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Objectives: To evaluate SATB2 expression and prognostic implications in a large cohort of thoracic neuroendocrine tumors.Methods: Surgical pathology files (1995-2017) and an institutional thymic epithelial tumor database (2010-2020) were searched for resected neuroendocrine tumors. Cases were stained with SATB2 (clone EP281). Percent SATB2-positive tumor cells and expression intensity were scored.Results: In the lung, SATB2 was expressed in 5% or more of tumor cells in 29 (74.4%) of 39 small cell carcinomas and 9 (22.5%) of 40 atypical and 26 (40.6%) of 64 typical carcinoid tumors. SATB2 percent tumor cell expression and intensity were higher in small cell carcinomas than in carcinoid tumors (both P < .001, respectively). After adjusting for tumor subtype, SATB2 expression did not correlate with outcome. In the thymus, four (100%) of four atypical carcinoid tumors and one large cell neuroendocrine carcinoma but no small cell carcinoma (n = 2) expressed SATB2 in 5% or more of tumor cells.Conclusions: SATB2 (clone EP281) is expressed in a large subset of pulmonary and thymic neuroendocrine tumors and therefore does not appear to be a useful marker to identify the origin of neuroendocrine tumors. Validation studies are needed, specifically including thymic neuroendocrine tumors, as the expression pattern might be different in those tumors. [ABSTRACT FROM AUTHOR]

Background: C3 glomerulopathy (C3G) is caused by overactivity of the alternative pathway of complement that results in bright glomerular C3 staining with minimal or no deposition of immunoglobulins on immunofluorescence microscopy. Laser microdissection and mass spectrometry of the two subtypes, C3 glomerulonephritis (C3GN) and dense deposit disease (DDD), have identified C3 as the predominant glomerular complement protein, although lesser amounts of C9, C5, C6, C7 and C8 are detectable. C3 plays a central role in complement activity, with its proteolytic cleavage first generating C3a and C3b, followed by inactivation of C3b generating iC3b (which includes C3a and C3b), which undergoes further breakdown yielding C3c and terminal breakdown fragment C3dg. The composition of C3 breakdown products in C3G is not known. Methods: In this study, we chose six cases each of C3GN and DDD to analyze the composition of C3 deposits. We analyzed the amino acid sequence of C3 spectra detected by mass spectrometry to determine the relative abundance of C3 fragments in C3G. Thus we were able to determine the amino acid sequences mapping to the various C3 activation products including C3dg, C3a (C3a1 and a2), and C3b that are part of C3b/iC3b/C3c. Results: C3dg is the predominant cleavage product detected with the highest amino acid coverage. The remaining amino acids map to C3a (C3a1 and a2) and C3b. Amino acids mapping to C3a and C3f are absent. Taken together, the C3a and C3b amino acids represent iC3b prior to or after C3c cleavage of C3dg. The C3 spectra for both C3GN and DDD are surprisingly similar. Conclusion: The finding of large amounts of C3dg suggests that C3b deposition in the glomerulus is an active process triggered by thioester binding of C3b to the glycocalyx overlying the glomerular endothelial cells and glomerular basement membrane. Regulatory protein-mediated inactivation of C3b results in the generation of iC3b. After additional cleavages, mostly C3dg remains. [ABSTRACT FROM AUTHOR]

Background. Complement activation plays an important role in the pathophysiology of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), although it remains unclear which pathway is activated. Whether pauci-immune necrotizing crescentic glomerulonephritis (pauci-immune GN) with negative ANCA serology is part of the spectrum of AAV or a different disease entity is essentially unknown. Methods. We used proteomic analysis to delineate the complement profile in a series of 13 kidney biopsies of patients with pauci-immune GN, with either proteinase 3 (PR3) (five patients) or myeloperoxidase (MPO) antibodies (four patients) or with consistently negative ANCA serology (four patients). Immunofluorescence staining of glomeruli was essentially negative in the PR3-ANCA and MPO-ANCA groups, while a mild staining for C3 was seen in the ANCA-negative cases. No electron-dense deposits were found in the PR3-ANCA and MPO-ANCA groups, but mesangial and few subepithelial deposits were clearly present in the ANCA-negative specimens. Results. Mass spectrometry revealed low spectra numbers for C3 and immunoglobulins in both PR3-positive and MPOpositive patients with minimal or no C4 and C9. In contrast, larger spectra numbers for C3, moderate spectra numbers for C9, complement factor H-related protein-1 and low spectra numbers for C4, C5 and immunoglobulins were found in the ANCA-negative cases. Conclusion. While complement activation is noted in AAV, the complement activation appears to be more prominent in the ANCA-negative glomerulonephritis. The larger amount of C3 and moderate amount of C9 in the ANCA-negative glomerulonephritis implies activation of the alternate and terminal pathway of complement, suggesting that this entity may be caused or promoted by a genetic or acquired defect in the alternative pathway. [ABSTRACT FROM AUTHOR]

The rapid pharmacodynamic response of cells to toxic xenobiotics is primarily coordinated by signal transduction networks, which follow a simple framework: the phosphorylation/dephosphorylation cycle mediated by kinases and phosphatases. However, the time course from initial pharmacodynamic response(s) to cell death following exposure can have a vast range. Viewing this time lag between early signaling events and the ultimate cellular response as an opportunity, we hypothesize that monitoring the phosphorylation of proteins related to cell death and survival pathways at key, early time points may be used to forecast a cell's eventual fate, provided that we can measure and accurately interpret the protein responses. In this paper, we focused on a three-phased approach to forecast cell death after exposure: (1) determine time points relevant to important signaling events (protein phosphorylation) by using estimations of adenosine triphosphate production to reflect the relationship between mitochondrial-driven energy metabolism and kinase response, (2) experimentally determine phosphorylation values for proteins related to cell death and/or survival pathways at these significant time points, and (3) use cluster analysis to predict the dose-response relationship between cellular exposure to a xenobiotic and plasma membrane degradation at 24 h post-exposure. To test this approach, we exposed HepG2 cells to two disparate treatments: a GSK-3β inhibitor and a MEK inhibitor. After using our three-phased approach, we were able to accurately forecast the 24 h HepG2 plasma membrane degradation dose-response from protein phosphorylation values as early as 20 min post-MEK inhibitor exposure and 40 min post-GSK-3β exposure. [ABSTRACT FROM PUBLISHER]

Background Immunotactoid glomerulopathy (ITG) is a rare glomerular disease. Here, we report the largest clinicopathologic series of ITG and define its proteomic profile. Methods The characteristics of 16 ITG patients who were identified from our pathology archives are provided between 1993 and 2011. We also performed laser microdissection and mass spectrometry (LMD/MS) in three cases. Results Presentation included proteinuria (100%), nephrotic syndrome (69%), renal insufficiency (50%) and microhematuria (80%). Hypocomplementemia was present in 46% and a serum M-spike in 63%. Hematologic malignancy was present in 38%, including chronic lymphocytic leukemia in 19%, lymphoplasmacytic lymphoma in 13% and myeloma in 13%. The pattern of glomerular injury was membranoproliferative (56%), membranous (31%) or proliferative (13%) glomerulonephritis. The microtubular deposits were immunoglobulin light chain restricted in 69% and had a mean diameter of 31 nm (range 17–52). During an average of 48 months of follow-up for 12 patients, 50% had remission, 33% had persistent renal dysfunction and 17% progressed to end-stage renal disease. Proteomic analysis by LMD/MS revealed the presence of immunoglobulins, monotypic light chains, complement factors of the classical and terminal pathway and small amount of serum amyloid P-component. Conclusions Hematologic malignancy, particularly lymphoma, is not uncommon in ITG. ITG appears to have a better prognosis than other paraprotein-related renal lesions, with a half of patients expected to recover kidney function with immunosuppressive therapy or chemotherapy. The proteomic profile of ITG is consistent with deposition of monotypic immunoglobulins and activation of the classical and terminal pathway of complement. [ABSTRACT FROM AUTHOR]

We report a 13-year-old Indian boy with nephrotic syndrome caused by renal AA amyloidosis. Workup of the AA amyloidosis revealed chronic hepatitis B. Laser microdissection of the Congo-red-positive glomeruli and vessels followed by liquid chromatography and tandem mass spectrometry confirmed the presence of serum amyloid A (SAA) protein and ruled out hereditary and familial amyloidosis. Furthermore, mass spectrometry also detected a variant of SAA protein (SAA W71R). [ABSTRACT FROM AUTHOR]