Beinlich A, Strohmeier R, Kaufmann M, Kuhl H
Department of Gynecology and Obstetrics, Johann-Wolfgang-Goethe University, 60590, Frankfurt, Germany.
Biochem Pharmacol. 2000 Aug 1;60(3):397-402. doi: 10.1016/s0006-2952(00)00325-7.
Peripheral benzodiazepine receptor (PBR) agonist [(3)H]Ro5-4864 has been shown to bind with high affinity to the human breast cancer cell line BT-20. Therefore, we investigated different human breast cancer cell lines with regard to binding to [(3)H]Ro5-4864 and staining with the PBR-specific monoclonal antibody 8D7. Results were correlated with cell proliferation characteristics. In flow cytometric analysis, the estrogen receptor (ER)-negative breast cancer cell lines BT-20, MDA-MB-435-S, and SK-BR-3 showed significantly higher PBR expression (relative fluorescence intensity) than the ER-positive cells T47-D, MCF-7 and BT-474 (P<0.05). Accordingly, BT-20 and MDA-MB-435-S had the highest capacity for binding [(3)H]-Ro5-4864, while the ER-positive cells exhibited only low binding of the benzodiazepine. PBR expression correlated inversely with cell doubling time (r = 0.78) and positively with Ki-67 expression (r = 0.77). The amount of mitochondria was significantly higher in cells with high PBR expression. As PBR could be demonstrated only after permeabilization of cells, PBR is suggested to be localized within the cytoplasm. Moreover, colocalization of PBR and mitochondria was shown by confocal microscopy analysis. The highest amounts of both PBR and mitochondria were found in cell lines with high mitotic activity. Therefore, it is concluded that the level of PBR is dependent on the number of mitochondria. PBR and its putative endogenous ligand diazepam-binding inhibitor are possibly involved in the regulation of cell proliferation of human breast cancer cell lines.
外周苯二氮䓬受体（PBR）激动剂[³H]Ro5-4864已被证明能与人类乳腺癌细胞系BT-20高亲和力结合。因此，我们研究了不同人类乳腺癌细胞系与[³H]Ro5-4864的结合情况以及用PBR特异性单克隆抗体8D7进行染色的情况。结果与细胞增殖特征相关。在流式细胞术分析中，雌激素受体（ER）阴性的乳腺癌细胞系BT-20、MDA-MB-435-S和SK-BR-3的PBR表达（相对荧光强度）显著高于ER阳性细胞T47-D、MCF-7和BT-474（P<0.05）。相应地，BT-20和MDA-MB-435-S对[³H]-Ro5-4864的结合能力最强，而ER阳性细胞对苯二氮䓬的结合能力较低。PBR表达与细胞倍增时间呈负相关（r = 0.78），与Ki-67表达呈正相关（r = 0.77）。PBR表达高的细胞中线粒体数量显著更高。由于只有在细胞通透后才能检测到PBR，因此推测PBR定位于细胞质中。此外，共聚焦显微镜分析显示PBR与线粒体共定位。在有高有丝分裂活性的细胞系中发现PBR和线粒体的含量最高。因此，得出结论：PBR的水平取决于线粒体的数量。PBR及其假定的内源性配体地西泮结合抑制剂可能参与人类乳腺癌细胞系的细胞增殖调节。
