MicroRNAs: Their Role in Metabolism, Tumor Microenvironment, and Therapeutic Implications in Head and Neck Squamous Cell Carcinoma.

MicroRNAs (miRNAs) are endogenous small non-coding RNA molecules that negatively regulate gene expression by binding to target mRNAs. Deregulated miRNAs can act as either oncogenic miRNAs or tumor suppressor miRNAs in controlling proliferation, differentiation, apoptosis, metastasis, epithelial-mesenchymal transition, and immune responses, which are all involved in the carcinogenesis process of HNSCC. Recent findings have shown that metabolic reprogramming is an important hallmark of cancer, which is necessary for malignant transformation and tumor development. Some reprogrammed metabolisms are believed to be required for HNSCC against an unfavorable tumor microenvironment (TME). The TME is composed of various cell types embedded in the altered extracellular matrix, among which exosomes, secreted by cancer cells, are one of the most important factors. Tumor-derived exosomes reshape the tumor microenvironment and play a crucial role in cell-to-cell communication during HNSCC development. Exosomes encapsulate many biomolecules, including miRNAs, circulate in body fluids, and can transmit intercellular regulatory messages to nearby and distant sites, which indicates that exosomal miRNAs have the potential to become non-invasive biomarkers. This review aims to clarify the functions of diverse miRNAs in HNSCC metabolic reprogramming and tumor-derived exosomes. In addition, it also emphasizes the potential role of miRNA as a biomarker in the diagnosis, prognosis, and treatment of HNSCC 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.

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.

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.

Downregulated miR329 and miR410 promote the proliferation and invasion of oral squamous cell carcinoma by targeting Wnt-7b.

microRNA (miRNA) dysregulation contributes widely to human cancer but has not been fully assessed in oral cancers. In this study, we conducted a global microarray analysis of miRNA expression in 40 pairs of betel quid-associated oral squamous cell carcinoma (OSCC) specimens and their matched nontumorous epithelial counterparts. Eighty-four miRNAs were differentially expressed in the OSCC specimens compared with the matched tissue. Among these downregulated miRNAs, 19 miRNAs were found and mapped to the chromosome 14q32.2 miRNA cluster region, which resides within a parentally imprinted region designated as Dlk-Dio3 and known to be important in development and growth. Bioinformatic analysis predicted two miRNAs from the cluster region, miR329 and miR410, which could potentially target Wnt-7b, an activator of the Wnt-ß-catenin pathway, thereby attenuating the Wnt-ß-catenin signaling pathway in OSCC. Stable ectopic expression of Wnt-7b in OSCC cells overexpressing miR329 or miR410 restored proliferation and invasion capabilities abolished by these miRNA. Combining a demethylation agent and a histone deacetylase inhibitor was sufficient to reexpress miR329, miR410, and Meg3, consistent with epigenetic regulation of these miRNA in human OSCC. Specifically, arecoline, a major betel nut alkaloid, reduced miR329, miR410, and Meg3 gene expression. Overall, our results provide novel molecular insights into how betel quid contributes to oral carcinogenesis through epigenetic silencing of tumor-suppressor miRNA that targets Wnt-ß-catenin signaling.

Pro-apoptotic role of Cdc25A: activation of cyclin B1/Cdc2 by the Cdc25A C-terminal domain.

Cdc25A is a dual specificity protein phosphatase that activates cyclin/cyclin-dependent protein kinase (Cdk) complexes by removing inhibitory phosphates from conserved threonine and tyrosine in Cdks. To address how Cdc25A promotes apoptosis, Jurkat cells were treated with staurosporine, an apoptosis inducer. Upon staurosporine treatment, a Cdc25A C-terminal 37-kDa fragment, designated C37, was generated by caspase cleavage at Asp-223. Thr-507 in C37 became dephosphorylated, which prevented 14-3-3 binding, as shown previously. C37 exhibited higher phosphatase activity than full-length Cdc25A. C37 with alanine substitution for Thr-507 (C37/T507A) that imitated the cleavage product during staurosporine treatment interacted with Cdc2, Cdk2, cyclin A, and cyclin B1 and markedly activated cyclin B1/Cdc2. The dephosphorylation of Thr-507 might expose the Cdc2/Cdk2-docking site in C37. C37/T507A also induced apoptosis in Jurkat and K562 cells, resulting from activating cyclin B1/Cdc2 but not Cdk2. Thus, this study reveals that Cdc25A is a pro-apoptotic protein that amplifies staurosporine-induced apoptosis through the activation of cyclin B1/Cdc2 by its C-terminal domain.