Inhibition of metastases of a human melanoma xenograft by monoclonal antibody to the GD2/GD3 gangliosides.

A human melanoma variant cell line was obtained from a lung metastasis that arose spontaneously after we inoculated melanoma cells sc into a nude mouse. In this model, IgG2a monoclonal antibody (MAb) ME 36.1 defining the GD2/GD3 gangliosides inhibited melanoma growth at the primary site and metastatic spread of the cells, whereas an IgG1 variant of MAb ME 36.1 inhibited lung metastasis formation only. Possible mechanisms of antitumor effects of MAb ME 36.1 are discussed.

Development of invasive and growth factor-independent cell variants from primary human melanomas.

Growth autonomy and high levels of invasiveness are characteristics of human melanoma cells that are metastatic in vivo. By consecutive passage through a reconstructed basement membrane, we have selected from 5 of 6 primary melanoma cell lines variants which show an up to 10-fold increase in invasiveness. The invasive variants grew more rapidly than the parental, noninvasive cells in serum- and growth factor-free medium and one of the 3 variant cell lines with the highest invasive capacity in vitro metastasized to the lungs when injected s.c. into nude mice. In a second approach, variants of 6 primary melanoma cell lines were clonally selected in medium without exogenous growth factors (protein-free medium). These selected cells showed higher invasive properties in vitro and in vivo than the parental cells. Clones of invasive and growth factor-independent cell variants were heterogenous and changed over time in the absence of selected pressure to a phenotype similar to that of parental nonselected cells. These results indicate that primary melanoma cells contain subpopulations of cells that have the phenotype of an advanced (metastatic) stage of tumor progression, but this phenotype is not stable without selective pressure.

In vitro properties of human melanoma cells metastatic in nude mice.

We have developed a human melanoma metastasis model in nude mice. In this model, a human variant cell line (451-LU) was obtained that spontaneously metastasized in nude mice. This variant cell line was selected from the lung of a nude mouse after several in vivo passages of human melanoma WM164 cells previously isolated from a melanoma metastasis of a patient. The WM164 cells were not competent for metastasis in nude mice prior to this selection. We compared the phenotypes of the parental nonmetastatic cell line and the metastatic variant with respect to growth at clonal seeding densities in protein-free medium (growth factor independence), in vitro invasion through reconstructed basement membranes, secretion of proteolytic enzymes, expression of tumor-associated antigens, and chromosomal abnormalities. Metastatic 451-LU cells showed significantly increased growth factor independence when grown at clonal seeding densities as compared to the parental cells. In in vitro chemoinvasion assays, metastatic 451-LU cells were significantly more invasive than the parental cells. The metastatic variant secreted collagenase and tissue type plasminogen activator at levels 10- and 3-fold higher than the parental WM164 cells, respectively. Polyclonal antibodies to tissue type plasminogen activator significantly inhibited invasion through reconstructed basement membranes. In metastatic 451-LU cells, expression of nerve growth factor receptor was elevated, both at the protein and transcriptional level. Metastatic cells were aneuploid with a mode of 97 chromosomes, whereas the parental nonmetastatic cells had a mode of 52 chromosomes. Our studies suggest that metastatic melanoma cell variants selected in vivo show increased independence of exogenous growth factors when grown at clonal cell densities, enhanced invasiveness in vitro, greater secretion of proteolytic enzymes, and increased chromosome mode as compared to the nonmetastatic parental cells. The data further suggest that melanoma cells isolated from metastatic lesions and maintained in vitro have an unstable invasive phenotype but that metastatic variant cells can readily be selected.

Expression of melanoma-associated antigens in rapidly dividing human melanocytes in culture.

Conditions were established to induce rapid clonal growth of melanocytes from newborn foreskin. Surface antigen expression was analyzed using monoclonal antibodies derived by immunization of mice with melanoma cell, melanocyte, and placental membrane preparations. Unlike resting melanocytes in normal skin, cultured melanocytes expressed most major melanoma-associated antigens tested, e.g., nerve growth factor receptor, proteoglycan, transferrin-related Mr 97,000 protein antigen, Mr 120,000 protein, and gangliosides 9-O-acetyl GD3 and GD3. HLA-DR antigen and ganglioside GD2 were expressed at very low levels or not expressed. After several subpassages, most melanocyte cultures, including clones and melanocytes, initially sorted by rosetting with monoclonal antibody to nerve growth factor receptor, lost their characteristic bipolar morphology and expression of nerve growth factor receptor and Mr 97,000 antigen but continued to express high molecular weight proteins such as proteoglycan, Mr 130,000/105,000 and 120,000 antigen. The few melanocyte cultures that did maintain their characteristic bipolar to spindle morphology continued to express all melanoma-associated antigens and even began to express HLA-DR antigens. Melanocytes cultured in the presence of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate also maintained their bipolar morphology, were often pigmented, and continued to express melanoma-associated antigens for several passages; they did not express HLA-DR antigen. Our studies indicate that rapidly proliferating melanocytes in culture undergo antigenic changes associated with malignancy.

Growth and phenotypic characteristics of human nevus cells in culture.

Nevus cells were isolated from the three cutaneous components, epidermis, basal layer, and dermis, of nonmalignant pigmented lesions and were cultured separately in the presence or absence of the phorbol ester 12-0-tetradecanoyl phorbol-13-acetate in medium that supports the rapid proliferation of melanocytic cells. The separation procedure used provided cultures that were essentially free from normal melanocytes (dermis) or fibroblasts (epidermis). In short term culture, nevus cells of all skin compartments expressed markers associated with differentiated melanocytes, such as presence of premelanosomes and melanosomes and elevated tyrosinase levels. Nevus cells also expressed melanoma-associated antigens, such as NGF-receptor, transferrin-related p97, proteoglycan, and HLA-DR as detected with monoclonal antibodies. After several subpassages, cells showed a decreased expression of melanoma-associated antigens, decreased tyrrosinase levels, and melanosomes could no longer be detected. Morphologically, these cells were similar to fibroblasts. The disappearance of melanoma-associated cell surface antigens was concomitant with the appearance of a melanocyte-associated 145 kd protein that might serve as a marker of fibroblast-like differentiation in nevus cells and normal melanocytes. Nevus cell cultures grown in the presence of 12-0-tetradecanoyl phorbol-13-acetate maintained a stable differentiated phenotype throughout their lifespan. As reported earlier, nevus cells in culture, irrespective of the presence or absence of 12-0-tetradecanoyl phorbol-13-acetate, have a finite lifespan in vitro, grow anchorage-independent in soft agar, but do not form tumors when xenografted to nude mice. These studies demonstrate that nevus cells isolated from the epidermal, basal layer, and dermal components of lesional skin can serve as models to characterize the initial steps of tumor progression in a human cell system.

Aggressive fibromatosis of the breast.

Fibromatosis of the breast results in aggressive, infiltrative lesions with a propensity for local recurrence. We describe an unusual case of fibromatosis producing a growth resembling carcinoma in a 39-year-old woman. Recognizing this infrequently encountered condition is important to avoid unnecessary radical surgery.

Lichen amyloidosus. Ultrastructure and pathogenesis.

The ultrastructure of six cases of lichen amyloidosus was studied with special attention to epidermal keratinocytes and the role of tonofilaments as precursors of fibrils of amyloid. Through the process of apoptosis, keratinocytes undergo degeneration and become filamentous cells and then filamentous masses or Civatte bodies. These bodies then drop into the dermis through a damaged basement membrane. In the papillary dermis, islands of amyloid become closely associated with Civatte bodies. In some cases, conversion to straight nonbranching filaments, characteristic of fibrils of amyloid, was found within whorled, densely packed filamentous masses. The transformation into fibrils of amyloid was not observed in keratinocytes or Civatte bodies situated in the epidermis. This final step of conversion may be aided by dermal fibroblasts that are frequently lodged around deposits of amyloid.

Nucleolar organizer regions in superficial spreading melanoma with nodule.

Nucleolar organizer regions (NORs) are genes coding for the ribosomal RNA; they also induce the formation of the nucleolus at interphase. Transcriptionally active NORs can be visualized in histological sections with a silver colloid method, allowing direct counting of these structures (so-called AgNORs). Seven superficial spreading melanomas with nodule (i.e., melanomas containing both a radial and a vertical growth phase) were studied with the technique. The nuclear AgNOR counts (mean +/- SEM) were 5.44 +/- 1.70 for the radial growth phase and 7.65 +/- 2.35 for the vertical growth phase (P less than 0.01). This difference in mean nuclear AgNOR numbers may be related to other known differences in the biological behavior of the two growth phases.

Transformation of normal human melanocytes and non-malignant nevus cells by adenovirus 12-SV40 hybrid virus.

Infection of normal human melanocyte and nevus cultures with an adenovirus 12-Simian Virus 40 hybrid virus (Ad12-SV40) produced transformed cells that expressed SV40-T antigen. The Ad12-SV40 cells exhibited rapid cell proliferation to high cell densities and efficient growth in soft agar, but none of 15 transformed melanocyte and nevus cultures formed tumors when injected s.c. or under the renal capsule into athymic nude mice. While the Ad12-SV40-transformed cells lost certain properties associated with the melanocytic phenotype, i.e., pigmentation, tyrosinase activity and melanosome content, the expression of melanoma-associated antigens, including nerve growth factor receptor, p97 melano-transferrin, and chondroitin sulfate proteoglycan, remained stable. The transformed melanocytes acquired the ability to express HLA-DR antigen, which is found on nevus and melanoma cells. Total ganglioside patterns in Ad12-SV40-transformed cells changed to reflect more advanced stages of tumor progression. Transformed melanocytes, like nevus and melanoma cells, showed increased GD3 content and transformed nevus cells increased GD2 which is a feature of malignant melanoma cells. Ad12-SV40-transformed human melanocytes and nevus cells are useful tools for studying tumor progression under experimental conditions.

Regulatory factors that determine growth and phenotype of normal human melanocytes.

Normal human melanocytes, unlike malignant melanoma cells, required at least three growth-promoting agents, i.e., phorbol ester for protein kinase C activation and the growth factors basic fibroblast growth factor (bFGF) and insulin, for growth in chemically defined W489 medium. Cell growth was further stimulated by addition of agents that increase intracellular levels of cyclic adenosine 3',5'-monophosphate (cAMP) to the medium. Among these agents, the pituitary hormones alpha-melanocyte-stimulating hormone (alpha-MSH) and follicle-stimulating hormone were the most potent, whereas bacterial toxins, including cholera, tetanus, and pertussis toxin and their subunits either were less mitogenic or gave variable results depending on the culture tested. Medium containing phorbol ester PMA, growth factors bFGF and insulin (or insulin-like growth factor-I), and synthetic alpha-MSH supported melanocyte growth for more than 5 months with doubling times between 5 and 8 days. Two copper-binding proteins, ceruloplasmin and tyrosinase, were mitogenic when added to medium and ceruloplasmic induced a long bi- to tripolar-shape of cells. Addition of 1 mM dibutyryl cAMP to the medium led to the formation of dendrites in all cells, with an average of 28 extensions per cell. Although cell growth was inhibited by dibutyryl cAMP, cells were not terminally differentiated and continued to proliferate. Dendritic melanocytes showed a 2.2-fold increase in activity of the tyrosine kinase pp60c-src. The induction of dendritic processes in melanocytes by dibutyryl cAMP or sodium butyrate was reversible and appears to reflect the expression of the mature melanocytic phenotype in situ.

Immunohistochemical demonstration of actinically damaged elastic fibers in keratoacanthomas: an aid in diagnosis.

The inclusion of elastic fibers within the epithelium of keratoacanthomas is a phenomenon suggested to be an aid in differentiating this lesion from squamous cell carcinoma. Antilysozyme antibodies have recently been noted to stain actinically damaged elastic fibers but not those from sunprotected skin. In this study, 54 keratoacanthomas and 46 squamous cell carcinomas were stained with a histochemical elastic tissue stain and polyclonal antibody to lysozyme using an immunoperoxidase technique. Elastic fibers were demonstrated in keratoacanthomas (37/54, 68%) significantly more often than squamous cell carcinomas (12/46, 26%) (p less than 0.001) using both techniques. This study confirms that the inclusion of elastic fibers occurs significantly more often in keratoacanthomas than squamous cell carcinomas. These elastic fibers were also actinically damaged, suggesting a role for sun damage in the evolution of keratoacanthoma.

Fibroblast cell interactions with human melanoma cells affect tumor cell growth as a function of tumor progression.

It is known from a variety of experimental systems that the ability of tumor cells to grow locally and metastasize can be affected by the presence of adjacent normal tissues and cells, particularly mesenchymally derived stromal cells such as fibroblasts. However, the comparative influence of such normal cell-tumor cell interactions on tumor behavior has not been thoroughly investigated from the perspective of different stages of tumor progression. To address this question we assessed the influence of normal dermal fibroblasts on the growth of human melanoma cells obtained from different stages of tumor progression. We found that the in vitro growth of most (4 out of 5) melanoma cell lines derived from early-stage radial growth phase or vertical growth phase metastatically incompetent primary lesions is repressed by coculture with normal dermal fibroblasts, suggesting that negative homeostatic growth controls are still operative on melanoma cells from early stages of disease. On the other hand, 9 out of 11 melanoma cell lines derived from advanced metastatically competent vertical growth phase primary lesions, or from distant metastases, were found to be consistently stimulated to grow in the presence of dermal fibroblasts. Evidence was obtained to show that this discriminatory fibroblastic influence is mediated by soluble inhibitory and stimulatory growth factor(s). Taken together, these results indicate that fibroblast-derived signals can have antithetical growth effects on metastatic versus metastatically incompetent tumor subpopulations. This resultant conversion in responsiveness to host tissue environmental factors may confer upon small numbers of metastatically competent cells a growth advantage, allowing them to escape local growth constraints both in the primary tumor site and at distant ectopic tissue sites.

Biology of tumor progression in human melanocytes.

Tumor progression in the human melanocyte system can be delineated into 6 sequential stages. The first three steps represent nonmalignant melanocyte lesions from focal proliferations of structurally normal melanocytes to lesions with architectural and cytologic atypia. Primary melanoma may be divided into radial growth phase without competence for metastasis and vertical growth phase with metastatic competence. Melanocytes isolated from normal skin, nonmalignant pigmented lesions, and melanomas and maintained in culture have properties that are characteristic for each stage of tumor progression. Cytogenetic studies revealed nonrandom chromosomal abnormalities of advanced melanomas involving chromosomes 1, 6, and 7. Recent progress in tissue culture techniques has allowed studies of growth regulation of normal and malignant cells. Six growth factor receptor-growth factor systems seem to be of biologic significance in the melanocyte system: EGF, NGF, FGF, PDGF, insulin, and beta-TGF. Monoclonal antibodies have characterized a large number of antigens on melanocytes of the various stages of tumor progression, making melanoma one of the most widely studied human tumor systems.

Lymphomatoid granulomatosis.

The clinical and pathologic appearance of seven patients with lymphomatoid granulomatosis who had skin lesions when first seen is reviewed. Six patients subsequently developed systemic disease. Although the gross morphology of the skin lesions is variable, the pathology is distinctive. An adequate deep biopsy shows the characteristic lymphohistiocytic infiltrate with variable numbers of atypical cells. Angiodestruction is less evident in the skin compared to other organs. The infiltrate surrounds and invades not only vessels but also nerves and epidermal appendages. The skin biopsy specimen can be differentiated from the lymphomatous infiltrates and Wegener's granulomatosis. Two of the patients who developed systemic disease were diagnosed by skin biopsy but clinicians failed to institute therapy, preferring to wait for other organ involvement. In addition, two patients developed lymphoma, one of which was confirmed at autopsy and one on subcutaneous and bone marrow biopsy 5 years after the initial skin diagnosis. Lymphomatoid granulomatosis can be diagnosed by performing a skin biopsy. Appropriate chemotherapy may result in a high percentage of complete remissions and therefore the dermatopathologist can play an important role in the early diagnosis of this potentially fatal disease.