The calcium-activated chloride channel-associated protein rCLCA2 is expressed throughout rat epidermis, facilitates apoptosis and is downmodulated by UVB

The rodent chloride channel regulatory proteins mCLCA2 and its porcine and human homologues pCLCA2 and hCLCA2 are expressed in keratinocytes but their localization and significance in the epidermis have remained elusive. hCLCA2 regulates cancer cell migration, invasion and apoptosis, and its loss predicts poor prognosis in many tumors. Here, we studied the influences of epidermal maturation and UV-irradiation (UVR) on rCLCA2 (previous rCLCA5) expression in cultured rat epidermal keratinocytes (REK) and correlated the results with mCLCA2 expression in mouse skin in vivo. Furthermore, we explored the influence of rCLCA2 silencing on UVR-induced apoptosis. rClca2 mRNA was strongly expressed in REK cells, and its level in organotypic cultures remained unchanged during the epidermal maturation process from a single cell layer to fully differentiated, stratified cultures. Immunostaining confirmed its uniform localization throughout the epidermal layers in REK cultures and in rat skin. A single dose of UVR modestly downregulated rClca2 expression in organotypic REK cultures. The immunohistochemical staining showed that CLCA2 localized in basal and spinous layers also in mouse skin, and repeated UVR induced its partial loss. Interestingly, silencing of rCLCA2 reduced the number of apoptotic cells induced by UVR, suggesting that by facilitating apoptosis, CLCA2 may protect keratinocytes against the risk of malignancy posed by UVB-induced corrupt DNA.

Hyaluronan metabolism enhanced during epidermal differentiation is suppressed by vitamin C

BACKGROUND

Hyaluronan is a large, linear glycosaminoglycan present throughout the narrow extracellular space of the vital epidermis. Increased hyaluronan metabolism takes place in epidermal hypertrophy, wound healing and cancer. Hyaluronan is produced by hyaluronan synthases and catabolized by hyaluronidases, reactive oxygen species and KIAA1199.

OBJECTIVES

To investigate the changes in hyaluronan metabolism during epidermal stratification and maturation, and the impact of vitamin C on these events.

METHODS

Hyaluronan synthesis and expression of the hyaluronan-related genes were analysed during epidermal maturation from a simple epithelium to a fully differentiated epidermis in organotypic cultures of rat epidermal keratinocytes using quantitative reverse transcriptase polymerase chain reaction, immunostaining and Western blotting, in the presence and absence of vitamin C.

RESULTS

With epidermal stratification, both the production and the degradation of hyaluronan were enhanced, resulting in an increase of hyaluronan fragments of various sizes. While the mRNA levels of Has3 and KIAA1199 remained stable during the maturation, Has1, Has2 and Hyal2 showed a transient upregulation during stratification, Hyal1 transcription remained permanently increased and transcription of the hyaluronan receptor, Cd44, decreased. At maturation, vitamin C downregulated Has2, Hyal2 and Cd44, whereas it increased high-molecular-mass hyaluronan in the epidermis, and reduced small fragments in the medium, suggesting stabilization of epidermal hyaluronan.

CONCLUSIONS

Epidermal stratification and maturation is associated with enhanced hyaluronan turnover, and release of large amounts of hyaluronan fragments. The high turnover is suppressed by vitamin C, which is suggested to enhance normal epidermal differentiation in part through its effect on hyaluronan.

Human Keratinocytes Respond to Extracellular UTP by Induction of Hyaluronan Synthase 2 Expression and Increased Hyaluronan Synthesis

The release of nucleotides into extracellular space is triggered by insults like wounding and ultraviolet radiation, resulting in stimulatory or inhibitory signals via plasma membrane nucleotide receptors. As similar insults are known to activate hyaluronan synthesis we explored the possibility that extracellular UTP or its breakdown products UDP and UMP act as mediators for hyaluronan synthase (HAS) activation in human epidermal keratinocytes. UTP increased hyaluronan both in the pericellular matrix and in the culture medium of HaCaT cells. 10-100 μm UTP strongly up-regulated HAS2 expression, although the other hyaluronan synthases (HAS1, HAS3) and hyaluronidases (HYAL1, HYAL2) were not affected. The HAS2 response was rapid and transient, with the maximum stimulation at 1.5 h. UDP exerted a similar effect, but higher concentrations were required for the response, and UMP showed no stimulation at all. Specific siRNAs against the UTP receptor P2Y₂, and inhibitors of UDP receptors P2Y₆ and P2Y₁₄, indicated that the response to UTP was mediated mainly through P2Y₂ and to a lesser extent via UDP receptors. UTP increased the phosphorylation of p38, ERK, CREB, and Ser-727 of STAT3 and induced nuclear translocation of pCaMKII. Inhibitors of PKC, p38, ERK, CaMKII, STAT3, and CREB partially blocked the activation of HAS2 expression, confirming the involvement of these pathways in the UTP-induced HAS2 response. The present data reveal a selective up-regulation of HAS2 expression by extracellular UTP, which is likely to contribute to the previously reported rapid activation of hyaluronan metabolism in response to tissue trauma or ultraviolet radiation.

Hexosamine biosynthesis in keratinocytes: roles of GFAT and GNPDA enzymes in the maintenance of UDP-GlcNAc content and hyaluronan synthesis

UDP-N-acetylglucosamine (UDP-GlcNAc) is a glucose metabolite with pivotal functions as a key substrate for the synthesis of glycoconjugates like hyaluronan, and as a metabolic sensor that controls cell functions through O-GlcNAc modification of intracellular proteins. However, little is known about the regulation of hexosamine biosynthesis that controls UDP-GlcNAc content. Four enzymes can catalyze the crucial starting point of the pathway, conversion of fructose-6-phosphate (Fru6P) to glucosamine-6-phosphate (GlcN6P): glutamine-fructose-6-phosphate aminotransferases (GFAT1 and 2) and glucosamine-6-phosphate deaminases (GNPDA1 and 2). Using siRNA silencing, we studied the contributions of these enzymes to UDP-GlcNAc content and hyaluronan synthesis in human keratinocytes. Depletion of GFAT1 reduced the cellular pool of UDP-GlcNAc and hyaluronan synthesis, while simultaneous blocking of both GNPDA1 and GDPDA2 exerted opposite effects, indicating that in standard culture conditions keratinocyte GNPDAs mainly catalyzed the reaction from GlcN6P back to Fru6P. However, when hexosamine biosynthesis was blocked by GFAT1 siRNA, the effect by GNPDAs was reversed, now catalyzing Fru6P towards GlcN6P, likely in an attempt to maintain UDP-GlcNAc content. Silencing of these enzymes also changed the gene expression of related enzymes: GNPDA1 siRNA induced GFAT2 which was hardly measurable in these cells under standard culture conditions, GNPDA2 siRNA increased GFAT1, and GFAT1 siRNA increased the expression of hyaluronan synthase 2 (HAS2). Silencing of GFAT1 stimulated GNPDA1 and GDPDA2, and inhibited cell migration. The multiple delicate adjustments of these reactions demonstrate the importance of hexosamine biosynthesis in cellular homeostasis, known to be deranged in diseases like diabetes and cancer.

Fluorescence resonance energy transfer (FRET) and proximity ligation assays reveal functionally relevant homo- and heteromeric complexes among hyaluronan synthases HAS1, HAS2, and HAS3

In vertebrates, hyaluronan is produced in the plasma membrane from cytosolic UDP-sugar substrates by hyaluronan synthase 1-3 (HAS1-3) isoenzymes that transfer N-acetylglucosamine (GlcNAc) and glucuronic acid (GlcUA) in alternative positions in the growing polysaccharide chain during its simultaneous extrusion into the extracellular space. It has been shown that HAS2 immunoprecipitates contain functional HAS2 homomers and also heteromers with HAS3 (Karousou, E., Kamiryo, M., Skandalis, S. S., Ruusala, A., Asteriou, T., Passi, A., Yamashita, H., Hellman, U., Heldin, C. H., and Heldin, P. (2010) The activity of hyaluronan synthase 2 is regulated by dimerization and ubiquitination. J. Biol. Chem. 285, 23647-23654). Here we have systematically screened in live cells, potential interactions among the HAS isoenzymes using fluorescence resonance energy transfer (FRET) and flow cytometric quantification. We show that all HAS isoenzymes form homomeric and also heteromeric complexes with each other. The same complexes were detected both in Golgi apparatus and plasma membrane by using FRET microscopy and the acceptor photobleaching method. Proximity ligation assays with HAS antibodies confirmed the presence of HAS1-HAS2, HAS2-HAS2, and HAS2-HAS3 complexes between endogenously expressed HASs. C-terminal deletions revealed that the enzymes interact mainly via uncharacterized N-terminal 86-amino acid domain(s), but additional binding site(s) probably exist in their C-terminal parts. Of all the homomeric complexes HAS1 had the lowest and HAS3 the highest synthetic activity. Interestingly, HAS1 transfection reduced the synthesis of hyaluronan obtained by HAS2 and HAS3, suggesting functional cooperation between the isoenzymes. These data indicate a general tendency of HAS isoenzymes to form both homomeric and heteromeric complexes with potentially important functional consequences on hyaluronan synthesis.

Extracellular UDP-glucose activates P2Y14 Receptor and Induces Signal Transducer and Activator of Transcription 3 (STAT3) Tyr705 phosphorylation and binding to hyaluronan synthase 2 (HAS2) promoter, stimulating hyaluronan synthesis of keratinocytes

Hyaluronan, a major matrix molecule in epidermis, is often increased by stimuli that enhance keratinocyte proliferation and migration. We found that small amounts of UDP-sugars were released from keratinocytes and that UDP-glucose (UDP-Glc) added into keratinocyte cultures induced a specific, rapid induction of hyaluronan synthase 2 (HAS2), and an increase of hyaluronan synthesis. The up-regulation of HAS2 was associated with JAK2 and ERK1/2 activation, and specific Tyr(705) phosphorylation of transcription factor STAT3. Inhibition of JAK2, STAT3, or Gi-coupled receptors blocked the induction of HAS2 expression by UDP-Glc, the latter inhibitor suggesting that the signaling was triggered by the UDP-sugar receptor P2Y14. Chromatin immunoprecipitations demonstrated increased promoter binding of Tyr(P)(705)-STAT3 at the time of HAS2 induction. Interestingly, at the same time Ser(P)(727)-STAT3 binding to its response element regions in the HAS2 promoter was unchanged or decreased. UDP-Glc also stimulated keratinocyte migration, proliferation, and IL-8 expression, supporting a notion that UDP-Glc signals for epidermal inflammation, enhanced hyaluronan synthesis as an integral part of it.

Rab10-mediated endocytosis of the hyaluronan synthase HAS3 regulates hyaluronan synthesis and cell adhesion to collagen

Hyaluronan synthases (HAS1-3) are unique in that they are active only when located in the plasma membrane, where they extrude the growing hyaluronan (HA) directly into cell surface and extracellular space. Therefore, traffic of HAS to/from the plasma membrane is crucial for the synthesis of HA. In this study, we have identified Rab10 GTPase as the first protein known to be involved in the control of this traffic. Rab10 colocalized with HAS3 in intracellular vesicular structures and was co-immunoprecipitated with HAS3 from isolated endosomal vesicles. Rab10 silencing increased the plasma membrane residence of HAS3, resulting in a significant increase of HA secretion and an enlarged cell surface HA coat, whereas Rab10 overexpression suppressed HA synthesis. Rab10 silencing blocked the retrograde traffic of HAS3 from the plasma membrane to early endosomes. The cell surface HA coat impaired cell adhesion to type I collagen, as indicated by recovery of adhesion following hyaluronidase treatment. The data indicate a novel function for Rab10 in reducing cell surface HAS3, suppressing HA synthesis, and facilitating cell adhesion to type I collagen. These are processes important in tissue injury, inflammation, and malignant growth.

Isothiocyanate analogs targeting CD44 receptor as an effective strategy against colon cancer

Inflammatory pathway plays an important role in tumor cell progression of colorectal cancers. Although colon cancer is considered as one of the leading causes of death worldwide, very few drugs are available for its effective treatment. Many studies have examined the effects of specific COX-2 and 5-LOX inhibitors on human colorectal cancer, but the role of isothiocyanates (ITSCs) as COX-LOX dual inhibitors engaged in hyaluronan-CD44 interaction has not been studied. In the present work, we report series of ITSC analogs incorporating bioisosteric thiosemicarbazone moiety. These inhibitors are effective against panel of human colon cancer cell lines including COX-2 positive HCA-7, HT-29 cells lines, and hyaluronan synthase-2 (Has2) enzyme over-expressing transformed intestinal epithelial Apc10.1Has2 cells. Specifically, our findings indicate that HA-CD44v6-mediated COX-2/5-LOX signaling mediate survivin production, which in turn, supports anti-apoptosis and chemo-resistance leading to colon cancer cell survival. The over-expression of CD44v6shRNA as well as ITSC treatment significantly decreases the survival of colon cancer cells. The present results thus offer an opportunity to evolve potent inhibitors of HA synthesis and CD44v6 pathway and thus underscoring the importance of the ITSC analogs as chemopreventive agents for targeting HA/CD44v6 pathway.

Hyaluronan synthase 1 (HAS1) requires higher cellular UDP-GlcNAc concentration than HAS2 and HAS3

Mammals have three homologous genes encoding proteins with hyaluronan synthase activity (Has1-3), all producing an identical polymer from UDP-N-acetylglucosamine and UDP-glucuronic acid. To compare the properties of these isoenzymes, COS-1 cells, with minor endogenous hyaluronan synthesis, were transfected with human Has1-3 isoenzymes. HAS1 was almost unable to secrete hyaluronan or form a hyaluronan coat, in contrast to HAS2 and HAS3. This failure of HAS1 to synthesize hyaluronan was compensated by increasing the cellular content of UDP-N-acetyl glucosamine by ∼10-fold with 1 mm glucosamine in the growth medium. Hyaluronan synthesis driven by HAS2 was less affected by glucosamine addition, and HAS3 was not affected at all. Glucose-free medium, leading to depletion of the UDP-sugars, markedly reduced hyaluronan synthesis by all HAS isoenzymes while raising its concentration from 5 to 25 mm had a moderate stimulatory effect. The results indicate that HAS1 is almost inactive in cells with low UDP-sugar supply, HAS2 activity increases with UDP-sugars, and HAS3 produces hyaluronan at high speed even with minimum substrate content. Transfected Has2 and particularly Has3 consumed enough UDP-sugars to reduce their content in COS-1 cells. Comparison of different human cell types revealed ∼50-fold differences in the content of UDP-N-acetylhexosamines and UDP-glucuronic acid, correlating with the expression level of Has1, suggesting cellular coordination between Has1 expression and the content of UDP-sugars.

Abstract 2458: The expression of hyaluronan and hyaluronidases in cutaneous melanoma

Aberrant hyaluronan expression implicates aggressive disease progression and metastatic potential in many cancers. In tumors originating from simple epithelium, hyaluronan amount is increased both in the epithelial and stromal component and it correlates with patient's poor overall prognosis. The role of hyaluronan degrading enzymes (hyaluronidases, HYAL1-2) in cancer progression is controversial. Hyaluronidases are proposed to be both tumor suppressors and tumor promoters. In this retrospective study, we characterized the expression levels of HYAL1 and HYAL2 and correlated their expression to hyaluronan in the different stages of primary skin melanoma as well as in metastatic melanoma. Superfically (pT1) and deeply (pT4) invasive melanoma (Breslow < 1mm (n=18) and Breslow > 4mm (n=18)), in situ melanoma (n=17), lymph node metastasis (n=19), dysplastic nevi (n=28) and benign nevi samples (n=29) were analyzed for hyaluronan staining and HYAL1 and HYAL2 immunoreactivity (ABCAM antibodies) in paraffin tissue sections. Stainings were evaluated for their intensity and coverage. The tissue area for hyaluronan and HYAL1/HYAL2 positive staining was estimated with a five-level scoring from 0-4 and the staining intensity of melanocytic cells was evaluated with a four-level scoring (0-3; no color, weak, moderate and strong) by two independent observers. Compared to benign nevi and in situ melanoma, the cell-associated hyaluronan staining coverage and intensity were clearly reduced in the invasive part of melanoma with advanced Breslow depth. Strong hyaluronan staining intensity was detected in 36% of in situ melanoma cases and in 21% of superficial melanoma (Breslow < 1mm) cases, while in the deeply invasive melanoma group (Breslow > 4mm), only 6% of cases showed strong hyaluronan staining intensity. In addition, in lymph node metastases the melanoma cells showed low hyaluronan staining intensity or were totally hyaluronan negative. However, the tumor stroma was highly hyaluronan positive in all groups. HYAL1 immunoreactivity was found in melanocytic cells both in benign nevi and melanoma samples while the tumor stromal cells were negative. The coverage of HYAL2 immunoreactivity was parallel to HYAL1, although its staining intensity was lower than that of HYAL1. Our results suggest that hyaluronan content is clearly decreased in invasive primary and metastatic melanoma compared to benign nevi. The results from hyaluronan stainings will be compared with clinical follow-up data to study the prognostic value of hyaluronan in melanoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2458. doi:1538-7445.AM2012-2458

HAS3-induced accumulation of hyaluronan in 3D MDCK cultures results in mitotic spindle misorientation and disturbed organization of epithelium

The amount of hyaluronan (HA) is low in simple epithelia under normal conditions, but during tumorigenesis, trauma or inflammation HA is increased on the epithelial cells and surrounding stroma. Excessive HA in epithelia is suggested to interfere with cell-cell adhesions, resulting in disruption of the epithelial barrier function. In addition, stimulated HA synthesis has been correlated with epithelial-to-mesenchymal transition and invasion of cancer cells. However, the effects of HA overload on normal epithelial morphogenesis have not been characterized in detail. Madin-Darby canine kidney (MDCK) cells form polarized epithelial cysts, when grown in a 3-dimensional (3D) matrix. These cells were used to investigate whether stimulated HA synthesis, induced by stable overexpression of GFP-HAS3, influences cell polarization and epithelial morphogenesis. GFP-HAS3 expression in polarized MDCK cells resulted in active HA secretion at apical and basolateral membrane domains. HA-deposits interfered with the formation of cell-cell junctions, resulting in impaired barrier function. In 3D cyst cultures, HA accumulated into apical lumina and was also secreted from the basal side. The HAS3-expressing cysts failed to form a single lumen and instead displayed multiple small lumina. This phenotype was correlated with aberrant mitotic spindle orientation in dividing cells. The results of this study indicate that excess pericellular HA disturbs the normal cell-cell and cell-ECM interactions in simple epithelia, leading to aberrant epithelial morphogenesis. The morphological abnormalities observed in 3D epithelial cultures upon stimulated HAS3 expression may be related to premalignant changes, including intraluminal invasion and deregulated epithelialization, probably mediated by the mitotic spindle orientation defects.

Chronic UVR causes increased immunostaining of CD44 and accumulation of hyaluronan in mouse epidermis

Chronic intense UV radiation is the main cause of epidermal tumors. Because hyaluronan (HA), a large extracellular polysaccharide, is known to promote malignant growth, hyaluronan expression was studied in a model in which long-term UV radiation (UVR) induces epidermal tumors. Mouse back skin was exposed three times a week for 10.5 months to UVR corresponding to one minimal erythema dose, processed for histology, and stained for hyaluronan and the hyaluronan receptor CD44. This exposure protocol caused epidermal hyperplasia in most of the animals; tumors, mainly squamous cell carcinomas (SCCs), were found in ~20% of the animals. Specimens exposed to UVR showed increased hyaluronan and CD44 staining throughout the epidermal tissue. In hyperplastic areas, hyaluronan and CD44 stainings correlated positively with the degree of hyperplasia. Well-differentiated SCCs showed increased hyaluronan and CD44 staining intensities, whereas poorly differentiated tumors and dysplastic epidermis showed areas where HA and CD44 were locally reduced. The findings indicate that HA and CD44 increase in epidermal keratinocytes in the premalignant hyperplasia induced by UV irradiation and stay elevated in dysplasia and SCC, suggesting that the accumulation of hyaluronan and CD44 is an early marker for malignant transformation and may be a prerequisite for tumor formation.

Cellular content of UDP-N-acetylhexosamines controls hyaluronan synthase 2 expression and correlates with O-linked N-acetylglucosamine modification of transcription factors YY1 and SP1

Hyaluronan, a high molecular mass polysaccharide on the vertebrate cell surface and extracellular matrix, is produced at the plasma membrane by hyaluronan synthases using UDP-GlcNAc and UDP-GlcUA as substrates. The availability of these UDP-sugar substrates can limit the synthesis rate of hyaluronan. In this study, we show that the cellular level of UDP-HexNAc also controls hyaluronan synthesis by modulating the expression of HAS2 (hyaluronan synthase 2). Increasing UDP-HexNAc in HaCaT keratinocytes by adding glucosamine down-regulated HAS2 gene expression, whereas a decrease in UDP-HexNAc, realized by mannose treatment or siRNA for GFAT1 (glutamine:fructose-6-phosphate amidotransferase 1), enhanced expression of the gene. Tracing the UDP-HexNAc-initiated signal to the HAS2 promoter revealed no change in the binding of STAT3, NF-κB, and cAMP response element-binding protein, shown previously to mediate growth factor and cytokine signals on HAS2 expression. Instead, altered binding of SP1 and YY1 to the promoter correlated with cellular UDP-HexNAc content and inhibition of HAS2 expression. siRNA silencing of YY1 and SP1 confirmed their inhibitory effects on HAS2 expression. Reduced and increased levels of O-GlcNAc-modified SP1 and YY1 proteins were associated with stimulation or inhibition of HAS2 expression, respectively. Our data are consistent with the hypothesis that, by regulating the level of protein O-GlcNAc modifications, cellular UDP-HexNAc content controls HAS2 transcription and decreases the effects on hyaluronan synthesis that would result from cellular fluctuations of this substrate.

Hyaluronan synthases (HAS1-3) and hyaluronidases (HYAL1-2) in the accumulation of hyaluronan in endometrioid endometrial carcinoma

Background

Hyaluronan accumulation correlates with the degree of malignancy in many solid tumor types, including malignant endometrial carcinomas. To elucidate the mechanism of hyaluronan accumulation, we examined the expression levels of the hyaluronan synthases (HAS1, HAS2 and HAS3) and hyaluronidases (HYAL1 and HYAL2), and correlated them with hyaluronan content and HAS1-3 immunoreactivity.

Methods

A total of 35 endometrial tissue biopsies from 35 patients, including proliferative and secretory endometrium (n = 10), post-menopausal proliferative endometrium (n = 5), complex atypical hyperplasia (n = 4), grade 1 (n = 8) and grade 2 + 3 (n = 8) endometrioid adenocarcinomas were divided for gene expression by real-time RT-PCR, and paraffin embedded blocks for hyaluronan and HAS1-3 cytochemistry.

Results

The mRNA levels of HAS1-3 were not consistently changed, while the immunoreactivity of all HAS proteins was increased in the cancer epithelium. Interestingly, HAS3 mRNA, but not HAS3 immunoreactivity, was increased in post-menopausal endometrium compared to normal endometrium (p = 0.003). The median of HYAL1 mRNA was 10-fold and 15-fold lower in both grade 1 and grade 2+3 endometrioid endometrial cancers, as compared to normal endometrium (p = 0.004-0.006), and post-menopausal endometrium (p = 0.002), respectively. HYAL2 mRNA was also reduced in cancer (p = 0.02) and correlated with HYAL1 (r = 0.8, p = 0.0001). There was an inverse correlation between HYAL1 mRNA and the epithelial hyaluronan staining intensity (r = -0.6; P = 0.001).

Conclusion

The results indicated that HYAL1 and HYAL2 were coexpressed and significantly downregulated in endometrioid endometrial cancer and correlated with the accumulation of hyaluronan. While immunoreactivity for HASs increased in the cancer cells, tumor mRNA levels for HASs were not changed, suggesting that reduced turnover of HAS protein may also have contributed to the accumulation of hyaluronan.

Methyl-beta-cyclodextrin suppresses hyaluronan synthesis by down-regulation of hyaluronan synthase 2 through inhibition of Akt

Hyaluronan synthases (HAS1-3) are integral plasma membrane proteins that synthesize hyaluronan, a cell surface and extracellular matrix polysaccharide necessary for many biological processes. It has been shown that HAS is partly localized in cholesterol-rich lipid rafts of MCF-7 cells, and cholesterol depletion with methyl-beta-cyclodextrin (MbetaCD) suppresses hyaluronan secretion in smooth muscle cells. However, the mechanism by which cholesterol depletion inhibits hyaluronan production has remained unknown. We found that cholesterol depletion from MCF-7 cells by MbetaCD inhibits synthesis but does not decrease the molecular mass of hyaluronan, suggesting no major influence on HAS stability in the membrane. The inhibition of hyaluronan synthesis was not due to the availability of HAS substrates UDP-GlcUA and UDP-GlcNAc. Instead, MbetaCD specifically down-regulated the expression of HAS2 but not HAS1 or HAS3. Screening of signaling proteins after MbetaCD treatment revealed that phosphorylation of Akt and its downstream target p70S6 kinase, both members of phosphoinositide 3-kinase-Akt pathway, were inhibited. Inhibitors of this pathway suppressed hyaluronan synthesis and HAS2 expression in MCF-7 cells, suggesting that the reduced hyaluronan synthesis by MbetaCD is due to down-regulation of HAS2, mediated by the phosphoinositide 3-kinase-Akt-mTOR-p70S6K pathway.

4-Methylumbelliferone inhibits tumour cell growth and the activation of stromal hyaluronan synthesis by melanoma cell-derived factors

BACKGROUND

There is a close correlation between tumour progression and hyaluronan production, either by tumour cells or by stromal cells that are stimulated by tumour-derived factors. Inhibition of tumour stimulation of fibroblast hyaluronan may suppress tumour growth and invasion.

OBJECTIVES

To examine the effect of the hyaluronan synthesis inhibitor 4-methylumbelliferone (4-MU) on the growth of and hyaluronan synthesis by fibroblasts and C8161 and MV3 melanoma cell lines, invasion, and inhibition of tumour cell-derived factor activation of fibroblasts.

METHODS

Effects of 4-MU on growth and hyaluronan synthesis by fibroblasts and melanoma cells were examined in monolayer culture and fibroblast-contracted collagen lattices, and their effects on the growth and invasion of tumour cells into collagen lattices were also studied.

RESULTS

4-MU caused a dose-dependent growth inhibition of fibroblast and melanoma cells with maximum inhibition at 0·5 mmol L(-1) 4-MU. At this dose, 4-MU inhibited (3) H-glucosamine incorporation into fibroblast glycosaminoglycans by 52%, and hyaluronan synthesis by 64%. The relative inhibition was more pronounced when fibroblasts were stimulated with C8161 melanoma cell-conditioned medium. 4-MU reduced the level of hyaluronan in fibroblast-contracted collagen lattices, and inhibited both the growth on and invasion into the lattices by melanoma cells. This growth inhibition appears to be predominantly independent of inhibition of hyaluronan synthesis. The effect on growth inhibition was reversible, and 4-MU had no effect on apoptosis.

CONCLUSIONS

4-MU is a potent inhibitor of hyaluronan synthesis, induction of stromal hyaluronan accumulation by tumour cells, and fibroblast and melanoma cell proliferation, and results suggest that 4-MU may have potential as a tumour cell anti-invasive and antiproliferative agent.

Hyaluronan accumulation in wounded epidermis: a mediator of keratinocyte activation

The high-molecular-mass polysaccharide hyaluronan is abundant in the extracellular space between adjacent keratinocytes throughout the vital part of epidermis. It has a rapid turnover, and its content is subject to large fluctuations due to physiological and environmental conditions, with the strongest effects mediated by EGFR signaling. Using an elegant organotypic culture system, Monslow et al. (2009, this issue) demonstrate that heparin-binding (HB)-EGF released from its membrane anchor is the major ligand of EGFR in injured epidermis, accounting for the autocrine and paracrine activation of hyaluronan synthesis by the keratinocytes in the neighborhood, thus facilitating the epidermal wound-healing response.

Expression of hyaluronan synthases (HAS1-3) and hyaluronidases (HYAL1-2) in serous ovarian carcinomas: inverse correlation between HYAL1 and hyaluronan content

BACKGROUND

Hyaluronan, a tumor promoting extracellular matrix polysaccharide, is elevated in malignant epithelial ovarian tumors, and associates with an unfavorable prognosis. To explore possible contributors to the accumulation of hyaluronan, we examined the expression of hyaluronan synthases (HAS1, HAS2 and HAS3) and hyaluronidases (HYAL1 and HYAL2), correlated with hyaluronidase enzyme activity hyaluronan content and HAS1-3 immunoreactivity.

METHODS

Normal ovaries (n = 5) and 34 serous epithelial ovarian tumors, divided into 4 groups: malignant grades 1+2 (n = 10); malignant grade 3 (n = 10); borderline (n = 4) and benign epithelial tumors (n = 10), were analyzed for mRNA by real-time RT-PCR and compared to hyaluronidase activity, hyaluronan staining, and HAS1-3 immunoreactivity in tissue sections of the same specimens.

RESULTS

The levels of HAS2 and HAS3 mRNA (HAS1 was low or absent), were not consistently increased in the carcinomas, and were not significantly correlated with HAS protein or hyaluronan accumulation in individual samples. Instead, the median of HYAL1 mRNA level was 69% lower in grade 3 serous ovarian cancers compared to normal ovaries (P = 0.01). The expression of HYAL1, but not HYAL2, significantly correlated with the enzymatic activity of tissue hyaluronidases (r = 0.5; P = 0.006). An inverse correlation was noted between HYAL1 mRNA and the intensity of hyaluronan staining of the corresponding tissue sections (r = -0.4; P = 0.025).

CONCLUSION

The results indicate that in serous epithelial ovarian malignancies HAS expression is not consistently elevated but HYAL1 expression is significantly reduced and correlates with the accumulation of hyaluronan. (233 words).

4-Methylumbelliferone inhibits hyaluronan synthesis by depletion of cellular UDP-glucuronic acid and downregulation of hyaluronan synthase 2 and 3

Hyaluronan accumulation on cancer cells and their surrounding stroma predicts an unfavourable disease outcome, suggesting that hyaluronan enhances tumor growth and spreading. 4-Methylumbelliferone (4-MU) inhibits hyaluronan synthesis and retards cancer spreading in experimental animals through mechanisms not fully understood. These mechanisms were studied in A2058 melanoma cells, MCF-7 and MDA-MB-361 breast, SKOV-3 ovarian and UT-SCC118 squamous carcinoma cells by analysing hyaluronan synthesis, UDP-glucuronic acid (UDP-GlcUA) content, and hyaluronan synthase (HAS) mRNA levels. The maximal inhibition in hyaluronan synthesis ranged 22-80% in the cell lines tested. Active glucuronidation of 4-MU produced large quantities of 4-MU-glucuronide, depleting the cellular UDP-GlcUA pool. The maximal reduction varied between 38 and 95%. 4-MU also downregulated HAS mRNA levels: HAS3 was 84-60% lower in MDA-MB-361, A2058 and SKOV-3 cells. HAS2 was the major isoenzyme in MCF-7 cells and lowered by 81%, similar to 88% in A2058 cells. These data indicate that both HAS substrate and HAS2 and/or HAS3 mRNA are targeted by 4-MU. Despite different target point sensitivities, the reduction of hyaluronan caused by 4-MU was associated with a significant inhibition of cell migration, proliferation and invasion, supporting the importance of hyaluronan synthesis in cancer, and the therapeutic potential of hyaluronan synthesis inhibition.

Depletion of cell surface CD44 in nonmelanoma skin tumours is associated with increased expression of matrix metalloproteinase 7

BACKGROUND

Expression of matrix metalloproteinase (MMP)-7 and MMP-9 is low in the normal epidermis and is induced by physiological processes such as wound healing, but also malignant transformation of epidermal cells. The activity of both MMPs has been associated with the hyaluronan (HA) receptor CD44. We previously reported that the levels of CD44 and HA differ between the two types of epidermal tumours, basal (BCC) and squamous cell carcinoma (SCC), as well as between different grades of SCC.

OBJECTIVES

To investigate if the immunostaining patterns of MMP-7 and MMP-9 correlate to those of CD44 and HA in BCC and SCC.

METHODS

Paraffin sections from 71 BCCs, 21 in situ SCCs and 27 SCCs were immunostained for MMP-7 and -9.

RESULTS

Positive immunostaining for MMP-7 and MMP-9 was found in tumour cells of both BCC and SCC, while the staining intensity tended to be stronger in SCC. The staining intensity of MMP-7 was inversely correlated with that of CD44 in both tumour types. In well-differentiated SCC, the intensity of MMP-7 was generally weak, while CD44 staining was strong and homogeneously distributed. In poorly differentiated SCC, an increase in MMP-7 was seen, and the staining intensity of CD44 became weak and was locally absent. No correlation was seen between MMP-9 and CD44 or either of the two MMPs and HA.

CONCLUSIONS

Our results show that in nonmelanoma skin tumours MMP-7 and -9 are present in the tumour cells, and suggest a link between MMP-7 activity and the depletion of cell surface CD44.

Low molecular weight hyaluronan shielding of DNA/PEI polyplexes facilitates CD44 receptor mediated uptake in human corneal epithelial cells

AIM

It was the aim of this study to prepare purified DNA/PEI polyplexes, which are coated with hyaluronan to facilitate CD44 receptor mediated uptake of the DNA/PEI polyplex and to reduce unspecific interactions of the complex with negatively charged extracellular matrix components on the ocular surface.

METHODS

Hyaluronans of different molecular weights (<10 kDa, 10-30 kDa and 30-50 kDa) were isolated after enzymatic degradation of high molecular weight hyaluronan via ultrafiltration by centrifugation. The influence of the different hyaluronans used for coating on the stability and transfection efficiency of the complexes was evaluated in vitro. Transfection and uptake studies were performed in human corneal epithelial (HCE) cells. CD44 receptor expression of this cell model was evaluated by immunohistochemistry.

RESULTS

Coating of purified DNA/PEI polyplexes with low molecular weight hyaluronan (<10 kDa) facilitated receptor-mediated uptake via the CD44 receptor in HCE cells, increased complex stability in vitro, and effectively shielded the positive surface charges of the polyplex without decreasing its transfection efficiency. Higher molecular weights and larger amounts of hyaluronan in the complexes resulted in lesser improvements in the stability and transfection efficacy of the complexes.

CONCLUSIONS

Coating of polyplexes with low molecular weight hyaluronan is a promising strategy for gene delivery to the ocular surface, where CD44 receptor mediated uptake decreased cytotoxicity and reduced non-specific interactions with the negatively charged extracellular matrix components are considered beneficial for increased transfection efficiency of non-viral vectors.

Hyaluronan in human tumors: pathobiological and prognostic messages from cell-associated and stromal hyaluronan

Cancers are supported by a distinct type of connective tissue stroma, crucial for tumor survival and advancement. Hyaluronan is a major matrix molecule in the stroma of many common tumors, and involved in their growth and spreading. Here we focus in recent data on stromal hyaluronan in human tumors, and that on the surface of the malignant cells. Hyaluronan accumulation is most conspicuous in malignancies that develop in cells and tissues normally devoid of hyaluronan, such as single layered epithelia and their hyaluronan-poor connective tissue stroma. The magnitude of the hyaluronan accumulation in the malignant epithelium itself (e.g. colon and gastric cancers) or tumor stroma (breast, ovarian, prostate cancers) strongly correlates with an unfavorable prognosis of the patient, i.e. advancement of the malignancy. A completely different pattern arises from stratified epithelia that normally produce hyaluronan and are surrounded by a hyaluronan-rich stroma. The cell surface of the latter group of tumors (e.g. squamous cell carcinomas of skin, mouth, larynx and esophagus, and skin melanoma) show abundant hyaluronan which tends to get reduced and patchy in the most advanced stages of the tumors, suggesting enhanced turnover. While the assays of human tumors represent snapshots of currently unknown processes and kinetics of hyaluronan metabolism, it is obvious that hyaluronan accumulation at some stage is an inherent feature in most of the common epithelial malignant tumors. The possible contributions of inflammatory cells, stem cells, mutated stromal cells, or otherwise deranged growth factor exchange between stromal and cancer cells are discussed as possible explanations to hyaluronan abundance in the tumors. The importance of hyaluronan in human tumor progression will be further clarified when drugs become available to modify hyaluronan metabolism.

Mannose inhibits hyaluronan synthesis by down-regulation of the cellular pool of UDP-N-acetylhexosamines

We found that d-mannose dose-dependently decreases hyaluronan synthesis in cultured epidermal keratinocytes to approximately 50%, whereas glucose, galactose, and fructose up to 20 mm concentration had no effect. The full inhibition occurred within 3 h following introduction of mannose and did not involve down-regulation of hyaluronan synthase (Has1-3) mRNA. Following introduction of mannose, there was an approximately 50% reduction in the cellular concentration of UDP-N-acetylhexosamines (UDP-HexNAc, i.e. UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine). On the other hand, 2 mm glucosamine in the culture medium increased UDP-HexNAc content, stimulated hyaluronan secretion, and negated the effect of mannose, supporting the notion that the inhibition by mannose on hyaluronan synthesis was because of down-regulated UDP-HexNAc content. The content of UDP-glucuronic acid, the other building block for hyaluronan synthesis, was not reduced by mannose but declined from 39 to 14% of controls by 0.2-1.0 mm 4-methylumbelliferone, another compound that inhibits hyaluronan synthesis. Applying 4-methylumbelliferone and mannose together produced the expected reductions in both UDP sugars but no additive reduction in hyaluronan production, indicating that the concentration of each substrate alone can limit hyaluronan synthesis. Mannose is a potentially useful tool in studies on hyaluronan-dependent cell functions, as demonstrated by reduced rates of keratinocyte proliferation and migration, functions known to depend on hyaluronan synthesis.

Induction of hyaluronan cables and monocyte adherence in epidermal keratinocytes

Hyaluronan attached to cell surface can form at least two very different structures; a pericellular coat close to plasma membrane and hyaluronan chains coalesced into "cables" that can span several cell lengths. The hyaluronan in cables, induced by many inflammatory agents, can bind leukocytes, whereas that in the pericellular coat does not contribute to leukocyte binding. Therefore, this structural change seems to have a major role in inflammation. In the present study we checked whether cells of squamous epithelium, like epidermal keratinocytes, can form hyaluronan cables and bind leukocytes. In addition, we checked whether hyaluronan synthesis is affected during the induction of cables. Control keratinocytes expressed pericellular hyaluronan as small patches on plasma membrane. But when treated with inflammatory agents or stressful conditions (tunicamycin, interleukin-1beta, tumor necrosis factor-alpha, and high glucose concentration), hyaluronan organization changed into cable-like structures that avidly bound monocytes. Simultaneously, the total amount of secreted hyaluronan was slightly decreased, and the expression levels of hyaluronan synthases (Has1-3) and CD44 were not significantly changed. The results show that epidermal keratinocytes can form cables and bind leukocytes under inflammatory provocation and that these effects are not dependent on stimulation of hyaluronan secretion.

Hyaluronan-dependent pericellular matrix

Hyaluronan is a multifunctional glycosaminoglycan that forms the structural basis of the pericellular matrix. Hyaluronan is extruded directly through the plasma membrane by one of three hyaluronan synthases and anchored to the cell surface by the synthase or cell surface receptors such as CD44 or RHAMM. Aggregating proteoglycans and other hyaluronan-binding proteins, contribute to the material and biological properties of the matrix and regulate cell and tissue function. The pericellular matrix plays multiple complex roles in cell adhesion/de-adhesion, and cell shape changes associated with proliferation and locomotion. Time-lapse studies show that pericellular matrix formation facilitates cell detachment and mitotic cell rounding. Hyaluronan crosslinking occurs through various proteins, such as tenascin, TSG-6, inter-alpha-trypsin inhibitor, pentraxin and TSP-1. This creates higher order levels of structured hyaluronan that may regulate inflammation and other biological processes. Microvillous or filopodial membrane protrusions are created by active hyaluronan synthesis, and form the scaffold of hyaluronan coats in certain cells. The importance of the pericellular matrix in cellular mechanotransduction and the response to mechanical strain are also discussed.

Hyaluronan synthesis induces microvillus-like cell surface protrusions

Hyaluronan synthases (HASs) are plasma membrane enzymes that simultaneously elongate, bind, and extrude the growing hyaluronan chain directly into extracellular space. In cells transfected with green fluorescent protein (GFP)-tagged Has3, the dorsal surface was decorated by up to 150 slender, 3-20-microm-long microvillus-type plasma membrane protrusions, which also contained filamentous actin, the hyaluronan receptor CD44, and lipid raft microdomains. Enzymatic activity of HAS was required for the growth of the microvilli, which were not present in cells transfected with other GFP proteins or inactive GFP-Has3 mutants or in cells incubated with exogenous soluble hyaluronan. The microvilli induced by HAS3 were gradually withered by introduction of an inhibitor of hyaluronan synthesis and rapidly retracted by hyaluronidase digestion, whereas they were not affected by competition with hyaluronan oligosaccharides and disruption of the CD44 gene, suggesting independence of hyaluronan receptors. The data bring out the novel concept that the glycocalyx created by dense arrays of hyaluronan chains, tethered to HAS during biosynthesis, can induce and maintain prominent microvilli.

Plasma membrane residence of hyaluronan synthase is coupled to its enzymatic activity

Hyaluronan is a multifunctional glycosaminoglycan up to 10(7) Da molecular mass produced by the integral membrane glycosyltransferase, hyaluronan synthase (HAS). When expressed in keratinocytes, N-terminally tagged green fluorescent protein-HAS2 and -HAS3 isoenzymes were found to travel through endoplasmic reticulum (ER), Golgi, plasma membrane, and endocytic vesicles. A distinct enrichment of plasma membrane HAS was found in cell protrusions. The total turnover time of HAS3 was 4-5 h as judged by the green fluorescent protein signal decay and hyaluronan synthesis inhibition in cycloheximide-treated cells. The transfer from ER to Golgi took about 1 h, and the dwell time on the plasma membrane was less than 2 h in experiments with a relief and introduction, respectively, of brefeldin A. Constructs of HAS3 with 16- and 45-amino-acid C-terminal deletions mostly stayed within the ER, whereas a D216A missense mutant was localized within the Golgi complex but not the plasma membrane. Both types of mutations were almost or completely inactive, similar to the wild type enzyme that had its entry to the plasma membrane experimentally blocked by brefeldin A. Inhibition of hyaluronan synthesis by UDP-glucuronic acid starvation using 4-methyl-umbelliferone also prevented HAS access to the plasma membrane. The results demonstrate that 1) a latent pool of HAS exists within the ER-Golgi pathway; 2) this pool can be rapidly mobilized and activated by insertion into the plasma membrane; and 3) inhibition of HAS activity through mutation or substrate starvation results in exclusion of HAS from the plasma membrane.

Tumour regulation of fibroblast hyaluronan expression: a mechanism to facilitate tumour growth and invasion

Hyaluronan, a high molecular weight glycosaminoglycan is associated with cellular proliferation and migration. In a number of different tumour types, there is a close correlation between tumour progression and hyaluronan production, either by the tumour cells or the surrounding stromal cells. We have examined the ability of an aggressive melanoma cell line (C8161) to stimulate the synthesis of fibroblast hyaluronan, and the association of cell-surface CD44 receptors and hyaluronan with invasion. Melanoma cell-conditioned medium (CM) prepared in low glucose medium (1 mg/ml) stimulated the synthesis of fibroblast glycosaminoglycan as measured by [3H] glucosamine incorporation, and the synthesis of hyaluronan as measured using a specific hyaluronan-binding plate assay, while tumour cell-CM prepared in high glucose medium (4.5 mg/ml) inhibited the synthesis of fibroblast glycosaminoglycan. High glucose tumour cell-CM contained large amounts of lactate that appeared to inhibit the tumour-derived factor stimulation of fibroblast glycosaminoglycan synthesis, as removal of the lactate restored the stimulating activity. Melanoma cells seeded on contracted collagen lattices and incubated at the air/liquid interface rapidly formed a multilayered cell mass on the surface, with significant invasion of the gel. Hyaluronan staining was apparent within the collagen gel, and strong staining was seen around the invading tumour cells, but not around those cell layers near the surface. CD44 expression on the tumour cells was confined to those invading cells and corresponded to cellular hyaluronan staining. Hyaluronan staining was also apparent around and between tumour cells invading fibroblast-free collagen lattices. Monolayer cultures of C8161 cells stained strongly for CD44, but few cells stained for hyaluronan, while no detectable hyaluronan was released into the medium. In summary, the C8161 melanoma cells stimulated the synthesis of fibroblast hyaluronan, and in collagen lattices, only the invasive tumour cells expressed CD44 and hyaluronan, either in the presence or absence of fibroblasts.

CD44 expression indicates favorable prognosis in epithelial ovarian cancer

PURPOSE

The purpose of this study was to investigate the expression and prognostic significance of CD44 in epithelial ovarian cancer.

EXPERIMENTAL DESIGN

We analyzed the expression of CD44 by immunohistochemistry in 307 epithelial ovarian cancers and evaluated its relation to hyaluronan, clinicopathological factors, and prognosis.

RESULTS

Fifty-one percent of the tumors had a high proportion of CD44-positive cells (i.e., >/==" BORDER="0">10%), and this high CD44 expression was significantly associated with cancer cell-associated hyaluronan, well-differentiated tumor, mucinous histological type, and early stage of the tumor. High CD44 expression predicted better 5-year overall survival (50% versus 22%) and recurrence-free survival (70% versus 34%) in the univariate analyses (P < 0.00005 for both). In the Cox multivariate analyses, the independent predictors of overall survival at 5 years were primary residual tumor (P < 0.0005), International Federation of Gynecologists and Obstetricians (FIGO) stage (P = 0.001), histological grade (P = 0.014), adjuvant chemotherapy (P = 0.004), and stromal hyaluronan level (P < 0.0005), but not CD44. However, the expression of CD44 (P = 0.04) and stromal hyaluronan (P = 0.005) were both independent predictors of recurrence-free survival at 5 years, together with the size of the primary residual tumor (P < 0.0005) and histological type (P = 0.043).

CONCLUSIONS

The relatively frequent ectopic expression of CD44 on ovarian cancer cells is thus related to well-differentiated, early-stage tumor and long survival of the patients. Thus, whereas CD44-expressing cancer cells may adhere and implant to the hyaluronan-positive mesothelium, at least in model systems, high expression of CD44 in the tumor does not bring about an unfavorable prognosis.

Strong hyaluronan expression in the full-thickness rat articular cartilage repair tissue

Articular cartilage lesions have a poor capacity to regenerate. In full-depth articular cartilage defects, the repair process involves an ingrowth of mesenchymal cells from the bone marrow to the injured area, and these cells attempt to restore the lesion with cartilage-like repair tissue. In this study, we investigated histologically the distribution of hyaluronan in the rat repair tissue in relation to other glycosaminoglycans. Full-depth lesions were drilled to the weight-bearing region of rat medical femoral condyle. The rats were divided into two groups: intermittent active motion (IAM) and running training (RT) groups. In the RT group, programmed exercise was started 1 week after surgery, while the rats in the IAM group could move freely in their cages. The lesions were investigated 4 and 8 weeks after the surgery. Semiquantitative histological grading showed no significant differences in the repair between the groups. In normal articular cartilage, hyaluronan was stained mainly around chondrocytes. During repair, strong hyaluronan staining was observed in loose mesenchymal tissue, while in the repair area undergoing endochondral ossification, hyaluronan was intensively stained mainly around the hypertrophic chondrocytes. Remarkably strong staining for hyaluronan was noticed in areas of apparent mesenchymal progenitor cell invasion, the areas being simultaneously devoid of staining for keratan sulphate. In conclusion, hyaluronan is strongly expressed in the early cartilage repair tissue, and its staining intensity and distribution shows very sensitively abnormal articular cartilage structure.

Reduced level of CD44 and hyaluronan associated with unfavorable prognosis in clinical stage I cutaneous melanoma

The cell surface glycoprotein CD44 and its ligand, hyaluronan (HA), enhance growth and metastatic capacity of melanoma cells in vitro, but their clinical significance in primary cutaneous melanoma is still unclear. Therefore, we studied whether the levels of CD44 and HA associate with disease progression and survival of cutaneous melanoma. A series of 292 clinical stage I cutaneous melanomas was analyzed by immunohistochemistry using an anti-CD44H antibody (clone 2C5). HA was demonstrated histochemically using a biotinylated HA-specific affinity probe (bHABC). The reduced staining levels of CD44 and HA were associated with each other and indicators of progressive disease. Reduced CD44 and HA level, high tumor thickness, high pT category, high Clark's level, bleeding, and male gender predicted short univariate recurrence free survival (RFS) and overall survival (OS). In Cox's multivariate analysis (N: = 251), the decreased level of CD44, high tumor thickness, and bleeding predicted independently short RFS. High tumor thickness and bleeding were associated with short OS. We conclude that the reduced cell surface CD44 and HA levels associate with poor prognosis in clinical stage I cutaneous melanoma. The notion that the decreased level of CD44 independently predicts short RFS suggests that reduced cell surface CD44 enhances the spreading potential in localized cutaneous melanoma and that quantification of CD44 offers a prognostic tool for its clinical evaluation.

A preformed basal lamina alters the metabolism and distribution of hyaluronan in epidermal keratinocyte "organotypic" cultures grown on collagen matrices

A rat epidermal keratinocyte (REK) line which exhibits histodifferentiation nearly identical to the native epidermis when cultured at an air-liquid interface was used to study the metabolism of hyaluronan, the major intercellular macromolecule present in basal and spinous cell layers. Two different support matrices were used: reconstituted collagen fibrils with and without a covering basal lamina previously deposited by canine kidney cells. REKs formed a stratified squamous, keratinized epithelium on both support matrices. Hyaluronan and its receptor, CD44, colocalized in the basal and spinous layers similar to their distribution in the native epidermis. Most (approximately 75%) of the hyaluronan was retained in the epithelium when a basal lamina was present while most (approximately 80%) diffused out of the epithelium in its absence. While REKs on the two matrices synthesized hyaluronan at essentially the same rate, catabolism of this macromolecule was much higher in the epithelium on the basal lamina (half-life approximately 1 day, similar to its half-life in native human epidermis). The formation of a true epidermal compartment in culture bounded by the cornified layer on the surface and the basal lamina subjacent to the basal cells provides a good model within which to study epidermal metabolism.

High levels of stromal hyaluronan predict poor disease outcome in epithelial ovarian cancer

Several malignant tumors accumulate hyaluronan, a matrix component suggested to promote cancer cell migration and growth. To explore the potential clinical importance of this concept, we assessed the hyaluronan levels in epithelial ovarian cancer. A biotinylated affinity probe specific for hyaluronan was prepared and applied to histological sections of 309 epithelial ovarian cancers and 45 matched metastatic lesions. The staining was scored according to the percentage area of strong hyaluronan signal of total peri- and intratumoral stroma as low (<35%), moderate (35-75%), or high (>75%). Low, moderate, and high levels of stromal hyaluronan were observed in 95, 116, and 98 carcinomas, respectively. The high stromal hyaluronan level was significantly associated with poor differentiation, serous histological type, advanced stage, and large primary residual tumor, whereas it was not correlated with high CD44 expression on cancer cells. The 5-year outlook of the disease deteriorated with increasing stromal hyaluronan levels for both overall (45% versus 39% versus 26%; P = 0.002) and recurrence-free (66% versus 56% versus 40%; P = 0.008) survival. High levels of stromal hyaluronan were more frequent in metastatic lesions than in primary tumors (z = -3.9; P = 0.0001). In Cox's multivariate analyses, high level of stromal hyaluronan was an independent prognostic factor in all patients, as well as in stage-specific subgroups. These results suggest that stromal hyaluronan accumulation may be a powerful enhancer of tumor progression and, as such, provides a novel, independent prognostic marker and a potential target of therapy.

CD44 expression marks the onset of keratinocyte stratification and mesenchymal maturation into fibrous dermis in fetal human skin

The cell surface glycoprotein CD44 is involved in active cell movement, cancer metastasis, and morphogenesis. We studied its expression in fetal human skin using an antibody specific for CD44v3 and another that recognizes all CD44 forms. In embryonic and early fetal skin, only cells with dendritic morphology expressed CD44. The first keratinocyte expression of CD44 occurred in the basal cells on the eleventh week. Later, the suprabasal cells also turned positive, whereas periderm and the terminally differentiated cells remained negative at all stages. Maturation of the early mesenchyme towards dermis at the eleventh week was associated with an increase in the number of CD44-positive cells, and later the fibrous extracellular matrix also became CD44-positive. During hair induction, the epithelium showed a transient downregulation of CD44. Later, the follicular cells regained CD44. Cells in the primordial dermal papilla displayed a continuously strong signal. The sweat gland anlagen showed faint CD44 positivity. Exon 3 was present in the CD44 of keratinocytes and their derivatives but was absent in dermis. CD44 expression in human fetal skin is a relatively late event, associated with maturation and adult-type differentiation both in epidermal keratinocytes and in dermal fibroblastic cells.(J Histochem Cytochem 47:1617-1624, 1999)

Hyaluronan expression in gastric cancer cells is associated with local and nodal spread and reduced survival rate

Hyaluronan (HA), an extracellular high-molecular-mass polysaccharide, is supposed to be involved in the growth and progression of malignant tumours. We studied the cellular expression of HA in 215 operated stage I-IV gastric cancer patients using a specific biotinylated probe. Most (93%) of the tumours showed HA staining in their parenchyma, whereas the stroma inside and around the tumour was stained in every case. When HA expression was compared with the clinical and histological features of the tumours, a strong staining intensity in the tumour parenchyma was found to be associated with deep tumour invasion (pT3 or 4) and with mixed type of Laurén. A high proportion of HA-positive cells of all neoplastic cells was significantly associated with deep tumour invasion, nodal metastasis, positive lymphatic invasion, poor differentiation grade, as well as with inferior prognosis in univariate survival analysis. However, in multivariate analysis, only pT, pN, and vascular and lymphatic invasion emerged as independent predictors of survival in gastric cancer. The results indicate that ectopic HA expression is a frequent feature of gastric adenocarcinoma, and is associated with tumour progression and poor survival rate.

Expression of hyaluronan in normal and dysplastic bronchial epithelium and in squamous cell carcinoma of the lung

A series of 85 lung/bronchial tissue samples from 76 patients consisting of normal, metaplastic and dysplastic epithelium and different types of lung carcinomas were analyzed for the distribution of hyaluronan (HA), using a biotinylated hyaluronan binding complex as an HA-specific probe. The normal pseudo-stratified columnar bronchial epithelium was either negative for HA or displayed a weak staining around the basal cells. The epithelia of serous and mucous bronchial glands were HA negative whereas the submucosal connective tissue was strongly positive. In metaplastic, dysplastic and carcinoma in situ lesions the whole epithelium from basal to uppermost cells expressed HA on plasma membranes. Epithelial HA was also found in squamous cell carcinomas, but not in adenocarcinomas, carcinoid tumors or small cell carcinomas of the lung. Whereas epithelial HA was present in all lesions of the squamous cell type, the staining intensity displayed great local variability in 50% of the cases with severe dysplasia, carcinoma in situ and squamous cell carcinomas. In squamous cell carcinomas, such an irregular staining pattern was significantly associated with poor differentiation. Our results indicate that the expression of HA in different bronchial lesions and lung tumors is restricted to those showing squamous cell differentiation, being absent from other types of lung carcinomas. The increase of HA depleted areas in poorly differentiated squamous cell carcinomas emphasizes the important role of HA in tumor differentiation. HA on carcinoma cell surface may influence tumor growth and metastatic behavior.

Expression of hyaluronan in benign and malignant breast lesions

Hyaluronan (HA) is one of the extracellular-matrix components involved in wound healing, tumour growth and metastasis. Due to the limited data on HA expression in benign and malignant breast lesions, we analyzed its presence in these lesions by using the biotinylated-hyaluronan-binding region and the link-protein complex (bHABC) of cartilage proteoglycan as a specific probe. In all benign breast lesions, the expression of HA was restricted to the stromal connective tissue, the ductal epithelial cells being completely devoid of HA. In malignant breast tumours, the intensity of stromal HA staining was significantly stronger than in benign lesions. In addition, HA was detected on cell membranes or in cytoplasms of adenocarcinoma cells, in some cases of ductal carcinoma in situ and in 31% of malignant tumours. The staining pattern was mostly similar in all breast-cancer types studied, i.e., ductal, lobular, tubular, mucinous and medullary. In ductal breast cancer, intense HA expression in stroma and carcinoma cells correlated statistically significantly to poor differentiation of carcinoma, suggesting that altered HA expression may affect the mechanisms of breast-cancer progression.

Reactive oxygen species contribute to epidermal hyaluronan catabolism in human skin organ culture

Hyaluronan (HA) is produced by keratinocytes in human skin organ culture, and degraded locally in epidermis by an unknown metabolic route. The present work tested whether reactive oxygen species (ROS), spontaneously produced in the tissue, could contribute to HA catabolism in epidermis. Epidermal HA was endogenously labeled with 3H-glucosamine for 24 h, then chased for 24 h in the presence of superoxide dismutase (SOD) and catalase to reduce the concentration of ROS. In control cultures, 35% of labeled HA was degraded during the 24 h chase while the corresponding figures in the presence of SOD and catalase were 19% and 23%, respectively (p < 0.05). Methionine, a quencher of hypochlorous acid, did not significantly inhibit the degradation. In additional experiments, the iron and copper chelator Detapac was even more effective, reducing the degradation to 8-9%, and suggesting that the ROS responsible for the degradation were produced in the Fenton reaction. Dermal HA, and proteoglycans in both epidermis and dermis were not influenced by the treatments, indicating that the inhibition by SOD, catalase and Detapac on epidermal HA catabolism was specific. It is suggested that endogenous ROS is involved in the catabolism human epidermal HA.

Ultrastructural localization of keratinocyte surface associated heparan sulphate proteoglycans in human epidermis

Fixation and staining procedures were developed for the electron microscopic demonstration of glycosaminoglycans (GAGs) in human epidermis. En bloc staining with cuprolinic blue (CB), ruthenium red (RR) and tannic acid (TA) in the primary fixative were applied for the localization of the GAGs. Removal of the epidermal basal lamina and underlying dermis was a prerequisite for stain penetration. In CB-fixed specimens 50 nm long, rod-like granules were found attached to keratinocyte cell surfaces, while the RR- and TA-fixed specimens contained round granules (luminal diameter 10 and 30 nm, respectively). The stainability of the CB-positive granules in the presence of 0.3 mol/l MgCl2 indicated that they contained sulphated GAGs. Prefixation digestions of epidermal sheets with chondroitinase ABC. Streptomyces hyaluronidase, and heparitinase showed that the RR-positive granules also contained sulphated GAGs, mostly heparan sulphate. The granules visualized with TA on keratinocytes were susceptible to heparitinase treatment, but the abundance of TA-staining suggested that TA also stained structures other than heparan sulphate. The EM data was in accordance with the 35SO4 labelling experiments showing that heparan sulphate was the major sulphated GAG synthesized in epidermis, whereas chondroitin/dermatan sulphates comprised about one fifth of the total activity incorporated. The distributions of the CB-, RR- and TA-positive granules on cell surfaces were similar. The morphology of the proteoglycan granules was probably determined by the extent of the GAG-chain collapse following binding to each of the dyes.