Research Progress on Co-stimulating Molecule B7-H3 in Hematological Malignancies

Abstract

Costimulatory molecule B7-H3 is a new member of the B7 immunoregulatory family identified in 2001. Although B7-H3 mRNA is widely detected in a variety of lymphoid and nonlymphoid organs, but the B7-H3 protein is distributed limitedly, generally absent or low expressed in normal tissues. The triggering receptor expressed on myeloid cell (TREM)-like transcript 2 (TLT-2) is a possible receptor for B7-H3, but it is not confirmed. B7-H3 has an important immunologic function having costimulatory or coinhibitory immunoregulatory effects in adaptive immune responses, but its exact mechanism remains contentious. The recent studies reported that aberrant overexpression of B7-H3 was found in a wide range of solid cancer tissues and cells, and associated with more advanced disease and poor prognosis, and directly performed nonimmunological functions in oncogenesis. However, more and more studies demonstrate that B7-H3 also plays an important role in progression of hematologic malignancies. The overexpression of B7-H3 is significantly associated with the malignant degree, relapse, progression and prognosis in haematological malignancies. Thus, B7-H3 represents a novel diagnostic marker and potential therapeutic target for cancers. The immunotherapy targeting to B7-H3 become one of the hotspots of recent researches, and some monoclonal antibodies have already entered into clinical trials. This review summarizes the available data on the relationship between B7-H3 and hematologic malignancies, and further focusing on B7-H3 as a potential therapeutic target in these tumors.