ROR1-STAT3 signaling contributes to ovarian cancer intra-tumor heterogeneity.

Wnt pathway dysregulation through genetic and non-genetic alterations occurs in multiple cancers, including ovarian cancer (OC). The aberrant expression of the non-canonical Wnt signaling receptor ROR1 is thought to contribute to OC progression and drug resistance. However, the key molecular events mediated by ROR1 that are involved in OC tumorigenesis are not fully understood. Here, we show that ROR1 expression is enhanced by neoadjuvant chemotherapy, and Wnt5a binding to ROR1 can induce oncogenic signaling via AKT/ERK/STAT3 activation in OC cells. Proteomics analysis of isogenic ROR1-knockdown OC cells identified STAT3 as a downstream effector of ROR1 signaling. Transcriptomics analysis of clinical samples (n = 125) revealed that ROR1 and STAT3 are expressed at higher levels in stromal cells than in epithelial cancer cells of OC tumors, and these findings were corroborated by multiplex immunohistochemistry (mIHC) analysis of an independent OC cohort (n = 11). Our results show that ROR1 and its downstream STAT3 are co-expressed in epithelial as well as stromal cells of OC tumors, including cancer-associated fibroblasts or CAFs. Our data provides the framework to expand the clinical utility of ROR1 as a therapeutic target to overcome OC progression.

Drug response profiles in patient-derived cancer cells across histological subtypes of ovarian cancer: real-time therapy tailoring for a patient with low-grade serous carcinoma.

Many efforts are underway to develop novel therapies against the aggressive high-grade serous ovarian cancers (HGSOCs), while our understanding of treatment options for low-grade (LGSOC) or mucinous (MUCOC) of ovarian malignancies is not developing as well. We describe here a functional precision oncology (fPO) strategy in epithelial ovarian cancers (EOC), which involves high-throughput drug testing of patient-derived ovarian cancer cells (PDCs) with a library of 526 oncology drugs, combined with genomic and transcriptomic profiling. HGSOC, LGSOC and MUCOC PDCs had statistically different overall drug response profiles, with LGSOCs responding better to targeted inhibitors than HGSOCs. We identified several subtype-specific drug responses, such as LGSOC PDCs showing high sensitivity to MDM2, ERBB2/EGFR inhibitors, MUCOC PDCs to MEK inhibitors, whereas HGSOCs showed strongest effects with CHK1 inhibitors and SMAC mimetics. We also explored several drug combinations and found that the dual inhibition of MEK and SHP2 was synergistic in MAPK-driven EOCs. We describe a clinical case study, where real-time fPO analysis of samples from a patient with metastatic, chemorefractory LGSOC with a CLU-NRG1 fusion guided clinical therapy selection. fPO-tailored therapy with afatinib, followed by trastuzumab and pertuzumab, successfully reduced tumour burden and blocked disease progression over a five-year period. In summary, fPO is a powerful approach for the identification of systematic drug response differences across EOC subtypes, as well as to highlight patient-specific drug regimens that could help to optimise therapies to individual patients in the future.

Multiomics characterization implicates PTK7 in ovarian cancer EMT and cell plasticity and offers strategies for therapeutic intervention.

Most patients with ovarian cancer (OC) are diagnosed at a late stage when there are very few therapeutic options and a poor prognosis. This is due to the lack of clearly defined underlying mechanisms or an oncogenic addiction that can be targeted pharmacologically, unlike other types of cancer. Here, we identified protein tyrosine kinase 7 (PTK7) as a potential new therapeutic target in OC following a multiomics approach using genetic and pharmacological interventions. We performed proteomics analyses upon PTK7 knockdown in OC cells and identified novel downstream effectors such as synuclein-γ (SNCG), SALL2, and PP1γ, and these findings were corroborated in ex vivo primary samples using PTK7 monoclonal antibody cofetuzumab. Our phosphoproteomics analyses demonstrated that PTK7 modulates cell adhesion and Rho-GTPase signaling to sustain epithelial-mesenchymal transition (EMT) and cell plasticity, which was confirmed by high-content image analysis of 3D models. Furthermore, using high-throughput drug sensitivity testing (525 drugs) we show that targeting PTK7 exhibited synergistic activity with chemotherapeutic agent paclitaxel, CHK1/2 inhibitor prexasertib, and PLK1 inhibitor GSK461364, among others, in OC cells and ex vivo primary samples. Taken together, our study provides unique insight into the function of PTK7, which helps to define its role in mediating aberrant Wnt signaling in ovarian cancer.

Cellular thermal shift assay (CETSA) for determining the drug binding affinity using Ba/F3 clones stably expressing receptor pseudokinases.

The majority of drug screening approaches are performed using recombinant proteins, however, drug binding to its target(s) in cells should be also assessed, especially for drugs aimed at modulating intracellular signaling pathways. As a result, the development of a cellular thermal shift assay (CETSA) has become an important tool for determining the binding affinity of drugs to their intracellular targets. Cell lines, such as Ba/F3, are an excellent model system to stably express and study a target protein when this protein is not endogenously expressed or only present at low levels. Together with CETSA, Ba/F3 clones allow study of the transforming properties of the protein in question, its downstream intracellular signaling activation pathways, as well as its drug binding kinetics. This chapter describes in detail the establishment of Ba/F3 clones stably expressing receptor pseudokinases, such as receptor tyrosine kinase-like orphan receptors (ROR1, ROR2) and protein tyrosine kinase 7 (PTK7), and the use thereof to evaluate binding of small molecule inhibitors to their intracellular (pseudo)kinase domain by CETSA.

New insights into the molecular mechanisms of ROR1, ROR2, and PTK7 signaling from the proteomics and pharmacological modulation of ROR1 interactome.

ROR1, ROR2, and PTK7 are Wnt ligand-binding members of the receptor tyrosine kinase family. Despite their lack of catalytic activity, these receptors regulate skeletal, cardiorespiratory, and neurological development during embryonic and fetal stages. However, their overexpression in adult tissue is strongly connected to tumor development and metastasis, suggesting a strong pharmacological potential for these molecules. Wnt5a ligand can activate these receptors, but lead to divergent signaling and functional outcomes through mechanisms that remain largely unknown. Here, we developed a cellular model by stably expressing ROR1, ROR2, and PTK7 in BaF3 cells that allowed us to readily investigate side-by-side their signaling capability and functional outcome. We applied proteomic profiling to BaF3 clones and identified distinctive roles for ROR1, ROR2, and PTK7 pseudokinases in modulating the expression of proteins involved in cytoskeleton dynamics, apoptotic, and metabolic signaling. Functionally, we show that ROR1 expression enhances cell survival and Wnt-mediated cell proliferation, while ROR2 and PTK7 expression is linked to cell migration. We also demonstrate that the distal C-terminal regions of ROR1 and ROR2 are required for receptors stability and downstream signaling. To probe the pharmacological modulation of ROR1 oncogenic signaling, we used affinity purification coupled to mass spectrometry (AP-MS) and proximity-dependent biotin identification (BioID) to map its interactome before and after binding of GZD824, a small molecule inhibitor previously shown to bind to the ROR1 pseudokinase domain. Our findings bring new insight into the molecular mechanisms of ROR1, ROR2, and PTK7, and highlight the therapeutic potential of targeting ROR1 with small molecule inhibitors binding to its vestigial ATP-binding site.

High-throughput ex vivo drug testing identifies potential drugs and drug combinations for NRAS-positive malignant melanoma.

Therapy options for patients with metastatic melanoma (MM) have considerably improved over the past decade. However, many patients still need effective therapy after unsuccessful immunotherapy, especially patients with BRAF-negative tumors who lack the option of targeted treatment second line. Therefore, the elucidation of efficient and personalized therapy options for these patients is required. In this study, three patient-derived cancer cells (PDCs) were established from NRAS Q61-positive MM patients. The response of PDCs and five established melanoma cell lines (two NRAS-positive, one wild type, and two BRAF V600-positive) was evaluated toward a panel of 527 oncology drugs using high-throughput drug sensitivity and resistance testing. The PDCs and cell lines displayed strong responses to MAPK inhibitors, as expected. Additionally, the PDCs and cell lines were responsive to PI3K/mTOR, mTOR, and PLK1 inhibitors among other effective drugs currently undergoing clinical trials. Combinations with a MEK inhibitor were tested with other targeted agents to identify effective synergies. MEK inhibitor showed synergy with multikinase inhibitor ponatinib, ABL inhibitor nilotinib, PI3K/mTOR inhibitor pictilisib, and pan-RAF inhibitor LY3009120. The application of the patients' cancer cells for functional drug testing ex vivo is one step further in the process of identifying potential agents and agent combinations to personalize treatment for patients with MM. Our preliminary study results suggest that this approach has the potential for larger-scale drug testing and personalized treatment applications in our expansion trial. Our results show that drug sensitivity and resistance testing may be implementable in the treatment planning of patients with MM.

Evaluating Targeted Therapies in Ovarian Cancer Metabolism: Novel Role for PCSK9 and Second Generation mTOR Inhibitors.

BACKGROUND: Dysregulated lipid metabolism is emerging as a hallmark in several malignancies, including ovarian cancer (OC). Specifically, metastatic OC is highly dependent on lipid-rich omentum. We aimed to investigate the therapeutic value of targeting lipid metabolism in OC. For this purpose, we studied the role of PCSK9, a cholesterol-regulating enzyme, in OC cell survival and its downstream signaling. We also investigated the cytotoxic efficacy of a small library of metabolic (n = 11) and mTOR (n = 10) inhibitors using OC cell lines (n = 8) and ex vivo patient-derived cell cultures (PDCs, n = 5) to identify clinically suitable drug vulnerabilities. Targeting PCSK9 expression with siRNA or PCSK9 specific inhibitor (PF-06446846) impaired OC cell survival. In addition, overexpression of PCSK9 induced robust AKT phosphorylation along with increased expression of ERK1/2 and MEK1/2, suggesting a pro-survival role of PCSK9 in OC cells. Moreover, our drug testing revealed marked differences in cytotoxic responses to drugs targeting metabolic pathways of high-grade serous ovarian cancer (HGSOC) and low-grade serous ovarian cancer (LGSOC) PDCs. Our results show that targeting PCSK9 expression could impair OC cell survival, which warrants further investigation to address the dependency of this cancer on lipogenesis and omental metastasis. Moreover, the differences in metabolic gene expression and drug responses of OC PDCs indicate the existence of a metabolic heterogeneity within OC subtypes, which should be further explored for therapeutic improvements.

STRN-ALK rearranged pediatric malignant peritoneal mesothelioma - Functional testing of 527 cancer drugs in patient-derived cancer cells.

Genetic rearrangements involving the anaplastic lymphoma kinase (ALK) gene create oncogenic drivers for several cancers, including malignant peritoneal mesothelioma (MPeM). Here, we report genomic and functional precision oncology profiling on a rare case of a 5-year old patient diagnosed with wide-spread and aggressive MPeM, driven by STRN-ALK rearrangement. We established genomically representative patient-derived cancer cells (PDCs) from the tumor sample and performed high-throughput drug sensitivity testing with 527 oncology compounds to identify potent inhibitors. As expected, the PDCs were overall sensitive to the ALK inhibitors, although the eight different inhibitors tested had variable efficacy. We also discovered other effective inhibitors, such as MEK/ERK inhibitors and those targeting pathways downstream of ALK as well as Bcl-xl inhibitors. In contrast, most cytotoxic drugs were not very effective. ALK inhibitors synergized with MEK and PI3K/mTOR inhibitors, highlighting potential combinatorial strategies to enhance drug efficacy and tackle drug resistance. Based on genomic data and associated functional validation, the patient was treated with the ALK inhibitor crizotinib in combination with conventional chemotherapy (cisplatin and gemcitabine). A complete disease remission was reached, lasting now for over 3 years. Our results illustrate a rare pediatric cancer case, and highlight the potential of functional precision oncology to discover pathogenetic drivers, validate dependency on driver signals, compare different inhibitors against each other and potentially enhance targeted treatments by drug combinations. Such real-time implementation of functional precision oncology could pave the way towards safer and more effective personalized cancer therapies for individual pediatric cancer patients with rare tumors.

Glucocorticoids induce differentiation and chemoresistance in ovarian cancer by promoting ROR1-mediated stemness.

Glucocorticoids are routinely used in the clinic as anti-inflammatory and immunosuppressive agents as well as adjuvants during cancer treatment to mitigate the undesirable side effects of chemotherapy. However, recent studies have indicated that glucocorticoids may negatively impact the efficacy of chemotherapy by promoting tumor cell survival, heterogeneity, and metastasis. Here, we show that dexamethasone induces upregulation of ROR1 expression in ovarian cancer (OC), including platinum-resistant OC. Increased ROR1 expression resulted in elevated RhoA, YAP/TAZ, and BMI-1 levels in a panel of OC cell lines as well as primary ovarian cancer patient-derived cells, underlining the translational relevance of our studies. Importantly, dexamethasone induced differentiation of OC patient-derived cells ex vivo according to their molecular subtype and the phenotypic expression of cell differentiation markers. High-throughput drug testing with 528 emerging and clinical oncology compounds of OC cell lines and patient-derived cells revealed that dexamethasone treatment increased the sensitivity to several AKT/PI3K targeted kinase inhibitors, while significantly decreasing the efficacy of chemotherapeutics such as taxanes, as well as anti-apoptotic compounds such as SMAC mimetics. On the other hand, targeting ROR1 expression increased the efficacy of taxane drugs and SMAC mimetics, suggesting new combinatorial targeted treatments for patients with OC.

Structural Insights into Pseudokinase Domains of Receptor Tyrosine Kinases.

Despite their apparent lack of catalytic activity, pseudokinases are essential signaling molecules. Here, we describe the structural and dynamic properties of pseudokinase domains from the Wnt-binding receptor tyrosine kinases (PTK7, ROR1, ROR2, and RYK), which play important roles in development. We determined structures of all pseudokinase domains in this family and found that they share a conserved inactive conformation in their activation loop that resembles the autoinhibited insulin receptor kinase (IRK). They also have inaccessible ATP-binding pockets, occluded by aromatic residues that mimic a cofactor-bound state. Structural comparisons revealed significant domain plasticity and alternative interactions that substitute for absent conserved motifs. The pseudokinases also showed dynamic properties that were strikingly similar to those of IRK. Despite the inaccessible ATP site, screening identified ATP-competitive type-II inhibitors for ROR1. Our results set the stage for an emerging therapeutic modality of "conformational disruptors" to inhibit or modulate non-catalytic functions of pseudokinases deregulated in disease.

Molecular Mechanisms Associated with ROR1-Mediated Drug Resistance: Crosstalk with Hippo-YAP/TAZ and BMI-1 Pathways.

Signaling via the Wnt-related receptor tyrosine kinase-like orphan receptor 1 (ROR1) triggers tumorigenic features associated with cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT), while aberrant expression of ROR1 is strongly linked to advanced disease progression and chemoresistance. Several recent studies have shown that Wnt5a binding to ROR1 promotes oncogenic signaling by activating multiple pathways such as RhoA/Rac1 GTPases and PI3K/AKT, which in turn could induce transcriptional coactivator YAP/TAZ or polycomb complex protein BMI-1 signaling, respectively, to sustain stemness, metastasis and ultimately drug-resistance. These data point towards a new feedback loop during cancer development, linking Wnt5a-ROR1 signaling activation to YAP/TAZ or BMI-1 upregulation that could play an important role in disease progression and treatment resistance. This review focuses on the crosstalk between Wnt5a-ROR1 and YAP/TAZ or the BMI-1 signaling network, together with the current advancements in targeted strategies for ROR1-positive cancers.

Transanal Total Mesorectal Excision - A Case Report.

Transanal total mesorectal excision (TaTME), first introduced in 2010, represents a relatively new approach in the surgical treatment of rectal cancer. A case of a 65-years-old patient diagnosed with moderately differentiated adenocarcinoma of the middle rectum (cT2N0M0) is presented. Taking into consideration patient's characteristics and tumour features, the surgical team decided to use transanal total mesorectal excision technique. The surgical technique, as well as potential postoperative complications and oncological issues are discussed in the article. Patient selection and extensive experience in minimally invasive colorectal surgery are the bases for an optimal technique implementation. Although further studies are required in order to confirm its superiority over the laparoscopic total mesorectal excision, TaTME seems to be a safe and feasible option in the surgical approach of rectal cancer.

Wnt5a and ROR1 activate non-canonical Wnt signaling via RhoA in TCF3-PBX1 acute lymphoblastic leukemia and highlight new treatment strategies via Bcl-2 co-targeting.

B-cell precursor acute lymphoblastic leukemia (BCP-ALL) with TCF3-PBX1 fusion gene expression has constitutively elevated levels of Wnt16b and ROR1 (receptor tyrosine kinase-like orphan receptor), a ligand and a receptor from the Wnt signaling pathway, respectively. Although survival rate is usually high after the initial chemotherapy, many TCF3-PBX1 BCP-ALL patients relapse and subsequently develop treatment resistance, resulting in poor prognosis. Here, we aimed to investigate the molecular signaling associated with Wnt16b and ROR1 overexpression in TCF3-PBX1 cell lines and primary samples, and to identify effective treatment options via ROR1 targeting. We detected higher ROR1 expression on TCF3-PBX1 leukemic cells even at a later stage of patient relapse, providing a strong rationale for the use of ROR1-targeted therapy. We found that Wnt5a-ROR1 signaling enhances proliferation of TCF3-PBX1 cells via RhoA/Rac1 GTPases activation and STAT3 upregulation. Wnt16b also activated the RhoA/Rac1 signaling cascade suggesting the activation of a non-canonical Wnt pathway in TCF3-PBX1 cells. Wnt16 could interact with ROR1 but not in TCF3-PBX1 cells, suggesting that Wnt5a is the ligand signaling via ROR1 in TCF3-PBX1 cells. By high throughput drug-sensitivity testing of TCF3-PBX1 cells before and after ROR1 knockdown we found that targeting ROR1 significantly improves the therapeutic efficacy of Bcl-2 family inhibitors venetoclax and navitoclax, and this synergism was confirmed ex vivo using a drug-resistant primary sample from a relapsed TCF3-PBX1 patient. Our work underlines a new type of targeted combination therapy that could be clinically advantageous for patients with TCF3-PBX1 BCP-ALL.

Targeting Wnt signaling pseudokinases in hematological cancers.

Recent studies showed that several pseudokinases from the receptor tyrosine kinase family are important players in regulating cancer cell invasion, metastasis, and drug resistance, suggesting that targeting these proteins can play a therapeutic role in cancer treatment. Receptor Tyr kinase-like orphan receptors (RORs), protein Tyr kinase 7 (PTK7) (also called colon carcinoma kinase 4 (CCK4)), and receptor-like Tyr kinase (RYK) are Wnt ligand binding receptors within the non-canonical Wnt signaling, with important roles in development, tissue homeostasis, and organogenesis. At the cellular level, these receptors transduce signals important for cell survival, migration, polarization, and chemotaxis. Considerable progress has been made in the last decade in the field of pseudokinase signaling, improving our understanding of their structure-function mechanisms, and intracellular network of transduction components. Consequently, their role in various diseases, including cancer, is now scrutinized for therapeutic interventions to improve treatment outcome. In this article, we review findings regarding molecular mechanisms and targeted therapies for ROR1, PTK7, and RYK in hematological malignancies.

Interaction between ROR1 and MuSK activation complex in myogenic cells.

The ROR family of receptor tyrosine kinases, ROR1 and ROR2, is known to play an important role during skeletal muscle regeneration. ROR1 has a critical role in regulating satellite cell (SC) proliferation during muscle regeneration, and proinflammatory cytokines such as TNF-α and IL-1ß can induce expression of ROR1 in myogenic cells via NF-κB activation. While searching for ROR1-interacting proteins in myogenic cells, we identified MuSK as a ROR1-binding protein. MuSK interacts with and phosphorylates ROR1 at the cytoplasmic proline-rich domain. ROR1 also interacts with the MuSK activator Dok-7 independently of MuSK interaction. Collectively, our results identified ROR1 as a new interacting partner for MuSK and Dok-7, which may have an important role in myogenic cell signaling.

Perioperative Patient Blood Management Programme. Multidisciplinary recommendations from the Patient Blood Management Initiative Group.

Patients with untreated anaemia or iron deficiency who undergo surgical procedures have an increased risk for mortality and morbidity. Patient Blood Management programmes address this issue worldwide and try to improve patient outcomes through a complex set of measures targeting anaemia correction, minimisation of bleeding and improvement of anaemia tolerance, in all phases of perioperative care. The Patient Blood Management Initiative Group is a multidisciplinary team of physicians from specialties including anaesthesiology, nephrology, surgery, orthopaedics, haematology, gastroenterology and transfusion medicine. The team has elaborated ten recommendations, divided into five categories, in order to implement a Patient Blood Management programme in Romania, using the most recent and relevant evidence. The document was discussed during three meetings which took place during October 2016 and May 2017 and the result was modified and updated via e-mail.

The Romanian National Program for Liver Transplantation - 852 Procedures in 815 Patients over 17 Years (2000-2017): A Continuous Evolution to Success.

Background: Liver transplantation (LT) has become an established treatment for end-stage liver disease, with more than 20.000 procedures yearly worldwide. The aim of this study was to analyze the results of Romanian National Program of LT. Methods: Between April 2000 and April 2017, 817 pts received 852 LTs in Romania. Male/female ratio was 487/330, while adult/pediatric ratio was 753/64, with a mean age of 46 years (median 50 yrs; range 7 months - 68 yrs). Main LT indications were HBV cirrhosis (230 pts; 28.2%), HCC (173 pts; 21.2%), and HCV cirrhosis (137 pts; 16.8%). Waiting time and indications for LT, patient and donor demographics, graft features, surgical procedures, and short and long-term outcomes were analyzed. Results: DDLT was performed in 682 pts (83.9%): whole LT in 662 pts (81%), split LT in 16 pts (2.3%), reduced LT in 2 pts (0.2%), and domino LT in 1 pts (0.1%). LDLT was performed in 135 pts (16.5%): right hemiliver in 93 pts (11.4%), left lateral section in 28 pts (3.4%), left hemiliver in 8 pts (1%), left hemiliver with segment 1 in 4 pts (0.5%), and dual graft LDLT in 2 pts (0.2%). Overall major morbidity rate was 31.4% (268 pts), while perioperative mortality was 7.9% (65 pts). Retransplantation rate was 4.3% (35 pts): 27 whole LTs, 3 reduced LTs, 3 split LTs, and 2 LDLT. Long-term overall 1-, 3-, and 5-year estimated survival rates for patients were 87.9%, 81.5%, and 79.1%, respectively. One-, 3-, and 5-year overall mortality on waiting list also decreased significantly over time from 31.4%, 54.1% and 63.5%, to 4.4%, 13.9% and 23.6%, respectively. Conclusions: The Romanian National program for liver transplantation addresses all causes of acute and chronic liver failure or liver tumors in adults and children, using all surgical techniques, with good long-term outcome. The program constantly evolved over time, leading to decreased mortality rate on the waiting list.

Liver Resections in a High-Volume Center: Form Standard Procedures to Extreme Surgery and Ultrasound-guided Resections.

Background: Liver resection (LR) is the treatment of choice for most benign and malignant focal liver lesions, as well as in selected patients with liver trauma. Few other therapies can compete with LR in selected cases, such as liver transplantation in hepatocellular carcinoma (HCC) and ablative therapies in small HCCs or liver metastases. The present paper analyses a single center experience in LR, reviewing the indications of LR, the operative techniques and their short-term results. MATERIAL AND METHOD: Between January 2000 and December 2016, in "œDan Setlacec" Center of General Surgery and Liver Transplantation were performed 3165 LRs in 3016 patients, for pathologic conditions of the liver. In the present series, liver resections for living-donor liver transplantation were excluded. The median age of the patients was 56 years (mean 58 years; range 1-88), with male/female ratio 1524/1492 and adult/pediatric patient ratio 2973/43. Results: Malignant lesions were the main indication for LR (2372 LRs; 74.9%). Among these, colorectal liver metastases were the most frequent indication (952 LRs; 30.1%), followed by hepatocellular carcinoma (575 patients, 18.2%). The highest number of resected tumors per patient was 21, and the median diameter of the largest tumor was 40 mm (mean 51 mm; range 3-250). Major resections rate was 18.6% (588 LRs) and anatomical LRs were performed in 789 patients (24.9%). The median operative time was 180 minutes (mean 204 minutes; range 45-920). The median blood loss was 500 ml (mean 850 ml; range 500-9500), with a transfusion rate of 41.6% (1316 LRs). The morbidity rate was 40.1% (1270 LRs) and the rate of major complications (Dindo-Clavien IIIa or more) was 13.2% (418 LRs). Mortality rate was 4.2% (127 pts). CONCLUSION: LRs should be performed in specialized high-volume centers to achieve the best results (low morbidity and mortality rates).

Identification and Characterization of JAK2 Pseudokinase Domain Small Molecule Binders.

Janus kinases (JAKs) regulate hematopoiesis via the cytokine-mediated JAK-STAT signaling pathway. JAKs contain tandem C-terminal pseudokinase (JH2) and tyrosine kinase (JH1) domains. The JAK2 pseudokinase domain adopts a protein kinase fold and, despite its pseudokinase designation, binds ATP with micromolar affinity. Recent evidence shows that displacing ATP from the JAK2 JH2 domain alters the hyperactivation state of the oncogenic JAK2 V617F protein while sparing the wild type JAK2 protein. In this study, small molecule binders of JAK2 JH2 were identified via an in vitro screen. Top hits were characterized using biophysical and structural approaches. Development of pseudokinase-selective compounds may offer novel pharmacological opportunities for treating cancers driven by JAK2 V617F and other oncogenic JAK mutants.

Targeting ROR1 identifies new treatment strategies in hematological cancers.

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is a member of the ROR receptor family consisting of two closely related type I transmembrane proteins ROR1 and ROR2. Owing to mutations in their canonical motifs required for proper kinase activity, RORs are classified as pseudokinases lacking detectable catalytic activity. ROR1 stands out for its selective and high expression in numerous blood and solid malignancies compared with a minimal expression in healthy adult tissues, suggesting high potential for this molecule as a drug target for cancer therapy. Current understanding attributes a survival role for ROR1 in cancer cells; however, its oncogenic function is cancer-type-specific and involves various signaling pathways. High interest in ROR1-targeted therapies resulted in the development of ROR1 monoclonal antibodies such as cirmtuzumab, currently in a phase I clinical trial for chronic lymphocytic leukemia. Despite these advances in translational studies, the molecular mechanism employed by ROR1 in different cancers is not yet fully understood; therefore, more insights into the oncogenic role of ROR1 signaling are crucial in order to optimize the use of targeted drugs. Recent studies provided evidence that targeting ROR1 simultaneously with inhibition of B-cell receptor (BCR) signaling is more effective in killing ROR1-positive leukemia cells, suggesting a synergistic correlation between co-targeting ROR1 and BCR pathways. Although this synergy has been previously reported for B-cell acute lymphoblastic leukemia, the molecular mechanism appears rather different. These results provide more insights into ROR1-BCR combinatorial treatment strategies in hematological malignancies, which could benefit in tailoring more effective targeted therapies in other ROR1-positive cancers.