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.