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Epithelial-to-mesenchymal transition (EMT) is an important developmental process, participates in tissue repair, and occurs during pathologic processes of tumor invasiveness, metastasis, and tissue fibrosis. The molecular mechanisms leading to EMT are poorly understood. Although it is well documented that transforming growth factor (TGF)-β plays a central role in the induction of EMT, the targets of TGF-β signaling are poorly defined. We have shown earlier that Na,K-ATPase β1-subunit levels are highly reduced in poorly differentiated kidney carcinoma cells in culture and in patients' tumor samples. In this study, we provide evidence that Na,K-ATPase is a new target of TGF-β1–mediated EMT in renal epithelial cells, a model system used in studies of both cancer progression and fibrosis. We show that following treatment with TGF-β1, the surface expression of the β1-subunit of Na,K-ATPase is reduced, before well-characterized EMT markers, and is associated with the acquisition of a mesenchymal phenotype. RNAi-mediated knockdown confirmed the specific involvement of the Na,K-ATPase β1-subunit in the loss of the epithelial phenotype and exogenous overexpression of the Na,K-ATPase β1-subunit attenuated TGF-β1–mediated EMT. We further show that both Na,K-ATPase α- and β-subunit levels are highly reduced in renal fibrotic tissues. These findings reveal for the first time that Na,K-ATPase is a target of TGF-β1–mediated EMT and is associated with the progression of EMT in cancer and fibrosis. Mol Cancer Ther; 9(6); 1515–24. ©2010 AACR.

Na,K-ATPase is composed of two essential alpha- and beta-subunits, both of which have multiple isoforms. Evidence indicates that the Na,K-ATPase enzymatic activity as well as its alpha(1), alpha(3) and beta(1) isoforms are reduced in the failing human heart. The catalytic alpha-subunit is the receptor for cardiac glycosides such as digitalis, used for the treatment of congestive heart failure. The role of the Na,K-ATPase beta(1)-subunit (Na,K-beta(1)) in cardiac function is not known. We used Cre/loxP technology to inactivate the Na,K-beta(1) gene exclusively in the ventricular cardiomyocytes. Animals with homozygous Na,K-beta(1) gene excision were born at the expected Mendelian ratio, grew into adulthood, and appeared to be healthy until 10 months of age. At 13-14 months, these mice had 13% higher heart/body weight ratios, and reduced contractility as revealed by echocardiography compared to their wild-type (WT) littermates. Pressure overload by transverse aortic constriction (TAC) in younger mice, resulted in compensated hypertrophy in WT mice, but decompensation in the Na,K-beta(1) KO mice. The young KO survivors of TAC exhibited decreased contractile function and mimicked the effects of the Na,K-beta(1) KO in older mice. Further, we show that intact hearts of Na,K-beta(1) KO anesthetized mice as well as isolated cardiomyocytes were insensitive to ouabain-induced positive inotropy. This insensitivity was associated with a reduction in NCX1, one of the proteins involved in regulating cardiac contractility. In conclusion, our results demonstrate that Na,K-beta(1) plays an essential role in regulating cardiac contractility and that its loss is associated with significant pathophysiology of the heart.

Introduction Cyclooxygenase-2 overexpression may mediate resistance to epidermal growth factor receptor tyrosine kinase inhibition through prostaglandin E2-dependent promotion of epithelial to mesenchymal transition (EMT). Suppression of epithelial markers, such as E-cadherin, can lead to resistance to erlotinib. Prostaglandin E2 down-regulates E-cadherin expression by up-regulating transcriptional repressors, including ZEB1 and Snail. Furthermore, E-cadherin can be modulated by matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs), promoting tumor invasion and metastasis. Markers of EMT and tumor invasion were evaluated in patient serum from a phase I clinical trial investigating the combination of celecoxib and erlotinib in non-small cell lung cancer (NSCLC) patients. Methods Samples from 22 subjects were evaluated. Soluble E-cadherin (sEC) was evaluated by enzyme linked immunosorbent assay in patient serum at baseline, week 4, and week 8 of treatment. Other markers of EMT and angiogenesis were evaluated by enzyme linked immunosorbent assay, including MMP-9, TIMP-1, and CCL15. Results Serum sEC, MMP-9, TIMP-1, and CCL15 levels were determined at baseline and week 8. Patients with a partial response to therapy had a significant decrease in sEC, TIMP-1, and CCL15 at week 8. In patients who responded to the combination therapy, baseline MMP-9 was significantly lower compared with nonresponders (p = 0.006). Conclusions sEC, MMP-9, TIMP-1, and CCL15 levels correlate with response to combination therapy with erlotinib and celecoxib in patients with NSCLC. A randomized phase II trial is planned comparing erlotinib and celecoxib with erlotinib plus placebo in advanced NSCLC. This study will prospectively assess these and other biomarkers in serum and tumor tissue.

Prostate-specific membrane antigen (PSMA) is an important biomarker expressed in prostate cancer cells with levels proportional to tumor grade. The membrane association and correlation with disease stage portend a promising role for PSMA as an antigenic target for antibody-based therapies. Successful application of such modalities necessitates a detailed knowledge of the subcellular localization and trafficking of target antigen. In this study, we show that PSMA is expressed predominantly in the apical plasma membrane in epithelial cells of the prostate gland and in well-differentiated Madin-Darby canine kidney cells. We show that PSMA is targeted directly to the apical surface and that sorting into appropriate post-Golgi vesicles is dependent upon N-glycosylation of the protein. Integrity of the microtubule cytoskeleton is also essential for delivery and retention of PSMA at the apical plasma membrane domain, as destabilization of microtubules with nocodazole or commonly used chemotherapeutic Vinca alkaloids resulted in the basolateral expression of PSMA and increased the uptake of anti-PSMA antibody from the basolateral domain. These results may have important relevance to PSMA-based immunotherapy and imaging strategies, as prostate cancer cells can maintain a well-differentiated morphology even after metastasis to distal sites. In contrast to antigens on the basolateral surface, apical antigens are separated from the circulation by tight junctions that restrict transport of molecules across the epithelium. Thus, antigens expressed on the apical plasma membrane are not exposed to intravenously administered agents. The ability to reverse the polarity of PSMA from apical to basolateral could have significant implications for the use of PSMA as a therapeutic target.

Summary Na,K-ATPase is a hetero-oligomer of an α- and a β-subunit. The α-subunit (Na,K-α) possesses the catalytic function, whereas the β-subunit (Na,K-β) has cell-cell adhesion function and is localized to the apical junctional complex in polarized epithelial cells. Earlier, we identified two distinct conserved motifs on the Na,K-β1 transmembrane domain that mediate protein-protein interactions: a glycine zipper motif involved in the cis homo-oligomerization of Na,K-β1 and a heptad repeat motif that is involved in the hetero-oligomeric interaction with Na,K-α1. We now provide evidence that knockdown of Na,K-β1 prevents lumen formation and induces activation of extracellular regulated kinases 1 and 2 (ERK1/2) mediated by phosphatidylinositol 3-kinase in MDCK cells grown in three-dimensional collagen cultures. These cells sustained cell proliferation in an ERK1/2-dependent manner and did not show contact inhibition at high cell densities, as revealed by parental MDCK cells. This phenotype could be rescued by wild-type Na,K-β1 or heptad repeat motif mutant of Na,K-β1, but not by the glycine zipper motif mutant that abrogates Na,K-β1 cis homo-oligomerization. These studies suggest that Na,K-β1 cis homo-oligomerization rather than hetero-oligomerization with Na,K-α1 is involved in epithelial lumen formation. The relevance of these findings to pre-neoplastic lumen filling in epithelial cancer is discussed.

High levels of the soluble form of E-cadherin can be found in the serum of cancer patients and are associated with poor prognosis. Despite the possible predictive value of soluble E-cadherin, little is understood concerning its patho-physiological consequences in tumor progression. In this study, we show that soluble E-cadherin facilitates cell survival via functional interaction with cellular E-cadherin. Exposure of cells to a recombinant form of soluble E-cadherin, at a concentration found in cancer patient's serum, prevents apoptosis due to serum/growth factor withdrawal, and inhibits epithelial lumen formation, a process that requires apoptosis. Further, soluble E-cadherin-mediated cell survival involves activation of the epidermal growth factor receptor (EGFR) and EGFR-mediated activation of both phosphoinositide-3 kinase (PI3K)/AKT and ERK1/2 signaling pathways. These results are evidence of a complex functional interplay between EGFR and E-cadherin and also suggest that the presence of soluble E-cadherin in cancer patients' sera might have relevance to cell survival and tumor progression.

Na,K-ATPase also known as the sodium pump, is an oligomeric membrane bound enzyme that catalyzes ATP-dependent transport of three Na + ions out and two K + ions into the cell. It plays an important role in cardiac function by influencing the intracellular Ca 2+ levels via the Na + /Ca 2+ exchanger and thereby cardiac contractility. Na,K-ATPase is composed of two essential subunits, alpha-subunit and beta-subunit, both of which have multiple isoforms. The alpha subunit, which is also the catalytic subunit, is the receptor for cardiac glycosides such as digitalis, used for the treatment of congestive heart failure. Evidence indicates that Na,K-ATPase alpha1, alpha2 and beta1 isoforms as well as the Na,K-ATPase enzymatic activity is reduced in the failing human heart. Heterozygous knockout mice of the alpha-subunit isoforms had altered cardiac contractility. However, nothing much is known about the role of the beta-subunit in cardiac function. To investigate the role of beta-subunit in the myocardium, we used Cre/loxP technology to inactivate the beta-subunit gene exclusively in ventricular cardiac myocytes. Animals with homozygous ventricular myocyte beta-subunit gene excision were born at the expected Mendelian ratio, grew into adulthood, and appeared to be healthy until 9 months of age. These animals had ~20% and ~50% of control levels of beta-subunit and alpha-subunit protein in the heart respectively. At 13–14 months of age, these mice had 24% higher heart/body weight ratios, elevated levels of markers of cardiac hypertrophy such as ANP, BNP, alpha MHC, alpha skeletal actin, and reduced contractility by echocardiography (56.7% versus 66.4% EF in the WT, n = 7 each) as compared to their WT littermates. Pressure overload by transverse aortic constriction in younger mice, resulted in compensated hypertrophy in WT mice, but 50% of Na,K-beta knockout mice died soon after TAC. The few survivors exhibited decreased contractile function (50% as compared to 71% EF in WT, n = 4 each) and mimicked the effects of Na,K-beta knockout in old mice. In conclusion, our results suggest that loss of beta-subunit leads to significant pathophysiology from altered ionic homeostasis in the heart.

To evaluate whether beta-catenin signaling has a role in the regulation of angiogenesis in colon cancer, a series of angiogenesis-related gene promoters was analyzed for beta-catenin/TCF binding sites. Strikingly, the gene promoter of human vascular endothelial growth factor (VEGF, or VEGF-A) contains seven consensus binding sites for beta-catenin/TCF. Analysis of laser capture microdissected human colon cancer tissue indicated a direct correlation between up-regulation of VEGF-A expression and adenomatous polyposis coli (APC) mutational status (activation of beta-catenin signaling) in primary tumors. In metastases, this correlation was not observed. Analysis by immunohistochemistry of intestinal polyps in mice heterozygous for the multiple intestinal neoplasia gene (Min/+) at 5 months revealed an increase and redistribution of VEGF-A in proximity to those cells expressing nuclear beta-catenin with a corresponding increase in vessel density. Transfection of normal colon epithelial cells with activated beta-catenin up-regulated levels of VEGF-A mRNA and protein by 250-300%. When colon cancer cells with elevated beta-catenin levels were treated with beta-catenin antisense oligodeoxynucleotides, VEGF-A expression was reduced by more than 50%. Taken together, our observations indicate a close link between beta-catenin signaling and the regulation of VEGF-A expression in colon cancer.

Deregulated signaling through the phosphatidylinositol 3'-kinase (PI3K) pathway is common in many types of cancer, including glioblastoma. Dissecting the molecular events associated with activation of this pathway in glioblastoma patients in vivo presents an important challenge that has implications for the development and clinical testing of PI3K pathway inhibitors. Using an immunohistochemical analysis applied to a tissue microarray, we performed hierarchical clustering and multidimensional scaling, as well as univariate and multivariate analyses, to dissect the PI3K pathway in vivo. We demonstrate that loss of the tumor suppressor protein PTEN, which antagonizes PI3K pathway activation, is highly correlated with activation of the main PI3K effector Akt in vivo. We also show that Akt activation is significantly correlated with phosphorylation of mammalian target of rapamycin (mTOR), the family of forkhead transcription factors (FOXO1, FOXO3a, and FOXO4), and S6, which are thought to promote its effects. Expression of the mutant epidermal growth factor receptor vIII is also tightly correlated with phosphorylation of these effectors, demonstrating an additional route to PI3K pathway activation in glioblastomas in vivo. These results provide the first dissection of the PI3K pathway in glioblastoma in vivo and suggest an approach to stratifying patients for targeted kinase inhibitor therapy.

The first version of the Human Combinatorial Antibody Library (HuCAL) is a single-chain Fv-based phage display library (HuCAL-scFv) with 2x10(9) members optimised for high-throughput generation and targeted engineering of human antibodies. 61% of the library genes code for functional scFv as judged by sequencing. We show here that since HuCAL-scFv antibodies are expressed in high levels in Escherichia coli, automated panning and screening in miniaturised settings (96- and 384-well format) have now become feasible. Additionally, the unique modular design of HuCAL-genes and -vectors allows the distinctly facilitated conversion of scFv into Fab, miniantibody and immunoglobulin formats, and the fusion with a variety of effector functions and tags not only convenient for therapeutic applications but also for high-throughput purification and detection. Thus, the HuCAL principle enables the rapid and high-throughput development of human antibodies by optimisation strategies proven useful in classical low molecular weight drug development. We demonstrate in this report that HuCAL is a very convenient source of human antibodies for various applications.

20 Background: The standard of care for esophageal cancer (EC) patients is a trimodality approach that includes chemo− and radiotherapy followed by surgery. Approximately 25% of EC patients exhibit pathCR to chemoradiotherapy, but undergo unnecessary surgical resection procedures. A set of three protein biomarkers (NF−kB, SHH, and Gli−1) able to effectively identify pathCR status from diagnostic patient biopsies was discovered at M. D. Anderson Cancer Center (uncorrected ROC=0.97; corrected ROC=0.96). To translate that discovery to the clinical laboratory, a standardized protocol utilizing clinical grade reagents and instrumentation for biomarker detection has been developed. PathCR determination with this clinical procedure would be a significant step toward individualized therapeutic options for EC patients. Methods: OE33 and NCI−H460 cells were grown to confluence, collected, and fixed with PFA as a cell pellet. Fixed cell pellets were paraffin embedded, sectioned, and adhered to microscope slides. IHC detection of NF−kB, SHH, and Gli-1 proteins was performed in each cell line using clinical grade reagents and instrumentation, and protein localization was determined by microscopy to verify concordance with research laboratory techniques and results. Results: The clinical SOP allowed for efficient staining of each pathCR biomarker. Nuclear localization of activated NF-kB and Gli-1 was observed in OE33 and NCI-H460 cells, respectively, and SHH localization to the cytoplasm of NCI-H460 cells was also confirmed. The results correlate well with staining protocols utilized during research laboratory procedures. Conclusions: The clinical SOP for IHC detection of EC pathCR biomarkers can efficiently detect NF-kB, SHH, and Gli−1 in the control cell lines OE33 and NCI-H460. The protocols presented should be adaptable to EC patient tumor biopsies, providing an effective method for determining pathCR that will facilitate an individualized approach to treatment methods for people suffering from EC.