Ror2 as a therapeutic target in cancer

Novel Antibody Drug Conjugates Targeting Tumor-Associated Receptor Tyrosine Kinase ROR2 by Functional Screening of Fully Human Antibody Libraries Using Transpo-mAb Display on Progenitor B Cells

Receptor tyrosine kinase-like orphan receptor 2 (ROR2) has been identified as a highly relevant tumor-associated antigen in a variety of cancer indications of high unmet medical need, including renal cell carcinoma and osteosarcoma, making it an attractive target for targeted cancer therapy. Here, we describe the de novo discovery of fully human ROR2-specific antibodies and potent antibody drug conjugates (ADCs) derived thereof by combining antibody discovery from immune libraries of human immunoglobulin transgenic animals using the Transpo-mAb mammalian cell-based IgG display platform with functional screening for internalizing antibodies using a secondary ADC assay. The discovery strategy entailed immunization of transgenic mice with the cancer antigen ROR2, harboring transgenic IgH and IgL chain gene loci with limited number of fully human V, D, and J gene segments. This was followed by recovering antibody repertoires from the immunized animals, expressing and screening them as full-length human IgG libraries by transposon-mediated display in progenitor B lymphocytes ("Transpo-mAb Display") for ROR2 binding. Individual cellular "Transpo-mAb" clones isolated by single cell sorting and capable of expressing membrane-bound as well as secreted human IgG were directly screened during antibody discovery, not only for high affinity binding to human ROR2, but also functionally as ADCs using a cytotoxicity assay with a secondary anti-human IgG-toxin-conjugate. Using this strategy, we identified and validated 12 fully human, monoclonal anti-human ROR2 antibodies with nanomolar affinities that are highly potent as ADCs and could be promising candidates for the therapy of human cancer. The screening for functional and internalizing antibodies during the early phase of antibody discovery demonstrates the utility of the mammalian cell-based Transpo-mAb Display platform to select for functional binders and as a powerful tool to improve the efficiency for the development of therapeutically relevant ADCs.

ROR2 modulates neuropathic pain via phosphorylation of NMDA receptor subunit GluN2B in rats

BACKGROUND

Neuropathic pain, a type of chronic pain as a result of direct central or peripheral nerve damage, is associated with significant quality of life and functional impairment. Its underlying mechanisms remain unclear. We investigated whether ROR2, a member of the receptor tyrosine kinase-like orphan receptor (ROR) family, participates in modulation of neuropathic pain.

METHODS

Thermal hyperalgesia and mechanical allodynia were measured using radiant heat and von Frey filament testing. Immunofluorescence staining was used to detect expression of ROR2 in neuronal nuclei. Fos expression was determined by immunocytochemistry. Phosphorylation status was detected by western blot and immunoprecipitation. Small interfering RNA was used to knock down ROR2 expression.

RESULTS

ROR2 was upregulated and activated in spinal neurones after chronic constriction injury (CCI) in mice [1.3 (0.1) to 2.1 (0.1)-fold of sham, P<0.01] from Day 1-21. CCI induced significant demethylation of the CpG island in the ROR2 gene promoter [0.37 (0.06) vs 0.12 (0.03)% CpG methylation, P<0.001]. Knockdown of ROR2 in the spinal cord prevented and reversed CCI-induced pain behaviours and spinal neuronal sensitisation [Fos expression: 130 (12) vs 81 (8) cells, P<0.05; 120 (11) vs 70 (7) cells, P<0.05]. In contrast, activation of spinal ROR2 by intrathecal injection of Wnt5a induced pain behaviours and spinal neuronal sensitisation [Fos expression: 11 (1) vs 100 (12) cells, P<0.001] in wild-type mice. Furthermore, ROR2-mediated pain modulation required phosphorylation of N-methyl-D-aspartate receptor 2B subunit (GluN2B) at Ser 1303 and Tyr1472 by pathways involving protein kinase C (PKC) and Src family kinases. Intrathecal injection of GluN2B, PKC, or Src family kinase-specific inhibitors significantly attenuated Wnt5a-induced pain behaviours.

CONCLUSIONS

ROR2 in the spinal cord regulates neuropathic pain via phosphorylation of GluN2B, suggesting a potential target for prevention and relief of neuropathic pain.

miR-18a-5p promotes cell invasion and migration of osteosarcoma by directly targeting IRF2

An increasing number of studies have suggested that microRNAs (miRNAs) are involved in the progress of many human cancers including osteosarcoma (OS). Especially, microRNA-18a-5p (miR-18a-5p) has been reported to associate with the occurrence, development and clinical outcomes of human cancers. Therefore, we investigated the functions of miR-18a-5p in OS. Reverse transcription-quantitative PCR (RT-qPCR) showed that miR-18a-5p was significantly upregulated in OS tissues and cell lines (MG-63 and Saos-2). The overexpression of miR-18a-5p was found to significantly promote cell migration and invasion in MG-63 cells via Transwell assay. Moreover, luciferase reporter assays indicated that interferon regulatory factor (IRF)2 was a direct target of miR-18a-5p. IRF2 was downregulated in MG-63 and Saos-2 cell lines. Furthermore, Transwell analysis showed that the knockout of IRF2 promoted cell migration and invasion in MG-63 cells. Carcinogenesis of miR-18a-5p was reversed by the overexpression of IRF2 in OS. In conclusion, miR-18a-5p promoted the invasion and migration of OS cells through inhibiting IRF2 expression. Thus, miR-18a-5p might act as a potential target for the diagnosis and treatment of OS in the future.

miR-205-5p inhibits cell migration and invasion in prostatic carcinoma by targeting ZEB1

Many studies have demonstrated that miRNAs have influence on tumorigenesis and progression of human cancers, including invasion and migration. Thus, the role of miR-205/ZEB1 axis for the migration and invasion of prostate cancer cells was explored in the present study. The miR-205-5p and zinc finger E-box binding homeobox 1 (ZEB1) mRNA expression levels were observed in prostate cancer tissues or cell lines via reverse transcription-quantitative PCR (RT-qPCR), and the protein level of ZEB1 was measured by western blotting. Dual-Luciferase Reporter Assay was used to verify the relationship between miR-205-5p and ZEB1. In addition, cell migration and invasion was measured by Transwell assay. The results revealed that, compared with the control, downregulation of miR-205-5p was detected in prostate cancer tissues and cell lines, and miR-205-5p overexpression was found to inhibit cell migration and invasion. Moreover, miR-205-5p was confirmed to directly target ZEB1 in prostate cancer. Importantly, ZEB1 was identified to weaken the inhibitory effect of miR-205-5p in prostate cancer. In conclusion, miR-205-5p inhibited cell migration and invasion in prostatic carcinoma by targeting ZEB1 and miR-205-5p/ZEB1 axis shows potential to be developed in therapeutic strategies for prostate cancer.

Possible repurposing of pyrvinium pamoate for the treatment of mesothelioma: A pre-clinical assessment

Malignant mesothelioma (MM) is a very aggressive asbestos-related cancer, whose incidence is increasing worldwide. Unfortunately, no effective therapies are currently available and the prognosis is extremely poor. Recently, the anti-helminthic drug pyrvinium pamoate has attracted a strong interest for its anti-cancer activity, which has been demonstrated in many cancer models. Considering the previously established inhibitory effect of pyrvinium pamoate on the Wnt/β-catenin pathway and given the important role of this pathway in MM, we investigated the potential anti-tumor activity of this drug in MM cell lines. We observed that pyrvinium pamoate significantly impairs MM cell proliferation, cloning efficiency, migration, and tumor spheroid formation. At the molecular level, our data show that pyrvinium pamoate down-regulates the expression of β-catenin and Wnt-regulates genes. Overall, our study suggests that the repurposing of pyrvinium pamoate for MM treatment could represent a new promising therapeutic approach.

The biochemistry, signalling and disease relevance of RYK and other WNT-binding receptor tyrosine kinases

The receptor tyrosine kinases (RTKs) are a well-characterized family of growth factor receptors that have central roles in human disease and are frequently therapeutically targeted. The RYK, ROR, PTK7 and MuSK subfamilies make up an understudied subset of WNT-binding RTKs. Numerous developmental, stem cell and pathological roles of WNTs, in particular WNT5A, involve signalling via these WNT receptors. The WNT-binding RTKs have highly context-dependent signalling outputs and stimulate the β-catenin-dependent, planar cell polarity and/or WNT/Ca²⁺ pathways. RYK, ROR and PTK7 members have a pseudokinase domain in their intracellular regions. Alternative signalling mechanisms, including proteolytic cleavage and protein scaffolding functions, have been identified for these receptors. This review explores the structure, signalling, physiological and pathological roles of RYK, with particular attention paid to cancer and the possibility of therapeutically targeting RYK. The other WNT-binding RTKs are compared with RYK throughout to highlight the similarities and differences within this subset of WNT receptors.

Effects of trastuzumab and afatinib on kinase activity in gastric cancer cell lines

The molecular mechanism of action of the HER2‐targeted antibody trastuzumab is only partially understood, and the direct effects of trastuzumab on the gastric cancer signaling network are unknown. In this study, we compared the molecular effect of trastuzumab and the HER kinase inhibitor afatinib on the receptor tyrosine kinase (RTK) network and the downstream‐acting intracellular kinases in gastric cancer cell lines. The molecular effects of trastuzumab and afatinib on the phosphorylation of 49 RTKs and 43 intracellular kinase phosphorylation sites were investigated in three gastric cancer cell lines (NCI‐N87, MKN1, and MKN7) using proteome profiling. To evaluate these effects, data were analyzed using mixed models and clustering. Moreover, proliferation assays were performed. Our comprehensive quantitative analysis of kinase activity in gastric cancer cell lines indicates that trastuzumab and afatinib selectively influenced the HER family RTKs. The effects of trastuzumab differed between cell lines, depending on the presence of activated HER2. The effects of trastuzumab monotherapy were not transduced to the intracellular kinase network. Afatinib alone or in combination with trastuzumab influenced HER kinases in all cell lines; that is, the effects of monotherapy and combination therapy were transduced to the intracellular kinase network. These results were confirmed by proliferation analysis. Additionally, the MET‐amplified cell line Hs746T was identified as afatinib nonresponder. The dependence of the effect of trastuzumab on the presence of activated HER2 might explain the clinical nonresponse of some patients who are routinely tested for HER2 expression and gene amplification in the clinic but not for HER2 activation. The consistent effects of afatinib on HER RTKs and downstream kinase activation suggest that afatinib might be an effective candidate in the future treatment of patients with gastric cancer irrespective of the presence of activated HER2. However, MET amplification should be taken into account as potential resistance factor.

Silencing ROR1 and ROR2 inhibits invasion and adhesion in an organotypic model of ovarian cancer metastasis

OBJECTIVE

Elevated expression of the ROR1 and ROR2 Wnt receptors has been noted in both the tumour and stromal compartments of ovarian cancer patient tissue samples. In vitro studies have suggested these receptors play a role in ovarian cancer metastasis. However, these previous studies have utilised simple 2D in vitro models to investigate cancer cell growth and migration, which does not allow investigation of stromal involvement in Wnt driven metastasis.

AIM

To investigate targeting ROR1 and ROR2 using a primary co-culture 3D model of epithelial ovarian cancer dissemination to the omentum.

METHODS

Primary fibroblasts (NOF) and mesothelial (HPMC) cells were isolated from fresh samples of omentum collected from women with benign or non-metastatic conditions and cultured with collagen to produce a organotypic 3D model. Stable shRNA knockdown of ROR1, ROR2 and double ROR1/ROR2 in OVCAR4 cells were plated onto the 3D model to measure adhesion, or using a transwell to measure invasion. Gene expression changes in primary cells upon OVCAR4 interaction was evaluated using indirect transwell co-culture.

RESULTS

Double knockdown of ROR1 and ROR2 strongly inhibited cell adhesion (p<0.05) and invasion (P<0.05) to the omentum model. ROR2 was up regulated in primary fibroblasts when cultured with OVCAR4 (P=0.05) and ectopic overexpression of ROR2 in NOFs inhibited cell proliferation (P<0.01) but increased cell migration.

CONCLUSION

The combination of ROR1 and ROR2 signalling influences ovarian cancer dissemination to the omentum, however ROR2 may also play a role in stromal activation during metastasis. Therefore, targeting both ROR1 and ROR2 may be a powerful approach to treating ovarian cancer.

Adipocytes sustain pancreatic cancer progression through a non-canonical WNT paracrine network inducing ROR2 nuclear shuttling

Background:

Solid epidemiological evidences connect obesity with incidence, stage and survival in pancreatic cancer. However, the underlying mechanistic basis linking adipocytes to pancreatic cancer progression remain largely elusive. We hypothesized that factors secreted by adipocytes could be responsible for epithelial-to-mesenchymal transition (EMT) induction and, in turn, a more aggressive phenotype in models of pancreatic preneoplastic lesions.

Methods:

We studied the role of factors secreted by two adipogenic model systems from primary human bone marrow stromal cells (hBMSCs) in an in vitro experimental cell transformation model system of human pancreatic ductal epithelial (HPDE) cell stably expressing activated KRAS (HPDE/KRAS),

Results:

We measured a significant induction of EMT and aggressiveness in HPDE and HPDE/KRAS cell lines when cultured with medium conditioned by fully differentiated adipocytes (ADIPO^CM) if compared with the same cells cultured with medium conditioned by hBMSC (hBMSC^CM) from two different healthy donors. Several genes coding for soluble modulators of the non-canonical WNT signaling pathway, including FRZB, SFRP2, RSPO1, WNT5A and 5B were significantly overexpressed in fully differentiated adipocytes than in their respective in hBMSC. ADIPO^CM induced the overexpression and the nuclear translocation of the Frizzled family member receptor tyrosine kinase-like orphan receptor (Ror) 2 in HPDE and HPDE/KRAS cells. Vantictumab, an anti-Frizzled monoclonal antibody, reduced ROR2 nuclear translocation and in turn the EMT and aggressiveness in HPDE and HPDE/KRAS cells.

Conclusions:

We demonstrated that adipocytes could induce EMT and aggressiveness in models of pancreatic preneoplastic lesions by orchestrating a complex paracrine signaling of soluble modulators of the non-canonical WNT signaling pathway that determine, in turn, the activation and nuclear translocation of ROR2. This signaling pathway could represent a novel target for pancreatic cancer chemoprevention. Most importantly, these factors could serve as novel biomarkers to select a risk population among obese subjects for screening and, thus, early diagnosis of pancreatic cancer.

Canonical and non-canonical WNT signaling in cancer stem cells and their niches: Cellular heterogeneity, omics reprogramming, targeted therapy and tumor plasticity (Review)

Cancer stem cells (CSCs), which have the potential for self-renewal, differentiation and de-differentiation, undergo epigenetic, epithelial-mesenchymal, immunological and metabolic reprogramming to adapt to the tumor microenvironment and survive host defense or therapeutic insults. Intra-tumor heterogeneity and cancer-cell plasticity give rise to therapeutic resistance and recurrence through clonal replacement and reactivation of dormant CSCs, respectively. WNT signaling cascades cross-talk with the FGF, Notch, Hedgehog and TGFβ/BMP signaling cascades and regulate expression of functional CSC markers, such as CD44, CD133 (PROM1), EPCAM and LGR5 (GPR49). Aberrant canonical and non-canonical WNT signaling in human malignancies, including breast, colorectal, gastric, lung, ovary, pancreatic, prostate and uterine cancers, leukemia and melanoma, are involved in CSC survival, bulk-tumor expansion and invasion/metastasis. WNT signaling-targeted therapeutics, such as anti-FZD1/2/5/7/8 monoclonal antibody (mAb) (vantictumab), anti-LGR5 antibody-drug conjugate (ADC) (mAb-mc-vc-PAB-MMAE), anti-PTK7 ADC (PF-06647020), anti-ROR1 mAb (cirmtuzumab), anti-RSPO3 mAb (rosmantuzumab), small-molecule porcupine inhibitors (ETC-159, WNT-C59 and WNT974), tankyrase inhibitors (AZ1366, G007-LK, NVP-TNKS656 and XAV939) and β-catenin inhibitors (BC2059, CWP232228, ICG-001 and PRI-724), are in clinical trials or preclinical studies for the treatment of patients with WNT-driven cancers. WNT signaling-targeted therapeutics are applicable for combination therapy with BCR-ABL, EGFR, FLT3, KIT or RET inhibitors to treat a subset of tyrosine kinase-driven cancers because WNT and tyrosine kinase signaling cascades converge to β-catenin for the maintenance and expansion of CSCs. WNT signaling-targeted therapeutics might also be applicable for combination therapy with immune checkpoint blockers, such as atezolizumab, avelumab, durvalumab, ipilimumab, nivolumab and pembrolizumab, to treat cancers with immune evasion, although the context-dependent effects of WNT signaling on immunity should be carefully assessed. Omics monitoring, such as genome sequencing and transcriptome tests, immunohistochemical analyses on PD-L1 (CD274), PD-1 (PDCD1), ROR1 and nuclear β-catenin and organoid-based drug screening, is necessary to determine the appropriate WNT signaling-targeted therapeutics for cancer patients.

Molecular genetics and targeted therapy of WNT-related human diseases (Review)

Canonical WNT signaling through Frizzled and LRP5/6 receptors is transduced to the WNT/β-catenin and WNT/stabilization of proteins (STOP) signaling cascades to regulate cell fate and proliferation, whereas non-canonical WNT signaling through Frizzled or ROR receptors is transduced to the WNT/planar cell polarity (PCP), WNT/G protein-coupled receptor (GPCR) and WNT/receptor tyrosine kinase (RTK) signaling cascades to regulate cytoskeletal dynamics and directional cell movement. WNT/β-catenin signaling cascade crosstalks with RTK/SRK and GPCR-cAMP-PKA signaling cascades to regulate β-catenin phosphorylation and β-catenin-dependent transcription. Germline mutations in WNT signaling molecules cause hereditary colorectal cancer, bone diseases, exudative vitreoretinopathy, intellectual disability syndrome and PCP-related diseases. APC or CTNNB1 mutations in colorectal, endometrial and prostate cancers activate the WNT/β-catenin signaling cascade. RNF43, ZNRF3, RSPO2 or RSPO3 alterations in breast, colorectal, gastric, pancreatic and other cancers activate the WNT/β-catenin, WNT/STOP and other WNT signaling cascades. ROR1 upregulation in B-cell leukemia and solid tumors and ROR2 upregulation in melanoma induce invasion, metastasis and therapeutic resistance through Rho-ROCK, Rac-JNK, PI3K-AKT and YAP signaling activation. WNT signaling in cancer, stromal and immune cells dynamically orchestrate immune evasion and antitumor immunity in a cell context-dependent manner. Porcupine (PORCN), RSPO3, WNT2B, FZD5, FZD10, ROR1, tankyrase and β-catenin are targets of anti-WNT signaling therapy, and ETC-159, LGK974, OMP-18R5 (vantictumab), OMP-54F28 (ipafricept), OMP-131R10 (rosmantuzumab), PRI-724 and UC-961 (cirmtuzumab) are in clinical trials for cancer patients. Different classes of anti-WNT signaling therapeutics are necessary for the treatment of APC/CTNNB1-, RNF43/ZNRF3/RSPO2/RSPO3- and ROR1-types of human cancers. By contrast, Dickkopf-related protein 1 (DKK1), SOST and glycogen synthase kinase 3β (GSK3β) are targets of pro-WNT signaling therapy, and anti-DKK1 (BHQ880 and DKN-01) and anti-SOST (blosozumab, BPS804 and romosozumab) monoclonal antibodies are being tested in clinical trials for cancer patients and osteoporotic post-menopausal women. WNT-targeting therapeutics have also been applied as reagents for in vitro stem-cell processing in the field of regenerative medicine.

Mining Naïve Rabbit Antibody Repertoires by Phage Display for Monoclonal Antibodies of Therapeutic Utility

Owing to their high affinities and specificities, rabbit monoclonal antibodies (mAbs) have demonstrated value and potential primarily as basic research and diagnostic reagents, but, in some cases, also as therapeutics. To accelerate access to rabbit mAbs bypassing immunization, we generated a large naïve rabbit antibody repertoire represented by a phage display library encompassing >10 billion independent antibodies in chimeric rabbit/human Fab format and validated it by next-generation sequencing. Panels of rabbit mAbs selected from this library against two emerging cancer targets, ROR1 and ROR2, revealed high diversity, affinity, and specificity. Moreover, ROR1- and ROR2-targeting rabbit mAbs demonstrated therapeutic utility as components of chimeric antigen receptor-engineered T cells, further corroborating the value of the naïve rabbit antibody library as a rich and virtually unlimited source of rabbit mAbs.

Receptor tyrosine kinase expression and phosphorylation in canine nasal carcinoma

Preliminary studies have supported use of toceranib phosphate (Palladia®) in treatment of canine nasal carcinomas, though the mechanisms of its activity are unknown. This study evaluated sixteen canine nasal carcinoma and five normal nasal epithelium samples for expression and phosphorylation of known targets of toceranib [vascular endothelial growth factor receptor-2 (VEGR2), platelet derived growth factor alpha (PDGFR-α), platelet derived growth factor receptor beta (PDGFR-β), and stem cell factor receptor (c-KIT)] and epidermal growth factor receptor 1 (EGFR1) using immunohistochemistry, RT-PCR and a receptor tyrosine kinase (RTK) phosphorylation panel. Protein for VEGFR2 was expressed in all carcinomas, PDGFR-α was noted in 15/16, whereas PDGFR-β was detected in 3/16 samples, but showed significant stromal staining. Protein expression for c-KIT was present in 4/16 and EGFR1 was noted in 14/16 samples. Normal tissue showed variable protein expression of the RTKs. Messenger RNA for VEGFR2, PDGFR-β, and c-KIT were noted in all samples. Messenger RNA for PDGFR-α and EGFR1 were detected in 15/16 samples. All normal nasal tissue detected messenger RNA. Phosphorylation of VEGFR2, PDGFR-α, PDGFR-β and c-KIT was not observed in any carcinoma or normal nasal sample, but phosphorylation of EGFR1 was noted in 10/16 carcinoma and 3/5 normal samples. The absence of phosphorylated RTK targets of toceranib suggests any clinical effect of toceranib occurs through inhibition of alternative unidentified RTK pathways in canine nasal carcinomas. The observed protein and message expression and phosphorylation of EGFR1 in the nasal carcinoma samples merits further inquiry into EGFR1 as a therapeutic target for this cancer.

MicroRNA-93 promotes cell proliferation by directly targeting P21 in osteosarcoma cells

MicroRNAs (miRNAs) are small, non-coding RNAs that are key regulators of gene expression by directly binding to the 3'-untranslated region of their target mRNAs, resulting in translational repression or degradation of mRNA. It has been demonstrated that miRNAs have key roles in a variety of human malignancies, including osteosarcoma. The present study aimed to assess the molecular mechanism of miR-93 in the regulation of osteosarcoma cell proliferation. Reverse-transcription quantitative PCR and western blot assays were used to examine mRNA and protein expression. An MTT assay and flow cytometry were performed to determine the cell proliferation and cell cycle distribution. A luciferase reporter assay was performed to confirm the direct targeting of cyclin-dependent kinase inhibitor 1A (CDKN1A), also known as P21, by miR-93, which was suggested by a bioinformatics analysis. The results showed that the expression of miR-93 was frequently and significantly increased in a total of 19 osteosarcoma tissues compared to their matched adjacent non-tumor tissues, and the upregulation of miR-93 was associated with the malignant progression of osteosarcoma. Furthermore, miR-93 was also upregulated in the human osteosarcoma cell lines Saos-2, U2OS, SW1353 and MG63 when compared with that in the human osteoblast cell line hFOB1.19. Transfection with miR-93 inhibitor significantly reduced the miR-93 levels and inhibited the proliferation of U2OS and MG63 osteosarcoma cells. The protein levels of P21 were negatively regulated by miR-93 in U2OS and MG63 cells. Knockdown of miR-93 caused cell cycle arrest at G1 stage in U2OS and MG63 cells, identical to the effect of P21 overexpression. Finally, P21 was found to be significantly downregulated in osteosarcoma tissues compared to their matched adjacent non-tumor tissues, suggesting that the inhibition of P21 may be due to increased miR-93 expression in osteosarcoma tissues. In conclusion, the present study demonstrated that miR-93 enhances the proliferation of osteosarcoma cells, at least in part via inhibiting P21 expression and thus promoting cell cycle progression.

Ror2, a Developmentally Regulated Kinase, Is Associated With Tumor Growth, Apoptosis, Migration, and Invasion in Renal Cell Carcinoma

Renal cell carcinoma (RCC) represents one of the most resistant tumors to radiation and chemotherapy. Current therapies for RCC patients are inefficient due to the lack of diagnostic and therapeutic markers. The expression of novel tumor-associated kinases has the potential to dramatically shape tumor cell behavior. Identifying tumor-associated kinases can lend insight into patterns of tumor growth and characteristics. In the present study, we investigated the receptor tyrosine kinase-like orphan receptor 2 (Ror2), a new tumor-associated kinase, in RCC primary tumors and cell lines. Knockdown of Ror2 expression in RCC cells with specific shRNA significantly reduced cell proliferation and induced apoptosis. Using in vitro migration and Matrigel invasion assays, we found that cell migration and invasive ability were also significantly inhibited. In RCC, Ror2 expression correlated with expression of genes involved at the cell cycle and migration, including PCNA, CDK1, TWIST, and MMP-2. Furthermore, in vivo xenograft studies in nude mice revealed that administration of a Ror2 shRNA plasmid significantly inhibited tumor growth. These findings suggest a novel pathway of tumor-promoting activity by Ror2 within renal carcinomas, with significant implications for unraveling the tumorigenesis of RCC.

Wnt5a Increases Properties of Lung Cancer Stem Cells and Resistance to Cisplatin through Activation of Wnt5a/PKC Signaling Pathway

The development of chemoresistance to cisplatin regimens causes a poor prognosis in patients with advanced NSCLC. The role of noncanonical Wnt signaling in the regulation of properties of lung cancer stem cells and chemoresistance was interrogated, by accessing capacities of cell proliferation, migration, invasion, and clonogenicity as well as the apoptosis in A549 cell lines and cisplatin-resistant A549 cells treated with Wnt5a conditional medium or protein kinase C (PKC) inhibitor GF109203X. Results showed that the noncanonical Wnt signaling ligand, Wnt5a, could promote the proliferation, migration, invasion, and colony formation in A549 lung adenocarcinoma cells and cisplatin-resistant A549/DDP cells and increase the fraction of ALDH-positive cell in A549/DDP cells. An exposure of cells to Wnt5a led to a significant reduction of A549/DDP cell apoptosis but not A549 cells. An addition of GF109203X could both strikingly increase the baseline apoptosis and resensitize the Wnt5a-inhibited cell apoptosis. Interestingly, an inhibition of Wnt/PKC signaling pathway could reduce properties of lung cancer stem cells, promote cell apoptosis, and resensitize cisplatin-resistant cells to cisplatin via a caspase/AIF-dependent pathway. These data thus suggested that the Wnt5a could promote lung cancer cell mobility and cisplatin-resistance through a Wnt/PKC signaling pathway and a blockage of this signaling may be an alternative therapeutic strategy for NSCLC patients with resistance to chemotherapies.

Wnt signaling as potential therapeutic target in lung cancer

INTRODUCTION

Wingless-type (Wnt) signaling is tightly regulated at multiple cellular levels and is dysregulated in lung cancer. Therefore, it offers therapeutic targets for developing novel agents for lung cancer treatment.

AREAS COVERED

In this article, we discuss the role of the Wnt signaling pathway in lung cancer, highlighting the aberrant activation of Wnt in lung cancer stem cells and its implication in resistance to radiotherapy, chemotherapy and targeted therapy. We also expound the regulatory roles of microRNAs in Wnt signaling, as well as the potential of the Wnt pathway to provide biomarkers and therapeutic targets in lung cancer. The potential use of small molecule and biological inhibitors targeting the Wnt pathway for lung cancer therapy and prevention is also discussed.

EXPERT OPINION

Wnt signaling plays an important role in the development and metastasis of lung cancer; the pathway provides targets to develop agents towards for cancer prevention and therapy. A number of clinical trials have shown the effectiveness of Wnt pathway inhibitors in epithelial tumors. However, the side effects should be considered. Nevertheless, the results from clinical studies suggest that inhibitors targeting the Wnt signaling show promise against lung cancer.

ROR2 is epigenetically inactivated in the early stages of colorectal neoplasia and is associated with proliferation and migration

BACKGROUND

Colorectal cancer (CRC) is closely linked to Wnt signalling, with 94 % of cases exhibiting a Wnt related mutation. ROR2 is a receptor tyrosine kinase that is thought to repress β-catenin dependent Wnt signalling. Our study aims to determine if ROR2 is epigenetically silenced in CRC and determine if in vitro silencing of ROR2 potentiates Wnt signalling, and alters the proliferative, migratory or invasive potential of cells.

METHODS

ROR2 expression was examined in CRC cell lines and patient adenomas using qRT-PCR, while COBRA and bisulphite sequencing was used to analyse ROR2 promoter methylation. 258 patient primary tumour samples from publicly available databases were also examined for ROR2 expression and methylation. In addition, the functional effects of ROR2 modulation were investigated in HCT116 cells following ROR2 siRNA knockdown and in RKO and SW620 cells following ectopic ROR2 expression.

RESULTS

Reduced ROR2 expression was found to correlate with ROR2 promoter hypermethylation in colorectal cancer cell lines, carcinomas and adenomas. ROR2 expression was downregulated in 76.7 % (23/30) of CRC cell lines with increasing ROR2 promoter hypermethylation correlating with progressively lower expression. Analysis of 239 primary tumour samples from a publicly available cohort also found a significant correlation between reduced ROR2 expression and increased promoter methylation. Methylation analysis of 88 adenomas and 47 normal mucosa samples found greater percentage of adenoma samples to be methylated. Additional analysis also revealed that adenoma samples with reduced ROR2 expression also possessed ROR2 promoter hypermethylation. ROR2 knockdown in the CRC cell line HCT116 significantly decreased expression of the β-catenin independent Wnt targets genes JNK and NFATC1, increased cellular proliferation and migration but decreased invasion. When ROR2 was ectopically expressed in RKO and SW620 cells, there was no significant change to either cellular proliferation or migration.

CONCLUSION

ROR2 is frequently epigenetically inactivated by promoter hypermethylation in the early stages of colorectal neoplasia and this may contribute to colorectal cancer progression by increasing cellular proliferation and migration.

Wnt5a induces ROR1/ROR2 heterooligomerization to enhance leukemia chemotaxis and proliferation

Evolutionarily conserved receptor tyrosine kinase–like orphan receptor-1 and -2 (ROR1/2) are considered distinct receptors for Wnt5a and are implicated in noncanonical Wnt signaling in organogenesis and cancer metastasis. We found that Wnt5a enhanced proliferation and migration of chronic lymphocytic leukemia (CLL) cells and that these effects were blocked by the humanized anti-ROR1 mAb cirmtuzumab (UC-961). Treatment of CLL cells with Wnt5a induced ROR1 to oligomerize with ROR2 and recruit guanine exchange factors (GEFs), which activated Rac1 and RhoA; siRNA-mediated silencing of either ROR1 or ROR2 or treatment with UC-961 inhibited these effects. Using the ROR1-deficient CLL cell line MEC1, we demonstrated that ectopic ROR1 expression induced ROR1/ROR2 heterooligomers, which recruited GEFs, and enhanced proliferation, cytokine-directed migration, and engraftment potential of MEC1 cells in immune-deficient mice. Notably, treatment with UC-961 inhibited engraftment of ROR1+ leukemia cells in immune-competent ROR1-transgenic mice. Molecular analysis revealed that the extracellular Kringle domain is required for ROR1/ROR2 heterooligomerization and the cysteine-rich domain or intracellular proline-rich domain is required for Wnt5a-induced recruitment of GEFs to ROR1/ROR2. This study identifies an interaction between ROR1 and ROR2 that is required for Wnt5a signaling that promotes leukemia chemotaxis and proliferation.

The Caenorhabditis elegans Q neuroblasts: A powerful system to study cell migration at single-cell resolution in vivo

During development, cell migration plays a central role in the formation of tissues and organs. Understanding the molecular mechanisms that drive and control these migrations is a key challenge in developmental biology that will provide important insights into disease processes, including cancer cell metastasis. In this article, we discuss the Caenorhabditis elegans Q neuroblasts and their descendants as a tool to study cell migration at single-cell resolution in vivo. The highly stereotypical migration of these cells provides a powerful system to study the dynamic cytoskeletal processes that drive migration as well as the evolutionarily conserved signaling pathways (including different Wnt signaling cascades) that guide the cells along their specific trajectories. Here, we provide an overview of what is currently known about Q neuroblast migration and highlight the live-cell imaging, genome editing, and quantitative gene expression techniques that have been developed to study this process.

MicroRNA-205 acts as a tumor suppressor in osteosarcoma via targeting RUNX2

MicroRNAs (miRs) are a class of small non-coding RNAs, and negatively regulate gene expression through directly binding to the 3'-untranslational region (UTR) of their target mRNA, which further leads to translational repression or mRNA degradation. Recently, various miRs have been implicated in the development and progression of osteosarcoma (OS). However, the underlying mechanism has not been fully uncovered. Our study aimed to reveal the exact role of miR-205 in OS, as well as the regulatory mechanism. In this study, we found that the expression of miR-205 was significantly reduced in a total of 34 OS tissue specimens compared to their matched adjacent normal tissues. Besides, it was also remarkably downregulated in OS cell lines (Saos-2, U2OS, SW1353, and MG63) compared to human osteoblast hFOB1.19 cells. Overexpression of miR-205 caused a significant decrease in the proliferation, migration and invasion of MG63 and U2OS cells. Runt-related transcription factor 2 (RUNX2) was further identified as a target gene of miR-205. Moreover, the mRNA and protein expression of RUNX2 was reduced after miR-205 overexpression, but increased after knockdown of miR-205 in MG63 and U2OS cells. Furthermore, overexpression of RUNX2 effectively reversed the suppressive effect of miR-205 on the proliferation, migration, and invasion of MG63 and U2OS cells. The RUNX2 level was significantly increased in OS tissues compared to their matched adjacent normal tissues, as well as in OS cell lines compared to hFOB1.19 cells. In addition, the RUNX2 level was reversely correlated with the miR-205 level in OS tissues. Taken together, our data demonstrate that miR-205 acts as a tumor suppressor in OS via directly targeting RUNX2. Therefore, we suggest that the miR-205/RUNX2 axis may serve as a potential target for the treatment of OS.

Nucleotide-binding mechanisms in pseudokinases

Pseudokinases are classified by the lack of one or several of the highly conserved motifs involved in nucleotide (nt) binding or catalytic activity of protein kinases (PKs). Pseudokinases represent ∼10% of the human kinome and they are found in all evolutionary classes of kinases. It has become evident that pseudokinases, which were initially considered somewhat peculiar dead kinases, are important components in several signalling cascades. Furthermore, several pseudokinases have been linked to human diseases, particularly cancer, which is raising interest for therapeutic approaches towards these proteins. The ATP-binding pocket is a well-established drug target and elucidation of the mechanism and properties of nt binding in pseudokinases is of significant interest and importance. Recent studies have demonstrated that members of the pseudokinase family are very diverse in structure as well as in their ability and mechanism to bind nts or perform phosphoryl transfer reactions. This diversity also precludes prediction of pseudokinase function, or the importance of nt binding for said function, based on primary sequence alone. Currently available data indicate that ∼40% of pseudokinases are able to bind nts, whereas only few are able to catalyse occasional phosphoryl transfer. Pseudokinases employ diverse mechanisms to bind nts, which usually occurs at low, but physiological, affinity. ATP binding serves often a structural role but in most cases the functional roles are not precisely known. In the present review, we discuss the various mechanisms that pseudokinases employ for nt binding and how this often low-affinity binding can be accurately analysed.

Knockdown of receptor tyrosine kinase-like orphan receptor 2 inhibits cell proliferation and colony formation in osteosarcoma cells by inducing arrest in cell cycle progression

Osteosarcoma (OS) is the most common malignant tumor of the bone, with a high mortality rate and poor prognosis. Receptor tyrosine kinase-like orphan receptor 2 (ROR2) has been reported to be dysregulated in human malignancies. More recently, ROR2 has been demonstrated to promote OS cell migration and invasion. However, the role of ROR2 in the regulation of OS cell proliferation, as well as the underlying molecular mechanism, remains unclear. The present study aimed to investigate the underlying mechanism of ROR2 in osteosarcoma growth. Reverse transcription-quantitative polymerase chain reaction analysis and western blot analysis were used to examine the mRNA and protein expression. MTT assay, colony formation assay and cell cycle analysis were conducted to explore the function of ROR2 in osteosarcoma cells. In the present study, the expression of ROR2 was found to be frequently upregulated in OS tissues compared with matched adjacent normal tissues. It was also upregulated in the OS cell lines Saos-2, MG-63 and U-2 OS, relative to normal osteoblast hFOB 1.19 cells. Knockdown of ROR2 expression by transfection with ROR2-specific siRNA markedly inhibited the proliferation and colony formation of OS cells. Data from the cell cycle distribution assay revealed an accumulation of ROR2-knockdown cells in the G0/G1 phase, indicating that knockdown of ROR2 leads to an arrest in cell cycle progression. Mechanistic investigation revealed that the protein levels of c-myc, a target gene of the Wnt signaling, as well as cyclin D1, cyclin E and cyclin-dependent kinase 4 were markedly reduced in the ROR2-knockdown OS cells, suggesting that the inhibitory effect of ROR2 knockdown on OS cell proliferation is associated with the Wnt signaling pathway. In summary, the current study indicates an important role for ROR2 in the proliferation of OS cells. Therefore, ROR2 may be a promising therapeutic target in OS.

Receptor tyrosine kinase expression of circulating tumor cells in small cell lung cancer

Small cell lung cancer (SCLC) has a poor prognosis and is found disseminated at first presentation in the majority of cases. The cell biological mechanisms underlying metastasis and drug resistance are not clear. SCLC is characterized by high numbers of circulating tumor cells (CTCs) and we were able to expand several CTC lines ex vivo and to relate chitinase-3-like-1/YKL-40 (CHI3L1) as marker. Availability of expanded SCLC CTC cells allowed for a screening of receptor tyrosine kinases (RTKs) expressed. The metastatic CHI3L1-negative SCLC cell line SCLC26A, established from a pleural effusion was used for comparison. The CTC cell line BHGc10 was found to exhibit increased expression of RYK, AXL, Tie-1, Dtk, ROR1/2, several ephrins (Eph) and FGF/EGF receptors compared to SCLC26A. All of these RTKs have been associated with cell motility, invasion and poor prognosis in diverse cancer entities without knowledge of their association with CTCs. The identification of RYK, AXL and ROR1/2 as pseudokinases, lacking activity, seems to be related to the observed failure of RTK inhibitors in SCLC. These kinases are involved in the noncanonical WNT pathway and their expression in SCLC CTCs represents a cancer stem cell-like phenotype.