Programmed death-ligand 1 upregulation is associated with poor prognosis in patients with epithelial ovarian cancer

The clinical significance of programmed death-ligand 1 (PD-L1) expression in epithelial ovarian cancer (EOC), particularly its association with platinum resistance (PR) and prognosis, remains unclear. This study aimed to evaluate the relationship between PD-L1 expression and PR in EOC and investigate cisplatin-induced PD-L1 modulation using in vitro and in vivo models.

We retrospectively analyzed 189 patients with EOC, treated between 2014 and 2020. Tumor PD-L1 expression was assessed by immunohistochemistry (IHC) using the combined positive score (CPS). Serum PD-L1 levels were measured using enzyme-linked immunosorbent assay (ELISA). Cisplatin-induced PD-L1 regulation was examined in paired platinum-sensitive (PS: A2780 and ES2) and PR (A2780R and ES2R) cell lines and xenograft models.

High tumor PD-L1 expression (CPS ≥10) was more frequent in PR (38.5%) than in PS patients (19.0%, p < 0.01), and was associated with higher recurrence rates ( p < 0.001) and shorter overall survival ( p < 0.001). Serum PD-L1 concentrations were significantly elevated in patients with endometrioid and clear cell histologies compared with those in the control group ( p < 0.05). In vitro, PD-L1 expression was upregulated in PR cell lines compared with parental PS cell lines and was further increased following cisplatin exposure in a dose- and time-dependent manner. Xenograft models confirmed that cisplatin induces PD-L1 upregulation in both tumor tissue and serum, with more pronounced effects observed in PR tumors.

PD-L1 upregulation (CPS ≥10) is associated with PR, disease recurrence, and poor prognosis in EOC. Endometrioid and clear cell histologic subtypes demonstrated higher baseline PD-L1 expression in our cohort. Cisplatin-induced PD-L1 upregulation represents a tumor-intrinsic response, particularly in PR tumor cells, highlighting PD-L1 as a histology-specific marker of poor prognosis and a potential therapeutic target in platinum-resistant EOC.