Werkmeister J A, Pross H F, Roder J C
Int J Cancer. 1983 Jul 15;32(1):71-8. doi: 10.1002/ijc.2910320112.
Neuraminidase treatment of parental and butyrate-induced K562 tumor cells was associated with an increase in natural killer (NK) susceptibility of these target cells. The degree of enhancement with neuraminidase was significantly greater for the NK-resistant (NRR) butyrate-differentiated K562 cells so that the relative difference between the parental NK-sensitive (NKS) K562 line and its induced NKR variants, in terms of NK sensitivity, was no longer five- or six-fold but only two-fold. The predominant reason for the altered NK susceptibilities of the target cells after neuraminidase treatment was an increase in the target-cell-binding ability of these cells as assessed by a direct conjugate-forming cell assay using Percoll-enriched NK cells and cold target competition assays. The enhancement did not appear to be due simply to an increased membrane-membrane attraction caused by a reduction of net negative cell surface charges since protamine sulphate, a positively charged molecule, had no effect on NK activity. Compared with the NKS parental K562 tumor cells, the NKR butyrate-induced cells had 3.6- to 4.0-fold higher sialo-transferase activities and were associated with significantly greater amounts of cell surface sialic acid detected both in sialyl glycoproteins (2.2- to 2.9-fold higher) and particularly within ganglioside extracts (6.2- to 13.6-fold higher). In conformity with the marked neuraminidase enhancement of NK-mediated cytolysis of the butyrate-induced targets, these NKR cells were associated with significantly enhanced levels of neuraminidase-accessible sialic acid compared to the NKS parental K562 cell line. Other parameters such as sensitivity to superoxide radicals, intrinsic superoxide dismutase levels, altered membrane repair mechanisms and transferrin competition, were not significantly different between the NKS and NKR target phenotypes. Sugar inhibition studies demonstrated an enhanced inhibition against the butyrate-induced cells with a variety of neutral sugars. The degree of inhibition with phosphorylated sugars was comparable between the parental and induced K562 tumor target cells and is consistent with our previous findings showing that these hexose phosphates may be inhibiting cytolysis at a step independent of target-cell recognition.
用神经氨酸酶处理亲代K562肿瘤细胞和丁酸盐诱导的K562肿瘤细胞，会使这些靶细胞对自然杀伤（NK）的敏感性增加。对于NK抗性（NRR）丁酸盐分化的K562细胞，神经氨酸酶的增强程度显著更高，因此亲代NK敏感（NKS）K562细胞系与其诱导的NKR变体之间在NK敏感性方面的相对差异不再是五倍或六倍，而仅为两倍。神经氨酸酶处理后靶细胞NK敏感性改变的主要原因是，通过使用Percoll富集的NK细胞的直接共轭形成细胞测定法和冷靶竞争测定法评估，这些细胞的靶细胞结合能力增加。这种增强似乎并非仅仅由于净负细胞表面电荷减少导致的膜 - 膜吸引力增加，因为带正电荷的分子硫酸鱼精蛋白对NK活性没有影响。与NKS亲代K562肿瘤细胞相比，NKR丁酸盐诱导的细胞具有高3.6至4.0倍的唾液酸转移酶活性，并且在唾液酸糖蛋白（高2.2至2.9倍）中，特别是在神经节苷脂提取物中（高6.2至13.6倍）检测到的细胞表面唾液酸量显著更多。与亲代K562细胞系相比，这些NKR细胞与显著增强的神经氨酸酶可及唾液酸水平相关，这与丁酸盐诱导的靶细胞的NK介导的细胞溶解的显著神经氨酸酶增强一致。其他参数，如对超氧自由基的敏感性、内在超氧化物歧化酶水平、改变的膜修复机制和转铁蛋白竞争，在NKS和NKR靶表型之间没有显著差异。糖抑制研究表明，多种中性糖对丁酸盐诱导的细胞的抑制作用增强。磷酸化糖的抑制程度在亲代和诱导的K562肿瘤靶细胞之间相当，这与我们之前的发现一致，即这些己糖磷酸可能在独立于靶细胞识别的步骤中抑制细胞溶解。
