Effects of Co-Transplantation of Thymus and Stem Cells on Treatment of Malignant Tumors

There has recently been a rapid increase in cancer, and inflammation has been shown to play an important role in its development (Ahmad et al., 2009). Inflammatory cells produce cytokines such as TNF IL and IL which promote tumor growth, and tumor cells also produce macrophage colony-stimulating factor (M-CSF), which accelerates the immune response (Marx, 2004; Borrello et al., 2008). Aging leads to a marked malfunction of multiple cellular and molecular events that ultimately get translated into various chronic ailments and diseases such as Type 2 diabetes mellitus (T2DM), Alzheimer’s disease (AD), and osteoporosis, Parkinson’s disease, atherosclerosis, and an increased risk of cancer (Caruso et al., 2004). Aging leads to decreases in humoral and cellular immune responses, aged dendritic cells (DCs) being less able to activate T and B cells, and aged-natural killer (NK) cells being less efficient at killing tumor cells (Frasca et al., 2008). Based on histological type, cancer can be classified into five major categories: carcinoma, sarcoma, myeloma, lymphoma and mixed types. Treatment mainly includes surgery, radiotherapy, chemotherapy, immunotherapy, and stem cell transplantation. Radiotherapy and chemotherapy play a role in preventing cancer development, but cause adverse side effects. Immunotherapy is an effective method that aims to harness the body’s own immune system to fight the cancer. Using this approach, T cells are more able to recognize aberrant proteins from tumor cells, and either destroy the tumor cells or inhibit their growth (Schreiber et al., 2011; McNutt, 2013). The first to report a strong correlation between tumor-infiltrating T cells and patient survival in human colorectal cancer was Naito et al in 1998 (Naito et al., 1998). Moreover, it has been shown that increased CD8+ T cells infiltrate non-small-cell lung cancers, and may thus improve patient survival (Zhuang et al., 2010). In terms of immunotherapy, the most successful cancer vaccine has been described by Kenter et al, who suggest that complete responses are correlated with the induction of human papillomavirus type 16-specific immunity (Kenter et al., 2009). Recently, we have seen the development of new immunotherapies such as vaccination approaches and the use of monoclonal antibodies for tumors (Davies, 2014). For example, melanoma-associated antigen A3 (MAGE-A3) gene is expressed during embryogenesis and in a wide variety of tumors (Van den Eynde and van der Bruggen, 1997), and one report has shown that MAGE-A3 may facilitate antigen uptake by antigen-presenting cells, promoting T-cell responses, although it