Expression of aquaporin1, a water channel protein, in cytoplasm is negatively correlated with prognosis of breast cancer patients

// Fengxia Qin 1, * , Huikun Zhang 1, * , Ying Shao 1 , Xiaoli Liu 2 , Limin Yang 2 , Yong Huang 2 , Li Fu 1 , Feng Gu 1 , Yongjie Ma 2 1 Department of Breast Cancer Pathology and Research Laboratory, Key Laboratory of Breast Cancer Prevention and Therapy (Ministry of Education), National Clinical Research Center for Cancer, Tianjin, China 2 Department of Tumor Cell Biology, Key Laboratory of Cancer Prevention and Therapy of Tianjin, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Tianjin, China * These authors contributed equally to this work Correspondence to: Yongjie Ma, e-mail: mayongjie@tjmuch.com Feng Gu, e-mail: fenggumayo@163.com Li Fu, e-mail: fulijyb@hotmail.com Keywords: aquaporin1, breast cancer, prognosis, metastasis, cytoplasm Received: September 10, 2015      Accepted: January 01, 2016      Published: January 23, 2016 ABSTRACT Aquaporin1 (AQP1) belongs to a highly conserved family of aquaporin proteins which facilitate water flux across cell membranes. Although emerging evidences indicated the cytoplasm was important for AQP1 localization, the function of AQP1 corresponding to its cytoplasmic distribution has rarely been explored until present. In our clinical study, we reported for the first time that AQP1 was localized dominantly in the cytoplasm of cancer cells of invasive breast cancer patients and cytoplasmic AQP1 was an independent prognostic factor. High expression of AQP1 indicated a shorter survival, especially in luminal subtype. Moreover, in line with our findings in clinic, cytoplasmic expression of AQP1 was further validated in both primary cultured breast cancer cells and AQP1 over-expressing cell lines, in which the functional importance of cytoplasmic AQP1 was confirmed in vitro . In conclusion, our study provided the first evidence that cytoplasmic expression of AQP1 promoted breast cancer progression and it could be a potential prognostic biomarker for breast cancer.