Objective: To investigate the effects of DFMO on the growth characteristics, apoptosis and activity of telomerase of K562 cells. Methods: The growth rate, phase distribution of cell cycle and apoptosis of treated cells with DFMO were detected by cell count, morphological assay, FCM analysis and DNA electrophoresis, respectively. The telomerase activity was examined by telomeric repeat amplification protocol(TRAP). Results: In K562 cells treated with DFMO, the growth rate was markedly retarded. The increase in G1 -phase cells and decrease in s-phase population and induction of apoptosis were observed. The activity of telomerase of treated cells was inhibited. Conclusion: The growth inhibition and apoptosis induction of K562 cells treated by DFMO were associated with suppressed telomerase activity. It is suggested that inactivation of telomerase in cancer cells conld be one of important events in antitumor molecular mechanism of inhibition of polyamine biosynthesis.

The inducible c-myc antisense RNA expression plasmid PGXC expressed in mammalian cells was constructed. PGXC was cotransferred with plasmid pSV2neo which confers resistance to Geneticin (G418) to human promyclocytic leukemia cell line HL60. Following the promotion of c-myc antisense RNA expression with Cd~(2+) the growth rate of transfectant HL_(60)~R-9 was significantly slower than that of the parent cells HL60. Flow cytometric analysis indicated a marked increase in Gl fraction and decrease in S-phase population in the cell cycle of transfectants. The differentiation of cellular morphology and function of HL_(60)~R-9 was induced. HL_(60)~R-9 did not form colonies on soft agar and had reduced or lost the tumorigenicity in nude mice.

Orinthine decarboxylase (ODC) is a rate-limiting enzyme in polyamine biosynthesis. Abnormal elevation of ODC activity and subsequent polyamine accumulation are intimately associated with the genesis, development and metastasis of cancer. ODC antisense RNA expression plasmid, pCMV/ODCas, was constructed, with which the cells of human lung squamous carcinoma were transfected by the calcium phosphate precipitation method. After G418 selection, two G418 resistant colonies were obtained. The growth rate, the ability to form colony in soft agar, the biosyntheses of DNA, RNA and proteins, and ODC activities of the two antisense transfectants were significantly suppressed in comparison with the parental cell line. It was demonstrated that these changes were associated with the stable integration of exogenous antisense ODC gene in the genomic DNA of transfectants by analysis of Southern blot and PCR.