PhP-P exerted significant antitumor activity through induction of apoptosis, inhibition of cell proliferation and suppression of angiogenesis, compared with treatment with P-P or PBS

Human PNAS-4 (hPNAS-4), as a pro-apoptotic gene, can inhibit tumor growth when overexpressed in some malignant cells. Poly (lactic-co-glycolic acid) (PLGA) was used as a gene transfer vector due to the advantage of sustained release, nontoxicity and biodegradability. In this study, we aimed to investigate the effect of PLGA nanoparticles encapsulating hPNAS-4 combined with cisplatin (DDP) on ovarian carcinoma. Expression of hPNAS-4 was determined by RT-PCR. Mice bearing intraperitoneal ovarian carcinomas were treated with PBS, pVAX-PLGA nanoparticles (P-P), pVAX-hPNAS4-PLGA nanoparticles (PhP-P), DDP and PhP-P plus DDP, respectively. Intraperitoneal tumors were weighed to assess the antitumor efficacy. The percentage of proliferative cells and apoptotic cells was evaluated by Ki-67 staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. The anti-angiogenic effects were detected by CD31 staining and the alginate-encapsulate assay. Overexpression of hPNAS-4 was detected by RT-PCR in the PhP-P and PhP-P plus DDP groups. PhP-P exerted significant antitumor activity through induction of apoptosis, inhibition of cell proliferation and suppression of angiogenesis, compared with treatment with P-P or PBS alone. The combination of PhP-P with DDP showed enhanced antitumor activity compared with therapy of PhP-P or DDP alone. PLGA encapsulating hPNAS-4 combined with DDP may have promising applications in the therapy of ovarian cancer. Introduction PNAS-4 is identified as a novel pro-apoptotic gene, which can inhibit tumor cell growth through apoptosis. It is activated in the early stage of DNA damage, and consequently exerts the function of inducing apoptosis. Previous studies have shown that PNAS-4 significantly inhibits tumor growth of CT26 colon carcinoma and LL2 lung carcinoma in murine models (1). PNAS-4 has been proven to be a key regulator of cell migration during gastrulation in zebrafish model (2). X. laevis PNAS-4 (xPNAS-4) has been found to be present in early embryo development (3). PNAS-4 was widely expressed in various tissues especially in skeletal muscle (4). The sequence identity between human PNAS-4 (hPNAS-4) protein and mouse, Χenopus and zebrafish PNAS-4 is 96, 87 and 81% respectively (5). Overexpression of hPNAS-4 has been proven to possess the biological activity of inhibiting cell proliferation via inducing cell apoptosis in some tumor cells, such as osteosarcoma, lung carcinoma and ovarian cancer (5-7). Filippov et al have reported that overexpression of hPNAS-4 in the human osteosarcoma cell line-U2O increased cell death via apoptosis (6). The apoptotic mechanisms of hPNAS-4 include activation of a mitochondrial pathway and arrest of the cell cycle in the S phase (5). Ovarian cancer is the leading cause of gynecological cancer mortality. There are an estimated 230,000 new cases of ovarian cancer, resulting in over 140,000 deaths every year (8). Cisplatin (DDP), one of the most important chemotherapy drugs, has been widely used to treat ovarian cancer. However, DDP action on malignant cells is elicited at high DDP doses. The severe toxicity and side-effects owing to the high dose often cause patient intolerance. As a result, a strategy using dual agents rather than a single agent may become a more useful alternative with the purpose of higher antitumor efficiency and lower toxicity. The antitumor effect of DDP derives from its capability to form bifunctional DNA crosslinks, failure to repair damaged DNA, interference with DNA replication, cell cycle arrest, and ultimately apoptosis (10-13). Apoptosis induced by hPNAS-4 also involves DNA damage (8,14). Therefore, in this study, we aimed to utilize the combination therapy of hPNAS-4 with DDP to treat ovarian cancer. Therapeutic efficiency of functional genes mainly depends on effective gene delivery systems (14,15). At present, non-viral Antitumor effects of PLGA nanoparticles encapsulating the human PNAS-4 gene combined with cisplatin in ovarian cancer XIAORONG QI*, XIANGRONG SONG*, PING LIU, TAO YI, SHUANGZHI LI, CHUAN XIE, YU ZHENG, YU BAI, CHUNTANG SUN, YUQUAN WEI and XIA ZHAO Department of Gynecology and Obstetrics, Key Laboratory of Obstetric and Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second Hospital, State Key Laboratory of Biotherapy, Sichuan University, Chengdu 610041, P.R. China Received March 12, 2011; Accepted May 5, 2011 DOI: 10.3892/or.2011.1337 Correspondence to: Professor Xia Zhao, Department of Gynecology and Obstetrics, Key Laboratory of Obstetric and Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second Hospital, State Key Laboratory of Biotherapy, Sichuan University, No. 20, Section 3, South People's Road, Chengdu 610041,