every three days for a total of three doses. A second therapeutic experiment utilized every three day dosing for 35 days. Tumor volume, growth curves and E7 mRNA levels were assessed.

RESULTS

The two most active siRNA sequences resulted in a 67% and 71% reduction in E6/E7 mRNA. Fluorescent lamin siRNA was visualized up to 120 h after the initial tumor injection and was evenly distributed throughout the tumors. IHC showed lamin expression to be inhibited by 68% and 75% when compared to controls at 54 and 120 h respectively. In our preliminary therapeutic intervention experiments there was no significant difference in tumor growth between the treatment groups when mice were treated with three daily injections (p=0.41). However, when treated every third day for three injections final tumor volume was less in animals injected with siRNA sequences A (78% reduction; p<0.0001) and G (60% reduction; p=0.005) compared to saline injection. Tumors showed a corresponding decrease in E6/E7 mRNA. Extended treatment with siRNA completely or nearly eradicated tumors in 70% of the animals.

CONCLUSION

Therapeutic siRNA targeting E6/E7 significantly inhibits tumor growth in this mouse model of cervical cancer. Further investigation is needed to determine optimal dosing and route of delivery.

Expression of various types of alternatively spliced WAPL transcripts in human cervical epithelia

We have previously identified a novel gene WAPL that is inducible by human papillomavirus (HPV) E6 and E7 oncoproteins, and is associated with uterine cervical carcinogenesis. A WAPL splice variant named Friend of EBNA2 (FOE) has also been characterized as a binding partner of the Epstein-Barr virus transformation-related protein EBNA2. On the other hand, recent studies have revealed that WAPL is a cohesin-binding protein and promotes sister-chromatid resolution in mitotic prophase. These data demonstrate that WAPL plays an important role in tumorigenesis and cell cycle progression. In this study, we have isolated a large number of additional alternatively spliced WAPL variants from various cervical epithelia. Each variant consists of a variable 5'-terminal region and the conserved remainder. In addition, we have confirmed the genomic organization of the 5'-region of the WAPL gene, and have investigated the characteristic features of the WAPL variants and their products. Furthermore, we have determined the HPV types of the expressed E6/E7 transcripts in the cervical epithelia with a novel PCR protocol. These results should shed light on a novel aspect of WAPL function.

Immunization of mice with plasmids coexpressing HPV16 E5 and the novel oncogene hWAPL

The novel human oncogene hWAPL is associated with uterine cervical cancer. The HPV16 E5 oncoprotein could induce genomic instability in normal human cells. However, the mechanism of E5 interaction with hWAPL still awaits definition. In our present studies, the eukaryotic expression plasmids, pcDNA3-hWAPL and pcDNA3-hWAPL-E5 were constructed and carried out to vaccinate mice directly. The result that indicated the polyclonal antibody titer in immunized mice sera was increased by enzyme-linked immunosorbent assay. In addition, the proliferative responses of immunized mice spleen cells showed the optical densities values in vaccinated group remarkably higher than that in the control group. In conclusion, the recombinant plasmids could induce strong humoral and cellular immune response and exhibited great potential as therapeutic targets in the treatment of cervical cancer. However, the result didn't show significant difference in group with coexpression of HPV16 E5-hWAPL and group with only hWAPL expression. Consistent with these observations, we demonstrated that HPV16 E5 was not the optimal factor to cooperate with hWAPL in gene therapy.

Unscheduled overexpression of human WAPL promotes chromosomal instability

Previously, we have isolated and characterized a novel human gene termed human WAPL that has the characteristics of an oncogene in uterine cervical cancer. WAPL is inducible by human papillomavirus (HPV) E6 and E7 oncoproteins. On the other hand, recent studies have revealed that WAPL regulates sister chromatid resolution by controlling the association of cohesin and chromatin. However, the effects of WAPL overexpression on cervical carcinogenesis are still unclear. Here, we show that WAPL overexpression induces generation of multinucleated cells. In addition, WAPL-overexpressing cells demonstrated increases in chromatid breaks in comparison with control cells. These results were obtained even in HPV-negative cell lines. High frequent premature sister separation by disregulation of cohesin may lead to these results. Thus, our study suggests that unscheduled overexpression of WAPL disturbs mitosis and cytokinesis, and contributes to tumor progression by induction of chromosomal instability (CIN).