Bridging Links between Long Noncoding RNA HOTAIR and HPV Oncoprotein E7 in Cervical Cancer Pathogenesis

Abstract

Human Papillomavirus (HPV) type 16 oncoprotein E7 plays a major role in cervical carcinogenesis by interacting with and functionally inactivating various host regulatory molecules. Long noncoding RNA (lncRNA) HOTAIR is one such regulator that recruits chromatin remodelling complex PRC2, creating gene silencing H3K27 me3 marks. Hence, we hypothesized that HOTAIR could be a potential target of E7, in HPV16 related cervical cancers (CaCx). We identified significant linear trend of progressive HOTAIR down-regulation through HPV negative controls, HPV16 positive non-malignants and CaCx samples. Majority of CaCx cases portrayed HOTAIR down-regulation in comparison to HPV negative controls, with corresponding up-regulation of HOTAIR target, HOXD10, and enrichment of cancer related pathways. However, a small subset had significantly higher HOTAIR expression, concomitant with high E7 expression and enrichment of metastatic pathways. Expression of HOTAIR and PRC2-complex members (EZH2 and SUZ12), showed significant positive correlation with E7 expression in CaCx cases and E7 transfected C33A cell line, suggestive of interplay between E7 and HOTAIR. Functional inactivation of HOTAIR by direct interaction with E7 could also be predicted by in silico analysis and confirmed by RNA-Immunoprecipitation. Our study depicts one of the causal mechanisms of cervical carcinogenesis by HPV16 E7, through modulation of HOTAIR expression and function.Cervical carcinoma (CaCx) is the second most prevalent cancer among women in India after breast cancer and the fourth most prevalent cancer among women worldwide 1,2 . Human Papillomavirus (HPV) is considered as the major etiologic contributor to the development of CaCx and is found in 99.7% of all the cases, of which, the high-risk types HPV16 and 18 are the most prevalent ones 3,4 . HPV16 alone contributes to more than 50% of the CaCx cases globally 5 . HPV16 acts by frequently integrating into the host chromosome and replicates along with the host genome, which results in E2 gene disruption and consistent expression of the two HPV oncoproteins E6 and E7 due to loss of E2 repressor activity 6 . The infected epithelial basal cells differentiate from the basal membrane to the superficial zone and the virus particles are shed with the sloughed-off epithelial cells. Moreover, E6 and E7 also facilitate persistence of episomal HPV genomes in undifferentiated cells of the cervical epithelium 7 . It is well established that oncoproteins E6 and E7 are the major transforming agents, leading to carcinogenesis. While E6 regulates the decay of the tumor suppressor p53, E7 leads to cellular

Expression signatures of HOX cluster genes in cervical cancer pathogenesis: Impact of human papillomavirus type 16 oncoprotein E7

“…Such analysis, confirmed significant altered expression of all seven HOX cluster members among the cervical cancer cases, in comparison with the HPV negative control samples (Supplementary Table 2). Of these, upregulation of HOXD10 has been previously reported from our laboratory [9]. HOXA10 was the only member showing significantly reduced expression, as opposed to the rest revealing significant increase in expression (Figure 2).…”

“…The histopathologically normal samples were grouped together for comparison, as the HPV negative and HPV16 positive normal samples did not reveal any differentially expressed genes as described in our previous study [9]. …”

“…C33A cells were transfected with1 μg of plasmid pcDNA3.1-HPV16 E7 vector generated in our laboratory [9], using Lipofectamine 2000 reagent according to manufacturer's protocol. The cells were harvested and washed with 1X PBS, pH 7.4, trypsinized and collected by centrifugation at 300 xg for 10 minutes.…”

Unraveling the oral cancer lncRNAome: Identification of novel lncRNAs associated with malignant progression and HPV infection

“…There have been no detailed reports of those lncRNAs so far. The studies exploring the biological relevance and interplay between HPV infection and lncRNAs are still quite few [54,55]. …”

Long Non-Coding RNA ZEB1-Antisense 1 Affects Cell Migration and Invasion of Cervical Cancer by Regulating Epithelial-Mesenchymal Transition via the p38MAPK Signaling Pathway

“…Actually several lncRNAs have been found abnormally expressed in cervical cancer tissues to function as the oncogenes or antioncogenes, such as H19 [8], HOTAIR [9], and MEG3 [10]. ZEB1-antisense 1 (AS1) is another novel lncRNA located on chromosome 10p11.22 including 2 exons and 1 intron, with approximately 2,535 nucleotides in length [11].…”