A Novel NHE1-Centered Signaling Cassette Drives Epidermal Growth Factor Receptor–Dependent Pancreatic Tumor Metastasis and Is a Target for Combination Therapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers principally because of early invasion and metastasis. The epidermal growth factor receptor (EGFR) is essential for PDAC development even in the presence of Kras, but its inhibition with erlotinib gives only a modest clinical response, making the discovery of novel EGFR targets of critical interest. Here, we revealed by mining a human pancreatic gene expression database that the metastasis promoter Na+/H+ exchanger (NHE1) associates with the EGFR in PDAC. In human PDAC cell lines, we confirmed that NHE1 drives both basal and EGF-stimulated three-dimensional growth and early invasion via invadopodial extracellular matrix digestion. EGF promoted the complexing of EGFR with NHE1 via the scaffolding protein Na +/H + exchanger regulatory factor 1, engaging EGFR in a negative transregulatory loop that controls the extent and duration of EGFR oncogenic signaling and stimulates NHE1. The specificity of NHE1 for growth or invasion depends on the segregation of the transient EGFR/Na +/H + exchanger regulatory factor 1/NHE1 signaling complex into dimeric subcomplexes in different lipid raftlike membrane domains. This signaling complex was also found in tumors developed in orthotopic mice. Importantly, the specific NHE1 inhibitor cariporide reduced both three-dimensional growth and invasion independently of PDAC subtype and synergistically sensitized these behaviors to low doses of erlotinib

HPV16 E7-Dependent Transformation Activates NHE1 through a PKA-RhoA-Iinduced Inhibition of p38alpha

Background: Neoplastic transformation originates from a large number of different genetic alterations. Despite this genetic variability, a common phenotype to transformed cells is cellular alkalinization. We have previously shown in human keratinocytes and a cell line in which transformation can be turned on and followed by the inducible expression of the E7 oncogene of human papillomavirus type 16 (HPV16), that intracellular alkalinization is an early and essential physiological event driven by the up-regulation of the Na/H-+(+) exchanger isoform 1 (NHE1) and is necessary for the development of other transformed phenotypes and the in vivo tumor formation in nude mice.Methodology: Here, we utilize these model systems to elucidate the dynamic sequence of alterations of the upstream signal transduction systems leading to the transformation-dependent activation of NHE1.Principal Findings: We observe that a down-regulation of p38 MAPK activity is a fundamental step in the ability of the oncogene to transform the cell. Further, using pharmacological agents and transient transfections with dominant interfering, constitutively active, phosphorylation negative mutants and siRNA strategy to modify specific upstream signal transduction components that link HPV16 E7 oncogenic signals to up-regulation of the NHE1, we demonstrate that the stimulation of NHE1 activity is driven by an early rise in cellular cAMP resulting in the down-stream inhibition of p38 MAPK via the PKA-dependent phosphorylation of the small G-protein, RhoA, and its subsequent inhibition.Conclusions: All together these data significantly improve our knowledge concerning the basic cellular alterations involved in oncogene-driven neoplastic transformation

[Atypical mycobacterial infection after kidney transplant: two clinical cases]

Infections are an important cause of morbidity and mortality during kidney transplant. In areas where tuberculosis is not endemic, Mycobacteria other than tuberculosis (MOOT), also known as 'atypical' Mycobacteria, are more frequently involved in mycobacterial infections than M. tuberculosis. The incidence of MOOT infection in renal transplant recipients ranges from 0.16 to 0.38 percent. This low rate of reported incidence is, however, often due to delay in diagnosis and lack of therapeutic protocols. Further difficulty is caused by the interaction of antimycobacterial drugs with the post-transplant immunosuppressive regimen, necessitating close monitoring of plasma concentrations and careful dose modification. We present two cases of Mycobacterium Chelonae infection in kidney transplant recipients which differ in both clinical presentation and pharmacological approach

NHERF1 expression levels in blood and tissue predict breast tumor clinical behaviour

International audienceAims: Several studies have demonstrated that NHERF1 protein, over-expressed and heterogeneously distributed in different stages of breast cancer, could be used as a tumor marker for prognosis in molecular detection strategies. We observed tumor infiltrated lymphocytes in the tumour tissue displaying a high NHERF1 staining in contrast with those present in the contiguous non involved tissue. Hypothesizing that cancer cells elicit a specific T cell response associated with the characteristics of the solid tumor, we evaluated NHERF1 in peripheral lymphocytes from healthy donors and breast cancer patients. Method and results: NHERF1 levels were analyzed in 55 breast cancer patients and 40 healthy and compared with clinical pathological features. The level of NHERF1 was over-expressed in circulatory peripheral lymphocytes from patients compared to those from healthy subjects. Indeed in both circulatory lymphocytes and tissues, NHERF1 was positively associated with grade, Nottingham Prognostic Index and estrogen receptor of the tumors, while there was no association with other clinical parameters in either tissue. Conclusions: We propose that NHERF1 measurements in circulatory lymphocytes of breast cancer patients may be a valid method to predict breast cancer occurrence and prognosis and have value in the management of cancer patients

Protein Kinase A Gating of a Pseudopodial-located RhoA/ROCK/p38/NHE1 Signal Module Regulates Invasion in Breast Cancer Cell Lines

Metastasis results from a sequence of selective events often involving interactions with elements of the tumor-specific physiological microenvironment. The low-serum component of this microenvironment confers increased motility and invasion in breast cancer cells by activating the Na(+)/H(+) exchanger isoform 1 (NHE1). The present study was undertaken to characterize the signal transduction mechanisms underlying this serum deprivation-dependent activation of both the NHE1 and the concomitant invasive characteristics such as leading edge pseudopodia development and penetration of matrigel in breast cancer cell lines representing different stages of metastatic progression. Using pharmacological and genetic manipulation together with transport and kinase activity assays, we observe that the activation of the NHE1 and subsequent invasion by serum deprivation in metastatic human breast cells is coordinated by a sequential RhoA/p160ROCK/p38MAPK signaling pathway gated by direct protein kinase A phosphorylation and inhibition of RhoA. Fluorescence resonance energy transfer imaging of RhoA activity and immunofluorescence analysis of phospho-RhoA and NHE1 show that serum deprivation dynamically remodels the cell, forming long, leading edge pseudopodia and that this signal module is preferentially compartmentalized in these leading edge pseudopodia, suggesting a tight topographic relation of the signaling module to an invasion-specific cell structure

The NHERF1 PDZ2 Domain Regulates PKA–RhoA–p38-mediated NHE1 Activation and Invasion in Breast Tumor Cells

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