br Introduction br Prostate cancer PC is the most common
Prostate cancer (PC) is the most common malignancy in the male population, and ranks the third leading cause of cancer related death among males worldwide . In recent years, the morbidity of PC in China continues to rapidly grow . Although early diagnosed and non-metastatic localized PC can be treated by either surgical resection or radiation therapy , a substantial proportion of the cancer cases de-velop castration-resistance and advanced metastasis, thus causing the man death . Despite the significant improvement in detection rate of early-stage PC due to measurement of serum prostate-specific anti-gen (PSA), no consensus regarding whether routine PSA testing effec-tively reduces the risk of death from PC were met by medical and scientific communities . Meanwhile, the biological molecular mecha-nism underlying PC remains largely elusive. Thus, clear understanding of the molecular mechanisms of PC development and metastasis, as well as developing effective biomarkers for early diagnosis, are highly needed for the prevention and treatment of PC.
MicroRNAs (miRNA) are a class of small, non-cording RNAs, which have important roles in the regulation of gene expression .
Corresponding author at: West road of Jiefang 61, Changsha city, Hunan Province 410005, PR China.
Compelling evidence suggests many kinds of miRNAs involved in the initiation and progression of many types of human cancers. For exam-ple, microRNA-224 function as an onco-miRNA in Gastrin I cancer cells ; microRNA-137 functions as a tumor suppressor in human non-small cell lung cancer  and microRNA-4262 promotes tumor growth in hepatocellular carcinoma . Thus, miRNAs can serve as new thera-peutic targets in cancer treatment, as well as predictive biomarkers in cancer diagnosis and prognosis . It is known that several miRNAs (miR-141, miR-375, miR-181a, miR-2, miR-145, miR-221, miR-146, miR-379, etc.) are abnormally expressed in PC cells regulating PC pro-gression [11,12], implicating their potential roles in tumorigenesis of PC. MicroRNA-93 (miR-93) is known to be frequently overexpressed in PC patients, and cooperatively down-regulate Capicua (CIC) levels to promote cancer progression . However, the expression level and the accurate role of miR-93 in PC remain unclear. In this regard, the present study aimed to investigate the potential role and molecular mechanism of miR-93 in PC progression. Despite of great advances in molecular biology and genetics of PC, the treatment options for ad-vanced PC are limited and chemotherapy is still a promising approach against its development. Recently, the interest in the use of dietary in-gredients such as tea, ginger, berries, garlic, and lycopene is increasing for the prevention of cancer all over the world [14,15]. Among these foods, green tea or its derived components have received much atten-tion as chemopreventive agents in PC . With the growing research
findings on the anti-carcinogenic properties of green tea on PC, most studies thus far have focused on Green tea polyphenols . Other than polyphenols, green tea polysaccharides have also been reported to exhibit significant antitumor activities  (Antitumor and antimetastatic activities of rhamnogalacturonan-II-type polysaccharide isolated from mature leaves of green tea via activation of macrophages and natural killer cells). Despite these reports, the antitumor activities of green tea polysaccharides towards PC are not available until now. Thus, in order to discover new antitumor agents for PC, we isolated and characterized green tea polysaccharides, and then examine if miR-93 is involved in the mechanisms by which green tea polysaccharides induced apoptosis of PC cells in vitro.
2. Materials and methods
2.1. Cell lines and human prostate tissue specimens
All experimental procedures were approved by the Ethical and Sci-entific Committees of The Xiangya Hospital of Central South University, and written informed consent was obtained every patient before tissue collection. The surgically resected tissues were collected from a total of 60 patients having PC due to elevated serum prostate-specific antigen (PSA) levels from September 2011 to November 2013, and all PC pa-tients were treated without preoperative radiotherapy and chemother-apy. At the same time, 30 cancer free controls were recruited from patients with prostatic hyperplasia. All these fresh tissue samples were immediately snap-frozen in liquid nitrogen and stored at −80 °C for future use.
Survival percentage was estimated using the Kaplan–Meier method and comparison of the overall survival rate (%) between miR-93 high expression and low expression group was performed using the Student's t-test.