SOX11 Inhibitors Are Cytotoxic in Mantle Cell Lymphoma.

PURPOSE: Mantle cell lymphoma (MCL) is a fatal subtype of non-Hodgkin lymphoma. SOX11 transcription factor is overexpressed in the majority of nodal MCL. We have previously reported that B cell-specific overexpression of SOX11 promotes MCL pathogenesis via critically increasing BCR signaling in vivo. SOX11 is an attractive target for MCL therapy; however, no small-molecule inhibitor of SOX11 has been identified to date. Although transcription factors are generally considered undruggable, the ability of SOX11 to bind to the minor groove of DNA led us to hypothesize that there may exist cavities at the protein-DNA interface that are amenable to targeting by small molecules. EXPERIMENTAL DESIGN: Using a combination of in silico predictions and experimental validations, we report here the discovery of three structurally related compounds (SOX11i) that bind SOX11, perturb its interaction with DNA, and effect SOX11-specific anti-MCL cytotoxicity. RESULTS: We find mechanistic validation of on-target activity of these SOX11i in the inhibition of BCR signaling and the transcriptional modulation of SOX11 target genes, specifically, in SOX11-expressing MCL cells. One of the three SOX11i exhibits relatively superior in vitro activity and displays cytotoxic synergy with ibrutinib in SOX11-expressing MCL cells. Importantly, this SOX11i induces cytotoxicity specifically in SOX11-positive ibrutinib-resistant MCL patient samples and inhibits Bruton tyrosine kinase phosphorylation in a xenograft mouse model derived from one of these subjects. CONCLUSIONS: Taken together, our results provide a foundation for therapeutically targeting SOX11 in MCL by a novel class of small molecules.

LncRNA LINC00680 promotes lung adenocarcinoma growth via binding to GATA6 and canceling GATA6-mediated suppression of SOX12 expression.

Lung adenocarcinoma (LUAD) is a major subtype of non-small-cell lung cancers (NSCLC). LINC00680 has been characterized as a novel oncogenic lncRNA in LUAD, but its regulatory mechanisms remain largely unclear. This study aimed to explore the subcellular localization of LINC00680 in LUAD and its regulation on the transcriptional process. LUAD cell lines (A549, H1650, and H1299) were used for in vitro and in vivo studies. Results showed LINC00680 depletion resulted in G0/G1 phase arrest of LUAD cells and reduced CDK4 and cyclin D1 expression in H1650 and H1299 cells. LINC00680 overexpression promoted A549 cell proliferation and increased CDK4 and cyclin D1 expression. RNA-fluorescence in situ hybridization (FISH) assay showed that LINC00680 has both cytoplasmic and nuclear distribution in LUAD cells. RNA pulldown and western blotting assays confirmed a physical interaction between LINC00680 and GATA6. In LUAD cells, GATA6 overexpression only slightly suppressed SOX12 transcription. ChIP-qPCR and dual-luciferase assay showed that GATA6 only weakly bound to the SOX12 promoter and decreased its activity. However, when LINC00680 was depleted, these transcriptional suppressive effects were significantly enhanced. These findings suggested that LINC00680 forms a complex with GATA6 and weakens its transcriptional suppressive effect on SOX12 expression. In the nude mice model, LINC00680 overexpression partly abrogated the growth-suppressive effects of GATA6 on A549 derived tumors. In summary, this study revealed a novel LINC00680-GATA6-SOX12 axis in promoting LUAD cell cycle progression and proliferation. Future studies should be conducted for a better understanding of the complex networking of LINC00680 in LUAD.

Functional Regulatory Mechanisms Underlying Bone Marrow Mesenchymal Stem Cell Senescence During Cell Passages.

Mesenchymal stem cell (MSC) transplantation is an effective periodontal regenerative therapy. MSCs are multipotent, have self-renewal ability, and can differentiate into periodontal cells. However, senescence is inevitable for MSCs. In vitro, cell senescence can be induced by long-term culture with/without cell passage. However, the regulatory mechanism of MSC senescence remains unclear. Undifferentiated MSC-specific transcription factors can regulate MSC function. Herein, we identified the regulatory transcription factors involved in MSC senescence and elucidated their mechanisms of action. We cultured human MSCs (hMSCs) with repetitive cell passages to induce cell senescence and evaluated the mRNA and protein expression of cell senescence-related genes. Additionally, we silenced the cell senescence-induced transcription factors, GATA binding protein 6 (GATA6) and SRY-box 11 (SOX11), and investigated senescence-related signaling pathways. With repeated passages, the number of senescent cells increased, while the cell proliferation capacity decreased; GATA6 mRNA expression was upregulated and that of SOX11 was downregulated. Repetitive cell passages decreased Wnt and bone morphogenetic protein (BMP) signaling pathway-related gene expression. Silencing of GATA6 and SOX11 regulated Wnt and BMP signaling pathway-related genes and affected cell senescence-related genes; moreover, SOX11 silencing regulated GATA6 expression. Hence, we identified them as pair of regulatory transcription factors for cell senescence in hMSCs via the Wnt and BMP signaling pathways.

Upregulation of SOX11 enhances tamoxifen resistance and promotes epithelial-to-mesenchymal transition via slug in MCF-7 breast cancer cells.

Resistance to tamoxifen remains a prominent conundrum in the therapy of hormone-sensitive breast cancer. Also, the molecular underpinnings leading to tamoxifen resistance remain unclear. In the present study, we utilized the Gene Expression Omnibus database to identify that SOX11 might exert a pivotal function in conferring tamoxifen resistance of breast cancer. SOX11 was found to be markedly upregulated at both the messenger RNA and protein levels in established MCF-7-Tam-R cells compared to the parental counterparts. Moreover, SOX11 was able to activate the transcription of slug via binding to its promoter, resulting in promoting the progress of epithelial-to-mesenchymal transition and suppressing the expression of ESR1. Downregulating SOX11 expression can restore the sensitivity to 4-hydroxytamoxifen in MCF-7-Tam-R cells. Survival analysis from large sample datasets indicated that SOX11 was closely related to poorer survival in patients with breast cancer. These findings suggest a novel feature of SOX11 in contributing to tamoxifen resistance. Hence, targeting SOX11 could be a potential therapeutic strategy to tackle tamoxifen resistance in breast cancer.

SOX4: The unappreciated oncogene.

SOX4 is an essential developmental transcription factor that regulates stemness, differentiation, progenitor development, and multiple developmental pathways including PI3K, Wnt, and TGFß signaling. The SOX4 gene is frequently amplified and overexpressed in over 20 types of malignancies, and multiple lines of evidence support that notion that SOX4 is an oncogene. Its overexpression is due to both gene amplification and to activation of PI3K, Wnt, and TGFß pathways that SOX4 regulates. SOX4 interacts with multiple other transcription factors, rendering many of its impacts on gene expression context and tissue-specific. Nevertheless, there are common themes that run through many of the effects of SOX4 hyperactivity, such as the promotion of cell survival, stemness, the epithelial to mesenchymal transition, migration, and metastasis. Specific targeting of SOX4 remains a challenge for future cancer research and drug development.

SOX4 regulates invasion of bladder cancer cells via repression of WNT5a.

Sry­Related HMG­BOX­4 (SOX4) is a developmental transcription factor that is overexpressed in as many as 23% of bladder cancer patients; however, the role of SOX4 in bladder cancer tumorigenesis is not yet well understood. Given the many roles of SOX4 in embryonic development and the context­dependent regulation of gene expression, in this study, we sought to determine the role of SOX4 in bladder cancer and to identify SOX4­regulated genes that may contribute to tumorigenesis. For this purpose, we employed a CRISPR interference (CRISPRi) method to transcriptionally repress SOX4 expression in T24 bladder cancer cell lines, 'rescued' these cell lines with the lentiviral­mediated expression of SOX4, and performed whole genome expression profiling. The cells in which SOX4 was knocked down (T24­SOX4­KD) exhibited decreased invasive capabilities, but no changes in migration or proliferation, whereas rescue experiments with SOX4 lentiviral vector restored the invasive phenotype. Gene expression profiling revealed 173 high confidence SOX4­regulated genes, including WNT5a as a potential target of repression by SOX4. Treatment of the T24­SOX4­KD cells with a WNT5a antagonist restored the invasive phenotype observed in the T24­scramble control cells and the SOX4 lentiviral­rescued cells. High WNT5a expression was associated with a decreased invasion and WNT5a expression inversely correlated with SOX4 expression, suggesting that SOX4 can negatively regulate WNT5a levels either directly or indirectly and that WNT5a likely plays a protective role against invasion in bladder cancer cells.

Sublytic C5b-9 Induces Glomerular Mesangial Cell Apoptosis Through miR-3546/SOX4/Survivin Axis in Rat Thy-1 Nephritis.

BACKGROUND/AIMS: The activation of complement system and the formation of C5b-9 complex have been confirmed in the glomeruli of patients with mesangioproliferative glomerulonephritis (MsPGN). However, the role and mechanism of C5b-9-induced injury in glomerular mesangial cell (GMC) are poorly understood. Rat Thy-1N is an animal model for studying MsPGN. It has been revealed that the attack of C5b-9 to the GMC in rat Thy-1N is sublytic, and sublytic C5b-9 can cause GMC apoptosis, but the underlying mechanism is not fully elucidated. To explore the role and regulatory mechanism of C5b-9 in MsPGN lesion, we used rat Thy-1N model and first detected the change of microRNA (miRNA) profiles both in Thy-1N rat renal tissues (in vivo) and in the cultured GMCs with sublytic C5b-9 stimulation (in vitro). Then we determined the effect of miR-3546, which increased both in vivo and in vitro, on GMC apoptosis upon sublytic C5b-9 as well as the involved mechanism. METHODS: Rat Thy-1N model was established and GMCs were treated with sublytic C5b-9. The rat renal cortex and the stimulated GMCs were obtained for miRNA microarray detection. Subsequently, the increased miRNAs were verified by real-time PCR. Meanwhile, to ascertain the ability of some miRNAs to upregulate cleaved caspase 3 and induce GMC apoptosis, the corresponding miRNA mimics were transfected into GMCs, followed by western blotting (WB) and flow cytometry mesurement. Thereafter, the miR-3546-targeted gene (SOX4) was predicted using bioinformatics approaches, and SOX4 expression in Thy-1N tissues and in the GMCs upon sublytic C5b-9 stimulation or miR-3546 mimic/inhibitor transfection were detected using real-time PCR and WB. To prove that miR-3546 can affect SOX4 gene transcription and SOX4 can regulate survivin expression, dual luciferase reporter assay, real-time PCR, WB and chromatin immunoprecipitation (ChIP) assays were performed. Furthermore, the role of miR-3546/SOX4/survivin axis in the GMC apoptosis induced by sublytic C5b-9 was examined using WB and flow cytometry. RESULTS: Compared with normal renal tissues and untreated GMCs, there were 43 and 62 upregulated miRNAs (> 2-fold) in Thy-1N tissues and sublytic C5b-9-stimulated GMCs respectively. A total of 17 miRNAs were increased both in vivo and in vitro, 11 of which were validated by real-time PCR. Among them, miR-3546 could markedly promote GMC apoptosis and inhibit SOX4 or survivin expression in response to sublytic C5b-9, and either SOX4 or survivin overexpression markedly rescued the GMC apoptosis mediated by miR-3546 mimic. Additionally, SOX4 overexpression could reverse the survivin suppression by miR-3546 mimic, and SOX4 could bind to survivin promoter (-1,278 to -853 nt) and activate survivin gene transcription. CONCLUSION: MiR-3546/ SOX4/survivin axis has a promoting role in the GMC apoptosis triggered by sublytic C5b-9, and our findings may provide a new insight into the pathogenesis of rat Thy-1N and human MsPGN.

Inhibition of SOX4 induces melanoma cell apoptosis via downregulation of NF-κB p65 signaling.

SOX4 (SRY Box 4) has attracted attention due to its important effects on cell growth, proliferation and apoptosis, among other cellular processes. However, the role of SOX4 in melanoma cell apoptosis remains unclear. In the present study, we investigated whether inhibition of SOX4 induces melanoma cell apoptosis, and explored the possible mechanism involving the NF-κB signaling pathway. SOX4 was knocked down using a lentivirus in melanoma A2058 and SK-MEL-5 cell lines. Cell proliferation was measured by MTT assay. Apoptosis was determined by flow cytometry. Western blotting was performed to detect the protein levels of SOX4, p65 and apoptosis-related proteins, such as PARP, Bcl-2, Bax and survivin. Quantitative real-time PCR (qRT-PCR) was used to examine the mRNA levels of SOX4 and p65. To determine whether SOX4 is able to bind to the promoter of p65, a CHIP-PCR assay was performed. Our data demonstrated that SOX4 knockdown significantly induced apoptosis in melanoma cells, which was accompanied by increases in cleaved PARP and Bax, and decreases in Bcl-2 and survivin. The expression of p65 was also decreased in SOX4-knockdown melanoma cells. The CHIP-PCR assay indicated that SOX4 was able to bind to the promoter region of p65. We also observed that apoptosis in SOX4-knockdown and p65-overexpressing A2058 cells was much lower than that in SOX4-knockdown alone cells. This revealed that the overexpression of p65 partially reversed SOX4 downregulation-induced apoptosis. In conclusion, our results demonstrated that inhibition of SOX4 markedly induced melanoma cell apoptosis via downregulation of the NF-κB signaling pathway, which thus may be a novel approach for the treatment of melanoma.

Polycomb protein family member CBX7 regulates intrinsic axon growth and regeneration.

Neurons in the central nervous system (CNS) lose their intrinsic ability and fail to regenerate, but the underlying mechanisms are largely unknown. Polycomb group (PcG) proteins, which include PRC1 and PRC2 complexes function as gene repressors and are involved in many biological processes. Here we report that PRC1 components (polycomb chromobox (CBX) 2, 7, and 8) are novel regulators of axon growth and regeneration. Especially, knockdown of CBX7 in either embryonic cortical neurons or adult dorsal root ganglion (DRG) neurons enhances their axon growth ability. Two important transcription factors GATA4 and SOX11 are functional downstream targets of CBX7 in controlling axon regeneration. Moreover, knockdown of GATA4 or SOX11 in cultured DRG neurons inhibits axon regeneration response from CBX7 downregulation in DRG neurons. These findings suggest that targeting CBX signaling pathway may be a novel approach for promoting the intrinsic regenerative capacity of damaged CNS neurons.

MicroRNA-138 Inhibits Cell Growth, Invasion, and EMT of Non-Small Cell Lung Cancer via SOX4/p53 Feedback Loop.

Many studies have shown that downregulation of miR-138 occurs in a variety of cancers including non-small cell lung cancer (NSCLC). However, the precise mechanisms of miR-138 in NSCLC have not been well clarified. In this study, we investigated the biological functions and molecular mechanisms of miR-138 in NSCLC cell lines, discussing whether it could turn out to be a therapeutic biomarker of NSCLC in the future. In our study, we found that miR-138 is downregulated in NSCLC tissues and cell lines. Moreover, the low level of miR-138 was associated with increased expression of SOX4 in NSCLC tissues and cell lines. Upregulation of miR-138 significantly inhibited proliferation of NSCLC cells. In addition, invasion and EMT of NSCLC cells were suppressed by overexpression of miR-138. However, downregulation of miR-138 promoted cell growth and metastasis of NSCLC cells. Bioinformatics analysis predicted that SOX4 was a potential target gene of miR-138. Next, luciferase reporter assay confirmed that miR-138 could directly target SOX4. Consistent with the effect of miR-138, downregulation of SOX4 by siRNA inhibited proliferation, invasion, and EMT of NSCLC cells. Overexpression of SOX4 in NSCLC cells partially reversed the effect of miR-138 mimic. In addition, decreased SOX4 expression could increase the level of miR-138 via upregulation of p53. Introduction of miR-138 dramatically inhibited growth, invasion, and EMT of NSCLC cells through a SOX4/p53 feedback loop.

MiR-129-5p Inhibits Proliferation and Invasion of Chondrosarcoma Cells by Regulating SOX4/Wnt/ß-Catenin Signaling Pathway.

BACKGROUND/AIMS: Recently, microRNAs (miRNA) have been identified as novel regulators in Chondrosarcoma (CHS). This study was aimed to identify the roles of miR-129-5p-5p in regulation of SOX4 and Wnt/ß-catenin signaling pathway, as well as cell proliferation and apoptosis in chondrosarcomas. MATERIALS AND METHODS: Tissue samples were obtained from chondrosarcoma patients. Immunohistochemistry, real-time quantitative RT-PCR (RT-qPCR) and western blot analysis were performed to detect the expressions of miR-129-5p and SOX4. Luciferase assay was conducted to confirm that miR-129-5p directly targeted SOX4 mRNA. Manipulations of miR-129-5p and SOX4 expression were achieved through cell transfection. Cell proliferation, migration and apoptosis were evaluated by CCK-8 assay, colony forming assay, wound healing assay and flow cytometry in vitro. For in vivo experiment, the tumor xenograft model was established to evaluate the effects of miR-129-5p and SOX4 on chondrosarcomas. RESULTS: The expression of miR-129-5p was significantly down-regulated in chondrosarcoma tissues as well as cells in comparison with normal ones, while SOX4 was over-activated. Further studies suggested that miR-129-5p suppressed cell proliferation, migration and promoted apoptosis by inhibiting SOX4 and Wnt/ß-catenin pathway. CONCLUSION: MiR-129-5p inhibits the Wnt/ß-catenin signaling pathway by targeting SOX4 and further suppresses cell proliferation, migration and promotes apoptosis in chondrosarcomas.

MicroRNA-212 inhibits the metastasis of nasopharyngeal carcinoma by targeting SOX4.

MicroRNAs are important factors in the pathogenic processes of human types of cancers including nasopharyngeal carcinoma (NPC). In the present study, we confirmed that the microRNA-212 expression level was significantly decreased both in NPC tissues and NPC cell lines. Decreased expression of miR-212 was associated with advanced tumor-node-metastasis (TNM) stage and metastasis of NPC. Patients with a lower level of miR-212 had significantly decreased rates of overall and disease-free survival. Functional experiments showed that forced expression of miR-212 inhibited the migration and invasion of NPC cells while inhibition of miR-212 increased the migration and invasion of NPC cells. Furthermore, the results of luciferase assay, qRT-PCR and western blotting showed that SOX4 was the direct downstream target of miR-212 in NPC cells. In addition, we further confirmed that miR-212 exerted its inhibitory influence on the migration and invasion of NPC cells by targeting SOX4.

MicroRNA-140 Inhibits Cell Proliferation in Gastric Cancer Cell Line HGC-27 by Suppressing SOX4.

BACKGROUND Gastric cancer is a malignant tumor with a high morbidity and mortality. MicroRNAs are important regulators of gene expression, influencing the progression of gastric cancer. This study aimed to reveal the role of microRNA-140 (miR-140) in gastric cancer cell proliferation and its potential mechanisms. MATERIAL AND METHODS Gastric cancer tissues and cell lines BGC-823, SGC-7901, and HGC-27 were used to analyze miR-140 levels compared to normal tissues and cell line GES-1. In HGC-27 cells transfected with miR-140 mimic, we performed MTT, colony formation assay, and cell cycle assay by flow cytometry. SOX4, a predicted target of miR-140, was mutated to verify its regulation by miR-140, and was overexpressed to analyze its function in cell proliferation. Doxorubicin treatment was performed to investigate the effect of miR-140 on drug resistance. RESULTS miR-140 was down-regulated in gastric cancer tissues and cell lines, with the lowest expression level in HGC-27. miR-140 overexpression inhibited HGC-27 cell viability and colony formation and resulted in G0/G1 arrest. miR-140 suppressed SOX4 expression via binding to the 3' untranslated region, while the mutant SOX4 could not be regulated. Overexpressing SOX4 led to promoted cell viability, colony formation, and cell cycle progress. miR-140 overexpression also improved the anti-viability effects of doxorubicin, suggesting its potential in reducing the drug resistance of gastric cells. CONCLUSIONS These findings suggest that miR-140 directly inhibits SOX4, which might be one of its mechanisms in suppressing gastric cancer cell proliferation. This study provides a promising therapeutic strategy for treating gastric cancer and facilitates microRNA research in various diseases.

Cops2 promotes pluripotency maintenance by Stabilizing Nanog Protein and Repressing Transcription.

The COP9 signalosome has been implicated in pluripotency maintenance of human embryonic stem cells. Yet, the mechanism for the COP9 signalosome to regulate pluripotency remains elusive. Through knocking down individual COP9 subunits, we demonstrate that Cops2, but not the whole COP9 signalosome, is essential for pluripotency maintenance in mouse embryonic stem cells. Down-regulation of Cops2 leads to reduced expression of pluripotency genes, slower proliferation rate, G2/M cell cycle arrest, and compromised embryoid differentiation of embryonic stem cells. Cops2 also facilitates somatic cell reprogramming. We further show that Cops2 binds to Nanog protein and prevent the degradation of Nanog by proteasome. Moreover, Cops2 functions as transcriptional corepressor to facilitate pluripotency maintenance. Altogether, our data reveal the essential role and novel mechanisms of Cops2 in pluripotency maintenance.

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 miR­204 on renal cell carcinoma. Following transfection of miR­204, 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 miR­204 inhibits cell proliferation, migration and invasion in 786­O and A498 cells. To the best of our knowledge, this study is the first to demonstrate that miR­204 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.

Sox4-mediated caldesmon expression facilitates differentiation of skeletal myoblasts.

Caldesmon (CaD), which was originally identified as an actin-regulatory protein, is involved in the regulation of diverse actin-related signaling processes, including cell migration and proliferation, in various cells. The cellular function of CaD has been studied primarily in the smooth muscle system; nothing is known about its function in skeletal muscle differentiation. In this study, we found that the expression of CaD gradually increased as differentiation of C2C12 myoblasts progressed. Silencing of CaD inhibited cell spreading and migration, resulting in a decrease in myoblast differentiation. Promoter analysis of the caldesmon gene (Cald1) and gel mobility shift assays identified Sox4 as a major trans-acting factor for the regulation of Cald1 expression during myoblast differentiation. Silencing of Sox4 decreased not only CaD protein synthesis but also myoblast fusion in C2C12 cells and myofibril formation in mouse embryonic muscle. Overexpression of CaD in Sox4-silenced C2C12 cells rescued the differentiation process. These results clearly demonstrate that CaD, regulated by Sox4 transcriptional activity, contributes to skeletal muscle differentiation.

Embryonic mammary signature subsets are activated in Brca1-/- and basal-like breast cancers.

INTRODUCTION: Cancer is often suggested to result from development gone awry. Links between normal embryonic development and cancer biology have been postulated, but no defined genetic basis has been established. We recently published the first transcriptomic analysis of embryonic mammary cell populations. Embryonic mammary epithelial cells are an immature progenitor cell population, lacking differentiation markers, which is reflected in their very distinct genetic profiles when compared with those of their postnatal descendents. METHODS: We defined an embryonic mammary epithelial signature that incorporates the most highly expressed genes from embryonic mammary epithelium when compared with the postnatal mammary epithelial cells. We looked for activation of the embryonic mammary epithelial signature in mouse mammary tumors that formed in mice in which Brca1 had been conditionally deleted from the mammary epithelium and in human breast cancers to determine whether any genetic links exist between embryonic mammary cells and breast cancers. RESULTS: Small subsets of the embryonic mammary epithelial signature were consistently activated in mouse Brca1-/- tumors and human basal-like breast cancers, which encoded predominantly transcriptional regulators, cell-cycle, and actin cytoskeleton components. Other embryonic gene subsets were found activated in non-basal-like tumor subtypes and repressed in basal-like tumors, including regulators of neuronal differentiation, transcription, and cell biosynthesis. Several embryonic genes showed significant upregulation in estrogen receptor (ER)-negative, progesterone receptor (PR)-negative, and/or grade 3 breast cancers. Among them, the transcription factor, SOX11, a progenitor cell and lineage regulator of nonmammary cell types, is found highly expressed in some Brca1-/- mammary tumors. By using RNA interference to silence SOX11 expression in breast cancer cells, we found evidence that SOX11 regulates breast cancer cell proliferation and cell survival. CONCLUSIONS: Specific subsets of embryonic mammary genes, rather than the entire embryonic development transcriptomic program, are activated in tumorigenesis. Genes involved in embryonic mammary development are consistently upregulated in some breast cancers and warrant further investigation, potentially in drug-discovery research endeavors.

SOX4 is a direct target gene of FRA-2 and induces expression of HDAC8 in adult T-cell leukemia/lymphoma.

Previously, we have shown that an AP-1 family member, FRA-2, is constitutively expressed in adult T-cell leukemia/lymphoma (ATL) and, together with JUND, upregulates CCR4 and promotes ATL cell growth. Among the identified potential target genes of FRA-2/JUND was SOX4. Here, we examine the expression and function of SOX4 in ATL. SOX4 was indeed consistently expressed in primary ATL cells. FRA-2/JUND efficiently activated the SOX4 promoter via an AP-1 site. Knockdown of SOX4 expression by small interfering RNA (siRNA) strongly suppressed cell growth of ATL cell lines. Microarray analyses revealed that SOX4 knockdown reduced the expression of genes such as germinal center kinase related (GCKR), NAK-associated protein 1 (NAP1), and histone deacetylase 8 (HDAC8). We confirmed consistent expression of GCKR, NAP1, and HDAC8 in primary ATL cells. We also showed direct activation of the HDAC8 promoter by SOX4. Furthermore, siRNA knockdown of GCKR, NAP1, and HDAC8 each significantly suppressed cell growth of ATL cell lines. Taken together, we have revealed an important oncogenic cascade involving FRA-2/JUND and SOX4 in ATL, which leads to the expression of genes such as GCKR, NAP1, and HDAC8.

Sox4 stimulates ß-catenin activity through induction of CK2.

ß-catenin is a key component of the Wnt signaling pathway and the abnormal accumulation of ß-catenin is characteristic of various types of cancer. Here we demonstrate that overexpression of Sox4 enhances ß-catenin/TCF activity by increasing the stability of ß-catenin. Sox4 increased the protein level of ß-catenin and its target gene cyclin D1 in a dose-dependent manner. An siRNA experiment for Sox4 also demonstrated that Sox4 increases the protein levels of ß-catenin and thus activates the Wnt signaling pathway. We found that induction of ß-catenin/TCF activity by Sox4 is caused by stabilization of the ß-catenin protein, but not by induction of ß-catenin transcription. We further demonstrate that the increased level of ß-catenin is caused by induction of CK2. In light of recent evidence that Sox4 expression is activated in the colon and in other tumors with ß-catenin dysregulation, our findings suggest that Sox4 acts as an agonist of Wnt signaling in cancer cells.

Mouse induced glioma-initiating cell models and therapeutic targets.

Both stem cells and cancer cells are thought to be capable of unlimited self-renewal. Moreover, a small number of cancer cells express stem cell markers, including CD133 and ATP-binding cassette transporters through which the cells can pump out anti-cancer drugs or specific fluorescence dyes such as Hoechst33342, suggesting that either cancer cells resemble stem cells or that cancers contain stem cell-like cancer cells, called cancer-initiating cells (CICs) or cancer stem cells. Using the common characteristics of tissue-specific stem cells, malignant tumors and cancer cell lines were shown to contain CICs, which self-renew and are tumorigenic. CICs are also resistant to both irradiation and chemotherapy. These findings suggest that CICs are critical targets for successful therapy. However, CICs have not been well characterized, due to a lack of specific markers. We recently established mouse glioma-initiating cell (GIC) lines by overexpressing oncogenic HRas(L)6¹ in p53-deficient neural cells. These cells form transplantable glioblastoma multiforme (GBM) with features of human GBM when as few as 10 cells are transplanted in vivo, suggesting that these GIC-like cells are enriched in CICs. Characterization of these GICs showed that they expressed little or no Sox11. The overexpression of exogenous Sox11 in GICs blocked their tumorigenesis by inducing their neuronal differentiation, which was accompanied by decreased levels of a novel oncogene, plagl1. These findings suggest that Sox11 and Plagl1 work as a tumor suppressor and oncogene, respectively, in GBM and are potential therapeutic targets.