Aberrant Expression of Folate Metabolism Enzymes and Its Diagnosis and Survival Prediction in Ovarian Carcinoma

Hindawi Analytical Cellular Pathology Volume 2019, Article ID 1438628, 9 pages https://doi.org/10.1155/2019/1438628 Research Article Aberrant Expression of Folate Metabolism Enzymes and Its Diagnosis and Survival Prediction in Ovarian Carcinoma Jia Chen1,2 and Li Li 2,3 1 Department of Radiology, Affiliated Tumor Hospital of Guangxi Medical University, Nanning, Guangxi, China Department of Gynecologic Oncology, Affiliated Tumor Hospital of Guangxi Medical University, Nanning, Guangxi, China 3 Laboratory of Early Prevention and Treatment for Regional High Frequency Tumor, Ministry of Education Key Laboratory, Nanning, Guangxi, China 2 Correspondence should be addressed to Li Li; Received 23 December 2018; Accepted 5 March 2019; Published 31 March 2019 Academic Editor: Giovanni Tuccari Copyright © 2019 Jia Chen and Li Li. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This study was to validate changes in the levels of folate receptor-α (FOLR1), dihydrofolate reductase (DHFR), and methionine synthase reductase (MTRR) in the tissue of OC patients. The expression of FOLR1, DHFR, and MTRR was evaluated in 80 cases of primary OC, 50 cases of benign ovarian tumors, and 30 normal ovarian tissues. Associations between protein expression and clinicopathological characters were assessed, and diagnostic and prognostic evaluation of FOLR1, DHFR, and MTRR was performed. Results showed that upregulated FOLR1 and MTRR and downregulated DHFR were detected in OC. Patients with abnormality of FOLR1, DHFR, and MTRR tend to have a higher percentage of platinum resistance. Moreover, the areas under receiver operating characteristic curves (AUCs-ROC) for FOLR1, DHFR, and MTRR were 0.723, 0.717, and 0.714, respectively. The combination of FOLR1, DHFR, and MTRR could produce an area of 0.864 under the receiver-operating characteristic curve in distinguishing platinum-resistant patients from platinum-sensitive patients (P < 0 0001). Correlations were present between the expression of FOLR1, DHFR, and MTRR. Furthermore, Kaplan-Meier curves indicated that the patients with overexpressed MTRR had a poorer overall survival time compared to those with low expression (P < 0 05). Thus, folate metabolic enzymes could provide a potential promising biomarker for diagnosis platinum-resistant in OC. 1. Introduction Ovarian cancer is the fourth most common cancer in women worldwide, and it has the most noteworthy lethal rate around gynecologic malignancies. Two most critical barriers to treatment of ovarian malignancy are absence of early diagnostic markers and advancement of drug resistance after therapy, especially in advanced stages. Various epigenetic changes have been recognized in ovarian cancer. Recent progresses in our understanding of molecular pathogenesis of ovarian malignancy have dramatically provided potential new targets for molecularly targeted therapies. There thus is a critical need for improved biological markers and therapies for ovarian carcinoma, which will come from a better understanding of the biology of the disease. Folate is an essential component in DNA synthesis, replication and repair, protein synthesis, and methylation reactions. This is especially true for rapidly dividing cells [1]. Folate receptor 1 (FOLR1) internalizes folates by means of receptor-mediated endocytosis and reduced folate carrier (RFC) uses a bidirectional anion-exchange mechanism to transport folates into cytoplasm [2, 3]. Dihydrofolate reductase (DHFR) catalyzes the reduction of dihydrofolate (DHF) to tetrahydrofolate (THF), which plays a vital role in cellular metabolism and cell growth [4]. Methionine synthase reductase (MTRR) is an enzyme controlling the activity of MTR in folate metabolism by transferring the methyl group of methyltetrahydrofolate to homocysteine via the methionine synthase, which is responsible for DNA methylation [5]. In the previous research in our lab, ovarian cancerresistant cell lines were established to screening drugresistant genes [6]. Most of them are associated with metabolism, especially folate metabolism. Meanwhile, we have reported that overexpression of MTRR plays an 2 important role in cisplatin resistance, and silencing MTRR expression partially reverses cisplatin-resistant phenotype [7]. In the present study, the expression levels of FOLR1, DHFR, and MTRR were examined in OC tissues, and the prognostic ability of these three proteins was investigated and compared. The aim of this study was to validate changes in the levels of FOLR, DHFR, and MTRR in the tissue of OC patients. We sought to determine whether folate metabolism enzymes could serve as a novel biomarker for early diagnosis and prognosis of platinum-resistant OC patients, as well as their clinical significance in OC. 2. Materials and Methods 2.1. Clinical Samples and Follow-Up. OC tissues and normal ovary tissues were collected from patients who were treated in the Department of Gynecologic Oncology of the Affiliated Tumor Hospital of Guangxi Medical University between 2004 and 2010. All the patients were pathologically diagnosed with OC. Pathological stage and histological subtype were determined according to the International Federation of Gynecology and Obstetrics (FIGO) criteria and the World Health Organization criteria. Clinical and pathological data was collected from the medical records including age, surgical stage, metastasis, ascites, tumor grade and subtype, and drug resistance. Samples were collected from 80 cases of primary OC, 50 cases of benign ovarian tumors, and 30 normal ovarian tissues. The median age was 41.1 years (range: 13-76 years) in the OC group, 40.1 years (range: 10-74 years) in the benign ovarian tumor group, and 43.1 years (range: 29-60 years) in the normal ovary group. The 80 OC patients underwent surgical intervention for OC of whom 61 patients with epithelial ovarian cancer received chemotherapy with cisplatin plus paclitaxel and 19 patients with nonepithelial ovarian cancer were treated with cisplatin, bleomycin, and vincristine. The study was approved by the Ethics Committee of Guangxi Medical University. Written informed consent was obtained from all the subjects before study. 2.2. Western Blotting Analysis. 160 fresh specimens were sonicated with an ultrasonic tissue disrupter in lysis buffer for 30 min. The tissue debris was pelleted by centrifugation, and supernatants were collected. After measuring the protein concentration by BCA protein assay, proteins were subjected to SDS-PAGE and then transferred onto PVDF membranes. After blocking, the membranes was treated with 5% (w/v) BSA in PBST (PBS, pH 7.5, containing 0.1% Tween-20) and then incubated with primary antibodies MTRR (1 : 1000; Santa Cruz Biotechnology), FOLR1 (1 : 1200; Abcam), and DHFR (1 : 1000; Santa Cruz Biotechnology) overnight at 4°C. (...truncated)