Folate Receptor Alpha Expression and the Tumor Immune Microenvironment in Patients with Cervical Cancer

Abstract

Folate receptor α (FRα) is a cell-surface protein and an attractive target for cancer treatment. We investigated the association between FRα expression and the tumor immune microenvironment in patients with cervical cancer. We examined whole tumor sections of 123 patients with cervical cancer: 67 and 56 sections of squamous cell carcinoma (SCC) and non-SCC, respectively. FRα expression was assessed using immunohistochemical staining with the anti-FRα monoclonal antibody clone 26B3. Programmed death-ligand 1 (PD-L1) expression was assessed using a combined positive score (CPS). The intratumoral CD3 and CD8 cell densities were calculated as the average number of positive cells in five independent areas. FRα-positivity was identified in 72.4% of the patients, and it differed by histology (SCC vs. non-SCC; 55.2% vs. 92.9%, P<0.001). PD-L1 status was positive (CPS ≥1) in 75.6% and was more commonly expressed in patients with SCC (SCC vs. non-SCC; 83.5% vs. 66.1%, P=0.02). FRα expression had a weak correlation with PD-L1 expression (r=−0.22, P<0.001) and CD8-positive cells (r=−0.19, P=0.03). FRα-positivity was more frequently observed in the PD-L1 CPS <10 group than in the PD-L1 CPS ≥10 group (81% vs. 64%, P=0.03). FRα-high was significantly associated with poor prognosis, especially in the PD-L1 CPS ≥10 groups (hazard ratio: 4.10, 95% confidence interval: 1.39–12.06, P=0.01). In conclusion, FRα expression was higher in patients with cervical cancer and PD-L1 CPS <10 than in those with CPS ≥10. Targeting FRα expression may be a potential therapeutic strategy for cervical cancer patients with low or negative PD-L1 expression.