title: Anticancer Effects of Mesothelin-Targeted Immunotoxin Therapy Are Regulated by Tyrosine Kinase DDR1.
abstract: Recombinant immunotoxins (RIT) have been highly successful in cancer therapy due, in part, to the high cancer-specific expression of cell surface antigens such as mesothelin, which is overexpressed in mesothelioma, ovarian, lung, breast, and pancreatic cancers, but is limited in normal cells. RG7787 is a clinically optimized RIT consisting of a humanized anti-mesothelin Fab fused to domain III of Pseudomonas exotoxin A, in which immunogenic B-cell epitopes are silenced. To enhance the therapeutic efficacy of RITs, we conducted a kinome RNAi sensitization screen, which identified discoidin domain receptor 1 (DDR1), a collagen-activated tyrosine kinase, as a potential target. The collagen/DDR1 axis is implicated in tumor-stromal interactions and potentially affects tumor response to therapy. Therefore, we investigated the effects of DDR1 on RIT. Knockdown of DDR1 by siRNA or treatment with inhibitor, 7rh, greatly enhanced the cytotoxic activity of RG7787 in several cancer cell lines. Investigation into the mechanism of action showed DDR1 silencing was associated with decreased expression of several ribosomal proteins and enhanced inhibition of protein synthesis. Conversely, induction of DDR1 expression or collagen-stimulated DDR1 activity protected cancer cells from RG7787 killing. Moreover, the combination of RG7787 and DDR1 inhibitor caused greater shrinkage of tumor xenografts than either agent alone. These data demonstrate that DDR1 is a key modulator of RIT activity and represents a novel therapeutic strategy to improve targeting of mesothelin-expressing cancers.
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, NCI, Bethesda, Maryland.
authors.forename: Fatima
authors.initials: F
authors.lastname: Ali-Rahmani
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, NCI, Bethesda, Maryland.
authors.forename: David J
authors.initials: DJ
authors.lastname: FitzGerald
authors.affiliation: National Center for Advancing Translational Sciences, NIH, Rockville, Maryland.
authors.forename: Scott
authors.initials: S
authors.lastname: Martin
authors.affiliation: National Center for Advancing Translational Sciences, NIH, Rockville, Maryland.
authors.forename: Paresma
authors.initials: P
authors.lastname: Patel
authors.affiliation: Discovery Technologies, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Prunotto
authors.affiliation: National Center for Advancing Translational Sciences, NIH, Rockville, Maryland.
authors.forename: Pinar
authors.initials: P
authors.lastname: Ormanoglu
authors.affiliation: National Center for Advancing Translational Sciences, NIH, Rockville, Maryland.
authors.forename: Craig
authors.initials: C
authors.lastname: Thomas
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, NCI, Bethesda, Maryland. pastani@mail.nih.gov.
authors.forename: Ira
authors.initials: I
authors.lastname: Pastan
mesh_terms: D036002:ADP Ribose Transferases / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000494:pharmacology; D045744:Cell Line, Tumor; D000070819:Discoidin Domain Receptor 1; D005098:Exotoxins / Q000494:pharmacology; D058851:GPI-Linked Proteins / Q000378:metabolism*; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D018796:Immunoconjugates / Q000494:pharmacology; D000922:Immunotoxins / Q000494:pharmacology*; D000090204:Mesothelin; D051379:Mice; D008819:Mice, Nude; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D037521:Virulence Factors / Q000494:pharmacology; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D000970:Antineoplastic Agents; D001427:Bacterial Toxins; D000070819:Discoidin Domain Receptor 1; D005098:Exotoxins; D058851:GPI-Linked Proteins; D018796:Immunoconjugates; D000922:Immunotoxins; D000090204:Mesothelin; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C000715528:Msln protein, mouse; C000597116:LMB-100; C092030:DDR1 protein, human