E6-associated transcription patterns in human papilloma virus 16-positive cervical tissues

Gigaxonin Suppresses Epithelial-to-Mesenchymal Transition of Human Cancer Through Downregulation of Snail

Gigaxonin is an E3 ubiquitin ligase that plays a role in cytoskeletal stability. Its role in cancer is not yet clearly understood. Our previous studies of head and neck cancer had identified gigaxonin interacting with p16 for NFκB ubiquitination. To explore its role in cancer cell growth suppression, we analyzed normal and tumor DNA from cervical and head and neck cancers. There was a higher frequency of exon 8 SNP (c.1293 C>T, rs2608555) in the tumor (46% vs. 25% normal, P = 0.011) pointing to a relationship to cancer. Comparison of primary tumor with recurrence and metastasis did not reveal a statistical significance. Two cervical cancer cell lines, ME180 and HT3 harboring exon 8 SNP and showing T allele expression correlated with higher gigaxonin expression, reduced in vitro cell growth and enhanced cisplatin sensitivity in comparison with C allele expressing cancer cell lines. Loss of gigaxonin expression in ME180 cells through CRISPR-Cas9 or siRNA led to aggressive cancer cell growth including increased migration and Matrigel invasion. The in vitro cell growth phenotypes were reversed with re-expression of gigaxonin. Suppression of cell growth correlated with reduced Snail and increased e-cadherin expression. Mouse tail vein injection studies showed increased lung metastasis of cells with low gigaxonin expression and reduced metastasis with reexpression of gigaxonin. We have found an association between C allele expression and RNA instability and absence of multimeric protein formation. From our results, we conclude that gigaxonin expression is associated with suppression of epithelial-mesenchymal transition through inhibition of Snail.

SIGNIFICANCE

Our results suggest that GAN gene exon 8 SNP T allele expression correlates with higher gigaxonin expression and suppression of aggressive cancer cell growth. There is downregulation of Snail and upregulation of e-cadherin through NFκB ubiquitination. We hypothesize that exon 8 T allele and gigaxonin expression could serve as diagnostic markers of suppression of aggressive growth of head and neck cancer.

Construction of an immune-related ceRNA network in cervical cancer based on HPV E6 splicing

Background

Cervical cancer is one of the leading causes of cancer-related deaths worldwide. The unspliced human papillomavirus (HPV) E6 plays an important role in tumor progression and immune regulation. Improved immunotherapy implementation might benefit from a better knowledge of HPV E6 splicing-related immune gene expressions and immunocyte infiltration in cervical cancer. This study aimed to identify the potential therapeutic and prognostic roles of unspliced/spliced E6 ratio (E6 ratio) in cervical cancer.

Methods

Data from the TCGA were used to analyze the E6 condition and clinical information. Nomogram and K-M analysis were used to analyze assess the prognostic significance, IOBR was used to investigate immunological infiltrates. Functions and pathway enrichment analysis of DEGs were investigated through GO analysis and KEGG pathway analysis, respectively. A core module was taken from the competitive endogenous RNA (ceRNA) network and used to build a lncRNA-miRNA-mRNA network. QT-qPCR was used to detect the expression of genes. CCK-8, colony formation, wound healing and migration assays were used to detect cell functions.

Results

Our study found that HPV E6 ratio had significantly correlation with overall survival. In cervical cancer, a high E6 ratio was adversely linked with infiltrating levels of aDC, M1 macrophages, monocytes, NKT, and Tgd. High E6 ratio phenotypes were shown to be implicated in immune response regulation, cell adhesion, and Wnt signaling pathways, according to functional enrichment analysis. Subsequently, we constructed an immune-related ceRNA network based on E6 splicing in cervical cancer, including three lncRNA (LINC00943, LIFR-AS1, DANT2, and RASSF8-AS1), four miRNA (miR-205-5p, miR-181d-5p, miR-222-3p, and miR-221-3p), and seven mRNA (FGFR1, PRLR, CXCL2, ISG20, ISG15, SDC1, and NR2F2). Among them, CXCL2, SDC1, and miR-221-3p were associated with survival and immune cell infiltration.

Conclusions

These data imply that a high E6 ratio in cervical cancer contributes to the immune-related ceRNA network, resulting in a low amount of infiltrating effector immune cells and tumor growth. As a result, the E6 ratio might be employed as a biomarker in cervical cancer to determine prognosis and treatment success.

Evidence for disseminated tumor cells in lymphatic vessels afferent to sentinel lymph nodes in patients diagnosed with cervical cancer

BACKGROUND

In patients diagnosed with cervical cancer, the purpose of lymphadenectomy is the removal of lymph nodes for diagnosis and potential treatment of metastasized tumor cells. It is unclear if afferent lymphatic vessels harbor tumor cells and, thus, may pose additional risk for recurrence or progression if not removed.

AIM

In this feasibility study, we analyzed the lymphatic vessels afferent to sentinel lymph node (SLN) using a highly sensitive and specific molecular marker for cervical cancer cells.

METHODS AND RESULTS

Twenty patients diagnosed with cervical cancer of FIGO stage IA1 to IIB2 underwent laparoscopic SLN removal. Labeling was done using patent blue and the afferent lymphatic vessels were harvested from the parametric tissue and frozen at -80°C. HPV DNA type was evaluated in the primary tumor. Lymphatic vessels afferent to the sentinel lymph nodes were analyzed for the presence of viral oncogene transcripts of the respective HPV type. In one of 18 patients, all with tumor stage ≤IBI and pN0 by conventional histopathology, HPV mRNA could be detected in two of four lymphatic vessels, whereas at least one of the lymphatic vessel biopsies of both patients with tumors ˃4 cm and pN1 status was HPV mRNA positive. No clinical correlation with recurrence after a median follow-up of 9 years was noticed.

CONCLUSION

HPV mRNA indicative of disseminated tumor cells could be detected in lymphatic vessels. The relevance of harvesting lymphatic vessels afferent to SLN in order to increase oncologic safety will have to be investigated in a future prospective study.

Dysregulation of hsa-miR-34a and hsa-miR-449a leads to overexpression of PACS-1 and loss of DNA damage response (DDR) in cervical cancer

We have observed overexpression of PACS-1, a cytosolic sorting protein in primary cervical tumors. Absence of exonic mutations and overexpression at the RNA level suggested a transcriptional and/or posttranscriptional regulation. University of California Santa Cruz genome browser analysis of PACS-1 micro RNAs (miR), revealed two 8-base target sequences at the 3' terminus for hsa-miR-34a and hsa-miR-449a. Quantitative RT-PCR and Northern blotting studies showed reduced or loss of expression of the two microRNAs in cervical cancer cell lines and primary tumors, indicating dysregulation of these two microRNAs in cervical cancer. Loss of PACS-1 with siRNA or exogenous expression of hsa-miR-34a or hsa-miR-449a in HeLa and SiHa cervical cancer cell lines resulted in DNA damage response, S-phase cell cycle arrest, and reduction in cell growth. Furthermore, the siRNA studies showed that loss of PACS-1 expression was accompanied by increased nuclear γH2AX expression, Lys382-p53 acetylation, and genomic instability. PACS-1 re-expression through LNA-hsa-anti-miR-34a or -449a or through PACS-1 cDNA transfection led to the reversal of DNA damage response and restoration of cell growth. Release of cells post 24-h serum starvation showed PACS-1 nuclear localization at G1-S phase of the cell cycle. Our results therefore indicate that the loss of hsa-miR-34a and hsa-miR-449a expression in cervical cancer leads to overexpression of PACS-1 and suppression of DNA damage response, resulting in the development of chemo-resistant tumors.

Comparative RNA sequencing reveals that HPV16 E6 abrogates the effect of E6*I on ROS metabolism

High-risk Human Papillomavirus infections are responsible for anogenital and oropharyngeal cancers. Alternative splicing is an important mechanism controlling HPV16 gene expression. Modulation in the splice pattern leads to polycistronic HPV16 early transcripts encoding a full length E6 oncoprotein or truncated E6 proteins, commonly named E6*. Spliced E6*I transcripts are the most abundant RNAs produced in HPV-related cancers. To date, the biological function of the E6*I isoform remains controversial. In this study, we identified, by RNA sequencing, cellular targets deregulated by E6*I, among which genes related to ROS metabolism. Concomitantly, E6*I-overexpressing cells display high levels of ROS. However, co-overexpression of both E6 and E6*I has no effect on ROS production. In HPV16-infected cells expressing different E6/E6*I levels, we show that the newly identified targets CCL2 and RAC2 are increased by E6*I but decreased by E6 expression, suggesting that E6 abrogates the effect of E6*I. Taken together, these data support the idea that E6*I acts independently of E6 to increase ROS production and that E6 has the ability to counteract the effects of E6*I. This asks the question of how E6*I can be considered separately of E6 in the natural history of HPV16 infection.

Characterization of HPV integration, viral gene expression and E6E7 alternative transcripts by RNA-Seq: A descriptive study in invasive cervical cancer

Scarce data are available on the expression of papillomavirus genome and the frequency of alternatively spliced E6E7 mRNAs in invasive cervical cancer. We carried out a comprehensive characterization of HPV expression by RNA-Seq analysis in 22 invasive cervical cancer with HPV16 or HPV18, characterizing the presence of integrated/episomal viral DNA, the integration sites in human genome and the proportion of alternative splicing products of E6 and E7 genes. The expression patterns suggested the presence of episomal and/or integrated viral DNA, with integration detected in most tumors, frequently occurring within human genes in HPV18+ and in intergenic regions in HPV16+ tumors. Alternative splicing of E6E7 transcripts showed E6*I as the most frequent isoform for both viral types, followed by E6*II and E6/E7 (unspliced) transcripts in HPV16+, and by E6/E7 in HPV18+ tumors. Previously described E6*VI and E6*V transcript isoforms for HPV16, and E6*X for HPV18, were rare or not detected.

Detection and genotyping of human papillomavirus (HPV) in HIV-infected women and its relationship with HPV/HIV co-infection

HPV have been identified as high-risk and low-risk, depending on their association with the development of cancer. HPV infections can be facilitated by co-infection with HIV. Here, we investigated HPV prevalence and genotypes and the risk factors affecting HPV/HIV co-infection. Forty HIV-positive patients had 80 cervical swab samples collected in 2 consecutive years. Polymerase chain reaction and DNA direct sequencing were used to perform HPV genotyping. Statistical analyses were performed regarding risk factors for HPV/HIV co-infection and the occurrence of cervical lesions. HPV DNA was detected in 59 samples (73.75%), and high-risk HPVs were predominant (59.3%). The most prevalent type was HPV56 (17%), followed by HPV16 (15.3%). Patient age did not affect the risk of cervical cancer (P = .84) or HPV prevalence in different years (P = .25/P = .63). CD4 count also did not affect the risk for cervical lesions in the tested samples (P = .15/P = .28). Although the HIV viral load was not correlated with an increase in cervical lesion detection in the first group of analyzed samples (P = .12), it did affect cervical cancer risk in the group of samples analyzed in the following year (P = .045). HIV-infected patients presented a high prevalence of HPV co-infection, and HPV16 and HPV56 were the most prevalent genotypes. Considering this, it is possible that immunodeficiency can contribute to increased susceptibility to HPV56 infection in HIV-infected patients. The association between HIV viral load and the lesions also confirmed the importance of monitoring HIV/HPV co-infected patients with high HIV viral loads.

Comparative analysis of HPV16 gene expression profiles in cervical and in oropharyngeal squamous cell carcinoma

Human papillomavirus type 16 (HPV16) is the major cause of cervical cancer and of a fraction of oropharyngeal carcinoma. Few studies compared the viral expression profiles in the two types of tumor. We analyzed HPV genotypes and viral load as well as early (E2/E4, E5, E6, E6*I, E6*II, E7) and late (L1 and L2) gene expression of HPV16 in cervical and oropharyngeal cancer biopsies. The study included 28 cervical squamous cell carcinoma (SCC) and ten oropharyngeal SCC, along with pair-matched non-tumor tissues, as well as four oropharynx dysplastic tissues and 112 cervical intraepithelial neoplasia biopsies. Viral load was found higher in cervical SCC (<1 to 694 copies/cell) and CIN (<1 to 43 copies/cell) compared to oropharyngeal SCC (<1 to 4 copies/cell). HPV16 E2/E4 and E5 as well as L1 and L2 mRNA levels were low in cervical SCC and CIN and undetectable in oropharynx cases. The HPV16 E6 and E7 mRNAs were consistently high in cervical SCC and low in oropharyngeal SCC. The analysis of HPV16 E6 mRNA expression pattern showed statistically significant higher levels of E6*I versus E6*II isoform in cervical SCC (p = 0.002) and a slightly higher expression of E6*I versus E6*II in oropharyngeal cases. In conclusion, the HPV16 E5, E6, E6*I, E6*II and E7 mRNA levels were more abundant in cervical SCC compared to oropharyngeal SCC suggesting different carcinogenic mechanisms in the two types of HPV-related cancers.

The Role of E6 Spliced Isoforms (E6*) in Human Papillomavirus-Induced Carcinogenesis

Persistent infections with High Risk Human Papillomaviruses (HR-HPVs) are the main cause of cervical cancer development. The E6 and E7 oncoproteins of HR-HPVs are derived from a polycistronic pre-mRNA transcribed from an HPV early promoter. Through alternative splicing, this pre-mRNA produces a variety of E6 spliced transcripts termed E6*. In pre-malignant lesions and HPV-related cancers, different E6/E6* transcriptional patterns have been found, although they have not been clearly associated to cancer development. Moreover, there is a controversy about the participation of E6* proteins in cancer progression. This review addresses the regulation of E6 splicing and the different functions that have been found for E6* proteins, as well as their possible role in HPV-induced carcinogenesis.