Prognostic significance of L-type amino acid transporter 1 (LAT1) expression in patients with ovarian tumors

Aim: Amino acid transporters are essential for the growth, progression and the pathogenesis of various cancers. However, it remains obscure about the clinicopathological significance of L-type amino acid transporter 1 (LAT1) and system ASC amino acid transporter 2 (ASCT2) for patients with human ovarian tumors. The aim of this study is to elucidate the prognostic role of these amino acid transporters in ovarian tumor. Methods: One-hundred forty-two patients with surgically resected ovarian tumors were analyzed by immunohistochemistry. Expression of LAT1, ASCT2, CD98, Ki-67 and microvessel density (MVD) determined by CD34 were evaluated using specimens of the resected tumors. Results: LAT1 and ASCT2 were positively expressed in 39% and 53%, respectively, of ovarian tumors (n=142) and 50% and 57%, respectively, of epidermal ovarian cancers (n=107). A positive LAT1 expression was closely correlated with the expression for ASCT2 and CD98, and cell proliferation (Ki-67) in ovarian cancer. By multivariate analysis, LAT1 was clarified as a significant independent marker for predicting a poor overall survival (OS). The expression of LAT1 could clearly discriminate between epidermal ovarian cancer and borderline malignancy. The expression level of LAT1 within ovarian cancer cells varied among serous adenocarcinoma, endometrioid adenocarcinoma, clear cell adenocarcinoma and mucinous adenocarcinoma and we found LAT1 expression was higher in clear cell adenocarcinoma than other histological types. Conclusions: LAT1 is highly expressed in various ovarian tumors and a positive LAT1 expression can serve as a significant independent factor for predicting a poor OS in patients with epidermal ovarian cancer.