Study On Biological Characteristics Of Human Leukemia Cell Lines With High Tumorigenicity In Nude Mice

Objectives we examined the biological characteristics of different clones derived from human leukemia cell lines K562-n and HL6O-n with high tumorigenicity in nude mice which were established from K562 and HiL-60 cell lines respectively, in order to search the cytobiological mechanisms of increased tumorigenicity and the specific karyotypes associated with the high tumorigenicity. Furthermore ,We planed to identify?the genes differentially expressed between high tumorigenic cell line K562-n and the parental K562 cell line by DNA microarrays .we predicted to explore the potential oncogenes and tumor suppressor genes relatived to leukemogenesis and progression of leukemias according to the microarray gene expression analysis. Methods Combined with subcutaneously inoculation in nude mice and culture in vitro, the cell lines K562-n and HL6O-n with high tumorigenicity in nude mice were established from K562 and HL-60 cells respectively.The different clones of K562-n and HL6O-n cells were obtained by limited dilution. Then the biological features of different clones were compared with K562 and HL-60 cells ,in the respect of tuniorigenicity in nude mice , colony formation percentage in soft agar, ultrastructure by electron microscopy, cell cycle distribution by flow cytometer ,the susceptibility to nude mice NK cells and the histopathology of nude mice tuxnors.The cytogenetics analysis of different strains with distinct tumorigenicity was done to observe the chromosome changes relatived to the tumorigenicity.At last,the differential gene expression profiles on genomic scale were identified by the DNA microarray techniques to search the genes associated with the tumorigenicity of leukemia cells in nude mice. Results The high tumorigenicity leukemia cell lines K562-n and HL6O-n were established and several clones with different tumorigenicity of K562-n and HL6O-n were derived .The colony formation percentages in soft agar, especially the large colony formation percentages of the high tumorigenic clone strains K562-B, K562-C, K562-E ,HLL6O-A and HL6O-B were significantly higher than the contrast K562 and HIL-60 cell lines.There were no significantly differences between the low or non- tuniorigenic clone strains K562-A, K562-D, 11L60-E and HL6O-F with the contrast K562 and HL-60 cells. Ultrastructurely, in the high turnorigenic cells , the nuclear is highly abnormal ,the euchromatic element of nuclear chromatin is increased and the heterochromatin is very rare,the microfilaments in cytoplasm are increased and the arrangement was disturbed compared with the paretantal cell lines.The cell cycle analysis by flow cytometer showed higher S phase fractions of high tumorigentic cells. Together with the ultrastructure suggested the proliferation and DNA synthesis is more active in high tumorigenicity cell strains. The study also shows that the killing activities of NK cells to the high clone strains are significant lower than the contrast, which demonstrates the tumorigenicity of leukemia cell lines is negative correlative with the susceptibility to NK cells. The histopathology of nude mice tumors produced by low tumorigenic leukemia cells showed there were many inflammatory cells infiltrated majority were lymphocytes ,and many tumor cells were killed especially in vessel abundant areas . In the contrast, there were rare inflamniatoiy cells infiltrated in the tumors produced by high tumorigenic cell strains, but ischemic necrosis can be seen in the center of the large tumors. The cytogenetic analysis showed the chromosome numbers of K562 cells...