Regulation of carcinoma cell invasion by protein C inhibitor whose expression is decreased in renal cell carcinoma

Abstract

Protein C inhibitor (PCI), a member of the serine protease inhibitor family, is produced in various human tissues, including the liver, kidney and testis. In addition to inhibiting the anticoagulant protein C pathway, PCI also inhibits urinary plasminogen activator (uPA), which is a well-known mediator of tumor cell invasion. In the present study, to clarify the biologic significance of PCI in the kidney, we compared the expression of PCI between human renal cell carcinoma (RCC) tissue and nontumor kidney tissue. The PCI antigen level in RCC tissue was found to be significantly lower than in nontumor kidney tissue, and expression of PCI mRNA was detected in normal renal proximal tubular epithelial cells (RPTEC), but not in RCC or in an RCC cell line (Caki-1 cells). Key words: protein C inhibitor; urinary plasminogen activator; renal cell carcinoma; tumor invasionProtein C inhibitor (PCI) was originally identified as an inhibitor of the anticoagulant protease, activated protein C, 1 and was subsequently found to inhibit other proteases involved in blood coagulation and fibrinolysis, such as thrombin, 2 thrombin-thrombomodulin complex, 3 factor Xa, 2 factor XIa, 4 plasma kallikrein 4 and urinary plasminogen activator (uPA). 5 Human plasma PCI is believed to be produced mainly by the liver, 6 but is also synthesized in the kidneys and the reproductive organs, including the testis, seminal vesicles and ovary. 7,8 Thus, besides its function in the regulation of blood coagulation, PCI may also play a role in the regulation of reproduction. Recently, Uhrin et al. 9 reported that PCI knockout male mice are apparently healthy but infertile, and that this infertility is caused by abnormal spermatogenesis induced by destruction of the Sertoli cell barrier. In the kidneys, PCI is mainly synthesized by proximal tubular epithelial cells, 10 and most urinary PCI is present in complex with uPA, 11 which it inhibits; hence, PCI is also referred to as plasminogen activator inhibitor-3 (PAI-3). However, the physiologic role of uPA inhibition by PCI in the urinary tract is unknown.It is known that metastasis and invasion of various tumor cells are mediated by uPA and its receptor. 12 uPA is inhibited by PAI-1 and PAI-2, 13 the former of which has been reported to be essential for regulation of tumor cell invasion and metastasis by promoting angiogenesis. 14,15 Previously, it was shown that the expression of uPA is lower, that the expression of uPA receptor is moderately higher and that the expression of PAI-1 is significantly higher in human renal cell carcinoma (RCC) than in nontumor kidney tissue. 16,17 Furthermore, Swiercz et al. 18 suggested that the expression of uPA, its receptor and PAI-1 correlate with the aggressive phenotype of RCC. These studies suggest the importance of the plasminogen activator system, including uPA, its receptor and PAI-1, in the process of RCC tumor cell invasion; however, there is no direct evidence yet that uPA regulates the invasiveness of RCC cells. It is also known that uPA and/or plasmin may ...

Farnesyltransferase inhibitor SCH‐66336 downregulates secretion of matrix proteinases and inhibits carcinoma cell migration

“…This is supported by results showing that Caki-1 cells exhibit lower invasive capacity when uPA activity is reduced by added anti-uPA antibody and PAI-1. 31 Interestingly, an in vivo assay with another FTI, L-744,832, also showed inhibition of growth of 3 human prostate tumor xenographs in nude mice. 42 High levels of plasminogen activators as well as MMP-2 and MMP-9 have been correlated with aggressive phenotypes in different cancers, including prostate 27 and renal 43 cancers.…”

“…30 The in vitro invasiveness of renal cancer Caki-1 cells, which express uPA, was significantly enhanced by addition of uPA but inhibited by antiuPA antibody and PAI-1. 31 Together, these data suggested that prostate PC-3 and renal Caki-1 cancer cells could be excellent models for investigating the ability of SCH-66336 to regulate the expression and activity of gelatinases and of components of the plasminogen activation system.…”

Protein C inhibitor inhibits breast cancer cell growth, metastasis and angiogenesis independently of its protease inhibitory activity

“…14 Palmieri et al showed that adhesion to extracellular matrix proteins such as fibronectin, vitronectin, and laminin is increased in breast cancer cells overexpressing PCI as compared to control cells; this effect appears to be partially mediated by integrin, whose expression is also enhanced in PCI-expressing breast cancer cells as compared to mock-transfected cells. 15 On the other hand, we demonstrated that PCI expression is significantly decreased in the RPTEC-derived renal carcinoma cell line, Caki-1 cells, and that PCI inhibits in vitro the Matrigel invasion of renal carcinoma cells by inhibiting uPA 16 ; however, we could not evaluate the effect of PCI on tumor metastasis in vivo because Caki-1 cells were not able to grow even in severe combined immunodeficient (SCID) mice. 16 Therefore, it remains still unclear whether PCI is able to regulate in vivo the metastatic activity of tumor cells.…”

“…15 On the other hand, we demonstrated that PCI expression is significantly decreased in the RPTEC-derived renal carcinoma cell line, Caki-1 cells, and that PCI inhibits in vitro the Matrigel invasion of renal carcinoma cells by inhibiting uPA 16 ; however, we could not evaluate the effect of PCI on tumor metastasis in vivo because Caki-1 cells were not able to grow even in severe combined immunodeficient (SCID) mice. 16 Therefore, it remains still unclear whether PCI is able to regulate in vivo the metastatic activity of tumor cells.In the present study, we investigated (i) the effect of recombinant intact PCI, reactive site-modified (Arg354 to Ala) PCI (R354APCI), or N-terminal fragment of protease-cleaved PCI (NTPCI), on the in vitro invasiveness of MDA-231 cells, (ii) the in vitro invasiveness of MDA-231 breast cancer cells expressing intact PCI, R354APCI or NTPCI, and (iii) the growth and metastatic potential of intact PCI, R354APCI, or NTPCI-expressing MDA-231 cells. In addition, we investigated the effect of intact PCI, R354APCI, or NTPCI on angiogenesis, which is known to be important for tumor growth and metastasis.…”

“…15 On the other hand, we demonstrated that PCI expression is significantly decreased in the RPTEC-derived renal carcinoma cell line, Caki-1 cells, and that PCI inhibits in vitro the Matrigel invasion of renal carcinoma cells by inhibiting uPA 16 ; however, we could not evaluate the effect of PCI on tumor metastasis in vivo because Caki-1 cells were not able to grow even in severe combined immunodeficient (SCID) mice. 16 Therefore, it remains still unclear whether PCI is able to regulate in vivo the metastatic activity of tumor cells.…”