Tumor growth and evasion of immune destruction: UV-induced tumors as a model.

A number of complex interrelating mechanisms contributing to progressive growth of an immunogenic tumor and its evasion of immune destruction are exemplified in the model of the UV-induced tumor 1591 (fig. 3). The effects of (i) carcinogen-induced immune suppression, (ii) age-related changes in immune competence, (iii) generation and immunoselection of tumor cell variants which do not express target tumor antigen and (iv) tumor-induced immune suppression have been documented. The findings may help to assess the problems and the possibilities of immunotherapy of cancer. The problems reside in the many avenues of escape available to the tumor. The possibilities for immunotherapy derive from the fact that progressively growing tumors may still retain immunogenic antigens and therefore be susceptible to immune attack.