A vast majority of pharmacological compounds and their metabolites are excreted via the urine, and within the complex structure of the kidney,the proximal tubules are a main target site of nephrotoxic compounds. We used the model nephrotoxicants mercuric chloride, 2-bromoethylamine hydrobromide, hexachlorobutadiene, mitomycin, amphotericin, and puromycin to elucidate time- and dose-dependent global gene expression changes associated with proximal tubular toxicity. Male Sprague-Dawley rats were dosed via intraperitoneal injection once daily for mercuric chloride and amphotericin (up to 7 doses), while a single dose was given for all other compounds. Animals were exposed to 2 different doses of these compounds and kidney tissues were collected on day 1, 3, and 7 postdosing. Gene expression profiles were generated from kidney RNA using 17K rat cDNA dual dye microarray and analyzed in conjunction with histopathology. Analysis of gene expression profiles showed that the profiles clustered based on similarities in the severity and type of pathology of individual animals. Further, the expression changes were indicative of tubular toxicity showing hallmarks of tubular degeneration/regeneration and necrosis. Use of gene expression data in predicting the type of nephrotoxicity was then tested with a support vector machine (SVM)-based approach. A SVM prediction module was trained using 120 profiles of total profiles divided into four classes based on the severity of pathology and clustering. Although mitomycin C and amphotericin B treatments did not cause toxicity, their expression profiles were included in the SVM prediction module to increase the sample size. Using this classifier, the SVM predicted the type of pathology of 28 test profiles with 100% selectivity and 82% sensitivity. These data indicate that valid predictions could be made based on gene expression changes from a small set of expression profiles. A set of potential biomarkers showing a time- and dose-response with respect to the progression of proximal tubular toxicity were identified. These include several transporters (Slc21a2, Slc15, Slc34a2), Kim 1, IGFbp-1, osteopontin, alpha-fibrinogen, and Gstalpha.

Several clinical trials in oncology have reported increased mortality or disease progression associated with erythropoiesis-stimulating agents. One hypothesis proposes that erythropoiesis-stimulating agents directly stimulate tumor proliferation and/or survival through cell-surface receptors. To test this hypothesis and examine if human tumors utilize the erythropoietin receptor pathway, the response of tumor cells to human recombinant erythropoietin was investigated in disaggregated tumor cells obtained from 186 patients with colorectal, breast, lung, ovarian, head and neck, and other tumors. A cocktail of well characterized tumor growth factors (EGF, HGF, and IGF-1) were analyzed in parallel as a positive control to determine whether freshly-isolated tumor cells were able to respond to growth factor activation ex vivo. Exposing tumor cells to the growth factor cocktail resulted in stimulation of survival and proliferation pathways as measured by an increase in phosphorylation of the downstream signaling proteins AKT and ERK. In contrast, no activation by human recombinant erythropoietin was observed in isolated tumor cells. Though tumor samples exhibited a broad range of cell-surface expression of EGFR, c-Met, and IGF-1R, no cell-surface erythropoietin receptor was detected in tumor cells from the 186 tumors examined (by flow cytometry or Western blot). Erythropoiesis-stimulating agents did not act directly upon isolated tumor cells to stimulate pathways known to promote proliferation or survival of human tumor cells isolated from primary and metastatic tumor tissues.

Wnt-modulator in surface ectoderm (WISE) is a secreted modulator of Wnt signaling expressed in the adult kidney. Activation of Wnt signaling has been observed in renal transplants developing interstitial fibrosis and tubular atrophy; however, whether WISE contributes to chronic changes is not well understood. Here, we found moderate to high expression of WISE mRNA in a rat model of renal transplantation and in kidneys from normal rats. Treatment with a neutralizing antibody against WISE improved proteinuria and graft function, which correlated with higher levels of b-catenin protein in kidney allografts. In addition, treatment with the anti-WISE antibody reduced infiltration of CD68 + macrophages and CD8 + T cells, attenuated glomerular and interstitial injury, and decreased biomarkers of renal injury. This treatment reduced expression of genes involved in immune responses and in fibrogenic pathways. In summary, WISE contributes to renal dysfunction by promoting tubular atrophy and interstitial fibrosis.

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11104 Background: EpoR mRNA and protein expression have been reported at low levels in human tumors implying EpoR may be functional in tumor cells with inferred implications for the use of erythropoiesis stimulating agents in the Oncology setting. However, mRNA studies use bulk tumor tissue which ignores contribution from the stroma and IHC studies have all used Abs that have since been shown to not be specific for EpoR. Therefore this important question remains unresolved. Methods: EpoR expression and function was investigated in viable, non-apoptotic primary human tumor cells (using tumor specific Abs) that were disaggregated from at least 30 patients from each of the following tumor types: breast (incl. metastases), NSC lung, colorectal, and ovarian. Additional tumor types included head and neck, GBM, pancreatic and gastric. Analysis was performed under conditions that were shown to preserve EpoR expression and function in positive control tissues (primary human erythroid progenitors from bone marrow and UT-7 cells). Cell surface EpoR expression was evaluated by flow cytometry using novel EpoR-specific Abs. EpoR function was investigated by analysis of EpoR signaling using phospho-specific Abs specific for STAT5, Erk, Akt etc following ex vivo Epo stimulation (0U- 300U/mL; for 5 and 30 min). Results: No expression of cell surface EpoR was detected in tumor cells in any of the over 130 tumors. In contrast, high levels of expression were observed in positive controls analyzed in parallel. No induction of EpoR signaling was observed in tumor cells at any [Epo], whereas activation was readily detected in tumor cells treated in parallel with a cocktail of known tumor growth factors. Positive controls treated in parallel, showed robust Epo concentration-dependent signaling. No evidence of EpoR expression or function was observed in tumor endothelial cells. Conclusions: These data demonstrate that epithelial tumor cells do not express functional cell surface EpoR and are not responsive to physiological, therapeutic or indeed very high levels of Epo (300U/mL). No significant financial relationships to disclose.