B7 Family Proteins in Cancer Progression: Immunological and Non-Immunological Functions

The B7 family of proteins is commonly divided into three classes according to their structure and the type of receptor they bind to.The B7 proteins exhibit both positive and negative functions with regard to the immune response and are known to be co-inhibitory or co-stimulatory ligands that regulate antitumor immune responses.They are also involved in the regulation of cancer progression via non-immunological functions such as accelerating metabolism, promoting proliferation, and facilitating chemoresistance.Given the dynamic interaction between cancer cells and B7 family proteins, each member has been considered as a novel biomarker or therapeutic target that may well improve the effectiveness of cancer diagnosis and treatment.In this review, we summarize the characteristics of B7 proteins and their immunological and non-immunological roles in cancer progression.