Dept. of Radiation Oncology, TU München and Helmholtz Zentrum München (HMGU), CCG-Innate Immunity in Tumor Biology, Germany.
Radiother Oncol. 2011 Jun;99(3):313-6. doi: 10.1016/j.radonc.2011.05.051. Epub 2011 Jun 23.
The major stress-inducible heat shock protein 70 (Hsp70) is frequently overexpressed in highly aggressive tumors, and elevated intracellular Hsp70 levels mediate protection against apoptosis. Following therapeutic intervention, such as ionizing irradiation, translocation of cytosolic Hsp70 to the plasma membrane is selectively increased in tumor cells and therefore, membrane Hsp70 might serve as a therapy-inducible, tumor-specific target structure.
Based on the IgG1 mouse monoclonal antibody (mAb) cmHsp70.1, we produced the Hsp70-specific recombinant Fab fragment (Hsp70 Fab), as an imaging tool for the detection of membrane Hsp70 positive tumor cells in vitro and in vivo.
The binding characteristics of Hsp70 Fab towards mouse colon (CT26) and pancreatic (1048) carcinoma cells at 4 °C were comparable to that of cmHsp70.1 mAb, as determined by flow cytometry. Following a temperature shift to 37 °C, Hsp70 Fab rapidly translocates into subcellular vesicles of mouse tumor cells. Furthermore, in tumor-bearing mice Cy5.5-conjugated Hsp70 Fab, but not unrelated IN-1 control Fab fragment (IN-1 ctrl Fab), gradually accumulates in CT26 tumors between 12 and 55 h after i.v. injection.
In summary, the Hsp70 Fab provides an innovative, low immunogenic tool for imaging of membrane Hsp70 positive tumors, in vivo.
主要应激诱导热休克蛋白 70（Hsp70）在高度侵袭性肿瘤中经常过表达，细胞内 Hsp70 水平升高可介导对细胞凋亡的保护。在治疗干预后，如电离辐射，细胞质 Hsp70 向质膜的易位在肿瘤细胞中被选择性增加，因此，膜 Hsp70 可能作为治疗诱导的、肿瘤特异性的靶结构。
基于 IgG1 小鼠单克隆抗体（mAb）cmHsp70.1，我们产生了 Hsp70 特异性重组 Fab 片段（Hsp70 Fab），作为体外和体内检测膜 Hsp70 阳性肿瘤细胞的成像工具。
Hsp70 Fab 在 4°C 时对小鼠结肠（CT26）和胰腺（1048）癌细胞的结合特性与 cmHsp70.1 mAb 相当，这是通过流式细胞术确定的。在温度升高至 37°C 后，Hsp70 Fab 迅速转位到小鼠肿瘤细胞的亚细胞小泡中。此外，在荷瘤小鼠中，Cy5.5 缀合的 Hsp70 Fab，但不是无关的 IN-1 对照 Fab 片段（IN-1 ctrl Fab），在静脉注射后 12 至 55 小时之间逐渐积聚在 CT26 肿瘤中。
总之，Hsp70 Fab 为体内膜 Hsp70 阳性肿瘤的成像提供了一种创新的、低免疫原性的工具。
