PURPOSE: Recent discoveries suggest that aberrant DNA methylation provides cancer cells with advanced metastatic properties. However, the precise regulatory mechanisms controlling metastasis genes and their role in metastatic transformation are largely unknown. To address epigenetically-regulated gene products involved in ovarian cancer metastasis, we examined the mechanisms regulating mucin 13 (MUC13) expression and its influence on aggressive behaviors of ovarian malignancies. MATERIALS AND METHODS: We injected SK-OV-3 ovarian cancer cells peritoneally into nude mice to mimic human ovarian tumor metastasis. Overexpression of MUC13 mRNA was detected in metastatic implants from the xenografts by expression microarray analysis and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The DNA methylation status within the MUC13 promoter region was determined using bisulfite sequencing PCR and quantitative methylation-specific PCR. We evaluated the effects of exogenous MUC13 on cell invasion and migration using in vitro transwell assays. RESULTS: MUC13 mRNA expression was up-regulated, and methylation of specific CpG sites within the promoter was reduced in the metastatic implants relative to those in wild-type SK-OV-3 cells. Addition of a DNA methyltransferase inhibitor to SK-OV-3 cells induced MUC13 expression, thereby implying epigenetic regulation of MUC13 by promoter methylation. MUC13 overexpression increased migration and invasiveness, compared to control cells, suggesting aberrant up-regulation of MUC13 is strongly associated with progression of aggressive behaviors in ovarian cancer. CONCLUSION: We provide novel evidence for epigenetic regulation of MUC13 in ovarian cancer. We suggest that the DNA methylation status within the MUC13 promoter region may be a potential biomarker of aggressive behavior in ovarian cancer.
Animals ; Cell Line, Tumor ; *DNA Methylation ; Epigenesis, Genetic ; Female ; *Gene Expression Regulation, Neoplastic ; Heterografts/metabolism ; Humans ; Mice ; Mice, Nude ; Mucins/*genetics/metabolism/physiology ; Neoplasm Invasiveness/genetics ; Ovarian Neoplasms/genetics/*metabolism/pathology ; RNA, Messenger/metabolism

Animals ; Aquaporin 5 ; physiology ; Cytokines ; physiology ; Gene Expression Regulation ; Humans ; Intracellular Signaling Peptides and Proteins ; physiology ; Membrane Proteins ; physiology ; Mucins ; genetics ; Mucus ; secretion ; Myristoylated Alanine-Rich C Kinase Substrate ; Pulmonary Disease, Chronic Obstructive ; metabolism ; Respiratory Mucosa ; secretion ; Signal Transduction

BACKGROUNDChronic obstructive pulmonary disease (COPD) is usually complicated with mucus overproduction in airway. Recently the increased expression of the human calcium-activated chloride channel 1 (CaCC(1)) was found to play an important role in mucus overproduction in the asthmatic airways. To investigate the relationship of CaCC(1) and mucus overproduction in the airway of Chinese patients with COPD, the expressions of CaCC(1), MUC5AC and mucus in bronchial tissues were examined.

METHODSBronchial tissues were obtained from fiberoptic bronchoscopy and bronchial biopsy in West China Hospital from April to July in 2004. Twenty-five patients were diagnosed as the patients with COPD overproduction, and other 20 were the control subjects. The expressions of CaCC(1), MUC5AC and mucin in bronchial tissues were detected by reverse transcriptase-polymerase chain reaction (RT-PCR), in situ hybridization with digoxigenin (DIG)-labeled RNA probe, immunohistochemical and alcian blue-periodic acid Schiff (AB-PAS) staining, respectively.

RESULTSCompared with the control group, the stronger expressions of CaCC(1) were further detected throughout the bronchial tissues from patients with COPD (P < 0.01). Furthermore, the stronger expressions of the CaCC(1) mRNA were related to the severity of airflow obstruction. Samples from COPD showed a stronger staining for MUC5AC than those in control subjects (P < 0.01) and AB-PAS staining revealed more mucins in COPD patients' submucosal gland comparing with that in control subjects (P < 0.01). Expression levels of the CaCC(1) mRNA were respectively negatively correlated with the patients' forced expiratory volume in one second (FEV(1))/forced vital capacity (FVC) data, FEV(1)% predicted data, V(50)% predicted data, V(25)% predicted data (r = -0.43, r = -0.43, r = -0.35, r = -0.36, P < 0.01, P < 0.01, P < 0.05, P < 0.05). While the expression levels of the CaCC(1) mRNA were well correlated with the expression levels of the MUC5AC mRNA of airway epithelium and the PAS-AB stained area of submucosal glands (r = 0.39, r = 0.46, P < 0.05, P < 0.01). Expression levels of the MUC5AC mRNA were negatively correlated with the patients' FEV(1)/FVC data (P = 0.01), FEV(1)% pred data (P = 0.01), V(50)% predicted data, V(25)% predicted data (r = -0.53, r = -0.53, r = -0.48, r = -0.43, P < 0.01, P < 0.01, P < 0.01, P < 0.01). While the expression levels of the MUC5AC mRNA were well correlated with the positively PAS-AB stained area of submucosal gland (P < 0.05), and the correlation coefficients were 0.43.

CONCLUSIONThese results suggest that the stronger gene expression of CaCC(1) exists, complicated with mucus overproduction in the airway of Chinese patients with COPD.

Adult ; Aged ; Bronchi ; metabolism ; Chloride Channels ; genetics ; Female ; Forced Expiratory Volume ; Gene Expression Regulation ; Humans ; Male ; Middle Aged ; Mucin 5AC ; Mucins ; genetics ; Mucus ; physiology ; Pulmonary Disease, Chronic Obstructive ; metabolism ; physiopathology ; RNA, Messenger ; analysis ; Vital Capacity