Expression profile of orphan receptor tyrosine kinase (ROR1) and Wilms' tumor gene 1 (WT1) in different subsets of B-cell acute lymphoblastic leukemia

T cell-redirecting therapies in hematological malignancies: Current developments and novel strategies for improved targeting

T cell-redirecting therapies (TCRTs), such as chimeric antigen receptor (CAR) or T cell receptor (TCR) T cells and T cell engagers, have emerged as a highly effective treatment modality, particularly in the B and plasma cell-malignancy setting. However, many patients fail to achieve deep and durable responses; while the lack of truly unique tumor antigens, and concurrent on-target/off-tumor toxicities, have hindered the development of TCRTs for many other cancers. In this review, we discuss the recent developments in TCRT targets for hematological malignancies, as well as novel targeting strategies that aim to address these, and other, challenges.

A ROR1 Small Molecule Inhibitor (KAN0441571C) Induced Significant Apoptosis of Mantle Cell Lymphoma (MCL) Cells

The receptor tyrosine kinase orphan receptor 1 (ROR1) is absent in most normal adult tissues but overexpressed in various malignancies and is of importance for tumor cell survival, proliferation, and metastasis. In this study, we evaluated the apoptotic effects of a novel small molecule inhibitor of ROR1 (KAN0441571C) as well as venetoclax (BCL-2 inhibitor), bendamustine, idelalisib (PI3Kδ inhibitor), everolimus (mTOR inhibitor), and ibrutinib (BTK inhibitor) alone or in combination in human MCL primary cells and cell lines. ROR1 expression was evaluated by flow cytometry and Western blot (WB). Cytotoxicity was analyzed by MTT and apoptosis by Annexin V/PI staining as well as signaling and apoptotic proteins (WB). ROR1 was expressed both in patient-derived MCL cells and human MCL cell lines. KAN0441571C alone induced significant time- and dose-dependent apoptosis of MCL cells. Apoptosis was accompanied by decreased expression of MCL-1 and BCL-2 and cleavage of PARP and caspase 3. ROR1 was dephosphorylated as well as ROR1-associated signaling pathway molecules, including the non-canonical WNT signaling pathway (PI3Kδ/AKT/mTOR). The combination of KAN0441571C and ibrutinib, venetoclax, idelalisib, everolimus, or bendamustine had a synergistic apoptotic effect and significantly prevented phosphorylation of ROR1-associated signaling molecules as compared to KAN0441571C alone. Our results suggest that targeting ROR1 by a small molecule inhibitor, KAN0441571C, should be further evaluated particularly in combination with other targeting drugs as a new therapeutic approach for MCL.

The ROR1 antibody-drug conjugate huXBR1-402-G5-PNU effectively targets ROR1+ leukemia

Antibody-drug conjugates directed against tumor-specific targets have allowed targeted delivery of highly potent chemotherapy to malignant cells while sparing normal cells. Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal protein with limited expression on normal adult tissues and is overexpressed on the surface of malignant cells in mantle cell lymphoma, acute lymphocytic leukemia with t(1;19)(q23;p13) translocation, and chronic lymphocytic leukemia. This differential expression makes ROR1 an attractive target for antibody-drug conjugate therapy, especially in malignancies such as mantle cell lymphoma and acute lymphocytic leukemia, in which systemic chemotherapy remains the gold standard. Several preclinical and phase 1 clinical studies have established the safety and effectiveness of anti-ROR1 monoclonal antibody-based therapies. Herein we describe a humanized, first-in-class anti-ROR1 antibody-drug conjugate, huXBR1-402-G5-PNU, which links a novel anti-ROR1 antibody (huXBR1-402) to a highly potent anthracycline derivative (PNU). We found that huXBR1-402-G5-PNU is cytotoxic to proliferating ROR1+ malignant cells in vitro and suppressed leukemia proliferation and extended survival in multiple models of mice engrafted with human ROR1+ leukemia. Lastly, we show that the B-cell lymphoma 2 (BCL2)-dependent cytotoxicity of huXBR1-402-G5-PNU can be leveraged by combined treatment strategies with the BCL2 inhibitor venetoclax. Together, our data present compelling preclinical evidence for the efficacy of huXBR1-402-G5-PNU in treating ROR1+ hematologic malignancies.

Targeting the Receptor Tyrosine Kinase ROR1 by Small Molecules

Receptor tyrosine kinases (RTKs) are frequently dysregulated in malignancies and important for the malignant characteristics of tumor cells. RTKs are attractive structures for drug targeting of cancer. The RTK ROR1 is of significance during embryogenesis but downregulated in post-partum tissues. However, ROR1 is overexpressed in several hematological and solid tumors and important for tumor cell proliferation, survival, migration, and metastasis. WNT5a is a main ligand for ROR1. Several clinical trials are ongoing using anti-ROR1 antibody based drugs directed against the external domain (monoclonal antibodies, BiTE, CAR-T). We have produced small molecules (KAN834/1571c) fitting to the ATP pocket of the intracellular tyrosine kinase (TK) domain of ROR1 (TK inhibitor, TKI). These inhibitors of ROR1 prevented ROR1 phosphorylation and inactivated the WNT/β-catenin independent as well as WNT/β-catenin dependent pathways. ROR1-TKI induced apoptosis of ROR1 positive fresh patient derived tumor cells and appropriate cell lines and a dose and time dependent tumor reduction in animal models. In combination with other clinically relevant targeting drugs as venetoclax a synergistic apoptotic effect was seen. Two other small molecules (ARI-1 and strictinin) bound also to ROR1 and inhibited tumor growth. Development of small molecule ROR1 inhibitors is warranted to include this novel therapeutic approach for cancer therapy.

Genetics of blood malignancies among Iranian population: an overview

BACKGROUND

Blood malignancies are among the leading causes of cancer related deaths in the world. Different environmental and genetic risk factors are involved in progression of blood malignancies. It has been shown that the lifestyle changes have affected the epidemiological patterns of these malignancies. Hematologic cancers are the 5th common cancer among Iranian population. It has been observed that there is a rising trend of blood malignancies incidences during the recent decades. Therefore, it is required to design novel diagnostic methods for the early detection of such malignancies in this population.

MAIN BODY

In present review we have summarized all of the significant genes which have been reported among Iranian patients with blood malignancies. The reported genes were categorized based on their cell and molecular functions to clarify the molecular biology and genetics of blood malignancies among Iranian patients.

CONCLUSION

It was observed that the epigenetic and immune response factors were the most frequent molecular processes associated with progression of blood malignancies among Iranian population. This review paves the way of introducing a population based panel of genetic markers for the early detection of blood malignancies in this population.

Locating potentially lethal genes using the abnormal distributions of genotypes

Genes are the basic functional units of heredity. Differences in genes can lead to various congenital physical conditions. One kind of these differences is caused by genetic variations named single nucleotide polymorphisms (SNPs). An SNP is a variation in a single nucleotide that occurs at a specific position in the genome. Some SNPs can affect splice sites and protein structures and cause gene abnormalities. SNPs on paired chromosomes may lead to fatal diseases so that a fertilized embryo cannot develop into a normal fetus or the people born with these abnormalities die in childhood. The distributions of genotypes on these SNP sites are different from those on other sites. Based on this idea, we present a novel statistical method to detect the abnormal distributions of genotypes and locate the potentially lethal genes. The test was performed on HapMap data and 74 suspicious SNPs were found. Ten SNP maps “reviewed” genes in the NCBI database. Among them, 5 genes were related to fatal childhood diseases or embryonic development, 1 gene can cause spermatogenic failure, and the other 4 genes were associated with many genetic diseases. The results validated our method. The method is very simple and is guaranteed by a statistical test. It is an inexpensive way to discover potentially lethal genes and the mutation sites. The mined genes deserve further study.

ROR1 associates unfavorable prognosis and promotes lymphoma growth in DLBCL by affecting PI3K/Akt/mTOR signaling pathway

The receptor-tyrosine-kinase (RTK)-like orphan receptor 1 (ROR1) is a transmembrane glycoprotein regarded as a tumor-associated antigen. ROR1 plays an important role in cancer development, but the detailed function of ROR1 in diffuse large B-cell lymphoma (DLBCL) remains unclear. In this study, we first detected ROR1 expression and evaluated the relationship between ROR1 expression and the clinicopathological characteristics of DLBCL patients. Next we employed shRNA-mediated knockdown of ROR1 in DLBCL cell line to explore the characteristics of ROR1 in DLBCL development both in vitro and in vivo. The results showed a significantly higher level of ROR1 in DLBCL tissues than in lymphatic hyperplasia tissues. High ROR1 expression was correlated with unfavorable prognosis in DLBCL patients. Furthermore, ROR1 knockdown inhibited the growth and induced the apoptosis in DLBCL cells and xenografts. In addition, shROR1 inhibited activation of the PI3K/Akt/mTOR signaling pathway, both in vitro and in vivo. Taken together, our results suggest that ROR1 is a novel prognostic marker for DLBCL survival and ROR1 significantly promotes DLBCL tumorigenesis by regulating the PI3K/Akt/mTOR signaling pathway. Targeting ROR1 may provide a promising strategy for DLBCL treatment. © 2019 BioFactors, 45(3):416-426, 2019.

Maintenance and pharmacologic targeting of ROR1 protein levels via UHRF1 in t(1;19) pre-B-ALL

Expression of the transmembrane pseudokinase ROR1 is required for survival of t(1;19)-pre-B-cell acute lymphoblastic leukemia (t(1;19) pre-B-ALL), chronic lymphocytic leukemia, and many solid tumors. However, targeting ROR1 with small-molecules has been challenging due to the absence of ROR1 kinase activity. To identify genes that regulate ROR1 expression and may, therefore, serve as surrogate drug targets, we employed an siRNA screening approach and determined that the epigenetic regulator and E3 ubiquitin ligase, UHRF1, is required for t(1;19) pre-B-ALL cell viability in a ROR1-dependent manner. Upon UHRF1 silencing, ROR1 protein is reduced without altering ROR1 mRNA, and ectopically expressed UHRF1 is sufficient to increase ROR1 levels. Additionally, proteasome inhibition rescues loss of ROR1 protein after UHRF1 silencing, suggesting a role for the proteasome in the UHRF1-ROR1 axis. Finally, we show that ROR1-positive cells are twice as sensitive to the UHRF1-targeting drug, naphthazarin, and undergo increased apoptosis compared to ROR1-negative cells. Naphthazarin elicits reduced expression of UHRF1 and ROR1, and combination of naphthazarin with inhibitors of pre-B cell receptor signaling results in further reduction of cell survival compared with either inhibitor alone. Therefore, our work reveals a mechanism by which UHRF1 stabilizes ROR1, suggesting a potential targeting strategy to inhibit ROR1 in t(1;19) pre-B-ALL and other malignancies.

Antiproliferative and Apoptotic Effects of Novel Anti-ROR1 Single-Chain Antibodies in Hematological Malignancies

Receptor tyrosine kinase-like orphan receptor (ROR) proteins are a conserved family of tyrosine kinase receptors that function in developmental processes including cell survival, differentiation, cell migration, cell communication, cell polarity, proliferation, metabolism, and angiogenesis. ROR1 has recently been shown to be expressed in various types of cancer cells but not normal cells. Pharmacokinetics and pharmacodynamics of single-chain Fragment variable (scFv) antibodies provide potential therapeutic advantages over whole antibody molecules. In the present study, scFvs against a specific peptide from the extracellular domain of ROR1 were selected using phage display technology. The selected scFvs were further characterized using polyclonal and monoclonal phage enzyme-linked immunosorbent assay (ELISA), soluble monoclonal ELISA, colony PCR, and sequencing. Antiproliferative and apoptotic effects of selected scFv antibodies were also evaluated in lymphoma and myeloma cancer cell lines using MTT and annexin V/PI assays. The results of ELISA indicated specific reactions of the isolated scFvs against the ROR1 peptide. Colony PCR confirmed the presence of full-length V_H and Vκ inserts. The percentages of cell growth after 24 h of treatment of cells with individual scFv revealed that the scFv significantly inhibited the growth of the RPMI8226 and chronic lymphocytic leukemia (CLL) cells in comparison with the untreated cells ( p < 0.05). Interestingly, 24-h treatment with specific scFv induced apoptosis cell death in the RPMI8226 and CLL cells. Taken together, our results demonstrate that targeting of ROR1 using peptide-specific scFv can be an effective immunotherapy strategy in hematological malignancies.

Receptor tyrosine kinases in carcinogenesis

Receptor tyrosine kinases (RTKs) are cell surface glycoproteins with enzymatic activity involved in the regulation of various important functions. In all-important physiological functions including differentiation, cell-cell interactions, survival, proliferation, metabolism, migration and signaling these receptors are the key players of regulation. Additionally, mutations of RTKs or their overexpression have been described in many human cancers and are being explored as a novel avenue for a new therapeutic approach. Some of the deregulated RTKs observed to be significantly affected in cancers included vascular endothelial growth factor receptor, epidermal growth factor receptor, fibroblast growth factor receptor, RTK-like orphan receptor 1 (ROR1) and the platelet-derived growth factor receptor. These deregulated RTKs offer attractive possibilities for the new anticancer therapeutic approach involving specific targeting by monoclonal antibodies as well as kinase. The present review aimed to highlight recent perspectives of RTK ROR1 in cancer.

ROR1 contributes to melanoma cell growth and migration by regulating N-cadherin expression via the PI3K/Akt pathway

The Receptor tyrosine kinase-like Orphan Receptor 1 (ROR1) is primarily expressed by neural crest cells during embryogenesis. Following a complete downregulation after birth, ROR1 was shown to re-express in various types of cancers. Little is known about ROR1 expression and function in melanoma. Here we show that ROR1 is aberrantly expressed in both melanoma cell lines and tumors and that its expression associates with poor Post-Recurrence Survival of melanoma. Using gain- and loss-of-function approaches we found that ROR1 enhances both anchorage-dependent and -independent growth of melanoma cells. In addition, ROR1 decreases cell adhesion and increases cell motility and migration. Mechanistically, ROR1 was found to induce upregulation of Akt and the mesenquimal markers N-cadherin and vimentin. The regulation of N-cadherin by ROR1 relies on both Akt dependent and independent mechanisms. ROR1 does not affect Wnt canonical pathway but was found to be engaged in a positive feedback loop with Wnt5a. In summary, we show that ROR1 contributes to melanoma progression and is a candidate biomarker of poor prognosis. Although further studies are needed to confirm this possibility, the present work indicates that ROR1 is a good prospective target for melanoma cancer therapy. © 2015 Wiley Periodicals, Inc.

Identifying new targets in leukemogenesis using computational approaches

There is a need to identify novel targets in Acute Lymphoblastic Leukemia (ALL), a hematopoietic cancer affecting children, to improve our understanding of disease biology and that can be used for developing new therapeutics. Hence, the aim of our study was to find new genes as targets using in silico studies; for this we retrieved the top 10% overexpressed genes from Oncomine public domain microarray expression database; 530 overexpressed genes were short-listed from Oncomine database. Then, using prioritization tools such as ENDEAVOUR, DIR and TOPPGene online tools, we found fifty-four genes common to the three prioritization tools which formed our candidate leukemogenic genes for this study. As per the protocol we selected thirty training genes from PubMed. The prioritized and training genes were then used to construct STRING functional association network, which was further analyzed using cytoHubba hub analysis tool to investigate new genes which could form drug targets in leukemia. Analysis of the STRING protein network built from these prioritized and training genes led to identification of two hub genes, SMAD2 and CDK9, which were not implicated in leukemogenesis earlier. Filtering out from several hundred genes in the network we also found MEN1, HDAC1 and LCK genes, which re-emphasized the important role of these genes in leukemogenesis. This is the first report on these five additional signature genes in leukemogenesis. We propose these as new targets for developing novel therapeutics and also as biomarkers in leukemogenesis, which could be important for prognosis and diagnosis.

microRNA regulation of Wnt signaling pathways in development and disease

Wnt signaling pathways and microRNAs (miRNAs) are critical regulators of development. Aberrant Wnt signaling pathways and miRNA levels lead to developmental defects and diverse human pathologies including but not limited to cancer. Wnt signaling pathways regulate a plethora of cellular processes during embryonic development and maintain homeostasis of adult tissues. A majority of Wnt signaling components are regulated by miRNAs which are small noncoding RNAs that are expressed in both animals and plants. In animal cells, miRNAs fine tune gene expression by pairing primarily to the 3'untranslated region of protein coding mRNAs to repress target mRNA translation and/or induce target degradation. miRNA-mediated regulation of signaling transduction pathways is important in modulating dose-sensitive response of cells to signaling molecules. This review discusses components of the Wnt signaling pathways that are regulated by miRNAs in the context of development and diseases. A fundamental understanding of miRNA functions in Wnt signaling transduction pathways may yield new insight into crosstalks of regulatory mechanisms essential for development and disease pathophysiology leading to novel therapeutics.

An In silico Chimeric Vaccine Targeting Breast Cancer Containing Inherent Adjuvant

Background:

Today, Lack of efficient therapeutic strategy for breast cancer (the most common cause of death in women) is one of the momentous problematic topics for all health care committees. Designing new specific vaccine, based on antigens located on the surface of cancer cells can be useful. Over expression of ROR1, lacked of HER2/neu, and hormone receptors on cell surface in the breast cancer, introduce this protein as an appropriate candidate for designing cancer vaccine.

Objectives:

We hypothesized the extracellular domain of receptor tyrosine kinase like orphan receptor 1 (ROR-1) along with a super antigen such as staphylococcal enterotoxin B could be a potent vaccine for drug resistant breast cancer.

Materials and Methods:

Here, we assessed the findings of bioinformatics analysis to identify the antitumor immune properties of this chimeric construct. In addition, the stability, physic-chemical properties and allergic potency of designed fusion protein were investigated by valid bioinformatics software.

Results:

Our result suggested that chimeric model is capable to be a stimulant of both T-cell and B- cell mediated immune responses with an acceptable accessibility and solubility but without any allergenicity.

Conclusions:

The ROR-1 with an enterotoxin B could be a potent vaccine for breast cancer.

Silencing of Receptor Tyrosine Kinase ROR1 Inhibits Tumor-Cell Proliferation via PI3K/AKT/mTOR Signaling Pathway in Lung Adenocarcinoma

Receptor tyrosine kinase ROR1, an embryonic protein involved in organogenesis, is expressed in certain hematological malignancies and solid tumors, but is generally absent in adult tissues. This makes the protein an ideal drug target for cancer therapy. In order to assess the suitability of ROR1 as a cell surface antigen for targeted therapy of lung adenocarcinoma, we carried out a comprehensive analysis of ROR1 protein expression in human lung adenocarcinoma tissues and cell lines. Our data show that ROR1 protein is selectively expressed on lung adenocarcinoma cells, but do not support the hypothesis that expression levels of ROR1 are associated with aggressive disease. However silencing of ROR1 via siRNA treatment significantly down-regulates the activity of the PI3K/AKT/mTOR signaling pathway. This is associated with significant apoptosis and anti-proliferation of tumor cells. We found ROR1 protein expressed in lung adenocarcinoma but almost absent in tumor-adjacent tissues of the patients. The finding of ROR1-mediated proliferation signals in both tyrosine kinase inhibitor (TKI)-sensitive and -resistant tumor cells provides encouragement to develop ROR1-directed targeted therapy in lung adenocarcinoma, especially those with TKI resistance.

The receptor tyrosine kinase ROR1--an oncofetal antigen for targeted cancer therapy

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.

The dual role of the novel Wnt receptor tyrosine kinase, ROR2, in human carcinogenesis

The Wnt signaling pathway is involved in the development and progression of many human cancers, yet attempts to target the pathway therapeutically have been disappointing to date. The recent discovery that the ROR2 receptor tyrosine kinase (RTK) is a novel Wnt receptor provides the potential to target the non-canonical Wnt pathway for cancer treatments. As a member of the RTK superfamily of surface receptors ROR2 appears to possess dual roles as a tumor suppressor or activator depending on tumor type. This review will explore the dual role of ROR2 in tumorigenesis and provide an up to date analysis of current literature in this rapidly expanding field.

Restricted cell surface expression of receptor tyrosine kinase ROR1 in pediatric B-lineage acute lymphoblastic leukemia suggests targetability with therapeutic monoclonal antibodies

BACKGROUND

Despite high cure rates for pediatric B-lineage acute lymphoblastic leukemia (B-ALL), short-term and long-term toxicities and chemoresistance are shortcomings of standard chemotherapy. Immunotherapy and chemoimmunotherapy based on monoclonal antibodies (mAbs) that target cell surface antigens with restricted expression in pediatric B-ALL may offer the potential to reduce toxicities and prevent or overcome chemoresistance. The receptor tyrosine kinase ROR1 has emerged as a candidate for mAb targeting in select B-cell malignancies.

METHODOLOGY AND PRINCIPAL FINDINGS

Using flow cytometry, Western blotting, immunohistochemistry, and confocal immunofluorescence microscopy, we analyzed the cell surface expression of ROR1 across major pediatric ALL subtypes represented by 14 cell lines and 56 primary blasts at diagnosis or relapse as well as in normal adult and pediatric tissues. Cell surface ROR1 expression was found in 45% of pediatric ALL patients, all of which were B-ALL, and was not limited to any particular genotype. All cell lines and primary blasts with E2A-PBX1 translocation and a portion of patients with other high risk genotypes, such as MLL rearrangement, expressed cell surface ROR1. Importantly, cell surface ROR1 expression was found in many of the pediatric B-ALL patients with multiply relapsed and refractory disease and normal karyotype or low risk cytogenetics, such as hyperdiploidy. Notably, cell surface ROR1 was virtually absent in normal adult and pediatric tissues.

CONCLUSIONS AND SIGNIFICANCE

Collectively, this study suggests that ROR1 merits preclinical and clinical investigations as a novel target for mAb-based therapies in pediatric B-ALL. We propose cell surface expression of ROR1 detected by flow cytometry as primary inclusion criterion for pediatric B-ALL patients in future clinical trials of ROR1-targeted therapies.

Patients with activated B-cell like diffuse large B-cell lymphoma in high and low infectious disease areas have different inflammatory gene signatures

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease with an association with inflammation and viral infections. We hypothesize that environmental factors may be involved in the pathogenesis of DLBCL. In this study, we compared gene expression profiles of lymph node tissues from patients with DLBCL from two different geographical areas with diverse environmental exposures. Specimens from Egyptian and Swedish patients with DLBCL as well as controls were studied. Gene expression analysis using microarray and quantitative polymerase chain reaction demonstrated significantly higher expression of signal transducer and activator of transcription 3 (STAT3) in Swedish as compared to Egyptian patients and control materials from both countries. This was confirmed at protein level using confocal microscopy. The receptor tyrosine kinase ROR1, a "survival factor" for malignant cells, was overexpressed and significantly related to the STAT3 expression pattern. The difference in the expression of genes involved in inflammatory responses and in the tumorigenic process of DLBCL might relate to infectious agents and/or other environmental exposures.

Alternative Wnt pathways and receptors

In addition to activating β-catenin/TCF transcriptional complexes, Wnt proteins can elicit a variety of other responses. These are often lumped together under the denominator "alternative" or "non-canonical" Wnt signaling, but they likely comprise distinct signaling events. In this article, I discuss how the use of different ligand and receptor combinations is thought to give rise to these alternative Wnt-signaling responses. Although many of the biochemical details remain to be resolved, it is evident that alternative Wnt signaling plays important roles in regulating tissue morphogenesis during embryonic development.

Detection of orphan receptor tyrosine kinase (ROR-1) expression in Egyptian pediatric acute lymphoblastic leukemia

Receptor tyrosine kinases, a group of tumor-associated antigens, were introduced as targets for cancer intervention strategies. The human orphan receptor tyrosine kinase-1 (ROR-1) is a member of this family. Overexpression of ROR1 has been reported in B-cell chronic lymphocytic leukemia. The aim of this study was to detect the expression profile of ROR1 in 54 pediatric acute lymphoblastic leukemia (ALL) patients. ROR1 was overexpressed in ALL as the ROR1/ β-actin ratio was higher in ALL children than in control group (P = 0.024). ROR1 is a potential tool for targeted immunotherapy in pediatric ALL patients.

ROR1 and ROR2 in Human Malignancies: Potentials for Targeted Therapy

Targeted therapies require cellular protein expression that meets specific requirements that will maximize effectiveness, minimize off-target toxicities, and provide an opportunity for a therapeutic effect. The receptor tyrosine kinase-like orphan receptors (ROR) are possible targets for therapy that may meet such requirements. RORs are transmembrane proteins that are part of the receptor tyrosine kinase (RTK) family. The RORs have been shown to play a role in tumor-like behavior, such as cell migration and cell invasiveness and are normally not expressed in normal adult tissue. As part of the large effort in target discovery, ROR proteins have recently been found to be expressed in human cancers. Their unique expression profiles may provide a novel class of therapeutic targets for small molecules against the kinase or for antibody-based therapies against these receptors. Being restricted on tumor cells and not on most normal tissues, RORs are excellent targets for the treatment of minimal residual disease, the final hurdle in the curative approach to many cancers, including solid tumors such as neuroblastoma. In this review, we summarize the biology of RORs as they relate to human cancer, and highlight the therapeutic approaches directed toward them.

Differential and tumor-specific expression of CD160 in B-cell malignancies

CD160 is a human natural killer (NK)-cell-activating receptor that is also expressed on T-cell subsets. In the present study, we examined 811 consecutive cases of B-cell lymphoproliferative disorders (B-LPDs), and demonstrated CD160 expression in 98% (590 of 600) of chronic lymphocytic leukemia (CLL) cases, 100% (32 of 32) of hairy cell leukemia (HCL) cases, 15% (5 of 34) of mantle cell lymphoma (MCL) in the leukemic phase, and 16% (23 of 145) of other B-LPD cases. CD160 transcript and protein were absent in the normal B-cell hierarchy, from stem cells, B-cell precursors, maturing B cells in the germinal center, and circulating B cells, including CD5(+)CD19(+) B1 cells in umbilical cord. CD160 positivity was significantly higher in CLL and HCL in terms of percentage (65.9% and 67.8%, respectively, P < .0001) and median fluorescence intensity (552 and 857, respectively, P < .0001) compared with all other B-LPD cases. Lymph node CLL samples were also CD160(+). Using the disease-specific expression of CD5, CD23, and CD160, a score of 3 characterized CLL (diagnostic odds ratio, 1430); a score of 0 excluded CLL, MCL, and HCL; and the CD23/CD5 ratio differentiated CLL from leukemic CD23(+) MCL. In the B-cell lineage, CD160 is a tumor-specific antigen known to mediate cellular activation signals in CLL, and is a novel target for therapeutic manipulation and monitoring of minimal residual disease.

Use of the receptor tyrosine kinase-like orphan receptor 1 (ROR1) as a diagnostic tool in chronic lymphocytic leukemia (CLL)

Flow cytometry is commonly used to establish the diagnosis of chronic lymphocytic leukemia (CLL). A defined combination of antibodies discriminates between normal B cells and CLL cells (coexpression of CD5, CD19, and CD23). The receptor tyrosine-like orphan receptor one (ROR1) is an embryonic glycoprotein involved in several developmental processes. It was shown to be highly and specifically expressed on circulating B lymphoma cells, but not on normal B cells. Here, we examined the potential of ROR1 as a diagnostic marker in initial and follow-up diagnostics of patients with CLL. 105 untreated and 72 treated patients, as well as healthy volunteers were examined using flow cytometry assays. Furthermore, we examined 10 patients with various B cell non-Hodgkin lymphomas (B-NHL). ROR1 was detected using a directly labeled antibody. We detected uniformly high ROR1 expression levels in all CLL samples. In marked contrast, only low or absent ROR1 expression levels were found on B cells from healthy donors. ROR1 expression in CLL patients was not influenced by various treatments. Taken together, ROR1 may be used as a diagnostic marker for CLL. As it is the only antigen which can exclusively be detected on neoplastic B cells it may greatly increase both, specificity as well as sensitivity, in lymphoma diagnostics.

MYBPC1 computational phosphoprotein network construction and analysis between frontal cortex of HIV encephalitis (HIVE) and HIVE-control patients

MYBPC1 computational phosphoprotein network construction and analysis of frontal cortex of HIV encephalitis (HIVE) was very useful to identify novel markers and potential targets for prognosis and therapy. Based on integrated gene regulatory network infer method by linear programming and a decomposition procedure with analysis of the significant function cluster using kappa statistics and fuzzy heuristic clustering from the database for annotation, visualization, and integrated discovery, we identified and constructed significant molecule MYBPC1 phosphoprotein network from 12 frontal cortex of HIVEcontrol patients and 16 HIVE in the same GEO Dataset GDS1726. Our result verified MYBPC1 phosphoprotein module only in the upstream of frontal cortex of HIVEcontrol patients (CREB5, MAPKAPK3 inhibition), whereas in the upstream of frontal cortex of HIVE (CREB5, ZC3HAV1 activation; ROR1 inhibition) and downstream (MAPKAPK3 activation; CFDP1, PDCD4, RBBP6 inhibition). Importantly, we determined that MYBPC1 phosphoprotein cluster of HIVE was involved in signal transduction, transferase, post-translational protein modification, developmental process and glycoprotein (only in HIVE terms), the condition was vital to inflammation and cognition impairment of HIVE. Our result demonstrated that common terms in both HIVE-control patients and HIVE included phosphoprotein, organelle, response to stimulus, nucleic acid binding, primary metabolic process, and biological regulation, and these terms were more relative to inflammation and cognition impairment, therefore, we deduced the stronger MYBPC1 phosphoprotein network in HIVE. It would be necessary of the stronger MYBPC1 phosphoprotein function to inflammation and cognition impairment of HIVE.

Mice lacking the orphan receptor ror1 have distinct skeletal abnormalities and are growth retarded

Ror1 is a member of the Ror-family receptor tyrosine kinases. Ror1 is broadly expressed in various tissues and organs during mouse embryonic development. However, so far little is known about its function. The closely related family member Ror2 was shown to play a crucial role in skeletogenesis and has been shown to act as a co-receptor for Wnt5a mediating non-canonical Wnt-signaling. Previously, it has been shown that during embryonic development Ror1 acts in part redundantly with Ror2 in the skeletal and cardiovascular systems. In this study, we report that loss of the orphan receptor Ror1 results in a variety of phenotypic defects within the skeletal and urogenital systems and that Ror1 mutant mice display a postnatal growth retardation phenotype.

The B-cell tumor-associated antigen ROR1 can be targeted with T cells modified to express a ROR1-specific chimeric antigen receptor

Monoclonal antibodies and T cells modified to express chimeric antigen receptors specific for B-cell lineage surface molecules such as CD20 exert antitumor activity in B-cell malignancies, but deplete normal B cells. The receptor tyrosine kinase-like orphan receptor 1 (ROR1) was identified as a highly expressed gene in B-cell chronic lymphocytic leukemia (B-CLL), but not normal B cells, suggesting it may serve as a tumor-specific target for therapy. We analyzed ROR1-expression in normal nonhematopoietic and hematopoietic cells including B-cell precursors, and in hematopoietic malignancies. ROR1 has characteristics of an oncofetal gene and is expressed in undifferentiated embryonic stem cells, B-CLL and mantle cell lymphoma, but not in major adult tissues apart from low levels in adipose tissue and at an early stage of B-cell development. We constructed a ROR1-specific chimeric antigen receptor that when expressed in T cells from healthy donors or CLL patients conferred specific recognition of primary B-CLL and mantle cell lymphoma, including rare drug effluxing chemotherapy resistant tumor cells that have been implicated in maintaining the malignancy, but not mature normal B cells. T-cell therapies targeting ROR1 may be effective in B-CLL and other ROR1-positive tumors. However, the expression of ROR1 on some normal tissues suggests the potential for toxi-city to subsets of normal cells.

Stat3 activates the receptor tyrosine kinase like orphan receptor-1 gene in chronic lymphocytic leukemia cells

Background

The receptor tyrosine kinase like orphan receptor (ROR)-1 gene is overexpressed in chronic lymphocytic leukemia (CLL). Because Stat3 is constitutively activated in CLL and sequence analysis revealed that the ROR1 promoter harbors γ-interferon activation sequence-like elements typically activated by Stat3, we hypothesized that Stat3 activates ROR1.

Methodology/Principal Findings

Because IL-6 induced Stat3 phosphorylation and upregulated Ror1 protein levels in MM1 cells, we used these cells as a model. We transfected MM1 cells with truncated ROR1 promoter luciferase reporter constructs and found that IL-6 induced luciferase activity of ROR1-195 and upstream constructs. Co-transfection with Stat3 siRNA reduced the IL-6-induced luciferase activity, suggesting that IL-6 induced luciferase activity by activating Stat3. EMSA and the ChIP assay confirmed that Stat3 binds ROR1, and EMSA studies identified two Stat3 binding sites. In CLL cells, EMSA and ChIP studies determined that phosphorylated Stat3 bound to the ROR1 promoter at those two ROR1 promoter sites, and ChIP analysis showed that Stat3 co-immunoprecipitated DNA of STAT3, ROR1, and several Stat3-regulated genes. Finally, like STAT3-siRNA in MM1 cells, STAT3-shRNA downregulated STAT3, ROR1, and STAT3-regulated genes and Stat3 and Ror1 protein levels in CLL cells.

Conclusion/Significance

Our data suggest that constitutively activated Stat3 binds to the ROR1 promoter and activates ROR1 in CLL cells.

Ror-family receptor tyrosine kinases in noncanonical Wnt signaling: their implications in developmental morphogenesis and human diseases

The Ror-family receptor tyrosine kinases (RTKs) play crucial roles in the development of various organs and tissues. In mammals, Ror2, a member of the Ror-family RTKs, has been shown to act as a receptor or coreceptor for Wnt5a to mediate noncanonical Wnt signaling. Ror2- and Wnt5a-deficient mice exhibit similar abnormalities during developmental morphogenesis, reflecting their defects in convergent extension movements and planar cell polarity, characteristic features mediated by noncanonical Wnt signaling. Furthermore, mutations within the human Ror2 gene are responsible for the genetic skeletal disorders dominant brachydactyly type B and recessive Robinow syndrome. Accumulating evidence demonstrate that Ror2 mediates noncanonical Wnt5a signaling by inhibiting the beta-catenin-TCF pathway and activating the Wnt/JNK pathway that results in polarized cell migration. In this article, we review recent progress in understanding the roles of noncanonical Wnt5a/Ror2 signaling in developmental morphogenesis and in human diseases, including heritable skeletal disorders and tumor invasion.

DNA methylation for subtype classification and prediction of treatment outcome in patients with childhood acute lymphoblastic leukemia

Despite improvements in the prognosis of childhood acute lymphoblastic leukemia (ALL), subgroups of patients would benefit from alternative treatment approaches. Our aim was to identify genes with DNA methylation profiles that could identify such groups. We determined the methylation levels of 1320 CpG sites in regulatory regions of 416 genes in cells from 401 children diagnosed with ALL. Hierarchical clustering of 300 CpG sites distinguished between T-lineage ALL and B-cell precursor (BCP) ALL and between the main cytogenetic subtypes of BCP ALL. It also stratified patients with high hyperdiploidy and t(12;21) ALL into 2 subgroups with different probability of relapse. By using supervised learning, we constructed multivariate classifiers by external cross-validation procedures. We identified 40 genes that consistently contributed to accurate discrimination between the main subtypes of BCP ALL and gene sets that discriminated between subtypes of ALL and between ALL and controls in pairwise classification analyses. We also identified 20 individual genes with DNA methylation levels that predicted relapse of leukemia. Thus, methylation analysis should be explored as a method to improve stratification of ALL patients. The genes highlighted in our study are not enriched to specific pathways, but the gene expression levels are inversely correlated to the methylation levels.

RNAi screen for rapid therapeutic target identification in leukemia patients

Targeted therapy has vastly improved outcomes in certain types of cancer. Extension of this paradigm across a broad spectrum of malignancies will require an efficient method to determine the molecular vulnerabilities of cancerous cells. Improvements in sequencing technology will soon enable high-throughput sequencing of entire genomes of cancer patients; however, determining the relevance of identified sequence variants will require complementary functional analyses. Here, we report an RNAi-assisted protein target identification (RAPID) technology that individually assesses targeting of each member of the tyrosine kinase gene family. We demonstrate that RAPID screening of primary leukemia cells from 30 patients identifies targets that are critical to survival of the malignant cells from 10 of these individuals. We identify known, activating mutations in JAK2 and K-RAS, as well as patient-specific sensitivity to down-regulation of FLT1, CSF1R, PDGFR, ROR1, EPHA4/5, JAK1/3, LMTK3, LYN, FYN, PTK2B, and N-RAS. We also describe a previously undescribed, somatic, activating mutation in the thrombopoietin receptor that is sensitive to down-stream pharmacologic inhibition. Hence, the RAPID technique can quickly identify molecular vulnerabilities in malignant cells. Combination of this technique with whole-genome sequencing will represent an ideal tool for oncogenic target identification such that specific therapies can be matched with individual patients.