Introduction

Immune system is composed of innate and adaptive responses and plays critical roles in cancer development and destruction. A century ago, Paul Ehrlich postulated that cancer would be quite common in long-lived organisms if not for the protective effects of immunity. About 50 years later, Burnet and Thomas proposed the concept of cancer immunosurveillance based on the experimental evidence of immune recognition of tumor antigens expressed on tumor cells (Dunn et al. 2004). In 1971, the US Congress created a National Cancer Act-a War on Cancer. Among many tough questions asked were whether the immune system can be manipulated so that it recognizes tumor cells as foreign invaders that must be eliminated from the body and whether viruses play a role in human cancer. In 1980s, Steven Rosenberg and his colleagues developed adoptive cell therapy (ACT) for the treatment of melanoma cancer patients using lymphocyte activated killed (LAK) cells, providing the first direct evidence that the immune system can be manipulated to achieve therapeutic efficacy of cancer treatment (Rosenberg, 2011). In 1990s, many human tumor antigens such as MAGE and NY-ESO-1 have been identified from melanoma and many other types of cancer using tumor-reactive T cells, thus setting the stage for the development of cancer vaccines in the twenty-first century (Wang and Rosenberg, 1999). Indeed, the first dendritic cell (DC)-based vaccine was approved in 2010 by the U.S. Food and Drug Administration (FDA) for the treatment of patients with prostate cancer.