Increased expression of cyclin G1 in leiomyoma compared with normal myometrium

OBJECTIVE: The purpose of this study was to detect the expression of cyclin G1 in leiomyoma and to investigate the alteration of its expression compared with normal myometrial tissue that was obtained from the same patient. STUDY DESIGN: With the use of Northern blot analysis, Western blot analysis, and immunohistochemistry, we analyzed the-expression of cyclin G1 in 24 patients who underwent hysterectomies. RESULTS: We found that messenger RNA levels of cyclin G1 were elevated in human leiomyomas compared with their adjacent normal myometrial tissues. Consistent with elevated messenger RNA levels, high levels of cyclin G1 protein expression were detected by immunoblot analysis in all leiomyoma samples. Immunohistochemistry revealed that cyclin G1 is located mainly in the nucleus in both normal myometrium and leiomyoma. However, higher levels of cyclin G1 were apparent in tumor regions compared with adjacent normal myometrial regions. In addition, we found the expression levels of other cyclins (4 and E) and CDK2 were elevated in leiomyomas compared with normal myometrium. Because cyclin G1 is a transcriptional target of the p53 tumor suppressor, we examined the p53 status of all eight leiomyoma samples and found no p53 mutations. CONCLUSION: These results suggest that cyclin 131 is frequently overexpressed in uterine leiomyoma in a p53-independent manner and that this abnormality could be attributed to the severe proliferation of human uterine leiomyomas.