Mediation of renal cyst formation by hepatocyte growth factor

Computational drug discovery approaches identify mebendazole as a candidate treatment for autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a rare genetic disorder characterised by numerous renal cysts, the progressive expansion of which can impact kidney function and lead eventually to renal failure. Tolvaptan is the only disease-modifying drug approved for the treatment of ADPKD, however its poor side effect and safety profile necessitates the need for the development of new therapeutics in this area. Using a combination of transcriptomic and machine learning computational drug discovery tools, we predicted that a number of existing drugs could have utility in the treatment of ADPKD, and subsequently validated several of these drug predictions in established models of disease. We determined that the anthelmintic mebendazole was a potent anti-cystic agent in human cellular and in vivo models of ADPKD, and is likely acting through the inhibition of microtubule polymerisation and protein kinase activity. These findings demonstrate the utility of combining computational approaches to identify and understand potential new treatments for traditionally underserved rare diseases.

Development of crizotinib-associated renal cyst in a non-small cell lung cancer patient with ALK fusion: a case report and review of the literature

BACKGROUND

Crizotinib, an oral first-generation tyrosine kinase inhibitor (TKI), is superior to systemic chemotherapy for the treatment of non-small cell lung cancer (NSCLC) with positive rearrangement of anaplastic lymphoma kinase (ALK). However, an increased incidence of renal and hepatic cysts has been reported in the patients on crizotinib treatment.

CASE PRESENTATION

Here, we describe a case of a 71-year-old Chinese women developed multiple cystic lesions in kidney and liver during crizotinib treatment for the primary and metastatic NSCLC. The renal and hepatic cysts were noted by CT scan 3 months after crizotinib treatment, which were spontaneously and significantly regressed after stopping crizotinib.

CONCLUSIONS

Based on literature review and our experience in this case report, we concluded that crizotinib-associated renal cyst (CARCs) has features of malignancy and abscess in radiographic imaging, and thus, pathological confirmation is necessary to avoid inappropriate treatment decision. In addition, to benefit the patients with progress-free survival (PFS), switching from crizotinib to alectinib is recommended for the treatment of NSCLC patients who developed CARCs.

Small hairpin inhibitory RNA delivery in the metanephric organ culture identifies long noncoding RNA Pvt1 as a modulator of cyst growth

Autosomal dominant polycystic kidney disease (ADPKD) is a monogenic disorder characterized by the formation of kidney cysts that originate from the epithelial tubules of the nephron and primarily results from mutations in polycystin-1 (PKD1) and polycystin-2 (PKD2). The metanephric organ culture (MOC) is an ex vivo system in which explanted embryonic kidneys undergo tubular differentiation and kidney development. MOC has been previously used to study polycystic kidney disease as treatment with 8-bromo-cAMP induces the formation of kidney cysts. However, the inefficiency of manipulating gene expression in MOC has limited its utility for identifying genes and pathways that are involved in cystogenesis. Here, we used a lentivirus and three serotypes of self-complementary adeno-associated viral (scAAV) plasmids that express green fluorescent protein and found that scAAV serotype D/J transduces the epithelial compartment of MOC at an efficiency of 68%. We used scAAV/DJ to deliver shRNA to knockdown Pvt1, a long noncoding RNA, which was upregulated in kidneys from Pkd1 and Pkd2 mutant mice and humans with ADPKD. shRNA delivery by scAAV/DJ downregulated expression of Pvt1 by 45% and reduced the cyst index by 53% in wild-type MOCs and 32% in Pkd1-null MOCs. Knockdown of Pvt1 decreased the level of c-MYC protein by 60% without affecting Myc mRNA, indicating that Pvt1 regulation of c-MYC was posttranscriptional. These results identify Pvt1 as a long noncoding RNA that modulates cyst progression in MOC.NEW & NOTEWORTHY This study identified scAAV/DJ as effective in transducing epithelial cells of the metanephric organ culture (MOC). We used scAAV/DJ shRNA to knockdown Pvt1 in cystic MOCs derived from Pkd1-null embryos. Downregulation of Pvt1 reduced cyst growth and decreased levels of c-MYC protein. These data suggest that suppression of Pvt1 activity in autosomal dominant polycystic kidney disease might reduce cyst growth.

Renal Abscess Caused by Crizotinib: A Rare Case Report

Crizotinib is a tyrosine kinase inhibitor that has been found to be effective in the treatment of c-ros oncogene 1-positive non-small cell lung cancer. Although this targeted agent for treating cancer has shown superiority to standard chemotherapy in some ways, this drug has adverse effects, such as the development of renal abscesses. Some associated renal damage may disappear with crizotinib withdrawal. Hence, we present the case of a 58-year-old man with non-small cell lung cancer on crizotinib therapy who developed bilateral renal abnormal space-occupying lesions, successively which were difficult to identify using various imaging methods; even PET-CT highly suspected the right renal masses as malignant. Finally, the right renal lesions were confirmed as renal abscesses by postoperative pathology. The left renal lesion was considered as renal cysts through the lesion disappearing after crizotinib withdrawal. There have been very few reports in this respect, especially proved by various methods and confirmed by postoperative pathology. It is important to recognize this drug-related complication in order to avoid incorrect diagnosis and inadequate therapy. It is necessary to monitor renal changes after taking crizotinib.

Diverse Receptor Tyrosine Kinase Phosphorylation in Urine-Derived Tubular Epithelial Cells from Autosomal Dominant Polycystic Kidney Disease Patients

BACKGROUNDS

The clinical features of autosomal dominant polycystic kidney disease (ADPKD) differ among patients even if they have the same gene mutation in PKD1 or PKD2. This suggests that there is diversity in the expression of other modifier genes or in the underlying molecular mechanisms of ADPKD, but these are not well understood.

METHODS

We primarily cultured solute carrier family 12 member 3 (SLC12A3)-positive urine-derived distal tubular epithelial cells from 6 ADPKD patients and 4 healthy volunteers and established immortalized cell lines. The diversity in receptor tyrosine kinase (RTK) phosphorylation by phospho-RTK array in immortalized tubular epithelial cells was analyzed.

RESULTS

We noted diversity in the activation of several molecules, including Met, a receptor of hepatocyte growth factor (HGF). Administration of golvatinib, a selective Met inhibitor, or transfection of small interfering RNA for Met suppressed cell proliferation and downstream signaling only in the cell lines in which hyperphosphorylation of Met was observed. In three-dimensional culture of Madin-Darby canine kidney (MDCK) cells as a cyst formation model of ADPKD, HGF activated Met, resulting in an increased total cyst number and total cyst volume. Administration of golvatinib inhibited these phenotypes in MDCK cells.

CONCLUSION

Analysis of urine-derived tubular epithelial cells demonstrated diverse RTK phosphorylation in ADPKD, and Met phosphorylation was noted in some patients. Considering the difference in the effects of golvatinib on immortalized tubular epithelial cells among patients, this analysis may aid in selecting suitable drugs for individual ADPKD patients.

Molecular pathways involved in injury-repair and ADPKD progression

The major hallmark of Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the formation of many fluid-filled cysts in the kidneys, which ultimately impairs the normal renal structure and function, leading to end-stage renal disease (ESRD). A large body of evidence suggests that injury-repair mechanisms are part of ADPKD progression. Once cysts have been formed, proliferation and fluid secretion contribute to the cyst size increase, which eventually causes stress on the surrounding tissue resulting in local injury and fibrosis. In addition, renal injury can cause or accelerate cyst formation. In this review, we will describe the various mechanisms activated during renal injury and tissue repair and show how they largely overlap with the molecular mechanisms activated during PKD progression. In particular, we will discuss molecular mechanisms such as proliferation, inflammation, cell differentiation, cytokines and growth factors secretion, which are activated following the renal injury to allow the remodelling of the tissue and a proper organ repair. We will also underline how, in a context of PKD-related gene mutations, aberrant or chronic activation of these developmental pathways and repair/remodelling mechanisms results in exacerbation of the disease.

Alectinib Induced Regression of Renal and Hepatic Cysts Caused by Crizotinib

Background

Crizotinib is the first tyrosine kinase inhibitor approved for the treatment of anaplastic lymphoma kinase (ALK) rearranged non-small cell lung cancer (NSCLC). An increased incidence of renal cysts has been described during the crizotinib treatment.

Case Presentation

We herein report the case of a 74-year-old woman who received crizotinib for metastatic ALK-positive NSCLC. During the crizotinib treatment, complex renal cystic lesions with invasion of perirenal spaces and iliopsoas muscle appeared; two complex hepatic cysts were also observed. Almost all lesions disappeared after switching to alectinib, a second-generation ALK inhibitor.

Conclusion

It would seem that alectinib is able to reduce in size and number hepatic and renal cysts caused by the crizotinib treatment. Nevertheless, further studies are needed to clarify the role of both crizotinib in the onset of renal and hepatic cysts and alectinib in their disappearance.

Renal complication of crizotinib: Crizotinib-associated complex renal cyst

Crizotinib is one of the first generations of tyrosine kinase inhibitors targeting anaplastic lymphoma kinase(ALK) and is recently found to be associated with the development of complex renal cysts with inconclusive explanation up to this time. Hereby, we discuss the hypothesis of Crizotinib-associated complex renal cyst development and coexisting renal impairment after initiation of the treatment in a 75-year-old man with ALK-positive non-small cell lung cancer whose complex renal cysts evolved after initiation and cessation of Crizotinib treatment. The coexistence as renal impairment persisted even after switching from Crizotinib to Ceritinib.

Polycystic Kidney Disease and Renal Fibrosis

Polycystic kidney disease (PKD) is a common genetic disorder characterized by formations of numerous cysts in kidneys and most caused by PKD1 or PKD2 mutations in autosomal dominant polycystic kidney disease (ADPKD). The interstitial inflammation and fibrosis is one of the major pathological changes in polycystic kidney tissues with an accumulation of inflammatory cells, chemokines, and cytokines. The immune response is observed across different stages and occurs prior to or coincident with cyst formation in ADPKD. Evidence for inflammation as an important contributor to cyst growth and fibrosis includes increased interstitial macrophages, upregulated expressions of pro-inflammatory cytokines, activated complement system, and activated pathways including NF-κB and JAK-STAT signaling in polycystic kidney tissues. Inflammatory cells are responsible for overproduction of several pro-fibrotic growth factors which promote renal fibrosis in ADPKD. These growth factors trigger epithelial mesenchymal transition and myofibroblast/fibrocyte activation, which stimulate the expansion of extracellular matrix (ECM) including collagen I, III, IV, V, and fibronectin, leading to renal fibrosis and reduced renal function. Besides, there are imbalanced ECM turnover regulators which lead to the increased ECM production and inadequate degradation in polycystic kidney tissues. Several fibrosis associated signaling pathways, such as TGFβ-SMAD, Wnt, and periostin-integrin-linked kinase are also activated in polycystic kidney tissues. Although the effective anti-fibrotic treatments are limited at the present time, slowing the cyst expansion and fibrosis development is very important for prolonging life span and improving the palliative care of ADPKD patients. The inhibition of pro-fibrotic cytokines involved in fibrosis might be a new therapeutic strategy for ADPKD in the future.

Renal Injury during Long-Term Crizotinib Therapy

Crizotinib is highly effective against anaplastic lymphoma kinase-positive and c-ros oncogen1-positive non-small cell lung cancer. Renal dysfunction is associated with crizotinib therapy but the mechanism is unknown. Here, we report a case of anaplastic lymphoma kinase positive non-small cell lung cancer showing multiple cysts and dysfunction of the kidneys during crizotinib administration. We also present results demonstrating that long-term crizotinib treatment induces fibrosis and dysfunction of the kidneys by activating the tumor necrosis factor-α/nuclear factor-κB signaling pathway. In conclusion, this study shows the renal detrimental effects of crizotinib, suggesting the need of careful monitoring of renal function during crizotinib therapy.

Crizotinib Associated Renal Cysts [CARCs]: incidence and patterns of evolution

Background

Novel therapeutic agents recently introduced for the treatment of cancer have several unusual side effects. An increased incidence of renal cystic lesions, often with features concerning for malignancy or infection, has been reported in patients with anaplastic lymphoma kinase (ALK) - rearranged advanced non-small cell lung cancer (NSCLC) treated with Crizotinib. Many of these lesions undergo spontaneous resolution despite developing complex features on imaging. We assess the incidence and patterns of evolution of Crizotinib Associated Renal Cysts [CARCs] at our institute and provide histopathology correlation of their benign nature.

Methods

A retrospective analysis of renal lesions in computerised tomography (CT) scans of 35 patients with advanced ALK-rearranged NSCLC who had been prescribed crizotinib at our institution was performed by three radiologists, who analysed the evolution of these lesions, particularly for pre-defined significant and complex changes.

Results

Of 26 patients eligible for this analysis, 4 (15%) had cysts at baseline that remained stable on crizotinib treatment while 11(42%) developed significant change in 28 renal cysts. Commonest pattern of cyst evolution was enlargement from baseline followed by spontaneous regression (17/28 lesions) while other patterns noted were stable lesions, regression from baseline and ongoing enlargement. The median maximum size reached was 23 mm (range 9 – 67 mm) after a median of 178 days (160 to 1342) on crizotinib. Complex change occurred in 12 cysts, in 7/26 (27%) patients and within 60 days of starting Crizotinib in 10 cysts. Imaging features were falsely concerning for malignancy or abscess in 4/26 patients.

Conclusion

Most CARCs resolve spontaneously, or have a benign evolution despite enlargement and other features concerning for malignancy or infection on imaging. This unusual manifestation of chemotherapy should be recognised, particularly by radiologists, so that inappropriate treatment decisions are avoided.

Renal Toxicities of Targeted Therapies

With the incorporation of targeted therapies in routine cancer therapy, it is imperative that the array of toxicities associated with these agents be well-recognized and managed, especially since these toxicities are distinct from those seen with conventional cytotoxic agents. This review will focus on these renal toxicities from commonly used targeted agents. This review discusses the mechanisms of these side effects and management strategies. Anti-vascular endothelial growth factor (VEGF) agents including the monoclonal antibody bevacizumab, aflibercept (VEGF trap), and anti-VEGF receptor (VEGFR) tyrosine kinase inhibitors (TKIs) all cause hypertension, whereas some of them result in proteinuria. Monoclonal antibodies against the human epidermal growth factor receptor (HER) family of receptors, such as cetuximab and panitumumab, cause electrolyte imbalances including hypomagnesemia and hypokalemia due to the direct nephrotoxic effect of the drug on renal tubules. Cetuximab may also result in renal tubular acidosis. The TKIs, imatinib and dasatinib, can result in acute or chronic renal failure. Rituximab, an anti-CD20 monoclonal antibody, can cause acute renal failure following initiation of therapy because of the onset of acute tumor lysis syndrome. Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, can result in proteinuria. Discerning the renal adverse effects resulting from these agents is essential for safe treatment strategies, particularly in those with pre-existing renal disease.

The renal effects of ALK inhibitors

Anaplastic lymphoma kinase 1 (ALK-1) is a member of the insulin receptor tyrosine kinase family. In clinical practice, three small molecule inhibitors of ALK-1 are used, namely crizotinib, ceritinib and alectinib. Several more agents are in active pre-clinical and clinical studies. Crizotinib is approved for the treatment of advanced ALK-positive non-small cell lung cancer (NSCLC). According to the package insert and published literature, treatment with crizotinib appears to be associated with kidney failure as well as an increased risk for the development and progression of renal cysts. In addition, this agent is associated with development of peripheral edema and rare electrolyte disorders. This review focuses on the adverse renal effects of Crizotinib in clinical practice.

Development of renal cysts after crizotinib treatment in advanced ALK-positive non-small-cell lung cancer

INTRODUCTION

The development of complex renal cysts after crizotinib treatment for non-small-cell lung cancer (NSCLC) is a reported side effect. However, its occurrence and characteristics have not been reported.

METHODS

Medical records and computed tomography images of crizotinib-treated patients in three prospective clinical trials were reviewed. The size and Bosniak category of the renal cysts before and after crizotinib treatment were determined. Patients' clinical characteristics, tumor stage, treatment response, renal function, and outcomes were analyzed.

RESULTS

During December 2010 to March 2013, we enrolled 32 patients who received crizotinib. There were 23 patients who had renal cysts before crizotinib. The median follow-up time was 493 days. Seven patients (22%, six with baseline renal cyst and one without baseline renal cyst) had significant renal cyst change. Four (13% of all) had new complex renal cysts. The median time from crizotinib treatment to first recognization of significant renal cyst change was 77 days. After stopping crizotinib, complex renal cysts regressed significantly. Patients with significant renal cyst change received more previous anticancer therapy (median, 5 lines versus 3 lines, p = 0.04) and received crizotinib for longer duration (median, 956 days versus 248 days, p = 0.007) compared with those without significant renal cyst change.

CONCLUSIONS

Change of renal cysts after crizotinib treatment is not uncommon. Development of complex renal cysts reverses after stopping crizotinib.

[Renal cysts - A novel complication of crizotinib treatment for lung cancer]

We report the case of a woman with an ALK positive lung adenocarcinoma, who developed bilateral complex renal cysts 17 months after the introduction of treatment with crizotinib. Clinical investigation led to the conclusion that the cysts were due to anticancer drug. Regression of the renal cysts was observed one month after cessation of the crizotinib. This case illustrates that specific and little known toxicities can occur with these novel molecules which have entered use for the management of lung cancer.

Complex renal cysts associated with crizotinib treatment

An apparent causal association between crizotinib treatment and renal cyst development emerged during clinical trials in anaplastic lymphoma kinase (ALK)-positive non-small cell lung cancer (NSCLC). Serious adverse event (SAE) reports of renal cysts from a safety database of 1375 patients from four clinical trials were reviewed. A blinded, retrospective, independent radiologic review (IRR) was performed using scans from patients on study for ≥ 6 months in three clinical trials; risk factors for renal cyst development were assessed. Among 17 patients with renal cysts reported as SAEs, evidence of invasion into adjacent structures was noted in seven patients, with no evidence of malignancy found. These patients generally did not require dose reductions, none required permanent crizotinib discontinuation due to this AE, and most continued treatment with clinical benefit. In the blinded IRR, among 255 crizotinib-treated patients, 22%, 3%, and 2% had preexisting simple cysts, complex cysts, or both, respectively. At the 6-month tumor assessment, 9% of all patients had acquired new cysts, and 2% of patients with preexisting cysts had developed new cysts and enlargements (>50%) of preexisting simple cysts. Asians appeared to have an increased risk of developing new cysts on treatment; Koreans in particular had 5.18 times higher odds of developing cysts than non-Asians (95% confidence interval, 1.51-17.78; P = 0.05). Crizotinib treatment appears to be associated with an increased risk of development and progression of renal cysts in patients with ALK-positive NSCLC. While close monitoring is recommended, dosing modification was not generally necessary, allowing patients to remain on crizotinib treatment.

Exploitation of the Polymeric Immunoglobulin Receptor for Antibody Targeting to Renal Cyst Lumens in Polycystic Kidney Disease

Autosomal-dominant polycystic kidney disease (ADPKD) is a common life-threatening genetic disease that leads to renal failure. No treatment is available yet to effectively slow disease progression. Renal cyst growth is, at least in part, driven by the presence of growth factors in the lumens of renal cysts, which are enclosed spaces lacking connections to the tubular system. We have shown previously shown that IL13 in cyst fluid leads to aberrant activation of STAT6 via the IL4/13 receptor. Although antagonistic antibodies against many of the growth factors implicated in ADPKD are already available, they are IgG isotype antibodies that are not expected to gain access to renal cyst lumens. Here we demonstrate that targeting antibodies to renal cyst lumens is possible with the use of dimeric IgA (dIgA) antibodies. Using human ADPKD tissues and polycystic kidney disease mouse models, we show that the polymeric immunoglobulin receptor (pIgR) is highly expressed by renal cyst-lining cells. pIgR expression is, in part, driven by aberrant STAT6 pathway activation. pIgR actively transports dIgA from the circulation across the cyst epithelium and releases it into the cyst lumen as secretory IgA. dIgA administered by intraperitoneal injection is preferentially targeted to polycystic kidneys whereas injected IgG is not. Our results suggest that pIgR-mediated transcytosis of antagonistic antibodies in dIgA format can be exploited for targeted therapy in ADPKD.

OFD1 and flotillins are integral components of a ciliary signaling protein complex organized by polycystins in renal epithelia and odontoblasts

Mutation of the X-linked oral-facial-digital syndrome type 1 (OFD1) gene is embryonic lethal in males and results in craniofacial malformations and adult onset polycystic kidney disease in females. While the OFD1 protein localizes to centriolar satellites, centrosomes and basal bodies, its cellular function and how it relates to cystic kidney disease is largely unknown. Here, we demonstrate that OFD1 is assembled into a protein complex that is localized to the primary cilium and contains the epidermal growth factor receptor (EGFR) and domain organizing flotillin proteins. This protein complex, which has similarity to a basolateral adhesion domain formed during cell polarization, also contains the polycystin proteins that when mutant cause autosomal dominant polycystic kidney disease (ADPKD). Importantly, in human ADPKD cells where mutant polycystin-1 fails to localize to cilia, there is a concomitant loss of localization of polycystin-2, OFD1, EGFR and flotillin-1 to cilia. Together, these data suggest that polycystins are necessary for assembly of a novel flotillin-containing ciliary signaling complex and provide a molecular rationale for the common renal pathologies caused by OFD1 and PKD mutations.

Regulation of STATs by polycystin-1 and their role in polycystic kidney disease

Autosomal-dominant polycystic kidney disease (ADPKD) is a common genetic disease caused by mutations in the gene coding for polycystin-1 (PC1). PC1 can regulate STAT transcription factors by a novel, dual mechanism. STAT3 and STAT6 are aberrantly activated in renal cysts. Genetic and pharmacological approaches to inhibit STAT3 or STAT6 have led to promising results in ADPKD mouse models. Here, we review current findings that lead to a model of PC1 as a key regulator of STAT signaling in renal tubule cells. We discuss how PC1 may orchestrate appropriate epithelial responses to renal injury, and how this system may lead to aberrant STAT activation in ADPKD thereby causing inappropriate activation of tissue repair programs that culminate in renal cyst growth and fibrosis.

STAT3 Signaling in Polycystic Kidney Disease

Mutations in the gene coding for the integral membrane protein polycystin-1 (PC1) are the cause of most cases of autosomal-dominant polycystic kidney disease (ADPKD), a very common disease that leads to kidney failure and currently lacks approved treatment. Recent work has revealed that PC1 can regulate the transcription factor STAT3, and that STAT3 is aberrantly activated in the kidneys of ADPKD patients and PKD mouse models. Recent approaches to directly inhibit STAT3 in PKD mouse models have been promising. Numerous signaling pathways are known to activate STAT3 and many have long been implicated in the pathogenesis of PKD - such as EGF/EGFR, HGF/c-Met, Src. However, a role of STAT3 in the pathogenesis of PKD had never been considered until now. Here, we review the current findings that suggest that STAT3 is a promising target for the treatment of PKD.

Polycystin-1 regulates STAT activity by a dual mechanism

Mutations in polycystin-1 (PC1) lead to autosomal-dominant polycystic kidney disease (ADPKD), a leading cause of renal failure for which no treatment is available. PC1 is an integral membrane protein, which has been implicated in the regulation of multiple signaling pathways including the JAK/STAT pathway. Here we show that membrane-anchored PC1 activates STAT3 in a JAK2-dependent manner, leading to tyrosine phosphorylation and transcriptional activity. The C-terminal cytoplasmic tail of PC1 can undergo proteolytic cleavage and nuclear translocation. Tail-cleavage abolishes the ability of PC1 to directly activate STAT3 but the cleaved PC1 tail now coactivates STAT3 in a mechanism requiring STAT phosphorylation by cytokines or growth factors. This leads to an exaggerated cytokine response. Hence, PC1 can regulate STAT activity by a dual mechanism. In ADPKD kidneys PC1 tail fragments are overexpressed, including a unique ∼15-kDa fragment (P15). STAT3 is strongly activated in cyst-lining epithelial cells in human ADPKD, and orthologous and nonorthologous polycystic mouse models. STAT3 is also activated in developing, postnatal kidneys but inactivated in adult kidneys. These results indicate that STAT3 signaling is regulated by PC1 and is a driving factor for renal epithelial proliferation during normal renal development and during cyst growth.

Failure to ubiquitinate c-Met leads to hyperactivation of mTOR signaling in a mouse model of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited disorder that is caused by mutations at two loci, polycystin 1 (PKD1) and polycystin 2 (PKD2). It is characterized by the formation of multiple cysts in the kidneys that can lead to chronic renal failure. Previous studies have suggested a role for hyperactivation of mammalian target of rapamycin (mTOR) in cystogenesis, but the etiology of mTOR hyperactivation has not been fully elucidated. In this report we have shown that mTOR is hyperactivated in Pkd1-null mouse cells due to failure of the HGF receptor c-Met to be properly ubiquitinated and subsequently degraded after stimulation by HGF. In Pkd1-null cells, Casitas B-lineage lymphoma (c-Cbl), an E3-ubiquitin ligase for c-Met, was sequestered in the Golgi apparatus with α₃β₁ integrin, resulting in the inability to ubiquitinate c-Met. Treatment of mouse Pkd1-null cystic kidneys in organ culture with a c-Met pharmacological inhibitor resulted in inhibition of mTOR activity and blocked cystogenesis in this mouse model of ADPKD. We therefore suggest that blockade of c-Met is a potential novel therapeutic approach to the treatment of ADPKD.

Scatter Factors in renal disease: Dr. Jeckyll and Mr. Hyde?

The Scatter Factors are two homologous proteins, named Scatter Factor/Hepatocyte Growth Factor and Macrophage Stimulating Protein. Their receptors are the products of two oncogenes, Met and Ron, respectively. The Scatter Factors induce movement, stimulate proliferation, regulate apoptosis and are morphogenic, i.e. operate an integrated program that seems tailored to drive organ development and to regenerate injured tissues. On the other hand, Scatter Factors may be responsible for pathologic tissue remodeling, infiltration of inflammatory cells, and tumor growth and diffusion. The review describes the involvement of Scatter Factors in renal disease, including acute renal failure, glomerulonephritis, chronic fibrosing nephropathies, dialysis, renal transplantation and renal tumors, and discusses the double-faced role of Scatter Factors, that play either a protective or a pathogenic role.

Pkd1 inactivation induced in adulthood produces focal cystic disease

Autosomal dominant polycystic kidney disease, the most common monogenetic disorder, is characterized by gradual replacement of normal renal parenchyma by fluid-filled cysts. Mutations in either PKD1 or PKD2 cause autosomal dominant polycystic kidney disease. Pkd1(-/-) or Pkd2(-/-) mice develop rapid renal cystic disease and exhibit embryonic lethality; this supports the "two-hit" hypothesis, which proposes that a germline mutation in PKD1 (or PKD2) followed by a second somatic mutation later in life is responsible for the phenotype. Here, for investigation of the loss of Pkd1 at specific times of development, an inducible Pkd1-knockout mouse model was generated. Inactivation of Pkd1 in 5-wk-old mice resulted in formation of only focal renal cysts 6 to 9 wk later but in a severe polycystic phenotype nearly 1 yr later. Cysts derived from either collecting tubules or distal tubules but not from proximal tubules, which correlated with sites of Cre-mediated recombination. Inactivation of Pkd1 in 1-wk-old mice, however, resulted in massive cyst disease 6 wk later, despite a similar pattern of Cre-mediated recombination between 1- and 5-wk-old kidneys. Moreover, a germline heterozygous Pkd1 mutation facilitated cyst formation when a somatic Pkd1 mutation was induced. A marked increase in proliferating cell nuclear antigen expression was observed in cyst-lining epithelia and in normal-looking tubules adjacent to but not in those distant from cysts. These data suggest that Pkd1 inactivation is not sufficient to initiate the cell proliferation necessary for cyst formation; a paracrine mechanism may account for focal cell proliferation and regional disease progression. We propose that an additional genetic or nongenetic "third hit" may be required for rapid development of cysts in polycystic kidney disease.

ADPKD: molecular characterization and quest for treatment

Autosomal-dominant polycystic kidney disease (ADPKD) is a common hereditary disease that features multiple cystogenesis in various organs and vascular defects. The genes responsible for ADPKD, PKD1, and PKD2 have been identified, and the pathological processes of the disease are becoming clearer. This review focuses on recent findings about the molecular and cellular biology of ADPKD, and especially on PKD1. PKD1 and its product, polycystin-1, play pivotal roles in cellular differentiation because they regulate the cell cycle and because polycystin-1 is a component of adherens junctions. A possible link between polycystin-1 and PPARgamma is discussed. The extraordinarily fast research progress in this area in the last decade has now reached a stage where the development of a remedy for ADPKD might become possible in the near future.

Expression of hepatocyte growth factor and its receptor C-met in acquired renal cystic disease associated with renal cell carcinoma

PURPOSE

The development of renal cell carcinoma (RCC) is a critical problem in acquired renal cystic disease (ARCD) in patients with end stage renal disease, particularly males on chronic hemodialysis. We examined the expression of hepatcyte growth factor (HGF) and its receptor c-met in ARCD associated with RCC to elucidate the role of the HGF/c-met pathway in renal cyst development and subsequent tumor transformation.

MATERIALS AND METHODS

Immunohistochemical expression of HGF, c-met and Bcl-2 was examined in 15 normal tissue samples of kidneys obtained from nephrectomy for localized RCC and 19 with ARCD associated with RCC from 16 patients on dialysis. The expression of HGF mRNA was examined by reverse transcriptase-polymerase chain reaction.

RESULTS

In normal kidneys immunostaining for HGF was scarcely detected in renal tubular cells. Bcl-2 and c-met immunostaining was observed mainly in distal tubular cells. In nontumor areas of kidneys with ARCD associated RCC the expression of HGF and c-met was up-regulated in tubular and the cyst epithelial cells. Hyperplastic cysts with multilayer epithelium and micropapillary projection were the predominant cysts stained with HGF and c-met. Immunostaining for HGF and c-met was also detected in RCC regions. The Bcl-2 immunostaining pattern was similar to that of HGF and c-met in nontumor and RCC regions. On reverse transcriptase-polymerase chain reaction HGF mRNA expression was up-regulated in nontumor areas and RCC regions in ARCD.

CONCLUSIONS

These results suggest that up-regulation of HGF and its receptor c-met may be involved in renal cyst formation and subsequent tumor transformation in patients with end stage renal disease. Increased Bcl-2 expression may promote this process through the inhibition of apoptosis.

Obstructive nephropathy and renal fibrosis: The role of bone morphogenic protein-7 and hepatocyte growth factor

BACKGROUND

The nephropathy induced by ureteral obstruction is associated with increased interstitial volume due to matrix deposition, fibroblast differentiation/proliferation, and monocyte infiltration. Recent studies indicate that transforming growth factor-beta (TGF-beta) is linked to renal fibrosis. Tumor necrosis factor (TNF-alpha) has a role in the recruitment of inflammatory cells. We found that infiltration of macrophages of the interstitium in unilateral ureteral obstruction (UUO) occurred as early as four hours after the onset of UUO.

METHODS

Recent studies indicate that a renal tubular development morphogen, bone morphogenetic protein-7 (BMP-7), is effective in preventing the tubulointerstitial nephritis in the setting of obstructive nephropathy. The mechanism of action appears to be preservation of epithelial cell phenotype, inhibition of epithelial-mesenchymal transdifferentiation, and inhibition of injury-induced epithelial cell apoptosis. Hepatocyte growth factor (HGF) also inhibited tubulointerstitial fibrosis.

RESULTS

In a treatment protocol in rats with ureteral ligation, BMP-7 restored renal function. The preservation of glomerular filtration rate (GFR) was accompanied by a significant decrease in cortical interstitial volume. In diabetic rats given BMP-7 proteinuria was normalized. In mice with ureteral obstruction, HGF suppressed the expression of TGF-beta and of platelet-derived growth factor. The onset of tubulointerstitial fibrosis was almost completely inhibited by HGF.

CONCLUSION

Both BMP-7 and HGF attenuate the tubulointerstitial fibrosis due to ureteral obstruction. They also increase GFR and renal plasma flow.

Hepatocyte growth factor: from diagnosis to clinical applications

Hepatocyte growth factor (HGF), initially identified and molecularly cloned as a potent mitogen of primary cultured hepatocytes, has multiple activities in a variety of tissues during the course of development and also in various disease states. HGF plays key roles in the attenuation of disease progression as an intrinsic repair factor. It is also evident that HGF levels are regulated under different conditions, for example, during the course of pregnancy, aging, and disease. This review focuses on the levels of HGF in normal and pathophysiological situations and examines the relationships between HGF levels and disease, disease stage, and disease prognosis. The clinical potential of HGF as a treatment for subjects with various diseases is also given attention.

Dysplastic and polycystic kidneys: diagnosis, associations and management

Cystic and bright kidneys can pose a significant diagnostic dilemma when discovered as an incidental finding at the time of a routine fetal ultrasound scan. There are diverse aetiologies with equally variable implications for the prognosis in the affected fetus, and for future pregnancies. Accurate antenatal diagnosis in the absence of any positive family history is often not possible and a team approach to management (to include the fetal medicine specialist, paediatric nephrologist or urologist, geneticists and in some cases, pathologist) is essential. In this review we will attempt to describe the embryology and aetiology of these conditions and suggest an approach to management.

Refinement of the gene locus for autosomal dominant medullary cystic kidney disease type 1 (MCKD1) and construction of a physical and partial transcriptional map of the region

Autosomal dominant medullary cystic kidney disease (MCKD) is an adult onset tubulointerstitial nephropathy that leads to salt wasting and end-stage renal failure. A gene locus (MCKD1) has been mapped on chromosome 1q21. Here we report on a large MCKD1 family of British origin linked to the MCKD1 locus. Haplotype analysis performed with markers spanning the previously reported critical MCKD1 region allowed for the refinement of this interval to 4 cM by definition of D1S305 as a new proximal flanking marker. Furthermore, we constructed a yeast artificial chromosome, P1-related artificial chromosome, and bacterial artificial chromosome contig of this region, which is only sparsely covered by the Human Genome Sequencing Project. This enabled us to map numerous expressed sequence tags within the critical interval. This physical and partial transcriptional map of the MCKD1 region is a powerful tool for the identification of positional and functional candidate genes for MCKD1 and will help to identify the disease-causing gene.

Dome formation and tubule morphogenesis by Xenopus kidney A6 cell cultures exposed to microgravity simulated with a 3D-clinostat and to hypergravity

Confluent high-density cell cultures of A6 cells derived from adult male Xenopus kidney exhibit spontaneous dome-formation at 1 g. To determine whether this morphogenetic property is altered by gravity, we used a three-dimensional (3D) clinostat to subject the cells to simulated microgravity, and a centrifuge to subject them to hypergravity. We used the generation orbit control method as the new rotation control system of the 3D-clinostat, not the random method. The growth of A6 cells was significantly enhanced by hypergravity, but significantly reduced by simulated microgravity. Dome formation by A6 cells at high confluence was inhibited under simulated microgravity conditions, whereas hypergravity promoted dome formation and induced tubule morphogenesis, compared to the control at 1 g. These results indicated that changes in gravity influence the morphogenetic properties of A6 cells, such as dome formation and tubule morphogenesis. When dome formation by A6 cells at high confluence was induced spontaneously in the control 1 g culture, the gene expression of the HGF family of pleiotropic factors, such as HGF-like protein (HLP) and growth factor-Livertine (GF-l.ivertine), an epithelial serine protease of channel activating protease 1 (CAP1), and Na+, K+-adenosine triphosphatase (ATPase), increased. Simulated microgravity increased the gene expression of activin A and reduced the gene expression of HLP, GF-Livertine, CAP1, and Na+, K+-ATPase. Hypergravity, on the other hand, decreased the gene expression of activin A and increased the gene expression of HLP, GF-Livertine, CAP1, and Na+, K+-ATPase. These results suggest that the effects of gravitational changes on expression of the HGF family member gene, CAP1, and Na+, K+-ATPase gene may be important for the cell growth, tubule morphogenesis, and dome formation of A6 cells in altered

The hepatocyte growth factor/Met pathway in development, tumorigenesis, and B-cell differentiation

This article summarizes the structure, signal transduction and physiologic functions of the HGF/Met pathway, as well as its role in tumor growth, invasion, and metastasis. Moreover, it highlights recent studies indicating a role for the HGF/Met pathway in antigen-specific B-cell development and B-cell neoplasia.

Hepatocyte growth factor in renal failure: promise and reality

Can science discover some secrets of Greek mythology? In the case of Prometheus, we can now suppose that his amazing hepatic regeneration was caused by a peptide growth factor called hepatocyte growth factor (HGF). Increasing evidence indicates that HGF acts as a multifunctional cytokine on different cell types. This review addresses the molecular mechanisms that are responsible for the pleiotropic effects of HGF. HGF binds with high affinity to its specific tyrosine kinase receptor c-met, thereby stimulating not only cell proliferation and differentiation, but also cell migration and tumorigenesis. The three fundamental principles of medicine-prevention, diagnosis, and therapy-may be benefited by the rational use of HGF. In renal tubular cells, HGF induces mitogenic and morphogenetic responses. In animal models of toxic or ischemic acute renal failure, HGF acts in a renotropic and nephroprotective manner. HGF expression is rapidly up-regulated in the remnant kidney of nephrectomized rats, inducing compensatory growth. In a mouse model of chronic renal disease, HGF inhibits the progression of tubulointerstitial fibrosis and kidney dysfunction. Increased HGF mRNA transcripts were detected in mesenchymal and tubular epithelial cells of rejecting kidney. In transplanted patients, elevated HGF levels may indicate renal rejection. When HGF is considered as a therapeutic agent in human medicine, for example, to stimulate kidney regeneration after acute injury, strategies need to be developed to stimulate cell regeneration and differentiation without an induction of tumorigenesis.

Serum hepatocyte growth factor levels in Henoch-Schönlein purpura

BACKGROUND

Henoch-Schönlein purpura (HSP) is the most common form of vasculitis in children. The potential role of hepatocyte growth factor (HGF) in acute immune-mediated vasculitis has not been elucidated.

METHODS

Serum HGF levels were determined in patients with HSP.

RESULTS

In patients with acute-phase HSP, mean (+/- SD) serum HGF levels were 0.32 +/- 0.14 ng/mL and were significantly higher than those in the control group (0.11 +/- 0.10 ng/mL). This elevation of serum HGF levels recovered to control levels in parallel with improvement of the clinical symptoms.

CONCLUSIONS

It is suggested that elevation of serum HGF levels in patients with acute-phase HSP may reflect endothelial cell damage or dysfunction in HSP.

Hepatocyte growth factor and the kidney: it is not just for the liver

Mesenchymal-epithelial interactions are important for many biological processes in epithelial organs such as the kidney. Hepatocyte growth factor (HGF) is a mesenchymally derived polypeptide cytokine that acts through its tyrosine kinase c-met receptor and is an important mediator of these interactions. This article reviews data showing the in vitro actions of HGF on renal epithelial cells that result in such diverse responses as mitogenesis, motogenesis, and morphogenesis. It also examines the in vivo evidence linking HGF and the c-met receptor to kidney development, regeneration following injury, and renal disease. Elucidating cellular mechanisms underlying the coordinated control of diverse HGF-induced phenotypic changes in renal epithelia in vitro should contribute to a clearer understanding of complex biological processes such as organogenesis, regeneration, and carcinogenesis in epithelial organs such as the kidney.

Retinal pigment epithelial cells secrete and respond to hepatocyte growth factor

Hepatocyte growth factor (HGF) is normally expressed by mesenchymal cells while its receptor, c-Met, is expressed in epithelial cells. Since HGF is critically involved in epithelial-mesenchyme interactions and the retinal pigment epithelium (RPE) is present at the interface between the retina and choroid, this study was initiated to determine whether the RPE expresses or responds to HGF in vitro. Cultured adult and fetal human RPE expressed mRNA for HGF and c-Met by RT-PCR. ELISA assay demonstrated the secretion of HGF into RPE culture supernatants. Tyrosine phosphorylation of c-Met was constitutively found in 72 hour RPE cultures and could be rapidly induced in serum-starved cells by concentrated RPE supernatants. HGF was mitogenic for cultured RPE (100 ng/ml.) and stimulated their chemotaxis (maximal response at 50 ng/ml). RPE are one of only a very limited number of epithelia that express both HGF and its receptor, suggesting the possibility of an autocrine action for this growth factor.

Co-expression of hepatocyte growth factor and its receptor in human prostate cancer

Hepatocyte growth factor acts differently depending on the organs or tumours involved. It may be produced simultaneously with its receptor, c-Met, in several types of malignant tumour cells and may exercise an autocrine regulation. To analyse the effect of hepatocyte growth factor in human prostate cancer, we conducted immunohistochemistry, in situ hybridization and the reverse transcriptase polymerase chain reaction. The first two techniques revealed the growth factor in prostate cancer cells, and the polymerase chain reaction confirmed this expression. c-Met is expressed in prostate cancer cells, but not in interstitial cells. Hepatocyte growth factor is expressed in interstitial cells, especially in hormone-treated cancer tissue, indicating that the growth factor pathway changes with the hormonal status. Low-grade tumours expressed c-Met at the plasma membrane. Higher grade tumours tended to express it in the cytoplasm, suggesting that the role of c-Met as the hepatocyte growth factor receptor was blocked in higher grade tumours. The relationship between the growth factor and its receptor is thus influenced by hormonal status and differentiation in prostate cancer and is not explained simply in terms of autocrine or paracrine action.

Hepatocyte growth factor and neutrophil elastase in idiopathic pulmonary fibrosis

It has been hypothesized that hepatocyte growth factor (HGF) may play an important role in regulating the growth of lung epithelium and in the regeneration of the lung as a paracrine or endocrine factor in idiopathic pulmonary fibrosis (IPF). Based on this background, serum HGF was measured in 31 IPF patients (21 male/10 female, median age 60 years). Fifteen age-matched normal non-smokers served as the control. Hepatocyte growth factor was measured by enzyme-linked immunosorbent assay with monoclonal and polyclonal antibodies against human HGF (Otsuka Assay Laboratories, Tokushima, Japan). Elastase: alpha 1-proteinase complex was also measured by enzyme-linked immunosorbent assay. No patients had significant liver or renal dysfunction. As a result, mean (standard error) serum HGF concentration of the patients with IPF was 0.384 (0.022) ng ml-1, which was significantly high compared to normal non-smokers [0.213 (0.012) ng ml-1, P < 0.001, 95% confidence interval was between 0.104 and 0.238]. Serum HGF values correlated strongly with the plasma elastase: alpha 1 proteinase inhibitor complex (R = 0.679, P < 0.001). Immunohistochemical staining of lung tissue with anti-human neutrophil elastase showed scattered immunopositive cells mainly in interstitium. Immunohistochemical staining with mouse anti-human HGF antibody showed that HGF was distributed to the lung epithelial cells in IPF lung specimens obtained by open lung biopsy. These results suggest that HGF may play an important role in the pathogenesis of IPF.

C-met proto-oncogene expression in benign and malignant human renal tissues

PURPOSE

Hepatocyte growth factor/scatter factor (HGF/SF) is a potent mitogen to renal epithelial cells in vitro and in vivo. HGF/SF signals through its receptor which is coded by the c-met proto-oncogene. We hypothesized that altered expression of the HGF/SF receptor, c-met, may be involved in the pathogenesis of certain renal cell carcinomas. Our objectives were to 1) assess the presence and localization of c-met protein in benign and malignant human renal tissues, and 2) correlate the presence of c-met protein with renal carcinoma histological subtype, tumor stage and tumor grade.

MATERIALS AND METHODS

Immunohistochemical analysis of c-met protein was performed in 41 normal and malignant human renal samples.

RESULTS

c-met Immunostaining was detected in the normal kidney tissue in all 41 samples. In the normal kidney c-met immunostaining was limited to the cell membrane and/or cytoplasm of epithelial cells in specific tubular segments, including the proximal convoluted tubule, thin and thick limbs of the loop of Henle, and the collecting duct. The glomeruli, distal convoluted tubule and stroma were consistently negative for c-met staining. c-met Immunostaining was detected in 68% of renal cell carcinomas and was more common in higher nuclear grade cancers (p < 0.034).

CONCLUSIONS

The c-met receptor is present in specific tubular segments in the normal kidney and is frequently expressed in higher nuclear grade renal cancers, suggesting a role in renal carcinoma progression. Future studies should evaluate the biological significance of the HGF/ SF-c-met pathway in normal renal physiology, and renal cancer growth and progression.

Modulation of motility and proliferation of glioma cells by hepatocyte growth factor

Invasive proliferation is a critical biological characteristic of gliomas. We evaluated the activities of hepatocyte growth factor (HGF) on proliferation and motility of glioma cells, comparing them with the effects of other growth factors (EGF, bFGF, PDGF-BB, TGF-beta 1). Seven primary culture lines all expressed c-met and HGF mRNA, and secreted HGF. HGF stimulated 3H-thymidine uptake of every glioma cell line (30 to 70% upregulation). Boyden chamber assay and scattering assay revealed that HGF promoted cell motility with chemokinetic and strong chemotactic activities. Concentric circle assay showed that HGF promoted two-dimensional expansion (proliferation and motility) most strongly among the growth factors studied. Further, we analyzed 23 paraffin-embedded sections of surgically resected gliomas (7 grade II, 8 grade III, and 8 grade IV) by immunohistochemistry. Expression of HGF and Met increased with malignant progression of gliomas, suggesting that gliomas stimulated their invasive proliferation by autocrine HGF production. Neurons and vasculature were HGF-positive, and Met-positive glioma cells gathered around them. The data indicate that neurons and vasculature, which are the main tracks of glioma invasion, augment chemotactic invasion and proliferation of gliomas by paracrine HGF secretion. Clearly HGF plays a critical role in invasive proliferation of glioma cells and it is therefore a candidate target of therapeutic intervention.

Expression of hepatocyte growth factor/scatter factor and its receptor, MET, suggests roles in human embryonic organogenesis

Hepatocyte growth factor/scatter factor (HGF/SF) is secreted by mesenchymal cells and elicits proliferation, motility, differentiation, and morphogenesis of epithelia and other cells. These effects are mediated by binding to MET, a receptor tyrosine kinase. Genetically engineered mice lacking HGF/SF die in utero due to a failure of placental and hepatocyte differentiation, but little information exists regarding the expression of this signaling system in human development. Using reverse transcriptase-polymerase chain reaction, Western blots, and immunohistochemistry, we report that HGF/SF and MET are expressed during critical early periods of human organogenesis from 6 to 13 wk of gestation. Organs that expressed both genes included liver, metanephric kidney, intestine, and lung, each of which develop by inductive interactions between mesenchyme and epithelia. Of all organs studied, the placenta contained the highest levels of HGF/SF protein, and MET was detected in trophoblastic cells of chorionic villi as early as the 5th wk of gestation. Finally, examination of a human multicystic dysplastic kidney demonstrated that malformed, hyperproliferative tubules expressed MET, whereas HGF/SF protein was immunolocalized to the same epithelia and also to the surrounding undifferentiated cells. Hence HGF/SF might be an important growth factor in normal human embryogenesis and may additionally play a role in human organ malformations.

Immunodetection of c-met-oncogene's protein product in renal cell neoplasia

The proto-oncogene c-met encodes a transmembrane tyrosine kinase receptor for hepatocyte growth factor and is expressed in normal kidney tissue. This receptor may be involved in the carcinogenesis of various organs. The aim of this study was to investigate the relationship between c-met immunohistochemical expression and pathological tumor variables in human renal cell carcinomas (RCCs) and adenomas (RAs). Formalin fixed, paraffin embedded tissues from 35 RCCs, 16 RAs and 17 normal kidneys were immunostained (Strept. ABC/HRP) with a polyclonal antibody against c-met protein (Santa Cruz, Clone C-12). The statistical analysis was performed using the linear trend in proportions and Fisher's exact test. C-met protein was detected in the cytoplasm and the plasma membranes of neoplastic cells in 19/35 RCCs (54%), 10/16 adenomas (63%) (p = 0.41) and in 17/17 controls in the epithelial cells of distal renal tubules and collecting ducts. C-met protein expression was not related with gender (p = 0.45), age (p = 0.18), tumor size (p = 0.99), cell type (p = 0.26), grade (p = 0.86) and stage (p = 0.33). Moreover, c-met immunopositive tumor cell percentage and intensity were increased in stage [RCCs, but these results were not statistically significant. Apart from glandular differentiation, c-met protein expression was not related to other histopathological features (i.e. to the type of cells or to any selective overexpression in tumor cells). C-met product may be involved in the malignant transformation of tubular epithelial cells as an early event in RCC carcinogenesis. C-met expression does not seem to have any prognostic significance for RCCs, as it was not associated with any pathological prognosticator.

Deregulation of cell survival in cystic and dysplastic renal development

Various aberrations of cell biology have been reported in polycystic kidney diseases and in cystic renal dysplasias. A common theme in these disorders is failure of maturation of renal cells which superficially resemble embryonic tissue. Apoptosis is a feature of normal murine nephrogenesis, where it has been implicated in morphogenesis, and fulminant apoptosis occurs in the small, cystic kidneys which develop in mice with null mutations of bcl-2. Therefore, we examined the location and extent of apoptosis in pre- and postnatal samples of human polycystic and dysplastic kidney diseases using propidium iodide staining, in situ end-labeling and electron microscopy. In dysplastic kidneys cell death was prominent in undifferentiated cells around dysplastic tubules and was occasionally found in cystic epithelia. The incidence of apoptosis was significantly greater than in normal controls of comparable age both pre- and postnatally. In the polycystic kidneys there was widespread apoptosis in the interstitium around undilated tubules distant from cysts, in undilated tubules between cysts and in cystic epithelia. The level of apoptosis compared to controls was significantly increased postnatally. A similar increase of cell death was also noted in the early and late stages of renal disease in the polycystic cpk/cpk mouse model. We speculate that deregulation of cell survival in these kidneys may reflect incomplete tissue maturation, and may contribute to the progressive destruction of functional kidney tissue in polycystic kidneys and the spontaneous involution reported in cystic dysplastic kidneys.