title: Epidermal growth factor receptor endocytic traffic perturbation by phosphatidate phosphohydrolase inhibition: new strategy against cancer.
abstract: Epidermal growth factor receptor (EGFR) exaggerated (oncogenic) function is currently targeted in cancer treatment with drugs that block receptor ligand binding or tyrosine kinase activity. Because endocytic trafficking is a crucial regulator of EGFR function, its pharmacological perturbation might provide a new anti-tumoral strategy. Inhibition of phosphatidic acid (PA) phosphohydrolase (PAP) activity has been shown to trigger PA signaling towards type 4 phosphodiesterase (PDE4) activation and protein kinase A inhibition, leading to internalization of empty/inactive EGFR. Here, we used propranolol, its l- and d- isomers and desipramine as PAP inhibitors to further explore the effects of PAP inhibition on EGFR endocytic trafficking and its consequences on EGFR-dependent cancer cell line models. PAP inhibition not only made EGFR inaccessible to stimuli but also prolonged the signaling lifetime of ligand-activated EGFR in recycling endosomes. Strikingly, such endocytic perturbations applied in acute/intermittent PAP inhibitor treatments selectively impaired cell proliferation/viability sustained by an exaggerated EGFR function. Phospholipase D inhibition with FIPI (5-fluoro-2-indolyl des-chlorohalopemide) and PDE4 inhibition with rolipram abrogated both the anti-tumoral and endocytic effects of PAP inhibition. Prolonged treatments with a low concentration of PAP inhibitors, although without detectable endocytic effects, still counteracted cell proliferation, induced apoptosis and decreased anchorage-independent growth of cells bearing EGFR oncogenic influences. Overall, our results show that PAP inhibitors can counteract EGFR oncogenic traits, including receptor overexpression or activating mutations resistant to current tyrosine kinase inhibitors, perturbing EGFR endocytic trafficking and perhaps other as yet unknown processes, depending on treatment conditions. This puts PAP activity forward as a new suitable target against EGFR-driven malignancy.
authors.affiliation: Departamento de Inmunología Clínica y Reumatología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile; Centro de Envejecimiento y Regeneración, Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Ronan
authors.initials: R
authors.lastname: Shaughnessy
authors.forename: Claudio
authors.initials: C
authors.lastname: Retamal
authors.forename: Claudia
authors.initials: C
authors.lastname: Oyanadel
authors.forename: Andrés
authors.initials: A
authors.lastname: Norambuena
authors.forename: Alejandro
authors.initials: A
authors.lastname: López
authors.forename: Marcela
authors.initials: M
authors.lastname: Bravo-Zehnder
authors.forename: Fabian J
authors.initials: FJ
authors.lastname: Montecino
authors.forename: Claudia
authors.initials: C
authors.lastname: Metz
authors.forename: Andrea
authors.initials: A
authors.lastname: Soza
authors.forename: Alfonso
authors.initials: A
authors.lastname: González
mesh_terms: D003891:Desipramine / Q000494:pharmacology; D004705:Endocytosis; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D066246:ErbB Receptors / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D009369:Neoplasms / Q000188:drug therapy*; D010711:Phosphatidate Phosphatase / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D011433:Propranolol / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D008024:Ligands; D011433:Propranolol; D066246:ErbB Receptors; D010711:Phosphatidate Phosphatase; D003891:Desipramine
keywords: EGFR; apoptosis; cancer; endocytosis; phosphatidic acid