Y Box-Binding Protein 1 Promotes Epithelial-Mesenchymal Transition, Invasion, and Metastasis of Cervical Cancer via Enhancing the Expressions of Snail.

OBJECTIVE: Y box-binding protein 1 (YB-1) is a potent oncogenic protein. How it regulates Snail in most tumors including cervical cancer is unknown. This article is to study if YB-1 plays a role in cervical cancer via regulating the expression of Snail. METHODS: Immunohistochemical staining of YB-1, Snail, and E-cadherin (E-cad) was performed on tissue specimens including 35 cases of chronic cervicitis (as a control), 35 cases of cervical intraepithelial neoplasm (CIN) I, 35 cases of CIN II/III, 28 cases of unmetastatic cervical squamous cell carcinoma, and 19 cases of metastatic cervical squamous cell carcinoma. RNA interference technique was used to knock down YB-1, E6, and Snail genes. Quantitative polymerase chain reaction, western blot, and transwell experiment were used to detect RNA, protein, and cell invasion of cervical cancer cell lines Hela and C33A, respectively. RESULTS: First, YB-1 knockdown significantly reduced messenger RNA (mRNA) and protein levels of Snail, followed by the increased mRNA and protein levels of E-cad and the decreased invasive ability in both Hela (human papillomavirus [HPV] 18+) and C33A (HPV-) cell lines. Second, YB-1 and Snail protein were correlatively expressed in the group order of metastatic cervical squamous cell carcinoma > unmetastatic cervical squamous cell carcinoma > CINs > cervicitis, with the inverse expression mode of E-cad in the group order, P value less than 0.01, between any 2 groups. Finally, HPV18 E6 knockdown reduced the mRNA and protein levels of YB-1 and Snail in Hela cells. CONCLUSIONS: The results firstly reported that YB-1 whose mRNA expression is regulated by HPV18 E6 promotes epithelial-mesenchymal transition and progression of cervical cancer via enhancing the expressions of Snail, which indicated that YB-1/Snail/epithelial-mesenchymal transition axis could have a potential use in the diagnosis and therapy of cervical cancer metastasis as a cancer marker and molecular target.

Clonality analysis of synchronous lesions of cervical carcinoma based on X chromosome inactivation polymorphism, human papillomavirus type 16 genome mutations, and loss of heterozygosity.

One of the most common forms of carcinoma in women, cervical invasive squamous cell carcinoma (CIC), often coexists with multiple lesions of cervical intraepithelial neoplasia (CIN). CIC and CIN show heterogeneity with respect to both histopathology and biology. To understand the causes, origin, and model of progression of cervical carcinoma, we assessed the clonality of a case with multiple synchronous lesions by analyzing X chromosome inactivation polymorphism, human papillomavirus type 16 (HPV16) sequence variation/mutations, and loss of heterozygosity (LOH). Microdissection was performed on 24 samples from this case, representing the entire lesional situation. The combination of different X chromosome inactivation patterns, two HPV16 point mutations, and LOH at three genomic microsatellite loci, led to the identification of five different "monoclonal" lesions (CIN II, CIN III, and invasive carcinoma nests) and five different "polyclonal" areas (CIN II and normal squamous epithelium). This finding indicated that CIC can originate from multiple precursor cells, from which some clones might progress via multiple steps, namely via CIN II and CIN III, whereas others might develop independently and possibly directly from the carcinoma precursor cells. Our results also supported the view that HPV16 as a "field factor" causes cervical carcinoma, which is probably promoted by the loss of chromosomal material as indicated by the LOH.

Positive Correlative over-Expression between eIF4E and Snail in Nasopharyngeal Carcinoma Promotes its Metastasis and Resistance to Cisplatin.

EIF4E is the rate-limiting factor in the mRNA translation of specific set of oncogenes. Snail is the core transcription factor of epithelial-mesenchymal transition (EMT), a key step of cancer metastasis. The connection between the two oncoproteins has not been well established in the human cancer tissues and in nasopharyngeal carcinoma (NPC). Here we showed that the positive correlative over-expression was seen between eIF4E and Snail in NPC tissues, and the expression was significantly higher in the metastatic NPC than in the un-metastatic NPC. In NPC cells, eIF4E knockdown significantly reduced Snail mRNA and protein levels, increased the mRNA level of E-cad (a direct downstream gene of Snail and a negative EMT marker), attenuated the invasive ability of the cells, and sensitized the cells to cisplatin in invasion. In contrast, enforced the expression of eIF4E significantly increased Snail mRNA and protein levels, and promoted the invasive ability in NPC cells. Under the condition of the high eIF4E expression, Snail knockdown significantly increased E-cad mRNA level and weaken the invasive ability of NPC cells. Finally, eIF4E directly bound Snail mRNA for translation initiation displayed by the RIP assay. Therefore, the results firstly suggested that eIF4E enhanced the Snail expression in both transcription and translation manner in human cancer tissues and targeting the eIF4E/Snail axis might intervene with the EMT and metastasis of NPC. This finding provided a new clue for further understanding the metastatic mechanism of human cancers and for preventing and treating NPC metastasis.

HPV18 E7 induces the over-transcription of eIF4E gene in cervical cancer.

OBJECTIVES: Eukaryotic translation initiation factor 4E (eIF4E) is overexpressed in cervical cancer (CC). However, the molecular mechanisms are unclear. This study aimed to investigate the molecular mechanism of eIF4E gene overexpression in CC. MATERIALS AND METHODS: The human papillomavirus (HPV) type 18 E7 and eIF4E mRNAs were measured following knock down or overexpression of E7 gene by RT-PCR and real-time PCR. Cell counting kit-8 assay was used to determine the cell proliferation. Flow cytometry was used to analyze the cell cycle and apoptosis. Transwell system was employed to determine the cell migration. RESULTS: Overexpression of E7 gene increased eIF4E mRNA level by 24.3% (P<0.01) in HPV negative C33A cells. Knock down of E7 decreased markedly eIF4E mRNA by 73% (P<0.01) in HPV18 positive HeLa cells. Under the state of high expression of E7, 1) up-regulation of eIF4E drastically promoted the cell proliferation, cell cycle and cell migration, and inhibited the cell apoptosis. 2) down-regulation of eIF4E significantly inhibited the cell proliferation, cell cycle and the ability of cell migration, and also promoted the apoptosis of cervical cancer cells. CONCLUSION: HPV E7 induced eIF4E gene over transcription which might be a new marker for CC. The finding broadens the understanding of the CC carcinogenesis.

Multiple variants of HPV16 E6 gene in cervical invasive squamous cell carcinoma.

BACKGROUND: HPV16 is the most commonly detected genotype in cervical squamous cell carcinoma. E6 of HPV16 is a viral oncogene and has frequent DNA sequence variations whose encoded proteins have been shown to have heterogeneity in biochemical and biological properties. This study tried to establish whether the E6 variants derive from the infection pool or from spontaneous mutation in the host. MATERIALS AND METHODS: We combined the use of microdissection of multiple areas of tumor tissue, PCR-sequencing of HPV16 E6 and E5 genes and allele-specific amplification of PCR to analyze the E6 variations in four cases of cervical cancer (M4, M12, M13 and M23). RESULTS: We isolated two common (350G and 350T) and three rare (310G, 374T and 459C) E6 variations corresponding to five different E6 variants. The common E6 variations were always co-segregated with specific E5 variations. Both common variants persisted in all the four cases. Of three cases each had one additional rare E6 variant. CONCLUSION: The common E6 variants would derive from the infection pool, whereas the rare E6 variants may evolve from the mutation of either of the common E6 variants. This finding might have implications for the future study of natural HPV evolution, the design of viral vaccine and the carcinogenesis of cervical cancer.

LMP1 stimulates the transcription of eIF4E to promote the proliferation, migration and invasion of human nasopharyngeal carcinoma.

Eukaryotic translation initiation factor 4E (eIF4E) is the rate-limiting translation initiation factor for many oncogenes. Previous studies have shown eIF4E overexpression in nasopharyngeal carcinoma (NPC). We aimed to study whether viral oncogene latent membrane protein 1 (LMP1) stimulates the transcription of eIF4E to promote NPC malignancy. In NPC cell lines (CNE1 and CNE2), ectopic LMP1 significantly increased the mRNA and protein levels of eIF4E and the transcriptional activity of the eIF4E promoter in a LMP1-plasmid-transfected dose-dependent manner. As a backward experiment, knocking down of LMP1 significantly reduced eIF4E mRNA in B95-8 cells. In the high LMP1 expression condition, knocking down of c-Myc significantly reduced eIF4E mRNA in both NPC and B95-8 cells, and knocking down of eIF4E significantly inhibited the tumor proliferation, migration and invasion promoted by LMP1. The results indicated that LMP1 stimulates the transcription of eIF4E via c-Myc to promote NPC. To the best of our knowledge, this is the first evidence that LMP1 stimulates the transcription of eIF4E. This might be an important cause of the overexpression of eIF4E in NPC and be the novel mechanism by which LMP1 initiates cancer. LMP1-stimulated eIF4E initiates the translation of those oncogenes transcriptionally activated by LMP1 to amplify and pass down the carcinogenesis signals launched by LMP1.

HPV E6 induces eIF4E transcription to promote the proliferation and migration of cervical cancer.

Increasing evidence has placed eukaryotic translation initiation factor 4E (eIF4E) at the hub of tumor development and progression. Several studies have reported that eIF4E is over-expressed in cervical cancer; however, the mechanism remains elusive. The results of this study further confirm over-expression of eIF4E in cervical cancer tumors and cell lines, and we have discovered that the transcription of eIF4E is induced by protein E6 of the human papillomavirus (HPV). Moreover, regulation of eIF4E by E6 significantly influences cell proliferation, the cell cycle, migration, and apoptosis. Therefore, eIF4E emerges as a key player in tumor development and progression and a potential target for CC treatment and prevention.

EIF4E over-expresses and enhances cell proliferation and cell cycle progression in nasopharyngeal carcinoma.

Eukaryotic translation initiation factor 4E (eIF4E) is involved in integration and amplification of many carcinogenesis signals in tumors. However, it remains unclear whether eIF4E over-expresses in NPC and whether it is associated with the development of NPC. Here, we analyzed the expression state of eIF4E, c-Myc, and MMP9 in 24 nasopharyngitises and 64 nasopharyngeal carcinomas (NPC) tissues and studied the influences of eIF4E on the proliferation and cell cycle in NPC cell lines. The results indicate that eIF4E might over-express in NPC and the over-expression of eIF4E promotes NPC growth and cell cycle progression through enhancing the translational expression of c-Myc and MMP9. The finding certainly adds new knowledge in the understanding of the carcinogenesis of NPC and provides a potential molecular target for the NPC therapy and prevention.