In December 1971, the President of the United States of America established an extended effort to find a cure for cancer. Since then, the cancer research community has built a significant advance in understanding the pathogenesis of the disease. However, cancer remains one of the leading causes of death worldwide. Chemotherapy, radiation, and surgery have been utilized as the primary weapon against cancer. All the same, these treatments have added little to the overall survival of the patients. In addition, these therapies produce numerous side effects and cannot be afforded by a wide range of people.

Cancer immunotherapy was selected as the breakthrough therapy of 2013 in the field of cancer treatment (Jennifer Couzin-Frankel, Science, 342 (2013): 1432-1433; Marcia McNutt, Science 342 (2013): 1417). Immunotherapy aims to target the immune system and not the tumor itself. The immune responses have the potential to increase and sustain over time. It undergoes pseudoprogression which may reflect the development of antitumor immunity. Immunotherapy uses antibodies that bind to and inhibit the function of cancer related proteins in a specific manner. Immunotherapy also includes usage of vaccines and T cell infusions.

Although immunotherapy has provided a new hope, it does not help every cancer patient. Why some patients do not benefit from immunotherapy is the focus of this special issue. We invite the authors to contribute original research articles as well as review articles to this special issue. We are particularly interested in articles that offer an overview of the existing concepts, novel findings, controversies, and challenges in this area. Articles on future prospects of immunotherapy are invited.

Potential topics include but are not limited to the following:

• Multidrug resistance and cancer immunotherapy
• Immune system and multiple steps of tumor growth
• Immunological aspects of epithelial-to-mesenchymal transition
• Cancer stem cells as target for immunotherapy
• Role of inflammatory molecules in cancer immunotherapy
• Role of noncoding RNAs in cancer immunotherapy
• Immuno-oncology signaling molecules
• Role of tumor microenvironment in cancer immunotherapy
• Role of metabolism in cancer immunotherapy
• Role of human microbiome in cancer immunotherapy
• Safety and toxicity associated with cancer immunotherapy