Natural immunity to cancer in humans.

The evolution of cancer reflects intricate cellular and molecular interactions of tumor cells with the tumor microenvironment. Novel systems biology approaches are emerging to analyze the complex interaction between tumors and host-immune response in humans. The opposing host-protective and tumor-promoting roles of the immune system reflect the disparate effects of immunity on tumorigenesis. Global analysis of tumor microenvironment showed that a strong adaptive immune reaction within primary human tumors reduced the risk of relapse events. Recent advances support the existence of immunosurveillance in human cancer. The major role of the intratumoral immune reaction could advance our understanding of tumor evolution and have important consequences in clinical practice.