Experimental Studies On The Function Of Ndr2 In Human Lymphoid Hematopoietic Tissues

Ndr2 belongs to the Ndr gene family. Human Ndr2 was first cloned by our group in Jan. 2000. Preliminary studies showed that Ndr2 was widely expressed in 72 kinds of human tissues, with the highest expression in brain; Ndr2 was a differentially expressed gene between brain and glioma. To further probe into the distribution and potential role of human Ndr2, in this experiment the expression and function of Ndr2 in human lymphoid hematopoietic tissues were studied using tissue pathological and molecular biological techniques. We also investigated the differential expression of Ndr2 in other four kinds of tissues and their relative tumors.The major findings of the present work are as follows:1. In situ hybridization demonstrated that Ndr2 mRNA signal weredispersive in lymphocytes of the cortex section of human lymph node; RT-PCR showed the expression of Ndr2 mRNA in 5 kinds of lymphoid tumor cell lines (JurkaU Raji, U937> YT and HL60); Ndr2 immunoreactivity was found in the cytoplasm of Jurkat and Raji cells as well as lymphocytes of human lymph node as evidenced by immunohistochemistry. Both the Ndr2 mRNA and protein level were found to be higher in normal PBMC than in the PBMC of ALL and CLL patients.2. With the proliferation of PBMC, Ndr2 mRNA and protein level showed a decreasing tendency; N-myc mRNA showed no significant changes; well c-myc mRNA steadily increased. These suggest that Ndr2 may exert an inhibitory effect on the proliferation of PBMC; Ndr2 and N-myc have no correlation in the process of cell proliferation.3. N-myc ASODN was used to block the expression of N-myc in Jurkat and Raji cells. After N-myc blockage, Ndr2 mRNA and protein level were found to be enhanced greatly in Raji cells, but no significant changes were found in Jurkat cells. Flow cytometry showed Gl phase arrest of Raji cells and apoptosis of Jurkat cells induced by N-myc ASODN.4. Transient transfection of Ndr2 in Raji cells induced Gl phase arrest, accompanied by decreased protein level of cyclinDl and cyclinE. This finding suggest that the potential inhibitory effect of Ndr2 on proliferation may be due to its disturbance of cell cycle via changed expression of different cyclins.5. Ndr2 expression were also observed in brain and glioma, lung and lung cancer, stomach and carcinoma of stomach, colon and carcinoma of colon, with the highest expression in brain. Ndr2 mRNA were higher in brain and lung that glioma and lung cancer respectively, which suggest that Ndr2 may participate in the development of neural and respiratory tumors. No significant differences were found between digestive system and their relative tumors.These findings about the distribution of Ndr2 in human tissues and theirrelative tumors, especially the results from lymphoid hematopoietic tissues, have provided a basis for the following work to wholly unravel the function of Ndr2 and its potential role in the development of tumor.