The use of FoxP3 as a biomarker and prognostic factor for malignant human tumors

Only since the early 21st century has it been proven that the immune system can actively defend the body against the development of malignant tumors. Escape from this process, termed immunosurveillance, has been shown to be required for the development of many tumors in both mice and humans, and may be a necessary prerequisite for the establishment of many malignancies. Serendipitously, an evolution in the understanding and characterization of immunosuppressor cells, regulatory T cells, has coincided with the establishment of tumor immunosurveillance. These two fields merged when it was found that the recruitment of regulatory T cells within tumors was a dominant mechanism tumors used to escape immunosurveillance. Regulatory T cells are specifically identified with antibodies which recognize the transcription factor, FoxP3. The presence of FoxP3+ cells within tumors has been shown to predict the prognosis, invasiveness, and metastatic ability of some tumors by modulating the ability of the immune system to target tumor cells. Furthermore, depletion of regulatory T cells from tumors could lead to the rejection of both early- and late-stage tumors by the host immune system. These findings suggest that the widespread use of FoxP3 as a biomarker should be explored for human tumors to enable physicians to make better decisions in oncologic care and to prepare the field for novel therapeutic agents directed at the elimination of regulatory T cells within tumors.