Introduction CD73 (ecto-5’-nucleotidase) is a membrane-bound enzyme crucial in adenosine generation. The adenosine pathway plays a critical role in immunossupressive tumor-microenvironment (TME). The purpose of the study was to evaluate CD73 expression in TME, and its association with clinicopathological features to better understand the role of CD73-adenosine pathway in epithelial ovarian cancer (EOC).

Methods A total of 48 patients (treatment-naïve, n=35; recurrent, n=13) with epithelial ovarian cancer were enrolled in the current study. For each patient, a retrospective review of medical records was conducted. Immunohistochemical staining for CD73 was performed using paraffin embedded tissue block. CD73 expression level were graded on a scale of 0 to 3.

Results Median age was 59 years (range 38–84 years), and the majority of the patients presented with high-grade serous carcinoma (HGSC, 85.4%) and stage III-IV disease (89.6%) at diagnosis. Among the treatment-naive patients, 17.1% of patients (n=6) showed low CD73 expression (grade 1), whereas 60.0% of patients (n=21) showed high CD73 expression (grade 2/3). All of the BRCA1/2-mutated tumors were high CD73 (n=7), whereas 20% of BRCA1/2-non-mutated tumors (n=5) were low CD73 expression. The CD73 high group showed better PFS compared to the CD73 low group (median PFS 20.1 versus 11.9 months, P=0.043). Among the recurrent patients, 84.6% of patients (n=11) showed high CD73 expression (All HGSC [n=10] were high; all clear cell carcinoma [n=2] were low).

Conclusion/Implications Our study suggests that higher CD73 expression is associated with favorable survival outcomes in EOC. Further studies are needed to explore the role of CD73 in EOC.