HL-60-AR白血病细胞诱导分化性状的持续性表达

HGPRT~-人早幼粒白血病细胞突变株(HL-60-AR)与RA保温一定时间后,洗去药物继续培养,细胞分化性状(NBT还原能力、细胞膜C_3补体受体及形态变化)不但继续存在,而且能持续表达。撤去RA后连续传代培养,至少在传三代后细胞分化性状仍高度表达。然而,DMSO对HL-60-AR细胞的作用特点明显不同于RA。HL-60-AR细胞分化伴随增殖能力的降低。核酸分子杂交结果表明,细胞c-myc癌基因表达受抑先于细胞分化性状的获得和增殖能力的下降。

CONTINUOUS EXPRESSION OF INDUCED DIFFERENTIATION CHARACTERS IN A HGPRT~- HUMAN PROMYELOCYTIC LEUKEMIA CELL MUTANT (HL-60-AR)

A human promyelocytic leukemia cell mutant (HL-60-AR) with characteristics of resistance to 8-azagunine and deficient in hy-poxanthine and guanine phosphoribosyltrans-ferase had been established from HL-60 cell line in our laboratory.The previous study showed that HL-60-AR mutant cells main-tained the basic biological characteristics and potence of differentiation induced by various compounds of their parental HL-60 cells.In order to investigate the dependence of inducer presence for HL-60-AR cell differentiation,the present experiment was designed that HL-60-AR cells were washed for 3 times to re-move inducer after treatment for various pe-riod,and suspended in medium without indu-cer,then assayed expression of cell differen-tiated characters.Meanwhile,the cultures in which inducer was removed were passaged se-veral generations and assayed to determine the passage hereditary stablization of cell dif-ferentiated characters. Experimental results showed that when HL-60-AR cells incubated in medium without inducer after they had a previous treatment with 10~(-6)M RA for 24 hours,the cell dif-ferentiated characters could be continuous ex-pression and the number of differentiated cells was progressively increased.The increase of NBT reduction positive cells and cell mem-brane C_3 complement receptor positive cells de-tected by YC rosette formation was indepen-dent on the duration of incubation between cells and RA,but it does depend on the ad-ditive duration of cell exposure to RA-contai-ning medium and RA-free medium.The cells which exposed to RA for 24 hours and rein-cubated in RA-free medium for another 120 hours showed kinetics of numbers of differen-tiated cells similar to cells exposed RA for 144 hours (Fig.3,4).This result indicated that cellular commitment to differentiation re-quired an approximately 24 hour exposure to RA.Following this,committed cells continued to differentiate.However,cell differentiated characters induced by DMSO was unstable and reversible. A notable result happened when RA-induced cells were suspended in conventional culture medium and passaged for 3 times,the number of differentiated cells could be de-tected as high as 50 percent.Taken togather the results indicate that after exposure to RA for 24 hours,a significant cell differentiation could be required and cell in populations re-moved from RA thereafter continued to diffe-rentiate.The expression of differentiated cha-racters was irreversible and heritable,exten-ding from parent to daughter cells. It was showed that a cell proliferative arrest could be assayed as HL-60-AR cell dif-ferentiation.The differentiated cells decreasedcell DNA synthesis and number of colony-forming in soft agar medium,and lost the ability of tumor-producing in nude mice.A rapid decrease of c-myc oncogene expression detected by molecular hybridization at the ear-ly stage of RA-treatment indicated that the inhibition of c-myc gene expression might provide some clues for explaining the primary-process and molecular mechanism of HL-60-AR cell differentiation.