CD3L1 expression and its association with the tumor microenvironment in 62 cases of osteosarcoma and Chordoma.

CD3L1 (ITPRIPL1), a natural ligand of CD3ε, is implicated in tumor-immune interactions and is overexpressed in several solid tumors. However, its expression and functional significance in osteosarcoma and chordoma remain uncharacterized. This study aimed to evaluate CD3L1 expression in osteosarcoma and chordoma and assess its association with clinical features and outcomes. Formalin-fixed, paraffin-embedded tissue samples from 42 osteosarcoma and 20 chordoma patients were analyzed for CD3L1 expression using immunohistochemistry. Multiplex immunofluorescence staining was performed to evaluate immune cell infiltration in chordoma. Associations between CD3L1 expression and clinicopathological parameters were examined using chi-square tests, Fisher's exact test, and Kaplan-Meier survival analysis. CD3L1 was detected in 62.9% (39/62) of cases, with positivity rates of 59.6% in osteosarcoma and 70.0% in chordoma. CD3L1 expression was independent of patient age, sex, or tumor location but was significantly associated with chondroid stroma and prior PD-1 immunotherapy in osteosarcoma. In chordoma, higher CD3L1 expression correlated with increased infiltration of CD8 T cells, B cells, and M2 macrophages. CD3L1 is expressed in osteosarcoma and chordoma and is associated with features of the tumor immune microenvironment, including markers of macrophage infiltration. As a potential therapeutic target, CD3L1 warrants further functional and clinical investigation.