A gene on the HER2 amplicon, C35, is an oncogene in breast cancer whose actions are prevented by inhibition of Syk

Background:

C35 is a 12 kDa membrane-anchored protein endogenously over-expressed in many invasive breast cancers. C35 (C17orf37) is located on the HER2 amplicon, between HER2 and GRB7. The function of over-expressed C35 in invasive breast cancer is unknown.

Methods:

Tissue microarrays containing 122 primary human breast cancer specimens were used to examine the association of C35 with HER2 expression. Cell lines over-expressing C35 were generated and tested for evidence of cell transformation in vitro.

Results:

In primary breast cancers high levels of C35 mRNA expression were associated with HER2 gene amplification. High levels of C35 protein expression were associated with hallmarks of transformation, such as, colony growth in soft agar, invasion into collagen matrix and formation of large acinar structures in three-dimensional (3D) cell cultures. The transformed phenotype was also associated with characteristics of epithelial to mesenchymal transition, such as adoption of spindle cell morphology and down-regulation of epithelial markers, such as E-cadherin and keratin-8. Furthermore, C35-induced transformation in 3D cell cultures was dependent on Syk kinase, a downstream mediator of signalling from the immunoreceptor tyrosine-based activation motif, which is present in C35.

Conclusion:

C35 functions as an oncogene in breast cancer cell lines. Drug targeting of C35 or Syk kinase might be helpful in treating a subset of patients with HER2-amplified breast cancers.

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.

Gadodiamide contrast agent 'activates' fibroblasts: a possible cause of nephrogenic systemic fibrosis

Nephrogenic systemic fibrosis (NSF) is a fibrotic disease generating intense interest due to its recent discovery, and unknown cause. It appears confined to patients with renal disease and presents as grossly thickened, indurated, tight skin that is woody to palpation. Histologically, the dermis contains thickened collagen bundles, numerous plump fibroblast-like cells, and elevated hyaluronan expression. Recent data suggest a link between the use of gadolinium chelate as an MRI contrast agent and the onset of the disease. Fibroblasts from the lesions of six NSF patients, all of whom were exposed to gadodiamide, were compared with control fibroblasts for hyaluronan and collagen synthesis. Serum from NSF patients was assessed for fibroblast hyaluronan-stimulating activity, collagen synthesis, and gadodiamide for its effect on fibroblast proliferation and matrix synthesis. NSF fibroblasts synthesized excess levels of hyaluronan and collagen compared with control fibroblasts, with up to 2.8-fold and 3.3-fold increases, respectively. NSF patient serum stimulated control fibroblast hyaluronan synthesis by up to 7-fold, and collagen synthesis by up to 2.4-fold. 1 mM gadodiamide added to culture medium stimulated fibroblast growth in a dose-dependent manner, decreasing their doubling time from 28 h to 22 h, and increasing the maximum cell density. Even a short exposure to gadodiamide stimulated cell growth, suggesting that the cells were activated by the gadodiamide. The growth of fibroblasts within contracted collagen lattices was also significantly stimulated by gadodiamide, while fibroblasts exposed to gadodiamide synthesized increased levels of hyaluronan. Control fibroblasts exposed to gadodiamide, and NSF fibroblasts exhibited an extensive pericellular coat of hyaluronan, and expressed alpha-smooth muscle actin. Gadolinium chloride did not affect fibroblast growth. This report demonstrates that NSF fibroblasts synthesize excess levels of hyaluronan and collagen, and that gadodiamide stimulates control fibroblast growth, matrix synthesis, and differentiation into myofibroblasts, suggesting a possible role for gadodiamide in the pathophysiology of NSF.

Cutaneous mucinosis associated with dermatomyositis and nephrogenic fibrosing dermopathy: fibroblast hyaluronan synthesis and the effect of patient serum

BACKGROUND

Dermal mucin is an amorphous gelatinous substance composed primarily of hyaluronan (HA) and sulphated glycosaminoglycans (GAGs). In primary cutaneous mucinosis, accumulation of mucin is a characteristic feature of lichen myxoedematosus, scleromyxoedema and reticular erythematous mucinosis. Secondary mucinoses are disorders where mucin deposition is an additional finding, and deposition is associated with lupus erythematosus, dermatomyositis, scleroderma and granuloma annulare. The underlying cause of the abnormal mucin deposition is unknown. An increasing number of cases of a fibromucinous scleromyxoedema-like disorder associated with renal dysfunction, recently termed nephrogenic fibrosing dermopathy (NFD), is being reported.

OBJECTIVES

To examine the synthesis of sulphated GAGs and HA by fibroblasts derived from uninvolved and involved skin of a patient with dermatomyositis and two patients with NFD, and the effect of patient serum.

METHODS

GAGs were quantified by a radiometric assay and HA was determined by an enzyme-linked HA-binding protein assay.

RESULTS

We found that fibroblasts derived from active lesions of NFD synthesize elevated levels of GAGs, and in particular HA, compared with normal controls, while serum from the patient with dermatomyositis and the two patients with NFD stimulates GAG synthesis, including HA synthesis, by both control and patient fibroblasts.

CONCLUSIONS

Fibroblasts from patients with active NFD are either activated to synthesize elevated levels of HA or contain another cell type, possibly derived from circulating fibrocytes. In both disorders, there is additionally a serum-derived factor that stimulates production of sulphated GAGs and HA by fibroblasts.

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.

Melanoma cell-derived factors stimulate glycosaminoglycan synthesis by fibroblasts cultured as monolayers and within contracted collagen lattices

BACKGROUND

Various tumours exhibit glycosaminoglycan rich, and in particular hyaluronan rich matrices surrounding them that facilitate tumour growth and invasion. In many tumours, this matrix is predominantly synthesized by fibroblasts following stimulation by tumour cell-derived factors.

OBJECTIVES

To determine what effect tumour cell-conditioned medium has upon fibroblast glycosaminoglycan synthesis when cells were cultured as monolayers and within contracted collagen lattices.

METHODS

Serum-free conditioned medium from melanoma cell lines (C8161, MV3, A375 and Hs294T) was examined for its ability to stimulate the incorporation of 3H-glucosamine and 35SO4 into glycosaminoglycans synthesized by fibroblasts.

RESULTS

Conditioned medium from all four melanoma cell lines exhibited potent glycosaminoglycan-stimulating activity. In monolayer culture, C8161-conditioned medium stimulated a 4.2-fold increase in fibroblast hyaluronan, and a 9.9-fold increase in sulphated glycosaminoglycan synthesis, while 35SO4 incorporation was increased only 2.1-fold. In collagen lattice cultures, C8161-conditioned medium stimulated a 4.9-fold increase in hyaluronan synthesis, a 5.4-fold increase in sulphated glycosaminoglycans, and a 1.3-fold increase in 35SO4 incorporation.

CONCLUSIONS

Melanoma cells produce factors that are potent stimulators of fibroblast glycosaminoglycan synthesis, in both monolayer culture and within contracted collagen lattices. Synthesis of both hyaluronan and sulphated glycosaminoglycans with a reduced degree of polymer sulphation is stimulated. Such changes are likely to promote tumour cell proliferation and migration.

Evaluation of the use of tyrosinase-specific and melanA/MART-1-specific reverse transcriptase-coupled--polymerase chain reaction to detect melanoma cells in peripheral blood samples from 299 patients with malignant melanoma

BACKGROUND

There is a current need for a reliable prognostic marker for melanoma patients, particularly those with stage 2 and stage 3 disease, so that adjuvant therapies can be directed appropriately.

OBJECTIVES

To establish whether or not the use of tyrosinase-specific or melanA/MART-1-specific reverse transcriptase-coupled-polymerase chain reaction (RT--PCR) of peripheral blood cells detects preclinical disease progression in patients with malignant melanoma.

METHODS

Two hundred and ninety-nine patients with melanoma in clinical stages 1--4 were observed in this study. Samples were obtained sequentially from 153 of these patients at 4-week intervals over a period of up to 2 years and correlated with clinical evidence of disease activity. Tyrosinase and melanA/MART-1 amplicons were analysed by agarose gel electrophoresis and Southern blot hybridization subsequent to a single round of amplification.

RESULTS

We demonstrated a statistically significant increase in tyrosinase RT--PCR positivity with advancing stage of melanoma progression. The percentage tyrosinase positivity in 910 samples tested was: stage 1, 135 samples, 34% positive; stage 2, 196 samples, 51% positive; stage 3, 423 samples, 50% positive; and stage 4, 156 samples, 65% positive. The positivity rate for individual patients tested sequentially was higher if only one positive test was required to label a patient positive, at 42%, 65%, 82% and 81% for patients in stages 1--4, respectively. However, we did not find a clear pattern of conversion from negativity to positivity in patients who progressed during the study from stage 2 to stage 3 or stage 3 to stage 4, and found no clear evidence of increased positivity rates in the 6-week period following melanoma-related surgery in patients with stage 3 and 4 disease. The positivity rate for melanA/MART-1 was lower for both patients and samples, and no melanA/MART-1-positive sample was negative for tyrosinase.

CONCLUSIONS

We conclude that the presence of circulating tyrosinase-positive cells as detected by this method appears to be a discontinuous rather than a continuous phenomenon, even in patients with stage 4 disease. For this reason the assay cannot be recommended as a method of sequentially monitoring individual patients in a clinical setting.

Effect of retinoic acid on plasminogen activator expression in human melanoma cells

The plasminogen activation system comprises various proteases that contribute to the invasive potential and metastatic spread of the tumour cell. Two such proteases are tissue-type (tPA) and urokinase-type (uPA) plasminogen activators. Both these enzymes convert plasminogen into the active zymogen plasmin, which has a broad substrate specificity and is capable of degrading a wide range of extracellular matrix molecules. In this study, we examined the effect of retinoic acid (RA) on uPA and tPA secretion in the highly metastatic C8161 and the poorly metastatic Hs294T human melanoma cell lines using a specific enzyme-linked immunosorbent assay (ELISA) detection system, and correlated this production with RA receptor (RAR) expression. Over a range of dilutions, we were able to show that the highly metastatic C8161 cells secreted 0.95 ng of uPA/cell compared with 4.41 fg/cell for the Hs294T cells, whereas the Hs294T cells secreted 24.5 fg of tPA/cell compared with 4.35 fg/cell for the C8161 cells. On exposure of the cells to RA (10(-10)-10(-5) M) for 4 days, uPA secretion was increased 3.4-fold in the C8161 cell line and 1.6-fold in the Hs294T cell line using 10(-8) M RA. In addition, tPA expression was increased in both cell lines by 3.7-fold in the C8161 cells and 3.8-fold in the Hs294T cells with 10(-6) M RA treatment. Increases in PA expression by RA have been reported to involve RAR alpha and RAR beta expression. We were able to detect RAR beta and gamma expression in both cell lines, with and without RA treatment, but were unable to detect expression of RAR alpha. This suggests that another mechanism must exist to regulate the RA modulation of tPA and uPA secretion in these cell lines that does not require RAR alpha expression.

The role of human melanoma cell ICAM-1 expression on lymphokine activated killer cell-mediated lysis, and the effect of retinoic acid

Intercellular adhesion molecule (ICAM-1) exists as a membrane-associated form (mICAM-1) on the surface of tumour cells as well as a soluble form (sICAM-1). This study analyses the ability of all-trans retinoic acid (RA) to alter both sICAM and mICAM-1 expression in C8161 and Hs294T human melanoma cell lines and investigates the involvement of ICAM-1 in the interaction between tumour and lymphokine-activated killer (LAK) cells using the Cr-51 release assay. Our data showed that 4-day pretreatment of the tumour cells with 10(-7) M RA and 10(-6) M RA induced an increase in lysis of both cell lines and also increased mICAM-1 expression without having any effect on sICAM-1 levels. Addition of blocking ICAM-1 antibody (10 microg ml(-1)) to the C8161 cells at an effector:tumour cell ratio of 40:1 caused a 2.3-fold reduction in lysis of tumour cells and a 3-fold reduction in lysis of RA-treated cells. Blocking ICAM-1 antibody at optimum concentrations of 5 microg ml(-1) reduced lysis 1.8-fold in control Hs294T cells and 1.3-fold in RA-treated cells. Blocking the HLA-ABC complex had no effect on lysis. The more highly metastatic C8161 cells were found to secrete 4-fold greater levels of sICAM-1 than the poorly metastatic Hs294T cells and addition of sICAM-1 to the assay failed to affect lysis of either cell line but did induce a 2-fold decrease in lysis of RA-treated C8161 cells. Collectively, these data provide further evidence for ICAM-1 involvement in the tumour/LAK cell response and indicates that the RA-induced increase in mICAM-1 levels are partly responsible for the increase in susceptibility of the tumour cells. sICAM-1 appears to be unimportant in evasion of the tumour cells from LAK cell lysis, but may play a role in evasion of RA-treated C8161 cells.

Melanoma cell-derived factor stimulation of fibroblast glycosaminoglycan synthesis--the role of platelet-derived growth factor

The hyaluronan-rich matrix surrounding many tumours may facilitate tumour growth, invasion and angiogenesis, with the majority of this hyaluronan apparently being synthesised by normal fibroblasts, stimulated to do so by tumour cell-derived factors. Melanoma cell-conditioned medium (CM) stimulates up to a 6-fold increase in fibroblast glycosaminoglycan (GAG) synthesis, with the active factors being present in tumour CM ultrafiltration fractions > 30 kDa and < 1 kDa. These fractions are poorly active individually, but when recombined, the activity is substantially greater than the additive effect. The objective of this study was to identify the factors present in the ultrafiltration fraction > 30 kDa that produce a greater than additive effect with the fraction < 1 kDa in stimulating the incorporation of 3H glucosamine into fibroblast GAGs. A number of factors including basic fibroblast growth factor (bFGF), interleukin (IL)-1 beta, pleiotrophin, platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-beta), tumour necrosis factor-alpha (TNF-alpha) and vascular endothelial growth factor (VEGF) failed to stimulate any significant increase in GAG synthesis, but when added to the < 1 kDa tumour CM fraction, both PDGF and to a lesser extent, bFGF, exhibited potent stimulating activities. Neutralising antibodies to PDGF and bFGF added to the melanoma CM decreased the fibroblast GAG-stimulating activity by 29% and 40%, respectively, in C8161 melanoma CM and by 47% and 45%, respectively, in Hs294T melanoma CM. The activities of PDGF-AA and PDGF-BB isoforms were indistinguishable, suggesting the PDGF-alpha receptor plays a role in the GAG-stimulatory response. Western analysis following treatment with PDGF, bFGF or melanoma CM revealed banding patterns for PDGF and melanoma CM that were similar. Immunoprecipitation of the PDGF-alpha receptor revealed it to be phosphorylated in fibroblasts treated with PDGF and melanoma CM, but not with control fibroblast CM. These studies suggest that PDGF plays an important role in the GAG-stimulating activity of the melanoma CM, but requires the presence of an as yet unidentified novel low molecular weight factor for full activity.

Pentoxifylline-induced modulation of melanoma cell growth, adhesion and lymphokine activated killer cell-mediated lysis

Pentoxifylline (PX) is a phosphodiesterase inhibitor which effectively increases overall cAMP levels within the cell. This study analyses the ability of PX to alter growth, adhesion and lymphokine activated killer (LAK) cell-mediated lysis of the C8161 and Hs294T human melanoma cell lines, and investigates the role of intercellular adhesion molecule-1 (ICAM-1) in the tumour/LAK cell interaction. We have demonstrated that 4 days' pretreatment with PX (100-250 microg/ml) significantly reduces cell numbers in a dose- and time-dependent manner, with cell numbers decreasing by 67.5% in the C8161 cell line and by 65.4% in the Hs294T cell line with 250 microg/ml PX. Adherence of both cell lines to a range of extracellular matrix components is not affected by PX, with the exception of the C8161 cells, where 4 days' pretreatment with 250 microg/ml PX causes a 24.2% reduction in adherence to fibronectin. Four days' pretreatment of the tumour cells with 250 microg/ml PX leads to increased lysis of the C8161 cells and decreased lysis of the Hs294T cells. The addition of blocking ICAM-1 antibody (10 microg/ml) to the C8161 cells at an effector:tumour cell ratio of 40:1 causes a 2.3-fold reduction in lysis of both control and PX-treated cells. Addition of blocking ICAM-1 antibody (5 microg/ml) to Hs294T cells reduces lysis of control cells 1.8-fold. In PX-treated Hs294T cells, 10 microg/ml of blocking ICAM-1 antibody significantly reduces lysis 1.5-fold. The more aggressive C8161 cells produce 5-fold greater levels of soluble ICAM-1 (sICAM-1) than the poorly metastatic Hs294T cells. PX (10-250 microg/ml) causes a dose-dependent increase in sICAM-1 expression in both cell lines, with maximum increases of 4.7-fold and 4.3-fold in the Hs294T and C8161 cell lines, respectively, following 4 days' pretreatment with 250 microg/ml PX. Collectively, these data demonstrate the ability of PX to alter tumour cell growth, adhesion and LAK cell-mediated lysis and also support a role for the involvement of ICAM-1 in the tumour/LAK cell interaction.

Colonization of living skin equivalents by Malassezia furfur

Initial colonization events and yeast-hyphal transformation by Malassezia furfur were observed using living skin equivalent (LSE) models for growth. Yeast cells were inoculated onto the LSEs which were incubated in CO2-independent media at 37 degreesC for variable lengths of time. Assessment of fungal growth and invasion was by light- and scanning electron microscopy (SEM). Viability counts of M. furfur were determined by a method of washing and serial dilution. Yeast cells had retained their viability and increased in number approximately twofold over a 4-day period of incubation. Yeast-to-hyphal transition was not achieved in this model. Random destruction of the uppermost layers of the stratum corneum was observed in the presence of M. furfur. LSEs therefore appear to be a promising model for mechanisms of growth of cutaneous organisms.

Effect of retinoic acid on melanoma cell-derived factor stimulation of fibroblast glycosaminoglycan synthesis

The hyaluronan-rich matrix that surrounds many tumours and facilitates tumour cell growth and invasion is thought to be predominantly synthesized by normal stromal cells stimulated by tumour cell-derived factors. This study examines the possibility that the production of tumour cell-derived factors that stimulate fibroblast glycosaminoglycan (GAG) synthesis may be blocked by exposure to differentiation-inducing agents such as retinoic acid. We have demonstrated that Hs294T, C8161 and A375 human melanoma cell lines release factors into their medium that stimulate normal fibroblast GAG synthesis. Exposure of these melanoma cells to retinoic acid failed to mediate any significant reduction in growth over a 7-day period. Retinoic acid failed to block the tumour cell production of GAG-stimulating activities and even enhanced the activities produced by the C8161 cell line, particularly at low retinoic acid concentrations (48% stimulation at 10(-9) M retinoic acid; P < 0.02). Addition of retinoic acid directly to fibroblast cultures exposed to fibroblast-conditioned medium resulted in an inhibition of GAG synthesis with a 33% inhibition observed at 10(-5) M. Addition of retinoic acid to fibroblast cultures exposed to the tumour cell-conditioned medium failed to inhibit the stimulation of GAG synthesis. Other differentiation-inducing agents, such as hexamethylene-bis-acetamide and butyrate, also failed to block the production of tumour cell-derived GAG-stimulating activities. These results demonstrate that retinoic acid and other differentiation-inducing agents fail to inhibit melanoma cell production of fibroblast GAG synthesis-stimulating factors or their action upon fibroblasts.

Partial characterisation of human melanoma cell-derived factors that stimulate fibroblast glycosaminoglycan synthesis

Glycosaminoglycans (GAGs), and in particular hyaluronan, are known to play a role in tumour cell migration, invasion and metastasis. Conditioned medium from two human metastatic melanoma cell lines (Hs294T and C8161) shows potent fibroblast GAG-synthesis-stimulating activities which are active in fibroblast cultures derived from different anatomical sites. This ability is not specific to melanoma cells and is observed in several carcinoma cell lines. Initial characterisation studies have demonstrated that the GAG-stimulating activities in the medium conditioned with melanoma cells show a degree of heat and trypsin resistance. Fractionation of the conditioned medium with Amicon ultrafiltration membranes of various molecular weight cut-offs, ranging from 1 to 30 kD, resulted in a total loss of activity. Activity could be regained by recombination of the concentrated fraction with the filtrate, suggesting more than one factor to be involved in GAG stimulation, with a degree of interdependence between the individual fractions. The fraction greater than 30 kD and that less than 1 kD appear to contain the majority of the GAG-stimulating activity.

Effects of retinoids on glycosaminoglycan synthesis by human skin fibroblasts grown as monolayers and within contracted collagen lattices

Fibroblasts grown within contracted collagen lattices synthesize substantially less glycosaminoglycans than fibroblasts grown as monolayers on a plastic substrate. [3H]glucosamine incorporation into hyaluronate was reduced by 70%, and incorporation into sulphated glycosaminoglycans was reduced by 40%. However, incorporation into heparan sulphate and chondroitin sulphates was reduced by 14 and 49%, respectively, resulting in a substantial change in the proportions of the individual glycosaminoglycans. On the basis of [3H]glucosamine incorporation, hyaluronate constituted 80% of the total glycosaminoglycans synthesized in monolayer cultures, but only 67% in collagen lattice cultures. Incorporation of 35SO4 into chondroitin sulphates was reduced by 22%, whereas no change was observed in heparan sulphates following culture within collagen lattices. Exposure of the fibroblast cultures to retinoic acid (10(-6) mol/l) and retinyl propionate (2 x 10(-6) mol/l) resulted in a decrease in the incorporation of [3H]glucosamine into hyaluronate by up to 41% in monolayer cultures, and 25% in collagen lattice cultures. The retinoids stimulated the incorporation of [3H]glucosamine into heparan sulphate by up to 72%, and chondroitin sulphates by up to 30%, whereas 35SO4 incorporation remained essentially unaltered. Only modest changes in the incorporation of both isotopes into fibroblast sulphated glycosaminoglycans were observed following exposure to the retinoids in lattice cultures. Q-Sepharose ion-exchange chromatography at pH 2.0 revealed that there was no change in the degree of polymer sulphation of either chondroitin sulphate or heparan sulphate isolated from collagen lattice cultures compared with monolayer cultures. Retinoic acid (10(-6) mol/l) treatment did, however, reduce the degree of polymer sulphation of heparan sulphates and chondroitin sulphates in both monolayer and lattice cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Activity of terbinafine on Trichophyton mentagrophytes in a human living skin equivalent model

Germination of arthroconidia of Trichophyton mentagrophytes in the presence of the allylamine antifungal terbinafine was assessed utilizing a human living skin equivalent model. Arthroconidia were inoculated onto the skin-equivalent previously exposed to low concentrations of terbinafine (0.01-1.0 mg l-1) and then incubated at 28 degrees C for 7 days. An assessment of fungal growth inhibition was made by light and scanning electron microscopy. In the absence of terbinafine, adherence, germination and hyphal extension were observed. Penetration of the model was seen, with hyphae present in the dermal component. In the presence of terbinafine, inhibition of fungal growth was apparent and the drug was seen to act as a barrier against fungal invasion of the dermis. The data indicate that the living skin equivalent model is a promising in vitro system for evaluating new antifungal agents.

Integrins and other adhesion molecules involved in melanocytic tumor progression

Recent investigations have reported changes in the expression of cell surface adhesion molecules associated with melanoma progression from in situ to invasive to metastatic tumors, including the upregulation of the integrins alpha v beta 3, alpha 3 beta 1, alpha 4 beta 1, and alpha 5 beta 1, downregulation of alpha 6 beta 1, and enhanced expression of intercellular adhesion molecule-1, MUC18, and CD44. Current research is now focused on the function of these adhesion molecules in facilitating melanoma invasion, metastasis and evasion of lysis by effector cells, and the mechanisms involved in controlling the adhesion molecule activation state and signal transduction.

Cell-cell and cell-extracellular matrix interactions during melanoma cell invasion and metastasis

Although great advances have been made in recent years in understanding the interactions between tumour cells and their environment, we still do not fully understand the complex mechanisms involved in the steps by which in situ malignancy becomes invasive and then metastatic. To complete the various steps of the pathway to metastatic malignancy, melanoma cells have acquired the ability to grow in the absence of certain growth factors while producing autocrine factors. They are also able to modulate the extracellular matrix and express an array of adhesion molecules enabling them to interact with various cell types and extracellular matrix molecules during the establishment of secondary tumours.

Human melanoma cell-derived factor(s) stimulate fibroblast glycosaminoglycan synthesis

Conditioned media from cultures of human metastatic Hs294T melanoma cells contain a factor/factors that promote(s) fibroblast-mediated contraction of collagen lattices, and stimulate(s) fibroblast glycosaminoglycan (GAG) synthesis. Complete medium from melanoma cell cultures stimulated fibroblast hyaluronate synthesis 9.3-fold, and sulphated GAG synthesis 2.6-fold, as measured by 3H-glucosamine incorporation. 35SO4 incorporation into sulphated GAGS was essentially unaltered, the net result being a decrease in the degree of sulphation. Fibroblasts synthesized hyaluronate with an increased molecular weight when grown in the presence of the melanoma-cell culture medium, while the molecular weights of heparan and chondroitin sulphates remained essentially unaltered. Our results indicate that the tumour-cell-derived factor(s) stimulate(s) changes in fibroblast glycosaminoglycan synthesis, and that these changes may facilitate tumour cell invasion in vivo.

Retinoic acid-induced inhibition of metastatic melanoma cell lung colonization and adhesion to endothelium and subendothelial extracellular matrix

The effect of pretreatment of metastatic B16 melanoma cells with 10(-6) M all trans-retinoic acid resulted in a significant inhibition of lung colonization following injection of 10(5) cells into the tail vein of syngeneic C57BL mice. Adhesion of melanoma cells to vascular endothelial cell monolayers, and subendothelial extracellular matrix was also inhibited by pretreatment with retinoic acid, as was tumour cell aggregation following seeding of pretreated cells on to 0.5% agar. Release of 35SO4 from radiolabelled subendothelial extracellular matrix by melanoma cells was essentially unaltered by retinoic acid pretreatment, as was the release of radiolabel from [3H]proline-labelled matrix, while plasminogen activator activity was enhanced in retinoic-acid-treated cells. These observed changes in adhesive properties may be responsible, at least in part, for the retinoic-acid-induced inhibition of lung colonization.

Pentoxifylline enhances lung colonization and alters cell adhesion and glycosaminoglycan synthesis by metastatic B16 melanoma cells

The effect of pentoxifylline on B16 melanoma cell lung colonization, synthesis and properties of glycosaminoglycans (GAGS), and adhesion to and degradation of subendothelial extracellular matrix was examined. Pentoxifylline inhibited cell growth, cell numbers being reduced by 50% following incubation for 4 days in the presence of 250 micrograms/ml pentoxifylline, while the treated cells appeared more flattened, possessed numerous but short dendritic processes, and exhibited greatly enhanced tyrosinase activity and melanin synthesis. Pentoxifylline treatment increased the cells' ability to colonize the lungs of syngeneic C57BL mice following tail-vein injection of 10(5) cells. The number of lung tumours increased from 16.7 +/- 6.1 to 52.2 +/- 17.8. In addition, pentoxifylline-treated cell GAG synthesis was reduced by 36%, and the charge density of chondroitin sulphate reduced, while tumour-cell aggregation and adhesion to subendothelial extracellular matrix was increased, as was the tumour-cell-mediated release of 35SO4 from radiolabelled subendothelial matrix. The observed changes in GAG synthesis may contribute toward the increased cell adhesiveness which, in addition to increased degradation of certain components of the subendothelial extracellular matrix, may account, at least in part, for the enhancement of lung colonization.

Retinoic acid-induced inhibition of lung colonization and changes in the synthesis and properties of glycosaminoglycans of metastatic B16 melanoma cells

The effect of all-trans retinoic acid on metastatic B16 melanoma lung colonization and synthesis and properties of glycosaminoglycans was examined. Injection of tumour cells, pretreated with 10(−6) M-retinoic acid or grown to low density, into the tail vein of syngeneic C57 mice produced significantly fewer pulmonary tumours compared to subconfluent control cells. By cochromatography of glycosaminoglycans isolated from control ([14C]glucosamine-labelled) and 10(−6) M-retinoic acid-treated ([3H]glucosamine-labelled) cells on DEAE ion-exchange columns, differences in elution profiles were detected. Chondroitin sulphates isolated from retinoic acid-treated cells eluted at a lower salt concentration than those from control cells, while retinoic acid-treated cells synthesised heparan sulphates of a higher charge density than heparans from control cultures. These changes were apparent in both medium and trypsin-releasable fractions. Retinoic acid-treated cultures were seeded so that they were of a similar density to control cultures when harvested, as cell density was shown to affect glycosaminoglycan synthesis, the glycosaminoglycans from low-density cultures having similar properties to those isolated from retinoic acid-treated cultures. Retinoic acid treatment also reduced the overall synthesis of glycosaminoglycans while having little effect on the composition or distribution between medium, trypsin-releasable and cell-associated fractions. These observed changes in glycosaminoglycans may, in part, be responsible for retinoic acid-induced inhibition of lung colonization, and reduced adhesion to basement membrane components, which we have previously demonstrated.

Modulation of melanoma cell adhesion to basement membrane components by retinoic acid

The effect of retinoic acid pretreatment on metastatic B16 melanoma cell adhesion in serum-free medium to tissue culture plastic precoated with fibronectin, laminin/nidogen, type I and type IV collagen was examined. Both control cells grown to subconfluence and cells treated with 10(−6) M-retinoic acid adhered and spread rapidly on fibronectin (greater than 75% following 1 h of incubation) but adhered poorly to type I collagen (less than 15%). Control cells adhered to laminin/nidogen (greater than 35%), type IV collagen (greater than 58%) and type IV collagen plus laminin/nidogen (greater than 80%), while retinoic acid-treated cells showed a reduced ability to attach and spread on these substrata, the number of adherent cells being reduced by 61% on laminin/nidogen, by 19% on type IV collagen, and by 41% on type IV collagen plus laminin/nidogen following 1 h of incubation. The minimum concentration of retinoic acid required to yield an effective reduction in adhesion was 10(−7) M for type IV collagen and 10(−10) M for laminin/nidogen. Melanoma cells harvested at low density showed a reduced adhesion to laminin/nidogen and type IV collagen compared to that of subconfluent control cultures, but also showed a reduced adhesion to fibronectin. The effect of retinoic acid on cell adhesion was not, however, due to reduced cell density, as the cells were seeded so that control and retinoic acid-treated cultures were of a similar density when harvested.

Different susceptibilities of melanoma cells to retinoic acid-induced changes in melanotic expression

The effect of retinoic acid on murine B16 melanoma cell growth, tyrosinase activity and melanin synthesis was investigated. Retinoic acid inhibited the growth of B16F1, B16F10 and B16BL6 melanoma cells, but enhanced melanin synthesis only in the B16F1 cells. The B16F10 and B16BL6 cells exhibited retinoic acid-induced suppression of tyrosinase activity and melanin synthesis, which was most apparent in the B16F10 cell variant. For comparison, Cloudman S91 melanoma cells proved to be particularly sensitive to retinoic acid-induced growth inhibition and stimulation of the expression of their melanotic phenotype. These results suggest considerable heterogeneity in the B16 melanoma with respect to their response to retinoic acid.

Ascorbate induced changes in glycosaminoglycan synthesis and distribution of normal and SV40-transformed fibroblasts

The effect of ascorbate on the glycosaminoglycans synthesized by normal and simian virus 40(SV40)-transformed human skin fibroblasts was examined. Cells were incubated in the presence or absence of ascorbate, and radiolabelled with [3H]glucosamine and [35S]sulphate for 48 h, 3 days after reaching confluence. Glycosaminoglycans were analysed in the medium, a collagenase extract, and in the trypsin/cell-associated fraction. Hyaluronic acid was the main 3H-labelled glycosaminoglycan in all but the collagenase extracts, and showed a large decrease in normal fibroblast cultures, but a significant increase in SV40-transformed fibroblast cultures following feeding with ascorbate. Incorporation of [3H]glucosamine into sulphated glycosaminoglycans was reduced in normal fibroblast cultures but increased slightly in SV40-transformed cultures following ascorbate supplementation. [35S]sulphate incorporation remained essentially unaltered in both cell cultures. Ascorbate stimulated the deposition of glycosaminoglycans into the insoluble matrix of normal fibroblasts while reducing the deposition in SV40-transformed fibroblast cultures. The observed changes may in part be related to ascorbate-induced deposition of collagen in normal fibroblast cultures and the inability of the transformed fibroblast cells to deposit an extensive extracellular matrix, in addition to possible changes in the specific activity of the UDP-N-acetyl-[3H]hexosamine pool.

Changes in the synthesis, distribution and sulphation of glycosaminoglycans of cultured human skin fibroblasts upon ascorbate feeding

The effect of ascorbic acid on the synthesis, distribution and sulphation of glycosaminoglycans by human skin fibroblasts has been examined. Medium was supplemented with ascorbate over several days, and cultures incubated with [3H]glucosamine and Na2(35)SO4 for 48 h, followed by analysis of the glycosaminoglycans in the medium, in collagenase and trypsin extracts, and in cell fractions. Ascorbate feeding resulted in a reduction in hyaluronate synthesis, which was the main 3H-labelled component and was distributed mainly in the medium fractions. Sulphated glycosaminoglycans showed a reduction in incorporation of 3H label, but increased sulphation following ascorbate feeding. In control cultures 53% of 3H-labelled sulphated glycosaminoglycans and 63% of 35S-labelled glycosaminoglycans were present in the medium fraction, while in ascorbate-fed cultures, 41% of 3H label and 38% 35S label were incorporated into medium-sulphated glycosaminoglycans. Ascorbate also caused an increase in cell density and in collagen production and deposition.

An in vitro cytotoxicity study of aldehyde-treated pig dermal collagen

The cytotoxicity of aldehyde-treated collagen was assayed by measuring 3H-thymidine incorporation in adult human skin fibroblasts grown in tissue culture for 1 or 3 days in the presence of pig dermal collagen cross-linked with formaldehyde or glutaraldehyde. A comparison was also made with collagen preparations washed for 2 weeks either at 15 degrees throughout or partly at 15 degrees and partly at 37 degrees. Collagen treated with both formaldehyde and glutaraldehyde proved increasingly toxic with increase in the concentrations of aldehyde used. While the maximum toxic effect was observed after 1 day culture in formaldehyde-treated collagen, with thymidine uptake ranging from 4-48% of control values with 5-0.1% formaldehyde and a 15 degrees wash, the toxic effect of glutaraldehyde treatment increased with longer exposure and at 3 days thymidine uptake ranged from 3-40% of control values with 0.05-0.001% glutaraldehyde and washing at 15 degrees. Washing partly at 37 degrees significantly reduced toxicity, the differences in thymidine uptake as compared with washing at 15 degrees alone ranging from 34-50% with 1 and 0.3% formaldehyde respectively in 1 day cultures and from 14-37% with 0.02 and 0.005% glutaraldehyde in 3 day cultures. While fibroblasts actively grew and migrated when seeded on non-cross-linked collagen, only limited cell survival occurred on aldehyde-treated collagen.

Sulphated glycosaminoglycans in regenerating rat liver

The total weight percentage glycosaminoglycan content of rat liber was found to increase by 50% in the first 30 h after partial hepatectomy. The content returned to near normal by the third day, but then increased again to a second maximum at 5-6 days, only to gradually decline to normal by the ninth day, when regeneration was nearly complete. This biphasic pattern was most marked in the chondroitin sulphate A/C component, with a 6-fold increase by the sixth day. Dermatan sulphate showed the same temporal trend, whereas heparan sulphate remained relatively unaltered. No such changes were detected in the livers of rats subjected to sham operation. The possible molecular mechanisms underlying the apparent link between cellular glycosaminoglycan content and proliferative tendency are discussed.

Purification of some glycoside hydrolases by affinity chromatography

Two glycoproteins have been isolated from the cell walls of baker's yeast. One is a glucan-protein complex which has been partially characterised as having a branched carbohydrate structure composed of chains of (1 leads to 3)-linked beta-D-glucosyl residues, some of which are attached by (1 leads to 6)-linkages to the main chain. Immobilization of this glycoprotein was achieved by covalent attachment to Sepharose, and the product was used to isolate a number of (1 leads to 3)-beta-D-glucan hydrolases from Helix pomatia, malted barley, and Basidiomycete QM806. The second glycoprotein, a mannan-protein complex, after immobilization, has been used in the purification of an alpha-D-mannosidase from jack-bean meal.