Differential Expression Of Nucleostemin In The Tumour Of Human Colorectum

Nucleostemin (NS), a new P53-binding protein which is located in the nucleus of stem cell and cancer cell, could regulate the self-renewal and multiplication of stem cell and cancer cell. With the development of research, Nucleostemin plays an important role in regulating the multiplication of stem cell and cancer cell. At present, nucleostemin is a putative proliferative marker for stem cell and cancer cell, but little is known about whether it could be used as a biomarker in molecular diagnosis and classification on clinic tumor. The main purpose of this study was to investigate the characteristic of NS expression and localization in human colorectal carcinoma (CRC) and to determine the relationship between NS expression and colon cancer classification. Firstly we collected 40 colorectal samples from clinic operation including adenoma and carcinoma. By means of immunohistochemistry and Western blot, the expression characteristic of NS was observed on the transformed cell of colorectum. By comparing the expression patterns of NS of different grades of CRC with Ki-67 expression, it was possibly to achieve the purpose of the study.By immunohistochemical staining, we detected NS positive (NS+) nucleolus in most of the nucleus of CRC cells. However, the number of NS+ nucleolus or nucleolar organizer region (NOR) were significantly increased in the cells of grade I CRC, but gradually decreased as tumor trends to grade II and III CRC. Oppositely, the size of each NS+nucleolus was gradually increased from grade I to grade III CRC. Western blot analyses demonstrated that the difference of NS expression was not statistically significant among three grades CRC. However, NS expression was significantly higher in metastatic CRC by compared with that of un-metastatic CRC. NS expression exhibited some similarities to that of Ki-67 in tumor cell proliferation and differentiation although they were showed in nucleolus and nucleus respectively.We conclude that during tumorgenesis, NS appeared in the NOR of precancerous cell (adenoma) is an early events in initiating tumorgenesis, Grade I CRC cell exhibited more and larger NS+NOR than benign adenoma. Afterwards, NOR fused together to be one or two larger NS+nucleoli as the tumour cell progressed to grade II or III CRC. Because these results of NS expression have some relationship with clinic CRC pathological alteration, NS might be a promise new marker in molecular diagnosis and classification of CRC tumors.