B7-H3 protein expression in acute myeloid leukemia

Costimulatory molecules are essential regulators of the immunological synapse and enable the fine-tuning of the immune response. These mechanisms are subverted by cancer cells to evade immunosurveillance. The B7 family of costimulatory molecules comprises several ligands that may contribute to immunoescape. B7-H3 [B7-homolog 3 or CD276] remains poorly investigated in hematological malignancies. To determine the role B7-H3, we analyzed the expression of this molecule in blast cells from a cohort of 111 acute myeloid leukemia (AML) patients. B7-H3 was expressed in blast cells with a mean fluorescence intensity ratio >3 in 30 (27%) of the 111 patients. B7-H3 expression was higher in the M3 and M5 FAB subtypes and in cases with mutated NPM1 and wild type CEBPA. There were no significant differences found for the FLT3-ITD or cytogenetic risk groups. The complete remission (CR) rate between the 17 B7-H3-positive and 58 negative patients who were treated intensively was not different. The event free survival was longer in B7-H3-positive patients (P = 0.014), and there was a trend toward better overall survival. However, this difference was not statistically significant (P = 0.053). In conclusion, B7-H3 is one of the most strongly expressed B7-family molecules in AML and merits further investigation.