BACKGROUNDThe Notch-regulated ankyrin repeat protein (NRARP) is recently found to promote proliferation of breast cancer cells. The role of NRARP in carcinogenesis deserves extensive investigations. This study attempted to investigate the expression of NRARP in thyroid cancer tissues and assess the influence of NRARP on cell proliferation, apoptosis, cell cycle, and invasion in thyroid cancer.

METHODSThirty-four cases with thyroid cancer were collected from the Department of General Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine between 2011 and 2012. Immunohistochemistry was used to detect the level of NRARP in cancer tissues. Lentivirus carrying NRARP-shRNA (Lenti-NRARP-shRNA) was applied to down-regulate NRARP expression. Cell viability was tested after treatment with Lenti-NRARP-shRNA using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptosis and cell cycle distribution were determined by flow cytometry. Cell invasion was tested using Transwell invasion assay. In addition, expressions of several cell cycle-associated and apoptosis-associated proteins were examined using Western blotting after transfection. Student's t-test, one-way analysis of variance (ANOVA), or Kaplan-Meier were used to analyze the differences between two group or three groups.

RESULTSNRARP was highly expressed in thyroid cancer tissues. Lenti-NRARP-shRNA showed significantly inhibitory activities against cell growth at a multiplicity of infection of 10 or higher (P < 0.05). Lenti-NRARP-shRNA-induced G1 arrest (BHT101: 72.57% ± 5.32%; 8305C: 75.45% ± 5.26%) by promoting p21 expression, induced apoptosis by promoting bax expression and suppressing bcl-2 expression, and inhibited cell invasion by suppressing matrix metalloproteinase-9 expression.

CONCLUSIONDownregulation of NRARP expression exerts significant antitumor activities against cell growth and invasion of thyroid cancer, that suggests a potential role of NRARP in thyroid cancer targeted therapy.

Adult ; Aged ; Animals ; Apoptosis ; genetics ; physiology ; Cell Cycle ; genetics ; physiology ; Cell Line, Tumor ; Cell Proliferation ; genetics ; physiology ; Cell Survival ; genetics ; physiology ; Female ; Humans ; In Vitro Techniques ; Kaplan-Meier Estimate ; Male ; Mice ; Mice, Nude ; Middle Aged ; Neoplasm Proteins ; genetics ; metabolism ; Proteins ; genetics ; metabolism ; RNA, Small Interfering ; genetics ; Thyroid Neoplasms ; genetics ; metabolism ; mortality ; pathology

OBJECTIVE To investigate the effects of aucubin （AU） on the proliferation and tumor growth of prostate cancer （PC） cells by regulating the protein kinase B （Akt）/murine double minute2 （MDM2）/p53 signaling pathway. METHODS Prostate cancer cell PC3 were separated into control group， 50 μmol/L AU group， 100 μmol/L AU group， SC79 （Akt activator） group （5 μmol/L）， and 100 μmol/L AU+SC79 group. The cell cloning and proliferation ability were investigated； the rate of cell apoptosis and the expressions of Akt/MDM2/p53 signaling pathway-related protein were detected. Meanwhile， xenograft tumor models of nude mice were constructed and separated into tumor group， AU group （80 mg/kg）， SC79 group （50 mg/kg）， and AU+SC79 group （80 mg/kg AU+50 mg/kg SC79）， with 10 mice in each group. They were given relevant medicine， once a day， for 21 d. After the last medication， tumor weight was determined， and the expressions of nucleus-associated antigen （Ki-67） and Akt/MDM2/p53 signaling pathway-related protein were detected in tumor tissue. RESULTS In the cell experiment， compared with control group， the cell clonal formation number， proliferation rate and phosphorylation levels of Akt and MDM2 protein in 50 μmol/L AU and 100 μmol/L AU groups were significantly decreased （P＜0.05）， while the cell apoptosis rate and p53 protein expression levels were significantly increased （P＜0.05）； however， the change trend of each index in SC79 group was opposite （P＜0.05）. Compared with 100 μmol/L AU group， the cell clonal formation number， proliferation rate and phosphorylation levels of Akt and MDM2 protein in 100 μmol/L AU+SC79 group were significantly increased （P＜0.05）， while cell apoptosis rate and p53 protein expression levels were significantly decreased （P＜0.05）； however， compared with SC79 group， the changing trend of indexes was the opposite （P＜0.05）. In the in vivo experiment， compared with the tumor group， the tumor mass and Ki-67 positive expression and the phosphorylation levels of Akt and MDM2 protein in nude mice of AU group were significantly decreased （P＜0.05）， and the expression level of p53 protein was significantly increased （P＜0.05）， but the changing trend of above indexes of nude mice in SC79 group were opposite （P＜0.05）. Compared with AU group， the tumor mass， Ki-67 positive expression and phosphorylation levels of Akt and MDM2 protein in tumor tissues of nude mice in AU+SC79 group were significantly increased （P＜0.05）， while the expression level of p53 protein was significantly decreased （P＜0.05）； however， compared with SC79 group， the changing trend of above indexes was opposite （P＜0.05）. CONCLUSIONS AU can inhibit PC cell proliferation and tumor growth by inhibiting Akt/MDM2/p53 signaling pathway.