Cancer-associated expression of minichromosome maintenance 3 gene in several human cancers and its involvement in tumorigenesis.

PURPOSE: The purpose of our study was to identify an unique gene that shows cancer-associated expression, evaluates its potential usefulness in cancer diagnosis, and characterizes its function related to human carcinogenesis. EXPERIMENTAL
DESIGN: We used the differential display reverse transcription-PCR method with normal cervical, cervical cancer and metastatic tissues, and cervical cancer cell line to identify genes overexpressed in cancers.
RESULTS: We identified a minichromosome maintenance 3 (MCM3) gene that was overexpressed in various human cancers, including leukemia, lymphoma, and carcinomas of the uterine cervix, colon, lung, stomach, kidney and breast, and malignant melanoma. Western blot and immunohistochemical analyses also revealed that MCM3 protein was elevated in most of human cancer tissues tested. We compared the MCM3 protein expression levels in human cancers with conventional proliferation markers, Ki-67 and proliferating cell nuclear antigen. MCM3 antibody was the most specific for multiple human cancers, whereas proliferating cell nuclear antigen was relatively less effective in specificity, and Ki-67 failed to detect several human cancers. The down-regulation of MCM3 protein level was examined under serum starvation in both normal and cancer cells. Interestingly, MCM3 protein was stable in MCF-7 breast cancer cells even up to 96 hours after serum starvation, whereas it was gradually degraded in normal BJ fibroblast cells. Nude mice who received injections of HEK 293 cells stably transfected with MCM3 formed tumors in 6 weeks.
CONCLUSIONS: Our study indicates that determination of MCM3 expression level will facilitate the assessment of many different human malignancies in tumor diagnosis, and MCM3 is involved in multiple types of human carcino-genesis.