Citations

ABSTRACTHeparan sulfate proteoglycans (HSPGs) are key components of the extracellular matrix that mediate cell proliferation, invasion, and cellular signaling. The biological functions of HSPGs are linked to their co‐stimulatory effects on extracellular ligands (e.g., WNTs) and the resulting activation of transcription factors that control mammalian development but also associated with tumorigenesis. We examined the expression profile of HSPG core protein syndecans (SDC1–4) and glypicans (GPC1–6) along with the enzymes that initiate or modify their glycosaminoglycan chains in human breast cancer (HBC) epithelial cells. Gene expression in relation to cell proliferation was examined in the HBC cell lines MCF‐7 and MDA‐MB‐231 following treatment with the HS agonist heparin. Heparin increased gene expression of chain initiation and modification enzymes including EXT1 and NDST1, as well as core proteins SDC2 and GPC6. With HS/Wnt interactions established, we next investigated WNT pathway components and observed that increased proliferation of the more invasive MDA‐MB‐231 cells is associated with activation of the Wnt signaling pathway. Specifically, there was substantial upregulation (>5‐fold) of AXIN1, WNT4A, and MYC in MDA‐MB‐231 but not in MCF‐7 cells. The changes in gene expression observed for HSPG core proteins and related enzymes along with the associated Wnt signaling components suggest coordinated interactions. The influence of HSPGs on cellular proliferation and invasive potential of breast cancer epithelial cells are cell and niche specific. Further studies on the interactions between HSPGs and WNT ligands may yield clinically relevant molecular targets, as well as new biomarkers for characterization of breast cancer progression. J. Cell. Biochem. 115: 967–976, 2014. © 2013 Wiley Periodicals, Inc.

Abstract Signaling through fibroblast growth factor receptor one (FGFR1) is a known inducer of proliferation in both embryonic and human adult mesenchymal stem cells (hMSCs) and positively regulates maintenance of stem cell viability. Leveraging the mitogenic potential of FGF2/FGFR1 signaling in stem cells for therapeutic applications necessitates a mechanistic understanding of how this receptor stimulates cell cycle progression. Using small interfering RNA (siRNA) depletion, antibody-inhibition, and small molecule inhibition, we establish that FGFR1 activity is rate limiting for self-renewal of hMSCs. We show that FGFR1 promotes stem cell proliferation through multiple mechanisms that unite to antagonize cyclin-dependent kinase (CDK) inhibitors. FGFR1 not only stimulates c-Myc to suppress transcription of the CDK inhibitors p21Waf1 and p27Kip1, thus promoting cell cycle progression but also increases the activity of protein kinase B (AKT) and the level of S-phase kinase-associated protein 2 (Skp2), resulting in the nuclear exclusion and reduction of p21Waf1. The in vivo importance of FGFR1 signaling for the control of proliferation in mesenchymal progenitor populations is underscored by defects in ventral mesoderm formation during development upon inhibition of its signaling. Collectively, these studies demonstrate that FGFR1 signaling mediates the continuation of MSC growth and establishes a receptor target for enhancing the expansion of mesenchymal progenitors while maintaining their multilineage potential. Stem Cells 2013;31:2724–2736

AbstractRunx2 is the master transcription factor for bone formation. Haploinsufficiency of RUNX2 is the genetic cause of cleidocranial dysplasia (CCD) that is characterized by hypoplastic clavicles and open fontanels. In this study, we found that Pin1, peptidyl prolyl cis–trans isomerase, is a critical regulator of Runx2 in vivo and in vitro. Pin1 mutant mice developed CCD‐like phenotypes with hypoplastic clavicles and open fontanels as found in the Runx2+/− mice. In addition Runx2 protein level was significantly reduced in Pin1 mutant mice. Moreover Pin1 directly interacts with the Runx2 protein in a phosphorylation‐dependent manner and subsequently stabilizes Runx2 protein. In the absence of Pin1, Runx2 is rapidly degraded by the ubiquitin‐dependent protein degradation pathway. However, Pin1 overexpression strongly attenuated uniquitin‐dependent Runx2 degradation. Collectively conformational change of Runx2 by Pin1 is essential for its protein stability and possibly enhances the level of active Runx2 in vivo. J. Cell. Physiol. 228: 2377–2385, 2013. © 2013 Wiley Periodicals, Inc.

AbstractCancer is a multifaceted disease that involves acquisition of genetic mutations, deletions, and amplifications as well as deregulation of epigenetic mechanisms that fine‐tune gene regulation. Key epigenetic mechanisms that include histone modifications, DNA methylation, and non‐coding RNA‐mediated gene silencing are often deregulated in a variety of cancers. Subnuclear localization of key proteins in the interphase nucleus and bookmarking of genes by lineage commitment factors in mitosis—a new dimension to epigenetic control of fundamental biological processes—is also modified in cancer. In this review, we discuss the various aspects of epigenetic control that are operative in a variety of cancers and their potential for risk assessment, early detection, targeted therapy, and personalized medicine. J. Cell. Physiol. 228: 2103–2108, 2013. © 2013 Wiley Periodicals, Inc.

AbstractVorinostat, an oral histone deacetylase inhibitor with antitumor activity, is in clinical trials for hematologic and solid tumors that metastasize and compromise bone structure. Consequently, there is a requirement to establish the effects of vorinostat on tumor growth within bone. Breast (MDA-231) and prostate (PC3) cancer cells were injected into tibias of SCID/NCr mice and the effects of vorinostat on tumor growth and osteolytic disease were assessed by radiography, micro-computed tomography, and histologic and molecular analyses. Vorinostat-treated and control mice without tumors were also examined. Tumor growth in bone was reduced ∼33% by vorinostat with inhibited osteolysis in the first few weeks of the experiment. However, osteolysis became more severe in both the vehicle and vorinostat-treated groups. Vorinostat increased the expression of tumor-derived factors promoting bone resorption, including PTHrP, IL-8, and osteopontin. After 4 weeks of vorinostat therapy, the non–tumor-bearing contralateral femurs and limbs from vorinostat-treated tumor-free SCID mice showed significant bone loss (50% volume density of controls). Thus, our studies indicate that vorinostat effectively inhibits tumor growth in bone, but has a negative systemic effect reducing normal trabecular bone mass. Vorinostat treatment reduces tumor growth in bone and accompanying osteolytic disease as a result of decreased tumor burden in bone. However, vorinostat can promote osteopenia throughout the skeleton independent of tumor cell activity. Mol Cancer Ther; 9(12); 3210–20. ©2010 AACR.