Plasminogen activator inhibitor-2(PAI-2) overexpression supportsbladder cancer developmentin PAI-1 knockout mice in N-butyl-N-(4-hydroxybutyl)-nitrosamine- induced bladdercancer mouse model

Hideki Furuya,Fumie Igari,Charles J Rosser,Yutaro Tsukikawa,Ian Pagano,Yijun Sun,Keith S Chan,Yoshiko Shimizu,Kanani Hokutan,Rafael Peres,Kazukuni Hayashi,Runpu Chen,Nari Kim,Owen T M Chan

doi:10.1186/s12967-020-02239-6

Abstract

BackgroundAccumulating evidence suggests that plasminogen activator inhibitor-1 (PAI-1) plays an important role in bladder tumorigenesis by regulating cell cycle. However, it remains unclear whether and how inhibition of PAI-1 suppresses bladder tumorigenesis.MethodsTo elucidate the therapeutic effect of PAI-1 inhibition, we tested its tumorigenicity in PAI-1 knockout (KO) mice exposed to a known bladder carcinogen.ResultsPAI-1 deficiency did not inhibit carcinogen-induced bladder cancer in mice although carcinogen-exposed wild type mice significantly increased PAI-1 levels in bladder tissue, plasma and urine. We found that PAI-1 KO mice exposed to carcinogen tended to upregulate protein C inhibitor (PAI-3), urokinase-type plasminogen activator (uPA) and tissue-type PA (tPA), and significantly increased PAI-2, suggesting a potential compensatory function of these molecules when PAI-1 is abrogated. Subsequent studies employing gene expression microarray using mouse bladder tissues followed by post hoc bioinformatics analysis and validation experiments by qPCR and IHC demonstrated that SERPING1 is further downregulated in PAI-1 KO mice exposed to BBN, suggesting that SERPING1 as a potential missing factor that regulate PAI-2 overexpression (compensation pathway).ConclusionsThese results indicate that serpin compensation pathway, specifically PAI-2 overexpression in this model, supports bladder cancer development when oncoprotein PAI-1 is deleted. Further investigations into PAI-1 are necessary in order to identify true potential targets for bladder cancer therapy.

Highlights

Accumulating evidence suggests that plasminogen activator inhibitor-1 (PAI-1) plays an important role in bladder tumorigenesis by regulating cell cycle
PAI‐1 levels are upregulated in tissues, plasma and urine by butyl-N-(4-hydroxybutyl) nitrosamine (BBN) To confirm that Plasminogen activator inhibitor-1 (PAI-1) is overexpressed by BBN in our animals, we analyzed PAI-1 levels in mouse bladders during BBN exposure using real-time RT-polymerase chain reaction (PCR)
BBN exposure to wild type (WT) mice significantly increased PAI-1 expression at week 20 when 50% of BBN-exposed mice developed muscle invasive bladder cancer (MIBC) (P < 0.01, Table 1)

Summary

Introduction

Accumulating evidence suggests that plasminogen activator inhibitor-1 (PAI-1) plays an important role in bladder tumorigenesis by regulating cell cycle. It remains unclear whether and how inhibition of PAI-1 suppresses bladder tumorigenesis. The canonical function of PAI-1 is inhibition of tissue plasminogen activator (tPA) and uPA to maintain clot formation and plays a major role in non-neoplastic disorders, such as deep vein thrombosis, myocardial infarction, atherosclerosis, and stroke [4, 5]. We have reported that mRNA and protein levels of PAI-1 are elevated in voided urine from patients with BCa [8,9,10,11,12,13]. We confirmed that the protein expression of PAI-1 was increased in actual bladder tumors, compared to benign controls and PAI-1 expression levels were higher in muscle invasive bladder cancer (MIBC) compared with non-muscle invasive bladder cancer (NMIBC) [14, 15]

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Discussion

Conclusion