Veveris-Lowe T L, Lawrence M G, Collard R L, Bui L, Herington A C, Nicol D L, Clements J A
School of Life Sciences and Science Research Centre, Queensland University of Technology, Brisbane, Australia.
Endocr Relat Cancer. 2005 Sep;12(3):631-43. doi: 10.1677/erc.1.00958.
Prostate-specific antigen (PSA) and the related kallikrein family of serine proteases are current or emerging biomarkers for prostate cancer detection and progression. Kallikrein 4 (KLK4/hK4) is of particular interest, as KLK4 mRNA has been shown to be elevated in prostate cancer. In this study, we now show that the comparative expression of hK4 protein in prostate cancer tissues, compared with benign glands, is greater than that of PSA and kallikrein 2 (KLK2/hK2), suggesting that hK4 may play an important functional role in prostate cancer progression in addition to its biomarker potential. To examine the roles that hK4, as well as PSA and hK2, play in processes associated with progression, these kallikreins were separately transfected into the PC-3 prostate cancer cell line, and the consequence of their stable transfection was investigated. PC-3 cells expressing hK4 had a decreased growth rate, but no changes in cell proliferation were observed in the cells expressing PSA or hK2. hK4 and PSA, but not hK2, induced a 2.4-fold and 1.7-fold respective increase, in cellular migration, but not invasion, through Matrigel, a synthetic extracellular matrix. We hypothesised that this increase in motility displayed by the hK4 and PSA-expressing PC-3 cells may be related to the observed change in structure in these cells from a typical rounded epithelial-like cell to a spindle-shaped, more mesenchymal-like cell, with compromised adhesion to the culture surface. Thus, the expression of E-cadherin and vimentin, both associated with an epithelial-mesenchymal transition (EMT), was investigated. E-cadherin protein was lost and mRNA levels were significantly decreased in PC-3 cells expressing hK4 and PSA (10-fold and 7-fold respectively), suggesting transcriptional repression of E-cadherin, while the expression of vimentin was increased in these cells. The loss of E-cadherin and associated increase in vimentin are indicative of EMT and provides compelling evidence that hK4, in particular, and PSA have a functional role in the progression of prostate cancer through their promotion of tumour cell migration.
前列腺特异性抗原（PSA）以及相关的激肽释放酶丝氨酸蛋白酶家族是目前或正在兴起的用于前列腺癌检测和病情进展监测的生物标志物。激肽释放酶4（KLK4/hK4）尤其值得关注，因为KLK4信使核糖核酸在前列腺癌中已被证明有所升高。在本研究中，我们现在表明，与良性腺组织相比，hK4蛋白在前列腺癌组织中的相对表达高于PSA和激肽释放酶2（KLK2/hK2），这表明hK4除了具有生物标志物潜力外，可能在前列腺癌进展中发挥重要的功能作用。为了研究hK4以及PSA和hK2在与病情进展相关过程中所起的作用，将这些激肽释放酶分别转染到PC-3前列腺癌细胞系中，并研究其稳定转染的后果。表达hK4的PC-3细胞生长速率降低，但在表达PSA或hK2的细胞中未观察到细胞增殖的变化。hK4和PSA，但不是hK2，分别使通过基质胶（一种合成细胞外基质）的细胞迁移增加了2.4倍和1.7倍，但未增加侵袭。我们推测，表达hK4和PSA的PC-3细胞所表现出的这种运动性增加可能与这些细胞中观察到的结构变化有关，即从典型的圆形上皮样细胞转变为纺锤形、更具间充质样的细胞，对培养表面的粘附能力受损。因此，研究了与上皮-间质转化（EMT）相关的E-钙粘蛋白和波形蛋白的表达。在表达hK4和PSA的PC-3细胞中，E-钙粘蛋白蛋白丢失且信使核糖核酸水平显著降低（分别降低了10倍和7倍），这表明E-钙粘蛋白受到转录抑制，而这些细胞中波形蛋白的表达增加。E-钙粘蛋白的丢失和波形蛋白的相应增加表明发生了EMT，并提供了令人信服的证据，表明尤其是hK4和PSA通过促进肿瘤细胞迁移在前列腺癌进展中发挥功能作用。
