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

Receptor tyrosine kinase-like orphan receptor serves as a potential target in cancer immunotherapy

Receptor tyrosine kinase-like orphan receptor (ROR), consisting of ROR1 and ROR2, is a conserved family of receptor tyrosine kinase superfamily that plays crucial roles during embryonic development with limited expression in adult normal tissues. However, it is overexpressed in a range of hematological malignancies and solid tumors and functions in cellular processes including cell survival, polarity, and migration, serving as a potential target in cancer immunotherapy. This review summarizes the expression and structure of ROR in developmental morphogenesis and its function in cancers associated with Wnt5a signaling and highlights the cancer immunotherapy strategies targeting ROR.

Novel Targets and Advanced Therapies in Diffuse Large B Cell Lymphomas

Since the introduction of rituximab in the late 1990s, significant progress has been made in advancing targeted therapies for B cell lymphomas, improving patients' chance of being cured and clinicians' therapeutic armamentarium. A better understanding of disease biology and pathogenic pathways, coupled with refinements in immunophenotypic and molecular diagnostics, have been instrumental in these achievements. While traditional chemotherapy remains fundamental in most cases, concerns surrounding chemorefractoriness and cumulative toxicities, particularly the depletion of the hemopoietic reserve, underscore the imperative for personalized treatment approaches. Integrating targeted agents, notably monoclonal antibodies, alongside chemotherapy has yielded heightened response rates and prolonged survival. A notable paradigm shift is underway with innovative-targeted therapies replacing cytotoxic drugs, challenging conventional salvage strategies like stem cell transplantation. This review examines the landscape of emerging targets for lymphoma cells and explores innovative therapies for diffuse large B cell lymphoma (DLBCL). From Chimeric Antigen Receptor-T cells to more potent monoclonal antibodies, antibody-drug conjugates, bispecific antibodies, checkpoint inhibitors, and small molecules targeting intracellular pathways, each modality offers promising avenues for therapeutic advancement. This review aims to furnish insights into their potential implications for the future of DLBCL treatment strategies.

Enhancement of targeted therapy in combination with metformin on human breast cancer cell lines

BACKGROUND

Breast cancer remains a primary global health concern due to its limited treatment options, frequent disease recurrence, and high rates of morbidity and mortality. Thereby, there is a need for more effective treatment approaches. The proposal suggests that the combination of targeted therapy with other antitumoral agents could potentially address drug resistance. In this study, we examined the antitumoral effect of combining metformin, an antidiabetic drug, with targeted therapies, including tamoxifen for estrogen receptor-positive (MCF-7), trastuzumab for HER2-positive (SKBR-3), and antibody against ROR1 receptor for triple-negative breast cancer (MDA-MB-231).

METHODS

Once the expression of relevant receptors on each cell line was confirmed and appropriate drug concentrations were selected through cytotoxicity assays, the antitumor effects of both monotherapy and combination therapy on colony formation, migration, invasion were assessed in in vitro as well as tumor area and metastatic potential in ex ovo Chick chorioallantoic membrane (CAM) models.

RESULTS

The results exhibited the enhanced effects of tamoxifen when combined with targeted therapy. This combination effectively inhibited cell growth, colony formation, migration, and invasion in vitro. Additionally, it significantly reduced tumor size and metastatic potential in an ex ovo CAM model.

CONCLUSIONS

The findings indicate that a favorable strategy to enhance the efficacy of breast cancer treatment would be to combine metformin with targeted therapies.

Receptor tyrosine kinase-like orphan receptor 1 inhibitor strictinin exhibits anti-cancer properties against highly aggressive androgen-independent prostate cancer

Aim

It is important to identify anti-cancer compounds that can inhibit specific molecular targets to eradicate androgen-receptor negative (ARneg), androgen-independent (AI) prostate cancer, which is an aggressive form of prostate cancer with limited treatment options. The goal of this study was to selectively target prostate cancer cells that have high levels of oncogenic protein Receptor tyrosine kinase-like orphan receptor 1 (ROR1) by using strictinin, a small molecule ROR1 inhibitor.

Methods

The methods performed in this study include western blots, methyl thiazolyl tetrazolium (MTT) proliferation assays, phosphatidylserine apoptosis assays, apoptosis flow cytometry (Annexin V, caspase 3/7), migration scratch assays, Boyden chamber invasion assays, and cell cycle flow cytometry.

Results

Strictinin was most lethal against PC3 [half-maximal drug inhibitory concentration (IC50) of 277.2 µmol/L], an ARneg-AI cell type that expresses the highest levels of ROR1. Strictinin inhibited ROR1 expression, downstream phosphatidylinositol 3-kinase (PI3K)-protein kinase B (AKT)-glycogen synthase kinase 3beta (GSK3β) pro-survival signaling, and epithelial-to-mesenchymal transition markers in PC3 cells. Additionally, strictinin decreased PC3 cell migration and invasion, while increasing S-phase cell cycle arrest. In ARneg-AI DU145 cells, strictinin inhibited ROR1 expression and modulated downstream AKT-GSK3β signaling. Furthermore, strictinin exhibited anti-migratory, anti-invasive, but minimal pro-apoptotic effects in DU145 cells likely due to DU145 having less ROR1 expression in comparison to PC3 cells. Throughout the study, strictinin minimally impacted the phenotype of normal prostatic epithelial cells RWPE-1 (IC50 of 658.5 µmol/L). Strictinin was further identified as synergistic with docetaxel [combination index (CI) = 0.311] and the combination therapy was found to reduce the IC50 of strictinin to 38.71 µmol/L in PC3 cells.

Conclusions

ROR1 is an emerging molecular target that can be utilized for treating prostate cancer. The data from this study establishes strictinin as a potential therapeutic agent that targets ARneg-AI prostate cancer with elevated ROR1 expression to reduce the migration, invasion, cell cycle progression, and survival of prostate cancer.

ROR1-AS1 might promote in vivo and in vitro proliferation and invasion of cholangiocarcinoma cells

Long non-coding RNAs (lncRNAs) play important roles in many pathophysiological processes, including cancer progression. Namely, lncRNA Receptor-tyrosine-kinase-like orphan receptor-1 antisense 1 (ROR1-AS1) is crucial for cancer occurrence and progression in organs such as the liver or bladder. However, its expression and role in cholangiocarcinoma (CCA) have not been thoroughly explored.Firstly, we assessed cell viability, proliferation, invasion, and migration using three cell lines (HuCCT-1, QBC399, and RBE) to explore the biological characteristics of ROR1-AS1 in CCA. Secondly, to determine the in vivo effect of ROR1-AS1 on tumor growth, ROR1-AS1 knockdown (KD) HuCCT-1 cells were subcutaneously injected into nude mice to evaluate tumor growth. Finally, we conducted a bioinformatic analysis to confirm the role of ROR1-AS1 in the prognosis and immunity of CCA.In this study, we found that lncRNA ROR1-AS1 was increased in CCA samples and patients with higher ROR1-AS1 expression had a shorter overall survival period. siRNA-mediated KD of ROR1-AS1 significantly reduced cell proliferation and inhibited the migration of CCA cells. In addition, ROR1-AS1 KD HuCCT-1 cells injected into nude mice grew slower than normal CCA cells.In summary, our results show that ROR1-AS1 can promote CCA progression and might serve as a new target for diagnosis and treatment of CCA.

Beyond Bruton's tyrosine kinase inhibitors in mantle cell lymphoma: bispecific antibodies, antibody-drug conjugates, CAR T-cells, and novel agents

Mantle cell lymphoma is a B cell non-Hodgkin lymphoma (NHL), representing 2-6% of all NHLs and characterized by overexpression of cyclin D1. The last decade has seen the development of many novel treatment approaches in MCL, most notably the class of Bruton's tyrosine kinase inhibitors (BTKi). BTKi has shown excellent outcomes for patients with relapsed or refractory MCL and is now being studied in the first-line setting. However, patients eventually progress on BTKi due to the development of resistance. Additionally, there is an alteration in the tumor microenvironment in these patients with varying biological and therapeutic implications. Hence, it is necessary to explore novel therapeutic strategies that can be effective in those who progressed on BTKi or potentially circumvent resistance. In this review, we provide a brief overview of BTKi, then discuss the various mechanisms of BTK resistance including the role of genetic alteration, cancer stem cells, tumor microenvironment, and adaptive reprogramming bypassing the effect of BTK inhibition, and then provide a comprehensive review of current and emerging therapeutic options beyond BTKi including novel agents, CAR T cells, bispecific antibodies, and antibody-drug conjugates.

Targeting ROR1 Inhibits Glucocorticoid-induced Gastric Cancer Metastasis

Glucocorticoids are commonly used in clinic but are also a double-edged sword. While treating tumors, they are reported to promote tumor growth and metastasis. To explore the role and elucidate the mechanism of dexamethasone in promoting tumor growth and metastasis, we detected the levels of cortisol and adrenocorticotropic hormone (ACTH) in peripheral blood of patients with gastric cancer, and immunohistochemical staining was used to detect the expression of GR and ROR1 in the surgically resected gastric cancer samples. The levels of cortisol and ACTH in peripheral blood of patients with stage III and IV gastric cancer were higher than those of patients with stage I/II gastric cancer. Dexamethasone up-regulated the ROR1 level on gastric cancer cell lines in a concentration-dependent manner. Gastric cancer specimen with high ROR1 had higher rates of relapse and metastasis than gastric adenocarcinomas expressing low levels of ROR1.Gastric cancer patients with high expression of ROR1 had a short survival time. ROR1 was expressed by gastric cancer cell lines, but not on normal gastric epithelial cell line. Suppressing ROR1 in gastric cancer cell lines impaired their invasion, migration, scratch healing and clone formation ability in vitro and slowed down the tumor growth of MKN-45 cells in immunodeficient mice in vivo. Collectively, our study indicated that dexamethasone up-regulated ROR1 levels on gastric cancer cells. ROR1 participated in and mediated the role of dexamethasone in promoting gastric tumor growth, and blocking ROR1 can prevent the tumor growth.

A Small Molecule Targeting the Intracellular Tyrosine Kinase Domain of ROR1 (KAN0441571C) Induced Significant Apoptosis of Non-Small Cell Lung Cancer (NSCLC) Cells

The ROR1 receptor tyrosine kinase is expressed in embryonic tissues but is absent in normal adult tissues. ROR1 is of importance in oncogenesis and is overexpressed in several cancers, such as NSCLC. In this study, we evaluated ROR1 expression in NSCLC patients (N = 287) and the cytotoxic effects of a small molecule ROR1 inhibitor (KAN0441571C) in NSCLC cell lines. ROR1 expression in tumor cells was more frequent in non-squamous (87%) than in squamous (57%) carcinomas patients, while 21% of neuroendocrine tumors expressed ROR1 (p = 0.0001). A significantly higher proportion of p53 negative patients in the ROR1+ group than in the p53 positive non-squamous NSCLC patients (p = 0.03) was noted. KAN0441571C dephosphorylated ROR1 and induced apoptosis (Annexin V/PI) in a time- and dose-dependent manner in five ROR1+ NSCLC cell lines and was superior compared to erlotinib (EGFR inhibitor). Apoptosis was confirmed by the downregulation of MCL-1 and BCL-2, as well as PARP and caspase 3 cleavage. The non-canonical Wnt pathway was involved. The combination of KAN0441571C and erlotinib showed a synergistic apoptotic effect. KAN0441571C also inhibited proliferative (cell cycle analyses, colony formation assay) and migratory (scratch wound healing assay) functions. Targeting NSCLC cells by a combination of ROR1 and EGFR inhibitors may represent a novel promising approach for the treatment of NSCLC patients.

Non-canonical WNT5A-ROR signaling: New perspectives on an ancient developmental pathway

Deciphering non-canonical WNT signaling has proven to be both fascinating and challenging. Discovered almost 30 years ago, non-canonical WNT ligands signal independently of the transcriptional co-activator β-catenin to regulate a wide range of morphogenetic processes during development. The molecular and cellular mechanisms that underlie non-canonical WNT function, however, remain nebulous. Recent results from various model systems have converged to define a core non-canonical WNT pathway consisting of the prototypic non-canonical WNT ligand, WNT5A, the receptor tyrosine kinase ROR, the seven transmembrane receptor Frizzled and the cytoplasmic scaffold protein Dishevelled. Importantly, mutations in each of these signaling components cause Robinow syndrome, a congenital disorder characterized by profound tissue morphogenetic abnormalities. Moreover, dysregulation of the pathway has also been linked to cancer metastasis. As new knowledge concerning the WNT5A-ROR pathway continues to grow, modeling these mutations will likely provide crucial insights into both the physiological regulation of the pathway and the etiology of WNT5A-ROR-driven diseases.

CAR Based Immunotherapy of Solid Tumours-A Clinically Based Review of Target Antigens

Immunotherapy with CAR-engineered immune cells has transformed the management of selected haematological cancers. However, solid tumours have proven much more difficult to control using this emerging therapeutic modality. In this review, we survey the clinical impact of solid tumour CAR-based immunotherapy, focusing on specific targets across a range of disease indications Among the many candidates which have been the subject of non-clinical CAR T-cell research, clinical data are available for studies involving 30 of these targets. Here, we map out this clinical experience, highlighting challenges such as immunogenicity and on-target off-tumour toxicity, an issue that has been both unexpected and devastating in some cases. We also summarise how regional delivery and repeated dosing have been used in an effort to enhance impact and safety. Finally, we consider how emerging armouring systems and multi-targeted CAR approaches might be used to enhance tumour access and better enable discrimination between healthy and transformed cell types.

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.

ROR1-targeting switchable CAR-T cells for cancer therapy

The success of chimeric antigen receptor T cell (CAR-T) therapy in the treatment of hematologic malignancies has prompted the development of numerous CAR-T technologies, including switchable CAR-T (sCAR-T) systems that combine a universal CAR-T with bispecific adapter proteins. Owing to their controllability and versatility, sCAR-Ts have received considerable attention. To explore the therapeutic utility of sCAR-Ts targeting the receptor tyrosine kinase ROR1, which is expressed in hematologic and solid malignancies, and to identify bispecific adaptor proteins that efficiently mediate universal CAR-T engagement, a panel of switches based on ROR1-targeting Fabs with different epitopes and affinities was compared in in vitro and in vivo models of ROR1-expressing cancers. For switches targeting overlapping or identical epitopes, potency correlated with affinity. Surprisingly, however, we identified a switch targeting a unique epitope with low affinity but mediating potent and selective antitumor activity in vitro and in vivo. Converted to a conventional CAR-T, the same anti-ROR1 mAb (324) outperformed a clinically investigated conventional CAR-T that is based on an anti-ROR1 mAb (R12) with ~200-fold higher affinity. Thus, demonstrating therapeutic utility on their own, sCAR-Ts also facilitate higher throughput screening for the identification of conventional CAR-T candidates for preclinical and clinical studies.

TLR/WNT: A Novel Relationship in Immunomodulation of Lung Cancer

The most frequent cause of death by cancer worldwide is lung cancer, and the 5-year survival rate is still very poor for patients with advanced stage. Understanding the crosstalk between the signaling pathways that are involved in disease, especially in metastasis, is crucial to developing new targeted therapies. Toll-like receptors (TLRs) are master regulators of the immune responses, and their dysregulation in lung cancer is linked to immune escape and promotes tumor malignancy by facilitating angiogenesis and proliferation. On the other hand, over-activation of the WNT signaling pathway has been reported in lung cancer and is also associated with tumor metastasis via induction of Epithelial-to-mesenchymal-transition (EMT)-like processes. An interaction between both TLRs and the WNT pathway was discovered recently as it was found that the TLR pathway can be activated by WNT ligands in the tumor microenvironment; however, the implications of such interactions in the context of lung cancer have not been discussed yet. Here, we offer an overview of the interaction of TLR-WNT in the lung and its potential implications and role in the oncogenic process.

Crystal structure of the kringle domain of human receptor tyrosine kinase-like orphan receptor 1 (hROR1)

Receptor tyrosine kinase-like orphan receptors (RORs) are monotopic membrane proteins belonging to the receptor tyrosine kinase (RTK) family. RTKs play a role in the control of most basic cellular processes, including cell proliferation, differentiation, migration and metabolism. New emerging roles for RORs in cancer progression have recently been proposed: RORs have been shown to be overexpressed in various malignancies but not in normal tissues, and moreover an abnormal expression level of RORs on the cellular surface is correlated with high levels of cytotoxicity in primary cancer cells. Monoclonal antibodies against the extracellular part of RTKs might be of importance to prevent tumor cell growth: targeting extracellular kringle domain molecules induces the internalization of RORs and decreases cell toxicity. Here, the recombinant production and crystallization of the isolated KRD of ROR1 and its high-resolution X-ray crystal structure in a P3121 crystal form at 1.4 Å resolution are reported. The crystal structure is compared with previously solved three-dimensional structures of kringle domains of human ROR1 and ROR2, their complexes with antibody fragments and structures of other kringle domains from homologous proteins.

Zilovertamab Vedotin Targeting of ROR1 as Therapy for Lymphoid Cancers

BACKGROUND: Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal protein present on many cancers. Zilovertamab vedotin (ZV) is an antibody–drug conjugate comprising a monoclonal antibody recognizing extracellular ROR1, a cleavable linker, and the anti-microtubule cytotoxin monomethyl auristatin E. METHODS: In this phase 1, first-in-human, dose-escalation study, we accrued patients with previously treated lymphoid cancers to receive ZV every 3 weeks until the occurrence of cancer progression or unacceptable toxicity had occurred. RESULTS: We enrolled 32 patients with tumor histologies of mantle cell lymphoma (MCL) (n=15), chronic lymphocytic leukemia (n=7), diffuse large B-cell lymphoma (DLBCL) (n=5), follicular lymphoma (n=3), Richter transformation lymphoma (n=1), or marginal zone lymphoma (n=1). Patients had received a median of four previous drug and/or cellular therapies. Starting dose levels were 0.5 (n=1), 1.0 (n=3), 1.5 (n=3), 2.25 (n=11), and 2.5 (n=14) mg per kg of body weight (mg/kg). Pharmacokinetic and pharmacodynamic data documented systemic ZV exposure and exposure-dependent ZV targeting of ROR1 on circulating tumor cells. As expected with an monomethyl auristatin E-containing antibody–drug conjugate, adverse events (AEs) included acute neutropenia and cumulative neuropathy resulting in a recommended ZV dosing regimen of 2.5 mg/kg every 3 weeks. No clinically concerning AEs occurred to suggest ROR1-mediated toxicities or nonspecific ZV binding to normal tissues. ZV induced objective tumor responses in 7 of 15 patients with MCL (47%; 4 partial and 3 complete) and in 3 of 5 patients with DLBCL (60%; 1 partial and 2 complete); objective tumor responses were not observed among patients with other tumor types. CONCLUSIONS: In heavily pretreated patients, ZV demonstrated no unexpected toxicities and showed evidence of antitumor activity, providing clinical proof of concept for selective targeting of ROR1 as a potential new approach to cancer therapy. (ClinicalTrials.gov number, NCT03833180.)

Perspectives on the development of antibody-drug conjugates targeting ROR1 for hematological and solid cancers

Antibody–drug conjugates (ADCs) are targeted therapeutics generated by conjugation of cytotoxic small molecules to monoclonal antibodies (mAbs) via chemical linkers. Due to their selective delivery of toxic payloads to antigen-positive cancer cells, ADCs demonstrate wider therapeutic indexes compared with conventional chemotherapy. After decades of intensive research and development, significant advances have been made in the field, leading to a total of 10 U.S. food and drug administration (FDA)-approved ADCs to treat cancer patients. Currently, ~80 ADCs targeting different antigens are under clinical evaluation for treatment of either hematological or solid malignancies. Notably, three ADCs targeting the same oncofetal protein, receptor tyrosine kinase like orphan receptor 1 (ROR1), have attracted considerable attention when they were acquired or licensed successively in the fourth quarter of 2020 by three major pharmaceutical companies. Apparently, ROR1 has emerged as an attractive target for cancer therapy. Since all the components of ADCs, including the antibody, linker and payload, as well as the conjugation method, play critical roles in ADC’s efficacy and performance, their choice and combination will determine how far they can be advanced. This review summarizes the design and development of current anti-ROR1 ADCs and highlights an emerging trend to target ROR1 for cancer therapy.

Bio-vehicles of cytotoxic drugs for delivery to tumor specific targets for cancer precision therapy

Abnormal structural and molecular changes in malignant tissues were thoroughly investigated and utilized to target tumor cells, hence rescuing normal healthy tissues and lowering the unwanted side effects as non-specific cytotoxicity. Various ligands for cancer cell specific markers have been uncovered and inspected for directional delivery of the anti-cancer drug to the tumor site, in addition to diagnostic applications. Over the past few decades research related to the ligand targeted therapy (LTT) increased tremendously aiming to treat various pathologies, mainly cancers with well exclusive markers. Malignant tumors are known to induce elevated levels of a variety of proteins and peptides known as cancer "markers" as certain antigens (e.g., Prostate specific membrane antigen "PSMA", carcinoembryonic antigen "CEA"), receptors (folate receptor, somatostatin receptor), integrins (Integrin αvβ3) and cluster of differentiation molecules (CD13). The choice of an appropriate marker to be targeted and the design of effective ligand-drug conjugate all has to be carefully selected to generate the required therapeutic effect. Moreover, since some tumors express aberrantly high levels of more than one marker, some approaches investigated targeting cancer cells with more than one ligand (dual or multi targeting). We aim in this review to report an update on the cancer-specific receptors and the vehicles to deliver cytotoxic drugs, including recent advancements on nano delivery systems and their implementation in targeted cancer therapy. We will discuss the advantages and limitations facing this approach and possible solutions to mitigate these obstacles. To achieve the said aim a literature search in electronic data bases (PubMed and others) using keywords "Cancer specific receptors, cancer specific antibody, tumor specific peptide carriers, cancer overexpressed proteins, gold nanotechnology and gold nanoparticles in cancer treatment" was carried out.

A Novel Treatment for Ewing's Sarcoma: Chimeric Antigen Receptor-T Cell Therapy

Ewing's sarcoma (EWS) is a malignant and aggressive tumor type that predominantly occurs in children and adolescents. Traditional treatments such as surgery, radiotherapy and chemotherapy, while successful in the early disease stages, are ineffective in patients with metastases and relapses who often have poor prognosis. Therefore, new treatments for EWS are needed to improve patient's outcomes. Chimeric antigen receptor (CAR)-T cells therapy, a novel adoptive immunotherapy, has been developing over the past few decades, and is increasingly popular in researches and treatments of various cancers. CAR-T cell therapy has been approved by the Food and Drug Administration (FDA) for the treatment of leukemia and lymphoma. Recently, this therapeutic approach has been employed for solid tumors including EWS. In this review, we summarize the safety, specificity and clinical transformation of the treatment targets of EWS, and point out the directions for further research.

Immunotherapy for lung cancer: Focusing on chimeric antigen receptor (CAR)-T cell therapy

Besides traditional treatment strategies, including surgery, radiotherapy, and chemotherapy for lung cancer as the leading cause of cancer incidence and death, immunotherapy has also emerged as a new treatment strategy. The goal of immunotherapy is to stimulate the immune system responses against cancer, using various approaches such as therapeutic vaccines, monoclonal antibodies, immune checkpoint inhibitors, and T-cell therapy. Chimeric antigen receptor (CAR)-T cells, one of the most popular cancer immunotherapy approaches in the last decade, are genetically engineered T-cells to redirect patients' immune responses to recognize and eliminate tumor-associated antigens (TAA)-expressing tumor cells. CAR-T cell therapy provides promising benefits in lung tumors. In this review, we summarize different immunotherapy approaches for lung cancer, the structure of CAR-T cells, currently undergoing CARs in clinical trials, and various TAAs are being investigated as potential targets in designing CAR-T cells for lung cancer.

A ROR1 small molecule inhibitor (KAN0441571C) induced significant apoptosis of ibrutinib-resistant ROR1+ CLL cells

ROR1 - a receptor tyrosine kinase - is overexpressed in CLL. Ibrutinib, a Bruton's tyrosine kinase inhibitor, is clinically effective in CLL but patients may develop resistance. We evaluated the effect of an ROR1 inhibitor, KAN0441571C, in CLL cells from six patients obtained before and after developing resistance to ibrutinib. The ROR1 inhibitor induced apoptosis in ibrutinib-resistant CLL cells to the same degree as in ibrutinib-sensitive cells and dephosphorylated ROR1. This was also noted in one patient who became resistant to both ibrutinib and the Bcl-2 inhibitor venetoclax. The combination of ROR1 inhibitor and venetoclax had a synergistic apoptotic effect on ibrutinib-resistant cells.

Ultrasensitive and label free electrochemical immunosensor for detection of ROR1 as an oncofetal biomarker using gold nanoparticles assisted LDH/rGO nanocomposite

In the present article, we developed a highly sensitive label-free electrochemical immunosensor based on NiFe-layered double hydroxides (LDH)/reduced graphene oxide (rGO)/gold nanoparticles modified glassy carbon electrode for the determination of receptor tyrosine kinase-like orphan receptor (ROR)-1. In this electrochemical immunoassay platform, NiFe-LDH/rGO was used due to great electron mobility, high specific surface area and flexible structures, while Au nanoparticles were prepared and coated on the modified electrodes to improve the detection sensitivity and ROR1 antibody immobilizing (ROR1Ab). The modification procedure was approved by using cyclic voltammetry and differential pulse voltammetry based on the response of peak current to the step by step modifications. Under optimum conditions, the experimental results showed that the immunosensor revealed a sensitive response to ROR1 in the range of 0.01-1 pg mL^-1, and with a lower limit of quantification of 10 attogram/mL (10 ag mL^-1). Furthermore, the designed immunosensor was applied for the analysis of ROR1 in several serum samples of chronic lymphocytic leukemia suffering patients with acceptable results, and it also exhibited good selectivity, reproducibility and stability.

Gastric Cancer: Identification of microRNAs Inhibiting Druggable Targets and Mediating Efficacy in Preclinical In Vivo Models

In addition to chemotherapy, targeted therapies have been approved for treatment of locally advanced and metastatic gastric cancer. The therapeutic benefit is significant but more durable responses and improvement of survival should be achieved. Therefore, the identification of new targets and new approaches for clinical treatment are of paramount importance. In this review, we searched the literature for down-regulated microRNAs which interfere with druggable targets and exhibit efficacy in preclinical in vivo efficacy models. As druggable targets, we selected transmembrane receptors, secreted factors and enzymes. We identified 38 microRNAs corresponding to the criteria as outlined. A total of 13 miRs target transmembrane receptors, nine inhibit secreted proteins and 16 attenuate enzymes. These microRNAs are targets for reconstitution therapy of gastric cancer. Further target validation experiments are mandatory for all of the identified microRNAs.

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.

Resistin: Potential biomarker and therapeutic target in atherosclerosis

Resistin, a cysteine-rich secretory protein, has a pleiotropic role in humans. Resistin usually presents as trimer or hexamer in plasma, and targets specific receptors Toll Like Receptor 4 (TLR4) or Adenylyl Cyclase-Associated Protein 1 (CAP1). Upon binding to TLR4 and CAP1, resistin can trigger various intracellular signal transduction pathways to induce vascular inflammation, lipid accumulation, and plaque vulnerability. These pro-atherosclerotic effects of resistin appear in various cell types, including endothelial cells, vessel smooth muscle cells and macrophages, which cause diverse damages to cardiovascular system from dyslipidemia, atherosclerosis rupture and ventricular remodeling. In this review, we gather recent evidence about the pro- atherosclerotic effects of resistin and highlight it as a candidate therapeutic or diagnostic target for cardiovascular disease.

The PI3K-AKT-mTOR Pathway and Prostate Cancer: At the Crossroads of AR, MAPK, and WNT Signaling

Oncogenic activation of the phosphatidylinositol-3-kinase (PI3K), protein kinase B (PKB/AKT), and mammalian target of rapamycin (mTOR) pathway is a frequent event in prostate cancer that facilitates tumor formation, disease progression and therapeutic resistance. Recent discoveries indicate that the complex crosstalk between the PI3K-AKT-mTOR pathway and multiple interacting cell signaling cascades can further promote prostate cancer progression and influence the sensitivity of prostate cancer cells to PI3K-AKT-mTOR-targeted therapies being explored in the clinic, as well as standard treatment approaches such as androgen-deprivation therapy (ADT). However, the full extent of the PI3K-AKT-mTOR signaling network during prostate tumorigenesis, invasive progression and disease recurrence remains to be determined. In this review, we outline the emerging diversity of the genetic alterations that lead to activated PI3K-AKT-mTOR signaling in prostate cancer, and discuss new mechanistic insights into the interplay between the PI3K-AKT-mTOR pathway and several key interacting oncogenic signaling cascades that can cooperate to facilitate prostate cancer growth and drug-resistance, specifically the androgen receptor (AR), mitogen-activated protein kinase (MAPK), and WNT signaling cascades. Ultimately, deepening our understanding of the broader PI3K-AKT-mTOR signaling network is crucial to aid patient stratification for PI3K-AKT-mTOR pathway-directed therapies, and to discover new therapeutic approaches for prostate cancer that improve patient outcome.

ROR1 Is Expressed in Diffuse Large B-Cell Lymphoma (DLBCL) and a Small Molecule Inhibitor of ROR1 (KAN0441571C) Induced Apoptosis of Lymphoma Cells

The receptor tyrosine kinase ROR1 is absent in most normal adult tissues, but overexpressed in several malignancies. In this study, we explored clinical and functional inhibitory aspects of ROR1 in diffuse large B-cell lymphoma (DLBCL). ROR1 expression in tumor cells was more often observed in primary refractory DLBCL, Richter’s syndrome and transformed follicular lymphoma than in relapsed and non-relapsed DLBCL patients (p < 0.001). A survival effect of ROR1 expression was preliminarily observed in relapsed/refractory patients independent of gender and stage but not of age, cell of origin and international prognostic index. A second generation small molecule ROR1 inhibitor (KAN0441571C) induced apoptosis of ROR1+ DLBCL cell lines, similar to venetoclax (BCL-2 inhibitor) but superior to ibrutinib (BTK inhibitor). The combination of KAN0441571C and venetoclax at EC₅₀ concentrations induced almost complete killing of DLBCL cell lines. Apoptosis was accompanied by the downregulation of BCL-2 and MCL-1 and confirmed by the cleavage of PARP and caspases 3, 8, 9. PI3Kδ/AKT/mTOR (non-canonical Wnt pathway) as well as β-catenin and CK1δ (canonical pathway) were inactivated. In zebra fishes transplanted with a ROR1+ DLBCL cell line, KAN0441571C induced a significant tumor reduction. New drugs with mechanisms of action other than those available for DLBCL are warranted. ROR1 inhibitors might represent a novel promising approach.

ROR1 regulates chemoresistance in Breast Cancer via modulation of drug efflux pump ABCB1

Chemoresistance is one of the leading causes of mortality in breast cancer (BC). Understanding the molecules regulating chemoresistance is critical in order to combat chemoresistant BC. Drug efflux pump ABCB1 is overexpressed in chemoresistant neoplasms where it effluxes various chemotherapeutic agents from cells. Because it is expressed in normal and cancerous cells alike, attempts at targeting ABCB1 directly have failed due to low specificity and disruption of normal tissue. A proposed method to inhibit ABCB1 is to target its cancer-specific, upstream regulators, mitigating damage to normal tissue. Few such cancer-specific upstream regulators have been described. Here we characterize ROR1 as an upstream regulator of ABCB1. ROR1 is highly expressed during development but not expressed in normal adult tissue. It is however highly expressed in several cancers. ROR1 is overexpressed in chemoresistant BC where it correlates with poor therapy response and tumor recurrence. Our data suggests, ROR1 inhibition sensitizes BC cells to chemo drugs. We also show ROR1 regulates ABCB1 stability and transcription via MAPK/ERK and p53. Validating our overall findings, inhibition of ROR1 directly correlated with decreased efflux of chemo-drugs from cells. Overall, our results highlight ROR1’s potential as a therapeutic target for multidrug resistant malignancies.

A fully chimeric IgG antibody for ROR1 suppresses ovarian cancer growth in vitro and in vivo

BACKGROUND

Over-expression of Receptor-tyrosine-kinase-like Orphan Receptor 1 (ROR1) in cancer cells has been reported in the context of several tumors (including ovarian cancer) and is associated with poor prognosis. The aim of this study was to construct a fully chimeric anti-ROR1 IgG antibody (ROR1-IgG) and investigate its antitumor activity against ovarian cancer cells, bothin vitro and in vivo.

METHODS

A fully chimeric anti-ROR1 IgG antibody (ROR1-IgG) eukaryotic expression vector was constructed and ROR1-IgG antibody was expressed in CHO cells. The characteristics of ROR1-IgG were investigated by ELISA, SPR, Western blotting, FACS and fluorescence staining analyses. CCK8 and wound healing assays were performed to determine inhibition and migration capacity of ovarian cancer cells after treatment with ROR1-IgGin vitro. Further, the antitumor activity of ROR1-IgG was assessed in vivo using tumor-mice xenograft model.

RESULTS

The results showed that ROR1-IgG could specifically bind to ROR1-positive cells (HO8910 and A2780) with a high affinity. Functional studies revealed that ROR1-IgG inhibited the malignant behavior of ROR1-positive cells (HO8910 and A2780) in a time- and dose-dependent manner. These effects were not observed in ROR1-negative lose386 cells. The tumor inhibition rates following treatment with low, medium, and high concentrations of ROR1-IgG were approximately 47.72%, 53.79%, and 60.51%, respectively. In addition, the expression of Bcl-2 was obviously reduced while that of Bax was distinctly elevated in xenografts.

CONCLUSIONS

Collectively, our findings suggest that ROR1-IgG may be a novel therapeutic agent for patients with ROR1-positive ovarian cancer.

Solution structure, dynamics and function investigation of Kringle domain of human receptor tyrosine kinase-like orphan receptor 1

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) has been recently proposed as a potential target for cancer treatment. It was suggested that monoclonal antibodies (mAb) against the Kringle (KNG) domain of ROR1 could induce apoptosis of chronic lymphocytic leukemia cells. Here, we reported the determination of the solution structure of human ROR1-KNG (hROR1-KNG), investigation of its dynamic properties and potential binding interface by NMR spectroscopy. The obtained NMR structure of hROR1-KNG exhibits an open form at Asn47-His50 and shows obvious differences from other canonical KNGs at the corresponding lysine binding site, which implies that hROR1-KNG may interact with some non-canonical ligands. Dynamics analysis of hROR1-KNG reveal a faster local motion around the α-turn and 3₁₀-helix, which may provide flexibility to protect the proximal hydrophobic core in solution or facilitate the binding of other molecules. The intermediate-to-slow conformational exchange of Cys77-Ile79 may influence the conformation determination of disulfide bond Cys53-Cys77. Binding interface of hROR1-KNG for mAb R11 was analyzed and compared with the epitope for the functional mAbs. Previous study implies that hROR1-KNG may be involved in mediating the heterooligomerization between ROR1 and ROR2 in vivo. However, apparently, no direct interaction between hROR1-KNG and hROR2-KNG was observed from chemical shift perturbation experiment. Our work lays foundation to further functional study on interactions of hROR1-KNG with other biological relevant partners.Communicated by Ramaswamy H. Sarma.

Design, Synthesis, and Biological Evaluation of Novel Biotinylated Podophyllotoxin Derivatives as Potential Antitumor Agents

Podophyllotoxin has long been used as an active substance for cytotoxic activity. Fourteen novel biotinylated podophyllotoxin derivatives were designed, synthesized, and evaluated for cytotoxic activity for this study. The synthesized compounds were evaluated for cytotoxic activity in the following human cancer cell lines, SW480, MCF-7, A-549, SMMC-7721, and HL-60 by MTT assay. Most of them exhibited potent cytotoxic effects and compound 15 showed the highest cytotoxic activity among the five cancer cell lines tested, having its IC50 values in the range of 0.13 to 0.84 μM. Apoptosis analysis revealed that compound 15 caused obvious induction of cell apoptosis. Compound 15 significantly down-regulated the expression level of the marker proteins (caspase-3 and PARP) in H1299 and H1975 cells, activated the transcription of IRE1α, increased the expression of GRP78 and XBP-1s, and finally induced apoptosis of H1299 cells. In vivo studies showed that 15 at a dose of 20 mg/kg suppressed tumor growth of S180 cell xenografts in icr mice significantly. Further molecular docking studies suggested that compound 15 could bind well with the ATPase domain of Topoisomerase-II. These data suggest that compound 15 is a promising agent for cancer therapy deserving further research.

Novel ROR1 inhibitor ARI-1 suppresses the development of non-small cell lung cancer

Limited drug response and severe drug resistance confer the high mortality of non-small-cell lung cancer (NSCLC), a leading cause of cancer death worldwide. There is an urgent need for novel treatment against NSCLC. Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is aberrantly overexpressed and participats in NSCLC development and EGFR-TKIs-induced drug resistance. Increasing evidences indicate that oncogenic ROR1 is a potential target for NSCLC therapy. However, nearly no ROR1 inhibitor was reported until now. Here, combining the computer-aided drug design and cell-based activity screening, we discover (R)-5,7-bis(methoxymethoxy)-2-(4-methoxyphenyl)chroman-4-one (ARI-1) as a novel ROR1 inhibitor. Biological evaluation demonstrates that ARI-1 specifically targets the extracellular frizzled domain of ROR1 and potently suppresses NSCLC cell proliferation and migration by regulating PI3K/AKT/mTOR signaling in a ROR1-dependent manner. Moreover, ARI-1 significantly inhibits tumor growth in vivo without obvious toxicity. Intriguingly, ARI-1 is effective to EGFR-TKIs-resistant NSCLC cells with high ROR1 expression. Therefore, our work suggests that the ROR1 inhibitor ARI-1 is a novel drug candidate for NSCLC treatment, especially for EGFR-TKIs-resisted NSCLC with high ROR1 expression.

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.

ROR1 is highly expressed in circulating tumor cells and promotes invasion of pancreatic cancer

Pancreatic cancer (PaC) is an aggressive malignancy, which is associated with high levels of metastasis. Circulating tumor cells (CTCs), which may be considered a functional biomarker and promising treatment strategy for metastasis, are associated with the prognosis and progression of various metastatic cancers, including PaC. Receptor tyrosine kinase‑like orphan receptor 1 (ROR1) expression contributes to cell metastasis and poor clinical outcomes in malignant tumors. The present study aimed to explore the function of ROR1 in PaC CTCs. Reverse transcription‑quantitative polymerase chain reaction and western blot analysis were used to examine the expression of ROR1, E‑cadherin and N‑cadherin. Cell proliferative and invasive ability was assessed by MTT and Transwell assays, respectively. The results revealed that the mRNA and protein expression levels of ROR1 were augmented in PaC tissues. Furthermore, the mRNA expression levels of ROR1 were higher in CTCs compared with in peripheral blood cells, and ROR1 was more highly expressed in CTCs than in cells. Notably, CTCs exhibited a markedly greater proliferative and invasive capacity than PANC‑1 and SW‑1990 cells, whereas knockdown of endogenous ROR1 by small interfering RNA led to suppression of the invasion of CTCs. In addition, it was revealed that the mechanism underlying the effects of ROR1 on PaC CTC metastasis may involve the epithelial‑mesenchymal transition process. In conclusion, ROR1 may be considered a potential biomarker and therapeutic target for the treatment of PaC.

The expansion of targetable biomarkers for CAR T cell therapy

Biomarkers are an integral part of cancer management due to their use in risk assessment, screening, differential diagnosis, prognosis, prediction of response to treatment, and monitoring progress of disease. Recently, with the advent of Chimeric Antigen Receptor (CAR) T cell therapy, a new category of targetable biomarkers has emerged. These biomarkers are associated with the surface of malignant cells and serve as targets for directing cytotoxic T cells. The first biomarker target used for CAR T cell therapy was CD19, a B cell marker expressed highly on malignant B cells. With the success of CD19, the last decade has shown an explosion of new targetable biomarkers on a range of human malignancies. These surface targets have made it possible to provide directed, specific therapy that reduces healthy tissue destruction and preserves the patient's immune system during treatment. As of May 2018, there are over 100 clinical trials underway that target over 25 different surface biomarkers in almost every human tissue. This expansion has led to not only promising results in terms of patient outcome, but has also led to an exponential growth in the investigation of new biomarkers that could potentially be utilized in CAR T cell therapy for treating patients. In this review, we discuss the biomarkers currently under investigation and point out several promising biomarkers in the preclinical stage of development that may be useful as targets.

Multi-Compartment and Multi-Host Vector Suite for Recombinant Protein Expression and Purification

Recombinant protein expression has become an invaluable tool in basic and applied research. The accumulated knowledge in this field allowed the expression of thousands of protein targets in a soluble, pure, and homogeneous state, essential for biochemical and structural analyses. A lot of progress has been achieved in the last decades, where challenging proteins were expressed in a soluble manner after evaluating different parameters such as host, strain, and fusion partner or promoter strength, among others. In this regard, we have previously developed a vector suite that allows the evaluation of different promoters and solubility enhancer-proteins, through an easy and efficient cloning strategy. Nonetheless, the proper expression of many targets remains elusive, requiring, for example, the addition of complex post-translation modifications and/or passage through specialized compartments. In order to overcome the limitations found when working with a single subcellular localization and a single host type, we herein expanded our previously developed vector suite to include the evaluation of recombinant protein expression in different cell compartments and cell hosts. In addition, these vectors also allow the assessment of alternative purification strategies for the improvement of target protein yields.

A receptor tyrosine kinase ROR1 inhibitor (KAN0439834) induced significant apoptosis of pancreatic cells which was enhanced by erlotinib and ibrutinib

There is a great unmet medical need in pancreatic carcinoma (PC) for novel drugs with other mechanisms of action than existing. PC cells express the onco-fetal RTK ROR1, absent on most normal post-partem cells. ROR1 is involved in proliferation, survival, EMT and metastasis of tumor cells in various malignancies. A small molecule inhibitor (KAN0439834) (530 Da) targeting the TK domain of ROR1 was developed and the activity in ROR1 expressing human PC cell lines (n = 8) evaluated. The effects were compared to a murine mAb against the external part of ROR1, gemcitabine, erlotinib and ibrutinib. KAN0439834 induced significant apoptosis of the tumor cells. EC₅₀ values for KAN0439834 varied between 250–650 nM depending on the cell line. The corresponding values for erlotinib and ibrutinib were 10–40 folds higher. KAN0439834 was much more effective in inducing tumor cell death than the ROR1 mAb although both inhibited ROR1 phosphorylation and downstream non-canonical Wnt pathway molecules. Combination of KAN0439834 with erlotinib or ibrutinib had significant additive effects on tumor cell death. A first-in-class small molecule ROR1 inhibitor (KAN0439834) showed promising in vitro activity against a number of human PC cell lines. Interesting is the additive effects of erlotinib and ibrutinib which warrants further studies as both these agents are in clinical trials for pancreatic carcinoma.

Potent and selective antitumor activity of a T cell-engaging bispecific antibody targeting a membrane-proximal epitope of ROR1

T cell-engaging bispecific antibodies (biAbs) present a promising strategy for cancer immunotherapy, and numerous bispecific formats have been developed for retargeting cytolytic T cells toward tumor cells. To explore the therapeutic utility of T cell-engaging biAbs targeting the receptor tyrosine kinase ROR1, which is expressed by tumor cells of various hematologic and solid malignancies, we used a bispecific ROR1 × CD3 scFv-Fc format based on a heterodimeric and aglycosylated Fc domain designed for extended circulatory t_1/2 and diminished systemic T cell activation. A diverse panel of ROR1-targeting scFv derived from immune and naïve rabbit antibody repertoires was compared in this bispecific format for target-dependent T cell recruitment and activation. An ROR1-targeting scFv with a membrane-proximal epitope, R11, revealed potent and selective antitumor activity in vitro, in vivo, and ex vivo and emerged as a prime candidate for further preclinical and clinical studies. To elucidate the precise location and engagement of this membrane-proximal epitope, which is conserved between human and mouse ROR1, the 3D structure of scFv R11 in complex with the kringle domain of ROR1 was determined by X-ray crystallography at 1.6-Å resolution.

MHC class I presented antigens from malignancies: A perspective on analytical characterization & immunogenicity

The field of cancer immunotherapy has expanded rapidly in the past few years, with many new approaches entering the clinic for T cell mediated killing of tumors. Several of these clinical approaches involve the exploitation of a CD8 + T cell response against MHC I presented tumor antigens. Here, we describe the types of tumor antigens which are considered as targets in the design of T cell based therapeutic approaches, the rationale for targeting MHC I antigens and the analytical tools commonly employed for the discovery of MHC I presented peptides. The advantages and disadvantages of each approach are discussed and a perspective on the future directions of the MHC I peptide exploration field and biotherapeutic strategies is given. SIGNIFICANCE: This work is the first time a review article has been written to summarize all the various types of tumor antigens, and the analytical tools employed to discover and characterize them.

miR‑30a inhibits epithelial‑mesenchymal transition and metastasis in triple‑negative breast cancer by targeting ROR1

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype that lacks effective targeted therapies. In the present study, we revealed that the expression of miR-30a was significantly decreased in TNBC, and TNBC patients with low expression of miR-30a were associated with high histological grade and more lymph node metastasis. Moreover, we found that miR-30a suppressed TNBC cell epithelial-mesenchymal transition (EMT), as demonstrated by the overexpression of miR-30a which increased the expression of epithelial marker E-cadherin but decreased the expression of mesenchymal markers N-cadherin and vimentin. Furthermore, we demonstrated that overexpression of miR-30a significantly suppressed TNBC cell invasion and migration, as well as inhibited tumor growth and metastasis in vivo. More importantly, RTK-like orphan receptor 1 (ROR1) was predicted as the direct target of miR-30a, which was subsequently confirmed by luciferase assays. Forced expression of miR-30a in TNBC cells decreased ROR1 expression, whereas the overexpression of ROR1 reversed the suppressive effects of miR-30a in TNBC cell migration and invasion. Collectively, this study indicated that miR-30a functions as a tumor-metastasis suppressor miRNA in TNBC by directly targeting ROR1 and that miR-30a may serve as a novel therapeutic target for TNBC.

Twist promotes tumor metastasis in basal-like breast cancer by transcriptionally upregulating ROR1

Rationale: Twist is a key transcription factor for induction of epithelial-mesenchymal transition (EMT), which promotes cell migration, invasion, and cancer metastasis, confers cancer cells with stem cell-like characteristics, and provides therapeutic resistance. However, the functional roles and targeted genes of Twist in EMT and cancer progression remain elusive. Methods: The potential targeted genes of Twist were identified from the global transcriptomes of T47D/Twist cells by microarray analysis. EMT phenotype was detected by western blotting and immunofluorescence of marker proteins. The dual-luciferase reporter and chromatin immunoprecipitation assays were employed to observe the direct transcriptional induction of ROR1 by Twist. A lung metastasis model was used to study the pro-metastatic role of Twist and ROR1 by injecting MDA-MB-231 cells into tail vein of nude mice. Bio-informatics analysis was utilized to measure the metastasis-free survival of breast cancer patients. Results: Twist protein was proved to directly activate the transcription of ROR1 gene, a receptor of Wnt5a in non-canonical WNT signaling pathway. Silencing of ROR1 inhibited EMT process, cell migration, invasion, and cancer metastasis of basal-like breast cancer (BLBC) cells. Knockdown of ROR1 also ameliorated the pro-metastatic effect of Twist. Furthermore, analyses of clinical specimens indicated that high expression of both ROR1 and Twist tightly correlates with poor metastasis-free survival of breast cancer patients. Conclusion: ROR1 is a targeted gene of Twist. Twist/ROR1 signaling is critical for invasion and metastasis of BLBC cells.

Backbone and side-chain chemical shift assignments of the kringle domain of human receptor tyrosine kinase-like orphan receptor 1 (ROR1)

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) expresses at high level in many cancers and has been suggested as a potential therapeutic target. It was reported that the Kringle (KNG) domain of ROR1 extracellular region is involved in ROR1/ROR2 heterooligomerization. Monoantibodies that target KNG domain of ROR1 could induce apoptosis of chronic lymphocytic leukemia cells. Here we present the backbone and side chain assignments of KNG domain of ROR1, which lays a foundation for its further structural and function research.

ROR1 expression as a biomarker for predicting prognosis in patients with colorectal cancer

There is a lack of reliable prognosis biomarker in the current treatment of colorectal cancer. The receptor-tyrosine-kinase-like orphan receptor 1 (ROR1) is overexpressed and associated with poor prognosis in certain tumors. This study aimed to explore the prognostic significance of ROR1 in colorectal cancer. Western blot analysis and immunohistochemistry showed that the expression of ROR1 in colorectal cancer was significantly higher than that in the adjacent normal tissues. ROR1 expression was positively associated with the clinical stage and lymph-node metastasis (p < 0.01). Kaplan-Meier survival analysis revealed that patients with higher ROR1 expression had a significantly shorter overall survival (p < 0.01). Multivariate Cox regression analysis confirmed that ROR1 is an independent prognostic marker in colorectal cancer (p = 0.002, HR = 2.08, 95% CI: 1.314–3.292). Thus, our study demonstrated that ROR1 expression is correlated with malignant attributes and may serve as a novel prognostic marker and therapeutic target for colorectal cancer.

Investigation of the molecular mechanisms underlying postoperative recurrence in prostate cancer by gene expression profiling

The present study aimed to identify potential genes associated with prostate cancer (PCa) recurrence following radical prostatectomy (RP) in order to improve the prediction of the prognosis of patients with PCa. The GSE25136 microarray dataset, including 39 recurrent and 40 non-recurrent PCa samples, was downloaded from the Gene Expression Omnibus database. Differentially-expressed genes (DEGs) were identified using limma packages, and the pheatmap package was used to present the DEGs screened using a hierarchical cluster analysis. Furthermore, gene ontology functional enrichment analysis was used to predict the potential functions of the DEGs. Subsequently, Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed to analyze pathway enrichment of DEGs in the regulatory network. Lastly, a protein-protein interaction (PPI) network of the DEGs was constructed using Cytoscape software to understand the interactions between these DEGs. A total of 708 DEGs were identified in the recurrent and non-recurrent PCa samples. Functional annotation revealed that these DEGs were primarily involved in cell adhesion, negative regulation of growth, and the cyclic adenosine monophosphate and mitogen-activated protein kinase (MAPK) signaling pathways. Furthermore, five key genes, including cluster of differentiation 22, insulin-like growth factor-1, inhibin β A subunit, MAPK kinase 5 and receptor tyrosine kinase like orphan receptor 1, were identified through PPI network analysis. The results of the present study have provided novel ideas for predicting the prognosis of patients with PCa following RP.

Breakthroughs in modern cancer therapy and elusive cardiotoxicity: Critical research-practice gaps, challenges, and insights

To date, five cancer treatment modalities have been defined. The three traditional modalities of cancer treatment are surgery, radiotherapy, and conventional chemotherapy, and the two modern modalities include molecularly targeted therapy (the fourth modality) and immunotherapy (the fifth modality). The cardiotoxicity associated with conventional chemotherapy and radiotherapy is well known. Similar adverse cardiac events are resurging with the fourth modality. Aside from the conventional and newer targeted agents, even the most newly developed, immune-based therapeutic modalities of anticancer treatment (the fifth modality), e.g., immune checkpoint inhibitors and chimeric antigen receptor (CAR) T-cell therapy, have unfortunately led to potentially lethal cardiotoxicity in patients. Cardiac complications represent unresolved and potentially life-threatening conditions in cancer survivors, while effective clinical management remains quite challenging. As a consequence, morbidity and mortality related to cardiac complications now threaten to offset some favorable benefits of modern cancer treatments in cancer-related survival, regardless of the oncologic prognosis. This review focuses on identifying critical research-practice gaps, addressing real-world challenges and pinpointing real-time insights in general terms under the context of clinical cardiotoxicity induced by the fourth and fifth modalities of cancer treatment. The information ranges from basic science to clinical management in the field of cardio-oncology and crosses the interface between oncology and onco-pharmacology. The complexity of the ongoing clinical problem is addressed at different levels. A better understanding of these research-practice gaps may advance research initiatives on the development of mechanism-based diagnoses and treatments for the effective clinical management of cardiotoxicity.

ASK family and cancer

Cancer is a major problem in public health and is one of the leading causes of mortality worldwide. Many types of cancer cells exhibit aberrant cellular signal transduction in response to stress, which often leads to oncogenesis. Mitogen-activated protein kinase (MAPK) signal cascades are one of the important intracellular stress signaling pathways closely related to cancer. The key molecules in MAPK signal cascades that respond to various types of stressors are apoptosis signal-regulating kinase (ASK) family members; ASK1, ASK2 and ASK3. ASK family members are activated by a wide variety of stressors, and they regulate various cellular responses, such as cell proliferation, inflammation and apoptosis. In this review, we will discuss both the oncogenic and anti-oncogenic roles of the ASK family members in various contexts of cancer development with deeper insights into the involvement of ASK family members in cancer pathology.

Bivalent Epigenetic Control of Oncofetal Gene Expression in Cancer

Multiple mechanisms of epigenetic control that include DNA methylation, histone modification, noncoding RNAs, and mitotic gene bookmarking play pivotal roles in stringent gene regulation during lineage commitment and maintenance. Experimental evidence indicates that bivalent chromatin domains, i.e., genome regions that are marked by both H3K4me3 (activating) and H3K27me3 (repressive) histone modifications, are a key property of pluripotent stem cells. Bivalency of developmental genes during the G₁ phase of the pluripotent stem cell cycle contributes to cell fate decisions. Recently, some cancer types have been shown to exhibit partial recapitulation of bivalent chromatin modifications that are lost along with pluripotency, suggesting a mechanism by which cancer cells reacquire properties that are characteristic of undifferentiated, multipotent cells. This bivalent epigenetic control of oncofetal gene expression in cancer cells may offer novel insights into the onset and progression of cancer and may provide specific and selective options for diagnosis as well as for therapeutic intervention.

Antitumor activity of a newly developed monoclonal antibody against ROR1 in ovarian cancer cells

Receptor-tyrosine-kinase-like Orphan Receptor 1 (ROR1) is a tyrosine-protein kinase transmembrane receptor and ROR1 overexpression is associated with a poor prognosis in various cancers, including ovarian cancer. Targeting of ROR1 has been evaluated as a novel cancer therapy strategy. This study developed a novel chimeric anti-ROR1 Fab antibody (named ROR1-cFab) and then assessed the antitumor activity of this antibody in ovarian cancer cells, an in vitro model of preclinical cancer therapy. A ROR1-cFab prokaryotic expression vector was constructed from positive fusion cells (splenocytes from mice with high ROR1 immune titers were fused with myeloma cells) after three rounds of sub-clone affinity screening. Then, a variety of assays were employed to assess the binding selectivity and specificity of ROR1-cFab to ROR1 protein. Furthermore, CCK8, flow cytometric apoptosis, wound healing, and Transwell migration assays were used to assess antitumor activity of this newly developed anti-ROR1 antibody in ovarian cancer cells. We demonstrated that ROR1-cFab could specifically bind to ROR1 protein and ROR1-positive ovarian cancer A2780 cells. Functional assays revealed that ROR1-cFab inhibited tumor cell proliferation and migration, as well as inducing apoptosis of ROR1-positive A2780 cells in a dose dependent manner. These effects were not observed in ROR1-negative lose386 cells. In conclusion, ROR1-cFab is a novel anti-ROR1 antibody with a high affinity to ROR1 protein and inhibitory effects on ROR1-positive cells. Future studies will determine whether the ROR1-cFab might be a promising candidate for treatment of ROR1-positive ovarian 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.