Loss of beta-catenin expression associated with disease progression in malignant melanoma.

BACKGROUND: beta-catenin plays a crucial role in the function of cell adhesion molecules and also participates in growth regulatory signalling pathways that may be involved in malignant transformation. OBJECTIVES: To examine beta-catenin expression in lesions of melanocytic origin for associations with clinicopathological markers of disease progression and for its significance as a predictor of disease recurrence and prognosis. METHODS: beta-catenin expression was examined by immunoperoxidase staining in 50 melanocytic naevi and 91 primary and 50 metastatic melanomas. RESULTS: beta-catenin was expressed in 96% of melanocytic naevi, in 94% and 65%, respectively, of radial and vertical growth phase primary melanomas, and in 38% of metastatic melanomas. Benign and malignant melanocytic lesions had distinct patterns of beta-catenin localization. Most lesions expressing beta-catenin exhibited cytoplasmic staining; however, over 40% of benign lesions also displayed nuclear staining, which was present only in 10% of primary and 15% of metastatic melanomas. Absent or weak expression of beta-catenin in primary melanomas was associated with several markers of disease progression, including tumour thickness and presence of lymph node metastases. A similar but not statistically significant trend was observed for the association of beta-catenin expression with disease recurrence and prognosis. CONCLUSIONS: These results suggest that loss or downregulation of beta-catenin expression in melanoma cells plays a significant role in progression of the disease.

Expression of a catalytically inactive H118Y mutant of nm23-H2 suppresses the metastatic potential of line IV Cl 1 human melanoma cells.

Nm23-H1 and nm23-H2 are putative metastasis suppressor genes that encode nucleoside diphosphate kinase (NDPK) A and B. NDPKs form oligomers distributed between soluble and particulate fractions of cells and therefore may exert their effects as either soluble or bound proteins. To determine whether metastasis-related functions of NDPKs are mediated by their catalytic activity in membrane bound or soluble complexes, we have stably transfected highly metastatic human melanoma Line IV Cl 1 cells with wild-type and catalytically inactive (H118Y) nm23-H1 and nm23-H2 genes and assayed their metastatic potential in nude mice. Transfection with wild-type nm23-H1 and nm23-H2 genes and catalytically inactive nm23-H1 did not significantly (all p > 0.10) alter the metastatic potential of Line IV Cl 1 cells while transfection with catalytically inactive nm23-H2 significantly (p < 0.01) reduced their metastatic potential. The lack of effect of transfection with wild-type and catalytically inactive nm23-H1 suggests that neither soluble nor membrane bound NDPK A affect the metastatic potential of Line IV Cl 1 cells. The metastasis suppressive effect of catalytically inactive NDPK B overexpression suggests that competition with bound complexes containing catalytically active NDPK B inhibits metastasis of Line IV Cl 1 cells. These results imply that bound NDPK B promotes metastasis and suggest that inhibition of its function or of its binding to critical sites may be a useful approach to limit the development of metastases in human melanoma.

Alpha(v)beta3 expression on blood vessels and melanoma cells in primary lesions: differential association with tumor progression and clinical prognosis.

The alpha(v)beta3 integrin has emerged as a key mediator in angiogenesis. Its role in tumor-induced angiogenesis is supported by its up-regulation in vivo in the vasculature of a number of different types of carcinoma. The potential clinical significance of alpha(v)beta3 expression on blood vessels in carcinomas is suggested by its association with tumor progression. Currently no information is available about the clinical significance of alpha(v)beta3 expression on the vasculature of lesions of melanocytic origin. Since we have previously found that alpha(v)beta3 expression on melanoma cells in primary lesions is associated with a poor prognosis, in the present study we have compared alpha(v)beta3 expression on blood vessels and on cells of melanocytic origin in nevi and in malignant melanoma lesions. In addition we have examined the lesions for expression of the alpha(v) subunit to gain information on the regulation of alpha(v)beta3 expression on endothelial cells and on cells of the melanocyte lineage. alpha(v)beta3 expression on endothelial cells and on melanocytic cells was a relatively sensitive and specific marker for malignant lesions. However, alpha(v)beta3 expression on endothelial cells in primary melanoma lesions was not associated with the prognosis of the disease. The alpha(v) subunit and the alpha(v)beta3 complex were differentially expressed on endothelial cells and on melanocytic cells, implying that different regulatory pathways control their expression. This finding may account for the differential clinical significance of alpha(v)beta3 expression on tumor vasculature and on melanoma cells we observed in our patient cohort. Lastly, alpha(v)beta3 may be a useful target for immunotherapeutic approaches in melanoma because of its high expression on the vasculature of all metastatic lesions tested and its restricted distribution in normal tissues.

Increased beta2-microglobulin-free HLA class I heavy chain serum levels in the course of immune responses to viral antigens and to mismatched HLA antigens.

Besides being present in serum in association with beta2-mu, HLA class I heavy chains are also present in serum as beta2-micro-free moieties. The increase in serum levels of beta2-micro-associated HLA class I heavy chains in conditions associated with an activation of the immune system have prompted us to measure the serum levels of beta2-mu-free HLA class I heavy chains in the course of immune responses to viral antigens and to mismatched histocompatibility antigens. The serum level of beta2-mu-free HLA class I heavy chains, like that of beta2-mu-associated HLA class I heavy chains was significantly increased in patients affected by advanced HIV-1 infection or by chronic hepatitis C (CHC). In the latter group of patients an association was found between a reduction in the beta2-mu-free HLA class I heavy chain serum level and response to therapy with interferon alpha and ribavirin. Moreover, the beta2-mu-free HLA class I heavy chain serum level was increased more than that of beta2-mu-associated HLA class I heavy chains during episodes of liver ischemia following liver transplantation and in the course of acute graft rejection and of acute graft-versus-host-disease (GVHD) after allogeneic bone marrow transplantation (BMT). These results suggest that the serum levels of beta2-mu-free and beta2-mu-associated HLA class I heavy chains are independently regulated. Furthermore, beta2-mu-free HLA class I heavy chain serum level may be a useful marker to monitor response to therapy in CHC patients and the clinical course of liver and bone marrow grafts.

Differential clinical significance of alpha(v)Beta(3) expression in primary lesions of acral lentiginous melanoma and of other melanoma histotypes.

Despite its potential clinical relevance, alpha(v)beta(3) expression has been analyzed only in a limited number of melanoma lesions, mostly nodular melanoma (NM) and superficial spreading melanoma (SSM). Therefore, in the present study, we have correlated alpha(v)beta(3) expression in 33 acral lentiginous melanomas (ALMs), 6 lentigo maligna melanomas, 7 mucosal melanomas, 12 NMs and 9 SSMs with their antigenic profile, with their histo-pathological characteristics and with the clinical course of the disease. Furthermore, we have compared alpha(v)beta(3) expression in ALM lesions with that in NM and SSM lesions since this information helps to clarify the relationship of the latter 2 histotypes with ALM. Such a relationship is uncertain since ALM has a clinical course similar to that of NM and SSM despite different antigenic profiles and biological characteristics. The level of alpha(v)beta(3) expression in primary lesions was not correlated with that of high-m. w. melanoma-associated antigen and intercellular adhesion molecule-1, with lesion thickness and with disease recurrence in ALM but was significantly correlated with these 4 parameters in the other melanoma histotypes analyzed. Therefore, alpha(v)beta(3) expression appears to have a differential clinical significance in ALM and in the other histotypes of melanoma we have analyzed since it appears to play a significant role in the progression of the disease only in non-ALM histotypes.

Beta2-micro-free HLA class I heavy chain levels in sera of healthy individuals. Lack of association with beta2-micro-associated HLA class I heavy chain levels and HLA phenotype.

We have applied a double-determinant immune assay (DDIA) to measure soluble beta2-microglobulin (beta2-micro)-free HLA class I heavy chains in serum. The mean concentration of beta2-micro-free HLA class I heavy chains in serum from 120 healthy subjects was 0.21+/-0.24 microg/ml. The individual serum levels of beta2-micro-free HLA class I heavy chains had a wide distribution, did not seem to be related with HLA phenotype, were stable over time and did not change with age. The serum levels of soluble beta2-micro-free HLA class I heavy chains did not correlate with those of soluble beta2-micro-associated HLA class I heavy chains, suggesting that their release is independently regulated. Three forms of soluble beta2-micro-free HLA class I heavy chains, with apparent molecular masses of 44, 39 and 37-35 kD, respectively, circulate in human serum. These results provide a useful background to assess the serum level of soluble beta2-micro-free HLA class I heavy chains in pathological conditions and to evaluate their putative immunoregulatory function.

Improved tumor targeting of rhenium-186-labeled anti-human high-m.w. melanoma-associated antigen monoclonal antibody 763.74 following purification with anti-idiotypic monoclonal antibody MK2-23.

Because of its high-energy beta emissions and imageable gamma emissions, 186Re represents an attractive isotope to radiolabel monoclonal antibodies (MAbs) recognizing human tumor-associated antigens (TAAs) for radioimmunoscintigraphy (RIS) and radioimmunotherapy (RIT) of patients with malignant diseases. Application of 186Re, however, is hindered by the frequent denaturation of MAbs following exposure to the strong reducing conditions employed in the labeling procedures. To overcome this problem, we have utilized a direct labeling procedure and combined it with affinity chromatography over columns of immobilized anti-idiotypic (anti-id) MAbs which recognize idiotopes in the antigen-combining site of the radiolabeled MAb. The validity of the procedure was demonstrated with the anti-high-m.w. melanoma-associated antigen (HMW-MAA) MAb 763.74 and its corresponding anti-id MAb MK2-23. Utilizing this approach, MAb 763.74 was labeled to specific activities of 2.8 +/- 0.6 mCi/mg with 186Re. Furthermore, its immunoreactivity, which was reduced to about 30% following labeling with 186Re, was improved to about 50% by affinity chromatography over columns of anti-id MAb MK2-23. The improvement in immunoreactivity of 186Re MAb 763.74 resulted in a significant (p < 0.05) increase in targeting to human melanoma tumors grown in nude mice and an increase in sensitivity of RIS. Our results suggest that direct labeling of anti-TAA MAb with 186Re coupled with purification over affinity columns of anti-id MAb may facilitate the application of 186Re to RIS and RIT.

Clinical significance of alpha(v)beta3 integrin and intercellular adhesion molecule-1 expression in cutaneous malignant melanoma lesions.

Several lines of experimental evidence in in vitro and animal model systems suggest that the integrin alpha(v)beta3 plays a role in the tumorigenicity of human melanoma cells and that the blocking of alpha(v)beta3 ligand binding can inhibit tumor progression. However, there is only scanty information about the role of alpha(v)beta3 in malignant melanoma in a clinical setting. Therefore, in the present study, we have analyzed the distribution in lesions of melanocyte origin and in normal tissues of the alpha(v) integrin subunit and of the alpha(v)beta3 complex and their association with histopathological and clinical parameters of malignant melanoma. We have used as probes the monoclonal antibodies (mAbs) TP36.1 and VF27.263.15, which we have shown with a combination of serological and immunochemical assays to be specific for the alpha(v) subunit and for the alpha(v)beta3 complex, respectively. In immunohistochemical assays, mAb TP36.1 stained both benign and malignant lesions of melanocyte origin. In contrast, the reactivity of mAb VF27.263.15 was restricted to malignant lesions. Both mAbs displayed differential reactivity with primary melanoma lesions of different histotypes because they stained about 50% of acral lentiginous melanoma and superficial spreading melanoma lesions, at least 80% of nodular melanoma lesions, and none of the uveal melanoma lesions tested. Both mAbs TP36.1 and VF27.263.15 stained about 60% of lymph node metastases and 80% of cutaneous metastases. Expression of the alpha(v)beta3 complex in melanocytic lesions resembles that of intercellular adhesion molecule-1 (ICAM-1) in several respects: (a) both are expressed in a significantly (P < 0.004) larger proportion of malignant than of benign lesions; (b) expression of both molecules in primary melanoma lesions is significantly (P < 0.05) associated with lesion thickness; and (c) expression of both molecules in primary lesions from patients with stage I melanoma is significantly (P < 0.05) associated with an increased probability of disease recurrence following surgical excision. alpha(v)beta3 and ICAM-1 in primary melanoma lesions complement each other in predicting the outcome of the disease, because the association with prognosis was enhanced when primary lesions were stained by both anti-alpha(v)beta3 mAb VF27.263.15 and anti-ICAM-1 mAb CL203.4 or by neither mAb. Because alpha(v)beta3 has been suggested as a potential target of immunotherapy, its distribution in normal tissues was investigated. alpha(v)beta3 expression is restricted because it was only detected in ductal epithelium of parotid glands, thyrocytes, basal glands of the stomach, colonic and rectal epithelium glomeruli, Bowman's capsules and proximal and distal tubules of kidneys, and endometrial epithelium. These findings suggest that renal function will be a critical clinical parameter to monitor in therapies of malignant diseases relying on systemic administration of anti-alpha(v)beta3 mAb.

Purification by affinity chromatography with anti-idiotypic monoclonal antibodies of immunoreactive monoclonal antibodies following labeling with 188Re.

Because of its high energy beta emissions and imageable gamma emissions, 188Re represents an attractive isotope to radiolabel monoclonal antibodies (mAb) recognizing human tumor-associated antigens for radioimaging and radioimmunotherapy in patients with malignant diseases. The application of 188Re is, however, hindered by the denaturation of a sizable proportion of antibody molecules during the labeling process. To overcome this problem, we have combined radiolabeling of mAb with 188Re with purification of immunoreactive 188Re-labeled mAb by affinity chromatography over columns of anti-idiotypic (anti-id) mAb. Utilizing the anti-high-molecular-weight melanoma-associated antigen (HMW-MAA) mAb 763.74 as a model system, we found that the immunoreactivity of mAb 763.74 labeled with 188Re to a specific activity of 1 mCi/mg increased from about 50% to at least 80% following passage over columns of immobilized anti-id mAb. Moreover, between 90-100% of immunoreactive mAb contained in radiolabeled preparations could be recovered from anti-id mAb columns. These results indicate that the procedure we have described may facilitate the application of 188Re for immunoscintigraphy and immunotherapy of malignant diseases.

Coronary artery stenosis in rats affects beta-adrenergic receptor signaling in myocytes.

OBJECTIVE: The purpose of this study was to determine whether the early chronic ischemic cardiomyopathy produced by non-occlusive coronary artery constriction was characterized by alterations in the regulation of beta-adrenoreceptor (beta-AR) signaling. METHODS: Coronary artery narrowing was surgically induced in rats and the animals sacrificed at 7 and 14 days. The changes in the biochemical properties of the multiple components of the beta-AR pathway were examined in enzymatically dissociated myocytes. RESULTS: Coronary stenosis, involving an average 55% reduction in luminal diameter, was associated with left ventricular failure and right ventricular dysfunction at both time intervals. A decrease in the quantity of beta-AR was detected at 7 days and preceded the loss of high-affinity binding sites. This regulatory modification was characterized by a reduction in beta 1 and beta 2 receptors and a shift in the isoproterenol dose response curve indicating a functional correlation between the decrease in beta-AR and attenuated inotropic support of the myocardium. The percentage of beta-AR binding agonist with high affinity decreased significantly at 14 days along with a further reduction in the density of beta 1 and beta 2 receptors. Reconstitution studies with cyc S49 lymphoma cells did not detect an impairment of Gs alpha functional activity, but the quantity of Gi alpha was increased at both intervals. Finally, activation of the catalytic unit of adenylyl cyclase by forskolin and GTP was not altered by coronary stenosis, however, basal cyclic AMP in myocytes was depressed at 14 days. CONCLUSIONS: Coronary stenosis induces distinct and progressive modifications in the beta-AR signaling cascade which may contribute to the impaired ventricular performance in this model of myocardial ischemia.

Decreased 3 alpha-hydroxysteroid dehydrogenase activity in peripheral blood lymphocytes from patients with primary open angle glaucoma.

The purpose of the present study was to determine whether peripheral blood lymphocytes (PBL) from primary open angle glaucoma (POAG) patients have reduced 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) activity as was previously found in POAG-derived cultured trabecular meshwork cells. The availability of PBL from both POAG and control patients makes this a useful system for studying the association of decreased 3 alpha-HSD activity with POAG. PBL were isolated from the venous blood of 17 POAG patients and 22 non-glaucoma controls and assayed for 3 alpha-HSD activity with tritiated 5 beta-dihydrocortisol as a substrate. The mean 3 alpha-HSD activity +/- S.E.M., expressed in comparable units of specific activity, of the POAG derived PBL was 13.8 +/- 1.3 U as compared to 32.8 +/- 2.0 U for control cells. This reduction (> 50%) was statistically significant (P < 0.001). Quantitative immunoblot analysis of PBL indicated that the POAG and control cells, despite their difference in 3 alpha-HSD activity, had nearly identical amounts of 3 alpha-HSD protein. The molecular weight of PBL 3 alpha-HSD from both groups of patients was 38,000, the same as previously reported for human liver. The results of this study show an association of decreased PBL 3 alpha-HSD activity and POAG which was not related to antiglaucoma therapy. The reduced levels of 3 alpha-HSD activity in the readily obtainable PBL may serve as a marker for POAG or those at risk for developing the disease.

Differential expression and mutation of NME genes in autologous cultured human melanoma cells with different metastatic potentials.

The putative metastasis suppressor genes, NME1(nm23-1) and NME2(nm23-2), were examined in a model system we developed to approximate the dissemination of melanoma from a primary skin tumor. We utilized two autologous human melanoma cell lines, IV Cl 1 and IV Cl 3, which displayed qualitatively different metastatic phenotypes following subdermal inoculation into nude mice. Highly metastatic IV Cl 1 cells expressed approximately 5 fold lower levels of protein encoded by NME genes than non-metastatic IV Cl 3 cells. Similar differences in NME protein levels were observed in tumors induced by the two cell lines in nude mice. There were no differences in NME mRNA levels between these two cell lines, suggesting that expression of these proteins is regulated at a post-transcriptional level. We found a ser122-pro mutation in the NME2 gene of metastatic IV Cl 1 cells. A similar ser120-gly mutation in NME1 has been found in human neuroblastoma, suggesting that mutation in this region may be a general phenomenon related to tumor progression. These mutations may have functional consequences since they eliminate potential phosphorylation sites and may affect the tertiary structure of mature protein complexes.

Alterations in angiotensin II receptor mediated signal transduction shortly after coronary artery constriction in the rat.

OBJECTIVE: The aim of the study was to determine the effect of coronary artery constriction on the density of angiotensin II receptors and on the effector responses coupled with these receptors on myocytes one week after surgical induction of coronary artery stenosis in rats. METHODS: After induction of coronary artery stenosis and following the estimation of global cardiac performance, myocytes were enzymatically dissociated and radioligand binding studies were performed. In addition, the isotonic contractile performance, cytosolic calcium transients, and angiotensin II stimulated inositol phosphate generation in myocytes were measured in the presence and absence of the angiotensin II receptor subtype antagonist losartan. RESULTS: After documenting left ventricular failure and right ventricular dysfunction, the expression and density of angiotensin II receptors in left ventricular myocytes were evaluated and found to be increased 3.1-fold and 4.1-fold, respectively. Corresponding increases in right ventricular myocytes were 3.6-fold and 4.5-fold. In contrast, the quantity of the regulatory protein Gq alpha was not altered in either ventricle. Angiotensin II did not increase the generation of total inositol phosphates in left and right ventricular myocytes at maximum stimulation. However, the threshold for the formation of inositol phosphates was lowered in left ventricular myocytes of coronary narrowed rats. Measurements of single cell mechanics indicated that angiotensin II stimulation markedly improved the depression in myocyte function biventricularly. This inotropic effect was coupled with the restoration of cytosolic calcium. CONCLUSIONS: The upregulation of angiotensin II receptors on myocytes in this model of global ischaemia may be a compensatory mechanism ameliorating myocyte contractility in an attempt to sustain ventricular pump function.

Coronary artery constriction in rats affects the activation of alpha 1 adrenergic receptors in cardiac myocytes.

OBJECTIVE: To determine whether alpha 1 adrenergic receptor mediated myocyte contractility and growth are depressed acutely after non-occlusive coronary artery narrowing, the left coronary artery was constricted in rats and mechanical behaviour, cytosolic calcium, and regulation of alpha 1 adrenergic receptors were examined in myocytes seven days later. METHODS: Coronary artery stenosis was surgically induced in rats and following the estimation of global cardiac performance myocytes were enzymatically dissociated and radioligand binding studies were performed. In addition, the isotonic contractile performance, cytosolic calcium transients and noradrenaline stimulated inositol phosphate generation in myocytes were measured in the presence of WB 4101 or after chlorethylclonidine treatment. RESULTS: Estimations of cell mechanics in vitro established that peak shortening was decreased by 36% and 18% in left and right ventricular myocytes of coronary stenosed rats. Time to peak shortening was prolonged by 29% in left and 20% in right myocytes, whereas velocity of shortening was decreased by 27% in left myocytes. These alterations were associated with increases in cell length and width, indicative of myocyte hypertrophy. In addition, coronary stenosis was accompanied by reductions in the expression of alpha 1a and alpha 1b receptor subtypes in myocytes. alpha 1 Adrenergic receptor density and noradrenaline stimulated phosphoinositol turnover were decreased by 30% and 34% in left myocytes. alpha 1a Adrenergic receptor subtype mediated cytosolic calcium concentration and myocyte mechanical performance were also impaired in left myocytes only. The alpha 1a adrenergic receptor subtype antagonist WB 4101 abolished noradrenaline stimulated inositol phosphate generation in myocytes, whereas chlorethylclonidine at large doses only partially inhibited this response. CONCLUSIONS: In conclusion, coronary narrowing leads to defects in the regulation of alpha 1 adrenergic receptors on myocytes which are coupled with attenuation in the transmission of signals, possibly affecting myocyte cell function and ongoing reactive cellular hypertrophy.

Characterization of anti-HLA class II monoclonal antibody LGII-612.14 reacting with formalin fixed tissues.

mAb LGII-612.14 derived from a BALB/c mouse immunized with interferon-gamma (IFN-gamma) treated cultured human B lymphoid cells LG-2 has been shown with serological and immunochemical assays to recognize a monomorphic determinant expressed on the beta chain of HLA-DR, -DQ and -DP antigens. The linear nature of the determinant, which is likely to be formed by residues 19-25, is indicated by the reactivity of mAb LGII-612.14 with HLA-DR, -DQ and -DP beta chains purified by electrophoresis in presence of SDS. An unusual characteristic of mAb LGII-612.14 is its reactivity with fixed tissue sections. The intensity of staining is affected by the incubation temperature, the incubation time and the fixative used. Maximal intensity of staining of formalin fixed, paraffin embedded tissue sections required an incubation time of 16 h. The intensity of staining of paraffin embedded tissues initially fixed with Bouin's solution, formalin or ethanol was similar to that of frozen tissue sections and stronger than that of tissues fixed with B5 solution. No staining was detected of paraffin embedded tissues fixed with glutaraldehyde or Zenker's solution. Comparison of the staining patterns with mAb LGII-612.14 of frozen and fixed tissue sections showed that the latter substrates provide a superior detail of tissue architecture and cellular morphology without significant loss of sensitivity. Furthermore, comparison of the characteristics of mAb LGII-612.14 with the few previously published anti-HLA class II mAb reacting with fixed tissues indicates that mAb LGII-612.14 stains formalin fixed, paraffin embedded tissues, while mAb 910D7 and TAL-1B5 stain tissues fixed with less commonly used fixatives. Furthermore, mAb LGII-612.14 is likely to yield more sensitive staining results than anti-HLA-DR, -DQ and -DP mAb KUL/05. The present results indicate that mAb LGII-612.14 represents a useful probe to apply immunohistochemical techniques to the analysis of the distribution of HLA class II antigens in fixed tissues. This will greatly facilitate the use of readily available collections of fixed tissue specimens in retrospective studies to assess the clinical significance of changes in HLA class II antigen expression which occur in various disease states.

Human hepatic 3 alpha-hydroxysteroid dehydrogenase: possible identity with human hepatic chlordecone reductase.

3 alpha-Hydroxysteroid dehydrogenase is a cytosolic, monomeric, NADPH-dependent oxidoreductase which reduces 3-keto-5-dihydrosteroids to their tetrahydro products. We present here the first partial amino acid sequence data for the human liver enzyme and show these sequences to be identical to the deduced amino acid sequence for human hepatic chlordecone reductase. In addition, these two enzymes exhibit similar substrate and cofactor specificities and immunological reactivity. The results suggest that the natural substrates for chlordecone reductase are 3-keto-5-dihydrosteroids and that these two proteins may be identical.

Interspecific DNA-mediated transfer and amplification of a gene specifying a Mr 100,000 human melanoma-associated cell surface glycoprotein.

The gene that encodes the membrane-bound Mr 100,000 human melanoma-associated antigen (MAA) defined by mouse mAb 376.96, a leukocyte and fibroblast interferon-modulated glycoprotein having preferential distribution on melanoma and carcinoma cells, has been transfected into the mouse melanoma cell line B78H1 as a step toward molecular cloning and characterization of the MAA. Primary, secondary, and tertiary B78H1 transfectants expressing the Mr 100,000 MAA gene were generated by treatment with coprecipitated DNA from Mr 100,000 MAA+ human or transfectant mouse cells and they were detected by an indirect RBC rosetting assay. The Mr 100,000 MAA gene was also transferred into K-1735 mouse melanoma cells and into nonmalignant and malignant mouse fibroblast lines. The species immunoprecipitated by mAb 376.96 from human melanoma cells (Mr 100,000) and from mouse melanoma transfectant cells (Mr 97,000-100,000) were both converted to molecule(s) having an Mr of approximately 70,000 by enzymatic removal of asparagine-linked carbohydrate residues. Two independent secondary transformant clones of B78H1 cells express Mr 100,000 MAA antigenicity at levels significantly higher than those observed when one or two copies of the gene are present. Clone Mr 100,000 secondary-A spontaneously overexpresses Mr 100,000 MAA at least 5-fold and has greater than or equal to 10 times elevated levels of putatively Mr 100,000 MAA gene-associated human alu family repeat element (h-alu)-positive restriction fragments relative to "single" copy secondary transfectant cells. Clone Mr 100,000 secondary-B has increased copy number and expression of Mr 100,000 MAA as a consequence of a selective co-amplification procedure which is targeted to a mouse wild type dihydrofolate reductase (dhfr) gene expression vector. This vector was co-introduced into B78H1 cells in addition to the DNA of Mr 100,000 MAA+ primary transfectant cells and the initially selected aminoglycoside phosphotransferase (neo) gene vector. Stepwise selections of a secondary Mr 100,000 MAA+ transfectant clone with increasing concentrations of the dihydrofolate reductase-inhibitory antimetabolite methotrexate led to progressive increases in copy numbers of the introduced dhfr gene and to parallel increases in h-alu sequences, in cellular levels of dihydrofolate reductase protein, and in cellular mAb 376.96 reactivity. Levels of these entities ultimately reached 50-fold, relative to levels expressed prior to amplification. The array of h-alu+ restriction fragments amplified in Mr 100,000 secondary-B cell DNA is very similar to that observed in Mr 100,000 secondary-A cell DNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunogenicity of human melanoma-associated antigens defined by murine monoclonal antibodies in allogeneic and xenogeneic hosts.

The immunogenicity in patients with melanoma, in monkeys, and in rabbits of four human melanoma-associated antigens (MAA) defined by murine monoclonal antibodies was investigated. The latter included the high molecular weight MAA and the (Mr 115,000, 100,000, and 95,000-150,000 MAA. To this end sera from patients with melanoma, from monkeys, and from rabbits immunized with cultured human melanoma cells were tested for their ability to inhibit the binding to cultured human melanoma cells of radiolabeled anti-Mr 95,000-150,000 MAA monoclonal antibody (MoAb) 140.72, anti-high molecular weight MAA MoAb 225.28, anti-Mr 115,000 MAA MoAb 345.134, and anti-Mr 100,000 MAA MoAb 376.96. None of the sera from patients with melanoma significantly inhibited the reactivity of any of the anti-MAA monoclonal antibodies with melanoma cells. Of the sera from the six monkeys immunized with human melanoma cells, two sera significantly inhibited the reactivity with cultured human melanoma cells of both MoAb 345.134 and 376.96, one serum inhibited only that of MoAb 345.134, and the remaining three sera did not inhibit any of the four anti-human MAA monoclonal antibodies. Sera from six of the seven rabbits immunized with cultured human melanoma cells inhibited the binding to melanoma cells of at least one of the four anti-human MAA monoclonal antibodies while the serum from one rabbit immunized with a melanoma cell extract had no effect. Marked differences were found among the individual rabbit sera in their ability to inhibit the binding of the four anti-human MAA monoclonal antibodies. Sequential immunoprecipitation experiments corroborated the serological findings obtained with one of the two rabbit antisera tested. These results suggest that the immunogenicity of human MAA in mice may be different from that in patients with melanoma and in other animal species.

Cross-reactivity of murine anti-human high molecular weight-melanoma associated antigen monoclonal antibodies with guinea pig melanoma cells.

To identify melanoma associated antigens (MAAs) shared by human and guinea pig melanoma cells, a battery of murine monoclonal antibodies (MoAbs) to human MAA and an antiserum to S100 protein were tested with four newly established guinea pig melanoma cell lines. Only the monoclonal antibodies 149.53 and 225.28 which recognize distinct determinants of the human high molecular weight-MAA (HMW-MAA) reacted with all four guinea pig melanoma cell lines. To compare the binding site of MoAbs 149.53 and 225.28 with guinea pig and human melanoma cells, inhibition binding experiments were performed with antiidiotypic monoclonal antibodies which completely inhibit the binding of MoAbs 149.53 and 225.28 to human melanoma cells. The binding of MoAb 149.53 to guinea pig melanoma cells was partially inhibited by antiidiotypic MoAbs MF9-10 and MK1-180 which recognize distinct private idiotopes within the antigen combining site of MoAb 149.53. On the other hand the binding of MoAb 225.28 to guinea pig melanoma cells was completely inhibited by antiidiotypic MoAbs MF11-30 and TK1-F2 which recognize distinct private idiotopes within the antigen combining site of MoAb 225.28. These results suggest that the determinant recognized by MoAb 149.53 on guinea pig melanoma cells is similar but not identical to that recognized on human melanoma cells, while the determinants recognized by MoAb 225.28 on the two types of cells do not display any detectable differences under the experimental conditions tested. The target structure on the guinea pig melanoma cells identified by MoAbs 149.53 and 225.28 is a Mr 280,000 molecule which has the same apparent molecular weight as one of the two subunits of the HMW-MAA synthesized by human melanoma cells. Sequential immunoprecipitation experiments with guinea pig melanoma cells showed that the determinant recognized by MoAb 149.53 is expressed on a subpopulation of the molecules recognized by MoAb 225.28. Immunohistochemical staining with MoAb 225.28 of a variety of different tissues from normal adult guinea pigs showed that the corresponding antigenic determinant is detectable only in basal cells of epidermis and hair follicles of skin. S100 protein, which is a cytoplasmic constituent of normal human melanocytes, benign nevi, and malignant melanocytes, was also detected in the cytoplasm of the four cultured guinea pig melanoma cells lines. The results of the present investigation may lead to a better understanding of the phylogenetic evolution of the human HMW-MAA and suggest that guinea pig melanoma may serve as a useful animal model for immunobiological studies and carcinogen-induced tumorigenesis investigations.