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Targeted cancer therapies have emerged as new treatment options for various cancer types. Among targets, receptor tyrosine kinases (RTKs) are among the most promising. ROR1 is a transmembrane RTK of importance during the normal embryogenesis for the central nervous system, heart, lung and skeletal systems, but is not expressed in normal adult tissues. However, ROR1 is overexpressed in several human malignancies and may act as a survival factor for tumor cells. Its unique expression by malignant cells may provide a target for novel therapeutics including monoclonal antibodies (mAbs) and small molecule inhibitors of tyrosine kinases (TKI) for the treatment of cancer. Promising preclinical results have been reported in e.g. chronic lymphocytic leukemia, pancreatic carcinoma, lung and breast cancer. ROR1 might also be an interesting oncofetal antigen for active immunotherapy. In this review, we provide an overview of the ROR1 structure and functions in cancer and highlight emerging therapeutic options of interest for targeting ROR1 in tumor therapy.

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.

Purpose: Erythropoietin (EPO) and EPO receptor (EPO-R) expression have been reported in solid tumors and are claimed to regulate tumor growth; however, no data have been published on this issue in B-cell malignancies or normal lymphoid cells. This report describes genomic/protein EPO-R expression and in vitro effects of recombinant human EPO (epoetin) in B-cell chronic lymphocytic leukemia (B-CLL), mantle-cell lymphoma (MCL), and multiple myeloma (MM).Experimental Design: Blood samples were obtained from patients with B-CLL, MCL, and healthy volunteers, and bone marrow was obtained from MM patients. EPO-R mRNA was detected by reverse transcription-PCR. EPO-R surface expression was investigated by flow cytometry using digoxigenin-labeled epoetin and polyclonal rabbit anti–EPO-R antibody for intracellular receptor. Tumor cell stimulation was determined in vitro using [3H]thymidine incorporation and CD69 expression after exposure to epoetin α or β or darbepoetin α.Results: EPO-R mRNA was detected in mononuclear cells from 32 of 41 (78%) B-CLL and 5 of 7 (71%) MCL patients, and 21 of 21 (100%) MM samples. Expression was also detected in highly purified T cells from six of eight B-CLL patients, four of four MM patients, and normal donor B and T cells. Surface EPO-R protein was not detected. Intracellular EPO-R staining with anti–EPO-R antibodies was unspecific. No tumor-stimulatory effect was observed with high epoetin concentrations.Conclusions: EPO-R gene is frequently expressed in lymphoid malignancies and normal B and T cells. However, there was no surface protein expression and no epoetin-induced in vitro stimulation of tumor B cells, indicating that epoetin therapy in vivo is likely to be safe in patients with lymphoid malignancies.

e13561 Background: There is a medical need to develop novel compounds for treatment of pancreatic carcinoma. Members of the TKR families are attractive therapeutic candidates. One of the families i...

Proline/arginine-rich end leucine-rich repeat protein (PRELP) belongs to the small leucine-rich proteoglycan (SLRP) family, normally expressed in extracellular matrix of collagen-rich tissues. We have previously reported on another SLRP, fibromodulin (FMOD) in patients with chronic lymphocytic leukemia (CLL). PRELP is structurally similar to FMOD with adjacent localization on chromosome 1 (1q32.1). As cluster-upregulation of genes may occur in malignancies, the aim of our study was to analyze PRELP expression in CLL. PRELP was expressed (RT-PCR) in all CLL patients (30/30), as well as in some patients with mantle cell lymphoma (3/5), but not in healthy donor leukocytes (0/20) or tumor samples from other hematological malignancies (0/35). PRELP was also detected in CLL cell-lines (4/4) but not in cell-lines from other hematological tumors (0/9). PRELP protein was detected in all CLL samples but not in normal leukocytes. Deglycosylation experiments revealed a CLL-unique 38 kDa core protein, with an intact signal peptide. This 38 kDa protein was, in contrast to the normal 55 kDa size, not detected in serum which, in combination with the uncleaved signal peptide, suggests cellular retention. The unique expression of a 38 kDa PRELP in CLL cells may suggest involvement in the pathobiology of CLL and merits further studies.

Background The biological effects of erythropoietin (EPO), the principal regulator of erythropoiesis, may extend to several non-hematopoietic tissues and cells. Recent studies suggest that EPO and erythropoietin receptors (EPO-R) may be expressed by solid tumors including breast, prostate, ovarian, and renal cancers. Studies also suggest that the EPO/EPO-R pathway might regulate survival and growth of cancer cells. Since recombinant human EPO (Epoetin) is frequently used to treat anemia in hematological malignancies, we studied the EPO-R expression as well as the in vitro effects of epoetin on tumor cells from patients with B-cell chronic lymphocytic leukemia (B-CLL), mantle cell lymphoma (MCL) and multiple myeloma (MM). Methods The genomic expression of EPO-R was analyzed in highly purified tumor cells by RT-PCR. Flow cytometry was applied to detect EPO-R protein expression on the cell surface (using EPO-dig + anti-dig FITC, F. Hoffmann-La Roche, Basel, Switzerland) and intracellularly (in permeabilized cells, using Santa Cruz polyclonal anti-EPO-R antibody). The functional capability of epoetin alfa, epoetin beta, and darbepoetin alfa to activate tumor cells in vitro (alone, and in combination with CD40L-transfected fibroblasts as co-stimulators) was assessed by proliferation assay (DNA synthesis) and by flow cytometry (CD69). Results EPO-R mRNA was detected in peripheral blood mononuclear cells in 32/41 (78%) B-CLL and 5/7 (71%) MCL patients. The positive results were confirmed in highly purified (>95%) tumor cells from 7 B-CLL patients. In MM patients, bone marrow mononuclear cells from 13/14 (93%) patients and highly purified (>98%) plasma cells from 3/3 (100%) patients were positive for EPO-R mRNA. However, surface EPO-R protein could not be detected in any of 9 tested B-CLL patients (5 of which were positive and 4 negative for EPO-R mRNA). In contrast, intracellular EPO-R protein was detected in 8/8 (100%) PCR-positive patients with B-CLL including 5 patients who had a negative surface EPO-R staining. Intracellular EPO-R protein was also found in 4/4 (100%) tested patients with MCL. CD69 expression and [3H]-thymidine incorporation were assessed in 8 patients with B-CLL and 4 patients with MCL after stimulation of tumor cells with epoetin. CD69 expression was not induced and no epoetin-induced proliferation was observed following in vitro stimulation with any of the 3 epoetin preparations. Conclusion The results indicate that EPO-R mRNA is expressed by tumor cells in most patients with B-CLL, MCL or MM. However, it is unclear whether the gene expression translates into a fully functional protein. EPO-R protein could be detected intracellularly in most samples but not on the cell surface (as assessed by different flow cytometry techniques). Furthermore, in vitro tumor cell stimulation even with high concentrations of epoetin did not induce proliferation/activation.

Background Opticin (OPTC) is a member of the small leucine-rich proteoglycan (SLRP) family and is localized particularly in certain extracellular matrices. We have previously reported the unique expression of another SLRP, fibromodulin (FMOD) in the leukemic cells of patients with chronic lymphocytic leukemia (CLL). OPTC is located in the same region as FMOD on chromosome 1 (1q32.1). Cluster up-regulation of genes may be observed in malignancies and the aim of the present study was to analyze the expression of OPTC in CLL cells. Methods The expression of OPTC was tested by RT-PCR and realtime qPCR in PBMC from CLL patients, other hematological malignancies and healthy controls. The presence of OPTC protein, and its subcellular localization, was investigated using fractionation methods where the obtained lysate fractions were analyzed by Western blotting. Deglycosylation experiments were performed to investigate the glycosylation status of the CLL OPTC. Results OPTC was expressed at the gene level in all patients with CLL (n = 90) and in 2/8 patients with mantle cell lymphoma (MCL) but not in blood mononuclear cells of healthy control donors (n = 20) or in tumor samples from nine other types of hematological malignancies. OPTC was detected by Western blot in all CLL samples analyzed (n = 30) but not in normal leukocytes (n = 10). Further analysis revealed a CLL-unique unglycosylated 37 kDa core protein that was found to be located preferentially in the cell nucleus and endoplasmic reticulum (ER) of the CLL cells. Conclusions A 37 kDa unglycosylated OPTC protein was detected in ER and in the nucleus of CLL cells and not in healthy control donors. The function of this OPTC core protein remains unclear but its CLL-specific expression and subcellular localization warrants further investigations in the pathobiology of CLL.