Correlation between the expression of folate receptor alpha (FRα) and clinicopathological features in patients with lung adenocarcinoma

Objectives Folate receptor alpha (FRα) is expressed on the cell surface, mediates its intracellular transport via receptor-mediated endocytosis, and is involved in cell division. Whether FRα could be a potential therapeutic target in FRα-expressing cancers remains unknown. Here, we retrospectively investigated the correlations between tumor FRα expression in lung adenocarcinoma (LADC) and clinicopathological features. Materials and methods FRα expression was evaluated using a tissue microarray (TMA) constructed from surgical specimens of LADC and compared with clinicopathological features including the EGFR mutation status and the expressions of PD-L1, PD-L2, PD-1, CD4, CD8, CD204, and αSMA. If the proportion of positively stained tumor cells was greater than or equal to 5%, the tumor was considered to show FRα expression; if the H-score was more than or equal to 60, the tumor was considered to show high FRα expression. Results Overall, 466 TMA cores created from 233 LADC patients were evaluated: FRα-positive expression (FRα-pos)/negative (FRα-neg), 222/11; FRα high expression (FRα-HE)/low (FRα-LE), 190/43. AnEGFR mutation was present in 53.2 % of the patients. The median H-score of FRα expression, FRα-pos rate, and FRα-HE rate for EGFR mutation/wild type were 159/104 (p = 0.0002), 97.6/92.7 % (p = 0.0773), and 88.7/73.4 % (p = 0.0026), respectively. The H-scores for FRα had mild correlations with the proportion of tumor cells with positive staining for PD-L1 (r=-0.2557, p < 0.0001), the number of CD8-positive cells per square millimeter (r=-0.1767, p = 0.0069), and the area with positive staining for αSMA (r = 0.2049, p = 0.0017). No correlations were seen between FRα expression and other cancer-immunity markers. Conclusion Tumor FRα expression was significantly higher in LADCs withEGFR mutation than in those with wild-type EGFR. This study suggested that FRα expression was related to cancer and microenvironment-immunity markers such as PD-L1 expression, CD8 cells, and αSMA.