Yao, Yuan

Objectives: To evaluate the clinical heterogeneity of sarcomas by examining associations between histological subtypes, metastatic patterns, treatment modalities, and survival outcomes. Methods: We analyzed data from 97,062 adult patients diagnosed with sarcoma between 2000 and 2020, using the Surveillance, Epidemiology, and End Results (SEER) database. Fourteen histological subtypes were included. Propensity score matching (PSM) was employed to adjust for baseline differences, and Cox proportional hazards models were used to identify prognostic variables. Results: The most prevalent subtypes were sarcoma not otherwise specified (31.9%), leiomyosarcoma (17.1%), and liposarcoma (13.9%). Metastatic patterns differed significantly by subtype; liver metastases were most common in sarcomas with small blue round cell (SBRC) features (8.9%) and stromal sarcoma (6.1%), while lung metastases were frequently observed in Ewing sarcoma (10.0%) and rhabdomyosarcoma (9.7%). Median overall survival (mOS) varied widely, ranging from 234 months in chondrosarcoma to 16–20 months in rhabdomyosarcoma and SBRC sarcoma. Overall, patients with primary sarcoma had significantly better survival than those with treatment-related disease (119.0 vs. 45.0 months, p < 0.0001), with this trend consistent across most subtypes. Treatment responses were subtype- and size-dependent. For instance, surgery plus radiotherapy improved outcomes in giant cell sarcoma regardless of tumor size, whereas chemotherapy provided benefit only in tumors larger than 5 cm. Combined surgery and radiotherapy offered additional survival benefit in select subtypes, including chordoma, leiomyosarcoma (>5 cm), and synovial sarcoma (<5 cm). Conclusions: Sarcomas exhibit substantial clinical and prognostic heterogeneity across histological subtypes. These findings underscore the importance of subtype-specific, individualized treatment strategies in optimizing patient outcomes.

Abstract Extrachromosomal DNA (ecDNA) drives the evolution of cancer cells by conferring survival advantages over normal cells. However, the functional importance of ecDNA replication and maintenance is yet to be evaluated, and the molecular components that contributed to these processes remain largely unknown. Here, using CRISPR-C (circularization of genes and chromosomes by CRISPR) technology and synthetic circular DNA mimicking ecDNA identified in tumors, we generated ecDNA-positive (ecDNA+) cell models. Using these models, we identified the proteins involved in ecDNA replication and maintenance and found DNA damage response (DDR)-related pathways were significantly enriched. We further demonstrated that ecDNA replication led to increased DDR and genome instability and DDR was also essential for ecDNA maintenance, consistent with observations that ecDNA+ tumors exhibited higher DDR scores than ecDNA-negative (ecDNA–) tumors in patients. ATM, MDC1, and CHK2, but not ATR, were activated in ecDNA+ cells compared to ecDNA– cells. Moreover, ecDNA+ cells were more sensitive to ATM and CHK2 inhibition. We further found that type II topoisomerase TOP2B and DNA ligase III (LIG3) were critical regulators for ecDNA replication and maintenance and related DDR. In summary, our findings of the reciprocal interactions between ecDNA and DDR provide new insights into detection and therapy for ecDNA+ tumors.