How do Tumors Actively Escape from Host Immunosurveillance?

The immunological background for the process of tumor growth is still obscure. However, our understanding of what happens could have important consequences, namely in the context of cancer immunotherapy. A tumor is able to grow in the host environment either because it is recognizable as normal tissue and tolerated by host immune cells, or because it can "escape" from host immunosurveillance. According to the second option the mechanisms of tumor recognition and consequent destruction are actively disturbed by such processes as: change of tumor immunogenicity, production of tumor-derived regulatory molecules, and interaction of cancer cells with tumor-infiltrating immune cells. The results of studies devoted to the problem of immunoregulation in the tumor environment seem to support the "escape" hypothesis.