Abstract Tumor metastasis is the dominant cause of death in cancer patients, including patients with oral tongue squamous cell carcinoma (TSCC). Previously, we reported that reduced miR‐138 level is correlated with enhanced metastatic potential in TSCC cells. Here, we demonstrate that miR‐138 suppresses TSCC cell migration and invasion by regulating 2 key genes in the Rho GTPase signaling pathway: RhoC and ROCK2. Direct targeting of miR‐138 to specific sequences located in the 3′‐untranslated regions of both RhoC and ROCK2 mRNAs was confirmed using luciferase reporter gene assays. Ectopic transfection of miR‐138 reduced the expression of both RhoC and ROCK2 in TSCC cells. These reduced expressions, in consequence, led to the reorganization of the stress fibers and the subsequent cell morphology change to a round bleb‐like shape as well as the suppression of cell migration and invasion. In contrast, knockdown of miR‐138 in TSCC cells enhanced the expression of RhoC and ROCK2, which resulted in an altered, elongated cell morphology, enhanced cell stress fiber formation and accelerated cell migration and invasion. Taken together, our results suggest that miR‐138 plays an important role in TSCC cell migration and invasion by concurrently targeting RhoC and ROCK2, and miR‐138 may serve as a novel therapeutic target for TSCC patients at risk of metastatic disease.
miR-7 (microRNA-7) has been characterized as a tumour suppressor in several human cancers. It targets a number of proto-oncogenes that contribute to cell proliferation and survival. However, the mechanism(s) by which miR-7 suppresses tumorigenesis in TSCC (tongue squamous cell carcinoma) is unknown. The present bioinformatics analysis revealed that IGF1R (insulin-like growth factor 1 receptor) mRNA is a potential target for miR-7. Ectopic transfection of miR-7 led to a significant reduction in IGF1R at both the mRNA and protein levels in TSCC cells. Knockdown of miR-7 in TSCC cells enhanced IGF1R expression. Direct targeting of miR-7 to three candidate binding sequences located in the 3'-untranslated region of IGF1R mRNA was confirmed using luciferase-reporter-gene assays. The miR-7-mediated down-regulation of IGF1R expression attenuated the IGF1 (insulin-like growth factor 1)-induced activation of Akt (protein kinase B) in TSCC cell lines, which in turn resulted in a reduction in cell proliferation and cell-cycle arrest, and an enhanced apoptotic rate. Taken together, the present results demonstrated that miR-7 regulates the IGF1R/Akt signalling pathway by post-transcriptional regulation of IGF1R. Our results indicate that miR-7 plays an important role in TSCC and may serve as a novel therapeutic target for TSCC patients.
Microtubule-associated tumor suppressor gene (MTUS1) has been identified as tumor suppressor gene in many malignant tumors. In this study, we investigated the role of MTUS1 in the development of salivary adenoid cystic carcinoma (SACC) and its functional effect on the migration and invasion of SACC.Archival clinical samples including 49 primary SACC were examined for MTUS1 expression by immunohistochemistry. Statistical analyses were performed to evaluate the correlation between MTUS1 with histopathological features and survival. The expression of MTUS1/ATIP (AT2 receptor-interacting protein) isoforms was determined in SACC tissue samples and cell lines using quantitative RT-PCR assays. Then we investigated whether the migration and invasion of SACC were mediated by MTUS1/ATIP3a using in vitro cell migration and invasion assay.We confirmed that the down-regulation of MTUS1 was a frequent event in SACC, and was correlated with distant metastasis and associated with reduced overall survival and disease free survival. Isoform specific quantitative RT-PCR assays revealed that ATIP1, ATIP3a and ATIP3b were the major isoforms of the MTUS1 gene products in SACC, and were significant down-regulation in SACC as compared to matching normal tissues. For functional analyses, we found that SACC-LM cells (SACC cell line with higher migration and invasion ability) possessed a lower expression level of ATIP3a compared to SACC-83 cells (lower migration and invasion ability). Restoration of ATIP3a expression in SACC-LM cells induced anti-proliferative activity and inhibited the migration and invasion ability. Knockdown of ATIP3a promoted the proliferation, migration and invasion ability of SACC-83 cells. Restoration of ATIP3a inhibited the phosphorylation of ERK (extracellular-regulated kinase) 1/2, the expression of Slug and Vimentin in SACC-LM cells, while knockdown of ATIP3a increased the phosphorylation of ERK1/2, the expression of Slug and Vimentin in SACC-83 cells.Our studies confirm that MTUS1 plays an important role in the progression of SACC, and may serve as a biomarker or therapeutic target for patients with SACC. MTUS1/ATIP3a down-regulation contributes to the proliferation, migration and the invasion abilities of SACC.
Abstract Our previous studies had revealed that over-expression of manganese superoxide dismutase (SOD2) is a frequent event in tongue squamous cell carcinoma (TSCC) [BMC Cancer. 2010 10:365], and it contributes to the enhanced metastatic potential of TSCC through regulating cell migration and invasion [Free Radic Biol Med. 2012 53(1):44-50]. In the current study, our immunohistochemistry analysis confirmed the over-expression of SOD2 in TSCC patient cohort, and further revealed that over-expression of Bmi1, a member of the Polycomb group of chromatin-modifier proteins that is essential for stem cell self-renewal, is also a common event in premalignant dysplasia, primary SCC, and lymph node metastases. Furthermore, the over-expression of BMI1 is associated with poor prognosis. More importantly, a statistically significant correlation was observed between Bmi1 expression and SOD2 expression. These observations were supported by our in vitro studies, in which knockdown of SOD2/Bmi1 in TSCC cell line (UM1) or stem cell marker-expressing side population (SP) of the UM1 cells led to reduced cell migration and invasion, as well as decreases in the SP proportion (in UM1 cells), proliferation, sphere and clone formation and reduced expression of stem cell markers (ABCG, Nanog, Bmi1). Interesting, knockdown of SOD2 in UM1 or SP led to reduced expression of Bmi1, and knockdown of Bmi1 led to reduced expression of SOD2, which mirrors the observed correlation between Bmi1 and SOD2 in the TSCC patient cohort. Since c-myc is a known oncogene that has been showed to regulate both Bmi1 and SOD2, we further examined the role of c-myc-SOD2/Bmi1 pathway in TSCC. Direct binding of c-myc protein to the E-box in the Bmi1/SOD2 promoter were demonstrated by ChIP assay and Luciferase assay. Moreover, knockdown of c-myc in UM1 or SP cells led to reduced expression of both Bmi1 and SOD2, as well as reduced cell migration, and invasion, reduced expression of stem cell markers, decreases in the SP proportion (in UM1 cells), inhibition in cell proliferation, sphere and clone formation. Taken together, these data suggest that Bmi1 and SOD2 are two major factors in the initiation and progression of TSCC, and play an important role in the migration and invasion of TSCC cells. C-myc directly regulated the expression of Bmi1 and SOD2, and thus mediated the migration and invasion and maintaining the stemmness of the CSC in TSCC. Citation Format: Qianting He, Zhonghua Liu, Leitao Zhang, Tingting Zhao, Luodan Zhao, Dan Chen, Yu Chen, Xueqiang Ding, Xiaofeng Zhou, Anxun Wang. C-myc-SOD2/Bmi1 pathway mediates cancer stem-like cell migration and invasion in tongue squamous cell carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1135. doi:10.1158/1538-7445.AM2014-1135
MicroRNA-138 is one of the most frequently down-regulated microRNAs in cancer. We recently identified 51 candidate targets of microRNA-138 (Jiang, L., Dai, Y., Liu, X., Wang, C., Wang, A., Chen, Z., Heidbreder, C. E., Kolokythas, A., and Zhou, X. (2011) Hum. Genet. 129, 189–197). Among these candidates, Fos-like antigen 1 (FOSL1) is a member of Fos gene family and is a known proto-oncogene. In this study, we first confirmed the microRNA-138-mediated down-regulation of FOSL1 in squamous cell carcinoma cell lines. We then demonstrated the effect of this microRNA-138-FOSL1 regulatory module on downstream genes (homolog of Snail 2 (Snai2) expression and the Snai2-mediated repression of E-cadherin expression), as well as its contributions to tumorigenesis. The microRNA-138-directed recruitment of FOSL1 mRNA to the RNAi-induced silencing complex was confirmed by a ribonucleoprotein-immunoprecipitation assay. Three canonical and three high affinity non-canonical microRNA-138 (miR-138) targeting sites were identified on the FOSL1 mRNA: one in the 5′-UTR, three overlapping sites in the coding sequences, and two overlapping sites in the 3′-UTR. The direct targeting of miR-138 to these sites was confirmed using luciferase reporter gene assays. In summary, we describe an important microRNA regulatory module, which may play an important role in cancer initiation and progression. Our results also provide evidence that microRNAs target both canonical and non-canonical targeting sites located in all areas of the mRNA molecule (e.g. 5′-UTR, coding sequences, and 3′-UTR). MicroRNA-138 is one of the most frequently down-regulated microRNAs in cancer. We recently identified 51 candidate targets of microRNA-138 (Jiang, L., Dai, Y., Liu, X., Wang, C., Wang, A., Chen, Z., Heidbreder, C. E., Kolokythas, A., and Zhou, X. (2011) Hum. Genet. 129, 189–197). Among these candidates, Fos-like antigen 1 (FOSL1) is a member of Fos gene family and is a known proto-oncogene. In this study, we first confirmed the microRNA-138-mediated down-regulation of FOSL1 in squamous cell carcinoma cell lines. We then demonstrated the effect of this microRNA-138-FOSL1 regulatory module on downstream genes (homolog of Snail 2 (Snai2) expression and the Snai2-mediated repression of E-cadherin expression), as well as its contributions to tumorigenesis. The microRNA-138-directed recruitment of FOSL1 mRNA to the RNAi-induced silencing complex was confirmed by a ribonucleoprotein-immunoprecipitation assay. Three canonical and three high affinity non-canonical microRNA-138 (miR-138) targeting sites were identified on the FOSL1 mRNA: one in the 5′-UTR, three overlapping sites in the coding sequences, and two overlapping sites in the 3′-UTR. The direct targeting of miR-138 to these sites was confirmed using luciferase reporter gene assays. In summary, we describe an important microRNA regulatory module, which may play an important role in cancer initiation and progression. Our results also provide evidence that microRNAs target both canonical and non-canonical targeting sites located in all areas of the mRNA molecule (e.g. 5′-UTR, coding sequences, and 3′-UTR).
Abstract Chemoresistance often associated with other clinical characteristics, such as enhanced metastatic potential. However, the underlying molecular mechanism remains unclear. Our previous studies had revealed that microRNA-222 (miR-222) regulates the cell invasion [Cancer Genomics Proteomics 2009 6:131-138], and plays a role in cell proliferation in tongue squamous cell carcinoma (TSCC) [FEBS Lett. 2010 584(18):4115-20]. The aim of this study is to elucidate the role of miR-222-ABCG2 pathway in the association of cisplatin (cDDP) resistance with enhanced cell migration and invasion ability in TSCC. First, we confirmed the association between cDDP resistance (measured by IC50) and metastatic potential (assessed by migration and invasion assays) using TSCC cell lines and primary cultures from TSCC cases. The siRNA-mediated ABCG2 knockdown led to enhanced cDDP responsiveness, and reduced metastatic potential in TSCC cells. On the contrary, ABCG2 overexpression induced cDDP resistance, and enhanced cell migration and invasion in TSCC cells. Bioinformatics analysis revealed that ABCG2 is a target gene of miR-222, and the direct interaction of miR-222 with ABCG2 mRNA was confirmed by luciferase reporter gene assay. Functional analyses indicated that miR-222 downregulated the expression of ABCG2 gene and enhanced cDDP responsiveness, as well as reduced cell migration and invasion in TSCC cells. Thus, our results confirmed the association between cDDP resistance and enhanced metastatic potential in TSCC. ABCG2 is a direct target gene of miR-222, and deregulation of miR-222-ABCG2 regulatory module in TSCC contributes to both cDDP resistance and enhanced metastatic potential. Citation Format: Anxun Wang, Luodan Zhao, Qianting He, Tingting Zhao, Wei Wang, Xiaofeng Zhou. Deregulation of miR-222-ABCG2 regulatory module in tongue squamous cell carcinoma contributes to chemoresistance and enhanced metastatic potential. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 194. doi:10.1158/1538-7445.AM2015-194
Squamous cell carcinomas are the leading frequent malignant tumors in the oral and maxillofacial region. Currently available treatment options are of limited efficacy, and there is an urgent need for development of alternative therapies. RNA interference (RNAi) is a sequence-specific RNA degradation process. In this study, we screened and identified an in vitro-transcribed 21-bp shRNA targeting human telomerase reverse transcriptase (hTERT) from three candidates and generated a lentivirus vector. Subsequent experiments indicated that this lentiviral transgenic system could effectively transfer into target KB cells, above 80% gene transfer efficiency at MOI of 2.5, and significantly and specifically inhibited hTERT expression both in mRNA (73.42%) and protein (74.67-82.91%) levels. To further evaluate the role of hTERT-targeted RNAi, we found that hTERT inhibition consequently induced suppression of cyclin D1 (54.67%), upregulation of caspase-3 (100.10%), and caspase-9 (42.67%) of KB cells. Therefore, the apoptosis rates of KB cells were increased by 206.33%. In conclusion, these data indicated the potential of lentivirus vectors in cancer gene therapy, especially after development of more efficient vector production methods, and higher virus titers demonstrated that targeting hTERT RNAi may result in telomere uncapping, which triggers cell cycle arrest and apoptosis signal and leads to tumor suppression.
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