Hyaluronan (HA) is a major glycosaminoglycan in the extracellular matrix whose expression is tightly linked to multidrug resistance and tumor progression. In this study we investigated HA-induced interaction between CD44 (a HA receptor) and Nanog (an embryonic stem cell transcription factor) in both human breast tumor cells (MCF-7 cells) and human ovarian tumor cells (SK-OV-3.ipl cells). Using a specific primer pair to amplify Nanog by reverse transcriptase-PCR, we detected the expression of Nanog transcript in both tumor cell lines. In addition, our results reveal that HA binding to these tumor cells promotes Nanog protein association with CD44 followed by Nanog activation and the expression of pluripotent stem cell regulators (e.g. Rex1 and Sox2). Nanog also forms a complex with the "signal transducer and activator of transcription protein 3" (Stat-3) in the nucleus leading to Stat-3-specific transcriptional activation and multidrug transporter, MDR1 (P-glycoprotein) gene expression. Furthermore, we observed that HA-CD44 interaction induces ankyrin (a cytoskeletal protein) binding to MDR1 resulting in the efflux of chemotherapeutic drugs (e.g. doxorubicin and paclitaxel (Taxol)) and chemoresistance in these tumor cells. Overexpression of Nanog by transfecting tumor cells with Nanog cDNA stimulates Stat-3 transcriptional activation, MDR1 overexpression, and multidrug resistance. Down regulation of Nanog signaling or ankyrin function (by transfecting tumor cells with Nanog small interfering RNA or ankyrin repeat domain cDNA) not only blocks HA/CD44-mediated tumor cell behaviors but also enhances chemosensitivity. Taken together, these findings suggest that targeting HA/CD44-mediated Nanog-Stat-3 signaling pathways and ankyrin/cytoskeleton function may represent a novel approach to overcome chemotherapy resistance in some breast and ovarian tumor cells displaying stem cell marker properties during tumor progression.Multidrug resistance frequently contributes to the failure of chemotherapeutic drug treatments in patients diagnosed with solid tumors such as breast and ovarian cancers (1). It is now certain that oncogenic signaling and cytoskeleton function are directly involved in chemotherapeutic drug resistance and tumor progression (2-4). A number of studies have aimed at identifying those molecules that are expressed specifically by epithelial tumor cells and correlate with metastatic behavior and chemoresistance. Among such molecules is hyaluronan (HA), 2 a major component in the extracellular matrix (ECM) of most mammalian tissues (5, 6). HA is a nonsulfated, unbranched glycosaminoglycan consisting of the repeating disaccharide units, D-glucuronic acid and N-acetyl-D-glucosamine (5, 6). HA is synthesized by specific HA synthases (6, 7) and digested into various smaller sized molecules by various hyaluronidases (8). It is well known that HA is enriched in many types of tumors (9, 10). In cancer patients, HA concentrations are usually higher in malignant tumors than in corresponding benign or normal tissues. Ac...

RhoA is a small GTPase shown to be crucial for cytokinesis, stress fiber formation, and epithelial cell–cell contacts. Analyzing mice with a keratinocyte-restricted deletion of the RhoA gene, we find that RhoA is not required for skin development and maintenance but has specific functions in vitro.

In this study, we have examined the interaction of hyaluronan (HA)-CD44 with IQGAP1 (one of the binding partners for the Rho GTPase Cdc42) in SK-OV-3.ipl human ovarian tumor cells. Immunological and biochemical analyses indicated that IQGAP1 (molecular mass of ϳ190 kDa) is expressed in SK-OV-3.ipl cells and that IQGAP1 interacts directly with Cdc42 in a GTPdependent manner. Both IQGAP1 and Cdc42 were physically linked to CD44 in SK-OV-3.ipl cells following HA stimulation. Furthermore, the HA-CD44-induced Cdc42-IQGAP1 complex regulated cytoskeletal function via a close association with F-actin that led to ovarian tumor cell migration. In addition, the binding of HA to CD44 promoted the association of ERK2 with the IQGAP1 molecule, which stimulated both ERK2 phosphorylation and kinase activity. The activated ERK2 then increased the phosphorylation of both Elk-1 and estrogen receptor-␣ (ER␣), resulting in Elk-1-and estrogen-responsive element-mediated transcriptional up-regulation. Down-regulation of IQ-GAP1 (by treating cells with IQGAP1-specific small interfering RNAs) not only blocked IQGAP1 association with CD44, Cdc42, F-actin, and ERK2 but also abrogated HA-CD44-induced cytoskeletal function, ERK2 signaling (e.g. ERK2 phosphorylation/activity, ERK2-mediated Elk-1/ER␣ phosphorylation, and Elk-1/ ER␣-specific transcriptional activation), and tumor cell migration. Taken together, these findings indicate that HA-CD44 interaction with IQGAP1 serves as a signal integrator by modulating Cdc42 cytoskeletal function, mediating Elk-1-specific transcriptional activation, and coordinating "cross-talk" between a membrane receptor (CD44) and a nuclear hormone receptor (ER␣) signaling pathway during ovarian cancer progression.Ovarian cancer cells are characterized by their ability to freely invade the peritoneal cavity, which is consistent with the well known aggressiveness and high morbidity rate of ovarian tumors (1-3). A number of studies have aimed at identifying specific molecule(s) expressed in ovarian carcinomas that correlate with tumor cell invasive behaviors. Among such candidate molecules is CD44 (a major hyaluronan (HA) 1 receptor) (4), which belongs to a family of multifunctional transmembrane glycoproteins expressed in ovarian tumor cells and carcinoma tissues (5-9). CD44 has been found to interact with HA at the N terminus of its extracellular domain (10 -12). Ovarian cancer cells express CD44 isoforms that cause very strong cell adhesion to HA-enriched peritoneal mesothelium (8,9,13,14). A significant reduction in tumor implants has been found to occur in nude mice 5 weeks after intraperitoneal injection of ovarian cancer cells incubated with anti-CD44 antibody compared with injected cells pretreated with antibodies against other cell-surface proteins (8, 9). These findings suggest that CD44 interaction with HA may be one of the important requirements for the peritoneal spread of ovarian cancer. However, the cellular and molecular mechanisms controlling the ability of CD44-positive ovarian tumor cells to und...

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In the injured spinal cord, a glial scar forms and becomes a major obstacle to axonal regeneration. Formation of the glial scar involves migration of astrocytes toward the lesion. Matrix metalloproteinases (MMPs), including MMP-9 and MMP-2, govern cell migration through their ability to degrade constituents of the extracellular matrix. Although MMP-9 is expressed in reactive astrocytes, its involvement in astrocyte migration and formation of a glial scar is unknown. Here we found that spinal cord injured, wild-type mice expressing MMPs developed a more severe glial scar and enhanced expression of chondroitin sulfate proteoglycans, indicative of a more inhibitory environment for axonal regeneration/plasticity, than MMP-9 null mice. To determine if MMP-9 mediates astrocyte migration, we conducted a scratch wound assay using astrocytes cultured from MMP-9 null, MMP-2 null, and wild-type mice. Gelatin zymography confirmed the expression of MMP-9 and MMP-2 in wild-type cultures. MMP-9 null astrocytes and wild-type astrocytes, treated with an MMP-9 inhibitor, exhibited impaired migration relative to untreated wild-type controls. MMP-9 null astrocytes showed abnormalities in the actin cytoskeletal organization and function but no detectable untoward effects on proliferation, cellular viability, or adhesion. Interestingly, MMP-2 null astrocytes showed increased migration, which could be attenuated in the presence of an MMP-9 inhibitor. Collectively, our studies provide explicit evidence that MMP-9 is integral to the formation of an inhibitory glial scar and cytoskeleton-mediated astrocyte migration. MMP-9 may thus be a promising therapeutic target to reduce glial scarring during wound healing after spinal cord injury.