Frizzled 4 Regulates Stemness and Invasiveness of Migrating Glioma Cells Established by Serial Intracranial Transplantation
ABSTRACT One of the most detrimental hallmarks of glioblastoma multiforme (GBM) is cellular invasiveness, which is considered a potential cause of tumor recurrence. Infiltrated GBM cells are difficult to completely eradicate surgically and with local therapeutic modalities. Although much effort has focused on understanding the various mechanisms controlling GBM invasiveness, its nature remains poorly understood. In this study, we established highly serial intracranial transplantation. U87R4 cells were highly invasive and displayed stem cell-like properties, as compared to noninvasive but proliferative U87L4 cells. Microarray analysis during serial transplantation revealed that apoptosis-inducing genes (caspase3 and PDCD4) were downregulated whereas several cancer stem cell-relevant genes [Frizzled 4 (FZD4) and CD44] were upregulated in more invasive cells. U87R4 cells were resistant to anticancer drug-induced cell death, partly due to downregulation of caspase3 and PDCD4, and they retained activated Wnt/β-catenin signaling due to upregulation of Frizzled 4, which was sufficient to control neurosphere formation. We also found that FZD4 promoted expression of the epithelial to mesenchymal transition regulator SNAI1, along with acquisition of a mesenchymal phenotype. Taken together, our results argue that Frizzled 4 is a member of the Wnt signaling family that governs both stemness and invasiveness of glioma stem cells, and that it may be a major cause of GBM recurrence and poor prognosis.
SourceAvailable from: Keshav Gopal[Show abstract] [Hide abstract]
ABSTRACT: IntroductionAberrant expression of the embryonic stem cell marker Sox2 has been reported in breast cancer (BC). We previously identified two phenotypically distinct BC cell subsets separated based on their differential response to a Sox2 transcription activity reporter, namely the reporter-unresponsive (RU) and the more tumorigenic reporter-responsive (RR) cells. We hypothesized that Sox2, as a transcription factor, contributes to their phenotypic differences by mediating differential gene expression in these two cell subsets.Methods We used chromatin immunoprecipitation and a human genome-wide promoter microarray (ChIP-chip) to determine the promoter occupancies of Sox2 in the MCF7 RU and RR breast cancer cell populations. We validated our findings with conventional chromatin immunoprecipitation, quantitative reverse transcription polymerase chain reaction (qPCR), and western blotting using cell lines, and also performed qPCR using patient RU and RR samples.ResultsWe found a largely mutually exclusive profile of gene promoters bound by Sox2 between RU and RR cells derived from MCF7 (1830 and 456 genes, respectively, with only 62 overlapping genes). Sox2 was bound to stem cell- and cancer-associated genes in RR cells. Using quantitative RT-PCR, we confirmed that 15 such genes, including PROM1 (CD133), BMI1, GPR49 (LGR5), and MUC15, were expressed significantly higher in RR cells. Using siRNA knockdown or enforced expression of Sox2, we found that Sox2 directly contributes to the higher expression of these genes in RR cells. Mucin-15, a novel Sox2 downstream target in BC, contributes to the mammosphere formation of BC cells. Parallel findings were observed in the RU and RR cells derived from patient samples.Conclusions In conclusion, our data supports the model that the Sox2 induces differential gene expression in the two distinct cell subsets in BC, and contributes to their phenotypic differences.Breast cancer research: BCR 11/2014; 16(6):470. DOI:10.1186/s13058-014-0470-2 · 5.88 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Cancer stem-like cells (CSC) thought to contribute to head and neck squamous carcinomas (HNSCC) may offer attractive therapeutic targets if a tractable approach can be developed. In this study, we report that silencing c-Met is sufficient to suppress sphere formation, tumor initiation and metastatic properties of HN-CSC. Pharmacologic inhibition of c-Met with the selective inhibitor PF-2341066 preferentially targeted CSC and synergized with conventional chemotherapy to improve efficacy in a mouse xenograft model of HNSCC, impeding tumor growth and reducing metastasis. Mechanistic investigations showed that CSC elimination was due to downregulation of Wnt/β-catenin signaling in HN-CSC and that the Wnt pathway receptor FZD8 was essential for interactions of c-Met and Wnt/β-catenin signaling in HN-CSC. Notably, ectopic expression of FZD8 rescued the impaired phenotype of HN-CSC where c-Met was inhibited. Furthermore, c-Met upregulated FZD8 through the ERK/c-Fos cascade in HN-CSC. Taken together, our results offer a preclinical proof-of-concept for targeting the c-Met/FZD8 signaling axis as a CSC-directed therapy to improve HNSCC treatment.Cancer Research 10/2014; 74(24). DOI:10.1158/0008-5472.CAN-14-0826 · 9.28 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Pleural chronic inflammation (PP) and mesothelial hyperplasia (HP) may be critical to the development of malignant pleural mesothelioma (MPM). Nonetheless, studies searching for mechanistic links involving microRNA (miRNA) regulation among these interrelated processes have not been reported. Using PCR-Array, we identified the miRNAs expressed in pleural tissues diagnosed with MPM (n = 5), PP (n = 4) and HP (n = 5), as well as in non-cancerous/non-inflammatory tissue as the normal control (n = 5). We performed bioinformatics and network analysis of differentially expressed miRNAs to identify tumorigenesis-related miRNAs and their biological networks. The targets of four down-regulated miRNAs in MPM (mir-181a-5p, miR-101-3p, miR-145-5p and miR-212-3p), one in PP (mir-101-3p) and one in HP (mir-494) were significantly enriched in “pathways in cancer”. Interactome networks revealed that > 50% of down-regulated miRNAs in MPM targeted the signaling-activation molecule MAPK1, the transcription factor ETS1 and the mesenchymal transition-associated molecule FZDA, which have been associated with oncogenic function. Comparative analysis revealed that FZD4 was an overlapping gene target of down-regulated miRNAs that were associated with “pathways in cancer” in MPM, PP and HP. Moreover, MAPK1, ETS1 and Cox-2, a pro-inflammatory enzyme associated with over-expression in cancers, were among the 25 overlapping target genes in MPM and PP. This network analysis revealed a potential combinatory effect of deregulated miRNAs in MPM pathogenesis and indicated potential molecular links between pleural inflammation and hyperplasia with tumorigenesis mechanisms in pleura.Experimental and Molecular Pathology 12/2014; 97(3). DOI:10.1016/j.yexmp.2014.09.016 · 2.88 Impact Factor