Background: SOX2 and SOX9 are commonly overexpressed in glioblastoma, and regulate the activity of glioma stem cells (GSCs). Their specific and overlapping roles in GSCs and glioma treatment remain unclear. Methods: SOX2 and SOX9 levels were examined in human biopsies. Gain and loss of function determined the impact of altering SOX2 and SOX9 on cell proliferation, senescence, stem cell activity, tumorigenesis and chemoresistance. Results: SOX2 and SOX9 expression correlates positively in glioma cells and glioblastoma biopsies. High levels of SOX2 bypass cellular senescence and promote resistance to temozolomide. Mechanistic investigations revealed that SOX2 acts upstream of SOX9. mTOR genetic and pharmacologic (rapamycin) inhibition decreased SOX2 and SOX9 expression, and reversed chemoresistance. Conclusions: Our findings reveal SOX2-SOX9 as an oncogenic axis that regulates stem cell properties and chemoresistance. We identify that rapamycin abrogate SOX protein expression and provide evidence that a combination of rapamycin and temozolomide inhibits tumor growth in cells with high SOX2/SOX9.

Lung cancer is the top cause of cancer-related deceases. One of the reasons is the development of resistance to the chemotherapy treatment. In particular, cancer stem cells (CSCs), can escape treatment and regenerate the bulk of the tumor. In this article, we describe a comparison between cancer cells resistant to cisplatin and CSCs, both derived from the non-small-cell lung cancer cell lines H460 and A549. Cisplatin-resistant cells were obtained after a single treatment with the drug. CSCs were isolated by culture in defined media, under nonadherent conditions. The isolated CSCs were clonogenic, could be differentiated into adherent cells and were less sensitive to cisplatin than the original cells. Cisplatin resistant and CSCs were able to generate primary tumors and to metastasize when injected into immunodeficient Nu/Nu mice, although they formed smaller tumors with a larger latency than untreated cells. Notably, under appropriated proportions, CSCs synergized with differentiated cells to form larger tumors. CSCs also showed increased capacity to induce angiogenesis in Nu/Nu mice. Conversely, H460 cisplatin-resistant cells showed increased tendency to develop bone metastasis. Gene expression analysis showed that several genes involved in tumor development and metastasis (EGR1, COX2, MALAT1, AKAP12, ADM) were similarly induced in CSC and cisplatin-resistant H460 cells, in agreement with a close similarity between these two cell populations. Cells with the characteristic growth properties of CSCs were also isolated from surgical samples of 18 out of 44 lung cancer patients. A significant correlation (P = 0.028) was found between the absence of CSCs and cisplatin sensitivity.

DUSP1/MKP1 is a dual-specific phosphatase that regulates MAPKs activity, with an increasingly recognized role in tumor biology. To understand more about the involvement of DUSP1 in lung cancer, we performed gene expression analyses of parental and DUSP1-interfered H460 non-small-cell lung cancer (NSCLC) cells. Downregulation of DUSP1 induced changes in the expression levels of genes involved in specific biological pathways, including angiogenesis, MAP kinase phosphatase activity, cell-cell signaling, growth factor and tyrosine-kinase receptor activity. Changes in the expression of some of these genes were due to modulation of c-Jun-N-terminal kinase and/or p38 activity by DUSP1. Complementary functional assays were performed to focus on the implication of DUSP1 in angiogenesis and metastasis. In H460 cells, interference of DUSP1 resulted in a diminished capacity to invade through Matrigel, to grow tumors in nude mice and also to induce metastasis through tail-vein injection. Furthermore, the angiogenic potential of H460 cells was also impaired, correlating with a decrease in VEGFC production and indicating that DUSP1 could be required to induce angiogenesis. Finally, we studied whether a similar relationship occurred in patients. In human NSCLC specimens, DUSP1 was mainly expressed in those tumor cells close to CD31 vascular structures and a statistically significant correlation was found between VEGFC and DUSP1 expression. Overall, these results provide evidence for a role of DUSP1 in angiogenesis, invasion and metastasis in NSCLC.

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