Transcription factor Sox4 is required for PUMA-mediated apoptosis induced by histone deacetylase inhibitor, TSA

The CRL4DCAF6 E3 ligase ubiquitinates CtBP1/2 to induce apoptotic signalling and promote intervertebral disc degeneration

Inflammation and apoptosis are two important pathological causes of intervertebral disc degeneration (IDD). The crosstalk between these two biological processes during IDD pathogenesis remains elusive. Herein, we discovered that chronic inflammation induced apoptosis through a cullin-RING E3 ligase (CRL)-dependent mechanism. Two cullin proteins, CUL4A and 4B, recruited DNA damage-binding protein 1 (DDB1), RING-box protein 1 (RBX1) and DDB1- and CUL4-associated factor 6 (DCAF6) to assemble a CRL4^DCAF6 E3 ligase in intervertebral discs (IVDs) derived from IDD patients. The CRL4^DCAF6 E3 ligase ubiquitinated and degraded C-terminal-binding protein 1 and 2 (CtBP1/2), two homologues of transcriptional corepressors. The degradation of CtBP1/2 disassociated from the p300-forkhead box O3a (FOXO3a) complex, inducing the expression of B-cell lymphoma 2 (Bcl2)-binding component 3 (BBC3) and causing BBC3-dependent apoptosis. TSC01131, a small molecule that specifically targets CUL4-DDB1 interaction, could inhibit the ubiquitination of CtBP1/2 in vitro and in vivo, thereby decreasing the BBC3 expression level and preventing apoptosis signalling. Using a mouse chronic inflammation model, we found that chronic inflammation could accelerate the IDD process through a conserved CRL4^DCAF6-mediated mechanism. The administration of TSC01131 to mice could significantly improve the outcome of IDD. Collectively, our results revealed that inflammation-dependent CRL4^DCAF6 E3 ligase triggered apoptosis through the removal of CtBP-mediated transrepression. The blockage of the CRL4^DCAF6 E3 ligase by TSC01131 may represent a new therapeutic strategy for IDD treatment. KEY MESSAGES: CUL4A and CUL4B recruited DDB1, RBX1 and DCAF6 to assemble a CRL4^DCAF6 E3 ligase in human IDD biopsies. The CRL4^DCAF6 E3 ligase ubiquitinated and degraded CtBP1/2, causing BBC3-dependent apoptosis. A small molecule TSC01131 that specifically targets CUL4-DDB1 interaction could inhibit the ubiquitination of CtBP1/2, improving the outcome of IDD in a mouse model.

Overexpression of HIPK2 removes the transrepression of proapoptotic genes mediated by the CtBP1-p300-FOXO3a complex and increases the chemosensitivity in osteosarcoma cells

Decreased expression of proapoptotic genes can lead to the chemoresistenance in cancer therapy. Carboxyl-terminal binding protein 1 (CtBP1), a transcriptional corepressor with multiple oncogenic effects, has been previously identified to suppress the expression of two proapoptotic genes [BAX (BCL2 associated X) and BIM (Bcl-2 interacting mediator of cell death)] by assembling a complex with the Forkhead box O3 (FOXO3a) transcription factor and the p300 histone acetyltransferase. However, the upstream regulatory signaling of the CtBP1-p300-FOXO3a complex is obscure, and the effects of changing this signaling on chemosensitivity in osteosarcoma are unknown. Herein, we discovered that the downregulation of HIPK2 (Homeodomain-interacting protein kinase 2) was essential for the function of the CtBP1-p300-FOXO3a complex. Downregulation of HIPK2 prevented the phosphorylation and subsequent degradation of CtBP1, thereby allowing the assembly of the CtBP1-p300-FOXO3a complex and suppression of the expression of proapoptotic genes, such as BAX, BIM, BIK (Bcl-2 interacting killer) and NOXA/PMAIP1 (Phorbol-12-myristate-13-acetate-induced protein 1). Overexpression of HIPK2 promoted the phosphorylation of CtBP1 and the degradation of CtBP1 by proteasomes, thereby preventing the formation of the CtBP1-p300-FOXO3a complex. The abolition of CtBP1 transrepression increased the expression of proapoptotic genes to induce apoptosis and increase chemosensitivity in osteosarcoma cells. Taken together, our in vitro and in vivo results revealed that overexpression of HIPK2 could remove the CtBP1-mediated transrepression of proapoptotic genes, indicating a new therapeutic option for the treatment of osteosarcoma.

Quercetin enhances the antitumor activity of trichostatin A through up-regulation of p300 protein expression in p53 null cancer cells

In the present study, we investigated the p53-independent mechanism by which quercetin (Q) increased apoptosis in human lung cancer H1299 cells exposed to trichostatin A (TSA), a histone deacetylase inhibitor. We also investigated the role of Q in increasing the acetylation of histones H3 and H4 and the possible mechanism. Q at 5 μM significantly increased apoptosis by 88% in H1299 cells induced by TSA at 72 h. Q also significantly increased TSA-induced death receptor 5 (DR5) mRNA and protein expression as well as caspase-10/3 activities in H1299 cells. Transfection of DR5 siRNA into H1299 cells significantly diminished the enhancing effects of Q on TSA-induced apoptosis. Furthermore, TSA in combination with Q rather than TSA alone significantly increased p300 expression. Transfection of p300 siRNA in H1299 cells significantly diminished the increase of histone H3/H4 acetylation, DR5 protein expression, caspase-10/3 activity and apoptosis induced by Q. In addition, similar effects of Q were observed when Q was combined with vorinostat, another FDA-approved histone deacetylase inhibitor. These data suggest that the up-regulation of p300 expression, which in turn increases histone acetylation and DR5 expression, plays an important role in the enhancing effect of Q on TSA/vorinostat- induced apoptosis in H1299 cells.

The p53 activator overcomes resistance to ALK inhibitors by regulating p53-target selectivity in ALK-driven neuroblastomas

Anaplastic lymphoma kinase (ALK) is an oncogenic receptor tyrosine kinase that is activated by gene amplification and mutation in neuroblastomas. ALK inhibitors can delay the progression of ALK-driven cancers, but are of limited use owing to ALK inhibitor resistance. Here, we show that resistance to ALK inhibitor in ALK-driven neuroblastomas can be attenuated by combination treatment with a p53 activator. Either ALK inhibition or p53 activator treatment induced cell cycle arrest, whereas combination treatment induced apoptosis, and prevented tumour relapse both in vitro and in vivo. This shift toward apoptosis, and away from cell-cycle arrest, in the presence of an ALK inhibitor and a p53 activator, is mediated by inhibition of the ALK-AKT-FOXO3a axis leading to a specific upregulation of SOX4. SOX4 cooperates with p53 to upregulate the pro-apoptotic protein PUMA. These data therefore suggest a novel combination therapy strategy for treating ALK-driven neuroblastomas.

DownRegulated SOX4 Expression Suppresses Cell Proliferation, Migration, and Induces Apoptosis in Osteosarcoma In Vitro and In Vivo

The SOX4 transcription factor is involved in various cellular processes, such as embryonic development and differentiation. Deregulated expression of Sox4 in several human cancers has been reported to date, but its biological functions in the progression of osteosarcoma remain unclear. In this study, we found that the expression levels of SOX4 protein were significantly higher in high-grade osteosarcoma tissues and metastatic osteosarcoma tissues. Its overexpression was associated with poor prognosis in osteosarcoma. Knockdown of the SOX4 gene in the osteosarcoma cell lines resulted in decreased cell proliferation, migration, invasion, and induced apoptosis. After SOX4 gene silencing, the protein expression levels of Bax, Caspase-3, and P53 in osteosarcoma cells were significantly elevated, while the protein expression levels of Bcl-2, MMP2, and MMP9 were obviously decreased. In vivo analysis in nude mice further confirmed that knockdown of SOX4 suppressed tumor growth. In conclusion, SOX4 appears to be an important tumor oncogene in the regulation of osteosarcoma cell proliferation, apoptosis, and invasion, and it may be a potential target for effective osteosarcoma therapy.

MiRNAs and piRNAs from bone marrow mesenchymal stem cell extracellular vesicles induce cell survival and inhibit cell differentiation of cord blood hematopoietic stem cells: a new insight in transplantation

Hematopoietic stem cells (HSC), including umbilical cord blood CD34+ stem cells (UCB-CD34+), are used for the treatment of several diseases. Although different studies suggest that bone marrow mesenchymal stem cells (BM-MSC) support hematopoiesis, the exact mechanism remains unclear. Recently, extracellular vesicles (EVs) have been described as a novel avenue of cell communication, which may mediate BM-MSC effect on HSC. In this work, we studied the interaction between UCB-CD34+ cells and BM-MSC derived EVs. First, by sequencing EV derived miRNAs and piRNAs we found that EVs contain RNAs able to influence UCB-CD34+ cell fate. Accordingly, a gene expression profile of UCB-CD34+ cells treated with EVs, identified about 100 down-regulated genes among those targeted by EV-derived miRNAs and piRNAs (e.g. miR-27b/MPL, miR-21/ANXA1, miR-181/EGR2), indicating that EV content was able to modify gene expression profile of receiving cells. Moreover, we demonstrated that UCB-CD34+ cells, exposed to EVs, significantly changed different biological functions, becoming more viable and less differentiated. UCB-CD34+ gene expression profile also identified 103 up-regulated genes, most of them codifying for chemokines, cytokines and their receptors, involved in chemotaxis of different BM cells, an essential function of hematopoietic reconstitution. Finally, the exposure of UCB-CD34+ cells to EVs caused an increased expression CXCR4, paralleled by an in vivo augmented migration from peripheral blood to BM niche in NSG mice. This study demonstrates the existence of a powerful cross talk between BM-MSC and UCB-CD34+ cells, mediated by EVs, providing new insight in the biology of cord blood transplantation.

Effects of microRNA‑338‑3p on morphine‑induced apoptosis and its underlying mechanisms

The aim of the present study was to investigate the effects of microRNA-338-3p (miR-338-3p) on morphine (MP)-induced apoptosis, and its underlying mechanisms. Freshly‑isolated mouse peritoneal macrophages were cultured in vitro and treated with MP following transfection with miR‑338‑3p mimic, inhibitor or controls. miR‑338‑3p expression levels increased significantly following MP treatment (P<0.01). This increase was enhanced following transfection with miR‑338‑3p mimic (P<0.05) and abrogated following transfection with miR‑338‑3p inhibitor (P<0.05). The apoptotic rate increased significantly in groups treated with MP (P<0.05); however, this increase was abrogated by transfection with miR‑338‑3p inhibitor (P<0.05). Bioinformatics software predicted that sex determining region Y‑box 4 (SOX4) was the target gene of miR‑338‑3p and this was verified using a dual‑luciferase reporter gene system. SOX4 mRNA and protein expression levels decreased significantly following MP treatment (P<0.05); however, this decrease was abrogated following transfection with miR‑338‑3p inhibitor (P<0.05). Caspase‑3 protein expression levels increased markedly following MP treatment (P<0.05); however, this increase was inhibited by transfection with miR‑338‑3p inhibitor (P<0.05). Therefore, decreased expression of miR‑338‑3p may suppress MP‑induced apoptosis, potentially via the upregulation of SOX4 expression and the caspase‑3‑dependent apoptotic signaling pathway.

Upregulation of microRNA-204 inhibits cell proliferation, migration and invasion in human renal cell carcinoma cells by downregulating SOX4

MicroRNA-204 (miR-204) has been reported to be frequently downregulated in various types of cancer, including renal, brain, ovary, hematological and colon cancer. The present study, investigated the effects of miR‑204 on renal cell carcinoma. Following transfection of miR‑204, an MTT assay, cell migration assay, cell invasion assay, western blot analysis and luciferase assay were performed in renal cell carcinoma cell lines. It was demonstrated that miR‑204 inhibits cell proliferation, migration and invasion in 786‑O and A498 cells. To the best of our knowledge, this study is the first to demonstrate that miR‑204 directly targets SOX4 in renal cell carcinoma. These results suggested that miR-204 may have value as a marker for the early detection of tumor metastasis and a therapeutic target preventing the invasion of renal cell carcinoma.

Transcriptional regulatory network of SOX4 during myoblast differentiation

The construction of transcriptional regulatory networks of transcription factors (TFs) has become more important and attractive to understand the alterations of binding protein-dependent transcriptional activity that governs the changes in spatiotemporal expression of TF target genes required in various cellular processes. Therefore, identification of new inner modules including target genes and protein interactions involved in unveiled TF-based transcription networks is currently in the research spotlight. In this study, we reveal a possible SOX4-centered transcriptional network by the identification of novel binding partners and target genes of the TF SOX4 using various screening techniques. Lamin B2, barrier to autointegration factor 1, and apolipoprotein C-III were identified as novel interacting partners of SOX4 by yeast two-hybrid screening, and the genes encoding lysosomal-associated membrane protein 1, ubiquitin-conjugating enzyme E2S, and Map2k2 were identified as putative target genes of SOX4. Differently from the computational networks of TFs, we revealed a SOX4-centered physical network during myoblast differentiation. These results will provide opportunities to better understand the SOX4-centered transcriptional regulation network and TF-based specific gene expression in various cellular environments.

SOX4 inhibits GBM cell growth and induces G0/G1 cell cycle arrest through Akt-p53 axis

Background

SOX4 is a transcription factor required for tissue development and differentiation in vertebrates. Overexpression of SOX4 has been reported in many cancers including glioblastoma multiforme (GBM), however, the underlying mechanism of actions has not been studied. In this study, we investigated the role of SOX4 in GBM.

Methods

Kaplan-Meier analysis was performed to assess the association between SOX4 expression levels and survival times in primary GBM samples. Cre/lox P system was used to generate gain or loss of SOX4 in GBM cells, and microarray analysis uncovered the regulation network of SOX4 in GBM cells.

Results

High SOX4 expression was significantly associated with good prognosis of primary GBMs. SOX4 inhibited the growth of GBM cell line LN229, A172G and U87MG, partly via the activation of p53-p21 signaling and down-regulation of phosphorylated AKT1. Gene expression profiling and subsequent gene ontology analysis showed that SOX4 influenced several key pathways including the Wnt/ beta-catenin and TGF-beta signaling pathways.

Conclusions

Our study found that SOX4 acts as a tumor suppressor in GBM cells by induce cell cycle arrest and inhibiting cell growth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-014-0207-y) contains supplementary material, which is available to authorized users.