Antigens and antibodies in malignant melanoma

Antigens, antibodies and immune complexes seem to play a major role in the course of malignant melanoma, in detection of the disease progression, in treatment planning and monitoring. Of particular interest are cell and matrix adhesion molecules, growth factors and cytokines, proteases, gangliosides and major histocompatibility complex class I and II molecules. Antigens expressed on melanoma cells, but not on mature melanocytes, may be used as markers for the degree of the differentiation of the melanoma cells. The more the melanoma cells are dedifferentiated, the smaller is the antigenic similarity to normal melanocytes. Also, different antigens may be identified in various stages of the disease and may be used as tumor markers for disease recurrence or progression. Certain melanoma-associated antigens (MAA) such as epidermal growth factor receptor and adhesium molecules can be modulated by cytokines. Early melanoma evokes an antigen-derived T cell response, which becomes attenuated with the progression of the disease. A variety of cell adhesion molecules present on melanoma cell surfaces may play a role in regulation of cellular cytotoxicity. Free antimelanoma antibodies are usually not detectable in the sera of patients with melanoma, possibly due to their binding to shed antigens and formation of immune complexes or to tissue antigens. When bound to normal melanocytes, they cause the appearance of associated hypopigmentation. The identification of melanoma surface antigens led to generation of monoclonal antimelanoma antibodies (MAb) by laboratories. Strategies utilizing MAb based on immunologic approaches have been developed. MAb to tumor-associated antigens of melanoma cells may be used for therapeutic purposes in man. Sera of patients with vitiligo were capable of causing regression of melanoma metastases in mice due to the presence of a high titer of naturally occurring antimelanoma antibodies. Immunization of melanoma patients with vaccines containing treated melanoma cells or specific melanoma antigens or anti-idiotypic antibodies resulted in an increasing titer of antimelanoma antibodies and regression of the tumor to some extent. The appearance of hypopigmentation in patients with melanoma serves as proof for the activity of antimelanoma antibodies, although its association with the prognosis is still not clear. The thorough investigation in the field of MAA and related antibodies is aimed at improving specific antimelanoma immunotherapy, such as antigenic targeting or enhancement of production of autoantibodies, as well as better understanding of the process of metastasis and the melanoma-immune system interaction.