Up-regulation of the SOX3 gene expression by retinoic acid: characterization of the novel promoter-response element and the retinoid receptors involved

Sox3/SOX3 gene is considered to be one of the earliest neural markers in vertebrates and it is implicated in the genetic cascades that direct brain formation. We have previously shown that early phases of differentiation and neural induction of NT2/D1 embryonal carcinoma cells by retinoic acid (RA) involve up-regulation of the SOX3 gene expression. Here, we present identification of a novel positive regulatory promoter element involved in RA-dependent activation of the SOX3 gene expression in NT2/D1 cells. This element represents a direct repeat 3-like motif that directly interacts with retinoid X receptor (RXR) alpha in a sequence-specific manner. It is capable of independently mediating the RA effect in a heterologous promoter context and its disruption caused significant reduction of RA/RXR transactivation of the SOX3 promoter. Furthermore, by using synthetic antagonists of retinoid receptors, we have shown for the first time, that RA-induced SOX3 gene expression could be significantly down-regulated by the synthetic antagonist of RXR. Also, this data showed that RXRs, but not RA receptors, are mediators of RA effect on the SOX3 gene up-regulation in NT2/D1 cells. Presented data will be valuable for future investigation of SOX3 gene expression, not only in NT2/D1 model system, but also in diverse developmental, physiological and pathological settings.     

Downregulation of MUC15 by miR-183-5p.1 promotes liver tumor-initiating cells properties and tumorigenesis via regulating c-MET/PI3K/AKT/SOX2 axis

Mucin 15 (MUC15) is reportedly aberrant in human malignancies, including hepatocellular carcinoma (HCC). However, the role of MUC15 in the regulation of liver tumor-initiating cells (T-ICs) remains unknown. Here, we report that expression of MUC15 is downregulated in liver T-ICs, chemoresistance and recurrent HCC samples. Functional studies reveal that MUC15 inhibits hepatoma cells self-renewal, malignant proliferation, tumorigenicity, and chemoresistance. Mechanistically, MUC15 interacts with c-MET and subsequently inactivates the PI3K/AKT/SOX2 signaling pathway. Moreover, we find that miR-183-5p.1 directly targets MUC15 3′-UTR in liver T-ICs. Coincidentally, SOX2 feedback inhibits MUC15 expression by directly transactivating miR-183-5p.1, thus completing a feedforward regulatory circuit in liver T-ICs. Importantly, MUC15/c-MET/PI3K/AKT/SOX2 axis determines the responses of hepatoma cells to lenvatinib treatment, and MUC15 overexpression abrogated lenvatinib resistance. Analysis of patient cohort, patient-derived tumor organoids and patient-derived xenografts further suggests that the MUC15 may predict lenvatinib benefits in HCC patients. Collectively, our findings suggest the crucial role of the miR-183-5p.1/MUC15/c-MET/PI3K/AKT/SOX2 regulatory circuit in regulating liver T-ICs properties, suggesting potential therapeutic targets for HCC.Subject terms: Cancer stem cells, Tumour biomarkers, Liver cancer     

Epigenetic activation of SOX11 in lymphoid neoplasms by histone modifications

Recent studies have shown aberrant expression of SOX11 in various types of aggressive B-cell neoplasms. To elucidate the molecular mechanisms leading to such deregulation, we performed a comprehensive SOX11 gene expression and epigenetic study in stem cells, normal hematopoietic cells and different lymphoid neoplasms. We observed that SOX11 expression is associated with unmethylated DNA and presence of activating histone marks (H3K9/14Ac and H3K4me3) in embryonic stem cells and some aggressive B-cell neoplasms. In contrast, adult stem cells, normal hematopoietic cells and other lymphoid neoplasms do not express SOX11. Such repression was associated with silencing histone marks H3K9me2 and H3K27me3. The SOX11 promoter of non-malignant cells was consistently unmethylated whereas lymphoid neoplasms with silenced SOX11 tended to acquire DNA hypermethylation. SOX11 silencing in cell lines was reversed by the histone deacetylase inhibitor SAHA but not by the DNA methyltransferase inhibitor AZA. These data indicate that, although DNA hypermethylation of SOX11 is frequent in lymphoid neoplasms, it seems to be functionally inert, as SOX11 is already silenced in the hematopoietic system. In contrast, the pathogenic role of SOX11 is associated with its de novo expression in some aggressive lymphoid malignancies, which is mediated by a shift from inactivating to activating histone modifications.     

LncRNA MALAT1/miR‐129 axis promotes glioma tumorigenesis by targeting SOX2

We aimed to explore the interaction among lncRNA MALAT1, miR‐129 and SOX2. Besides, we would investigate the effect of MALAT1 on the proliferation of glioma stem cells and glioma tumorigenesis. Differentially expressed lncRNAs in glioma cells and glioma stem cells were screened out with microarray analysis. The targeting relationship between miR‐129 and MALAT1 or SOX2 was validated by dual‐luciferase reporter assay. The expressions of MALAT1, miR‐129 and SOX2mRNA in both glioma non‐stem cells and glioma stem cells were examined by qRT‐PCR assay. The impact of MALAT1 and miR‐129 on glioma stem cell proliferation was observed by CCK‐8 assay, EdU assay and sphere formation assay. The protein expression of SOX2 was determined by western blot. The effects of MALAT1 and miR‐129 on glioma tumour growth were further confirmed using xenograft mouse model. The mRNA expression of MALAT1 was significantly up‐regulated in glioma stem cells compared with non‐stem cells, while miR‐129 was significantly down‐regulated in glioma stem cells. MALAT1 knockdown inhibited glioma stem cell proliferation via miR‐129 enhancement. Meanwhile, miR‐129 directly targeted at SOX2 and suppressed cell viability and proliferation of glioma stem cells by suppressing SOX2 expression. The down‐regulation of MALAT1 and miR‐129 overexpression both suppressed glioma tumour growth via SOX2 expression promotion in vivo. MALAT1 enhanced glioma stem cell viability and proliferation abilities and promoted glioma tumorigenesis through suppressing miR‐129 and facilitating SOX2 expressions.