PubMed · 7491534
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J M Monchik. 1995. Normocalcemic hyperparathyroidism.. https://doi.org/10.1016/s0039-6060(05)80094-7
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The high mobility group As (HMGAs) belong to a family of nonhistone nuclear proteins that orchestrate the assembly of nucleoprotein complexes. Through a complex network of protein-DNA and protein-protein interaction, they play important roles in gene transcription, recombination, and chromatin structure. This protein family is involved, through different mechanisms, in both benign and malignant neoplasias. We have recently reported that transgenic mice carrying the Hmga1 or Hmga2 genes under transcriptional control of the cytomegalovirus promoter develop pituitary adenomas secreting prolactin and growth hormone. We have shown that the mechanism of the HMGA2-induced pituitary adenoma is based on the increased E2F1 activity. The expression profile of mouse normal pituitary glands and adenomas induced in HMGA transgenic mice revealed an increased expression of the ccnb2 gene, coding for the cyclin B2 protein, in the neoplastic tissues compared with the normal pituitary gland. Here, we show, by electrophoretic mobility shift assay and chromatin immunoprecipitation, a direct binding of HMGA proteins to the promoter of ccnb2 gene, whereas luciferase assays showed that HMGAs are able to up-regulate ccnb2 promoter activity. Finally, we report an increased CCNB2 expression in human pituitary adenomas of different histotypes that is directly correlated with HMGA1 and HMGA2 expression. Because cyclin B2 is involved in the regulation of the cell cycle, these results taken together indicate that HMGA-induced cyclin B2 overexpression gives an important contribution to experimental and human pituitary tumorigenesis.
BACKGROUND: It still is unclear when angiogenic potential, which is believed to be a prerequisite for tumor development, is acquired. The current study was designed 1) to clarify when the phenotypic change of angiogenicity occurs during the development of colon carcinoma and 2) to investigate the possible roles of vascular endothelial growth factor (VEGF) and p53 in angiogenesis. METHODS: Colon carcinomas were classified according to the following criteria: m carcinomas were tumors in which carcinoma cells were observed within the mucosa (excluding adenomas with severe atypia) according to the World Health Organization criteria. sm carcinomas were defined by invasion into the submucosa but not into the muscularis propria. Using 27 adenomas, 26 m carcinomas, and 20 sm carcinomas, VEGF expression was analyzed with reverse transcriptase-polymerase chain reaction and immunohistochemistry. Microvessel density, VEGF, and p53 status were evaluated by immunohistochemistry. RESULTS: Neither VEGF mRNA nor VEGF protein was detected in any of the mild-to-moderate dysplastic adenomas, whereas 16 of 26 m carcinomas (62%) and all sm carcinomas exhibited VEGF protein. The microvessel density in adenomas, m carcinomas, and sm carcinomas was 3 +/- 0.55, 6.1 +/- 1.12, and 12 +/- 1.35 (0.739 mm(2) per field), respectively. In m carcinomas, positive VEGF expression was coincident with the expression of p53, and stainability for both VEGF and p53 was similar with regard to spatial distribution in tumor tissues. In m and sm carcinomas, there was a statistically significant correlation between the intensity of VEGF expression and microvessel density. CONCLUSIONS: The results of the current study demonstrated that angiogenesis develops in association with tumor progression from adenoma to noninvasive colorectal carcinoma, at least in part due to VEGF, and suggested that VEGF in m carcinomas is induced by mutant p53, although alternative mechanisms of VEGF up-regulation may exist in sm carcinomas.
A homozygous mutation at bp 677 in the gene for the methylenetetrahydrofolate reductase (MTHFR) was previously shown to be associated with a decreased risk of colorectal cancer. We examined the relation between the MTHFR genetic polymorphism and risk of colorectal adenoma in Japanese men using 205 cases of colorectal adenomas and 220 controls of normal total colonoscopy. The homozygous mutation was not measurably associated with colorectal adenomas. The findings corroborate the lack of an association between the MTHFR genotype and colorectal adenomas, but do not deny the possibility that the genotype may be involved in the late stage of colorectal carcinogenesis.