Osteosarcoma is the most frequent primary bone tumor with poor prognosis. Through RNA-sequencing of 100,987 individual cells from 7 primary, 2 recurrent, and 2 lung metastatic osteosarcoma lesions, 11 major cell clusters are identified based on unbiased clustering of gene expression profiles and canonical markers. The transcriptomic properties, regulators and dynamics of osteosarcoma malignant cells together with their tumor microenvironment particularly stromal and immune cells are characterized. The transdifferentiation of malignant osteoblastic cells from malignant chondroblastic cells is revealed by analyses of inferred copy-number variation and trajectory. A proinflammatory FABP4⁺ macrophages infiltration is noticed in lung metastatic osteosarcoma lesions. Lower osteoclasts infiltration is observed in chondroblastic, recurrent and lung metastatic osteosarcoma lesions compared to primary osteoblastic osteosarcoma lesions. Importantly, TIGIT blockade enhances the cytotoxicity effects of the primary CD3⁺ T cells with high proportion of TIGIT⁺ cells against osteosarcoma. These results present a single-cell atlas, explore intratumor heterogeneity, and provide potential therapeutic targets for osteosarcoma.

Purpose: We investigated the safety and preliminary efficacy of anti–PD-L1 antibody (ZKAB001) as maintenance therapy for localized patients with high-grade osteosarcoma to reduce the risk of recurrence and metastasis. Patients and Methods: This open-label Phase I/II study was divided into dose-escalation Phase I and expansion Phase II. Phase I used a 3+3 design with ZKAB001 at three escalating doses ranging: 5, 10, 15 mg/kg every 2 weeks in 9 patients with localized high-grade osteosarcoma and Phase II tested 10 mg/kg in 12 patients for up to 24 cycles. Primary endpoints were safety and tolerability assessed using CTCAE4.0.3. Results: Between October 2018 and 2019, 21 eligible patients were enrolled and accepted ZKAB001 treatment: 9 in the dose-escalation phase, and 12 in expansion phase. Six patients with disease progression withdrew from this study and follow-up is ongoing. The MTD was not defined in Phase I. All doses had a manageable safety profile. The recommended dose in Phase II was set at 10 mg/kg. Most frequent immune-related adverse events were thyroiditis (76.2%) and dermatitis (42.9%). Only 1 (4.8%) of 21 patients had a Grade 3 skin rash. The median 3-year event-free survival (EFS) and overall survival (OS) were not established; however, 24-month EFS was 71.4% (95% confidence interval, 47.2–86.0) and 2-year OS was 100%. Preliminary efficacy data showed EFS benefits in patients with PD-L1 positive or an MSI-H sub-population. Conclusions: Switching to maintenance using ZKAB001 showed an acceptable safety profile and provided preliminary evidence of clinical activity in localized patients with osteosarcoma.

Objective: The objective of this study was to determine the impact of the lymph node density (LND) on overall survival of patients with Wilms’ tumor (WT) using the Surveillance, Epidemiology, and End Results (SEER) database. Methods: Data from the SEER database were extracted from patients with WT in whom the LND could be obtained. Patients were divided into a low LND group and high LND group. Survival curves based on the LND stratification were plotted using the Kaplan–Meier method and compared with the log-rank test. The impact of prognostic factors on overall survival was analyzed using Cox regression models. Results: A total of 1,924 patients were identified from the database. Overall survival for the low LND group at 5, 10, and 20 years was significantly better than the high LND group (5-year survival: 94.1% vs 81.4%; 10-year survival: 92.6% vs 80.8%; 20-year survival: 90.6% vs 79.1%; P<0.001). In multivariate analysis, LND was a significant predictor of overall survival, regardless of whether it was a categorical variable or a continuous variable. Other significant predictors included age, race, SEER stage, and tumor laterality. Conclusion: LND was a significant risk factor for overall survival of patients with WT. LND may provide a better prediction of the prognosis of WT patients and may be helpful for designing better treatments.