CD80, the first identified member of the B7 family, is a protein that is widely expressed across a variety of tissues and is also found on some malignant tumor cells. This distribution suggests a potential mechanism by which tumor cells can evade the immune system. Recognized as a potent costimulatory molecule, CD80 plays a significant role in how immune cells regulate malignant growth.
CD80 is upregulated in response to cellular stress and is essential for effective immune surveillance, particularly during the process of carcinogenesis. Studies have reported that a low surface expression of CD80 on colon carcinoma cells can be an immune evasion mechanism. Conversely, in colorectal cancers (CRC) with high-frequency microsatellite instability (MSI), a subtype known for its immunogenicity and association with better prognosis, CD80 expression is often increased.
Both in vivo and in vitro research has demonstrated that increased CD80 expression on the surface of tumor cells can effectively activate antitumor immune responses. However, during tumor progression, the expression of CD80 is frequently diminished, possibly due to selective pressures exerted by the immune system.
Given these findings, enhancing CD80 expression in tumors is a strategy that urgently needs to be explored for the development of effective cancer immunotherapies.