Overexpression of orphan receptor tyrosine kinase Ror1 as a putative tumor-associated antigen in Iranian patients with acute lymphoblastic leukemia

Receptor tyrosine kinases (RTKs) are a group of enzymes involved in a variety of physiological and pathological processes. The human Ror1 is a member of the RTK family with unknown ligand and biological function. Overexpression of Ror1 has recently been reported in B-cell chronic lymphocytic leukemia. The aim of this study was to explore the expression profile of Ror1 in acute lymphoblastic leukemia (ALL) cells. Therefore, leukemic cells were isolated from the bone marrow and/or peripheral blood (PB) of 57 ALL patients. Immunophenotyping was performed by flow cytometry and mRNA expression was detected by RT-PCR. Overexpression of Ror1 mRNA was detected in 23 of 57 (40) ALL patients. A similar expression pattern was observed in ALL cell lines, with 4 of 12 (33) being positive. Stimulation of normal PB mononuclear cells with pokeweed mitogen and phorbol myristate acetate induced substantially higher Ror1 mRNA expression compared to unstimulated cultured cells. There has been neither a significant association between Ror1 expression and the immunophenotypic profile of the leukemic cells, nor with other clinical or hematological features of the patients. In conclusion, our findings propose Ror1 as a new tumor-associated antigen and a potential tool for targeted immunotherapy and monitoring of minimal residual disease in ALL. Copyright © 2008 S. Karger AG

Comparative expression profile of orphan receptor tyrosine kinase ROR1 in iranian patients with lymphoid and myeloid leukemias

It has recently been shown that ROR1, a member of the receptor tyrosine kinase family, is overexpressed in leukemic B cells of Chronic Lymphocytic Leukemia (CLL) and a subset of Acute Lymphoblastic Leukemia (ALL). In this comparative study the expression profile of ROR1 mRNA was investigated in Iranian patients with CLL and Acute Myelogenous Leukemia (AML) and the results were compared with those previously reported in our Iranian ALLpatients. RT-PCR was performed on bone marrow and/or peripheral blood samples of 84 CLL and 12 AML patients. CLL samples were classified into immunoglobulin heavy chain variable region (IGHV) gene mutated (n=55) and unmutated (n=29) and also indolent (n=42) and progressive (n=39) subtypes. ROR1 expression was identified in 94 of our CLL patients, but none of the AML patients expressed ROR1. No significant differences were observed between different CLL subtypes for ROR1 expression. Taken together the present data and our previous results on ROR1 expression in ALL, our findings propose ROR1 as a tumor-associated antigen overexpressed in a large proportion of lymphoid (CLL and ALL), but not myeloid (AML) leukemias. Expression of ROR1 seems to be associated to lineage and differentiation stages of leukemic cells with a potential implication for immunotherapy. © 2011, Avicenna Journal of Medical Biotechnology. All rights reserved