Primary Pulmonary Lymphoid Lesions: Radiologic and Pathologic Findings

The pulmonary lymphoid system is complex and is composed of two compartments: the pulmonary lymphatics and the bronchus-associated lymphoid tissue (BALT). Additional important cells that function in the pulmonary lymphoid system include dendritic cells, Langherhans cells, macrophages, and plasma cells. An appreciation of the normal lymphoid anatomy of the lung as well as its immunology is helpful in understanding the radiologic and pathologic findings of the primary pulmonary lymphoid lesions. Primary lymphoid lesions of the lung arise from the BALT and are uncommon. However, they are increasingly recognized within the growing number of posttransplant patients as well as other patients who are receiving immunosuppressive therapies. Primary lymphoid lesions encompass a wide range of benign and malignant lesions. Benign lymphoid lesions of the lung include reactive lymphoid hyperplasia, follicular bronchiolitis, lymphoid interstitial pneumonia, and nodular lymphoid hyperplasia. Malignant lymphoid lesions of the lung include low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT), other non-Hodgkin lymphomas, and Hodgkin lymphoma. Last, a miscellaneous group of primary lymphoid lesions includes lymphomatoid granulomatosis, posttransplant lymphoproliferative disorders, acquired immunodeficiency syndrome (AIDS)-related lymphoma, and intravascular lymphoma/lymphomatosis. These lesions are best evaluated with multidetector chest computed tomography. The radiologic findings of the primary lymphoid lesions are often nonspecific and are best interpreted in correlation with clinical data and pathologic findings. The purpose of this article is to review pulmonary lymphoid anatomy as well as the most common primary pulmonary lymphoid disorders.

Transbronchial Lung Cryobiopsy for Interstitial Lung Disease Diagnosis: A Perspective From Members of the Pulmonary Pathology Society

Transbronchial lung cryobiopsy involves using a cryoprobe rather than forceps to obtain a bronchoscopic biopsy. Recent studies have shown that transbronchial cryobiopsy provides a larger specimen than conventional transbronchial forceps biopsy, and that the interobserver agreement in the interpretation of cryobiopsy specimens is comparable to that of a surgical lung biopsy. This is encouraging, and transbronchial lung cryobiopsy clearly has a role in the workup and diagnosis of interstitial lung diseases. However, very few patients who have been studied underwent both transbronchial lung cryobiopsy and surgical lung biopsy, and the available data suggest that the diagnostic accuracy of cryobiopsy may not be similar to that of surgical lung biopsy. Further study is needed before transbronchial lung biopsy can be recommended as a replacement for surgical lung biopsy.

Tenascin-C drives persistence of organ fibrosis

The factors responsible for maintaining persistent organ fibrosis in systemic sclerosis (SSc) are not known but emerging evidence implicates toll-like receptors (TLRs) in the pathogenesis of SSc. Here we show the expression, mechanism of action and pathogenic role of endogenous TLR activators in skin from patients with SSc, skin fibroblasts, and in mouse models of organ fibrosis. Levels of tenascin-C are elevated in SSc skin biopsy samples, and serum and SSc fibroblasts, and in fibrotic skin tissues from mice. Exogenous tenascin-C stimulates collagen gene expression and myofibroblast transformation via TLR4 signalling. Mice lacking tenascin-C show attenuation of skin and lung fibrosis, and accelerated fibrosis resolution. These results identify tenascin-C as an endogenous danger signal that is upregulated in SSc and drives TLR4-dependent fibroblast activation, and by its persistence impedes fibrosis resolution. Disrupting this fibrosis amplification loop might be a viable strategy for the treatment of SSc.

Liquid Biopsy in Lung Cancer: A Perspective From Members of the Pulmonary Pathology Society

Liquid biopsy has received extensive media coverage and has been called the holy grail of cancer detection. Attempts at circulating tumor cell and genetic material capture have been progressing for several years, and recent financially and technically feasible improvements of cell capture devices, plasma isolation techniques, and highly sensitive polymerase chain reaction- and sequencing-based methods have advanced the possibility of liquid biopsy of solid tumors. Although practical use of circulating RNA-based testing has been hindered by the need to fractionate blood to enrich for RNAs, the detection of circulating tumor cells has profited from advances in cell capture technology. In fact, the US Food and Drug Administration has approved one circulating tumor cell selection platform, the CellSearch System. Although the use of liquid biopsy in a patient population with a genomically defined solid tumor may potentially be clinically useful, it currently does not supersede conventional pretreatment tissue diagnosis of lung cancer. Liquid biopsy has not been validated for lung cancer diagnosis, and its lower sensitivity could lead to significant diagnostic delay if liquid biopsy were to be used in lieu of tissue biopsy. Ultimately, notwithstanding the enthusiasm encompassing liquid biopsy, its clinical utility remains unproven.

Biomarker Testing in Lung Carcinoma Cytology Specimens: A Perspective From Members of the Pulmonary Pathology Society

The advent of targeted therapy in lung cancer has heralded a paradigm shift in the practice of cytopathology with the need for accurately subtyping lung carcinoma, as well as providing adequate material for molecular studies, to help guide clinical and therapeutic decisions. The variety and versatility of cytologic-specimen preparations offer significant advantages to molecular testing; however, they frequently remain underused. Therefore, evaluating the utility and adequacy of cytologic specimens is critical, not only from a lung cancer diagnosis standpoint but also for the myriad ancillary studies that are necessary to provide appropriate clinical management. A large fraction of lung cancers are diagnosed by aspiration or exfoliative cytology specimens, and thus, optimizing strategies to triage and best use the tissue for diagnosis and biomarker studies forms a critical component of lung cancer management. This review focuses on the opportunities and challenges of using cytologic specimens for molecular diagnosis of lung cancer and the role of cytopathology in the molecular era.

Biomarkers for PD-1/PD-L1 Blockade Therapy in Non-Small-cell Lung Cancer: Is PD-L1 Expression a Good Marker for Patient Selection?

Immunotherapy has emerged as a promising treatment modality in cancer therapy. With improved understanding of how to tip the balance of immune homeostasis, novel therapeutics targeting immune checkpoints have been developed, with durable responses observed in multiple solid tumors, including melanoma, renal cell carcinoma, and non-small-cell lung cancer. Clinical trials have reported favorable responses using programmed cell death-1 protein receptor (PD-1)/programmed cell death-1 protein ligand (PD-L1) blockade as monotherapy and most impressively in combinatorial trials with cytotoxic T-lymphocyte antigen-4 protein blockade. Nonetheless, a clinical benefit has not been observed in all patients. Therefore, identifying the ideal biomarkers for patient selection would be of great value in optimizing and personalizing immunotherapy. The utility of PD-L1 expression as a biomarker has varied in different clinical trials and immunohistochemistry assays. In addition, the response to immune checkpoint inhibition has been complicated by PD-L1 expression as a marker influenced by the dynamic tumor microenvironment. No consensus has yet been reached on whether PD-L1 expression is an ideal marker for patient selection. Recent research has shown promise for alternative markers, including T-cell immunohistochemistry, other immunologic markers, T-cell receptor clonality, and somatic mutational burden. However, additional studies are needed to assess the value of these as practical predictive biomarkers for patient selection and treatment response.

Programmed Death Ligand-1 Immunohistochemistry— A New Challenge for Pathologists: A Perspective From Members of the Pulmonary Pathology Society

The binding of programmed death ligand-1 and ligand-2 (PD-L1 and PD-L2) to PD-1 blocks T-cell–mediated immune response to tumor. Antibodies that target programmed death receptor-1 (PD-1) will block the ligand-receptor interface, thereby allowing T cells to attack the tumor and increase antitumor immune response. In clinical trials, PD-1 inhibitors have been associated with an approximately 20% overall response rate in unselected patients with non–small cell lung cancer, with sustained tumor response in a subset of patients treated by these immune checkpoint inhibitors. Facing a proliferation of PD-L1 immunohistochemistry clones, staining platforms, and scoring criteria, the pathologist must decide on the feasibility of introducing a newly approved companion diagnostic assay that may require purchase not only of a specific antibody kit but of a particular staining platform. Given the likely reality that clinical practice may, in the near future, demand access to 4 different PD-L1 antibodies coupled with different immunohistochemistry platforms, laboratories will be challenged with deciding among this variety of testing methods, each with its own potential benefits. Another immediate challenge to PD-L1 testing in lung cancer patients is that of access to adequate tumor tissue, given that non–small cell lung cancer samples are often extremely limited in size. With PD-L1 testing it has become clear that the historically used US regulatory approach of one assay–one drug will not be sustainable. One evolving concept is that of complementary diagnostics, a novel regulatory pathway initiated by the US Food and Drug Administration, which is distinct from companion diagnostics in that it may present additional flexibility. Although pathologists need to face the practical reality that oncologists will be asking regularly for the PD-L1 immunohistochemistry status of their patients' tumors, we should also keep in mind that there may be room for improvement of biomarkers for immunotherapy response. The field is rich with opportunities for investigation into biomarkers of immunotherapy response, particularly in the form of collaborative, multidisciplinary studies that incorporate oncologists, pathologists, and basic scientists. Pathologists must take the lead in the rational incorporation of these biomarkers into clinical practice.

Cytomorphologic findings of malignant mesothelioma in FNA biopsies and touch preps of core biopsies

BACKGROUND

Given the lack of recent literature regarding the aspiration cytology of immunohistochemically confirmed malignant mesothelioma (MM), we were interested in reviewing the experience of our institution and establishing useful morphologic criteria.

METHODS

Seventeen aspiration and touch preparation specimens with a diagnosis of MM obtained between 2002-2013 were reviewed along with 20 cases of adenocarcinoma and 16 cases of squamous cell carcinoma. The utility of a number of morphologic features was evaluated.

RESULTS

In most cases of MM, a consistent pattern emerged. Aspirates and touch preps were cellular with irregularly shaped 2 and 3 dimensional clusters. The individual cells were predominantly angulated and had dense cytoplasm with eccentric nuclei. In every case, a minority of tumor cells contained prominent microvacuoles. The chromatin pattern tended to be fine with small nucleoli. While most cases were cytologically monotonous, five cases displayed striking pleomorphism and three cases contained occasional large atypical cells. Two cases contained metachromatic background material. Features which were most useful in discriminating MM from adenocarcinoma were angulated cell shape(P = 0.0002), dense cytoplasm(P = 0.0001), and cytoplasmic microvacuoles(P = 0.0001). In our material, cases of squamous cell carcinoma were often difficult to distinguish from MM. Useful discriminatory features present in squamous cell carcinoma included ink dot nuclei(P = 0.0003), a "dirty" cystic, necrotic background (P = 0.0027) and tumor balls with peripheral spindling(P = 0.0041).

CONCLUSION

Most cases of MM have a consistent appearance in core biopsy touch preps and FNAs. Distinguishing MM from adenocarcinoma and squamous cell carcinoma can be facilitated by evaluating a few key morphologic features.

Early stage lung cancer detection in systemic sclerosis does not portend survival benefit: a cross sectional study

Background

Systemic Sclerosis (SSc) is a rare connective tissue disorder associated with an increased risk of malignancy including lung cancer.

Methods

A single center review of all cases of lung cancer in patients with SSc was conducted. Clinical, radiographic, and detailed pathologic data was collected. Risk factors were compared with our center’s SSc Registry. Cancer characteristics were compared with the National Cancer Institute SEER Cancer Statistics (NCI SEER) data.

Results

17 cases were identified; the majority were females (82%) with the lung cancers diagnosed after the onset of SSc (88%). Tobacco use was identified in 65% of cases. Serologic testing showed 50% of cases were Scl-70 positive. Twelve cases had radiographic evidence of SSc lung involvement, however only 6 had restrictive physiology on pulmonary function testing. Thirteen cases had pulmonary nodules preceding lung cancer. Thirteen of the cancers were adenocarcinoma. Ten underwent molecular mutational profiling: 2/8 had KRAS mutation and 1/10 had EGFR mutation. More of the non-small cell lung cancers were diagnosed at localized disease (56%) than in the NCI SEER database. However, 5 years survival among the stage I cases was 25% versus an expected survival of 54%.

Conclusions

The high proportion of adenocarcinomas seen in our study is different from that reported in the literature. Lung cancers were diagnosed at an early stage, likely due to our center’s practice of radiographic screening for SSc associated lung involvement, however this did not confer a survival advantage. A high proportion of patients who developed lung cancer had interstitial lung disease.

Peripheral lung adenocarcinomas with KRAS mutations are more likely to invade visceral pleura

CONTEXT

Kirsten-RAS (KRAS) mutations play an important role in the carcinogenesis of a subset of lung adenocarcinomas and are associated with poorer prognosis.

OBJECTIVE

To investigate the relationship of KRAS mutation status to the histologic subtype of adenocarcinoma according to the recent classification, patient demographics, tumor size, predominant histologic subtype, nodal status, and visceral pleural invasion, in an attempt to uncover the reason for the worse prognosis associated with KRAS mutation.

DESIGN

A total of 187 consecutive resected lung adenocarcinomas from our institution from 2008 to 2011 that were diagnosed according to the new International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification and screened for KRAS mutations were included in the study.

RESULTS

A total of 32% of the adenocarcinomas harbored the KRAS mutation. The median age in the KRAS mutation group was 69 years (range, 43-86 years), and male to female ratio was 1:2.3. The proportion of heavy smokers was significantly higher in tumors with KRAS mutation compared with wild type (83% versus 62%; P = .01). A total of 27% of tumors with KRAS mutation had pleural invasion versus 11% of tumors without KRAS mutation (P = .009). A total of 59 tumor samples were positive for KRAS mutation (25 for G12C, 14 for G12A, 8 for G12V, 7 for G12D, 3 for G12S, and 1 for G12T), and only 3 tumors harbored codon 13 mutations (G13C). Two tumors had double mutations.

CONCLUSIONS

KRAS mutations are more common in heavy smokers, and lung adenocarcinomas with KRAS mutation are more likely to invade the visceral pleura. Increased frequency of visceral pleural invasion may explain in part the worse prognosis associated with KRAS mutations.

Correlation of EGFR mutation status with predominant histologic subtype of adenocarcinoma according to the new lung adenocarcinoma classification of the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society

CONTEXT

Epidermal growth factor receptor (EGFR) mutations have been identified as predictors of response to EGFR tyrosine kinase inhibitors in non-small cell lung cancer.

OBJECTIVE

To investigate the relationship of EGFR mutation status to the histologic subtype of adenocarcinoma according to the new International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) classification.

DESIGN

We screened EGFR mutation in 200 consecutive lung adenocarcinoma resection specimens diagnosed between 2008 and 2011.

RESULTS

Among 200 lung adenocarcinomas, EGFR mutations were identified in 41 tumors (20.5%). The mean age in the EGFR-mutant group was 64.8 years and this group consisted of 78% females and 22% males. Most patients with EGFR-positive lung cancers were never-smokers (51%) as compared to 8% with EGFR-negative cancers (P < .001). The most common mutations identified in our population were deletions in exon 19 (22 patients) and L858R in exon 21 (12 patients). Five patients had double mutations. The predominant pattern of adenocarcinoma was lepidic (44%) in EGFR-mutant lung cancers as compared to 69% with acinar pattern in EGFR wild-type lung cancers (P < .001). Of 22 minimally invasive adenocarcinomas, 8 (36%) had EGFR mutations, accounting for 20% of adenocarcinomas with EGFR mutations (P < .05).

CONCLUSIONS

Based on the new IASLC/ATS/ERS classification, the predominant subtype of adenocarcinoma was lepidic (44%) in EGFR-mutant lung cancers (P < .001). However, histologic subtype should not be used to exclude patients from tyrosine kinase inhibitor therapy, since EGFR mutations are found in lung adenocarcinomas of other subtypes.

Molecular profiling in non-small cell lung cancer: a step toward personalized medicine

CONTEXT

Lung carcinoma is the result of sequential accumulation of genetic and epigenetic changes. Lung adenocarcinoma is a heterogeneous disease with diverse somatic mutations, and several of them include the so-called driver mutations, which may serve as "druggable" therapeutic targets. Thus, development of personalized approaches for the treatment of non-small cell lung carcinoma (NSCLC) mandates that pathologists make a precise histologic classification inclusive of routine molecular analysis of such tumors.

OBJECTIVE

To address the molecular mechanisms underlying NSCLC and how this knowledge reflects the multidisciplinary approach in the diagnosis and management of these patients. We will also summarize the current available and investigational personalized therapies for patients with resectable early-stage, unresectable locally advanced, and metastatic NSCLC.

DATA SOURCES

Peer-reviewed published literature and personal experience.

CONCLUSIONS

There are multiple mechanisms involved in the pathogenesis of lung cancer, which operate in parallel and involve pathways of activation and inhibition of various cellular events. Further research is essential to characterize the histologic and mutational profiles of lung carcinomas, which will ultimately translate into improved and more personalized therapeutic management of patients with lung cancer.

Chondroblastoma-like chondroma of soft tissue: report of the first case in the base of skull

Chondroblastoma-like chondroma (CLC) of soft tissue is a rare benign neoplasm that usually involves the soft tissues of the hand. This report describes the first case of CLC of soft tissue arising in the base of the skull. A 33-year-old man was seen with a slow growing mass in the right parotid region of his face. The noncontrast computed tomographic scans showed an 8.5-cm mass with calcifications involving the right masticator space and extending through the bone into the middle cranial fossa. The radiologic differential diagnosis included osteosarcoma, leiomyosarcoma, chondrosarcoma, and giant cell tumor. During surgery, the large lateral skull base tumor appeared to involve the middle and infratemporal fossae and eroded the surrounding bone. Although the tumor was removed piecemeal, total excision was performed. On microscopic examination, the tumor displayed lobules of mature hyaline cartilage with numerous chondroblasts, coarse calcifications including chicken wire calcifications, and scattered osteoclasts. No atypia, mitoses, necrosis, or osteoid formation was seen. The tumor was diagnosed as chondroma with chondroblastoma features of the soft tissue. His postoperative clinical course was uneventful; however, after 7 months, he had a local recurrence identified on follow-up magnetic resonance imaging. He underwent repeat surgical excision of the tumor, which showed similar histology as the previous excision. This large skull based tumor eroding the bone, which clinically and radiologically mimicked a malignant process, was an unusual presentation of a benign cartilaginous neoplasm. Pathologists should be aware that CLC may occur in the base of the skull and this lesion should be differentiated from the other benign or malignant tumors arising in this area. These lesions have a potential for local recurrence; hence, a close follow-up is recommended.

Renal morphologic lesions reminiscent of diabetic nephropathy

CONTEXT

Nodular, intercapillary glomerulosclerotic lesions resembling Kimmelstiel-Wilson nodules commonly observed in diabetic nephropathy can also be seen in patients without any clinical history or evidence of diabetes.

OBJECTIVES

To discuss the pathobiology of lesions reminiscent of diabetes nephropathy, including light-chain deposition disease, amyloidosis, immunotactoid nephropathy, the membranoproliferative form of glomerulonephritis, and idiopathic nodular glomerulosclerosis, and how to differentiate them from diabetic nephropathy.

DATA SOURCES

Published literature and authors' personal experience.

CONCLUSIONS

The well-formed, intercapillary, nodular mesangial lesions, along with thickened glomerular basement membranes and tubular basement membranes, and hyaline arteriolosclerosis are virtually pathognomic of diabetic nephropathy. However, the pathologist must exclude lesions reminiscent of diabetic nephropathy by performing special stains on histologic sections, immunofluorescence, and electron microscopic studies.

Lymphoproliferative neoplasms of the lung: a review

CONTEXT

Diagnosis and classification of lymphomas are based on the morphologic, immunologic, and genetic features that the lesional cells share with their normal B and T lymphocyte counterparts. Primary pulmonary lymphomas account for 0.3% of primary lung neoplasms and less than 0.5% of all lymphomas.

OBJECTIVE

To describe and summarize the clinical and histopathologic features of the primary pulmonary lymphoma and secondary involvement of the lung by lymphoma.

DATA SOURCES

Peer-reviewed published literature and personal experience.

CONCLUSIONS

Diagnosis of clonal lymphoid proliferations in the lung has evolved owing to the greater utility of molecular and flow cytometric analysis of tissue. Further studies are needed to best define the clinical and prognostic features, as well as search for targeted therapy for these patients with rare neoplasms.

Transcription factor E3 protein-positive perivascular epithelioid cell tumor of the appendix presenting as acute appendicitis: a case report and review of the literature

Perivascular epithelioid cell tumors (PEComas) are a group of mesenchymal tumors that coexpress melanocytic and smooth muscle markers; their exact origin remains unknown. This group includes renal angiomyolipoma, clear cell sugar tumor, and lymphangioleiomyomatosis, although the term perivascular epithelioid cell tumors is currently used for lesions that exhibit a similar morphologic and immunohistochemical profile throughout the human body. Recently, a distinct subset of PEComas has been shown to harbor transcription factor E3 gene (TFE3) fusions. We report, for the first time, a unique case of TFE3-positive PEComa presenting as acute appendicitis in a 24-year-old woman. Microscopically, the tumor was composed of benign-appearing epithelioid cells with clear and eosinophilic cytoplasm, and arranged in nested and alveolar patterns. Immunohistochemical studies showed diffuse strong positivity for neuron-specific enolase, TFE3, and progesterone receptor and focal strong positivity for human melanoma black-45 (HMB-45) and melanocyte differentiation antigen (Melan-A) in the tumor cells. Although rare, PEComa should be included in the differential diagnosis of mesenchymal tumors of the appendix.

Inflammatory aortic aneurysm: possible manifestation of IgG4-related sclerosing disease

In this study, we investigate the hypothesis that IgG4-related autoimmune reaction is involved in the formation of inflammatory aortic aneurysms (IAA). We obtained 23 cases of IAA and 11 cases of atherosclerotic aortic aneurysms (AAA) as control group. We evaluated the expression of IgG4 in both IAA study cases and AAA control cases. In addition, immunohistochemical expression of C-Kit, CD21, CD34, S-100 protein, SMA, vimentin, p53, beta-catenin, and ALK-1, and EBV-LMP1 expression by in situ hybridization were performed only in IAA cases. Of the 23 patients, 20 were males and 3 were females (M: F ratio 6.7:1); age ranged from 43 to 81 years (average 64.3 years). Histologically, all 23 cases of IAA formed a mass that displayed inflammatory myofibroblastic tumor-like features. All lesions stained strongly and diffusely for vimentin and SMA (100%); 17 stained strongly and focally for CD34 (74%); and all were negative for C-Kit, CD21, S-100 protein, p53, beta-catenin, EBV-LMP1, and ALK-1. The numbers of infiltrating IgG4-positive plasma cells in IAA cases exceed that of AAA cases. Score 3 (>50 plasma cells/one 40X field) of IgG4-positive plasma cells was only seen in IAA cases (13/23, 57%), whereas none of the 11 cases of AAA showed score 3 IgG4-positive plasma cells (P=0.0018, Fischer's exact test). Our findings suggest that IAA may be an aortic manifestation of the IgG4-related sclerosing disease. The high number of positive plasma cells, >50 plasma cells/one 40X field is more specific for the IAA than for AAA; however, lesser number can be seen in both IAA and AAA patients.

Role of extracellular matrix renal tubulo-interstitial nephritis antigen (TINag) in cell survival utilizing integrin (alpha)vbeta3/focal adhesion kinase (FAK)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B-serine/threonine kinase (AKT) signaling pathway

Tubulo-interstitial nephritis antigen (TINag) is an extracellular matrix protein expressed in tubular basement membranes. Combined mutations in TINag and nephrocystin-1 genes lead to nephronophthisis with reduced cell survival. Because certain extracellular matrix proteins are known to modulate cell survival, studies were initiated in Lewis rats lacking TINag to assess if they are more susceptible to cisplatin-induced injury. Cisplatin induced a higher degree of tubular cell damage and apoptosis in regions where TINag is expressed in a parental Wistar strain. This was accompanied by an accentuated increase in serum creatinine and Kim-1 RNA and renal expression of Bax, p53, and its nuclear accumulation, mtDNA fragmentation, and a decrease of Bcl-2. Cisplatin induced fulminant apoptosis of HK-2 cells with increased caspase3/7 activity, mtDNA fragmentation, and a reduced cell survival. These effects were partially reversed in cells maintained on TINag substratum. Far Western/solid phase assays established TINag binding with integrin αvβ3 comparable with vitronectin. Transfection of cells with αv-siRNA accentuated cisplatin-induced apoptosis, aberrant translocation of cytochrome c and Bax, and reduced cell survival. The αv-siRNA decreased expression of integrin-recruited focal adhesion kinase (FAK) and p-FAK, while increasing the expression of p53 and p-p53. Similarly, p-AKT was reduced although ILK was unaffected. Inhibition of PI3K had similar adverse cellular effects. These effects were ameliorated in cells on TINag substratum. In vivo, a higher degree of decrease in the expression of p-FAK and pAKT was observed in Lewis rats following cisplatin treatment. These in vivo and in vitro studies demonstrate an essential role of TINag in cellular survival to maintain proper tubular homeostasis utilizing integrin αvβ3 and downstream effectors.

Epac1-mediated, high glucose-induced renal proximal tubular cells hypertrophy via the Akt/p21 pathway

The mechanisms involved in tubular hypertrophy in diabetic nephropathy are unclear. We investigated the role of exchange protein activated by cAMP 1(Epac1), which activates Rap-family G proteins in cellular hypertrophy. Epac1 is expressed in heart, renal tubules, and in the HK-2 cell line. In diabetic mice, increased Epac1 expression was observed, and under high glucose ambience (HGA), HK-2 cells also exhibited increased Epac1 expression. We isolated a 1614-bp DNA fragment upstream of the initiation codon of Epac1 gene, inclusive of glucose response elements (GREs). HK-2 or COS7 cells transfected with the Epac1 promoter revealed a dose-dependent increase in its activity under HGA. Mutations in GRE motifs resulted in decreased promoter activity. HK-2 cells exhibited a hypertrophic response and increased protein synthesis under HGA, which was reduced by Epac1-siRNA or -mutants, whereas the use of a protein kinase A inhibitor had minimal effect. Epac1 transfection led to cellular hypertrophy and increased protein synthesis, which was accentuated by HGA. HGA increased the proportion of cells in the G0/G1 cell-cycle phase, and the expression of pAkt and the cyclin-dependent kinase inhibitors p21 and p27 was increased while the activity of cyclin-dependent kinase 4 decreased. These effects were reversed following transfection of cells with Epac1-siRNA or -mutants. These data suggest that HGA increases GRE-dependent Epac1 transcription, leading to cell cycle arrest and instigation of cellular hypertrophy.

Transcriptional and post-translational modulation of myo-inositol oxygenase by high glucose and related pathobiological stresses

Renal-specific oxidoreductase/myo-inositol oxygenase (RSOR/MIOX) catabolizes myo-inositol and is implicated in the pathogenesis of diabetic nephropathy. How high glucose (HG) ambience up-regulates its expression and enzyme activity was investigated. MIOX up-regulation was associated with an increase in enzyme activity, which was reduced to basal levels with phosphatase treatment. Using phosphothreonine, protein kinase A (PKA), and PKC substrate antibodies, analyses of kidney lysates of diabetic animals and LLC-PK1/HK-2 cells subjected to HG ambience indicated MIOX to be a phosphoprotein. Kinase phosphorylated recombinant RSOR/MIOX proteins had increased activity confined to exons 2-5. Mutants with substituted phosphorylation sites had a minimal increase in activity. Treatment of cells with PKC, PKA, and PDK1 kinase activators increased activity, whereas inhibitors reduced it. Inhibitors also reduced the phosphorylation and activity of MIOX induced by HG. Besides HG, exposure of cells to oxidants H(2)O(2) and methylglyoxal up-regulated MIOX expression and its phosphorylation and activity, whereas antioxidants N-acetylcysteine, β-naphthoflavone, and tertiary butyl hydroquinone reduced MIOX expression. Treatment with HG or oxidants or overexpression of MIOX induced nuclear translocation of redox-sensitive transcription factor Nrf2, which binds to antioxidant response elements of various promoters. Promoter analyses revealed an increase in luciferase activity with HG and oxidants. Analyses of antioxidant response elements and carbohydrate response elements revealed an accentuation of DNA-protein interactions with oxidants and under HG ambience. ChIP-PCR and immunofluorescence studies revealed nuclear translocation of carbohydrate response element-binding protein. These findings suggest that phosphorylation of RSOR/MIOX enhances its activity, which is augmented by HG via transcriptional/translational events that are also modulated by diabetes-related pathobiological stresses.