Kentaro Fujisawa

Disruption of cell-type-specific methylation at the Maspin gene promoter is frequently involved in undifferentiated thyroid cancers

Cancer-associated DNA hypomethylation is as prevalent as cancer-linked hypermethylation, but the biological significance of DNA hypomethylation in carcinogenesis is less understood. The expression of Maspin (mammary serpin) in differentiated normal cells is regulated by epigenetic modifications in a cell-type-specific manner. Paradoxical Maspin expression due to epigenetic modification has been addressed in several cancer cell types. To elucidate the role of the Maspin gene in thyroid cancer, we studied methylation status in the promoter region and its expression in six human undifferentiated thyroid cancer cell lines and in specimens from 92 primary thyroid tumors, consisting of six follicular adenomas, 56 well-differentiated thyroid cancers (WDTCs), 17 poorly differentiated thyroid cancers (PDTCs) and 13 undifferentiated thyroid cancers (UDTCs). Three of the six cell lines overexpressed Maspin mRNA and its protein product, but the remaining three did not. The methylation status at the promoter region was inversely correlated with Maspin expression. In Maspin-negative cell lines, Maspin expression was induced by treatment with 5-aza-2′-deoxycytidine, a DNA demethylating agent. Immunoreactivity for Maspin protein was frequently detected in UDTCs (8/13, 62%) and PDTCs (7/17, 41%). Immunoreactivity for Maspin was diffusely positive in UDTCs, and was restricted to dedifferentiated components of the tumor in PDTCs. Positive immunoreactivity was infrequent in WDTCs (1/56, 2%), and all follicular adenomas and normal thyroid glands were completely negative. Their methylation status evaluated by the methylation-specific PCR method showed a good inverse correlation with their immunoreactivity in surgically resected specimens. Our data suggest that overexpression of Maspin by DNA hypomethylation is closely associated with morphological dedifferentiation in thyroid cancers.

Prevention of critical telomere shortening by oestradiol in human normal hepatic cultured cells and carbon tetrachloride induced rat liver fibrosis.

Background and aim: Significant telomere shortening of hepatocytes is associated with replicative senescence and a non-dividing state in chronic liver disease, resulting in end stage liver failure and/or development of hepatocellular carcinoma. To prevent critical telomere shortening in hepatocytes, we have focused on oestrogen dependent transactivation of the human telomerase reverse transcriptase (hTERT) gene as a form of telomerase therapy in chronic liver disease. Methods: We examined expression of hTERT mRNA and its protein, and telomerase activity (TA) in three human normal hepatic cell lines (Hc-cells, h-Nheps, and WRL-68) before and after treatment with 17β-oestradiol. The effects of exogenous oestradiol administration were examined in a carbon tetrachloride (CCl4) induced model of liver fibrosis in rats. Results: Expression of hTERT mRNA and its protein was upregulated by oestradiol treatment. Telomere length decreased in Hc-cells and h-Nheps with accumulated passages whereas with long term oestradiol exposure it was greater than without oestradiol. The incidence of β-galactosidase positive cells, indicating a state of senescence, decreased significantly in oestradiol treated cells in comparison with non-treated cells (p<0.05). TA in both male and female rats with CCl4 induced liver fibrosis was significantly higher with oestradiol administration than without (p<0.05). Long term oestradiol administration markedly rescued the hepatic telomere from extensive shortening in both male and female rats. Conclusion: These results suggest that oestradiol acts as a positive modulator of the hTERT gene in the liver. Oestrogen dependent transactivation of the hTERT gene is a new strategy for slowing the progression of chronic liver disease.

Epigenetic status and aberrant expression of the maspin gene in human hepato-biliary tract carcinomas.

We examined expression of maspin and the epigenetic status of its gene in 40 primary hepato-biliary tract carcinomas and 11 cell lines originating from hepato-pancreatico-biliary tract carcinomas. Aberrant maspin expression was frequently observed immunohistochemically in biliary tract carcinomas (22/25, 88%) but not in hepatocellular carcinomas (HCCs) (0/15, 0%). Aberrant maspin expression by five pancreatico-biliary tract carcinoma cell lines was closely associated with demethylation at the maspin promoter. Five of six HCC cell lines were maspin-negative and exhibited extensive hypomethylation and hypoacetylation at the maspin promoter. Treatment with 5-aza-2’-deoxycytidine did not activate maspin expression in these five maspin-negative HCC cell lines, whereas treatment with Trichostatin A (TSA) activated maspin expression in two of them. Treatment with TSA increased histone acetylation in some HCC cell lines. These results suggest that aberrant maspin expression in biliary tract carcinomas is closely associated with demethylation at the promoter region, but that some HCC cell lines additionally require histone acetylation. In addition, the fact that maspin-negative HCC cell lines remain after treatment with TSA suggests the existence of other repressive factors controlling maspin expression.

Primary retroperitoneal spindle cell liposarcoma: Pathological and immunohistochemical findings

Spindle cell liposarcoma (SCLS) is presently regarded as a rare variant of well‐differentiated liposarcoma (WDLPS), which has the potential for aggressive clinical behavior. WDLPS occurs most frequently in the limbs and retroperitoneum. The most common site of SCLS occurrence is the upper limbs or shoulder girdle. Herein we report the first case of primary retroperitoneal SCLS. A 60‐year‐old Japanese man presented with a right inferior abdominal mass. Complete excision of the mass displayed a yellowish spherical tumor with a well‐circumscribed appearance measuring 98 × 95 mm. Pathological examination of the tumor revealed a neural‐like spindle cell proliferation set in a fibrous background that was associated with an atypical lipomatous component, which usually included lipoblasts. Mitotic cells were scarce. Immunohistochemical analysis demonstrated that lipoblasts were S100 positive, spindle cells were CD34 positive, and both spindle cells and lipoblasts were MDM2 negative. The Ki‐67 labeling index was <2%. At one year follow up, the patient was alive without local recurrence or metastasis. Although the proliferative activity of this tumor did not indicate strong malignancy, retroperitoneal liposarcoma generally has a poor prognosis. Accumulation of cases of SCLS is necessary to facilitate a more accurate evaluation of the pathology and clinical behavior of this tumor.