Kurtzberg J, Hershfield M S
Cancer Res. 1985 Apr;45(4):1579-86.
Cultured human T-lymphoblastoid cell lines are more sensitive than B-cell lines to 2'-deoxyadenosine in the presence of 2'-deoxycoformycin, a potent inhibitor of adenosine deaminase. This difference is related to the greater efficiency with which T-lymphoblasts accumulate cytotoxic levels of dATP derived from the adenosine deaminase substrate 2'-deoxyadenosine (dAdo). Previous work has shown that differences in dATP accumulation by cultured T- and B-lymphoblastoid cell lines cannot be explained by large differences in the levels of dAdo-phosphorylating or dAdo nucleotide (dAXP)-degrading activities in cytoplasmic extracts of these cells, although it has been proposed that intact B-cell lines may catabolize intracellular dAXP more rapidly than do T-cell lines. To further examine the determinants of dAdo sensitivity in T- and B-lymphoblasts, we have studied dAdo and dAXP metabolism in the human T- and B-cell lines CEM and WI-L2 and in hybrids generated by fusion of these cell lines. The hybrid nature of the fusion products was established by nutritional studies and by analyses of cellular surface antigens, DNA content, and enzymatic activities. We found that WI-L2 X CEM hybrids and another T X B hybrid derived from fusion of the SB human B-cell line with CEM were 30- to 40-fold less sensitive to dAdo and about 10-fold less sensitive to the dAdo analogue 9-beta-D-arabinofuranosyladenine than was CEM, or about as resistant as were their B-cell parental lines. Our studies confirm that CEM avidly accumulates dAXP from dAdo but does not catabolize intracellular dAXP. In contrast, WI-L2, SB, and WI-L2 X CEM and SB X CEM hybrids rapidly degraded intracellular dAXP, which limited their ability to undergo dAXP pool expansion. Expression of dAXP catabolic activity in T X B hybrids behaved as a dominant mechanism, conferring resistance to dAdo- and dAdo-related nucleosides to T X B hybrids. It has been postulated that cell fusion may play a role in the progression of tumors and contribute to diversity among the cells that compose clonal tumors. We have speculated that fusion of a malignant T-lymphoblast with an activated B-cell might be a mechanism for the evolution of drug resistance in acute T-cell leukemia.
在腺苷脱氨酶的强效抑制剂2'-脱氧助间型霉素存在的情况下，培养的人T淋巴母细胞系比B细胞系对2'-脱氧腺苷更敏感。这种差异与T淋巴母细胞积累源自腺苷脱氨酶底物2'-脱氧腺苷（dAdo）的细胞毒性水平的dATP的效率更高有关。先前的研究表明，培养的T和B淋巴母细胞系中dATP积累的差异不能用这些细胞胞质提取物中dAdo磷酸化或dAdo核苷酸（dAXP）降解活性的巨大差异来解释，尽管有人提出完整的B细胞系可能比T细胞系更快地分解代谢细胞内的dAXP。为了进一步研究T和B淋巴母细胞中dAdo敏感性的决定因素，我们研究了人T和B细胞系CEM和WI-L2以及由这些细胞系融合产生的杂交细胞中的dAdo和dAXP代谢。通过营养研究以及细胞表面抗原、DNA含量和酶活性分析确定了融合产物的杂交性质。我们发现，WI-L2×CEM杂交细胞以及另一种由SB人B细胞系与CEM融合产生的T×B杂交细胞对dAdo的敏感性比CEM低30至40倍，对dAdo类似物9-β-D-阿拉伯呋喃糖基腺嘌呤的敏感性低约10倍，或者与它们的B细胞亲代系一样耐药。我们的研究证实，CEM能从dAdo中大量积累dAXP，但不会分解代谢细胞内的dAXP。相比之下，WI-L2、SB以及WI-L2×CEM和SB×CEM杂交细胞会迅速降解细胞内的dAXP，这限制了它们进行dAXP池扩展的能力。T×B杂交细胞中dAXP分解代谢活性的表达表现为一种主导机制，赋予T×B杂交细胞对dAdo和与dAdo相关核苷的抗性。据推测，细胞融合可能在肿瘤进展中起作用，并有助于构成克隆性肿瘤的细胞之间的多样性。我们推测恶性T淋巴母细胞与活化B细胞的融合可能是急性T细胞白血病中耐药性演变的一种机制。
