In situ analysis of antigens on malignant and benign cells of the melanocyte lineage. Differential expression of two surface molecules, gp75 and p89

Can immunohistochemical markers and mitotic rate improve prognostic precision in patients with primary melanoma?

BACKGROUND

In addition to tumor thickness, several other prognostic parameters have been identified in primary human melanomas. Some are available readily (localization, gender, age, and ulceration). Others must be evaluated with a moderate or even substantial amount of work (mitoses and immunohistochemical markers). This study was undertaken to determine whether this extra effort is justified because it actually improves the precision of prognostic statements.

METHODS

Immunohistologic markers were determined on frozen sections from 691 biopsies of human melanomas with the immunoperoxidase method. Univariate and multivariate Cox regression analyses were performed with metastases and with death as endpoints.

RESULTS

Fifteen parameters were related to disease free survival in univariate Cox regression analysis: tumor thickness, ulceration, localization, gender, age, mitoses, and the immunohistochemical markers very late antigen (VLA)-2, human leukocyte antigen (HLA)-ABC, HLA-DR, NKI-beteb, Mel 14, intercellular adhesion molecule (ICAM-1), K-1-2, G-7-E2, and H-2-4-7. Three of the easily available parameters exhibited independent significance in multivariate Cox regression analysis: tumor thickness, ulceration, and localization. If mitotic rate was included in this model, then it had independent prognostic significance but ulceration was no longer significant. However, the model that included tumor thickness, localization, and ulceration had a slightly higher overall chi-square test score, indicating a better performance compared with thickness, localization, and mitoses. The model that included tumor thickness, localization, and mitoses could not be improved by any of the immunohistochemical markers in this study.

CONCLUSIONS

Nine immunohistochemical markers with established prognostic significance for primary human melanoma were not found to improve a prognostic model that included tumor thickness, localization, and mitoses. If mitoses was replaced by ulceration, then the model performed slightly better, although ulceration was not significant in the presence of mitoses.

Characterization of vitiligo antigens

Patients with vitiligo have circulating antibodies directed in part to pigment cell antigens with MWs of approximately 90, 75, and 40-45 kDs. These antigens are denominated VIT 90, VIT 75, and VIT 40, respectively. To further characterize these "vitiligo" antigens, we examined their relation to antigens defined by a panel of 25 monoclonal antibodies (moab) to pigment cell antigens. We found by immunoprecipitation and SDS-PAGE analysis of 125I labelled, detergent soluble, human melanocyte macromolecules, that 24 (83%) of 29 patients with vitiligo had antibodies to one or more vitiligo antigens vs. 2 (7%) of 28 control individuals. Seventeen of the 25 moabs did not react with any labelled antigen in the same lysate. Of the remaining eight moabs, only four precipitated an antigen that co-migrated with one of the vitiligo antigens. Moab TA99, HMSA-5, and TMH-1 (all directed to the 75 kD tyrosinase-related protein [TRP1]) co-migrated with VIT 75. Moab W6/32 (directed to class I HLA antigen) co-migrated with VIT 40. Immunodepletion studies with vitiligo antibodies selectively depleted the antigen defined by W6/32 but not the antigen defined by TA99 and HMSA-5, indicating that VIT 75 was not the 75 kD tyrosinase-related protein. The vitiligo antigens were easily labelled by the lactoperoxidase technique but poorly labelled with 35S-methionine, suggesting they are expressed on the cell surface. These studies indicate that VIT 90 and VIT 75 differ from antigens defined by currently available moabs to pigment cell antigens. VIT 40 appears to share a cross-reactive epitope, or be tightly bound to, class I HLA antigen.

Presence or absence of melanocytes in vitiligo lesions: an immunohistochemical investigation

There is a long-standing controversy over whether melanocytes in vitiligo lesions are actually lost or are still present but inactivated. Resolving this matter is essential for understanding the underlying pathology and for the development of treatment. Standard methods of detecting melanocytes are based on active melanin synthesis. However, it is possible that inactive melanocytes remain in the lesions. There are no methods presently available to detect such dormant melanocytes. Using a panel of one polyclonal and 17 monoclonal antibodies directed against melanocytic cells (largely selected by the European Organisation for Research and Treatment of Cancer Melanoma Group for diagnostic and therapeutic purposes), we investigated the absence or inactivation of melanocytes in vitiligo by immunohistochemistry. Results using this panel of antibodies on frozen skin sections suggest that melanocytes are indeed absent in the lesions. However, in epidermal split-skin preparations, residual staining was occasionally observed. To determine whether the staining obtained was due to degenerated melanocytes, confocal laser scanning microscopy was used. Immunofluorescent staining using the antibody NKI-beteb confirmed this to be the case. The results presented here strongly suggest that melanocytes are indeed lost in vitiligo lesions.

Molecular genetics of human malignant melanoma

Due to a variety of known and unknown control mechanisms, the human genome is remarkably stable when compared to most other species. The long latency periods of most solid tumors, during which the cell undergoes malignant transformation, are presumably due to this stability. The molecular basis responsible for the induction of genetic instability and the resultant biological characteristics manifest in tumor populations is not well understood. The discovery of both oncogenes and tumor suppressor genes, however, has placed the phenomenon of human genome stability on a more solid conceptual footing. These types of genes clearly place multiple barriers to oncogenic transformation, and traversing these barriers apparently requires both time and the accumulation of genetic defects that cannot be corrected. The evolution of neoplasias can, therefore, be predicted to be due to: (1) consistent and progressive loss of tumor suppressor genes; (2) gene amplification, resulting in the over-expression of proteins that aid in tumor progression; (3) gene mutation, which alters the orderly biochemistry of the normal cell; (4) genes that allow a cell like the melanocyte to escape the confining nature of the epidermis and to invade through the dermis into the circulatory and lymphatic systems in order to disseminate itself to other organs (e.g., proteolytic enzymes, enzyme inhibitors, integrins, metastases genes, chemotactic factors etc.); (5) factors, perhaps such as TGF beta 2, that may impact negatively on MHC antigens and confuse host defense mechanisms; and (6) S.O.S.-type genes, which may be expressed as a direct response to the accumulating damage in an attempt to correct the damage, but that may then become part of the problem instead of the solution. The extraordinary plasticity and instability of the genome of a melanoma cell suggests an inordinate amount of genetic flux. In addition to activating and inactivating various genes, this constant shuffling and rearranging of the genome in neoplasms such as MM may be constantly altering gene dose. Cytogenetic and molecular biological studies have been the Rosetta stone for understanding the etiological relevant genetic events in human cancers. Genetic alterations fundamental to the pathology of MM have begun to be defined. Studies designed to understand these perturbations at the biochemical and organismic level are underway.(ABSTRACT TRUNCATED AT 400 WORDS)

Cell adhesion molecules in neoplastic disease

In a variety of human malignancies, tumorigenesis and the development of metastatic disease are accompanied by changes in the expression of cell adhesion molecules. In carcinomas, normally expressed cell adhesion molecules are lost, or expressed in a functionally altered form, events which may help tumor cells to escape from contact-mediated controls and leave the primary tumor. The development of metastatic potential is, in a number of solid tumors, associated with the expression of new cell adhesion molecules by the tumor cells. These newly expressed cell adhesion molecules appear to mediate tumor cell interaction with leukocytes and endothelium, and may direct dissemination of the tumor cells throughout the body.

The EORTC Melanoma Group exchange program: evaluation of a multicenter monoclonal antibody study

In the framework of the European Organisation for Research and Treatment of Cancer (EORTC), the Immunology and Pathology Subgroups of the Malignant Melanoma Cooperative Group undertook a large multicenter monoclonal antibody (MAb) study. Fourteen laboratories from 7 European countries tested a panel of 23 MAbs for immunohistological staining reactivity for malignant and non-malignant lesions involving the melanocytic lineage. A standardized immunoperoxidase procedure was used and the results were evaluated using a standard protocol and data evaluation form developed in collaboration with the EORTC Data Center. According to this analysis, the antibodies in the panel could be classified into 3 main groups. The first group of MAbs includes those antibodies which stained the majority (greater than 80%) of all primary tumors, irrespective of their Breslow thickness and the majority of metastatic lesions. In addition, these MAbs stained a high percentage of cells within a given lesion. Several antibodies of Group I were likewise reactive with the majority of naevoblasts and with normal melanocytes. The second group of MAbs included antibodies reacting only with a limited number of primary melanomas and metastatic lesions. Antibodies of Group II reacted only weakly, if at all, with normal melanocytes or naevocytes. The percentage of cells within a malignant lesion stained by these MAbs was always rather low. The MAb group III detected surface structures whose expression appeared to be related to tumor progression; they did not react or reacted only weakly with naevi, and they all reacted with a small number of early primary melanomas (less than 0.75 mm). The number of lesions stained increased with increasing Breslow thickness. Our study suggests that the application of a panel of well defined MAbs might be of diagnostic and prognostic value in evaluating malignant melanoma.

The relationship between characteristics of the tumor cells and sex of the patients in primary malignant melanomas

Sex is a well proven prognosticator in primary malignant melanoma. We studied 19 parameters of tumor cells in primary malignant melanoma from 391 patients, the purpose being to determine if melanomas in men and women are alike. Apart from results in thin melanomas, no difference was seen between the sex groups. Thin melanomas showed a significant difference for the melanoma-associated antigen G7-E2 (higher expression in women) and the histocompatibility antigen HLA-DR (higher expression in men). The results suggest that sex-related prognostic differences are due more to host than to tumor characteristics.

Cell adhesion molecules of the immunoglobulin supergene family and their role in malignant transformation and progression to metastatic disease

Cell adhesion molecules (CAMs) of the immunoglobulin supergene family may play important roles in tumorigenesis and the development of metastatic disease. In a variety of human malignancies, tumor progression has been observed to be associated with changes in CAM expression. An early event in colorectal tumorigenesis appears to be the down regulation of a normally expressed CAM, DCC. Over-expression of a second CAM, carcinoembryonic antigen, is associated with colorectal tumors which have a high risk for metastasis development. Several tumors, including Wilms tumors and neuroblastoma, have been found to express a developmentally regulated form of NCAM which inhibits a variety of cell-cell interactions. Malignant cells not only show aberrations in the expression of their CAMS and thus their normal cell-cell interactions, but establish new adhesive interactions. The development of metastatic potential in cutaneous melanoma is associated with the de novo expression of two CAMs, one of which is ICAM-1, a molecule mediating adhesion between the tumor cells and leukocytes.

Structural characteristics of the 5' region of the human ICAM-1 gene

The ICAM-1 glycoprotein, one of the major cellular adhesion molecules, exhibits a diverse and highly regulated tissue distribution. To better understand the regulatory mechanisms underlying its particular expression pattern, we have cloned the ICAM-1 gene from human leukocyte libraries. By hybridization with various DNA probes derived from different regions of the ICAM-1 cDNA, several clones were identified and isolated. Clone HWB 3R1, containing a 15kb DNA insert, was selected for further characterization. The HWB 3R1 clone hybridized with probes corresponding to the 3' as well as the 5' region of the ICAM-1 cDNA and gave rise to ICAM-1 expression after transfection into the ICAM-1 deficient MJP17 melanoma cell line. The identity of the expressed ICAM-1 was verified by reaction with five different monoclonal antibodies specific for ICAM-1. Sequence analysis of about 1.2kb of DNA around the ATG start codon revealed putative binding sites for various transcription factors situated in the 5' untranslated region as well as within the first intron. These include SP-1, AP-1 and NF-kB binding sites as well as interferon and retinoic acid responsive elements.

Monoclonal antibody PAL-M1 recognizes the transferrin receptor and is a progression marker in melanocytic lesions

Monoclonal antibody PAL-M1, which was selected to discriminate between nevocellular nevi and cutaneous melanomas, has not been characterized until now. Here we show that PAL-M1 is directed against the transferrin receptor (CD71). The molecules precipitated by PAL-M1 and by anti-transferrin receptor antibodies OKT9 and 5E9 from various human tumor cell lines (melanoma, hepatoma, and lymphoma) show identical characteristics on SDS-PAGE. PAL-M1 also specifically recognized mouse L cells expressing the human transferrin receptor gene. Competition experiments demonstrated that PAL-M1 and OKT9 recognize the same or a spatially close determinant. Immunohistochemical staining of a large series of melanocytic lesions indicates that the transferrin receptor can be considered as a progression antigen in this type of lesion.

Antigen dynamics in melanocytic and nevocytic melanoma oncogenesis: anti-ganglioside and anti-ras p21 antibodies as markers of tumor progression

Based on melanoma pathogenesis, phenotypic dynamics in pigment cell tumor progression detected with 11 MoAb have been defined. Anti-melanosomal A4F11 antibody reacts with every type of pigment cell tumor tested except for a few specimens. TNKH1 and anti-K.1.2 antibodies recognize nevocytic benign to premalignant tumors. HLA-DR, A.1.43, and A.10.33 antigens are expressed in advanced melanomas. Staining with anti-ganglioside GM3 and GD3 antibodies, M2590 and 4.2, respectively, reveals that most pigment cell tumors express gangliosides GM3 and GD3. But A2B5 antibody, which detects some polysialogangliosides such as GQ1C, reacts with highly progressed melanoma cells. Anti-ras p21 antibodies, RASK-3 and RASK-4, react with malignant melanomas and their premalignant lesions. These findings suggest the following: A4F11 is a universal marker of pigment cell tumors. TNKH1 and anti-K.1.2 antibodies might not be markers of melanocytic tumors but of nevocytic benign to premalignant tumors. Melanoma cells express gangliosides GM3 and GD3 as common pigment cell antigens and synthesize aberrant polysialogangliosides. Anti-ganglioside MoAb, including A2B5, are possible markers of the level of malignancy in melanoma cells like anti-A.1.43 and anti-A.10.33 antibodies. Enhanced ras p21 expression already appears on premalignant pigment cells.

Oncofetal antigen in Xiphophorus detected by monoclonal antibodies directed against melanoma-associated antigens

Monoclonal antibodies (MAbs) directed against Xiphophorus melanoma cells were developed and tested by indirect immunofluorescence and immunoperoxidase staining for reactivity with a panel of 15 allogeneic tissues and 12 allogeneic cell lines. The reactivity of such MAbs was restricted to melanoma cells from tumor biopsies and melanoma-derived cell lines. In addition, all embryonic cells of all histiotypes from developmental stages later than mid-organogenesis and from corresponding short term in vitro cultures reacted with these MAbs. In contrast, normal tissues and organs from adult fish displayed no reactivity, thus implying that the melanoma-associated antigens detected by the MAbs described are oncofetal antigens.

Preclinical and phase I studies of monoclonal antibodies in melanoma: application to boron neutron capture therapy of melanoma

Monoclonal antibodies (MAbs) provide an attractive method of selectively localizing sufficient boron atoms around tumour cells to capture neutrons. Assuming that 10(8)-10(10) 10B atoms are needed for one capture event and that 10(3)-10(4) atoms can be coupled to each antibody molecule, then 10(5)-10(6) antibody molecules gathered on an individual cell will destroy that cell. Binding to normal tissues, on the other hand, would need to be at least 20-fold less than that to tumour tissues to avoid toxic effects of neutrons on surrounding tissues. Preclinical studies in animals show that several MAbs may bind to melanoma cells in sufficient quantities in vitro to localize the required amount of Boron per cell. Whether this will occur in vivo, however, may depend not only on antigen density but a variety of other properties of the tumour cells and MAbs. These include the Ig class and affinity of the antibody and whether the antibody is internalized into the tumour cell. The ratio of uptake between tumour and normal tissue is governed by such factors as the percentage of tumour cells within a tumour expressing the antigen and whether the MAb react with normal tissues. Use of Fab or F(ab)2 preparations of the MAb may increase the uptake ratio by preventing uptake of MAb by cells with Fc receptors. In contrast to preclinical animal studies, tumour/normal tissue uptake ratios in phase I studies in humans have been disappointingly low.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of 7F7-antigen, a human adhesion molecule identical to intercellular adhesion molecule-1 (ICAM-1) in human carcinomas and their stromal fibroblasts

The 7F7-antigen is a widespread 85-kDa membrane adherence molecule involved in heterotypic adhesion between PHA-blasts and fibroblasts. Immunofluorescence analysis of COS cells transfected with clone pICAM-I indicated that 7F7-antigen is identical with ICAM-I, the ligand for the contact molecule LFA-I. We have investigated the expression of ICAM-I on several human carcinomas. Tumor cells in most carcinomas, with the exception of squamous-cell carcinomas, expressed very little ICAM-I or none at all. In contrast, marked expression of this molecule was observed on fibrous tissue in the vicinity of carcinoma cells, its intensity correlating with lymphatic infiltration in these tumors. We also examined the expression of ICAM-I on carcinoma cell lines and its induction by treatment with interferon-gamma (IFN-gamma). The inducibility of ICAM-I expression on cultured fibroblasts by several lymphokines suggests that the expression of ICAM-I in the vicinity of carcinoma cells is effected by lymphokines produced by activated lymphocytes/macrophages within the tumor.

Immunohistologic evidence for the malignant potential of congenital melanocytic nevi

Monoclonal antibodies (MoAbs) against six well-defined progression-associated melanoma antigens (PAMAs) and a MoAb against the nuclear proliferation-associated antigen Ki67 were used for an immunoperoxidase study on 44 biopsies from 36 congenital melanocytic nevi (CMN). Twenty-nine common acquired nevi and 16 metastasizing primary melanomas were studied as controls. Two CMN of the series were giant CMN (greater than 20 cm), one of which later progressed to metastasizing melanoma. Of the remaining 34 CMN, four were histologically associated with a malignant melanoma. DNA flow cytometry was performed on adjacent cryostat sections of 37 biopsies from 28 CMN without melanoma. PAMAs were found expressed in CMN in the following frequencies: A-1-43: 36%; P358: 27%; PAL-M1: 20%; HLA-DR: 9%; Muc 18: 2%; A-10-33: 0%. No PAMAs were present in only 15 biopsies (34%). One single PAMA was found in 20 lesions (45%), and two or more PAMAs in nine lesions (21%). In all four CMN histologically associated with melanoma, and also in one biopsy from the giant CMN which later progressed to melanoma, at least two PAMAs were expressed. The latter biopsy was the only CMN in which the proliferation-associated antigen could be demonstrated. Only this biopsy and a single biopsy of the other giant CMN showed aneuploidy. We found expression of single PAMAs and co-expression of PAMAs in CMN in higher frequency than in common acquired melanocytic nevi. Co-expression of PAMAs was a feature of metastasizing primary melanomas. We conclude that co-expression of two or more PAMAs in a CMN might indicate its malignant potential, because this was found in all CMN proven to have progressed to malignant melanoma.

De novo expression of intercellular-adhesion molecule 1 in melanoma correlates with increased risk of metastasis

The 89-kDa cell surface glycoprotein, P3.58, is detectable on advanced human melanomas in situ but not on benign melanocytes or early melanomas. cDNA cloning of P3.58 from melanoma cells was accomplished by screening a lambda zap expression vector library with monoclonal antibodies produced against the denatured antigen. Nucleotide sequencing of the clones revealed that P3.58 is identical to the intercellular-adhesion molecule 1. No qualitative differences in P3.58 mRNA species could be seen between melanoma cells and hematopoietic cells and no differences in gene organization were observed between peripheral blood leukocytes and melanoma cells. Inspection of the deduced amino acid sequence of P3.58 indicated the presence of the consensus sequence characteristic for complement-binding proteins. The acquisition of this cell-adhesion molecule during the process of tumor progression is speculated to contribute to the development of metastasis in melanoma.

The tumor progression-associated human melanoma antigen P3.58 mediates monocyte-lymphocyte interactions in vitro

The melanoma-associated antigen P3.58 is rarely found on benign proliferating melanocytes but is consistently expressed on advanced malignant melanomas which have a high probability of metastasis. Previous studies have shown that its expression on normal tissues is limited to vascular endothelia and lymphoid follicle germinal centers and that it is also expressed by activated monocytes in vitro. In the studies reported here, anti-P3.58 monoclonal antibodies (mAb) were shown to partially inhibit antigen-specific and anti-CD3-induced T cell proliferation and to completely block a lymphocyte/monocyte clustering which occurs in the absence of added antigen. This inhibition is highly specific for P3.58 mAb and was not affected by mAb directed to major histocompatibility complex or T cell antigens. P3.58 therefore seems to be involved in an antigen-independent attraction or adhesion of lymphocytes. P3.58 is the second example (HLA-DR being the first) of an association between the expression of an immune function-associated molecule and the development of metastatic disease in melanoma.

Individual epitopes of an 85,000 MW membrane adherence molecule are variably expressed on cells of different lineage

The recently reported 85,000 MW membrane activation antigen, provisionally termed 7F7 antigen, is involved in the initiation of T-cell responses, in the binding of C3b-coated sheep erythrocytes to B cells and in the phorbol ester-induced aggregation of U937, suggesting that it represents a membrane molecule important for cell-cell adherence. Three new monoclonal antibodies were raised against the purified antigen and used to examine the expression of individual epitopes on cells of different lineage. All antibodies reacted with the purified membrane antigen on Western blots. Antibodies 7G2 and 7C6 reacted only weakly with activated T cells, although the 85,000 MW 7F7 antigen is recognized on T cells by antibodies 7F7 and 8B9. Whereas 7F7 and 8B9 inhibit the phorbol ester-induced aggregation of U937 and the attachment of phytohaemagglutinin (PHA)-activated T cells to fibroblasts, antibody 7G2 was without inhibitory effect. Four antibodies raised against the P3.58 glycoprotein, a melanoma-associated antigen with biochemical features similar to the 7F7 antigen were shown to react with the purified 7F7 antigen on Western blots. These four antibodies also failed to react with activated T cells. In addition, 7F7 bound to a L cell transfectant prepared with human chromosomal DNA which expressed the P3.58 antigen. The results indicate that the 7F7 antigen and the P3.58 melanoma antigen are identical, that some epitopes of this adherence molecule are differentially expressed on individual cell types and that one epitope, which is only weakly expressed on activated T cells, does not contribute to the role of the 7F7 antigen in some examples of cell-cell adherence.

Immunohistochemical demonstration of S-100 protein and melanoma-associated antigens in melanocytic nevi

Thirty-nine melanocytic nevi of varying histologic structure and stages of development were examined for the presence of S-100 protein and melanoma-associated antigens (MAA) by the indirect immunoperoxidase technique, using a polyclonal anti-serum to S-100 protein and monoclonal antibodies to MAA. S-100 protein and MAA were found in the cells of all types of nevi, including dysplastic and congenital nevi. While S-100 protein was present in nevus cells at the epidermodermal junction and at all levels of the dermis, the melanoma-directed monoclonal antibodies BM 24-2, NKI/C-3, Mel-1, and Mel-2 reacted most prominently with the superficial (A-type) nevus cells; the B- and C-type cells being negative in these cells. An exception to this rule was melanoma-monoclonal antibody 34.1 which reacted with nevus cells at all levels; deep C-cells often being more intensely stained than the subepidermal A-cells. The cells of the different nevus cell layers, known to differ morphologically and enzymatically, are, thus, also different in their expression of MAA. Our data suggest that for most antibodies these variations may be due to differences in the metabolic activities of nevus cells at various distances from the epidermis.

Differential expression of HLA-DR, DQ, and DP antigens in primary and metastatic melanoma

Fifty-five primary and 33 metastatic surgically removed melanoma lesions were stained in indirect immunoperoxidase with anti HLA-DR, DQ, and DP monoclonal antibodies and with the monoclonal antibody CL203.4 to a 96-K melanoma associated antigen (MAA). The latter antigen may represent a marker to monitor susceptibility of melanoma cells to modulation by IFN-gamma, because it is highly susceptible to induction by IFN-gamma. In primary melanomas 44%, 29%, 10%, and 55% of the lesions tested were evidently stained by anti HLA-DR, DQ, DP, and 96-K MAA monoclonal antibodies, respectively. A statistically significant association (P less than 0.01) was demonstrated between the degree of intratumoral lymphocytic infiltrate and the expression of HLA-DR and HLA-DQ antigens. In addition, a high degree of concordance in the reactivity pattern of individual lesions stained for HLA-DR antigens and for the 96-K MAA was found. In metastases 64%, 33%, 47%, and 100% of the lesions tested were evidently stained by anti HLA-DR, DQ, DP, and 96-K MAA monoclonal antibodies, respectively. This study indicates that HLA-DR and HLA-DP antigens are expressed in a higher percentage of metastatic than of primary melanomas and that there is no marked difference in the expression of HLA-DQ antigens between primary and metastatic melanomas. The data suggest that the regulatory mechanisms which control the expression of HLA-DR and DP antigens in primary and metastatic melanoma lesions are different. Locally produced IFN-gamma may play a role in the regulation of HLA Class II antigens in primary melanomas.

Glycoprotein P3.58, associated with tumor progression in malignant melanoma, is a novel leukocyte activation antigen

The P3.58 antigen is defined by monoclonal antibodies (MAbs) selected to discriminate between benign and malignant melanocytic cells. Its expression in malignant cells has been shown to correlate with an increased risk of metastasis. A survey of a wide range of tissues revealed that, on normal tissue, expression of P3.58 antigen is restricted to a subset of cells involved in the immune response. The antigen was found not only on certain endothelia, but also on activated macrophages in vivo and in vitro and as well as on activated B lymphocytes. A comparison with known B-lymphocyte and leukocyte activation antigens indicated that P3.58 is a novel leukocyte activation antigen. Biochemical analysis of the P3.58 antigen isolated from cells of different histogenic origin indicated that different molecular forms of the antigen exist, apparently depending on the cell type of origin. P3.58 molecules precipitated from tunicamycin-treated cells were identical in all cell types, suggesting that the variation observed is due to variable N-glycosylation.

Inflammatory cell infiltrates in human melanoma at different stages of tumor progression

Progression of human melanoma is associated with changes in antigenic phenotypes of tumor cells. To establish whether inflammatory infiltrates in progressing melanoma also change, we studied 146 cutaneous melanomas at different stages of progression. Monoclonal antibodies (MAbs) against lymphocyte and macrophage subpopulations, interleukin-2 receptor (IL-2 R), immune interferon (IFN-gamma), and the IFN-gamma-inducible, progression-associated melanoma antigens HLA-DR and gp89 were applied in situ. During the course of melanoma progression, decreased amounts of peritumoral T cells, IL-2 R-expressing lymphocytes and dermal T6+ dendritic cells were found, while increased numbers of intratumoral T cells, inflammatory (27E10+) and mature (25F9+) macrophages were associated with local progression of primary melanomas. In metastases, most infiltrate components except 25F9+ macrophages were rare. Positive correlations were observed between: (1) dermal T6+ cells and IL-2 R+ lymphocytes, and (2) presence of IFN-gamma in the infiltrate and HLA-DR and gp89 antigens on tumor cells. In all stages, HLA-DR expression on tumor cells was correlated with: (1) a shift towards T8+ lymphocytes in the infiltrates and (2) a loss of IL-2 R expression. Our data suggest mutual influences between melanoma cells and mononuclear cell infiltrates in situ.

Expression of the gangliosides GM3, GD3 and GD2 in tissue sections of normal skin, naevi, primary and metastatic melanoma

Expression of the gangliosides GM3, GD3 and GD2 was studied in tissue sections from 19 naevi, 29 primary and 83 metastatic melanoma using the ABC immunoperoxidase technique. GM3 was not detected in normal skin whereas GD2 was detected on the basal and stratum spinosum of the epidermis and on peripheral nerves in the dermis. GD3 was expressed on melanocytes but not on most other components of normal skin. However, GD3 was strongly expressed on epidermis adjacent to naevi and primary melanoma whereas GD2, in contrast to that in normal skin, was not expressed on the epidermis adjacent to 26/29 primary melanoma. All naevi were positive for GM3 and GD3 except that GM3 was not detected on junctional components of naevi. GD2 was not expressed on naevi except in areas showing neuroid differentiation. Studies on melanoma revealed that approximately 60% of primary and 75% of metastatic melanoma expressed GM3 to a varying extent. With 2 exceptions, all primary and metastatic melanomas expressed GD3 although there was variable expression within most of the individual tumours. GD2 was detected in only approximately 25% of primary and 50% of metastatic melanomas. Both GD2 and GD3 were detected on lymphocytes surrounding melanoma. The higher expression of GD2 on metastases compared to primary melanomas was consistent with the view that GD2 expression was associated with increased metastatic potential. However, the low proportion of metastases expressing GD2 and the absence of any correlation with thickness of the primary tumour suggested that GD2 expression was not a reliable marker of metastatic potential. No differences could be detected in ganglioside expression on metastases in skin or lymph nodes. These results appear to have implications for the use of MAbs against gangliosides in therapy of melanoma and in the study of melanocytic differentiation.

Cell surface antigens of human melanocytes and melanoma. Expression of adenosine deaminase binding protein is extinguished with melanocyte transformation

It has been proposed that the pathogenesis of melanoma proceeds through multiple stages, ranging from benign proliferation of melanocytic cells to acquisition of the capacity to invade tissues and metastasize. During investigations of cell surface antigens expressed by melanocytes and melanoma, we identified an antigen system that was expressed by cultured normal melanocytes but not by melanoma cell lines. mAbs against this antigen detected a 120-kD cell surface glycoprotein on melanocytes. This molecule had been identified previously as the binding protein for adenosine deaminase (ADAbp). ADAbp was expressed by 51 melanocyte cell lines derived from normal fetal, newborn, and adult skin and adult choroid, but not by 102 melanoma cell lines derived from primary and metastatic lesions. Studies with radiolabeled bovine adenosine deaminase, confirmed that melanocytes expressed binding sites for adenosine deaminase, but no binding sites were detected on cultured melanoma cells. Further studies showed that ADAbp+ melanocytes became ADAbp- upon malignant transformation in vitro. Immunohistochemical studies on a panel of frozen tissues demonstrated reactivity of anti-ADAbp mAbs with epidermal melanocytes and benign junctional nevi, but not with potentially premalignant dysplastic nevi or primary/metastatic melanoma lesions. These studies demonstrate that ADAbp expression is lost with malignant transformation of melanocytes, presumably at an early stage in the transformation process.

Immunohistochemical Localization of Melanoma-Associated Antigen p94 kd200 with the Use of a Modified Avidin-Biotin-Complex Lectin Method

The immunohistochemical localization of melanoma-associated antigen p94 kd200 was investigated in frozen sections of 3 congenital nevi, 4 benign intradermal nevi, 1 regressing nevus, 1 blue nevus, 1 dysplastic nevus, 1 lentigo maligna, 1 superficial spreading melanoma and 2 metastatic melanomas. The original avidin-biotin complex lectin method (Hsu SM, Raine L, Fanger H: Am. J. Clin. Pathol., 75: 734–738, 1981) was modified to detect the antigen. The sections were exposed to the monoclonal antibody to p94 kd200 (Hybritech Inc.), the linking biotin-labelled anti-mouse IgG, the avidin-biotin peroxidase complex and the 3-amino-9-ethylcarbazole solution in an incubator at 37 °C and 100% humidity. We found that the percentage of cells expressing p94 kd200 varied between 0 and 100% in congenital nevi, between 80 and 100% in benign intradermal nevi, between 0 and 20% in the regressing, blue and dysplastic nevi, and in the lentigo maligna, 80 to 100% in the superficial spreading melanoma, and between 0 and 40% in the metastatic melanomas. Positive cells were found to be hypomelanotic (did not have heavy melanin content). The intensity of labelling or the degree of antigen expression on benign and malignant hypomelanotic cells was also found to vary. These findings 1) reinforce the concept of quantitative rather than qualitative antigenic differences in benign and malignant cells 2) suggest that kd200 is lost with increasing pigment production 3) offer a potentially significant tool to investigate the antigenic changes during cell differentiation.

Immunohistological evaluation of MHC class I and II antigen expression on nevi and melanoma: relation to biology of melanoma

MHC antigen expression on 20 nevi, and 35 primary and 95 metastatic melanomas was studied by immunoperoxidase techniques using monoclonal antibodies to identify the antigens on frozen tissue sections. DR antigens were not detected on nevi but were detected on 71% of primary melanomas and 56% of metastases, suggesting that this antigen may be a useful marker of malignant transformation of nevi. Expression of class II antigen could not be related to other prognostic histological features of primary melanoma such as tumour thickness, but comparison of the common phenotypes of primary and metastatic melanoma suggested that expression of DR antigens alone in the absence of DP, DQ and ABC antigens may be an indicator of metastatic potential. Class I (HLA-A,B,C) antigens were also expressed infrequently on nevi but were detected on 43% of primary melanomas and 34% of metastases. HLA-A,B,C expression was inversely related to thickness of the primary melanoma. This as well as the lower expression of class I antigens on metastases, may indicate that growth and spread of melanoma may be inhibited by MHC (class I) dependent cytotoxic T cell responses. Expression of class I MHC antigens was unrelated to class II antigens. Expression of DR was more common than DP or DQ, but the latter with one exception, were not expressed in the absence of DR antigens. Significant differences were not found in MHC antigen expression on metastases in lymph nodes compared to those in subcutaneous sites, but further studies are needed to determine whether such differences may exist between metastases in other visceral sites.

Heterogeneous expression of melanoma-associated antigens in uveal melanomas

Twenty-five uveal melanomas were stained with seven monoclonal antibodies (MoAbs) recognizing different antigens on cutaneous melanomas. A two step immuno-peroxidase procedure was used. Phenotypic heterogeneity was observed for four MoAbs (M.2.2.4, AMF-7, 225.28S, PAL-M1) while two MoAbs (NKI-beteb, CL203.4) reacted strongly with most (85%) uveal melanomas, and one MoAb (R-24) showed very low reactivity. Despite heterogeneity, co-expression of some antigens was observed. Expression of the antigen recognized by MoAb M.2.2.4. was significantly lowered by pre-enucleation irradiation while the other antigens remained unchanged. Expression of antigens on uveal melanomas differed markedly from primary cutaneous melanomas. The clinical relevance of these findings awaits further study.

Tumor progression in human malignant melanoma: five stages defined by their antigenic phenotypes

The antigenic profile of melanocytic cells in the course of local and systemic tumor progression of human malignant melanoma was investigated by the reactivity of a panel of monoclonal antibodies (MAbs) in frozen sections of histologically defined melanocytic lesions. Specific antigenic phenotypes made it possible to distinguish 5 groups of lesions which could be ranked in relation to each other due to the sequential acquisition or loss of progression markers. On this basis, a scheme of antigenic changes which accompany the stepwise transformation of normal skin melanocytes into highly malignant metastatic melanoma cells is proposed. The steps of tumor progression identified solely by phenotyping with MAbs were in complete concordance with the concept of melanoma progression derived from histological, statistical and clinical analyses. Furthermore, our finding that the expression of gp89 as well as HLA-DR antigens can be induced by interferon-gamma in vitro provides evidence that immune interferon may play a role in the regulation of genes leading to phenotypic changes in progressing melanoma cells.

The epithelial cell surface antigen 17-1A, a target for antibody-mediated tumor therapy: its biochemical nature, tissue distribution and recognition by different monoclonal antibodies

The antigen defined by MAb 17-1A, raised against colorectal cancer cells and currently used in immunotherapy trials, is a 37 kDa protein containing N-linked glycans as demonstrated by inhibition of glycosylation with tunicamycin. The 17-1A antigen (17-1A Ag) is broadly distributed in normal epithelial tissues and is also found in various types of carcinoma. Quantitative differences in expression between normal and malignant tissues were only apparent in gastric carcinomas. After immunizing mice with fresh colon carcinoma tissue, 4 MAbs were obtained that showed the same tissue reaction pattern as MAb 17-1A and recognized the 17-1A Ag as judged from precipitation and immunoblotting experiments. MAbs M72 and M74 reacted with an anti-idiotypic serum directed against the original MAb 17-1A and were able to block 17-1A binding. In contrast, M77 and M79 are directed against a different epitope. This makes them potentially interesting for passive immunotherapy in regimens involving a combination of MAbs.

Tumor cell metastasis

Local tissue invasion and the formation of metastatic lesions are characteristic properties of many malignant tumors. The formation of metastases is a complex process involving the passage of tumor cells from the site of the primary bulk tumor through successive connective tissue barriers, ultimately resulting in the growth of secondary tumor cell colonies in distinct target organ locations. At many stages in the metastatic process, tumor cells interact with multiple components of the extracellular matrix. Recently, the importance of basement membrane as a barrier to invasive cells has been recognized. In the course of the transition from in situ to invasive carcinoma, normal or dysplastic epithelial cells residing on a basement membrane are replaced by neoplastic cells which subsequently invade the basement membrane and enter the underlying stroma. Once in the stroma, tumor cells can then penetrate the walls of blood vessels or the lymphatic system and enter into the circulation. Circulating tumor cells next arrest in the lumina of small vessels, invade the vessel wall, and leave the circulation. These cells are now directly exposed to the extracellular matrix of a target organ where they may grow to form secondary tumors. Throughout the metastatic process tumor cells are thus in contact with, and are potentially responsive to, various components of the extracellular matrix. This review provides a survey of the recent advances in our understanding of the interactions of metastatic tumor cells with the extracellular matrix. Specifically, the role of basement membrane as a barrier to metastatic tumor cells is examined.

Phenotypic dynamics of tumor progression in human malignant melanoma

The phenotypic changes in human melanoma cells during the course of tumor progression were studied with monoclonal antibodies (MAbs) against the melanoma-associated antigens (MAA) M.2.2.4, H.2.8.10, K.1.2, A.1.43, and A.10.33, and HLA-(A,B,C and D). Cryostat sections of 172 primary melanomas of the skin, 157 melanoma metastases and 56 nevi were investigated with an indirect immunoperoxidase method. Phenotypic heterogeneity was observed within lesions at all stages, and also within different tumors of the same patients. Despite this heterogeneity, principles of antigen expression were found. From the reaction pattern of MAbs, the following classifications of antigens were derived: "constitutive" markers of nevomelanocytic cells (M.2.2.4 and H.2.8.10) were found expressed over a wide range of local and systemic tumors. One MAA, K.1.2 (Suter et al., 1985), that declines with progression of melanoma, was classified as an "early" antigen, whereas MAA that appear in primary melanoma in proportion to invasiveness, and which are expressed in metastases of lymph nodes and visceral organs (A.1.43, and A.10.33), were classified as "late" markers of tumor progression. HLA-antigens were classified as "intermediate" markers, HLA-A,B,C, as an "early-intermediate", and HLA-DR as a "late-intermediate" marker. The occurrence of class II HLA, A.1.43-, and A.10.33-positive tumor cells in primary melanoma indicates a high metastatic potential of tumors, independent of tumor thickness. The data show that local and systemic progression of melanoma is associated with qualitative changes in tumor cells which can be recognized by MAbs.