Aquaporin-1 expression as predictive marker of chemoresistance in ovarian high-grade serous carcinoma: a comparative study between preoperative peritoneal biopsies and surgical samples

Introduction. Aquaporin 1 (AQP1), as component of transmembrane-water-channel family proteins, is involved in different aspects of cancer biology and metastatic events. AQPs expression has been documented in different human tumors and, recently, also in ovarian carcinoma (OC). Anyway, only few studies have investigated the prognostic role of AQP1 in OC; however, the relationship between AQP1 expression and response to chemotherapy remains to be fully elucidated. Materials and Methods. By immunohistochemistry, the expression of AQP1 was evaluated in the preoperative peritoneal biopsies of 32 patients with peritoneal carcinosis, in which a histological diagnosis of high grade serous ovarian carcinoma was made; a cut-off of >1 % positive tumor cells was utilized to distinguish immunoreactive positive cases from negative ones. Furtherly, the potential association between immunohistochemical expression of AQP1, chemotherapeutic response and clinico-pathological parameters, was statistically investigated. Results. Taking into consideration the cut-off, 20 (62.5%) cases showed positive membranous staining (AQP1+), while 12 (37.5%) cases were considered negative (AQP1-). In the AQP+ group, Fisher exact test showed a significant association of AQP1 expression with poor chemotherapy response in omental tissues complete response score (CRS) 1-2 (p= 0.0039), while a CRS 3 was never observed in all positive cases. No significant relationship emerged between AQP1 expression and other clinico-pathological variables. Discussion and conclusions. The study findings suggest that AQP1 may be expressed in a sub-group of OC cases and it could be proposed as predictive marker. Therefore, at the time of the diagnostic peritoneal biopsy, patients affected from high grade serous carcinoma should be categorized in 2 different predictive groups, such as AQP+ and AQP-; OC AQP+ cases may represent a subset of poor responders patients, that could be considered more eligible for cytoreductive surgery rather than for neoadjuvant chemotherapy.