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.

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.

MiR-129-5p Inhibits Proliferation and Invasion of Chondrosarcoma Cells by Regulating SOX4/Wnt/β-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/β-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/β-catenin pathway.

CONCLUSION

MiR-129-5p inhibits the Wnt/β-catenin signaling pathway by targeting SOX4 and further suppresses cell proliferation, migration and promotes apoptosis in chondrosarcomas.

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.