Purpose: CD44 is one of the most common markers used for identification of highly tumorigenic subpopulations of human carcinoma cells, but little is known about the function of CD44 or its major ligand, hyaluronan, in these cells. The purpose of this study was to investigate the involvement of hyaluronan and its interaction with CD44 in the properties of a tumorigenic subpopulation of primary ovarian carcinoma cells. Experimental Design: A tumorigenic subpopulation was identified in ascites fluids from ovarian carcinoma patients by expression of high CD133 levels. Treatment with small hyaluronan oligosaccharides, which dissociate constitutive hyaluronan polymer-CD44 interactions, was used to test the importance of hyaluronan-CD44 interaction in assembly of multidrug and monocarboxylate transporters and receptor tyrosine kinases in the plasma membrane of cells with high CD133 levels, and in the tumorigenic capacity of the CD133-high subpopulation. Results: Although total CD44 levels were similar in cells with high or low CD133 expression, CD44 was present in close association with transporters, receptor tyrosine kinases, and emmprin (CD147) in the plasma membrane of cells with high CD133 levels. Treatment with small hyaluronan oligosaccharides reduced association of the transporters and receptor tyrosine kinases with CD44 in the plasma membrane, diminished drug transporter activity, and inhibited i.p. tumorigenesis in these cells. Conclusions: We conclude that hyaluronan-CD44 interaction plays an important role in the properties of highly tumorigenic cells by stabilizing oncogenic complexes in their plasma membrane, and that treatment with hyaluronan-CD44 antagonists provides a logical therapeutic approach for abrogating the properties of these cells. (Clin Cancer Res 2009;15(24):7593-601)

Background: CD147 induces invadopodia activity and invasiveness in breast epithelial cells. Results: CD147 forms complexes with CD44 and EGFR in lipid raftlike membrane domains and induces hyaluronan-CD44-dependent EGFR-Ras-ERK signaling that promotes invadopodia activity and invasiveness. Conclusion: CD147 induces signaling complexes critical to invasiveness in breast epithelial cells. Significance: CD147 is a potential therapeutic target and disease marker in breast cancer.

Malignant peripheral nerve sheath tumors (MPNST) develop in ~10% of neurofibromatosis type-1 patients and are a major contributing factor to neurofibromatosis-1 patient mortality and morbidity. MPNSTs are multidrug resistant, and thus long-term patient survival rates are poor after standard doxorubicin or multiagent chemotherapies. We show that the hyaluronan receptor CD44 forms complexes with multidrug transporters, BCRP (ABCG2) and P-glycoprotein (ABCB1), in the plasma membrane of human MPNST cells. Small hyaluronan oligosaccharides antagonize hyaluronan-CD44–mediated processes and inhibit hyaluronan production. Treatment of MPNST cells with the hyaluronan oligomers causes disassembly of CD44-transporter complexes and induces internalization of CD44, BCRP, and P-glycoprotein. Consequently, the oligomers suppress drug transporter activity and increase sensitivity to doxorubicin treatment in culture. In vivo, systemic administration of hyaluronan oligomers inhibits growth of MPNST xenografts. Moreover, the oligomers and doxorubicin act synergistically in vivo, in that combined suboptimal doses induce tumor regression to a greater extent than the additive effects of each agent alone. These findings indicate that constitutive hyaluronan-CD44 interactions contribute to drug transporter localization and function at the plasma membrane, and that attenuating hyaluronan-CD44 interactions sensitizes MPNSTs to doxorubicin in vitro and in vivo. These results also show the potential efficacy of hyaluronan oligomers, which are nontoxic and nonimmunogenic, as an adjuvant for chemotherapy in MPNST patients.

Purpose: To determine if hyaluronan oligomers (o-HA) antagonize the malignant properties of glioma cells and treatment-resistant glioma side population (SP) cells in vitro and in vivo. Experimental Design: A single intratumoral injection of o-HA was given to rats bearing spinal cord gliomas 7 days after engraftment of C6 glioma cells. At 14 days, spinal cords were evaluated for tumor size, invasive patterns, proliferation, apoptosis, activation of Akt, and BCRP expression. C6SP were isolated by fluorescence-activated cell sorting and tested for the effects of o-HA on BCRP expression, activation of Akt and epidermal growth factor receptor, drug resistance, and glioma growth in vivo. Results: o-HA treatment decreased tumor cell proliferation, increased apoptosis, and downregulated activation of Akt and the expression of BCRP. o-HA treatment of C6SP inhibited activation of epidermal growth factor receptor and Akt, decreased BCRP expression, and increased methotrexate cytotoxicity. In vivo, o-HA also suppressed the growth of gliomas that formed after engraftment of C6 or BCRP+ C6SP cells, although most C6SP cells lost their expression of BCRP when grown in vivo. Interestingly, the spinal cord gliomas contained many BCRP+ cells that were not C6 or C6SP cells but that expressed nestin and/or CD45; o-HA treatment significantly decreased the recruitment of these BCRP+ progenitor cells into the engrafted gliomas. Conclusions: o-HA suppress glioma growth in vivo by enhancing apoptosis, down-regulating key cell survival mechanisms, and possibly by decreasing recruitment of host-derived BCRP+ progenitor cells. Thus, o-HA hold promise as a new biological therapy to inhibit HA-mediated malignant mechanisms in glioma cells and treatment-resistant glioma stem cells. Malignant gliomas are common central nervous system (CNS)tumors, and regrettably, the most aggressive subtype glioblastoma multiforme makes up >50% of newly diagnosed cases. Glioblastoma multiforme cells progressively and irreversibly infiltrate the normal CNS, and tumors are highly resistant to radiotherapy and chemotherapy. The infiltration of the brain or spinal cord by malignant gliomas is pathologically evident by the juxtaposition of normal cellular elements with relatively isolated tumor cells at the periphery of the glioma in white matter tracts, around neurons, and under the pia (so-called Sherer's structures).Glioma cell interactions with the extracellular matrix facilitate their invasiveness and dispersal throughout the CNS. In contrast to most other tissues, the CNS extracellular matrix is organized by interactions of its components with hyaluronan (HA; refs. 1 -3), a large, linear glycosaminoglycan that is especially concentrated in regions of high cell division and invasion. Moreover, HA expression and signaling are elevated in the matrices of many tumor types, including gliomas (4). Glioma cells produce matrix that is highly enriched in HA (5, 6), and these cells express high levels of the HA receptors CD44 and receptor for HA-mediated motili...

Summary Efforts to identify pharmaceuticals to treat heritable metabolic liver diseases have been hampered by the lack of models. However, cells with hepatocyte characteristics can be produced from induced pluripotent stem cells (iPSCs). Here we have used hepatocyte–like cells generated from homozygous familial hypercholesterolemia (hoFH) iPSCs to identify drugs that can potentially be repurposed to lower serum LDL-C. We found that cardiac glycosides reduce the production of apolipoprotein B (apoB) from human hepatocytes in culture and the serum of avatar mice harboring humanized livers. The drugs act by increasing the turnover of apoB protein. Analyses of patient medical records revealed that the treatment of patients with cardiac glycosides reduced serum LDL-C levels. These studies highlight the effectiveness of using iPSCs to screen for potential treatments for inborn errors of hepatic metabolism and suggest that cardiac glycosides could provide an approach for reducing hepatocyte production of apoB and treating hypercholesterolemia.