title: Calpain-mediated integrin deregulation as a novel mode of action for the anticancer gallium compound KP46.
abstract: On the basis of enhanced tumor accumulation and bone affinity, gallium compounds are under development as anticancer and antimetastatic agents. In this study, we analyzed molecular targets of one of the lead anticancer gallium complexes [KP46, Tris(8-quinolinolato)gallium(III)] focusing on colon and lung cancer. Within a few hours, KP46 treatment at low micromolar concentrations induced cell body contraction and loss of adhesion followed by prompt cell decomposition. This rapid KP46-induced cell death lacked classic apoptotic features and was insensitive toward a pan-caspase inhibitor. Surprisingly, however, it was accompanied by upregulation of proapoptotic Bcl-2 family members. Furthermore, a Bax- but not a p53-knockout HCT-116 subline exhibited significant KP46 resistance. Rapid KP46-induced detachment was accompanied by downregulation of focal adhesion proteins, including several integrin subunits. Loss of integrin-β1 and talin plasma membrane localization corresponded to reduced binding of RGD (Arg-Gly-Asp) peptides to KP46-treated cells. Accordingly, KP46-induced cell death and destabilization of integrins were enhanced by culture on collagen type I, a major integrin ligand. In contrast, KP46-mediated adhesion defects were partially rescued by Mg(2+) ions, promoting integrin-mediated cell adhesion. Focal adhesion dynamics are regulated by calpains via cleavage of multiple cell adhesion molecules. Cotreatment with the cell-permeable calpain inhibitor PD150606 diminished KP46-mediated integrin destabilization and rapid cell death induction. KP46 treatment distinctly inhibited HCT-116 colon cancer xenograft in vivo by causing reduced integrin plasma membrane localization, tissue disintegration, and intense tumor necrosis. This study identifies integrin deregulation via a calpain-mediated mechanism as a novel mode of action for the anticancer gallium compound KP46.
authors.affiliation: Department of Medicine I, Institute of Cancer Research and Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria.
authors.forename: Ute
authors.initials: U
authors.lastname: Jungwirth
authors.affiliation: Department of Medicine I, Institute of Cancer Research and Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Gojo
authors.affiliation: Department of Medicine I, Institute of Cancer Research and Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria.
authors.forename: Theresa
authors.initials: T
authors.lastname: Tuder
authors.affiliation: Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, Centre for Molecular Biology, University of Vienna, Vienna, Austria.
authors.forename: Gernot
authors.initials: G
authors.lastname: Walko
authors.affiliation: Department of Medicine I, Institute of Cancer Research and Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Holcmann
authors.affiliation: Department of Medicine I, Institute of Cancer Research and Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schöfl
authors.affiliation: Department of Internal Medicine I, Anna Spiegel Centre of Translational Research, Medical University Vienna, Vienna, Austria.
authors.forename: Karin
authors.initials: K
authors.lastname: Nowikovsky
authors.affiliation: Department of Internal Medicine I, Anna Spiegel Centre of Translational Research, Medical University Vienna, Vienna, Austria.
authors.forename: Nastasia
authors.initials: N
authors.lastname: Wilfinger
authors.affiliation: Department of Medicine I, Institute of Cancer Research and Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria.
authors.forename: Sushilla
authors.initials: S
authors.lastname: Schoonhoven
authors.affiliation: Institute of Inorganic Chemistry and Research Platform "Translational Cancer Therapy Research," University of Vienna, Vienna, Austria.
authors.forename: Christian R
authors.initials: CR
authors.lastname: Kowol
authors.affiliation: Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria.
authors.forename: Rosa
authors.initials: R
authors.lastname: Lemmens-Gruber
authors.affiliation: Department of Medicine I, Institute of Cancer Research and Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria. Institute of Inorganic Chemistry and Research Platform "Translational Cancer Therapy Research," University of Vienna, Vienna, Austria.
authors.forename: Petra
authors.initials: P
authors.lastname: Heffeter
authors.affiliation: Institute of Inorganic Chemistry and Research Platform "Translational Cancer Therapy Research," University of Vienna, Vienna, Austria.
authors.forename: Bernhard K
authors.initials: BK
authors.lastname: Keppler
authors.affiliation: Department of Medicine I, Institute of Cancer Research and Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria. Institute of Inorganic Chemistry and Research Platform "Translational Cancer Therapy Research," University of Vienna, Vienna, Austria. walter.berger@meduniwien.ac.at.
authors.forename: Walter
authors.initials: W
authors.lastname: Berger
mesh_terms: D000818:Animals; D018938:Caco-2 Cells; D002154:Calpain / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D009942:Organometallic Compounds / Q000494:pharmacology*; D015125:Oxyquinoline / Q000031:analogs & derivatives* / Q000494:pharmacology; D011897:Random Allocation; D023041:Xenograft Model Antitumor Assays
chemical_list: D016023:Integrins; D009942:Organometallic Compounds; C408502:tris(8-quinolinolato)gallium (III); D015125:Oxyquinoline; D002154:Calpain