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A. Bowman
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P1.17 - Thymic Malignancies/Esophageal Cancer/Other Thoracic Malignancies (ID 703)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Thymic Malignancies/Esophageal Cancer/Other Thoracic Malignancies
- Presentations: 1
- Moderators:
- Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P1.17-019 - B7-H3 Protein Expression in Thymic Epithelial Tumour Subtypes and Its Association with PD-L1 and Clinical Characteristics (ID 10332)
09:30 - 09:30 | Author(s): A. Bowman
- Abstract
Background:
B7-H3 (CD276) belongs to the B7 immunoregulatory family that includes PD-L1. Its expression is associated with poor overall survival (OS) in a range of solid tumours but its expression in TETs is unknown. Phase II clinical trials with anti-PD-1 inhibitors are on-going and exhibit good efficacy although they are often complicated by severe autoimmune toxicities. We measured the levels of B7-H3 in TETs and associated them with PD-L1 levels, OS and GTF2I status.
Method:
TMA sections from each of 125 TET FFPEs and 18 thymic hyperplasias were stained separately with antibodies to PD-L1 (clone 28-8, Abcam) and B7-H3/ CD276 (clone 6A1, Abcam). CD45 and cytokeratin (MF116) stains were used to differentiate epithelia and lymphocytes. All sections were scored with an H-score, giving a final score range of 0-300. For each antibody scores for each TET subtype were compared to each other with the Mann-Whitney test. Positive staining was defined as any staining above 0. Associations between the antibody scores and clinicopathological variables were determined.
Result:
The histological breakdown of analyzed samples was 17 A, 4 MNT LS, 30 AB, 25 B1, 26 B2, 5 B3, 10 CA, 8 NETT and 18 hyperplasias. B7-H3 protein was detected in the epithelia of 110 of 125 TETs (88%) and in 15 of 17 hyperplasias (88%) (Subtype breakdown in Diagram 1). No link between OS and GTF2I mutations status (previously described) was found. B7-H3 and PD-L1 were co-expressed in 94 of 125 TETs (75%). Only 2 B1 TETs were negative for both. Figure 1
Conclusion:
B7-H3 protein is expressed in the large majority of TETs, being highest in A and AB thymomas followed by squamous and neuroendocrine carcinomas. Trials with anti-B7-H3 monoclonal antibodies are already underway and given these findings, patients with TETs are likely to be good subjects for these trials.
