Gene profiling studies of patients with chronic lymphocytic leukemia (CLL) has revealed increased expression of Ror1, a cell surface receptor tyrosine kinase. The aim of present study was to analyze gene and protein expression of Ror1 in CLL cells and normal blood leukocytes. Gene expression analysis reverse transcriptionpolymerase chain reaction of ROR1 revealed that all patients with CLL (n 5 100) spontaneously expressed ROR1 mRNA whereas enriched blood B and T cells as well as granulocytes from healthy donors (n 5 10) were negative. A strong nonphysiological activation signal (PMA/ionomycin) was required to induce expression in vitro in normal lymphocytes. Major genomic aberrations (mutations or truncation) of ROR1 were not observed. Protein expression was analyzed by Western blot using a panel of polyclonal anti-Ror antibodies as well as flow cytometry. Blood lymphocytes from 18/18 CLL patients, but none of the 10 healthy donors, expressed surface Ror1. The majority of CLL cells exhibited Ror1 surface expression (71% mean; range 36-92%) with a mean fluorescence intensity (MFI) of 20 (range 10-45). The corresponding MFI of CD19 on CLL cells was 26 (range 9-48). There was no difference in the Ror1 protein expression comparing IgVH mutated and unmutated cases as well as progressive and nonprogressive CLL patients. Two different variants of the Ror1 protein, 105 and 130 kDa, were identified. The Ror1 protein expression in patients with CLL but not in normal leukocytes merits further studies of its role in the pathobiology of CLL, which may provide a basis for development of Ror1 directed targeted therapy. ' 2008 Wiley-Liss, Inc.
Key words: B-CLL; tyrosine kinase receptors; Ror1Chronic lymphocytic leukemia (CLL) originates from B lymphocytes, which differ in activation and maturation stage and are derived from antigen experienced B cells with different immunoglobulin heavy chain variable (IgVH) gene mutations. 1 Patients with mutated IgVH genes have a better prognosis compared to patients with unmutated genes. 2,3 Global gene expression profiling studies have revealed partly distinguishing but in general overlapping expression profiles in mutated and unmutated leukemic B cells, suggesting a common phenotype. 4,5 Gene expression profiling studies showed a 43.8-fold increase of the orphan receptor tyrosine kinase (RTK) ROR1 in CLL cells. 4 Ror1 is a member of the RTK family of orphan receptors related to muscle specific kinase and Trk neurotrophin receptors. [6][7][8] Ror receptors are cell surface receptors participating in signal transduction, cell-cell interaction, regulation of cell proliferation, differentiation, cell metabolism and survival. 7,9 They are evolutionarily highly conserved between different species e.g., human, mouse, Drosophila and C. elegans, suggesting important biological functions.The human ROR1 gene has a coding region of 2814 bp with a predicted 937 amino acids sequence and 105 kDa protein size including an Ig-like domain, cysteine-rich domain, kringle domain, tyrosine kinase domain and p...
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.