Microvascular expression of MALA-2 correlates with in vivo lymphocyte trafficking and is preferentially enhanced in tumors by tumor necrosis factor-alpha and interleukin-1 alpha

The role of endothelial cell adhesion molecule expression in the immune response to tumors is unknown. We have investigated the expression of murine lymphocyte activation antigen (MALA-2), the murine equivalent of intercellular adhesion molecule-1 (ICAM-1), in blood vessels of normal murine tissues and in melanoma tumors and evaluated the relationship between MALA-2 expression and lymphocyte trafficking in vivo. C3H/HeN mice were injected both i.p. and s.c. with a clone of K-1735 syngeneic melanoma cells. Day 11 tumor-bearing mice were killed and vascular expression of MALA-2 was quantified using immunohistochemistry. MALA-2 expression was high in lung, liver and spleen and low in lymph node, small bowel, muscle and tumor. Systemic administration of either recombinant tumor necrosis factor alpha (rTNF alpha) or recombinant interleukin-1 alpha (rIL-1 alpha) over 2 days prior to organ harvest resulted in an increase in the number of tumor vessels expressing MALA-2, with no change in MALA-2 expression in other tissues. In vivo lymphocyte trafficking was evaluated using cultured, activated splenocytes radiolabeled with 111In. 111In-labeled splenocyte distribution correlated closely with MALA-2 expression, with high localization to spleen, liver and lung and poor localization to lymph node, small bowel, muscle and tumor. Systemic administration of rTNF alpha, but not rIL-1 alpha, resulted in a significant increase in 111In-labeled splenocyte distribution to tumor, but neither rTNF alpha nor IL-1 alpha altered 111In-labeled splenocyte distribution to normal organs. Our data demonstrate the in vivo pattern of vascular MALA-2 expression in normal murine tissues and tumors and suggest that the expression of MALA-2 can be preferentially enhanced in tumors by systemic administration of cytokines. Lymphocyte distribution in vivo correlates closely with the pattern of MALA-2 expression, and these data support the conclusion that MALA-2 plays an important role in the regulation of lymphocyte trafficking.

Different sensitivities of the murine melanomas BL-6 and BL-6-beta m to local injections of interleukin-2 (IL-2). Analysis of gangliosides after the treatment

The murine melanoma cell line BL-6-beta m, which is a stable cell line transfected with a gene coding a unique actin subspecies called beta m to the BL-6 cell line, has low metastatic potentials as compared with those of the parent cell line. BL-6-beta m melanomas were found to be sensitive to in vivo local injection of IL-2, while BL-6 melanomas showed almost no response. Ganglioside analysis of BL-6 and BL-6-beta melanomas revealed that the main ganglioside of both melanomas was GM3, which suggested that different sensitivities between BL-6 and BL-6-beta m melanomas to the injection of IL-2 did not relate to the different compositions of main gangliosides. However, minor components of the gangliosides such as GM2 and GM1 emerged only in BL-6-beta m melanomas after treatment with IL-2. Local injection of IL-2 caused considerable infiltration of anti-asialo GM1-positive cells into the nests as well as the interstitials of BL-6-beta m melanomas. In contrast, in the BL-6 melanomas treated with IL-2, infiltration of the anti-asialo GM1-positive cells was hardly seen, although anti-Thy1,2 and anti-macrophage-positive cells were found to more or less the same extent as observed in BL-6-beta m melanomas. These results suggest that the murine metastatic variant melanoma cell lines BL-6 and BL-6-beta m have different properties in terms of sensitivity to in vivo IL-2 treatment, and a slight enhancement of the ganglioside components GM2 and GM1 expression only in BL-6-beta m after IL-2 treatment may play a role in the IL-2-mediated attraction of immune cells or may explain the different sensitivities of the two lines to treatment with IL-2.

Characterization and tumorigenicity of spheroids composed of pigmented or non pigmented B16 melanoma cells

A parental line of mouse B16 melanoma cells (B16) and two derived cloned lines, either pigmented (B16P) or non pigmented (B16NP), were cultured in vitro as spheroids. After 48 hrs, the pigmented cells (B16, B16P) formed smaller and looser aggregates, with higher rates of cell proliferation and lower amounts of extracellular matrix as compared to B16NP spheroids. The three lines were more tumorigenic when inoculated subcutaneously as spheroids than as isolated cells. Furthermore, B16P or B16 spheroids developed richly vascularized subcutaneous tumors and metastases more rapidly than B16NP aggregates. After intravenous injection of spheroids, the measurement with an image analyzer of the area of sections in lung colonies indicated that B16P colonies were larger and more numerous than those induced by B16NP cells.

Basal metallothionein in tumors: widespread presence of apoprotein

A survey has been conducted of solid and ascites tumors from mice and solid tumors in rats for the presence of metallothionein or metallothionein-like protein. In most tumors, a positive identification was made on the basis of Sephadex G-75 and HPLC-DEAE chromatography followed by competitive radioimmunoassay for metallothionein. Apometallothionein was revealed in a number of tumors for the first time by comparing the Sephadex G-75 chromatographic profiles of Zn in native cytosol and Cd in cytosol incubated briefly with CdCl2 to saturate free binding sites on the protein before Sephadex G-75 chromatography. In two cases unsaturation of metallothionein was correlated with a lack of zinc in the ascites fluid which supplies the tumor with zinc.

LZIP-1 and LZIP-2: two novel members of the bZIP family

A large family of bZIP proteins, containing a basic DNA-binding domain and a leucine zipper, have been described that recognize the CRE and AP-1 elements. Here, we have identified two new members, designated LZIP-1 and LZIP-2. The murine cDNA for LZIP-1 coded for a 379-amino-acid (aa) residue protein containing several distinct domains, including a Ser-rich region, a basic DNA-binding region, and an unusually long leucine zipper. A second form, LZIP-2, contained an additional 25 aa in the N-terminal region. Western immunoblotting revealed that antibody raised against part of recombinant LZIP-1 detected both forms in a variety of tissues. Gel mobility shift assays demonstrated that the recombinant protein possessed specific DNA-binding activity for both the CRE AP-1 sites. The present identification of two more ubiquitous members of the bZIP family emphasizes the complex nature of transcription factor interactions at the CRE and AP-1 sites.

Protoporphyrin biosynthesis in melanoma B16 cells stimulated by 5-aminolevulinic acid and chemical inducers: characterization of photodynamic inactivation

The stimulation of protoporphyrin (PP) biosynthesis in B16 melanoma cells in order to facilitate photodynamic cell killing was studied. Biosynthesis and accumulation of PP in the melanoma cells was increased from 8 to 15 pmol/mg protein by the use of dimethyl-sulfoxide (DMSO), a differentiation-inducer. Treatment of the cells with the porphyrogenic agent allylisopropyl-acetamide (AIA) stimulated an additional PP increase. The most remarkable enhancement of intracellular PP was achieved by the supplementation of 5-aminolevulinic acid (5-ALA) to the growth medium following the addition of DMSO and AIA during the induction phase. The intracellular concentration of PP exceeded 21,950 pmol/mg protein following combined stimulation by DMSO/AIA and 5-ALA. The porphyrins produced in the incubated cells, in serum-depleted medium, consisted of 95% PP; 88% of it was recovered from the cells and only 7% was excreted into the medium. Photosensitization of the B16 melanoma cells containing high PP concentrations was effective even at low light doses. Potassium (K) efflux was the first measurable sign of cell damage determined by X-ray microanalysis (XRMA) following fast liquid-nitrogen fixation. During a 1 min interval, 70% of cellular K was lost. After 5 min illumination, complete cell destruction was detected by scanning electron microscopy (SEM) and XRMA. The photodamaged cells showed influx of Na, Cl and Ca ions accompanying the immediate K losses. Ultrastructural cell damage was manifested by disintegration of the outer membrane. Total cell death of B16 melanoma cells was achieved by chemical induction of endogenous PP and photosensitization.

A pH- and temperature-dependent cycling method that doubles the yield of microtubule protein

This report describes a procedure for the isolation of microtubules (MTs) and microtubule-associated proteins from mammalian cultured cells and tissues. This method relies on the discovery that the solubility of brain tubulin is pH-sensitive. In this report, we examined tubulin solubility over a broad pH range and discovered that the amount of soluble tubulin increased by 240% as the pH was raised from 6.0 to 8.0. Quantitative immunoblotting revealed that there was an almost equal partitioning of tyrosinated and acetylated alpha-tubulin isotypes at the higher pH. These observations were incorporated into a new procedure for the purification of microtubule protein (MTP) from bovine brain and mouse B16 cultured melanoma cells. Morphologically, and in terms of polypeptide composition, this MTP is indistinguishable from that prepared by a glycerol-cycling method (21). Moreover, our new method of pH- and temperature-cycling yields almost twice as much MTP as that obtained by other cycling methods.

Metastatic behavior and tumorigenicity of a human melanoma cell line (MM-RU) after injection into nude mice

The ability of the human amelanotic melanoma cell line MM-RU to produce experimental metastases and to grow tumors at subcutaneous inoculation sites in 4-week-old nude mice was examined. After i.v. inoculation of 10(6) cells, all injected mice (n = 21) developed consistent numbers of metastatic pulmonary colonies within 32 days. The coefficients of variation for the number of colonies were between 17%-23% in three independent experiments. Survival time after i.v. inoculation was 63 +/- 7 days (mean +/- SD) (n = 20). Within 20 days, subcutaneous inoculation of 5 x 10(6) cells resulted in tumor growths of 13 +/- 3 mm (mean +/- SD) at the inoculation sites in all nude mice (n = 12). The MM-RU cell line seems to be a simple, fast vehicle for testing the effect of melanoma growth modulators on experimental pulmonary metastases as well as on subcutaneously growing melanoma.

In vivo antimelanoma effects of 4-S-cysteaminylphenol, a newly synthesized therapeutic agent specific to melanoma

Antimelanoma effects of 4-S-cysteaminylphenol (4-S-CAP), which is a newly synthesized melanin precursor, as a chemotherapeutic agent specific to malignant melanoma were determined in an in vivo system using mouse B16 melanoma. The intraperitoneal injection of 4-S-CAP induced a slight delay in the growth period of subcutaneous melanoma of C57BL/6 mice. Survival times of mice after treatment with 4-S-CAP were a little longer than those of control mice (P < 0.05), although all mice died from the local growth of tumours. The viable cell ratio of in vivo subcutaneous tumour cells reduced to 52.8% within 24 h after treatment with 4-S-CAP, but the ratio had recovered to the control level 72 h after treatment (> 90%). Similarly, the proliferating-cell-nuclear-antigen-positive cell ratio of melanotic melanoma had reduced 24 h after treatment and recovered within 72 h after treatment, while 4-S-CAP had no effect on amelanotic tumours. The formation of lung colonies by intravenous inoculation of malignant melanoma cells was compared between mice with intraperitoneal injection of 4-S-CAP and phosphate-buffered saline only. The 4-S-CAP-treated mice had significantly fewer lung colonies compared with the control mice (P < 0.01). The results indicate that the agent, 4-S-CAP, would have a therapeutic effect on malignant melanoma for a short time in vivo and therefore the agent can be effective against a small number of tumour cells, such as lung colonies, although it had little effect on the local tumours.

Identification of a mammalian melanosomal matrix glycoprotein

Antiserum raised in rabbits against the Triton X-100 insoluble fraction of melanosomes from mouse melanoma cells specifically decorates the internal matrix of melanosomes in immunoelectron microscopy. In metabolic labeling studies, the antiserum recognizes a protein of 94 kDa, which is processed to a band of 53 kDa. Whereas the precursor is relatively soluble in buffers containing Triton X-100, the processed protein requires the addition of sodium dodecyl sulfate for effective solubilization, as would be expected for a melanosomal matrix constituent. Tunicamycin reduces the Mr of the nascent protein to 75 kDa, but deoxymannojirimycin and swainsonine have no effect, suggesting that following initial glycosylation in the endoplasmic reticulum, the protein is not subject to processing by glycosidases in the Golgi apparatus or may bypass it entirely. Subcellular fractionation followed by immunoblotting confirms that the protein is present in the melanosome-rich, large granule fraction. Expression of the protein is regulated differently from that of the tyrosinase-related protein family. Conditions that greatly stimulate expression of tyrosinase-related proteins do not affect matrix protein expression, nor is the protein immunologically related to the tyrosinase-related protein family. Our results suggest that we have identified an authentic component of the mammalian melanosomal matrix, and that its characteristics lend support to a bipartite pathway for melanosomal biogenesis.

Thrombin increases the metastatic potential of tumor cells

Initial arrest of tumor cells in the microvasculature and their attachment to the endothelium and subendothelial matrix (SEM) are essential prerequisites for metastasis to occur. Factors mediating these interactions are viewed as important determinants of the tumor-cell metastatic phenotype. In this work we have studied the effects of thrombin, its analogs and its precursors on the adhesive properties and metastatic potential of tumor cells. We show that alpha-thrombin, the native form of the key coagulation enzyme, is capable of enhancing tumor-cell adhesion to both the endothelium and SEM components represented by fibronectin. Subclotting, physiological concentrations of alpha-thrombin produced a 2- to 5-fold increase in tumor-cell adhesion. A bell-shaped dose-response curve was observed, with maximal effect at 0.1 U/ml. Maximum effect occurred when cells were exposed to the agonist for 15 min and exposure for up to 4 hr resulted in enhanced tumor-cell adhesion. Prolonged incubation with thrombin resulted in a decline in the thrombin-enhanced adhesion which reached unstimulated control levels by 24 hr. Thrombin precursors and active-site-inhibited thrombin analogs only had minimal adhesion-enhancing activity; nitro- and exosite-alpha-thrombin, which retain a functional active site, mimicked, although to a lesser degree, the action of alpha-thrombin. Tumor-cell incubation with thrombin resulted in an upregulated cell-surface expression of the alpha11b beta 3 integrin, a receptor mediating interactions between tumor cells and endothelial cells, and between tumor cells and SEM. Antibodies against alpha 11b beta 3 integrin effectively inhibited thrombin-enhanced tumor-cell adhesion. Thrombin effects on tumor cells involved the PKC signal transduction pathway as thrombin-enhanced adhesion was inhibited by pre-incubation with PKC inhibitors and a transient PKC translocation from cytosol to membrane was observed following thrombin challenge. In vivo, thrombin-treated tumor cells demonstrated a 2-fold increase in their lung-colonizing ability. In contrast to the adhesion results, the metastasis-enhancing effects of alpha-thrombin were mimicked by a thrombin precursor (prothrombin) and thrombin analogs.

Lysosome-associated membrane protein-1 (LAMP-1) is the melanocyte vesicular membrane glycoprotein band II

Coated vesicles play a critical role in the process of melanogenesis. Antisera raised against a coated vesicle fraction from mouse melanoma cells recognize two major glycoprotein antigens, band I (47-55 kd) and band II (90-120 kd). We demonstrate that band II is lysosome-associated membrane protein 1 (LAMP-1) by the following criteria: 1) the molecular weight and abundance of LAMP-1 varies among tissues but is always identical to that of band II; 2) band II and LAMP-1 co-migrate in sucrose gradient sedimentation studies; 3) immunodepletion of cell extracts with antivesicle serum removes all LAMP-1; and 4) intact organelles immunoisolated with antivesicle serum contain band II and LAMP-1. Our results further confirm the long-suspected relationship between melanosomes and the lysosomal lineage of organelles.

Isolation and characterization of high molecular weight melanogenic inhibitors naturally occurring in melanoma cells

Intrinsic melanogenic inhibitors with high molecular weights have been isolated from Greene's amelanotic hamster melanoma by DEAE ion-exchange and gel filtration chromatographies. The native molecular weights of two partially purified inhibitors have been determined to be 15 kDa (beta-type) and 67 kDa (gamma-type), respectively, using HPLC gel filtration. Both types of inhibitors, despite their inability to directly inhibit isolated tyrosinase, have been shown to markedly inhibit melanin formation in cultured B16 cells. In contrast to the beta-type inhibitor, the gamma-type inhibitor can induce depigmentation in B16 cells without abolishing their internal tyrosinase activity. Further, it has been determined that both inhibitors contain various amounts of unsaturated fatty acids, C15:1, C18:1, C18:2, C18:3, C20:3, and C20:4, which exhibit depigmentary activities on cultured B16 cells. C15:1 is low in the beta-type, but high in the gamma-type whereas C18:3 is high in the beta-type but low in the gamma-type. These results suggest that the differential action of these inhibitors is most likely due to the composition of the unsaturated fatty acids.

Discriminant analysis for classification of murine melanomas and human cervical epithelial cells

Computer analysis of cell images offers many advantages over routine visual examination. It leads to quantitative and accurate detection of subvisual information and provides reproducible measures so that objective decisions in cancer diagnosis become possible. Such diagnostic decisions usually follow partly from a classification process. In this paper two multivariate discriminant analysis methods--namely, linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA)--are presented. LDA and QDA were used to classify cytologic data based on some morphodensitometric measurements. The cytologic data constituted two samples, one representing B16 cell lines and the other including three types of normal human cervical epithelial cells. LDA and QDA were assessed both individually and in comparison to each other, mainly on the basis of the rate of correct classification and robustness. The measurements extracted from the cytologic data employed were shown to be stable and consistent. The statistical results obtained from experiments on cervical cells look particularly promising and encouraging for future work. It has also been shown in this study that the classification techniques employed are valid and that LDA performed almost as well as QDA.

PKC mediates 12(S)-HETE-induced cytoskeletal rearrangement in B16a melanoma cells

The fatty acid 12(S)-HETE may be a new second messenger capable of activating PKC. In tumor cells 12(S)-HETE stimulates cytoskeleton-dependent cellular responses such as adhesion and spreading. Analysis of 12(S)-HETE effects on B16a melanoma cell cytoskeleton revealed reversible rearrangement of microtubules, microfilaments, the actin-binding proteins, vinculin, myosin heavy (MHC) and light chains (MLC), as well as bundling of vimentin intermediate filaments. The alterations in microfilaments and intermediate filaments occurred very rapidly, i.e., 5 min after exposure of tumor cells to 12(S)-HETE. The 12(S)-HETE-induced cytoskeletal alterations were accompanied by centrifugal organelle-translocation. Interestingly, MLC exhibited clear association with the cytoplasmic organelles. Biochemical analysis of the 12(S)-HETE effect indicated a PKC-mediated reversible hyperphosphorylation of MLC, vimentin, and a 130 kD cytoskeletal-associated protein. Optimal effects were obtained after 5 min treatment with 12(S)-HETE at 0.1 microM concentration. 12(S)-HETE pretreatment induced tumor cell spreading on a fibronectin matrix which required the intactness of all three major cytoskeletal components. The spreading process was dependent upon the activity of PKC. Our data suggest that 12(S)-HETE is a physiological stimulant of PKC. Further, it induces rearrangement of the cytoskeleton of tumor cells in interphase resulting in the stimulation of cytoskeleton-dependent cell activity such as spreading.

Glycosylation pathways in the biosynthesis of gangliosides in melanoma and neuroblastoma cells: relative glycosyltransferase levels determine ganglioside patterns

In order to elucidate some of the factors that determine the characteristic expression of gangliosides in malignant melanoma and neuroblastoma the levels of ganglioside synthases (glycosyltransferases) were determined in a panel of cell lines from those tumors that exhibited a wide range of ganglioside composition. Sialyltransferases (GM3, GD3, GD1a, and GT1b synthases), N-acetylgalactosaminyltransferases (GM2 and GD2 synthases), and galactosyltransferase (GM1 and GD1b synthases) were analyzed in crude membrane preparations from these cells. The results confirmed the importance of GM3 and GD3 synthases in determining the prominence of the a (GM3 to GT1a) or b (GD3 to GQ1b) biosynthetic pathways. The overall ganglioside composition in cells was found to be dependent on the relative levels of specific enzymes acting sequentially or in competing pathways. In general, the pattern and levels of transferases correlated with the actual ganglioside content of the cell line, although several important discrepancies were noted. For example, in cell lines containing high amounts of GD2 ganglioside, the level of the preceding enzyme in the pathway (GD3 synthase) was unexpectedly low. Thus, the high GD2:GD3 ratios characteristic of most neuroblastomas result from low levels of GD3 synthase as well as high levels of GD2 synthase. In other cell lines, GD3 synthase was completely absent, resulting in the synthesis of GM2, but not GD2, by N-acetylgalactosaminyltransferase I, as would be expected. It was concluded that different glycosyltransferases play key roles in determining glycolipid expression in different cell types.

The mouse pink-eyed dilution gene: association with human Prader-Willi and Angelman syndromes

Complementary DNA clones from the pink-eyed dilution (p) locus of mouse chromosome 7 were isolated from murine melanoma and melanocyte libraries. The transcript from this gene is missing or altered in six independent mutant alleles of the p locus, suggesting that disruption of this gene results in the hypopigmentation phenotype that defines mutant p alleles. Characterization of the human homolog revealed that it is localized to human chromosome 15 at q11.2-q12, a region associated with Prader-Willi and Angelman syndromes, suggesting that altered expression of this gene may be responsible for the hypopigmentation phenotype exhibited by certain individuals with these disorders.

Defect of insulin receptor in insulin-resistant variants of Cloudman S91 mouse melanoma cells

To study the mechanisms by which insulin regulates proliferation, we have compared wild-type Cloudman melanoma cells, whose growth in inhibited by insulin (insinh) to variant lines that were genetically selected for resistance to insulin (insres). Scatchard analysis of insulin binding to five insres) lines and six insres variants revealed a marked reduction in the number of high-affinity binding sites for insulin in the insres lines, and insres lines displayed an abnormal beta-subunit of the insulin receptor. During autophosphorylation of the wheat germ agglutinin-purified receptor, the beta-subunit apparently underwent proteolytic degradation. This proteolysis was ATP-dependent and was prevented by bovine pancreatic trypsin inhibitor, and phenylmethylsulphonyl fluoride, but not by aprotinin or leupeptin. Receptor proteolysis was not observed in wild-type lines. The results suggest that insulin resistance in the mutant Cloudman melanoma cells is apparently due to proteolysis of the beta-subunit of insulin receptor which, in turn, alters insulin binding capacity of the cells and blocks their anti-proliferative response to the hormone.

Distribution of fibroblast growth factors in cultured tumor cells and their transplants

The distributions of acidic fibroblast growth factor (aFGF) and basic FGF (bFGF) in extracts of various cultured mammalian cells were determined from their elution profiles on heparin-affinity chromatography, and assay of activity as ability to stimulate DNA synthesis in BALB/c3T3 cells. Only aFGF was found in extracts of mouse melanoma B 16 cell and rat Morris hepatoma cell (MH1C1) lines. Other tumor cell lines established from solid tumors and some normal cells contained bFGF as a main component, but blood tumor cell lines contained no aFGF or bFGF. The FGFs in extracts of solid tumor tissues derived by transplantations of these cultured tumor cells and various normal tissues of mice were also examined. Tumors formed by all cell lines, regardless of whether they produced aFGF, bFGF, or neither, contained bFGF that was probably derived from host cells including capillary endothelial cells, in addition to the tumor-derived aFGF or bFGF, if produced. The content of bFGF, possibly derived from the host, in these tumor tissues was comparable to those of various mouse organs other than thymus, lung, spleen, and testis, which have higher bFGF contents. Tumor tissues derived from cultured cells producing bFGF had relatively higher bFGF contents. Like bFGF, aFGF was distributed almost ubiquitously in normal mouse tissues.

Increased expression of alpha IIb beta 3 integrin in subpopulations of murine melanoma cells with high lung-colonizing ability

Four subpopulations of B16 amelanotic melanoma cells, possessing different abilities to induce platelet aggregation (TCIPA) and to form lung colonies, were isolated by centrifugal elutriation. The expression of alpha IIb beta 3, alpha v beta 3 and alpha 5 beta 1 integrins was examined in the 4 subpopulations in order to determine the relationship between integrin receptor expression and tumor-cell metastatic potential. The mRNA of alpha IIb, alpha 5, beta 1 and beta 3 was detectable in the 4 subpopulations by Northern blotting. A gradual increase in mRNAs and cell-surface immunoreactivity of the alpha IIb beta 3 receptor, but not in their gene copies, was observed from the low to the high metastatic subpopulations. The ability of tumor cells to adhere to fibronectin and subendothelial matrix (SEM) increased in parallel. In the high metastatic cells, the alpha IIb beta 3 receptors, but not the alpha 5 beta 1 receptors, were localized to focal adhesion plaques. Incubation of the high metastatic cells with alpha IIb beta 3-specific antibodies reduced their matrix adhesion, TCIPA and lung-colonizing abilities. In contrast, in the low met- astatic cells, SEM adhesion and lung-colony formation were not affected by anti-alpha IIb beta 3 antibody treatment. Incubation of either the low or the high metastatic subpopulation with an alpha 5 beta 1-specific antibody had no effect in vitro and showed a slight inhibition of lung colonization in vivo. Our results suggest that several phenotypic characteristics of the enhanced metastatic potential of B16a subpopulations may be mediated by increased expression of alpha IIb beta 3 receptors and that expression of these receptors may be regulated at the transcriptional level.

Determination of cytosine-cytosine photodimers in the DNA of Cloudman S91 melanoma cells using high pressure liquid chromatography

I measured the induction of cytosine-cytosine dimer (C-C) densities after UV-C (less than 290 nm) and UV-B irradiation (290-320 nm) in the 2'-deoxy-[3H]cytidine labeled DNA of Cloudman S91 mouse melanoma cells using a new, sensitive high pressure liquid chromatography procedure. UV-B exposure resulted in 0.000034% C-C/J m-2 of the total cytosine radioactivity which is 10 times less than the rate during UV-C irradiation. Previous work with these melanoma cells showed a 4-fold lower rate of induction of thymine-containing pyrimidine dimers by UV-B than UV-C light (Niggli Photochem. Photobiol. 52, 519-524, 1990). Based on these results, the calculated ratios for the pyrimidine dimer subspecies showed no significant difference following UV-C and UV-B exposure. However, UV-C and UV-B light induce 10-20 times more thymine-containing pyrimidine dimers than C-C in the DNA of S91 cells.

Expression of alpha-melanocyte stimulating hormone and the invasive ability of the B16 murine melanoma

The expression of alpha melanocyte stimulating hormone (MSH) has been investigated in two variants of the B16 murine melanoma. The presence of MSH was demonstrated by immunohistochemical methods using anti-MSH antibodies. The low metastasis variant B16-F1, which grows as an encapsulated non-invasive tumour, showed no alpha-MSH immunoreactivity. In contrast, the high metastasis variant BL6 was found to be alpha-MSH positive and the immunoreactivity was found predominantly in the peripheral invading zones of the tumour.

Differentiation of new metastatic variants of B16 melanoma under different culture conditions

The purpose of this study was to examine the differentiation of variant tumors of the B16 metastatic melanoma when tumors were grown serially under different culture conditions and transplanted into C57BL/6J black mice, lethal yellow Ay/a, albino c/c, and C+/c mutant mice. Morphological and biochemical markers of melanogenesis were examined in cells in culture and in the corresponding tumors. Cellular pigmentation was assessed in terms of the levels of DOPA and 5-S-CD and in terms of tyrosinase activity in the various cell lines and tumors. The observed change from high to low metastatic capacity, which was dependent on culture conditions, appeared to be unrelated to melanogenesis even though changes were observed in the biochemical melanotic phenotype. Overall, tumor cells from spontaneous pulmonary metastases appear to differentiate in ways that are unrelated to the instability of experimental metastatic capacity. The melanotic phenotype in albino c/c and C+/c mice was dependent on the phenotype of the parental tumors. A marked difference was observed between two pigmentation compartments, one of which was stable in the B16 control, while the other was unstable in YB16 and MB16 variant cells and in the tumors derived from them. It appears, therefore, that the metastatic capacity of B16 metastatic variants is changeable and is independent of the unstable melanogenic behavior. The production of metastases and the differentiation of tumors in the present experiments appeared to be related to the genetic background of the mice and the epigenetic metabolic environment of tumors and cells.

Induction of c-fos but not c-myc in S-91 cells by melanization signals

Synthesis of the pigment melanin is a complex differentiated function performed by pigment cells in response to a variety of stimuli. The possible roles of the proto-oncogenes c-fos and c-myc in the control of pigmentation were studied using subconfluent, actively proliferating Cloudman S-91 murine melanoma cells stimulated to synthesize melanin by melanocyte stimulating hormone (MSH) or forskolin. Stimulation caused a significant increase in melanin synthesis when compared to control cells, but had no effect on cell growth. Northern analysis of total cellular RNA demonstrated rapid, transient induction of c-fos mRNA as early as 30 min after stimulation with MSH or forskolin. In contrast, there was no effect on the high constitutive expression of c-myc in these actively proliferating cells. These data strongly suggest that the induction of c-fos mRNA is an early genetic event in stimulation of melanin synthesis and thus this proto-oncogene may play a major role in the regulation of this differentiated function, as reported for other forms of cellular differentiation. In contrast, c-myc expression is unaffected and instead correlated with cellular proliferative capacity. These results are consistent with the hypothesis that the down-regulation of c-myc frequently observed during cell differentiation is not a necessary event, but rather reflects an associated decrease in cell growth rate. The S-91 melanoma system appears to provide a convenient model for study of the regulation for a single, well defined differentiated function that is independent of growth rate.

Monoclonal anti-melanoma antibodies IKH-1 and IKH-2 which work on formalin-fixed, paraffin embedded tissues: characterization, clinical trials and comparative studies with HMB-45

Mouse monoclonal antibodies (MoAbs), IKH-1 and IKH-2, were produced against cloned human melanoma cells, KHm-6, which were cultured with 12-O-tetradecanoylphorbol-13-acetate (TPA) and processed by formalin fixation and alcohol dehydration (FFAD). According to the biochemical analysis, antigenic substances which reacted with IKH-1 were 34.0-60.0 kDa glycoproteins, and those which reacted with IKH-2 were 33.5, 34.5 and 36.0 kDa glycoproteins. Immunoelectron microscopy revealed that reaction products of IKH-1 were seen in some membranous vesicles, premelanosomes and cell membrane of TPA-treated KHm-6 cells, while IKH-2 recognized only premelanosomal structures. Immunohistochemical tests revealed that IKH-1 and IKH-2 have a high sensitivity (94.0% and 85.0%, respectively) to formalin-fixed, paraffin-embedded (FFPE) tissue sections of malignant melanomas. IKH-1 had a high specificity and IKH-2 and 100% specificity to FFPE tissue sections of melanocytic lesions.

Differential sensitivities of murine melanocytes and melanoma cells to buthionine sulfoximine and anticancer drugs

High levels of intracellular glutathione (GSH) may result in resistance of tumor cells to cytotoxic drugs. Because of the innate refractory nature of melanoma cells to chemotherapy, we have used a syngeneic murine system consisting of nontumorigenic Mel-ab melanocytes, tumorigenic H-ras-transformed melanocytes (C9.1), and the highly metastatic BL6 melanoma cells to examine the GSH content, glutathione S-transferase (GST) activity, and sensitivity to buthionine sulfoximine (BSO) and other cytotoxic drugs. Compared to the nontumorigenic melanocytes, both C9.1 and BL6 melanoma cells have nearly fivefold higher GSH content, and BL6 cells have increased GST activity. C9.1 and BL6 cells are more resistant to the cytotoxic effects of BCNU and adriamycin; however, the degrees of resistance do not reflect the increased GSH content in these cells. Pretreatment of BL6 melanoma cells with 50 microM BSO depleted over 90% of their GSH content and enhanced the growth-inhibitory effects of L-dopa methylester, BCNU, bleomycin, and dacarbazine. Exposure to BSO alone was not toxic to the tumor cells for up to 24 hr, but was significantly cytotoxic in the melanocytes after 9 hr. The sensitivity of these cells to BSO appears to depend on a critical level of GSH depletion which is not related to the initial GSH content. These studies suggest that the resistance of melanoma cells to cytotoxic drugs is only partially attributed to changes in the GSH system caused during cellular transformation.

Comparative action of dopachrome tautomerase and metal ions on the rearrangement of dopachrome

A vis-a-vis comparison between the effects of dopachrome tautomerase (DCT) and metal ions, e.g., cupric ions, on the kinetics and mode of rearrangement of dopachrome has been carried out under appropriate analytical conditions. The enzyme-promoted reaction is highly stereospecific for L-dopachrome, is unaffected by metal chelators and has an optimal pH around 6.8. By contrast, the kinetics of dopachrome rearrangement catalysed by cupric ions are not dependent on the stereochemistry of the substrate, are affected by EDTA and are not influenced by the pH of the medium in the range between 5-7.5. Both cupric ions and DCT catalyse the rearrangement of dopachrome to give 5,6-dihydroxyindole-2-carboxylic acid (DICA) rather than 5,6-dihydroxyindole (DI). However, at comparable activity, the ratio of formation DICA/DI is significantly higher in the enzyme-catalysed than in the metal-catalysed reaction. These results provide an improved background to look into the mode of action of DCT and metal ions, enabling a clear cut differentiation between the effects of the two factors when both are present in biological extracts.

POMC gene expression in mouse and hamster melanoma cells

Expression of mRNA hybridizable to murine POMC cDNA, and immunoreactivity specific for POMC derived peptide, beta-endorphin, are reported for the first time in one murine and two hamster melanoma lines. The apparent sizes of POMC mRNA transcript were 3.5, 1.5 and 1 kb. It is suggested that POMC gene expression may be involved in the autoregulation of the melanoma phenotype at the cellular and tissue levels.

Increase of sialylated tetraantennary sugar chains in parallel to the higher lung-colonizing abilities of mouse melanoma clones

The N-linked sugar chains of melanoma cell membrane from five murine B16 melanoma clones (F1, F10, BL6, W1-4, and C4-1) with different degrees of metastatic abilities after intravenous and intrafootpad injections were released quantitatively as oligosaccharides by hydrazinolysis, and their structures were analyzed by serial lectin column chromatography, Bio-Gel P-4 column chromatography, and sequential glycosidase digestion. Sugar chain structures of each clone have shown to consist of the same elemental oligosaccharides, but to differ in their percent compositions. More than 84% of the neutral oligosaccharides were high mannose-type sugar chains. Most complex-type sugar chains were sialylated, of which the major structure was tetraantennary sugar chain. Highly lung-colonizing F10 cells had 1.4 and 1.7 times more non-repeated tetraantennary sugar chains than moderately colonizing F1 and C4-1 cells, respectively, and 2.5 times more than poorly colonizing W1-4 cells. BL6 cells, which are also highly lung-colonizing, had 1.5 and 1.9 times more non-repeated tetraantennary sugar chains than F1 and C4-1 cells, respectively, and 2.8 times more than W1-4 cells. These results suggest that increase of sialylated tetraantennary complex-type sugar chains without N-acetyllactosamine repeating units of B16 melanoma cells might correlate with the higher lung-colonizing ability after intravenous injection.

Cysteinyldopamine is not incorporated into neuromelanin

The pigment of human substantia nigra, neuromelanin, has been thought to be derived from dopamine. To examine the genesis of neuromelanin, we advanced a new hypothesis that neuromelanin is formed by oxidation of dopamine and cysteinyldopamine. On the basis of this hypothesis, synthetic neuromelanins were obtained by tyrosinase oxidation of dopamine in the presence of various ratios of cysteine and were hydrolyzed with hydriodic acid to obtain 4-amino-3-hydroxyphenylethylamine (AHPEA). The AHPEA content in these synthetic melanins was shown to be proportional to the sulfur content. Eleven samples of human substantia nigra were treated as well and contents of AHPEA were found to be only trace amounts. These results suggest that cysteinyldopamine may not be incorporated into neuromelanin.

Multiple differences between wild-type B16 melanoma cells and a wheat germ agglutinin resistant clone

A low-metastatic, glycosylation-defective variant of the B16 murine melanoma was obtained by Tao and Burger (1977) through selection with wheat germ agglutinin. We found that variant and parental (wild-type) cell lines were equally invasive when confronted with precultured embryonic chick heart fragments in vitro. Also, a short-term in vivo arrest assay showed no significant differences. After intravenous injection, wild-type cells killed the recipient mice faster than did the variant cells. We were able to confirm the changes in glycosylation at the enzyme level. In addition, we showed that the pattern of endogenous lectins was strikingly different, at least at the quantitative level. We also looked at another set of receptor proteins, namely receptors for neurotransmitters coupled to adenylate cyclase. The response to the vasoactive intestinal peptide and prostaglandins was lower in the variant cells, which also had a delayed response to cholera toxin. Although most of the data can be explained by altered glycosylation in the variant cells, the large number of differences between variant and parent cells makes it difficult to identify the biochemical basis of altered metastatic behaviour. This might also be the case with other pairs of cells differing in metastatic activity.

Production and characterization of tumor infiltrating lymphocyte clones derived from B16-F10 murine melanoma

The adoptive transfer of tumor infiltrating lymphocytes (TIL) in conjunction with recombinant interleukin-2 (rIL-2) for the treatment of advanced cancer has recently been under intense investigation. Despite extensive research, the precise surface phenotype of TIL remains to be fully defined. To elucidate this unsolved problem, we established 11 TIL clones derived from rIL-2 expanded TIL obtained from B16-F10 murine melanoma tumors. These clones could be divided phenotypically into four groups: CD8 (+) T-cell clones, natural killer (NK)-cell clones, NK-like CD8 (+) T-cell clones, and double negative T-cell clones. Functionally, CD8 (+) T-cell clones demonstrated specific cytotoxic activity against B16-F10 melanoma cells, whereas NK-cell clones and double negative T-cell clones demonstrated only non-specific cytotoxic activity against NK-sensitive YAC-1 cells. NK-like CD8 (+) T-cell clones showed dual cytotoxic activity. Clones T1 [a CD8 (+) T-cell clone] and T2 [an NK-like CD8 (+) T-cell clone] which had cytotoxic activity against B16-F10 melanoma cells, demonstrated a proliferative response against immunoblotted B16-F10 melanoma antigens, whereas clones T7 (an NK-cell clone) and T10 (a double negative T-cell clone), which had no cytotoxic activity against B16-F10 cells, demonstrated no proliferative response against them. Winn assays revealed that only the CD8 (+) T-cell clone (T1) had an antitumor effect in vivo, whereas the double negative T-cell clone (T10) and NK-like CD8 (+) T-cell clone (T2) stimulated tumor growth in vivo. Adoptive immunotherapy using tumor-specific, highly cytotoxic TIL clones may represent a useful future immunotherapeutic option for the treatment of human tumors.

Purification of B16-F1 melanoma autocrine motility factor and its receptor

Tumor autocrine motility factor (AMF) is a cytokine which stimulates both random and directed cell migration by self-producing cells. AMF has been detected in and purified from serum-free conditioned medium of murine B16-F1 melanoma cells. Under nonreducing conditions AMF migrates in sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a single band of Mr 55,000, whereas under reducing conditions it migrates as a single polypeptide of Mr 64,000. Two-dimensional polyacrylamide gel electrophoresis of the purified AMF resolved two polypeptides with isoelectric points of 6.35 (major) and 6.4 (minor). No carbohydrate side chains were detected in the B16-F1 AMF. Purified AMF stimulated B16-F1 cell migration in a dose-dependent fashion and bound directly in a protein-protein-binding assay to the AMF receptor, a cell surface glycoprotein of Mr 78,000 [glycoprotein (gp) 78]. The involvement of gp78 in AMF-stimulated function was demonstrated by motility assays. These results suggest that AMF is the natural ligand for the gp78-AMF receptor.

Characterization of a highly invasive and spontaneously metastatic human malignant melanoma cell line

Although the incidence of, and deaths due to, malignant melanoma are rising at a rapid rate, few experimental models mimic the highly metastatic properties associated with the pathogenesis of the human disease, making study of the disease difficult. Thus, new human models are required to understand melanoma biology, especially its metastatic properties. Here we describe C8161, a highly invasive and spontaneously metastatic human melanoma cell line, which grows progressively in the subcutis of athymic nude mice with an average doubling time of approximately 6 days. By the time the tumor reaches a diameter of 1 cm, amelanotic metastases in lymph nodes, skin, peritoneal wall, spleen and lungs have formed. By comparing C8161 to variants from other well-characterized human malignant melanomas (A375 and MeWo) with differing metastatic traits, properties presumed to be involved in metastatic propensity were examined. C8161 showed a 2- to 14-fold higher ability to invade reconstituted basement membrane barriers in the MICS and correspondingly high type-IV collagenase mRNA levels and collagenolytic activity, as compared with other melanoma cell lines. Likewise, differential adhesion to immobilized RBM or HUVEC monolayers was observed, but did not correlate to rank orders of malignant properties. Recently, a correlation between surface expression of ICAM-1 and secondary tumor formation by human melanomas has been described in several laboratories. Basal levels of ICAM-1 on C8161, A375 and MeWo human melanomas were compared, but no correlation with metastatic potential was noted. Proto-oncogene expression in C8161 cells was compared with A375P and A375M variants using Northern blot analysis. c-myc expression was 6-fold greater than both A375 variants; c-fos expression was 3.4-fold less than A375P and 1.7-fold less than A375M; c-jun in C8161 cells was 2.5-fold and 2.1-fold greater than expression in A375P and A375M, respectively. Because C8161 is so highly malignant, amenable to experimental manipulation, and its behavior in nude mice mimics the clinical course of malignant melanoma, this cell line will prove valuable for studying properties associated with human melanoma tumor progression.

Heterogeneity of the MSH receptor among B16 murine melanoma subclones

The heterogeneity of melanotropin receptors on B16 sublines was tested by using photoaffinity crosslinking techniques and the superpotent alpha-MSH derivative [Nle4, D-Phe7, 1'-(2-nitro-4-azido-phenylsulfenyl)-Trp9]-alpha- MSH (NAPS-MSH). Specific crosslinking of this compound to B16-F1, B16-F10, B16-M2R or B16-W4 cells revealed three different subtypes of MSH receptor based on SDS-PAGE analysis. Binding of monoiodinated alpha-MSH to these different subclones is saturable and characteristic for a single class of complexes (0.9 nM less than KD less than 1.6 nM). In this article the nature of the different MSH receptor subtypes as well as their possible correlation to the melanogenic potential of a particular cell line is discussed.

Tyrosinase expression and melanogenesis in melanotic and amelanotic B16 mouse melanoma cells

Tyrosinase activity, abundance, and mRNA transcription were examined in three sublines of the B16 mouse melanoma. Tyrosinase activity and melanin content were highest in the B16-F1 cells, slightly less in the B16-F10, and markedly lower in the B16-F10-DD cells. No differences in the level of tyrosinase mRNA or protein were found in the three different sublines. Thus, the differences in tyrosinase expression arise from the post-translational modification of the enzyme causing its activation or inhibition.

Measurement of DNA content and nuclear pleomorphism in metastatic variants of the B16 murine melanoma and hamster lymphoma and its liver metastasis using image analysis techniques

The DNA content and nuclear pleomorphism (NPM), which are two cellular features consistently employed in the assessment of tumour malignancy, have been measured in B16 murine melanoma metastatic variants and in hamster primary lymphoma and its liver metastasis as tumour models using image analysis techniques. The three melanoma variants studied were the low metastasis variant F1, the BL6 variant selected for high lung metastasis and invasive ability, and ML8, a line isolated from pulmonary metastasis of the BL6 tumour. The cellularity of the melanomas bore no relationship to metastatic ability. The cell cycle distribution of nuclei based on integrated nuclear density (IND) was studied. The ML8 tumour showed higher DNA ploidy. Also, in this tumour the S-phase fraction was approximately 2.0-fold larger than that of the BL6 tumour. Flow cytometry of nuclei isolated from paraffin-embedded tumour tissue showed all three melanomas were aneuploid. In both F1 and BL6, two distinct subpopulations (p2 and p3) of nuclei, based on the degree of their pleomorphism, could be discerned. A significantly higher proportion of the more pleomorphic subpopulation (p2) occurred in BL6 than in F1. In the ML8 alone, a third subpopulation (p1), which was more pleomorphic than p2, was found. The hamster lymphomas (HALY-malignant and N-HALY-non-malignant) were less cellular than the metastatic tumour (HALY-met) in liver. The lymphomas N-HALY and HALY-met had a higher DNA ploidy as compared with its primary tumour HALY. However, the non-malignant lymphoma N-HALY and the moderately malignant hamster fibrosarcoma were also found to be hyperdiploid. The metastatic lymphoma (HALY-met) showed a more pleomorphic nuclear subpopulation as compared with the primary. No differences were found in the size of the S-phase fractions of the hamster tumours. The present work shows that image analysis techniques enable one to make objective measurements of DNA content and nuclear pleomorphism of tumour cells, and suggests that in the tumour models investigated there is increased nuclear pleomorphism and DNA ploidy associated with tumour progression.

Electron spin resonance imaging of mouse B16 melanoma

An X-band electron spin resonance (ESR) imaging apparatus with a pin-hole TE102 mode cavity and a rapid scan coil was constructed. Using this apparatus, ESR imaging of melanin in mouse B16 melanoma was observed for the first time. The ESR spectrum of B16 melanoma is similar to that of natural melanin extracted from sepia officinalis in microwave power dependence.

Magnetic susceptibility and electron spin resonance absorption spectra of mouse melanomas S91 and 591A

A study of magnetic susceptibility and electron spin resonance (E.S.R.) spectra of Cloudman S91 and S91A melanomas and various mouse tissues was correlated with trace-metal analysis and known biochemical reactions. Average magnetic moments obtained from temperature-dependence studies showed the following order for tissues: S91>S91A>leg muscle. These results indicated a similar order in the relative concentration of magnetic species (free radicals and/or paramagnetic ions) and were confirmed by E.S.R. The E.S.R. spectra at different power levels showed that the free radical activity and the Cu2+ and Fe3+ activity attributed to different signals was generally higher in S91 than in S91A, which did not show an Fe3+ type signal. Normal tissues such as liver, spleen, heart, kidney, brain, and leg muscle showed varying amounts of free radical activity but not signals attributable to paramagnetic ions. E.S.R. spectra and trace-metal analysis at different stages of S91 tumor growth indicated a systematic increase in the free rad cal activity, total copper and iron concentrations, and paramagnetic ions, presumed to be Cu2+ and Fe3+. The S91A melanoma showed increase in total copper, but not in free radical and paramagnetic ion (CU2+) activity after the initial growth. Correlation of these findings with known biochemical reactions suggests that the free radical activity may be attributed partly to melanin and intermediates of various enzymatic reactions. Presumed paramagnetic ion activity cannot yet be ascribed to specific biostates.