The hyaluronan receptor RHAMM regulates extracellular-regulated kinase

Overexpression of the receptor for hyaluronic acid mediated motility is an independent adverse prognostic factor in colorectal cancer

RHAMM, a member of the microtubule-associated protein family that interacts with the mitogen-activated protein kinase pathway, is associated with tumor progression, aggressive disease and shortened survival in several tumor types. This study aimed to determine the prognostic value of RHAMM in colorectal cancer (CRC). A series of 1420 unselected, nonconsecutive CRC resections were subdivided into three groups: (1) DNA mismatch repair (MMR)-proficient, (2) MLH1 negative and (3) presumed Lynch syndrome. Immunohistochemical analysis of RHAMM expression (0 vs >0%), increasing expression (increasing percentage positivity) and complete expression (100 vs <100%) was performed using tissue microarray technique and the results were correlated with clinicopathological parameters. Fifty-seven tissue samples of normal colonic mucosa were included as a control group. In a univariate analysis increasing and complete expression of RHAMM were associated with higher N stage (P=0.023 and 0.021) and worse survival (P<0.0001) in MMR-proficient CRC. Complete expression of RHAMM was associated with worse survival in presumed Lynch syndrome (P=0.016). In MLH1-negative CRC there was no association between RHAMM expression and the clinicopathological features. In a multivariate analysis, increasing RHAMM expression was an independent adverse prognostic factor in MMR-proficient CRC (P<0.0001) and complete expression in MMR-proficient CRC and presumed Lynch syndrome (P<0.0001 and P=0.031, respectively). Nuclear pERK expression was associated with increasing RHAMM expression in MMR-proficient CRC (P=0.012) and with complete RHAMM expression in presumed HNPCC (P=0.03). Increasing and complete RHAMM expressions are independent adverse prognostic factors in MMR-proficient CRC and presumed Lynch syndrome.

Hyaluronan-mediated angiogenesis in vascular disease: uncovering RHAMM and CD44 receptor signaling pathways

The correct formation of new blood vessels from existing vasculature (angiogenesis) is essential for embryogenesis and the effective repair of damaged or wounded tissues. However, excessive and detrimental vascularization also occurs in neoplasia, promoting tumour growth and metastasis, as well as in proliferative diabetic retinopathy and atherosclerosis. Greater understanding of the mechanisms controlling the angiogenic process will allow optimization of wound healing, and provide mechanisms to inhibit vascularization in tumours and other diseases. Evidence supports a cascade of events in which the perturbation of one of the steps is sufficient to significantly inhibit neovascularization. The extracellular macromolecules, notably glycosaminoglycans (GAGs), are important mediators of angiogenesis. Hyaluronan (HA), a large, non-sulphated GAG, was first discovered in the vitreous of the eye [.], and is ubiquitously expressed in the extracellular matrix (ECM) of tissues. Native high molecular weight HA (n-HA) is anti-angiogenic, whereas HA degradation products (o-HA; 3-10 disaccharides) stimulate endothelial cell (EC) proliferation, migration and tube formation following activation of specific HA receptors in particular, CD44 and Receptor for HA-Mediated Motility (RHAMM, CD168). The involvement of HA in the regulation of angiogenesis makes it an attractive therapeutic target. We review the role of o-HA in modulation of angiogenesis during tissue injury, and vascular disease, focusing on receptor-mediated signal transduction pathways that have been evaluated.

Effects of hyaluronan, BSA, and serum on bovine embryo in vitro development, ultrastructure, and gene expression patterns

Effects of hyaluronan (HA), BSA, and FCS on in vitro development, ultrastructure, and mRNA transcription of four developmentally important genes: apoptosis (Bax), oxidative stress (SOX), growth factor (IGF-II), and cell-to-cell adhesion (Ecad) were examined. Two biological origin HA, Hylartil and Hyonate and one produced by fermentation (f-HA) MAP-5 were tested. Embryos were cultured in SOF medium with 0.4% BSA or with 0.4% BSA and 10% FCS. HA was added 96 hr post insemination (pi) to half of the embryos from each culture group. Embryo development was not affected by either HA preparation, however, hatching rates were higher in Hyalartil and MAP-5 than in control and Hyonate (P < 0.05). There was no effect of HA on number of blastocysts developed in SOF + BSA. However, more blastocysts developed in SOF + BSA + f-HA than in SOF + BSA + FCS or with BSA + FCS + f-HA. HA added to SOF + BSA, increased level of expression of epidermal growth factor (EGF)-II and decreased the levels of expression of BAX, SOX, and Ecad (P < 0.05). Presence of FCS increased the levels of SOX and decreased the level of IGF-II (P < 0.05) and the addition of f-HA to SOF containing FCS showed no effect on the level of transcription of any analyzed genes. The fine structure of embryos cultured with f-HA irrespective of protein sources used was clearly improved. In summary, f-HA added 96 hr pi to SOF supplemented with BSA but not FCS improved development, molecular composition and fine structure of bovine embryos.

Hyaluronan fragments: an information-rich system

Hyaluronan is a straight chain, glycosaminoglycan polymer of the extracellular matrix composed of repeating units of the disaccharide [-D-glucuronic acid-beta1,3-N-acetyl-D-glucosamine-beta1,4-]n. Hyaluronan is synthesized in mammals by at least three synthases with products of varying chain lengths. It has an extraordinary high rate of turnover with polymers being funneled through three catabolic pathways. At the cellular level, it is degraded progressively by a series of enzymatic reactions that generate polymers of decreasing sizes. Despite their exceedingly simple primary structure, hyaluronan fragments have extraordinarily wide-ranging and often opposing biological functions. There are large hyaluronan polymers that are space-filling, anti-angiogenic, immunosuppressive, and that impede differentiation, possibly by suppressing cell-cell interactions, or ligand access to cell surface receptors. Hyaluronan chains, which can reach 2 x 10(4) kDa in size, are involved in ovulation, embryogenesis, protection of epithelial layer integrity, wound repair, and regeneration. Smaller polysaccharide fragments are inflammatory, immuno-stimulatory and angiogenic. They can also compete with larger hyaluronan polymers for receptors. Low-molecular-size polymers appear to function as endogenous "danger signals", while even smaller fragments can ameliorate these effects. Tetrasaccharides, for example, are anti-apoptotic and inducers of heat shock proteins. Various fragments trigger different signal transduction pathways. Particular hyaluronan polysaccharides are also generated by malignant cells in order to co-opt normal cellular functions. How the small hyaluronan fragments are generated is unknown, nor is it established whether the enzymes of hyaluronan synthesis and degradation are involved in maintaining proper polymer sizes and concentration. The vast range of activities of hyaluronan polymers is reviewed here, in order to determine if patterns can be detected that would provide insight into their production and regulation.

A Gene Similar to the Human Hyaluronan-mediated Motility Receptor (RHAMM) Gene is Upregulated During Porcine Circovirus Type 2 Infection

Little is known on the cellular events triggered by the Porcine Circovirus type 2 (PCV2) in Porcine Multisystemic Wasting Syndrome (PMWS). The differential display reverse-transcription PCR (DDRT-PCR) was used to identify cellular target molecules in lymph node tissue that were regulated in PMWS. Comparative profile analysis of a pool of lymph node tissues from PMWS and healthy animals showed that some transcripts were up-regulated in PMWS. Bacterial recombinant clones containing up-regulated transcripts were analyzed by reverse dot blot. Clones showing enhanced hybridization when probed with cDNAs from PMWS animals were sequenced and compared to existing databases. Two of the differentially regulated transcripts displayed homology with human genes such as an RNA splicing factor and hyaluronan-mediated motility receptor (RHAMM). Clones encoding theses genes were subsequently used as probes to analyze their expression pattern in PK15 cells persistently infected with PCV2. Northern blot analyzes indicated that these transcripts were up-regulated in these cells as observed in infected lymph node tissue from PMWS cases. A role for the up-regulation of the RHAMM gene is proposed.

The mechanism of molecular redundancy in autoimmune inflammation in the context of CD44 deficiency

Molecular redundancy refers to the ability of genes to back up damaged genes or gene loss. Although this term is widely discussed in many scientific circles, the process is still ill-defined, as shown by reviewing examples from the literature. Exploring the collagen-induced arthritis model in the context of CD44 knockout mice, we suggest a mechanistic explanation for molecular redundancy that depends neither on upregulation of the compensating molecule nor on structural similarity between the original molecule and the replacement molecule. The backup process is dependent, however, on two key properties shared by the two molecules: ligand binding and support of cell trafficking.

Topical high molecular weight hyaluronan reduces radicular pain post laminectomy in a rat model

BACKGROUND CONTEXT

A controversy exists about the mechanism of causation of the post-laminectomy pain syndrome. Some believe that epidural scarring, and attendant spinal nerve and nerve root scarring and tethering to the disc or pedicle at the site of surgery contributes to post-laminectomy pain in such patients. However, clinical outcome studies on this question are inconclusive and the assertion remains controversial. Definitive studies to help resolve the question are needed. Previously our laboratory has reported on a preclinical post-laminectomy model that mimics the postoperative proliferative fibrotic response grossly, as well as by biochemical assessment of the collagen content within the spinal canal. The post-laminectomy fibrotic response was attenuated in that study by application of a topical antifibrotic (high molecular weight hyaluronan gel) or by insertion of an absorbable roofing barrier (0.2-mm-thick Macropore sheet material) over the laminectomy defect before wound closure. The question remains of relevance of the attenuation of the fibrotic response to post-laminectomy chronic pain syndromes.

PURPOSE

The purpose of this study is to evaluate the effect of therapeutic attenuation of proliferative scar within the spinal canal post laminectomy on the pain-related behavioral response in a preclinical rat model.

STUDY DESIGN/SETTING

An established L5-L6 rat laminectomy model with a unilateral L5-6 disc injury was employed to assess postoperative proliferative fibrosis of the L5 spinal nerves using quantitative biochemical hydroxyproline assessment of the collagen content in four experimental groups. These observations were correlated with gross descriptions of spinal nerve scarring or tethering. Associated manifestations of a sensory pain-related response in the L5 spinal nerve receptor area of the hind paws was studied using standard tactile allodynia assessment with the von Frey hair technique. The tactile allodynia findings were supplemented by weekly descriptors of behavioral pain manifestations.

METHODS

Bilateral laminectomies at L5 and L6 and a unilateral right disc injury (L5-6) were performed on 35 male adult Sprague-Dawley rats, weighing 400+ grams (approved by the VA Institutional Animal Care Use Committee). The study consisted of four groups: 1) normal nonoperative control; 2) a sham-operated group; 3) an untreated laminectomy-disc injury group; and 4) a laminectomy-disc injury treatment group in which 0.1 cc topical high molecular weight hyaluronan (HMW HA) gel was layered over the dura and into the laminectomy canal before closure. Before animals were entered into the study, they were checked for the presence of abnormal response to the tactile testing procedure of the L5 sensory receptor area. Animals exhibiting anomalous responses were excluded from the study. Behavioral testing for tactile allodynia was performed at weekly intervals post laminectomy beginning at 3 weeks. Pain-related behavior was characterized at weekly intervals. A behavioral test cage with a wire mesh floor allowed for tactile allodynia testing. Graduated von Frey hairs whose stiffness increased logarithmically from 0.41 to 15 g were used for tactile allodynia tests. The animals were killed 8 weeks postoperatively for analysis. The dissected spinal nerve and nerve root specimens were studied biochemically for hydroxyproline content to estimate total collagen in and around the L5 neural structures. Statistical analyses were performed using analysis of variance and a Fisher comparison t test.

RESULTS

The major observations on the untreated preclinical post-laminectomy rat model previously described by this laboratory were confirmed. All untreated animals developed a tail contracture concave toward the right (disc injury side) consistent with asymmetrical lumbar muscle spasm. Only one animal in the HA gel treatment group had a tail contracture. It was of mild degree and occurred in an animal that demonstrated slightly increased right L5 tactile sensitivity. Gross inspection of the dissected specimens demonstrated spinal nerve scarring and tethering to the disc and pedicle greater on the right than the left in untreated animals, findings that were markedly reduced in the treatment group. Collagen content of the L5 spinal nerve and nerve roots with attached scar were significantly lower in the HA gel treatment group than in the untreated laminectomy group (p=.0014). Pain behavioral testing of the L5 receptor area of the right hind paw in the untreated laminectomy group showed markedly increased sensitivity to tactile allodynia testing compared with the corresponding limb of the control group (p=.0001), to the corresponding limb of the sham group (p=.0001), and compared with the HMW HA gel treatment group (p=.0010). Comparisons of the pain behavioral data between the sham and the post-laminectomy HA gel treatment group and the control animals lacked statistical significance.

CONCLUSION

This study supports the concept of a relationship between perineural fibrosis and radicular neuropathy in the model described, and emphasizes the role of disc injury and spinal nerve retraction in the post-laminectomy fibrotic process. Furthermore, it shows promise for preliminary assessment of interventions with other anti-inflammatory agents, for characterization of the neurochemical profile of the post-laminectomy pain state, and for exploration of newer pharmaceutical agents potentially useful in the prevention or management of the post-laminectomy syndrome. Post-laminectomy scar is but one of many potential causes of the post-laminectomy pain syndrome. Furthermore, a cautionary note must be emphasized as in all studies using preclinical models, conclusions drawn from the studies cannot be extended directly to patients without confirmatory clinical follow-up studies.

Expression and role of the hyaluronan receptor RHAMM in inflammation after bleomycin injury

Lung injury is associated with increased concentrations of hyaluronan (hyaluronic acid, HA). HA modifies cell behavior through interaction with cell-associated receptors such as receptor for HA-mediated motility (RHAMM, CD168). Using a function blocking anti-RHAMM antibody (R36), we investigated the expression and role of RHAMM in the inflammatory response to intratracheal bleomycin in rats. Immunostaining showed increased expression of RHAMM in macrophages 4-7 d after injury. Surface biotin labeling of cells isolated by lavage confirmed increased surface expression of a 70-kD RHAMM after lung injury, and in situ hybridization demonstrated increased RHAMM mRNA in macrophages responding to injury. Time-lapse cinemicrography demonstrated a 5-fold increase in motility of alveolar macrophages from bleomycin-treated animals that was completely blocked by R36 in vitro. Further, HA-stimulated macrophage chemotaxis was also inhibited by R36. Daily administration of R36 to injured animals resulted in a 40% decrease in macrophage accumulation 7 d after injury. Further, H&E staining of tissue sections showed that bleomycin-mediated changes in lung architecture were improved with R36 treatment. Taken together with previous results showing the inhibitory effects of HA-binding peptide on inflammation and fibrosis, we conclude that the interaction of RHAMM with HA is a critical component of the recruitment of inflammatory cells to the lung after injury.

Hyaluronan-binding motif identified by panning a random peptide display library

The glycosaminoglycan hyaluronan (HA) is involved in a variety of functions such as cell migration, adhesion, activation of intracellular signaling, metastasis, inflammation and wound repair. These functions of HA are mediated via HA-binding proteins (HABPs). To derive details of the HA-binding site in HABPs, here, we panned a random peptide display library expressed on the E. coli flagellin protein using HA-coated plates. Using this random peptide display library, 40 positive clones were obtained and the nucleotide sequences were determined. As a result, an Arg-Arg sequence, in addition to the known B-X7-B motif, was found to bind to HA. A binding experiment using the IAsys resonant mirror biosensor verified that a peptide containing an Arg-Arg sequence binds to HA.

Integrative genomics based identification of potential human hepatocarcinogenesis-associated cell cycle regulators: RHAMM as an example

DNA microarray has been widely used to examine gene expression profile of different human tumors. The information generated from microarray analysis usually represents the overall range of cancer-associated abnormality associated with gene regulation. In order to identify key regulatory genes involved in carcinogenesis of human cancer, hypothesis driven data mining of the microarray data plus experimental validation becomes a critical approach in the post-genome era. Here, we present an integrative genomic analysis of published microarray data and homolog gene database. Over 20,000 genes were examined to reveal 16 genes specific to vertebrates, cell cycle G2/M regulated, and overexpressed in human HCC. Using Affymetrix microarray analysis, we found that all 16 genes were up-regulated in human HCC. Among these 16 genes, we experimentally validated the up-regulation of receptor for hyaluronan-mediated motility (RHAMM) in different cell model systems. We first confirmed elevation of RHAMM in the G2/M phase of synchronized HeLa cells. We also found that RHAMM had an elevated level of expression in all the HCC samples we examined and it was induced during the G2/M phase of regenerating mouse hepatocytes after partial hepatectomy. Thus, the expression of RHAMM appears to be tightly regulated during mammalian cell cycle G2/M progression. The ectopic overexpression of RHAMM in 293T cells resulted in the accumulation of cells at G2/M phase. RHAMM-induced mitotic arrest of cells was predominantly in the prophase. Taken together, using an integrated functional genomic approach, we have uncovered a set of genes that may play specific roles in cell cycle progression and in HCC development. To elucidate the function of these genes in cell cycle regulation may shed light on the control mechanism of human HCC in the future.

Receptor for Hyaluronan-Mediated Motility Correlates with Centrosome Abnormalities in Multiple Myeloma and Maintains Mitotic Integrity

Elevated expression of receptor for hyaluronan-mediated motility (RHAMM) within ex vivo diagnostic multiple myeloma plasma cells predicts for aggressive disease and patient survival. Here, we investigate the relationship between RHAMM and centrosomal abnormalities within multiple myeloma patient samples. We report that myeloma patient samples contain pervasive structural and numerical centrosomal abnormalities. Structural, but not numerical, centrosomal abnormalities strongly correlate with elevated RHAMM expression. As others have shown that excess pericentriolar material strongly associates with abnormal mitoses, we modeled centrosomal abnormalities with exogenous RHAMM overexpression. RHAMM overexpression in vitro resulted in centrosomal and mitotic defects. To elucidate a mechanism for RHAMM-mediated spindle defects, we further investigated RHAMM mitotic function. RHAMM mitotic localization mirrors that of targeting protein for Xklp2 (TPX2), and RHAMM interacts with the spindle assembly factors dynein and TPX2. Like TPX2, RHAMM expression is up-regulated during mitosis. Moreover, inhibition of function experiments reveals that RHAMM and TPX2 functions converge to maintain spindle integrity after spindle assembly. We postulate that augmentation of RHAMM expression within human cancers, including myeloma, can directly affect centrosomal structure and spindle integrity and potentially modulate apoptotic and cell cycle progression pathways.

Hyaluronan-CD44 interaction with IQGAP1 promotes Cdc42 and ERK signaling, leading to actin binding, Elk-1/estrogen receptor transcriptional activation, and ovarian cancer progression

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 approximately 190 kDa) is expressed in SK-OV-3.ipl cells and that IQGAP1 interacts directly with Cdc42 in a GTP-dependent 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-alpha (ER alpha), resulting in Elk-1- and estrogen-responsive element-mediated transcriptional up-regulation. Down-regulation of IQGAP1 (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 alpha phosphorylation, and Elk-1/ER alpha-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 alpha) signaling pathway during ovarian cancer progression.

RHAMM, a receptor for hyaluronan-mediated motility, compensates for CD44 in inflamed CD44-knockout mice: a different interpretation of redundancy

We report here that joint inflammation in collagen-induced arthritis is more aggravated in CD44-knockout mice than in WT mice, and we provide evidence for molecular redundancy as a causal factor. Furthermore, we show that under the inflammatory cascade, RHAMM (receptor for hyaluronan-mediated motility), a hyaluronan receptor distinct from CD44, compensates for the loss of CD44 in binding hyaluronic acid, supporting cell migration, up-regulating genes involved with inflammation (as assessed by microarrays containing 13,000 cDNA clones), and exacerbating collagen-induced arthritis. Interestingly, we further found that the compensation for loss of the CD44 gene does not occur because of enhanced expression of the redundant gene (RHAMM), but rather because the loss of CD44 allows increased accumulation of the hyaluronic acid substrate, with which both CD44 and RHAMM engage, thus enabling augmented signaling through RHAMM. This model enlightens several aspects of molecular redundancy, which is widely discussed in many scientific circles, but the processes are still ill defined.

Intracellular hyaluronan in arterial smooth muscle cells: association with microtubules, RHAMM, and the mitotic spindle

Although considered a pericellular matrix component, hyaluronan was recently localized in the cytoplasm and nucleus of proliferating cells, supporting earlier reports that hyaluronan was present in locations such as the nucleus, rough endoplasmic reticulum, and caveolae. This suggests that it can play roles both inside and outside the cell. Hyaluronan metabolism is coupled to mitosis and cell motility, but it is not clear if intracellular hyaluronan associates with cytoskeletal elements or plays a structural role. Here we report the distribution of intracellular hyaluronan, microtubules, and RHAMM in arterial smooth muscle cells in vitro. The general distribution of intracellular hyaluronan more closely resembled microtubule staining rather than actin filaments. Hyaluronan was abundant in the perinuclear microtubule-rich areas and was present in lysosomes, other vesicular structures, and the nucleolus. Partially fragmented fluorescein-hyaluronan was preferentially translocated to the perinuclear area compared with high-molecular-weight hyaluronan. In the mitotic spindle, hyaluronan colocalized with tubulin and with the hyaladherin RHAMM, a cell surface receptor and microtubule-associated protein that interacts with dynein and maintains spindle pole stability. Internalized fluorescein-hyaluronan was also seen at the spindle. Following telophase, an abundance of hyaluronan near the midbody microtubules at the cleavage furrow was also noted. In permeabilized cells, fluorescein-hyaluronan bound to RHAMM-associated microtubules. These findings suggest novel functions for hyaluronan in cellular physiology.

Hyaluronan and morphogenesis

In the past decade, there has been an explosion of interest in hyaluronan, an often misunderstood, biochemically simple, yet functionally complex carbohydrate polymer that is a resident of many extracellular matrices. Previously thought of as a passive, space-filling component of the extracellular matrix, the so-called "goo" concept, hyaluronan has risen to a much higher regard in recent years, even being called "magic glue" in a recent perspective. Hyaluronan is likely to be the common thread in many morphogenetic processes, including condensation events and epithelial-to-mesenchymal transformation. Hyaluronan is comparatively unique as a component of the extracellular matrix as it is solely composed of carbohydrate. In order to truly understand this biopolymer, one must first understand its biosynthesis, then understand its uptake and turnover, then identify its binding proteins and receptors. Major advances have been made in all of these arenas within the past decade. Hyaluronan synthases, hyaluronidases, and the hyaladherins have been molecularly identified and cloned. Furthermore, many have now been inactivated, employing gene targeting strategies, to create mice deficient in the respective gene product function. Collectively, huge strides have been made in our understanding of the diverse biological functions for this fascinating molecule. Hyaluronan appeared in metazoans immediately prior to the arrival of the vertebrates, and may be required for the differentiation, development, and/or function of most cell lineages, structures, and tissues that we associate with vertebrates, such as the neural crest, the skeleton, including the teeth, skin, and hair, and the chambered heart. In this review, we will update the reader on the advances of the past decade and provide insight into those morphogenetic processes through which hyaluronan regulates vertebrate development.

Molecular profiling of malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1, based on large-scale real-time RT-PCR

Background

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a complex range of clinical symptoms. The hallmark of NF1 is the onset of heterogeneous (dermal or plexiform) benign neurofibromas. Plexiform neurofibromas can give rise to malignant peripheral nerve sheath tumors (MPNSTs), and the underlying molecular mechanisms are largely unknown.

Results

To obtain further insight into the molecular pathogenesis of MPNSTs, we used real-time quantitative RT-PCR to quantify the mRNA expression of 489 selected genes in MPNSTs, in comparison with plexiform neurofibromas.

The expression of 28 (5.7%) of the 489 genes was significantly different between MPNSTs and plexiform neurofibromas; 16 genes were upregulated and 12 were downregulated in MPNSTs.

The altered genes were mainly involved in cell proliferation (MKI67, TOP2A, CCNE2), senescence (TERT, TERC), apoptosis (BIRC5/Survivin, TP73) and extracellular matrix remodeling (MMP13, MMP9, TIMP4, ITGB4). More interestingly, other genes were involved in the Ras signaling pathway (RASSF2, HMMR/RHAMM) and the Hedgehog-Gli signaling pathway (DHH, PTCH2). Several of the down-regulated genes were Schwann cell-specific (L1CAM, MPZ, S100B, SOX10, ERBB3) or mast cell-specific (CMA1, TPSB), pointing to a depletion and/or dedifferentiation of Schwann cells and mast cells during malignant transformation of plexiform neurofibromas.

Conclusion

These data suggest that a limited number of signaling pathways, and particularly the Hedgehog-Gli signaling pathway, may be involved in malignant transformation of plexiform neurofibromas. Some of the relevant genes or their products warrant further investigation as potential therapeutic targets in NF1.

Hyaluronan blocks human neutrophil elastase (HNE)-induced airway responses in sheep

Hyaluronan (HA) blocks inhaled porcine pancreatic elastase-induced bronchoconstriction in sheep with airway hypersensitivity to Ascaris suum antigen. Since elastases from other species may display different catalytic properties compared to the human enzyme, we tested the efficacy of HA on human neutrophil elastase (HNE)-induced airway responses. We measured pulmonary resistance in allergic sheep before and after inhalation of HNE alone and after pretreatment with a 150 kD-HA (LKDHA; 3 and 15 mg), or a 300 kD-HA (HKDHA; 6, 7.5, and 15 mg). HKDHA (3 mg) was given either 0.5, 4, or 8 h before HNE challenge; LKDHA (15 mg) and HKDHA (6, 7.5, and 15 mg) were given 8 h before challenge. HNE caused an acute bronchoconstriction which was blocked by 3 mg LKDHA given 0.5 or 4 h before challenge. LKDHA (3 mg) given 8 h before challenge was ineffective, but protection was achieved by increasing the dose to 15 mg. When HKDHA at 6, 7.5, and 15 mg was given 8 h before challenge a dose-dependent inhibition of the HNE-induced airway response was observed. We conclude that HA inhibits HNE-induced airway responses and that within the range of 150-300 kD, dose rather than molecular weight may be the most important determinant of pretreatment time resulting in a protective effect.

Involvement of an unnamed protein, RDA288, in the mechanism through which progesterone mediates its antiapoptotic action in spontaneously immortalized granulosa cells

Progesterone (P4) inhibits apoptosis of rat granulosa cells and spontaneously immortalized granulosa cells (SIGCs), which were derived from rat granulosa cells. Defining the mechanism through which P4 mediates its action has been difficult because these cells do not express the classic nuclear P4 receptor. Previous studies have shown that a P4 receptor antibody, C-262, detects a 60-kDa protein that is involved in regulating P4's antiapoptotic action. Using a C-262 affinity column, this 60-kDa protein was isolated and sequenced by mass spectrometry. This analysis revealed that the C-262-detectable protein is an unnamed protein referred to as RDA288. This protein has several putative hyaluronic acid binding sites. Further hyaluronic acid antagonizes (3)H-P4 binding to SIGCs and mimics P4's action, whereas exogenous hyaluronic acid binding protein attenuates P4's actions. RT-PCR demonstrated that RDA288 mRNA was present in SIGCs, immature rat ovary, lung, and skeletal muscle but was not present in several other organs. Forced expression of RDA288 increased the capacity of SIGCs to bind and respond to P4. An antibody was also developed against RDA288. Using this antibody in a Western blot protocol, RDA288 expression was confirmed in both SIGCs and granulosa cells. An immunohistochemical study detected RDA288 in the cytoplasm and plasma membrane components of granulosa cells of antral follicles. Immunocytochemical studies on living nonpermeabilized SIGCs revealed that RDA288 was present on the extracellular surface of the plasma membrane. Finally, pretreatment with the RDA288 antibody blocked P4's antiapoptotic actions. Taken together, these data suggest that RDA288 plays a significant role in mediating P4's antiapoptotic action in granulosa cells.

Butyric and retinoic mixed ester of hyaluronan. A novel differentiating glycoconjugate affording a high throughput of cardiogenesis in embryonic stem cells

Embryonic stem (ES) cells can differentiate into specialized cells, including cardiac myocytes, but the efficiency is typically low and the process is incompletely understood. Achieving a high throughput of cardiogenesis from pluripotent cells is therefore a major requirement for future approaches in cardiac cell therapy. Here, we developed a novel ester of hyaluronan linked to both butyric and retinoic acid (HBR), coaxing pluripotent ES cells into a cardiogenic decision. In mouse ES cells, HBR remarkably increased the expression of GATA-4 and Nkx-2.5, acting as cardiac lineage-promoting genes in different animal species, including humans. HBR also enhanced prodynorphin gene expression and the synthesis and secretion of dynorphin B, an endorphin playing a major role in ES cell cardiogenesis. These effects occurred at the transcriptional level. HBR also primed the expression of cardiac-specific transcripts and highly enhanced the yield of spontaneously beating ES-derived cardiomyocytes. These results demonstrate the potential for chemically modifying the gene program of cardiac differentiation in ES cells without the aid of gene transfer technologies and may pave the way for novel approaches in tissue engineering and myocardial regeneration.

RHAMM expression and isoform balance predict aggressive disease and poor survival in multiple myeloma

Multiple myeloma (MM) plasma cells (PCs) express receptor for hyaluronan-mediated motility (RHAMM), a hyaluronan-binding, cytoskeleton and centrosome protein. The most abundant RHAMM isoforms in MM are full-length RHAMM (RHAMMFL) and the splice variant RHAMM-exon4. We separately examined the significance of RHAMM expression, and isoform balance, in 2 groups of MM patients. In oligonucleotide microarray experiments (n=210, Arkansas), increasing RHAMM mRNA expression in MM PCs is strongly associated with osteolytic bone lesions (P <.001), and event-free (P =.05) and overall (P =.04) survival. Semiquantitative determination of RHAMM isoform expression (Alberta, Canada) used capillary electrophoretic detection and measurement of RHAMM-exon4/RHAMMFL reverse-transcriptase-polymerase chain reaction (RT-PCR) products. RHAMM isoforms are rarely expressed concurrently in single MM PCs; the pattern of isoform expression, at the single-cell level, is approximated in larger numbers of cells by the RHAMM-exon4/RHAMMFL ratio. Absolute RHAMM expression and the RHAMM-exon4/RHAMMFL ratio are only partially correlated in MM PCs; in cell lines, absolute RHAMM expression is elevated in mitosis, while RHAMM ratios remain stable. Temporal examination of MM patients' peripheral blood reveals that the RHAMM-exon4/RHAMMFL ratio increases with disease burden. The RHAMM-exon4/RHAMMFL ratio in diagnostic bone marrow samples (n=101, Alberta) is an independent prognostic factor. Thus, expression and splicing of RHAMM are important molecular determinants of disease severity in MM.

Elevated hyaluronan production induces mesenchymal and transformed properties in epithelial cells

During carcinoma progression, tumor cells often undergo changes similar (but not identical) to epithelialmesenchymal transitions in embryonic development. In this study, we demonstrate that experimental stimulation of hyaluronan synthesis in normal epithelial cells is sufficient to induce mesenchymal and transformed characteristics. Using recombinant adenoviral expression of hyaluronan synthase-2, we show that increased hyaluronan production promotes anchorage-independent growth and invasiveness, induces gelatinase production, and stimulates phosphoinositide 3-kinase/Akt pathway activity in phenotypically normal Madin-Darby canine kidney and MCF-10A human mammary epithelial cells. Cells infected with hyaluronan synthase-2 adenovirus also acquired mesenchymal characteristics, including up-regulation of vimentin, dispersion of cytokeratin, and loss of organized adhesion proteins at intercellular boundaries. Furthermore, we show that the transforming effects of two well described agents, hepatocyte growth factor (HGF) and beta-catenin, are dependent on hyaluronan-cell interactions. Perturbation of endogenous hyaluronan polymer interactions by treatment with hyaluronan oligomers is shown here to reverse the transforming effects of HGF and beta-catenin in Madin-Darby canine kidney and MCF-10A human mammary epithelial cells. Also, HGF and beta-catenin induced assembly of hyaluronan-dependent pericellular matrices similar to those surrounding mesenchymal cells. Thus, increased expression of hyaluronan is sufficient to induce epithelial-mesenchymal transition and acquisition of transformed properties in phenotypically normal epithelial cells.

Genetic deletion of receptor for hyaluronan-mediated motility (Rhamm) attenuates the formation of aggressive fibromatosis (desmoid tumor)

Aggressive fibromatosis (desmoid tumor) is a locally invasive soft tissue neoplasm associated with mutations resulting in beta-catenin-mediated transcriptional activation. This tumor is composed of cells with histological and molecular characteristics common to proliferating mesenchymal cells of dermal wounds. Using immunohistochemistry and RT-PCR, we show that Rhamm, a protein with an important role in wound healing and neoplastic progression, is also expressed at high levels in aggressive fibromatosis. A mouse harboring a targeted deletion in Rhamm was generated, resulting in viable Rhamm-/- animals. Rhamm-/- mice were crossed with Apc/Apc1638N mice, which harbor a targeted mutation in the Apc gene predisposing animals to gastrointestinal and aggressive fibromatosis tumors. Rhamm deficiency significantly decreased the number of aggressive fibromatosis tumors formed, but did not alter the number of gastrointestinal polyps. Cell culture studies show that Rhamm regulates cell proliferation in both fibroblasts and fibromatosis cells under conditions of low density, but not high density. These results suggest that Rhamm regulates proliferation of cells with sparse cell-cell contacts, such as occurs in aggressive fibromatosis; provides the first genetic evidence implicating Rhamm in tumor pathology; and suggest Rhamm blockade as a potential therapeutic target for this otherwise difficult-to-treat neoplasm.

Developmental regulation of hyaluronan-binding protein (RHAMM/IHABP) expression in early bovine embryos

Hyaluronan or hyaluronic acid (HA) is a normal component of mammalian follicular, oviduct, and uterine fluids. Granulosa and expanding cumulus cells secrete large amounts of HA, and when HA is added in maturation and culture media, it improves the developmental potential of oocytes and embryos. HA regulates gene expression, signaling, proliferation, motility, adhesion, and morphogenesis. Many of these biological activities of HA are mediated through binding to the receptor for HA-mediated motility/intracellular HA-binding protein (RHAMM/IHABP). We evaluated the presence and dynamics of RHAMM/IHABP mRNA and protein expression in different stages of in vitro-produced bovine embryos using quantitative reverse transcriptase-real time-polymerase chain reaction and immunohistochemistry. We also analyzed the effects of different culture systems on the relative abundance of RHAMM/IHABP transcripts. RHAMM/IHABP mRNA levels decreased from the 2-cell to the 16-cell stage, increased again at the morula stage, and reached their highest level at the expanded blastocyst stage. RHAMM/IHABP mRNA abundance was significantly (P < 0.05) lower in embryos recovered in serum-containing medium than in embryos from serum-free media. Immunohistochemistry revealed the presence of RHAMM/IHABP first in 8-cell stages. Whereas RHAMM staining in 8-cell and morula stages was intense, it was weaker in blastocysts. Embryonic secretion of HA increased from the 2-cell stage until the 8-cell stage and then decreased in 16-cell embryos. After this, HA secretion increased in expanded and hatched blastocyst stages. These data suggest that the positive effects of HA on in vitro-produced bovine embryos may be mediated at least in part by RHAMM/IHABP.

Expression of hyaluronan synthase 2 or hyaluronidase 1 differentially affect the growth rate of transplantable colon carcinoma cell tumors

Advanced colorectal cancers are often associated with elevated amounts of hyaluronan. To investigate the importance of hyaluronan in colon carcinoma tumor progression, we have expressed by stable transfection hyaluronan synthase 2 (Has2) and hyaluronidase 1 (Hyal1) in the rat colon carcinoma cell line, PROb. We found that hyaluronan overproduction led to a higher growth rate of tumor cells in vitro, and to a faster development of transplantable tumors in syngeneic rats, compared to the mock-transfectants. Has2 transfected PROb cells gave rise to tumors that were significantly less vascularized, but had a significantly larger viable tumor fraction compared to tumors generated from mock-transfectants. In contrast, Hyal1 overexpression suppressed the growth rate of tumor cells both in vitro and in vivo. Moreover, tumors derived from Hyal1-transfected cells had a significantly larger necrotic area than tumors derived from mock- and Has2-transfectants. Our study demonstrates that Has2 overproduction promotes tumorigenicity, whereas Hyal1 overexpression suppresses tumorigenicity in an experimental model for colon carcinoma.

Angiogenic oligosaccharides of hyaluronan induce multiple signaling pathways affecting vascular endothelial cell mitogenic and wound healing responses

Hyaluronan (HA) is a large nonsulfated glycosaminoglycan and an important regulator of angiogenesis, in particular, the growth and migration of vascular endothelial cells. We have identified some of the key intermediates responsible for induction of mitogenesis and wound recovery. Treatment of bovine aortic endothelial cells with oligosaccharides of hyaluronan (o-HA) resulted in rapid tyrosine phosphorylation and plasma membrane translocation of phospholipase Cgamma1 (PLCgamma1). Cytoplasmic loading with inhibitory antibodies to PLCgamma1, Gbeta, and Galpha(i/o/t/z) inhibited activation of extracellular-regulated kinase 1/2 (ERK1/2). Treatment with the Galpha(i/o) inhibitor, pertussis toxin, reduced o-HA-induced PLCgamma1 tyrosine phosphorylation, protein kinase C (PKC) alpha and beta1/2 membrane translocation, ERK1/2 activation, mitogenesis, and wound recovery, suggesting a mechanism for o-HA-induced angiogenesis through G-proteins, PLCgamma1, and PKC. In particular, we demonstrated a possible role for PKCalpha in mitogenesis and PKCbeta1/2 in wound recovery. Using antisense oligonucleotides and the Ras farnesylation inhibitor FTI-277, we showed that o-HA-induced bovine aortic endothelial cell proliferation, wound recovery, and ERK1/2 activation were also partially dependent on Ras activation, and that o-HA-stimulated tyrosine phosphorylation of the adapter protein Shc, as well as its association with Sos1. Binding of Src to Shc was required for its activation and for Ras-dependent activation of ERK1/2, cell proliferation, and wound recovery. Neither Src nor Ras activation was inhibited by pertussis toxin, suggesting that their activation was independent of heterotrimeric G-proteins. However, the specific Src kinase inhibitor PP2 inhibited Gbeta subunit co-precipitation with PLCgamma1, suggesting a possible role for Src in activation of PLCgamma1 and interaction between two distinct o-HA-induced signaling pathways.

CD44 signaling through focal adhesion kinase and its anti-apoptotic effect

Adhesion molecules can initiate intracellular signaling. Engagement of CD44 either by its natural ligand hyaluronan or a specific antibody on a cell line induced tyrosine phosphorylation and activation of focal adhesion kinase (FAK), which then associated with phosphatidylinositol 3-kinase (PI3K) and activated mitogen-activated protein kinase at its downstream. However, the introduction of dominant negative Rho into the cells inhibited the CD44-stimulated FAK phosphorylation. Cells expressing CD44 were significantly resistant to etoposide-induced apoptosis. This anti-apoptotic effect was cancelled by the inhibition of either Rho, FAK or PI3K. These results may indicate a signaling pathway from CD44 to mediate the resistance against drug-induced apoptosis in cancer cells.

Changed lamellipodial extension, adhesion plaques and migration in epidermal keratinocytes containing constitutively expressed sense and antisense hyaluronan synthase 2 (Has2) genes

Hyaluronan is a major component of the epidermal extracellular matrix, is actively synthesized by keratinocytes and shows fast matrix turnover in the stratified epithelium. We probed the importance of hyaluronan synthesis in keratinocytes by establishing cell lines carrying the exogenous hyaluronan synthase 2 (Has2) gene in sense and antisense orientations to increase and decrease their hyaluronan synthesis, respectively. Compared with cell lines transfected with the vector only, most clones containing the Has2 sense gene migrated faster in an in vitro wounding assay, whereas Has2 antisense cells migrated more slowly. Has2 antisense clones showed delayed entry into the S phase of cell cycle following plating, smaller lamellipodia and less spreading on the substratum. The decrease of hyaluronan on the undersurface of Has2 antisense cells was associated with an increased area of adhesion plaques containing vinculin. Exogenous hyaluronan added to the keratinocyte cultures had a minor stimulatory effect on migration after wounding but did not restore the reduced migratory ability of Has2 antisense cells. Hyaluronan decasaccharides that displace receptor bound hyaluronan in keratinocytes, and Streptomyces hyaluronidase sufficient to remove most cell surface hyaluronan had little effect on cell migration. The results suggest that the dynamic synthesis of hyaluronan directed by Has2, rather than the abundance of pericellular hyaluronan, controls keratinocyte migration, a cell function vital for the repair of squamous epithelia following wounding.

Src-/- fibroblasts are defective in their ability to disassemble focal adhesions in response to phorbol ester/hyaluronan treatment

Exogenous hyaluronan promotes a rapid recruitment of Src to lamellae of mutant active H-ras transformed fibroblasts and an Src- and RHAMM (CD168)-dependent increase in random motility. These responses are accompanied by a loss of vinculin-positive lamellae focal adhesions. Nontransformed immortalized wild-type fibroblasts (WT) do not increase random motility in response to hyaluronan alone, but do increase motility in response to a combination of PMA treatment followed by hyaluronan. PMA treatment alone increases the number of lamellae/cell, percentage of cells with lamellae and number of focal adhesions/lamellae. Subsequent addition of hyaluronan does not affect the number of lamellae/cell but reduces both the number of focal adhesion/lamellae and the percentage of cells forming focal adhesion-positive lamellae. These effects are prevented by blocking RHAMM antibodies and mimicked by agonist RHAMM antibodies. Src-/- fibroblasts exhibit a limited response to PMA but do not increase motility or disassemble focal adhesions in response to a subsequent addition of HA. Rescue of Src-/- fibroblasts with either SrcA or c-Src restores response to close to WT levels. These results suggest that Src activity is uniquely required for both PMA and PMA-induced hyaluronan regulation of random motility and focal adhesion turnover.

N-terminal N-myristoylation of proteins: prediction of substrate proteins from amino acid sequence

Myristoylation by the myristoyl-CoA:protein N-myristoyltransferase (NMT) is an important lipid anchor modification of eukaryotic and viral proteins. Automated prediction of N-terminal N-myristoylation from the substrate protein sequence alone is necessary for large-scale sequence annotation projects but it requires a low rate of false positive hits in addition to a sufficient sensitivity. Our previous analysis of substrate protein sequence variability, NMT sequences and 3D structures has revealed motif properties in addition to the known PROSITE motif that are utilized in a new predictor described here. The composite prediction function (with separate ad hoc parameterization (a) for queries from non-fungal eukaryotes and their viruses and (b) for sequences from fungal species) consists of terms evaluating amino acid type preferences at sequences positions close to the N terminus as well as terms penalizing deviations from the physical property pattern of amino acid side-chains encoded in multi-residue correlation within the motif sequence. The algorithm has been validated with a self-consistency and two jack-knife tests for the learning set as well as with kinetic data for model substrates. The sensitivity in recognizing documented NMT substrates is above 95 % for both taxon-specific versions. The corresponding rate of false positive prediction (for sequences with an N-terminal glycine residue) is close to 0.5 %; thus, the technique is applicable for large-scale automated sequence database annotation. The predictor is available as public WWW-server with the URL http://mendel.imp.univie.ac.at/myristate/. Additionally, we propose a version of the predictor that identifies a number of proteolytic protein processing sites at internal glycine residues and that evaluates possible N-terminal myristoylation of the protein fragments.A scan of public protein databases revealed new potential NMT targets for which the myristoyl modification may be of critical importance for biological function. Among others, the list includes kinases, phosphatases, proteasomal regulatory subunit 4, kinase interacting proteins KIP1/KIP2, protozoan flagellar proteins, homologues of mitochondrial translocase TOM40, of the neuronal calcium sensor NCS-1 and of the cytochrome c-type heme lyase CCHL. Analyses of complete eukaryote genomes indicate that about 0.5 % of all encoded proteins are apparent NMT substrates except for a higher fraction in Arabidopsis thaliana ( approximately 0.8 %).

Hyaluronan promotes the malignant phenotype

Hyaluronan is a high-molecular-weight, negatively charged polysaccharide with unusual physical and interactive properties. Hyaluronan is localized in the extracellular matrix, at the cell surface, and inside cells. Its tissue distribution is ubiquitous, but it is particularly concentrated in pericellular matrices surrounding proliferating and migrating cells. Hyaluronan contributes to cell behavior in at least three ways. Its unique physical properties influence the biomechanical properties of extracellular and pericellular matrices; it is a template for assembly of other pericellular macromolecules; and it interacts directly with cell surface receptors that transduce intracellular signals. Experimental studies in animal models have documented a crucial role for hyaluronan in tumor growth and metastasis. Cellular manipulations have shown that hyaluronan promotes anchorage-independent growth and invasiveness, hallmarks of the malignant phenotype.

Hyaluronic acid blocks porcine pancreatic elastase (PPE)-induced bronchoconstriction in sheep

We previously showed that inhaled porcine pancreatic elastase (PPE) causes bronchoconstriction in sheep via a bradykinin-mediated mechanism. Hyaluronic acid (HA), in vitro, binds and inactivates airway tissue kallikrein (TK), the enzyme responsible for kinin generation. Therefore, we hypothesized that in vivo, HA should prevent PPE-induced bronchoconstriction by binding and inactivating TK. To test this, we measured pulmonary resistance (RL) in allergic sheep before and after inhalation of PPE alone (500 microg) and after pretreatment with either inhaled HA at 70 kD, designated low molecular weight (LMW)-HA or 200 kD, designated high molecular weight (HMW)-HA at different concentrations. Inhaled PPE increased RL 147 +/- 8% over baseline values and this effect was associated with a 111 +/- 28% increase in bronchoalveolar lavage fluid (BALF) TK activity. HA blocked the PPE-induced bronchoconstriction and the increase in BALF TK activity in a dose- dependent and molecular weight-dependent fashion. HA alone had no effect on RL. Instillation of PPE in the lung increased kinin concentrations in BALF, a result consistent with the PPE-induced increase in BALF TK activity. Our findings show that HA blocks PPE-induced bronchoconstriction in a dose-dependent and molecular weight-dependent fashion by a mechanism that may, in part, be related to inhibition of TK activity and the formation of kinins.

Peptides that mimic glycosaminoglycans: high-affinity ligands for a hyaluronan binding domain

BACKGROUND

Hyaluronan (HA) is a non-sulfated glycosaminoglycan (GAG) that promotes motility, adhesion, and proliferation in mammalian cells, as mediated by cell-surface HA receptors. We sought to identify non-carbohydrate ligands that would bind to and activate cell-surface HA receptors. Such analogs could have important therapeutic uses in the treatment of cancer, wound healing, and arthritis, since such ligands would be resistant to degradation by hyaluronidase (HAse).

RESULTS

Peptide ligands that bind specifically to the recombinant HA binding domain (BD) of the receptor for hyaluronan-mediated motility (RHAMM) were obtained by screening two peptide libraries: (i) random 8-mers and (ii) biased 8-mers with alternating acidic side chains, i.e. XZXZXZXZ (X=all-L-amino acids except Cys, Lys, or Arg; Z=D-Asp, L-Asp, D-Glu, or L-Glu). Selectivity of the peptide ligands for the HABD was established by (i) detection of binding of biotin- or fluorescein-labeled peptides to immobilized proteins and (ii) fluorescence polarization of FITC-labeled peptides with the HABD in solution. HA competitively displaced binding of peptides to the HABD, while other GAGs were less effective competitors. The stereochemistry of four biased octapeptides was established by synthesis of the 16 stereoisomers of each peptide. Binding assays demonstrated a strong preference for alternating D and L configurations for the acidic residues, consistent with the calculated orientation of glucuronic acid moieties of HA.

CONCLUSIONS

Two classes of HAse-resistant peptide mimetics of HA were identified with high affinity, HA-compatible binding to the RHAMM HABD. This demonstrated that non-HA ligands specific to a given HA binding protein could be engineered, permitting receptor-specific targeting.

Identification of sequence, protein isoforms, and distribution of the hyaluronan-binding protein RHAMM in adult and developing rat brain

The protein RHAMM (for "receptor for hyaluronan-mediated motility"; CD168) is a member of the hyaladherin family of hyaluronan-binding proteins. RHAMM has a role in cell signaling, migration, and adhesion via interactions with hyaluronan, microtubules, actin, calmodulin, and components of the extracellular regulated kinase (erk) signaling pathway. Based on previous findings of potentially similar roles in neural cells in culture, we investigated the molecular characteristics, protein expression profile, and distribution of RHAMM in rat brain. Reverse transcriptase-polymerase chain reaction (RT-PCR) using RNA isolated from adult rat brain yielded a single RHAMM sequence of 2.1 kilobases encoding a protein of 82.4 kDa. RHAMM is subject to alternate splicing in other systems, but no RT-PCR evidence was found for splice variants in brain, although our analysis does not rule out this possibility. The amino acid sequence displayed homology with human and murine RHAMM (74% and 80%, respectively) but contained only one copy of a 21-amino-acid sequence that is repeated five times in the murine homologue. By using anti-RHAMM antibodies, several RHAMM isoforms were identified in brain. Immunohistochemically, RHAMM was found in the vast majority of neurons and in many oligodendrocytes throughout brain, with heterogeneous levels among cell populations, and was confined to the somata and initial processes of these cells. RHAMM was detected in neurons of cerebral cortex and most subcortical and brainstem structures at postnatal day 1 and exhibited an adult distribution pattern by postnatal day 5. High levels were detected in oligodendrocytes by postnatal day 10. The widespread expression of RHAMM in adult and developing brain implies a role for this protein and its ligand hyaluronan in key events of cell signaling and cytoskeletal regulation in the CNS.

Active erk regulates microtubule stability in H-ras-transformed cells

Increasing evidence suggests that activated erk regulates cell functions, at least in part, by mechanisms that do not require gene transcription. Here we show that the map kinase, erk, decorates microtubules (MTs) and mitotic spindles in both parental and mutant active ras-transfected 10T1/2 fibroblasts and MCF10A breast epithelial cells. Approximately 20% of total cellular erk decorated MTs in both cell lines. A greater proportion of activated erk was associated with MTs in the presence of mutant active H-ras than in parental cells. Activation of erk by the ras pathway coincided with a decrease in the stability of MT, as detected by a stability marker. The MKK1 inhibitor, PD98059 and transfection of a dominant negative MKK1 blocked ras-induced instability of MTs but did not modify the association of erk with MTs or affect MT stability of the parental cells. These results indicate that the subset of active erk kinase that associates with MTs contributes to their instability in the presence of a mutant active ras. The MT-associated subset of active erk likely contributes to the enhanced invasive and proliferative abilities of cells containing mutant active H-ras.

Subcellular distribution, calmodulin interaction, and mitochondrial association of the hyaluronan-binding protein RHAMM in rat brain

The CNS contains high levels of the glycosaminoglycan hyaluronan, and neural cells express a variety of proteins that are members of the hyaladherin family of hyaluronan-binding proteins. We have previously shown that the hyaladherin RHAMM (receptor for hyaluronan-mediated motility; CD168) is expressed by neural cells in culture; plays a role in astrocyte motility, neurite migration, and axonal growth; and is widely distributed in neurons and oligodendrocytes of developing and adult rat CNS. Here we demonstrate differential localization of various forms of RHAMM in subcellular fractions of adult rat brain. Western blotting indicated the presence of 66, 75, and 85-90 kDa molecular weight RHAMM forms in whole-brain homogenates. Subfractionation revealed enrichment of the 66 and 85-90 kDa forms in soluble fractions, whereas the 75 kDa form was enriched in mitochondrial fractions. This latter form was retained in osmotically shocked mitochondria, but was liberated by alkali carbonate, suggesting a nonintrinsic mitochondrial membrane association. By double immunohistochemical labeling for RHAMM and the mitochondrial marker cytochrome oxidase, RHAMM was localized to isolated mitochondria in vitro and to neuronal mitochondria in vivo. Hyaluronan-sepharose chromatography and cetylpiridinium chloride precipitation confirmed the hyaluronan-binding capacity of RHAMM forms. By calmodulin-affinity chromatography, endogenously expressed brain RHAMM was demonstrated to bind calmodulin in a Ca2+-dependent manner. These results, together with reports of RHAMM association with actin and microtubules in other systems, suggest a role of RHAMM in calmodulin-mediated cell signaling to cytoskeletal elements and/or mitochondria in the CNS and invoke novel functions of its interactions with hyaluronan.

Sequence, protein expression and extracellular-regulated kinase association of the hyaladherin RHAMM (receptor for hyaluronan mediated motility) in PC12 cells

Differentiation of PC12 cells by nerve growth factor (NGF) or fibroblast growth factor-2 (FGF2) is dependent on signaling mediated by extracellular regulated kinase (ERK). We investigated the involvement of receptor for hyaluronan mediated motility (RHAMM) in this signaling pathway. A single RHAMM 3.2 kb transcript was detected in PC12 RNA. Reverse transcriptase-polymerase chain reaction generated a 2141 bp cDNA that had identical sequence to rat brain RHAMM and showed no evidence of alternate splicing. Several RHAMM species were identified by Western blotting. Immunohistochemistry showed RHAMM localization to the cytoskeleton, neurites and growth cones. Following stimulation of PC12 cells with NGF or FGF2 RHAMM was co-immunoprecipitated by phosphorylation-specific anti-ERK antibodies, indicating a role for RHAMM in ERK signaling in PC12 cells.

Hyaluronic acid in cultured ovine tracheal cells and its effect on ciliary beat frequency in vitro

Hyaluronic acid (hyaluronan, or HA) is secreted by submucosal glands, but its function in airway secretions other than influencing the rheology of mucus is not fully understood. HA is known to modulate cell behavior and to enhance sperm motility. Because sperm tails and cilia have the same microtubular structure, we studied the effect of HA on ciliary beat frequency (CBF) in vitro. CBF of cultured ovine airway epithelial cells was measured continuously by digital video microscopy. After removal of endogenous HA by hyaluronidase, cells were exposed to 50 to 100 microg/mL of HA at different times in culture. No change in CBF in response to HA was seen in cells cultured less than 7 days. After 7 days, however, 6 of 10 measured cells (from three different sheep) showed a transient CBF increase from a baseline of 6.4 +/- 0.3 Hz (mean +/- SE) to 7.4 +/- 0.4 Hz or 16% above baseline (p < 0.05). At these time points (but not before), cytochemical staining was positive for endogenous HA using a biotinylated HA-binding protein. These data suggest that HA can increase CBF of tracheal epithelial cells only late in culture when HA is able to bind to an unspecified cell surface structure. Because this binding has a physiological effect, we hypothesize that it is an HA-binding receptor, that is either transiently expressed late in culture or initially destroyed by the protease treatment for cell dispersion.

Hyaluronate receptors mediating glioma cell migration and proliferation

The extracellular matrix (ECM) of the central nervous system (CNS) is enriched in hyaluronate (HA). Ubiquitous receptors for HA are CD44 and the Receptor for HA-Mediated Motility known as RHAMM. In the present study, we have investigated the potential role of CD44 and RHAMM in the migration and proliferation of human astrocytoma cells. HA-receptor expression in brain tumor cell lines and surgical specimens was determined by immunocytochemistry and western blot analyses. The ability of RHAMM to bind ligand was determined through cetylpyridinium chloride (CPC) precipitations of brain tumor lysates in HA-binding assays. The effects of HA, CD44 blocking antibodies, and RHAMM soluble peptide on astrocytoma cell growth and migration was determined using MTT and migration assays. Our results show that the expression of the HA-receptors, CD44, and RHAMM, is virtually ubiquitous amongst glioma cell lines, and glioma tumor specimens. There was a gradient of expression amongst gliomas with high grade gliomas expressing more RHAMM and CD44 than did lower grade lesions or did normal human astrocytes or non-neoplastic specimens of human brain. Specific RHAMM variants of 85- and 58-kDa size were shown to bind avidly to HA following CPC precipitations. RHAMM soluble peptide inhibited glioma cell line proliferation in a dose-dependent fashion. Finally, while anti-CD44 antibodies did not inhibit the migration of human glioma cells, soluble peptides directed at the HA-binding domain of RHAMM inhibited glioma migration both on and off an HA-based ECM. These data support the notion that HA-receptors contribute to brain tumor adhesion, proliferation, and migration, biological features which must be better understood before more effective treatment strategies for these tumors can be found.

Fibroblasts require protein kinase C activation to respond to hyaluronan with increased locomotion

Hyaluronan (HA) stimulates the motility of some but not all cell types. Here, we show that HA-promoted random motility of ras-transformed 10T1/2 (C3) fibroblasts requires activation of protein kinase C and is associated with rapid uptake of HA in a CD44 and RHAMM-dependent manner. The addition of HA to parental 10T1/2 fibroblasts (parental cells) does not stimulate random motility, but these cells can be 'primed' to respond to HA by treatment with the phorbol ester, PMA, for 4-6 h. This effect of PMA requires protein synthesis, PKC activity and is associated with enhanced uptake of HA. These results suggest that the ability of cells to respond to HA is regulated by a protein kinase C-dependent process that may promote uptake of HA.

Identification of a nuclear variant of MGEA5, a cytoplasmic hyaluronidase and a beta-N-acetylglucosaminidase

MGEA5 was originally identified to be a novel human hyaluronidase, which is immunogenic in meningioma patients. Recently an N-acetylglucosaminidase was reported with identical sequence. Here, we define the origin of a splice variant by determining the genomic organization of the mgea5 gene. We find the splice variant missing a putative acetyltransferase domain of MGEA5. As for evolutionary analysis, we show that the MGEA5 is highly conserved in higher eukaryotes. As for expression analysis, we find both mRNA variants ubiquitously expressed in various human tissues and throughout mouse development. We generated polyclonal antibodies against MGEA5s/5 and identified proteins of 75 and 130 kDa, indicating posttranslational modifications of the larger protein. Cell fractionation revealed the cytoplasmic/cytoskeletal localization of the 130-kDa protein and the nuclear localization of the 75-kDa protein. We propose a model in which MGEA5 functions both as a hyaluronidase and an N-acetylglucosaminidase.

Stromal and epithelial expression of tumor markers hyaluronic acid and HYAL1 hyaluronidase in prostate cancer

Hyaluronic acid (HA), a glycosaminoglycan, regulates cell adhesion and migration. Hyaluronidase (HAase), an endoglycosidase, degrades HA into small angiogenic fragments. Using an enzyme-linked immunosorbent assay-like assay, we found increased HA levels (3-8-fold) in prostate cancer (CaP) tissues when compared with normal (NAP) and benign (BPH) tissues. The majority ( approximately 75-80%) of HA in prostate tissues was found to exist in the free form. Primary CaP fibroblast and epithelial cells secreted 3-8-fold more HA than respective NAP and BPH cultures. Only CaP epithelial cells and established CaP lines secreted HAase and the secretion increased with tumor grade and metastasis. The pH activity profile and optimum (4.2; range 4.0-4.3) of CaP HAase was identical to the HYAL1-type HAase present in human serum and urine. Full-length HYAL1 transcript and splice variants were detected in CaP cells by reverse transcriptase-polymerase chain reaction, cloning, and sequencing. Immunoblotting confirmed secretion of a approximately 60-kDa HYAL1-related protein by CaP cells. Immunohistochemistry showed minimal HA and HYAL1 staining in NAP and BPH tissues. However, a stromal and epithelial pattern of HA and HYAL1 expression was observed in CaP tissues. While high HA staining was observed in tumor-associated stroma, HYAL1 staining in tumor cells increased with tumor grade and metastasis. The gel-filtration column profiles of HA species in NAP, BPH, and CaP tissues were different. While the higher molecular mass and intermediate size HA was found in all tissues, the HA fragments were found only in CaP tissues. In particular, the high-grade CaP tissues, which showed both elevated HA and HYAL1 levels, contained angiogenic HA fragments. The stromal-epithelial HA and HYAL1 expression may promote angiogenesis in CaP and may serve as prognostic markers for CaP.

Abnormalities of bone marrow mesenchymal cells in multiple myeloma patients

BACKGROUND

The importance of the bone marrow microenvironment in multiple myeloma is receiving increasing attention. Recent studies have suggested the importance of cytokine production and cell-cell contact by bone marrow stromal cells in the survival of myeloma cells.

METHODS

In the current study, the authors examined bone marrow mesenchymal progenitor cell (MPC) cultures derived from eight multiple myeloma patients (mean age, 58 years) and nine normal donors (mean age, 61 years), with emphasis on cell surface antigens, cytokine, and growth factor expression.

RESULTS

The authors have found, based on analysis of cellular receptors, growth factors, and cytokine expression, that myeloma MPCs are phenotypically and functionally distinguishable from normal donor MPCs. Immunofluorescence analysis of MPC monolayers shows that myeloma MPC cultures expressed reduced cell surface vascular cell adhesion molecule-1 and fibronectin, in contrast with the strong expression found on normal donor MPCs. Furthermore, a subset of myeloma MPCs strongly express intracellular receptor for hyaluronan-mediated motility, whereas normal MPCs do not. Cytokine expression in bone marrow MPC cultures was examined by reverse transcription-polymerase chain reaction and enzyme linked immunosorbent assay. Bone marrow MPCs constitutively express interleukin (IL)-1beta, IL-6, granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage (GM)-CSF, stem cell factor (SCF), and tumor necrosis factor (TNF)-alpha. In comparison to normal MPCs, multiple myeloma MPCs express increased basal levels of IL-1beta and TNF-alpha. In vitro exposure of MPC cultures to dexamethasone resulted in the down-regulation of IL-6, G-CSF, and GM-CSF in both normal and myeloma MPC cultures. However, dexamethasone treatment significantly increased expression of SCF-1 in myeloma MPCs.

CONCLUSIONS

In myeloma, bone marrow stromal cells provide paracrine factors, through cytokine production and cell-cell contact, which play a role in plasma cell growth and survival. The authors' data indicate differences in bone marrow MPCs, which may be biologically relevant to the growth and survival of myeloma plasma cells.

Hyaluronan in morphogenesis

Hyaluronan is a very large polysaccharide that is found in extracellular matrices, at the cell surface and inside cells. This review focuses on the functions of hyaluronan directly associated with the cell surface, where it is commonly present as the essential core of a highly hydrated pericellular matrix that contains several other components (hyaladherins) bound to hyaluronan. Three major molecular characteristics of hyaluronan contribute to its physiological functions: its unique hydrodynamic properties, its interactions with structural extracellular hyaladherins, and its instructive effects on cell signaling and behavior. Recent studies of hyaluronan-deficient mouse embryos illustrate the importance of each of these classes of function of hyaluronan. It is postulated that the morphogenetic effects of hyaluronan are due to its ability to act as a template for assembly of a multi-component, pericellular matrix as well as to its physical properties. This matrix would provide a hydrated environment in which cells are separated from structural barriers to morphogenetic changes and receive signals from hyaluronan itself and from associated factors.

Hyaluronan enhances contraction of collagen by smooth muscle cells and adventitial fibroblasts: Role of CD44 and implications for constrictive remodeling

Remodeling contributes to restenosis when cells shrink the artery wall at sites of injury. This may be analogous to wound healing, where tissue remodeling achieves wound contraction. Hyaluronan (HA) is prominent in wound matrix and inhibits fetal scarring. HA is also produced in the artery wall after angioplasty, where it may inhibit constrictive remodeling. This hypothesis was tested in vitro using a model of matrix contraction. Primate aortic smooth muscle cells and adventitial fibroblasts were seeded into collagen I gels containing increasing amounts of HA (0% to 50%, wt/wt). Both cell types reduced the diameter of collagen alone approximately 65% at 18 hours. HA significantly increased gel contraction (diameter in mm: 0% HA, 7. 7+/-0.9; 2%, 7.1+/-0.7; 10%, 6.7+/-0.5; 50%, 5.6+/-0.9; P<0.05 for >/=10%), cell spreading and telopodia, and pericellular accumulation of collagen fibrils. These effects were mediated in part by cellular HA binding, because an antibody against CD44 receptors blocked pericellular collagen accumulation and enhanced gel contraction without altering cell shape. The role of CD44 was specific, because inhibiting receptor for hyaluronic acid-mediated motility (RHAMM) had no effect. Blocking ss(1)-integrins completely inhibited contraction of collagen, but gels containing HA required CD44 and ss(1)-integrin blockade for complete inhibition. Enhanced collagen reorganization and contraction were not attributable to increased collagenase activity, because the metalloproteinase inhibitor batimastat had no effect. In summary, HA enhanced collagen reorganization by the cell types most likely to mediate constrictive remodeling after angioplasty. These effects were CD44-dependent, thus providing a potential target for therapies to prevent constrictive remodeling and restenosis.

Hyaluronan: a multifunctional, megaDalton, stealth molecule

Hyaluronan has been implicated in biological processes such as cell adhesion, migration and proliferation. Traditionally, it was thought to be associated with the extracellular matrix, but, hyaluronan may also have unimagined roles inside the cell. Investigation of hyaluronan synthesis and degradation, the identification of new receptors and binding proteins, and the elucidation of hyaluronan-dependent signaling pathways are providing novel insights into the true biological functions of this fascinating molecule.