Digital spatial profiling of collapsing glomerulopathy.

Collapsing glomerulopathy is a histologically distinct variant of focal and segmental glomerulosclerosis that presents with heavy proteinuria and portends a poor prognosis. Collapsing glomerulopathy can be triggered by viral infections such as HIV or SARS-CoV-2. Transcriptional profiling of collapsing glomerulopathy lesions is difficult since only a few glomeruli may exhibit this histology within a kidney biopsy and the mechanisms driving this heterogeneity are unknown. Therefore, we used recently developed digital spatial profiling (DSP) technology which permits quantification of mRNA at the level of individual glomeruli. Using DSP, we profiled 1,852 transcripts in glomeruli isolated from formalin fixed paraffin embedded sections from HIV or SARS-CoV-2-infected patients with biopsy-confirmed collapsing glomerulopathy and used normal biopsy sections as controls. Even though glomeruli with collapsing features appeared histologically similar across both groups of patients by light microscopy, the increased resolution of DSP uncovered intra- and inter-patient heterogeneity in glomerular transcriptional profiles that were missed in early laser capture microdissection studies of pooled glomeruli. Focused validation using immunohistochemistry and RNA in situ hybridization showed good concordance with DSP results. Thus, DSP represents a powerful method to dissect transcriptional programs of pathologically discernible kidney lesions.

Extraglomerular immune complex deposition in lupus nephritis.

BACKGROUND: Lupus nephritis (LN) is a common manifestation and a major cause of morbidity and mortality in systemic lupus erythematosus (SLE) patients. It is characterized by glomerular and often extraglomerular immune complex deposition. PURPOSE: Given the emerging importance of the tubulointerstitial compartment, we conducted a retrospective study of 78 LN biopsies to enumerate the spectrum of extraglomerular immune complex deposition that can be observed in lupus nephritis by electron microscopy and to identify possible clinical or pathologic correlates. RESULTS: The presence of tubulointerstitial immune complex deposition often accompanied interstitial inflammation, but some discrepancies were also seen. CONCLUSIONS: As target antigens are identified, correlation with glomerular, tubulointerstitial, and vascular immune complex deposition will be of increasing interest.

Multicenter Clinicopathologic Correlation of Kidney Biopsies Performed in COVID-19 Patients Presenting With Acute Kidney Injury or Proteinuria.

RATIONALE & OBJECTIVE: Kidney biopsy data inform us about pathologic processes associated with infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We conducted a multicenter evaluation of kidney biopsy findings in living patients to identify various kidney disease pathology findings in patients with coronavirus disease 2019 (COVID-19) and their association with SARS-CoV-2 infection. STUDY DESIGN: Case series. SETTING & PARTICIPANTS: We identified 14 native and 3 transplant kidney biopsies performed for cause in patients with documented recent or concurrent SARS-CoV-2 infection treated at 7 large hospital systems in the United States. OBSERVATIONS: Men and women were equally represented in this case series, with a higher proportion of Black (n=8) and Hispanic (n=5) patients. All 17 patients had SARS-CoV-2 infection confirmed by reverse transcriptase-polymerase chain reaction, but only 3 presented with severe COVID-19 symptoms. Acute kidney injury (n=15) and proteinuria (n=11) were the most common indications for biopsy and these symptoms developed concurrently or within 1 week of COVID-19 symptoms in all patients. Acute tubular injury (n=14), collapsing glomerulopathy (n=7), and endothelial injury/thrombotic microangiopathy (n=6) were the most common histologic findings. 2 of the 3 transplant recipients developed active antibody-mediated rejection weeks after COVID-19. 8 patients required dialysis, but others improved with conservative management. LIMITATIONS: Small study size and short clinical follow-up. CONCLUSIONS: Cases of even symptomatically mild COVID-19 were accompanied by acute kidney injury and/or heavy proteinuria that prompted a diagnostic kidney biopsy. Although acute tubular injury was seen among most of them, uncommon pathology such as collapsing glomerulopathy and acute endothelial injury were detected, and most of these patients progressed to irreversible kidney injury and dialysis.

Discordance between immunofluorescence and immunohistochemistry C4d staining and outcomes following heart transplantation.

BACKGROUND: Capillary deposition of C4d is an important marker of antibody-mediated rejection (AMR) following heart transplantation (HT). There are two immunopathologic assay methods for detecting C4d: frozen-tissue immunofluorescence (IF) and paraffin immunohistochemistry (IHC). The clinical significance of discrepancy between the results of IF and IHC has not been understood. METHODS AND RESULTS: We reviewed 2187 biopsies from 142 HT recipients who had biopsies with assessment of both IF and IHC staining. Among them, 103 (73%) patients had negative IF and IHC C4d staining (Negative Group) and 32 (23%) patients had positive IF but negative IHC staining (Discordant Group). At the time of positive biopsy, 6 (19%) Discordant patients had graft dysfunction, compared to 5 (5%) Negative patients (p = .022). Cumulative incidence of cellular rejection at 1 year was comparable (31% vs. 29%, p = .46); however, cumulative incidence of AMR was significantly higher in the Discordant group (21% vs. 4%, p = .004). Overall 1-year survival was comparable (90% vs. 96%, p = .24); however, freedom from heart failure (HF) was significantly lower in the Discordant group (70% vs. 96%, p < .001). CONCLUSION: The Discordant group showed higher rates of graft dysfunction, AMR and HF admission than the Negative group.

Phasor approach to autofluorescence lifetime imaging FLIM can be a quantitative biomarker of chronic renal parenchymal injury.

Diabetic kidney disease continues to be the leading cause of chronic kidney disease, often advancing to end stage kidney disease. In addition to the well characterized glomerular alterations including mesangial expansion, podocyte injury, and glomerulosclerosis, tubulointerstitial fibrosis is also an important component of diabetic kidney injury. Similarly, tubulointerstitial fibrosis is a critical component of any chronic kidney injury. Therefore, sensitive and quantitative identification of tubulointerstitial fibrosis is critical for the assessment of long-term prognosis of kidney disease. Here, we employed phasor approach to fluorescence lifetime imaging, commonly known as FLIM, to understand tissue heterogeneity and calculate changes in the tissue autofluorescence lifetime signatures due to diabetic kidney disease. FLIM imaging was performed on cryostat sections of snap-frozen biopsy material of patients with diabetic nephropathy. There was an overall increase in phase lifetime (τphase) with increased disease severity. Multicomponent phasor analysis shows the distinctive differences between the different disease states. Thus, phasor autofluorescence lifetime imaging, which does not involve any staining, can be used to understand and evaluate the severity of kidney disease.

Mutation of complement factor B causing massive fluid-phase dysregulation of the alternative complement pathway can result in atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome is an ultra-rare disease characterized by microangiopathic hemolytic anemia, thrombocytopenia and acute kidney injury. Its pathogenesis is driven most frequently by dysregulated cell-surface control of the alternative pathway of complement secondary to inherited and/or acquired factors. Here we evaluated two unrelated patients with atypical hemolytic uremic syndrome. The first, a five-year-old Caucasian female, presented at 10 months with schistocytes, thrombocytopenia and kidney injury. The second, a 55-year-old Caucasian female, presented at age 31 following caesarean section for preeclampsia. Complement biomarker testing was remarkable for undetectable levels of C3 in both. Circulating levels of C5 and properdin were also low consistent with over-activity of the alternative and terminal pathways of complement. Genetic testing identified a heterozygous novel variant in CFB (c.1101 C>A, p.Ser367Arg) in both patients. Functional studies found strong fluid-phase C3 cleavage when normal and proband sera were mixed. Cell-surface C3b deposition was strongly positive when patient serum was supplemented with C3. In vitro control of C3 convertase activity could be restored with increased concentrations of factor H. Thus, CFB p.Ser367Arg is a gain-of-function pathogenic variant that leads to dysregulation of the alternative pathway in the fluid-phase and increased C3b deposition on cell surfaces. Our study highlights the complexities of complement-mediated diseases like atypical hemolytic uremic syndrome and illustrates the importance of functional studies at the variant level to gain insight into the disease phenotype.

Renal Vasculitis and Pauci-immune Glomerulonephritis Associated With Immune Checkpoint Inhibitors.

Immune checkpoint inhibitors are increasingly used to treat a variety of solid-organ and hematologic cancers. However, overactivation of the immune system can lead to immune-related adverse events, which are increasingly recognized in the kidney. There have been only rare reported cases of checkpoint inhibitor-associated glomerulonephritis and renal vasculitis, although vasculitis in other organs has been well described. We report 4 cases of renal vasculitis or pauci-immune glomerulonephritis after checkpoint inhibitor therapy. Three patients had renal small- to medium-vessel vasculitis and 1 had focally crescentic pauci-immune glomerulonephritis. Three patients presented with acute kidney injury, and 1 presented with nephrotic syndrome and hematuria. Three patients were tested for antineutrophil cytoplasmic antibodies, which were negative. The time from checkpoint inhibitor initiation to immune-related adverse event presentation ranged from 2 weeks to 24 months. Three patients were treated with glucocorticoids, resulting in clinical resolution. Our series demonstrates that renal vasculitis and pauci-immune glomerulonephritis are important considerations in the differential diagnosis of checkpoint inhibitor-related reductions in kidney function.

FXR/TGR5 Dual Agonist Prevents Progression of Nephropathy in Diabetes and Obesity.

Bile acids are ligands for the nuclear hormone receptor farnesoid X receptor (FXR) and the G protein-coupled receptor TGR5. We have shown that FXR and TGR5 have renoprotective roles in diabetes- and obesity-related kidney disease. Here, we determined whether these effects are mediated through differential or synergistic signaling pathways. We administered the FXR/TGR5 dual agonist INT-767 to DBA/2J mice with streptozotocin-induced diabetes, db/db mice with type 2 diabetes, and C57BL/6J mice with high-fat diet-induced obesity. We also examined the individual effects of the selective FXR agonist obeticholic acid (OCA) and the TGR5 agonist INT-777 in diabetic mice. The FXR agonist OCA and the TGR5 agonist INT-777 modulated distinct renal signaling pathways involved in the pathogenesis and treatment of diabetic nephropathy. Treatment of diabetic DBA/2J and db/db mice with the dual FXR/TGR5 agonist INT-767 improved proteinuria and prevented podocyte injury, mesangial expansion, and tubulointerstitial fibrosis. INT-767 exerted coordinated effects on multiple pathways, including stimulation of a signaling cascade involving AMP-activated protein kinase, sirtuin 1, PGC-1α, sirtuin 3, estrogen-related receptor-α, and Nrf-1; inhibition of endoplasmic reticulum stress; and inhibition of enhanced renal fatty acid and cholesterol metabolism. Additionally, in mice with diet-induced obesity, INT-767 prevented mitochondrial dysfunction and oxidative stress determined by fluorescence lifetime imaging of NADH and kidney fibrosis determined by second harmonic imaging microscopy. These results identify the renal signaling pathways regulated by FXR and TGR5, which may be promising targets for the treatment of nephropathy in diabetes and obesity.

Medical renal diseases are frequent but often unrecognized in adult autopsies.

Kidney diseases affect many hospitalized patients and contribute to morbidity and mortality. Therefore, kidney disease should be prevalent, but the frequency and spectrum of medical renal pathology in autopsy specimens has not been well documented. We sought to determine the spectrum of medical renal pathology in adult autopsy specimens and the frequency of overlooked diagnoses. We reviewed the hematoxylin- and eosin-stained kidney sections from 140 adult autopsies performed at a large teaching hospital over a 2-year period. Fifty-eight cases (41%) had findings warranting further analysis, including alterations in glomerular matrix and/or cellularity, atypical or pigmented casts, thrombi, tubulointerstitial or vascular inflammation, or deposition of amorphous material. After additional studies and clinical correlation, the pathologic changes in 43 cases (31%) were categorized as follows: diabetic nephropathy, bile cast nephropathy, thrombotic microangiopathy, infection-related glomerulonephritis, focal necrotizing/crescentic glomerulonephritis, oxalate nephropathy, light-chain cast nephropathy, amyloidosis, urate nephropathy, hemosiderosis, antineutrophil cytoplasmic antibody-associated vasculitis, polyoma virus nephropathy, atheroembolic disease, and nephrocalcinosis. These diagnoses were not reported in 26 (60%) cases during the initial autopsy evaluation. This study demonstrates that medical renal diseases are common in autopsy cases, but significant diagnoses can be easily overlooked. Autopsy kidney specimens are a rich source of renal pathology and their evaluation should be emphasized in anatomic pathology residency training. Ultimately, our understanding of how kidney disease contributes to morbidity and mortality will benefit from accurate recognition of renal pathology in autopsy specimens.

Successful use of rituximab in glomerular basement membrane nephritis associated with HIV interstitial nephritis secondary to Castleman disease
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We report a case of glomerular basement membrane crescentic glomerulonephritis and multicentric Castleman disease-associated interstitial nephritis in a patient with human immunodeficiency virus (HIV) infection. The patient received corticosteroids, cyclophosphamide, and plasmapheresis, and within 3 weeks, there was worsening thrombocytopenia, anemia, and renal function requiring initiation of hemodialysis. He then received 8 weekly doses of rituximab, and there was steady improvement in renal function, such that he stopped dialysis within 6 weeks and has remained in disease remission at 1-year follow-up. This is the first case report of acute kidney injury caused by both antiglomerular basement membrane disease and multicentric Castleman disease, with a favorable response to rituximab.
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Medullary Microvascular Thrombosis and Injury in Sickle Hemoglobin C Disease.

Sickle cell nephropathy is a common complication in patients with sickle cell hemoglobinopathies. In these disorders, polymerization of mutated hemoglobin S results in deformation of red blood cells, which can cause endothelial cell injury in the kidney that may lead to thrombus formation when severe or manifest by multilayering of the basement membranes (glomerular and/or peritubular capillaries) in milder forms of injury. As the injury progresses, the subsequent ischemia, tubular dysfunction, and glomerular scarring can result in CKD or ESRD. Sickle cell nephropathy can occur in patients with homozygous hemoglobin SS or heterozygous hemoglobin S (hemoglobin SC, hemoglobin S/ß(0)-thalassemia, and hemoglobin S/ß(+)-thalassemia). Clinical manifestations resulting from hemoglobin S polymerization are often milder in patients with heterozygous hemoglobin S. These patients may not present with clinically apparent acute sickle cell crises, but these milder forms can provide a unique view of the kidney injury in sickle cell disease. Here, we report a patient with hemoglobin SC disease who showed peritubular capillary and vasa recta thrombi and capillary basement membrane alterations primarily involving the renal medulla. This patient highlights the vascular occlusion and endothelial cell injury in the medulla that contribute to sickle cell nephropathy.

Human polyomavirus receptor distribution in brain parenchyma contrasts with receptor distribution in kidney and choroid plexus.

The human polyomavirus, JCPyV, is the causative agent of progressive multifocal leukoencephalopathy, a rare demyelinating disease that occurs in the setting of prolonged immunosuppression. After initial asymptomatic infection, the virus establishes lifelong persistence in the kidney and possibly other extraneural sites. In rare instances, the virus traffics to the central nervous system, where oligodendrocytes, astrocytes, and glial precursors are susceptible to lytic infection, resulting in progressive multifocal leukoencephalopathy. The mechanisms by which the virus traffics to the central nervous system from peripheral sites remain unknown. Lactoseries tetrasaccharide c (LSTc), a pentasaccharide containing a terminal α2,6-linked sialic acid, is the major attachment receptor for polyomavirus. In addition to LSTc, type 2 serotonin receptors are required for facilitating virus entry into susceptible cells. We studied the distribution of virus receptors in kidney and brain using lectins, antibodies, and labeled virus. The distribution of LSTc, serotonin receptors, and virus binding sites overlapped in kidney and in the choroid plexus. In brain parenchyma, serotonin receptors were expressed on oligodendrocytes and astrocytes, but these cells were negative for LSTc and did not bind virus. LSTc was instead found on microglia and vascular endothelium, to which virus bound abundantly. Receptor distribution was not changed in the brains of patients with progressive multifocal leukoencephalopathy. Virus infection of oligodendrocytes and astrocytes during disease progression is LSTc independent.

Intratubular hemoglobin casts in hemolysis-associated acute kidney injury.

Kidney injury is a complication of intravascular hemolysis associated with many forms of hemolytic disease. Reports of kidney biopsy findings in patients with hemolysis-related kidney injury have focused primarily on the accumulation of hemosiderin pigment within proximal tubular epithelial cells (hemosiderosis), a feature of chronic hemolysis. The nephrotoxic effects of hemoglobin include direct cytotoxicity to tubular cells, but hemoglobin also can precipitate in distal nephron segments, forming obstructive casts. We present a case of hemolysis-associated tubular injury, characterized by acute onset of intravascular hemolysis followed by acute kidney injury with acute tubular injury and abundant intratubular casts containing hemoglobin.

Pauci-immune glomerulonephritis in children: a clinicopathologic study of 21 patients.

BACKGROUND: Pauci-immune glomerulonephritis (GN) represents a severe form of glomerular injury and is the most common cause of crescentic GN in adults. To date, the clinicopathologic features of pauci-immune GN are not well characterized in the pediatric population. METHODS: Twenty-six biopsies from 21 pediatric patients with pauci-immune GN were identified retrospectively from the pathology archives of the University of Chicago (biopsy incidence 5 % among pediatric patients). RESULTS: There was distinct female predominance (2.5:1) among the patient cohort. Serologic studies identified anti-neutrophil cytoplasmic antibodies (ANCA) in 85 % of patients, and 80 % had systemic manifestations of vasculitis. The median estimated glomerular filtration rate (eGFR) at presentation was 43 ml/min/1.73 m(2). Based on a previously proposed classification of ANCA-associated GN, we identified a spectrum of injury, including crescentic (n = 9), focal (n = 7), mixed (n = 5) and sclerotic GN (n = 5). Necrotizing arteritis was identified in a minority of patients (n = 3). The majority of those patients for whom data were available had been treated with cyclophosphamide and corticosteroids, with or without rituximab. Of the 21 pediatric patients, 58 % had developed chronic kidney disease at follow-up (eGFR <90 ml/min/1.73 m(2)), of whom 85 % of those had crescentic, mixed or sclerotic GN. CONCLUSION: Pediatric patients with pauci-immune GN are similar to their adult counterparts in terms of clinical manifestations and histopathologic findings. Among the 21 patients in our study, those with focal GN had the best outcomes while patients with crescentic, mixed or sclerotic GN overwhelmingly had a poor long-term outcome for kidney function.

An International Survey of Genitourinary and Renal Pathologists Regarding Evaluation of the Non-Neoplastic Parenchyma in Kidney Cancer Specimens.

Increasing survivorship in kidney cancer patients has shifted treatment strategies to optimize renal function preservation. In 2010, the College of American Pathologists (CAP) updated their synoptic reporting guidelines for tumor nephrectomies to require evaluation of the nonneoplastic kidney parenchyma. We conducted this study to understand current practice behaviors regarding the evaluation of the nonneoplastic kidney parenchyma in tumor nephrectomy specimens. We emailed a 14-item multiple-choice survey to members of the Renal Pathology Society and Genitourinary Pathology Society. We also emailed a 12-item survey to program and associate program directors of American pathology residencies to assess the current state of renal pathology education. Ninety-eight genitourinary and 104 renal pathologists responded to the survey on the nonneoplastic kidney parenchyma. Ninety-five percent of respondents who examine tumor nephrectomies reported evaluating the nonneoplastic kidney parenchyma. Seventy-five percent of genitourinary pathologists and 67% of renal pathologists use synoptic reporting, and 81% use the CAP protocol. Thirty-nine percent of respondents report always contacting the clinician when they find evidence of medical renal disease. Forty-two program leaders responded to our renal pathology education survey, and 64% of them have a mandatory renal pathology rotation that on average lasts about 2 to 4 weeks. The majority of pathologists examine the nonneoplastic kidney parenchyma of tumor nephrectomies and frequently report incidences of new medical renal disease directly to clinicians, but there remains room for improvement and educational gaps during residency training. Further efforts to standardize both this evaluation and renal pathology education will improve patient care.

The Detrimental Impact of End-Stage Kidney Disease Is Not Reflected in Autopsy Reports.

CONTEXT.­: End-stage kidney disease (ESKD) is defined as renal impairment requiring renal replacement therapy to sustain life. With a 1-year mortality of ∼20% to 30%, many die of complications related to this disease. OBJECTIVE.­: To determine the percentage of autopsy cases of decedents with ESKD in which the contribution of ESKD to death is accurately reflected in the final report. DESIGN.­: Autopsy case records were retrospectively reviewed at 4 institutions (Yale New Haven Hospital, University of Chicago Medical Center, University of Illinois at Chicago Hospital, University of Iowa Hospital). Clinical, macroscopic, and microscopic autopsy findings were reviewed, with attention to renal disease findings. RESULTS.­: One hundred sixty decedents with documented ESKD and premortem dialysis who underwent autopsy assessment were identified. ESKD was implicated as a cause of death (CoD) or significant contributing factor in 44 cases (28%), but not in the remaining 116 cases (72%). Cardiovascular disease was the most common CoD in ESKD. There was significant interpathologist variation in the inclusion of ESKD as a CoD across institutions. These rates ranged from 85% correlation (23 of 27 cases), to 13% (4 of 31 and 8 of 62 cases at 2 institutions), and 22.5% (9 of 40 cases) across the 4 participating institutions. CONCLUSIONS.­: The recognition at autopsy of ESKD as a CoD or contributing CoD at autopsy in patients undergoing dialysis remains low (28%). The detrimental impact of ESKD is not reflected in hospital autopsy reports, which carries implications for collection of vital statistics and allocation of research funding for kidney diseases.

AA amyloidosis With Ig-Dominant Staining and Diagnostically Unusual Features.

Introduction: Although serum amyloid A (AA) amyloid may occasionally show nonspecific staining by immunofluorescence (IF), the correct diagnosis can usually be determined by integrating pathologic features and clinical scenario, and using AA amyloid immunohistochemistry (IHC) and/or mass spectrometry. A recent mass spectrometry-based study described false-positive Ig IF staining in a subset of AA amyloid cases. Methods: We sought to delineate clinicopathologic features of AA amyloid with Ig-dominant staining by using a retrospective review. Results: AA amyloid with Ig-dominant staining was identified in 10 patients from 5 institutions, representing 1.2% to 4% of AA amyloid kidney biopsies. Evidence of a monoclonal protein was documented in 0% to 2.7% of patients with AA amyloid screened for inclusion, but 30% of those with Ig-dominant staining. The patient population had equal sex distribution and presented at median age of 68.5 years with nephrotic proteinuria and kidney impairment. Etiologies of AA amyloid included injection drug use (30%), autoimmune disease (20%), and chronic infection (10%); 40% had no identified clinical association. On biopsy, heavy chain (co)dominant staining by IF (in 80%), discordant distribution in Ig staining (in 20%), tubulointerstitial nephritis (in 30%), and/or crescents (in 10%) were present. Two of 3 patients with paraproteinemia had concordant heavy and/or light chain dominant staining within the AA amyloid. Two cases were initially misdiagnosed as Ig-associated amyloidosis. Conclusion: We describe the morphologic spectrum of AA amyloidosis with Ig-dominant staining which may have clinical, laboratory, and pathologic overlap with amyloid light chain (AL), amyloid heavy chain, and heavy and light chain (AHL) amyloidosis.

Quantifying Protein Acetylation in Diabetic Nephropathy from Formalin-Fixed Paraffin-Embedded Tissue.

PURPOSE: Diabetic kidney disease (DKD) is a serious complication of diabetes mellitus and a leading cause of chronic kidney disease and end-stage renal disease. One potential mechanism underlying cellular dysfunction contributing to kidney disease is aberrant protein post-translational modifications. Lysine acetylation is associated with cellular metabolic flux and is thought to be altered in patients with diabetes and dysfunctional renal metabolism. EXPERIMENTAL DESIGN: A novel extraction and LC-MS/MS approach was adapted to quantify sites of lysine acetylation from formalin-fixed paraffin-embedded (FFPE) kidney tissue and from patients with DKD and non-diabetic donors (n = 5 and n = 7, respectively). RESULTS: Analysis of FFPE tissues identified 840 total proteins, with 225 of those significantly changing in patients with DKD. Acetylomic analysis quantified 289 acetylated peptides, with 69 of those significantly changing. Pathways impacted in DKD patients revealed numerous metabolic pathways, specifically mitochondrial function, oxidative phosphorylation, and sirtuin signaling. Differential protein acetylation in DKD patients impacted sirtuin signaling, valine, leucine, and isoleucine degradation, lactate metabolism, oxidative phosphorylation, and ketogenesis. CONCLUSIONS AND CLINICAL RELEVANCE: A quantitative acetylomics platform was developed for protein biomarker discovery in formalin-fixed and paraffin-embedded biopsies of kidney transplant patients suffering from DKD.

Expression profiling of 519 kinase genes in matched malignant peripheral nerve sheath tumor/plexiform neurofibroma samples is discriminatory and identifies mitotic regulators BUB1B, PBK and NEK2 as overexpressed with transformation.

About 50% of all malignant peripheral nerve sheath tumors (MPNSTs) arise as neurofibromatosis type 1 associated lesions. In those patients malignant peripheral nerve sheath tumors are thought to arise through malignant transformation of a preexisting plexiform neurofibroma. The molecular changes associated with this transformation are still poorly understood. We sought to test the hypothesis that dysregulation of expression of kinases contributes to this malignant transformation. We analyzed expression of all 519 kinase genes in the human genome using the nanostring nCounter system. Twelve cases of malignant peripheral nerve sheath tumor arising in a background of preexisting plexiform neurofibroma were included. Both components were separately sampled. Statistical analysis compared global changes in expression levels as well as changes observed in the pairwise comparison of samples taken from the same surgical specimen. Immunohistochemical studies were performed on tissue array slides to confirm expression of selected proteins. The expression pattern of kinase genes can separate malignant peripheral nerve sheath tumors and preexisting plexiform neurofibromas. The majority of kinase genes is downregulated rather than overexpressed with malignant transformation. The patterns of expression changes are complex without simple recurring alteration. Pathway analysis demonstrates that differentially expressed kinases are enriched for kinases involved in the direct regulation of mitosis, and several of these show increased expression in malignant peripheral nerve sheath tumors. Immunohistochemical studies for the mitotic regulators BUB1B, PBK and NEK2 confirm higher expression levels at the protein level. These results suggest that the malignant transformation of plexiform neurofibroma is associated with distinct changes in the expression of kinase genes. The patterns of these changes are complex and heterogeneous. There is no single unifying alteration. Kinases involved in mitotic regulation are particularly enriched in the pool of differentially expressed kinases. Some of these are overexpressed and are therefore possible targets for kinase inhibitors.