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Background/aim Previous studies have documented that osteoprotegerin (OPG) is involved in the development and progression of several human malignancies. However, OPG has also been shown to act as a tumor suppressor. The aim of this study was to examine the expression status of OPG in ovarian carcinoma cells and investigate the underlying mechanism responsible for alterations in OPG expression. Materials and methods The expression levels of OPG mRNA and protein were assessed in human ovarian carcinoma cell lines. The methylation status of the OPG promoter region was determined using the bisulfite pyrosequencing technique. The effects of demethylation on OPG expression were also analyzed. Results The human ovarian carcinoma cell lines, SW 626, OVCAR-3, ES-2, TOV-112D, and TOV-21G, expressed significantly lower levels of OPG mRNA and protein than the normal human ovarian epithelial cell line, HS823.Tc. Moreover, three CpG sites in the OPG promoter region were highly methylated in the SW 626, OVCAR-3, ES-2, and TOV-112D ovarian carcinoma cell lines compared to normal control cells. Furthermore, in all the examined ovarian carcinoma cell lines, treatment with the demethylating agent, 5-aza-2-deoxycytidine, resulted in significantly increased expression levels of OPG mRNA and protein compared to the respective pre-treatment levels. Conclusion OPG expression was down-regulated in the studied ovarian carcinoma cells compared to the normal control cells, while demethylation significantly restored OPG expression in the OPG-down-regulated cell lines. Our results suggest that OPG down-regulation in ovarian carcinoma occurs, at least partly, through epigenetic repression, suggesting its involvement in ovarian carcinogenesis.

BACKGROUND B-cell translocation gene 1 (BTG1) acts as a tumour suppressor in human malignancies. However, the precise mechanism of BTG1 down-regulation in colorectal carcinoma (CRC) remains unclear. We analyzed BTG1 expression in CRC cell lines and tissues and investigated the mechanism underlying the observed alterations. MATERIALS AND METHODS Real-time polymerase chain reaction (PCR) and western blot analyses were performed to analyze BTG1 expression in CRC cell lines. The methylation status of the BTG1 promoter region in cell lines was determined by methylation-specific PCR, and the effect of demethylation on BTG1 expression was explored with 5-aza-deoxycytidine treatment. BTG1 protein expression in CRC tissue samples was evaluated using immunostaining. RESULTS CRC cell lines and tissue samples expressed lower levels of BTG1 compared to controls, and BTG1 levels were significantly lower in metastatic than primary CRC. In BTG1-down-regulated CRC cell lines, the BTG1 promoter was highly methylated, and 5-aza-deoxycytidine significantly restored BTG1 expression. CONCLUSION BTG1 down-regulation in CRC occurs through epigenetic repression, which is involved in the development and progression of CRC.

Metaplastic papillary tumor (MPT) of the fallopian tube is a very uncommon lesion, displaying papillary growth of bland-appearing cells with abundant, eosinophilic cytoplasm and mucinous metaplasia. It is difficult for pathologists to determine whether to categorize this lesion as a metaplastic proliferative lesion or a true neoplasm. We recently experienced a case of tubal MPT and initiated a comprehensive review of previously published cases with thorough analysis of clinicopathological characteristics. MPT is typically related to pregnancy, but we describe the first case of pregnancy-unrelated, incidentally detected tubal MPT in a 51-year-old woman who underwent surgery for endometrial cancer. The MPT consisted of small papillary formations with epithelium consisting of nonciliated, columnar cells with abundant eosinophilic cytoplasm arranged as either a single layer or pseudostratified layer. The stroma had a myxoid appearance. Intraluminal and extracellular mucin and floating papillary tufts were observed. Nuclei of the epithelial lining cells were centrally located, rounded or oval, and displayed intranuclear pseudoinclusions or grooves. The MPT cells were positive for paired box 8, epithelial membrane antigen, and cytokeratin. Interestingly, Wilms tumor 1 (WT1) protein was localized within the cytoplasm of MPT cells. Furthermore, the MPT cells did not express phosphatase and tensin homolog deleted on chromosome 10 (PTEN). In summary, MPT of the fallopian tube is a very unusual, distinctive entity displaying unique histopathological features and immunophenotype. Our observation of cytoplasmic WT1 expression and loss of PTEN expression in tubal MPT suggests its neoplastic nature and raises the possibility of WT1 or PTEN involvement in the development of MPT.

Mitotically-active cellular fibroma (MACF) is a rare form of ovarian fibromatous tumor. Although it is generally acknowledged to have indolent biological behavior, its rarity and overlapping histopathological features with more common and aggressive entities make MACF prone to misdiagnosis and overtreatment. The clinicopathological characteristics of ovarian MACF have not been clearly established. Our 10-year review of cellular fibromatous tumors of the ovary diagnosed at a single institution revealed four cases of cellular fibroma (CF) and three cases of MACF. The mean age of patients with MACF was 46 years (range=20-71 years). Patients presented with symptoms related to pelvic masses, such as abdominal pain and discomfort and flank pain. Serum levels of cancer antigen 125 was increased in two patients with MACF. All cases of MACF were a single unilateral tumor. Magnetic resonance imaging revealed solid or mixed solid and cystic ovarian masses with diameters of 7.3-14.9 cm. The radiological impressions included benign stromal tumor, benign epithelial tumor, and borderline epithelial tumor. Grossly, MACFs exhibited yellow-to-tan fleshy cut surfaces, without necrosis or hemorrhage. Extensive hyaline degeneration, resulting in a fibrotic cut surface, was observed in one case. Histologically, MACF displayed frequent mitotic figures, as well as increased cellularity and mild cytological atypia. The mean mitotic count was 8.7 per 10 high-power fields. MACF is a newly-recognized subtype of ovarian cellular fibromatous tumor. Pathologists and clinicians should be aware of this rare entity to prevent misdiagnosis of MACF as fibrosarcoma or adult granulosa cell tumor and resultant overtreatment.