Ramani Vishnu C, Hennings Leah, Haun Randy S
Department of Pathology, Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
BMC Cancer. 2008 Dec 17;8:373. doi: 10.1186/1471-2407-8-373.
In a previous report we have demonstrated that the chymotryptic-like serine protease kallikrein 7 (KLK7/hK7) is overexpressed in pancreatic cancer. In normal skin, hK7 is thought to participate in skin desquamation by contributing in the degradation of desmosomal components, such as desmogleins. Thus, the ability of hK7 to degrade desmogleins was assessed and the effect of hK7 expression on desmoglein 2 was examined in cultured pancreatic cancer cells.
The expression of Dsg1, Dsg2, and Dsg3 in pancreatic tissues was examined by immunohistochemistry and their expression in two pancreatic cancer cell lines, BxPC-3 and Panc-1, was determined by western blot analysis. The ability of hK7 to degrade Dsg1 and Dsg2 was investigated using in vitro degradation assays. BxPC-3 cells stably transfected to overexpress hK7 were used to examine the effect of hK7 on cell-surface resident Dsg2.
The levels of immunoreactive Dsg1 and Dsg2 were reduced in pancreatic adenocarcinomas compared with both normal pancreatic and chronic pancreatitis tissues. Among the desmosomal proteins examined, Dsg2 exhibited robust expression on the surface of BxPC-3 cells. When hK7 was overexpressed in this cell line, there was a significant increase in the amount of soluble Dsg2 released into the culture medium compared with vector-transfected control cells.
A reduction in the amount of the cell adhesion components Dsg1 and Dsg2 in pancreatic tumors suggests that loss of these desmosomal proteins may play a role in pancreatic cancer invasion. Using in vitro degradation assays, both Dsg1 and Dsg2 could be readily proteolyzed by hK7, which is overexpressed in pancreatic adenocarcinomas. The enforced expression of hK7 in BxPC-3 cells that express significant amounts of Dsg2 resulted in a marked increase in the shedding of soluble Dsg2, which is consistent with the notion that aberrant expression of hK7 in pancreatic tumors may result in diminished cell-cell adhesion and facilitate tumor cell invasion.
在之前的一份报告中，我们已经证明胰凝乳蛋白酶样丝氨酸蛋白酶激肽释放酶7（KLK7/hK7）在胰腺癌中过表达。在正常皮肤中，hK7被认为通过参与桥粒成分（如桥粒芯糖蛋白）的降解来参与皮肤脱屑。因此，我们评估了hK7降解桥粒芯糖蛋白的能力，并在培养的胰腺癌细胞中检测了hK7表达对桥粒芯糖蛋白2的影响。
通过免疫组织化学检测胰腺组织中桥粒芯糖蛋白1（Dsg1）、桥粒芯糖蛋白2（Dsg2）和桥粒芯糖蛋白3（Dsg3）的表达，并通过蛋白质印迹分析确定它们在两种胰腺癌细胞系BxPC-3和Panc-1中的表达。使用体外降解试验研究hK7降解Dsg1和Dsg2的能力。使用稳定转染以过表达hK7的BxPC-3细胞来检测hK7对细胞表面驻留的Dsg2的影响。
与正常胰腺组织和慢性胰腺炎组织相比，胰腺腺癌中免疫反应性Dsg1和Dsg2的水平降低。在所检测的桥粒蛋白中，Dsg2在BxPC-3细胞表面表现出强烈表达。当hK7在该细胞系中过表达时，与载体转染的对照细胞相比，释放到培养基中的可溶性Dsg2的量显著增加。
胰腺肿瘤中细胞黏附成分Dsg1和Dsg2的量减少表明这些桥粒蛋白的缺失可能在胰腺癌侵袭中起作用。使用体外降解试验，Dsg1和Dsg2都可以被在胰腺腺癌中过表达的hK7轻易地蛋白水解。在表达大量Dsg2的BxPC-3细胞中强制表达hK7导致可溶性Dsg2的脱落显著增加，这与胰腺肿瘤中hK7的异常表达可能导致细胞间黏附减少并促进肿瘤细胞侵袭的观点一致。
