Disseminated melanoma, preclinical therapeutic studies, clinical trials, and patient treatment

A human melanoma cell line transduced with an interleukin-4 gene by a retroviral vector releases biologically active IL-4 and maintains the original tumor antigenic phenotype

Experimental models of vaccination with tumor cells engineered to produce interleukin-4 (IL-4) have shown that the local release of this cytokine is associated with the development of antitumor immunity that may induce regression of established cancer. The aim of this study was to transduce a human melanoma cell line with the gene coding for human IL-4, and to analyze cytokine production, phenotypic characteristics, and antigen expression after transduction. A retroviral vector, constructed by inserting IL-4 cDNA into the LXSN vector, was used to infect the human melanoma cell line Me14932, known to express the MHC class I HLA-A2 and the melanoma-associated antigen Melan-A/MART-1, recognized by HLA-A2-restricted T-cells. The confluence of all G418-resistant cells (Me14932/IL-4) was then analyzed for proviral integration and IL-4 mRNA expression. Substantially stable IL-4 release was detected by ELISA in the supernatant of transduced cells, ranging from 1.6 to 4.6 ng/ml per 10(5) cells per 24 hr; such a cytokine displayed a specific biologic activity, as revealed by the stimulation of blast cell proliferation and the inhibition of lymphokine activated killer cell (LAK) induction by IL-2. After 200 Gy irradiation, IL-4 release remained detectable for 5 weeks, whereas cell proliferation ceased within 7 days. Morphology and immunophenotypic characteristics of the parental cell line (expression of MHC classes I and II, ICAM-1, LFA 3, melanoma-associated antigens, etc.) were retained by the IL-4 gene-transduced melanoma as assayed by microscopy and immunofluorescence; likewise, susceptibility to lysis by LAK cells as well as a T-cell clone recognizing the Melan-A/MART-1 antigen did not change. These results, together with the lack of replication-competent retrovirus, suggest that the Me14932/IL-4 cell line displays suitable characteristics for its use in the treatment of HLA-matched melanoma patients.

[Immunotherapy of malignant melanoma. New prospects]

Malignant melanoma is an immunogenic tumor which can induce host humoral and cellular responses, and is a good model for development of anti-cancer immunotherapy. During the last decade systemically-administrated interferon and interleukin-2 have been used. Advances in immunology and molecular biology could allow a more specific and active immunotherapy. Perspectives include chemo-immunotherapy, monoclonal antibodies alone or in combination with cytotoxic agents, adoptive immunotherapy with tumor-infiltrating lymphocytes (TIL), gene therapy designed to increase tumor immunogenicity, and active immunotherapy with vaccines.

Lymphocyte-melanoma interaction: role of surface molecules

The coexistence of tumor-specific immunity with a progressing tumor is observed in most experimental systems and remains one of the major paradoxes of tumor immunology. Expression of several surface molecules on melanoma cells, e.g., intercellular adhesion molecule 1 (ICAM-1) or major histocompatibility complex (MHC) class II, has been associated with an aggressive tumor growth and an reduced host antitumor response. HLA class I expression is also frequently altered in melanoma compared to melanocytes. Given the central role of these molecules in the restriction of T cell recognition, regulation of tumor HLA class I expression might also be a strategy for the evasion of immune surveillance by the malignant cells. The fact that it is now possible to clone antigen-specific T cells from tumor patients, as well as the relevant autologous tumor cell lines, enabled us to establish a model system to investigate possible tumor escape mechanisms from immunosurveillance. Using this system, we were able to demonstrate that purified soluble ICAM-1 or 12-fold-concentrated cell-free melanoma supernatants, containing shed ICAM-1, were able to inhibit conjugate formation between T cell clones and the autologous melanoma cells as efficiently as monoclonal antibodies against CD11a, Soluble ICAM-1 also abrogated the MHC-restricted killing of the melanoma by T cell clones. We further observed that a number of CD4+ T cell clones and melanoma cell lines established from the same tumors form conjugates with each other, leading to an increase of [Ca2+]i in the T cell clone; however, this interaction failed to induce interleukin-2 production or proliferation of the T cell clone. Furthermore, this interaction rendered the T cell clone unresponsive to subsequent stimulation. All these effects were MHC class II restricted. Therefore, the melanoma was capable of delivering antigen-specific signals to the T cell clone, but did not deliver the costimulatory signals, e.g., a B7/CD28 interaction, necessary for full T cell activation. Transfection of the melanoma with an expression vector containing a B7 cDNA with subsequent B7 expression on its cell surface renders the melanoma a fully competent antigen-presenting cell which is able to induce a nuclear factor binding to the interleukin-2 promoter in the specific T cell clone, followed by enhanced interleukin-2 transcription, synthesis, and T cell proliferation.

Differentiation of cultured human melanoma cells induced by the aromatic fatty acids phenylacetate and phenylbutyrate

The increasing incidence of melanoma and the poor responsiveness of disseminated disease to conventional treatments call for the development of new therapeutic approaches. Phenylacetate, a nontoxic differentiation inducer, can suppress the growth of other neuroectodermal tumors, i.e., gliomas, in laboratory models and in humans. This finding led us to explore the efficacy of phenylacetate and related aromatic fatty acids in melanoma. Phenylacetate and phenylbutyrate were found to a) induce selective cytostasis and maturation of cultured human melanoma cells, b) modulate the expression of genes implicated in tumor metastasis (type IV collagenase and tissue inhibitor of metalloproteinases-2) and immunogenicity (HLA class I); and c) enhance the efficacy of other agents of clinical interest, including retinoids, interferon-alpha, suramin, and 5-aza-2'-deoxycytidine. Reflecting on the phenotypic heterogeneity of melanoma, the degree of biologic alterations induced by phenylacetate/phenylbutyrate varied significantly among the tumor cell lines tested. Although losing invasive capacity and tumorigenicity in athymic mice, poorly differentiated cells exhibited only a marginal change in morphology, remained amelanotic, and resumed growth after treatment was discontinued. By contrast, treatment of melanoma cells that were in a more advanced stage of maturation resulted in profound alterations in cell growth, morphology, and pigmentation consistent with terminal differentiation. The in vitro antitumor activity was observed with nontoxic, pharmacologic concentrations of phenylacetate and phenylbutyrate, suggesting potential clinical use of these drugs in the treatment of melanomas.