B7-H3 membranous expression correlates with histological grading in a two-center cohort of 133 pre-treatment bone and soft tissue sarcoma samples

Background B7-H3 targeted therapies are an upcoming promising treatment option for a variety of solid tumors. High levels of B7-H3 expression have only been reported for a few sarcoma subtypes in previous studies, but a systematic analysis in an untreated sarcoma cohort and across many different sarcoma subtypes has not yet been conducted. Methods One hundred thirty-three sarcoma samples of previously untreated patients from different sarcoma entities including soft tissue sarcoma (STS, n = 103) and bone sarcoma (BS, n = 30) were collected from two sarcoma centers in South-West Germany. Samples were centrally immunohistochemically stained and assessed for membranous B7-H3 expression. For further analysis of B7-H3 expression, H-Scores were calculated. Baseline characteristics such as sex, age, histology, grading, staging as well as outcome data like treatments, event-free and overall survival were collected. Results B7-H3 was found to be broadly expressed (97%) across all tested sarcoma subtypes, with only four samples (3%) without B7-H3 expression. 45% of all samples had low (H-Score 1-100), 33% intermediate (H-Score 101–200) and 19% high (H-Score 201–300) membranous B7-H3 expression. Highest expression was found in pleomorphic liposarcoma (median 202.5), osteosarcoma (median 175) and angiosarcoma (median 167.5), whereas expression was lowest in myxoid and well differentiated liposarcoma (medians 44.5 & 62.5) and chondrosarcoma (median 60). H-Scores were found to significantly correlate positive with histological grading irrespective of histological sarcoma subtype. Pre-treatment B7-H3 H-Scores did predict event-free but not overall survival. Conclusions B7-H3 is a promising treatment target in sarcomas as it is highly expressed particular in high grade bone and soft tissue sarcomas, such as pleomorphic liposarcomas and osteosarcomas.