Immunologic aspects of prostate cancer

The concept that cancer can be eliminated by the immune system has been put forward over 100 years ago [1]. At this time, it was already thought that immune effector cells can recognize cancer cells as non-self and can eliminate them in the same way as viral or microbial pathogens. Both the innate immune system and the adaptive immune system have a major role in the control of tumor cell growth. The innate immune system consists of nonantigen-specific cells including macrophages, dendritic cells, neutrophils, natural killer cells, gamma delta T cells, and complement. The adaptive immune system consists of cells such as antigen-specific cytotoxic and helper T cells and antibody-producing B cells which can obtain a memory phenotype against specific antigenic challenge. The result is the ability of the different immune cell types to recognize cancer cells as foreign [2]. Antigens produced by tumor cells are known to be recognized by T cells and B cells, and both tumor antigen-specific T cells and antibodies against tumor antigens can be detected in patients with cancers such as melanoma, ovarian cancer, colorectal carcinoma, and hepatocellular cell carcinoma [3, 4]. Tumor-related antigens fall into a number of types including unique patient or shared tumor-specific antigens, antigens which are in both tumors and normal tissues, and antigens derived from tumor-associated viruses. In prostate cancer, a number of antigens are expressed which can be used for prostate cancer diagnosis or monitoring (Table 5.1).