PD-L1 in gestational trophoblastic disease: an antibody evaluation.

INTRODUCTION: Treatment with antibodies directed against programed-cell death ligand 1 (PD-L1) is a novel therapy for patients with gestational trophoblastic disease. Assessment of PD-L1 expression in tumor tissue is commonly used to identify patients who might benefit from anti-PD-L1 treatment. Multiple antibodies are available to detect PD-L1-expressing cells, and percentages of PD-L1-expressing cells in samples of patients with gestational trophoblastic disease indicated by these antibodies differ substantially. This raises the question which PD-L1 antibody best reflects PD-L1 expression to select patients for treatment. MATERIAL AND METHODS: Seven commercially available antibodies for PD-L1 staining (E1L3N, 73-10, 22C3, CAL10, SP142, 28-8, SP263) were validated on Chinese hamster ovarian (CHO) cells transfected with PD-L1, PD-L2, wildtype CHO cells and tonsil tissue. Next, four complete hydatidiform moles and four choriocarcinomas were stained. Samples were independently assessed by two pathologists. RESULTS: All seven antibodies showed membranous staining in the PD-L1-transfected CHO cells. E1L3N and 22C3 scored the highest percentages of PD-L1-positive cells (70%-90% and 60%-70%, respectively). E1L3N stained the cytoplasm of non-transfected CHO cells and was excluded from analysis. The remaining six antibodies predominantly stained syncytiotrophoblast cells of both complete hydatidiform moles and choriocarcinomas. The percentage of PD-L1-stained trophoblast cells and staining intensity varied substantially per used PD-L1 antibody and between complete hydatidiform moles and choriocarcinomas. Agreement between pathologists was best with 22C3 (intraclass correlation coefficient 0.94-0.96). CONCLUSIONS: Based on staining results of the CHO cells, gestational trophoblastic disease samples and intraclass correlation coefficient, 22C3 seems the most suitable for adequate detection of PD-L1-expressing trophoblast cells. All antibodies detected PD-L1-expressing cells in the gestational trophoblastic disease samples, though with great variability, hampering comparison of results between studies in this rare disease and emphasizing the need for uniformity in detecting PD-L1-expressing cells.

Early prediction of post-molar gestational trophoblastic neoplasia and resistance to methotrexate, based on a single serum human chorionic gonadotropin measurement.

BACKGROUND: Clinicians are unable to provide individualized counseling regarding risk of progression for patients with a complete hydatidiform mole (CHM). We developed nomograms enabling early prediction of post-molar gestational trophoblastic neoplasia (GTN) and resistance to methotrexate (MTX) based on a single serum human chorion gonadotropin (hCG) measurement. METHODS: We generated two nomograms with logistic regression: to predict post-molar GTN, and MTX resistance. For patients with high probability to progress to post-molar GTN or MTX resistance, we determined hCG cut-offs at 97.5% specificity to select patients for additional- or adjustments in current treatment. RESULTS: The nomograms had a good to excellent ability to distinguish either between patients with uneventful hCG regression versus progression to post molar GTN, or between patients cured by MTX versus patients in whom resistance would occur. At 97.5% specificity, we identified 66% (95%CI 56-75) of the 149 patients who would progress to post-molar GTN, four weeks after initial curettage. For patients treated with MTX, we identified 55% (95%CI 23-83) of the 43 patients who would become resistant, preceding their third course at 97.5% specificity. CONCLUSION: The nomograms and cut-off levels can be used to assist in counseling for patients diagnosed with CHM.

Immune cell composition in the endometrium of patients with a complete molar pregnancy: Effects on outcome.

OBJECTIVE: In 15% of patients with complete hydatidiform mole (CHM), disease progresses to post-molar gestational trophoblastic neoplasia (GTN) after curettage. Tumor infiltrating lymphocytes (TILs) are essential in overcoming disease in many tumors. Infiltrating lymphocyte composition and density may influence trophoblast regression and development of post-molar GTN. We analyzed immune cell composition and density in curettaged endometrium of patients with CHM which spontaneously regressed, and of patients with CHM which progressed to post-molar GTN. METHODS: Sixteen patients with CHM and spontaneous regression, and 16 patients with CHM which progressed to post-molar GTN were selected. Immune cell composition and density of natural killer (NK) cells, natural killer T (NKT)-like cells, Cytotoxic T cells, T-Regulatory and T-Helper cells, were determined by multiplex immunohistochemistry (mIHC). RESULTS: Curettaged endometrium of patients with CHM and spontaneous regression contained a slightly higher number of immune cells compared to patients with CHM which progressed to post-molar GTN. NKT-like cell density was significantly higher in patients with spontaneous regression compared to patients with CHM which progressed to post-molar GTN (483 ± 296 vs.295 ± 143 (mean ± SD), p = 0.03) respectively. NKT-like cell density in the spontaneous regression group was split in 'high' and 'low' (i.e. above and below the median number of NKT-like cells). In patients with high NKT-like cell density, hCG normalized earlier than in patients with low NKT-like cell density (9.5 weeks, (range 3.7-14) vs. 12.9 weeks, (range 8.6-17.9), p = 0.05). CONCLUSION: A high number of NKT-like cells in the endometrium of CHMs may contribute to spontaneous regression of molar trophoblast cells.