Epstein-Barr Virus Infection Alone or Jointly with Human Papillomavirus Associates with Down-Regulation of miR-145 in Oral Squamous-Cell Carcinoma

Down-regulation of tumor-suppressive miR-145 has been reported in various malignancies, including oral squamous-cell carcinoma (OSCC) that is influenced by several factors, including Epstein-Barr virus (EBV) and human papillomavirus (HPV). Oncoviruses can modulate the expression of cellular microRNAs. Therefore, we sought to investigate the association of miR-145 down-regulation in OSCC with EBV and/or HPV infection, which might be a possible mechanism of these viruses in oral carcinogenesis. Herein, prevalence of EBV, HPV, and their co-infection was significantly higher in tumors than normal tissues of OSCC. EBV infection alone or jointly with HPV was significantly associated with down-regulation of miR-145 in tumors compared with normal adjacent tissues. In cell lines infected with EBV or HPV, miR-145 was also down-regulated. Consistently, methylation of miR-145 was significantly greater in tumors, and well correlated with increased expression of DNMT3B, which was influenced by infection with EBV and HPV. In cell lines, only EBV infection was associated with increased expression of DNMT3B. Moreover, the level of EBV-LMP1 mRNA in tumors was negatively correlated with miR-145 and positively correlated with DNMT3B. Therefore, EBV alone or jointly with HPV is associated with down-regulation of miR-145 and may influence on miR-145 promoter methylation through the induction of DNMT3B in OSCC

Suppression of miR-22, a tumor suppressor in cervical cancer, by human papillomavirus 16 E6 via a p53/miR-22/HDAC6 pathway.

MicroRNAs (miRNAs) are small non-coding RNAs that function to down-regulate gene expression involving in various cellular processes related to carcinogenesis. Recently, miR-22 was identified as a tumor-suppressing miRNA in many human cancers. However, the regulatory mechanism and the specific function of this miRNA in cervical cancer remain unclear. In the present study, we carried out gene transfection, western blot and quantitative RT-PCR to explore the regulatory mechanism and the functional role of miR-22 in cervical cancer. We verified that miR-22 was down-regulated in cervical cancer tissues and cervical cancer cell lines relative to matched non-tumor tissues and normal human cervical keratinocyte line (HCK1T). By contrast, histone deacetylase 6 (HDAC6) was inversely correlated with miR-22 in both cervical tissues and cancer cell lines. Mechanically, HDAC6 was down-regulated by miR-22 at the post-transcriptional level, via a specific target site within the 3'UTR, identified by a luciferase reporter assay. Moreover, we also showed that the correlation between miR-22 and HDAC6 expression was regulated by an E6/p53 pathway in HCK1Ts expressing HPV16 E6. For functional study, an ectopic expression of miR-22 could inhibit cell proliferation and migration, and could induce apoptosis of cervical cancer cell lines. These findings demonstrated that miR-22 was down-regulated in cervical cancer and inversely collated with its downstream target HDAC6. MiR-22 acts as tumor suppressor by inhibiting proliferation and migration, and by inducing apoptosis of cervical cancer cell lines by targeting the 3'UTR of HDAC6. This newly identified E6/p53/miR-22/HDAC6 regulatory network might be a candidate therapeutic target for cervical cancer

Effects of arecoline on proliferation of oral squamous cell carcinoma cells by dysregulating c-Myc and miR-22, directly targeting oncostatin M

<div><p>Arecoline, the major alkaloid of areca nut, is known to induce oral carcinogenesis, however, its mechanism is still needed to elucidate. This study investigated the effects of arecoline on cell viability and cell-cycle progression of oral squamous cell carcinoma (OSCC) cells as well as a relevant cellular gene expression. The results showed that a low concentration of arecoline (0.025 μg/ml) increased OSCC cell viability, proportion of cells in G2/M phase and cell proliferation. Simultaneously, it induced IL-6, STAT3 and c-Myc expression. Interestingly, c-<i>myc</i> promoter activity was also induced by arecoline. MiR-22 expression in arecoline-treated OSCC cells was suppressed and comparable to an upregulated c-Myc expression. In arecoline-treated OSCC cells, oncostatin M (OSM) expression was significantly upregulated and inversely correlated with miR-22 expression. Likewise, OSM expression and its post-transcriptional activity were significantly decreased in miR-22-transfected OSCC and 293FT cells. This result demonstrated that miR-22 directly targeted OSM. Interestingly, miR-22 played an important role as a tumor suppresser on suppressing cell proliferation, migration and cell-cycle progression of OSCC cells. This result suggested the effect of arecoline to promote cell proliferation and cell-cycle progression of OSCC cells might be involved in induction of c-Myc expression and reduction of miR-22 resulting in OSM upregulation.</p></div

Relative expression levels of miR-22 and OSM.

<p>100 and 500 ng/well of mock control (pIRES2-EGFP vector) and pIRES-miR-22 vectors were transfected into ORL-48(T) and ORL-136(T) cells. At 24 and 48 hours post-transfection, pri-miR-22 (A-B) and OSM (C-D) expression was determined by RT-PCR. Protein levels of OSM (E) were determined in ORL-48(T) and ORL-136(T) cells at 48 hours after transfection with 100 ng of mock control and pIRES-miR-22 vectors. Relative intensity of OSM protein band (F-G) was calculated using ImageJ 1.49v software. Statistical significance of the differences was analyzed using One-way ANOVA followed by Tukey’s multiple comparison test (*<i>P</i> < 0.05, **<i>P</i> < 0.01 and ***<i>P</i> < 0.001).</p

Up-Regulation of miR-21 Is Associated with Cervicitis and Human Papillomavirus Infection in Cervical Tissues.

MicroRNA-21 (miR-21) is recognized as an oncomir and shows up-regulation in many types of human malignancy. The aim of this study was to investigate the association of miR-21 expression associated with HPV infection in normal and abnormal cervical tissues. Cervical tissue samples with different cytological or histopathological grades were investigated for HPV by PCR and for miR-21 and programmed cell death, protein 4 (PDCD4) expression using quantitative real-time PCR (qRT-PCR). Laser capture microdissection (LCM) of stromal and epithelial tissues and in situ hybridization (ISH) using locked nucleic acid (LNA) probes were performed on a subset of fixed specimens. Cell line experiments were conducted on fibroblasts stimulated in culture media from HeLa cells, which were then assessed for miR-21, PDCD4, IL-6 and α-SMA expression by qRT-PCR. Twenty normal cervical cell, 12 cervicitis, 14 cervical intraepithelial neoplastic I (CIN I), 22 CIN II-III and 43 cervical squamous cell carcinoma (SCC) specimens were investigated. miR-21 levels were significantly lower in normal than in abnormal tissues. The expression of miR-21 in HPV negative normal cytology was significantly lower than in HPV positive samples in abnormal tissue and SCC. The miR-21 expression was significantly higher in HPV negative cervicitis than HPV negative normal cells. LCM and ISH data showed that miR-21 is primarily expressed in the tumor-associated stromal cell microenvironment. Fibroblasts treated with HeLa cell culture media showed up-regulated expression of miR-21, which correlated with increased expression of α-SMA and IL-6 and with down-regulation of PDCD4. These results demonstrate that miR-21 is associated with HPV infection and involved in cervical lesions as well as cervicitis and its up-regulation in tumor-stroma might be involved in the inflammation process and cervical cancer progression

Effect of arecoline on IL-6 and STAT3 in ORL-48(T) and ORL-136(T) cells.

<p>ORL-48(T) and ORL-136(T) cells were treated with 0, 0.025 and 25 μg/ml arecoline for 24 hours. Expression of IL-6 (A and D) and STAT3 (B and E) were investigated by RT-PCR and their amplicons were visualized by 2% agarose gel electrophoresis (C and F). Statistical significance of the differences of relative expression was analyzed using One-way ANOVA followed by Tukey’s multiple comparison test (*<i>P</i> < 0.05 and **<i>P</i> < 0.01).</p

The effects of arecoline on cell viability and cell-cycle progression.

<p>Cytotoxicity (A and B) and cell proliferation (C and D) were determined in arecoline-untreated or treated OSCC cell lines at various concentrations for 24 hours using the MTT assay. Statistical significance of the differences of cell viability (%) was analyzed using One-way ANOVA followed by Tukey’s multiple comparison test (*<i>P</i> < 0.05, **<i>P</i> < 0.01 and ***<i>P</i> < 0.001). Cell-cycle phase distribution (E and F) in ORL-48(T) cells treated with 0 and 0.025 μg/ml of arecoline in synchronized condition was analyzed by flow cytometry. The percentages of G0/G1, S and G2/M population (G) of arecoline-treated cells were compared to untreated ORL-48(T) cells as control. Statistical significance of the differences of G2/M population was analyzed using Paired <i>t</i>-test (*<i>P</i> < 0.05).</p

MiR-22 targets OSM and miR-22 functions in cell proliferation, migration and cell-cycle assay.

<p>The construct of the miR-22 targets sequence within the OSM 3′UTR WT and Mut in pGL3-Control vector. The luciferase gene was linked to the 3′UTR WT and Mut of OSM. 293FT cells were co-transfected with 250 ng pIRES-miR-22 and 100 ng pGL3-OSM 3′UTR WT or Mut vectors (A). The normalized luciferase activity in pIRES-miR-22 and pGL3-OSM 3′UTR WT or Mut co-transfected cells was relative to normalized luciferase activity of pIRES2-EGFP and OSM 3′UTR WT or Mut co-transfected cells (B). A green fluorescence expression vector (pEGFP-N3) was transfected for monitoring transfection efficiency. Statistical significance of the differences of luciferase activity was analyzed using Two-way ANOVA (*<i>P</i> < 0.05). Cell proliferation and migration in pIRES-miR-22-transfected ORL-48(T) cells were measured by a hemocytometer and wound healing assay at different incubation time points (C-E). The photograph was taken under 4X objective lens NIS-Elements Advanced Research Imaging Software version 3.0. Statistical significance of the differences of cell viability and wound closure was analyzed using Student's <i>t</i>-test (*<i>P</i> < 0.05 and ***<i>P</i> < 0.001). Cell-cycle assay in miR-22 or mock-transfected ORL-48(T) for 48 hours post-transfection was performed by flow cytometry (F). Statistical significance of the differences of G2/M and G0/G1 population was analyzed using Paired <i>t</i>-test (*<i>P</i> < 0.05 and (**<i>P</i> < 0.01, respectively).</p

Primer sequences.

<p>Primer sequences.</p

The morphology of fibroblasts treated with culture media from HeLa cells.

<p>HeLa cells were cultured in exosome-depleted media. The treated cells were elongated.</p