Many therapeutic strategies are continuously being investigated to find the means to effectively treat cancer. Immunotherapeutic approaches are emerging as very valuable options for patients with different types of cancer. Many of the approaches involve targeting the adaptive immune system. The adaptive immune system involves targeting specifically identified cells by cytotoxic T cells and represents a specialized attack on invading and pathogenic (disease-causing) cells and molecules.
However, a new treatment approach by scientists at Kobe University involves an enhancement of cells that are members of the innate (general, nonspecific) immune system, macrophages. This entails the use of antibodies against cancer cell and immune molecules to inhibit tumor growth. One antibody, called anti-SIRPalpha, has advantages in antitumor therapy. SIRPalpha is a protein located on macrophages. The CD47 protein of tumor cells interacts with the SIRPalpha protein and affects the pathogen-engulfing function of macrophages.
The researchers showed in laboratory mice that the anti-SIRPalpha antibody is capable of increasing the ability of the drug rituximab to suppress tumor growth. Rituximab is an antibody drug that binds to B lymphocytes. Treatment with anti-SIRPalpha allows rituximab to strengthen the engulfing function of macrophages. The antibody also binds to the SIRPalpha inhibiting it from interfering with macrophages. The scientists further showed the importance of the effect on macrophages for tumor suppression by treating mice whose macrophages were eliminated. The tumor-suppressing effect of anti-SIRPalpha was weakened in these mice.
In addition, anti-SIRPalpha works well with another antibody, anti-PD-1. PD-1 is an immune checkpoint molecule for cytotoxic T cells. Checkpoint molecules of the immune system are important for self-tolerance. However, tumor cells can exploit this to evade cytotoxic T cell attack leading to immune resistance of tumors. Co-treatment with anti-SIRPalpha and anti−PD-1 antibodies in laboratory mice injected with colon cancer cells resulted in stronger antitumor effects than using either of the antibodies alone. This approach can serve as a new cancer treatment strategy involving the innate and adaptive immune systems.
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Reference: Kobe University. (2017, February 6). Potential new cancer treatment activates cancer-engulfing cells. ScienceDaily. Retrieved March 8, 2017 from www.sciencedaily.com/releases/2017/02/170206084054.htm