Sarcione E J, Hart D
Int J Cancer. 1985 Mar 15;35(3):315-8. doi: 10.1002/ijc.2910350306.
Direct evidence was obtained for de novo synthesis of AFP by MCF-7 human breast cancer cells per se. Synthesis was demonstrated by L-14C-leucine and L-35S-methionine incorporation into immunochemically isolated AFP, and confirmed by radioimmunodiffusion and radioimmunoelectrophoresis. This information indicates that AFP synthesis is associated with normal and neoplastic cells of several different histotypes, and suggests that AFP detected and measured previously in primary human breast cancer tissue cytosol (Sarcione et al., 1983) also resulted from in situ biosynthesis by breast cancer cells per se rather than uptake of exogenous AFP originating from extracellular sources. Evidence that AFP obtained after treatment of 14C-leucine radiolabelled MCF-7 breast cancer cell protein with 0.4 M KCl contained 2.6 times more radioactivity than did AFP obtained before such salt treatment is interpreted as indicating that two different molecular species of de novo synthesized AFP existed in breast cancer cells: (1) larger amount of non-immunoreactive AFP which became immunoreactive and measurable after KCl treatment, and (2) smaller amounts of free immunoreactive AFP. 14C-radiolabelled AFP obtained before and after treatment of cell protein with 0.4 M KCl codiffused, comigrated with alpha 1 electrophoretic mobility and gave an identical radioimmunologic reaction both with each other and with added carrier human cord serum AFP. Furthermore, preliminary studies indicated that radiolabelled non-immunoreactive AFP could be separated from lower-molecular-weight free AFP by chromatography on Sephadex G-200. Taken together, these findings suggest that synthesized free AFP was bound as a non-immunoreactive high-molecular-weight macromolecular complex rather than being covalently linked. Our current working hypothesis is that most of the de novo synthesized endogenous AFP in MCF-7 human breast cancer cells was rapidly and reversibly bound by hydrophobic bonding to a specific cytoplasmic AFP-receptor.
获得了MCF - 7人乳腺癌细胞自身从头合成甲胎蛋白（AFP）的直接证据。通过将L - 14C - 亮氨酸和L - 35S - 甲硫氨酸掺入免疫化学分离的AFP中证明了合成，并通过放射免疫扩散和放射免疫电泳得到证实。该信息表明AFP合成与几种不同组织类型的正常细胞和肿瘤细胞相关，并表明先前在原发性人乳腺癌组织胞质溶胶中检测和测量到的AFP（Sarcione等人，1983年）也是由乳腺癌细胞自身原位生物合成产生的，而不是摄取源自细胞外来源的外源性AFP。用0.4 M KCl处理14C - 亮氨酸放射性标记的MCF - 7乳腺癌细胞蛋白后获得的AFP所含放射性比盐处理前获得的AFP多2.6倍，这一证据被解释为表明乳腺癌细胞中存在两种不同分子种类的从头合成AFP：（1）大量非免疫反应性AFP，在KCl处理后变为免疫反应性且可测量，以及（2）少量游离免疫反应性AFP。用0.4 M KCl处理细胞蛋白前后获得的14C - 放射性标记的AFP共扩散、共迁移，具有α1电泳迁移率，并且彼此之间以及与添加的载体人脐血清AFP产生相同的放射免疫反应。此外，初步研究表明，放射性标记的非免疫反应性AFP可通过在Sephadex G - 200上进行色谱分离与低分子量游离AFP分离。综上所述，这些发现表明合成的游离AFP以非免疫反应性高分子量大分子复合物的形式结合，而不是通过共价连接。我们目前的工作假设是，MCF - 7人乳腺癌细胞中大多数从头合成的内源性AFP通过疏水键与特定的细胞质AFP受体快速且可逆地结合。
