Establishment and characterization of a human-papillomavirus negative, p53-mutation negative human cervical cancer cell line

Establishment, authenticity, and characterization of cervical cancer cell lines

Cell lines have been considered excellent research models in many areas of biomedicine and, specifically, in the study of carcinogenesis. However, they cease to be effective models if their behavior changes. Although studies on the cross-contamination of cell lines originating from different tissues have been performed, little is known about cell lines derived from cervical neoplasia. We know that high-risk HPV (HR-HPV) is associated with the development of this type of cancer. This link between HPV infection and cancer was first established over 35 years ago when HPV16 DNA was found to be present in a large proportion of cervical cancer biopsies. The present review paper aims to report the status of the establishment, authenticity, and characterization of cervical cancer (CC) cell lines. This is a systematic review of articles on the establishment, authenticity, and characterization of CC cell lines, published from 1960 to date in the databases and in cell repository databases. 52 cell lines were identified in the literature. Only 25 cell lines were derived from cervical neoplasia, of which only 45.8% have a reported identity test (genomic fingerprint). Despite the increase in the establishment of cell lines of cervical neoplasia and the standards for the regulation of these study models, the criteria for their characterization continue to be diverse.

Down-regulation of lncRNA PCGEM1 inhibits cervical carcinoma by modulating the miR-642a-5p/LGMN axis

LncRNA PCGEM1 (PCGEM1) has been reported to exert essential effects on the development and progress of various tumors, while the detailed effects and possible mechanisms of PCGEM1 in cervical carcinoma remain unknown. In the present study, PCGEM1 was over-expressed in cervical carcinoma cells as evidenced by real-time quantitative polymerase chain reaction (RT-qPCR) assay. Knockdown of PCGEM1 significantly repressed proliferation, migration, and invasion, while induced G1 arrest in cervical carcinoma cells. In addition, PCGEM1 was predicted to target miR-642a-5p by bioinformatics software, which was further confirmed by luciferase reporter assay. Besides, RT-qPCR assay indicated that miR-642a-5p expression was decreased in cervical carcinoma cells and knockdown of PCGEM1 could accelerate miR-642a-5p expression. Moreover, inhibition of miR-642a-5p partly abolished the functions of PCGEM1 knockdown on proliferation, cell cycle, migration and invasion of cervical carcinoma cells. Furthermore, miR-642a-5p could bind to the 3'-UTR of LGMN, which was over-expressed in the cervical carcinoma cells. Suppression of LGMN partly restored the functions of miR-642a-5p inhibitor on proliferation, cell cycle distribution, migration and invasion in the cervical carcinoma cells treated with the PCGEM1 shRNA. Taken together, our data indicated that knockdown of PCGEM1 inhibited proliferation, migration and invasion in cervical carcinoma by modulating the miR-642a-5p/ LGMN axis.

Loss of the respiratory enzyme citrate synthase directly links the Warburg effect to tumor malignancy

To investigate whether altered energy metabolism induces the Warburg effect and results in tumor malignancy, the respiratory enzyme citrate synthase (CS) was examined, silenced, and the effects analyzed. In human cervical carcinoma cells, RNAi-mediated CS knockdown induced morphological changes characteristic of the epithelial-mesenchymal transition (EMT). This switch accelerated cancer cell metastasis and proliferation in in vitro assays and in vivo tumor xenograft models. Notably, CS knockdown cells exhibited severe defects in respiratory activity and marked decreases in ATP production, but great increases in glycolytic metabolism. This malignant progression was due to activation of EMT-related regulators; altered energy metabolism resulted from deregulation of the p53/TIGAR and SCO2 pathways. This phenotypic change was completely reversed by p53 reactivation via treatment with proteasome inhibitor MG132 or co-knockdown of E3 ligase HDM2 and partially suppressed by ATP treatment. This study directly links the Warburg effect to tumor malignancy via induction of the EMT phenotype.

The role of human papillomavirus type 16 E6/E7 oncoproteins in cervical epithelial-mesenchymal transition and carcinogenesis

Cervical cancer is the most common malignancy in females worldwide. This study investigated the prevalence of the E6/E7 oncoproteins of human papillomavirus (HPV) type 16, which are important in fibroblast growth factor (FGF) 2- and 4-induced epithelial-mesenchymal transition (EMT) and cervical tumorigenesis. We investigated the functional interaction between HPV16 E6/E7-transfected Cx cells (CxWJ cells) and treatment with FGF2 and 4, according to the expression of α-smooth muscle actin (α-SMA), vimentin and E-cadherin protein as well as cell growth and invasive ability. The results showed the upregulation of α-SMA and vimentin and the downregulation of E-cadherin protein expression in CxWJ cells. HPV16 E6/E7 infection partially repressed proliferation, but not the invasive ability of FGF2 or FGF4 stimulation in cervical cancer cells (CxWJ cells). These data provide evidence of a functional interaction between HPV16 E6/E7 and FGFs 2 and 4, suggesting that cooperative stimulation of HPV E6/E7 and FGFs activated in human cervical cancer cells is required to completely overcome the oncogenic function associated with the development of cervical epithelial-mesenchymal transition and tumorigenesis.

Conditionally replicating E1B-deleted adenovirus driven by the squamous cell carcinoma antigen 2 promoter for uterine cervical cancer therapy

Cervical cancer is the second most common type of malignant tumor among women worldwide. When the disease is confined locally, it can be controlled with surgical resection and radiotherapy. However, patients with recurrent or metastatic disease often have a poor prognosis. Measurement of serum levels of squamous cell carcinoma (SCC) antigens has been widely used as serological markers for SCC of uterine cervix. Recently, it has been demonstrated that cervical cancer patients with elevated squamous cell carcinoma antigen-2 (SCCA2) expression in tumor cells carry a poor prognosis. Here, by using a luciferase reporter assay, we show that SCCA2 promoter was active in SCCA2-producing human cervical cancer cell lines, including Cx, Cxwj, SiHa and HeLa cells, but relatively quiescent in normal cervical epithelial cells. We then developed a conditionally replicating adenovirus, designated Ad-KFH, under the transcriptional control of the SCCA2 promoter. This E1B-55 kDa-deleted oncolytic adenovirus replicated specifically in and lysed SCCA2-producing cervical cancer cells. Furthermore, in a peritoneal metastatic tumor model, Ad-KFH retarded Cxwj tumor growth in NOD/severe combined immunodeficient mice and prolonged survival of tumor-bearing mice, especially when combined with cisplatin. These results suggest that Ad-KFH may provide a new strategy of gene therapy for advanced or recurrent uterine cervical cancer.

A functional interferon regulatory factor-1 (IRF-1)-binding site in the upstream regulatory region (URR) of human papillomavirus type 16

We recently identified a new enhancer element (HIRE-1, HPV-Interferon Responsive Element-1) in the upstream regulatory region (URR) of human papillomavirus (HPV) type 16. HIRE-1 is located upstream from and in close proximity to the TATA box. HIRE-1 is 1 nt shorter in its 5' sequence in comparison to a consensus IRF-1 binding site (IRF-E). Gel shift analyses clearly demonstrated that HIRE-1 is capable of binding IRF-1 in response to interferon-gamma (IFN-gamma) treatment. In a reporter system, HIRE-1 stimulated transcription in response to IRF-1 or IFN gamma from both a heterologous or the homologous (p97) promoter in a dose-dependent manner. Mutations in the core binding sequence strongly decreased this enhancer activity. Interestingly, HIRE-1 stimulated transcription in the context of the full URR in a cell-type-specific manner, thereby suggesting the role of other cell-type-specific factors that might counteract with its function. Thus, our results may explain the inconsistent clinical and experimental results observed following IFN treatment of cervical lesions or cells. Also, this new enhancer may have an important function during inflammatory responses against HPV type 16.