title: Resistance to the mTOR inhibitor temsirolimus alters adhesion and migration behavior of renal cell carcinoma cells through an integrin α5- and integrin β3-dependent mechanism.
abstract: Inhibitors of the mammalian target of rapamycin (mTOR) have improved the treatment of renal cell carcinoma (RCC). However, chronic drug exposure may trigger resistance, limiting the utility of these agents. The metastatic behavior of RCC cells, susceptible (RCC(par)) or resistant (RCC(res)) to the mTOR inhibitor temsirolimus, was investigated. Adhesion to vascular endothelium or immobilized collagen and fibronectin was quantified. Chemotactic motility was evaluated with a modified Boyden chamber assay. Integrin α and β subtype receptors were analyzed by flow cytometry and Western blot analysis. The physiological relevance of the integrins was then determined by blocking studies and small interfering RNA knockdown. Adhesion to endothelial cells and to fibronectin (not to collagen) and chemotaxis were enhanced in RCC(res) compared to RCC(par). RCC(res) detached from fibronectin and motile activity further increased under retreatment with low-dosed temsirolimus. α5 integrin was diminished inside the cell and at the cell surface, whereas the β3 subtype was reduced intracellularly but elevated at the plasma membrane. In RCC(par), blocking α5 surface receptors enhanced RCC-collagen but reduced RCC-fibronectin interaction, whereas the opposite was true for RCC(res). Chemotaxis of RCC(par) but not of RCC(res) was strongly diminished by the α5 antibody. Blocking β3 significantly lowered chemotaxis with stronger effects on RCC(res), compared to RCC(par). Importantly, β3 knockdown reduced chemotaxis of RCC(par) but upregulated the motile behavior of RCC(res). Temsirolimus resistance is characterized by quantitative alterations of integrin α5 and β3 expression, coupled to functional changes of the integrin molecules, and forces a switch from RCC adhesion to RCC migration.
authors.affiliation: Department of Urology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Juengel
authors.affiliation: Department of Urology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.
authors.forename: Jasmina
authors.initials: J
authors.lastname: Makarević
authors.affiliation: Department of Urology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Reiter
authors.affiliation: Department of Urology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Mani
authors.affiliation: Department of Urology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.
authors.forename: Igor
authors.initials: I
authors.lastname: Tsaur
authors.affiliation: Department of Urology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Bartsch
authors.affiliation: Department of Urology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Haferkamp
authors.affiliation: Department of Urology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. Electronic address: Blaheta@em.uni-frankfurt.de.
authors.forename: Roman A
authors.initials: RA
authors.lastname: Blaheta
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002292:Carcinoma, Renal Cell / Q000378:metabolism* / Q000473:pathology; D002448:Cell Adhesion / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics; D019008:Drug Resistance, Neoplasm; D055785:Gene Knockdown Techniques; D006801:Humans; D039482:Integrin alpha5 / Q000235:genetics / Q000378:metabolism*; D039661:Integrin beta3 / Q000235:genetics / Q000378:metabolism*; D007680:Kidney Neoplasms / Q000378:metabolism* / Q000473:pathology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors
chemical_list: D000970:Antineoplastic Agents; D039482:Integrin alpha5; D039661:Integrin beta3; D047428:Protein Kinase Inhibitors; C401859:temsirolimus; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus