MiR-30a and miR-379 modulate retinoic acid pathway by targeting DNA methyltransferase 3B in oral cancer.

BACKGROUND: Epigenetic silencing of retinoic acid (RA) signaling-related genes have been linked with the pathogenesis and clinical outcome in oral squamous cell carcinoma (OSCC) carcinogenesis. However, the precise mechanisms underlying the abnormal silencing of RA signaling-related genes in OSCC have not been well investigated. METHODS: Using combined analysis of genome-wide gene expression and methylation profile from 40 matched normal-tumor pairs of OSCC specimens, we found a set of retinoid signaling related genes are frequently hypermethylated and downregulated in OSCC patient samples, including alcohol dehydrogenase, iron containing 1 (ADHFE1) and aldehyde dehydrogenase 1 family, member A2 (ALDH1A2), which are the important rate-limiting enzymes in synthesis of RA. The expression of ADHFE1 and ALDH1A2 in OSCC patients was determine by quantitative real-time PCR (qRT-PCR) and immunohistochemistry. The binding sites of miR-30a and miR-379 with DNA methyltransferase 3B (DNMT3B) were predicted using a series of bioinformatic tools, and validated using dual luciferase assay and Western blot analyses. The functions of miR-30a, miR-379, and DNMT3B were accessed by growth and colony formation analyses using gain- and loss-of-function approaches. Chromatin immunoprecipitation (ChIP) was performed to explore the molecular mechanisms by arecoline and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) treatment. RESULTS: We demonstrated that deregulated miR-30a and miR-379 could represent a mechanism for the silencing of ADHFE1 and ALDH1A2 in OSCC through targeting DNMT3B. Ectopic expression of miR-30a and miR-379 could induce re-expression of methylation-silenced ADHFE1 and ALDH1A2, and lead to growth inhibition in oral cancer cells. Furthermore, the dysregulation of the miRNAs and DNMT-3B may result from exposure to tobacco smoking and betel quid chewing. CONCLUSIONS: Our results demonstrate that tobacco smoking and betel quid chewing could repress miR-30a and miR-379, which upregulate the DNMT3B expression, in turn, lead to the hypermethylation of ADHFE1 and ALDH1A genes, consequently, promote the oncogenic activity. These findings highlight the potential use of retinoids in combination with epigenetic modifiers for the prevention or treatment of oral cancer.

MiR-944/CISH mediated inflammation via STAT3 is involved in oral cancer malignance by cigarette smoking.

The cytokine-inducible Src homology 2-containing protein (CISH) is an endogenous suppressors of signal transduction and activator of transcription (STAT) and acts as a key negative regulator of inflammatory cytokine responses. Downregulation of CISH has been reported to associate with increased activation of STAT and enhanced inflammatory pathways. However, whether microRNAs (miRNAs) play a crucial role in CISH/STAT regulation in oral squamous cell carcinoma (OSCC) remains unknown. The expression of CISH on OSCC patients was determine by quantitative real-time PCR (qRT-PCR) and immunohistochemistry. Specific targeting by miRNAs was determined by software prediction, luciferase reporter assay, and correlation with target protein expression. The functions of miR-944 and CISH were accessed by transwell migration and invasion analyses using gain- and loss-of-function approaches. Enzyme-linked immunosorbent assay (ELISA) and qRT-PCR were used to evaluate the pro-inflammation cytokines expression under the miR-944, CISH, NNK or combinations treatment. We found that the CISH protein, which modulates STAT3 activity, as a direct target of miR-944. CISH protein was significantly down-regulated in OSCC patients and cell lines and its level was inversely correlated with miR-944 expression. The miR-944-induced STAT3 phosphorylation, pro-inflammation cytokines secretion, migration and invasion were abolished by CISH restoration, suggesting that the oncogenic activity of miR-944 is CISH dependent. Furthermore, tobacco extract (NNK) may contribute to miR-944 induction and STAT3 activation. Antagomir-mediated inactivation of miR-944 prevented the NNK-induced STAT3 phosphorylation and pro-inflammation cytokines secretion. Altogether, these data demonstrate that NNK-induced miR944 expression plays an important role in CISH/STAT3-mediated inflammatory response and activation of tumor malignancy.

MicroRNA-486-3p functions as a tumor suppressor in oral cancer by targeting DDR1.

BACKGROUND: Discoidin domain receptor-1 (DDR1) tyrosine kinase is highly expressed in a variety of human cancers and involved in various steps of tumorigenesis. However, the precise mechanisms underlying the abnormal expression of DDR1 in oral squamous cell carcinoma (OSCC) has not been well investigated. METHODS: The expression of DDR1 on OSCC patients was determine by quantitative real-time PCR (qRT-PCR) and immunohistochemistry. Specific targeting by miRNAs was determined by software prediction, luciferase reporter assay, and correlation with target protein expression. The functions of miR-486-3p and DDR1 were accessed by MTT and Annexin V analyses using gain- and loss-of-function approaches. Chromatin immunoprecipitation (ChIP) and methylation specific PCR (MSP) were performed to explore the molecular mechanisms by arecoline treatment. RESULTS: Here, we reported that DDR1 was significantly upregulated in OSCC tissues and its levels were inversely correlated with miR-486-3p expression. The experimental results in vitro confirmed that miR-486-3p decreased DDR1 expression by targeting the 3'-UTR of DDR1 mRNA. Overexpression of miR-486-3p led to growth inhibition and apoptosis induction with a similar function by knockdown of DDR1. Aberrant methylation of ANK1 promoter was a highly prevalent in OSCC and contributes to oral carcinogenesis by epigenetic silencing of ANK1 and miR-486-3p. We found that miR-486-3p can be transcriptionally co-regulated with its host gene ANK1 through epigenetic repression. DNA methylation inhibitor treatment re-expressed ANK1 and miR-486-3p. Importantly, arecoline, a major betel nut alkaloid, recruited DNMT3B binding to ANK1 promoter for DNA methylation and then attenuated the expression of miR-486-3p in OSCC. CONCLUSION: This study was the first to demonstrate that betel nut alkaloid may recruit DNMT3B to regulate miR-486-3p/DDR1 axis in oral cancer andmiR-486-3p and DDR1 may serve as potential therapeutic targets of oral cancer.

MPT0B098, a Microtubule Inhibitor, Suppresses JAK2/STAT3 Signaling Pathway through Modulation of SOCS3 Stability in Oral Squamous Cell Carcinoma.

Microtubule inhibitors have been shown to inhibit Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signal transduction pathway in various cancer cells. However, little is known of the mechanism by which the microtubule inhibitors inhibit STAT3 activity. In the present study, we examined the effect of a novel small-molecule microtubule inhibitor, MPT0B098, on STAT3 signaling in oral squamous cell carcinoma (OSCC). Treatment of various OSCC cells with MPT0B098 induced growth inhibition, cell cycle arrest and apoptosis, as well as increased the protein level of SOCS3. The accumulation of SOCS3 protein enhanced its binding to JAK2 and TYK2 which facilitated the ubiquitination and degradation of JAK2 and TYK2, resulting in a loss of STAT3 activity. The inhibition of STAT3 activity led to sensitization of OSCC cells to MPT0B098 cytotoxicity, indicating that STAT3 is a key mediator of drug resistance in oral carcinogenesis. Moreover, the combination of MPT0B098 with the clinical drug cisplatin or 5-FU significantly augmented growth inhibition and apoptosis in OSCC cells. Taken together, our results provide a novel mechanism for the action of MPT0B098 in which the JAK2/STAT3 signaling pathway is suppressed through the modulation of SOCS3 protein level. The findings also provide a promising combinational therapy of MPT0B098 for OSCC.

IL-8 induces miR-424-5p expression and modulates SOCS2/STAT5 signaling pathway in oral squamous cell carcinoma.

Suppressor of cytokine signaling (SOCS) proteins are negative feedback regulators of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway. Dysregulation of SOCS protein expression in cancers can be one of the mechanisms that maintain STAT activation, but this mechanism is still poorly understood in oral squamous cell carcinoma (OSCC). Here, we report that SOCS2 protein is significantly downregulated in OSCC patients and its levels are inversely correlated with miR-424-5p expression. We identified the SOCS2 protein, which modulates STAT5 activity, as a direct target of miR-424-5p. The miR-424-5p-induced STAT5 phosphorylation, matrix metalloproteinases (MMPs) expression, and cell migration and invasion were blocked by SOCS2 restoration, suggesting that miR-424-5p exhibits its oncogenic activity through negatively regulating SOCS2 levels. Furthermore, miR-424-5p expression could be induced by the cytokine IL-8 primarily through enhancing STAT5 transcriptional activity rather than NF-κB signaling. Antagomir-mediated inactivation of miR-424-5p prevented the IL-8-induced cell migration and invasion, indicating that miR-424-5p is required for IL-8-induced cellular invasiveness. Taken together, these data indicate that STAT5-dependent expression of miR-424-5p plays an important role in mediating IL-8/STAT5/SOCS2 feedback loop, and scavenging miR-424-5p function using antagomir may have therapeutic potential for the treatment of OSCC.

Dysregulation of RUNX2/Activin-A Axis upon miR-376c Downregulation Promotes Lymph Node Metastasis in Head and Neck Squamous Cell Carcinoma.

Epigenetic correlates of the head and neck cancer may illuminate its pathogenic roots. Through a gene set enrichment analysis, we found that the oncogenic transcription factor RUNX2 is widely upregulated in the head and neck squamous cell carcinoma (HNSCC) with lymph node metastasis, where it also predicts poor prognosis in patients with HNSCC. Enforced expression of ectopic RUNX2 promoted the metastatic capabilities of HNSCC, whereas RUNX2 silencing inhibited these features. Mechanistic investigations showed that manipulating levels of activin A (INHBA) could rescue or compromise the RUNX2-mediated metastatic capabilities of HNSCC cells. Furthermore, we found that miR-376c-3p encoded within the 3'-untranslated region of RUNX2 played a pivotal role in regulating RUNX2 expression in highly metastatic HNSCC cells, where it was downregulated commonly. Restoring miR-376c expression in this setting suppressed expression of RUNX2/INHBA axis along with metastatic capability. Clinically, we observed an inverse relationship between miR-376c-3p expression and the RUNX2/INHBA axis in HNSCC specimens. In summary, our results defined a novel pathway in which dysregulation of the RUNX2/INHBA axis due to miR-376c downregulation fosters lymph node metastasis in HNSCC. Cancer Res; 76(24); 7140-50. ©2016 AACR.

Caveolin-1 regulates γ-secretase-mediated AßPP processing by modulating spatial distribution of γ-secretase in membrane.

Amyloidogenic processing of amyloid-ß precursor protein (AßPP) is associated with cholesterol- and sphingolipid-rich lipid rafts. Caveolin-1, a raft-residing protein, has been implicated in the pathogenesis of Alzheimer's disease. To determine the role of caveolin-1 in governing γ-secretase-mediated AßPP proteolysis, cellular γ-secretase activity was assessed in response to alteration in caveolin-1 expression. We demonstrated that suppression of caveolin-1 expression by RNA interference resulted in a significant increase in γ-secretase-mediated proteolysis of AßPP, generation of amyloid-ß, and cleavage of Notch. Overexpression of caveolin-1 attenuated γ-secretase-mediated proteolysis of AßPP and Notch, substantiating the negative regulation of γ-secretase by caveolin-1. Furthermore, we found that cells deficient in caveolin-1 exhibited significantly increased co-localization of γ-secretase with clathrin-coated non-caveolar endocytic vesicles, demonstrating that the partitioning of γ-secretase between caveolar and non-caveolar membranes can be modulated by caveolin-1. Our data also showed that JNK activation is essential for caveolin-1-mediated regulation of γ-secretase. Together, our results strongly suggest that caveolin-1 is an important regulator of γ-secretase activity.