title: Inhibition of the receptor tyrosine kinase ROR1 by anti-ROR1 monoclonal antibodies and siRNA induced apoptosis of melanoma cells.
abstract: The receptor tyrosine kinase (RTK) ROR1 is overexpressed and of importance for the survival of various malignancies, including lung adenocarcinoma, breast cancer and chronic lymphocytic leukemia (CLL). There is limited information however on ROR1 in melanoma. In the present study we analysed in seven melanoma cell lines ROR1 expression and phosphorylation as well as the effects of anti-ROR1 monoclonal antibodies (mAbs) and ROR1 suppressing siRNA on cell survival. ROR1 was overexpressed at the protein level to a varying degree and phosphorylated at tyrosine and serine residues. Three of our four self-produced anti-ROR1 mAbs (clones 3H9, 5F1 and 1A8) induced a significant direct apoptosis of the ESTDAB049, ESTDAB112, DFW and A375 cell lines as well as cell death in complement dependent cytotoxicity (CDC) and antibody dependent cellular cytotoxicity (ADCC). The ESTDAB081 and 094 cell lines respectively were resistant to direct apoptosis of the four anti-ROR1 mAbs alone but not in CDC or ADCC. ROR1 siRNA transfection induced downregulation of ROR1 expression both at mRNA and protein levels proceeded by apoptosis of the melanoma cells (ESTDAB049, ESTDAB112, DFW and A375) including ESTDAB081, which was resistant to the direct apoptotic effect of the mAbs. The results indicate that ROR1 may play a role in the survival of melanoma cells. The surface expression of ROR1 on melanoma cells may support the notion that ROR1 might be a suitable target for mAb therapy.
authors.affiliation: Department of Oncology-Pathology, Immune and Gene therapy Lab, Cancer Center Karolinska, Karolinska University Hospital Solna and Karolinska Institute, Stockholm, Sweden.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Hojjat-Farsangi
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Ghaemimanesh
authors.forename: Amir Hossein
authors.initials: AH
authors.lastname: Daneshmanesh
authors.forename: Ali-Ahmad
authors.initials: AA
authors.lastname: Bayat
authors.forename: Jafar
authors.initials: J
authors.lastname: Mahmoudian
authors.forename: Mahmood
authors.initials: M
authors.lastname: Jeddi-Tehrani
authors.forename: Hodjatallah
authors.initials: H
authors.lastname: Rabbani
authors.forename: Hakan
authors.initials: H
authors.lastname: Mellstedt
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D017209:Apoptosis / Q000235:genetics* / Q000276:immunology*; D001483:Base Sequence; D045744:Cell Line, Tumor; D003165:Complement System Proteins / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics / Q000276:immunology; D006801:Humans; D008545:Melanoma / Q000473:pathology*; D010766:Phosphorylation / Q000235:genetics / Q000276:immunology; D034741:RNA, Small Interfering / Q000235:genetics*; D057050:Receptor Tyrosine Kinase-like Orphan Receptors / Q000172:deficiency / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D034741:RNA, Small Interfering; D003165:Complement System Proteins; C078716:ROR1 protein, human; D057050:Receptor Tyrosine Kinase-like Orphan Receptors