| Ovarian cancer is the sixth most frequent type of cancer among females and is the leading cause of death from gynecological cancer in China, which is accounted for 2.4%~5.6% of female common tumors and is one of the most aggressive human tumors and is virtually incurable. Because it is difficult to be diagnosis in early stage and easy to metastasis, Its incidence and mortality rates are almost identical even though multi-modality treatment, including cytoreductive surgery and cisplatin-containing combination chemotherapy, have usefully prolonged survival. The 5-year survival rate of ovarian cancer is still very low, about 20-40%. Therefore, to inhibit invasion and metastasis will be the key point in the treatment of ovarian cancer. It is well-known that the development of carcinoma is the result of a series of molecular changes occurring in the cells. Genomic alterations have been found to be frequently associated with, development and metastasis of neoplasm. The NM23 gene is a conspicuous metastasis-suppressor gene, and is related to cell growth, differentiation and tumor pathogenesis.In this report, we cloned a different transcript (NM23-H1B) of human NM23-H1. The cDNA is 987 base pairs of length and encodes a protein of 177 amino acid residues. Compared with NM23H1, the cDNA contained an additional NH2-terminal region (25 amino acid residues). It is mapped to 17q21.3 in chromosome and shows that the second exon is not exit in NM23-H1. The expression pattern of NM23-H1B showed that it was ubiquitously expressed in normal tissues (15 tissues except colon) in different levels. Our data also indicated that the expression of transcript in tumor related to tumor differentiation. cDNA microarray analysis by Blast indicated its expression level is move up in some kinds of neoplasms, including liver cancer and gastric carcinoma.24 samples from patients with ovarian tumor at different clinical stages and 4 from normal ovaries were examined for NM23-H1B mRNA expression by using RT-PCR and Northern blot. We found that all samples expressed NM23-H1B mRNA through RT-PCR, while the level of expression in ovarian tumor was higher than that of normal ovary. The results of Northern hybridization showed that NM23-H1B was overexpressed in ovarian cancer while lowexpressed in normal ovary or LMP(low malignant potential, LMP). The level of expression in early stage( I and II stage) cancer was higher than advanced (III and IV stage) cancer. In early stage carcinoma, the expression level was related with the differentiation of tumor cell, well-differentiated cancer expressed NM23-H1B mRNA in comparatively higher level. The result of in situ hybridization showed: expression of NM23-H1B mRNA in ovarian cancer was significantly higher than that in normal ovary or LMP. NM-23H1B mRN was expression mostly in the cytoplasm, seldom in membrane or nucleus.Our experiments suggested that the expression of NM23-N1B in ovarian cancer might be related to tumor inhibition and this kind of inhibition maybe accociated with cell differentiation.
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