Tumor antigens and immune regulation in cancer immunotherapy

The importance of T-cell-mediated antitumor immunity has been demonstrated in both animal models and human cancer immunotherapy. The identification of tumor antigens from various types of cancer has generated a resurgence of interest in immunotherapy for cancer and provides the stage to develop therapeutic cancer vaccines. However, recent clinical studies indicate that immunity generated by peptide or DC/peptide vaccines is not sufficient to eradicate cancer. One of the major factors for the weak and transient immune response is the presence of immune suppression in tumor microenvironment. Regulatory T cells and myeloid-derived suppressor cells are major cell types that are responsible for immune suppression. Novel strategies have been developed for enhancing T-cell responses against cancer by overcoming immune suppression. Combination of antigen-specific vaccines to stimulate effector T cells with anti-immune suppression provides opportunities for developing effective cancer vaccines.