Jox A, Taquia E, Vockerodt M, Draube A, Pawlita M, Möller P, Bullerdiek J, Diehl V, Wolf J
Department of Internal Medicine I, University of Cologne, Germany.
Cancer Res. 1998 Nov 1;58(21):4930-9.
Fusion of the highly tumorigenic Burkitt's lymphoma (BL) cell line BL60-P7 with the nontumorigenic autologous EBV-immortalized lymphoblastoid cell line (LCL) IARC 277 results in suppression of the tumorigenic phenotype of the parental cell line BL60-P7 after s.c. inoculation into T cell-deficient nude mice. We analyzed whether, after long-term cultivation of these lymphoma hybrid cells, expression of tumorigenicity could be observed and correlated to the loss of particular chromosomes or chromosomal fragments, akin to numerous nonlymphoid hybrid cell models described previously. Two years after fusion, in vitro proliferation of some BL x LCL hybrid cells accelerated, and they partially lost LCL-typical aggregation. However, no major changes in the expression pattern of B cell-associated surface antigens and the EBV latent membrane protein LMP 1 were observed. Cytogenetic evaluation of these cells revealed spontaneous loss of chromosomes. Karyotyping of long-term cultivated hybrid cells demonstrated the occurrence of disomy for each chromosome in at least one metaphase analyzed. Therefore, if suppression of tumorigenicity in these hybrid cells would have been the result of the presence of a single LCL-derived chromosome, there should have been a high probability of its loss, leading to tumorigenic segregants. Surprisingly, the tumorigenic phenotype remained suppressed in nude mice. To induce chromosomal breakage and maldistribution, in addition to spontaneous chromosomal loss, the hybrid cell lines were irradiated at various doses. Again, none of the hybrid cell clones treated in this manner became tumorigenic in nude mice. Immunohistological analysis of the regressing hybrid cell tumors revealed that the hybrid cells had retained their LCL-like differentiation phenotype in vivo. In addition, infiltration with mononuclear cells of murine origin was observed in these regressing hybrid grafts. We conclude that suppression of the tumorigenic Burkitt's lymphoma phenotype in these hybrid cells cannot be attributed to a function encoded by a distinct chromosome or chromosomal fragment. Rather, the unexpected stable nontumorigenic phenotype reflects a LCL-specific activated B-cell phenotype of these hybrids, most probably induced by the expression of numerous copies of episomal latent EBV proteins.
将高致瘤性的伯基特淋巴瘤（BL）细胞系BL60 - P7与非致瘤性的自体EB病毒永生化淋巴母细胞系（LCL）IARC 277融合，在皮下接种到T细胞缺陷的裸鼠后，亲代细胞系BL60 - P7的致瘤表型受到抑制。我们分析了这些淋巴瘤杂交细胞长期培养后，是否能观察到致瘤性的表达，并将其与特定染色体或染色体片段的丢失相关联，这类似于先前描述的许多非淋巴细胞杂交细胞模型。融合两年后，一些BL×LCL杂交细胞的体外增殖加速，并且它们部分失去了LCL典型的聚集性。然而，未观察到B细胞相关表面抗原和EB病毒潜伏膜蛋白LMP 1的表达模式有重大变化。对这些细胞的细胞遗传学评估显示染色体自发丢失。对长期培养的杂交细胞进行核型分析表明，在至少一个分析的中期相中，每条染色体都出现了二体性。因此，如果这些杂交细胞中致瘤性的抑制是单个LCL衍生染色体存在的结果，那么其丢失的可能性应该很高，从而导致致瘤性分离株。令人惊讶的是，裸鼠中的致瘤表型仍然受到抑制。为了诱导染色体断裂和分布异常，除了自发的染色体丢失外，还对杂交细胞系进行了不同剂量的照射。同样，以这种方式处理的杂交细胞克隆在裸鼠中均未变成致瘤性。对消退的杂交细胞肿瘤进行免疫组织学分析表明，杂交细胞在体内保留了其LCL样分化表型。此外，在这些消退的杂交移植物中观察到了鼠源单核细胞的浸润。我们得出结论，这些杂交细胞中致瘤性伯基特淋巴瘤表型的抑制不能归因于由特定染色体或染色体片段编码的功能。相反，这种意外稳定的非致瘤性表型反映了这些杂交细胞的LCL特异性活化B细胞表型，很可能是由游离型潜伏EB病毒蛋白的大量拷贝表达所诱导的。
