Alpaugh M L, Lee M C, Nguyen M, Deato M, Dishakjian L, Barsky S H
Department of Pathology, UCLA School of Medicine, Los Angeles, California 90024, USA.
Exp Cell Res. 2000 Nov 25;261(1):150-8. doi: 10.1006/excr.2000.5056.
Myoepithelial cells surround incipient ductal carcinomas of the breast and exert anti-invasive and antiangiogenic effects in vitro through the elaboration of suppressor molecules. This study examines one putative molecule, solubilized CD44 produced by myoepithelial shedding of membrane CD44. Studies with different human myoepithelial cell lines demonstrate that myoepithelial cells express and shed both the 85-kDa standard (CD44s) and the 130-kDa epithelial (CD44v8-10) isoforms, findings further confirmed by the use of isoform-specific antibodies. PMA pretreatment enhances CD44 shedding detected by two different methods at different time points: a reduction in surface CD44 at 2 h by flow cytometry and a marked decrease in both total cellular CD44 and plasma membrane CD44 at 12 h by Western blot. This shedding is both specific for CD44 and specific for myoepithelial cells. This shedding is inhibited by the chymotrypsin inhibitors chymostatin and alpha(1)-antichymotrypsin but not by general metallo-, cysteine, or other serine proteinase inhibitors. Myoepithelial-cell-conditioned medium and affinity-purified solubilized CD44 from this conditioned medium block hyaluronan adhesion and migration of both human carcinoma cell lines and human umbilical vein endothelial cells.
肌上皮细胞围绕乳腺早期导管癌，并在体外通过分泌抑制分子发挥抗侵袭和抗血管生成作用。本研究检测了一种假定分子，即膜型CD44经肌上皮细胞脱落产生的可溶性CD44。对不同人肌上皮细胞系的研究表明，肌上皮细胞表达并脱落85 kDa标准型（CD44s）和130 kDa上皮型（CD44v8 - 10）异构体，使用异构体特异性抗体进一步证实了这一发现。佛波酯（PMA）预处理在不同时间点通过两种不同方法增强了CD44的脱落：流式细胞术检测显示2小时时表面CD44减少，蛋白质印迹法检测显示12小时时总细胞CD44和质膜CD44均显著减少。这种脱落对CD44具有特异性，对肌上皮细胞也具有特异性。这种脱落受到糜蛋白酶抑制剂抑糜酶素和α1 -抗糜蛋白酶的抑制，但不受一般金属蛋白酶、半胱氨酸蛋白酶或其他丝氨酸蛋白酶抑制剂的抑制。肌上皮细胞条件培养基以及从该条件培养基中亲和纯化的可溶性CD44可阻断透明质酸对人癌细胞系和人脐静脉内皮细胞的黏附与迁移。
