Spatial regulation of receptor tyrosine kinases in development and cancer

Therapeutic advances of targeting receptor tyrosine kinases in cancer

Receptor tyrosine kinases (RTKs), a category of transmembrane receptors, have gained significant clinical attention in oncology due to their central role in cancer pathogenesis. Genetic alterations, including mutations, amplifications, and overexpression of certain RTKs, are critical in creating environments conducive to tumor development. Following their discovery, extensive research has revealed how RTK dysregulation contributes to oncogenesis, with many cancer subtypes showing dependency on aberrant RTK signaling for their proliferation, survival and progression. These findings paved the way for targeted therapies that aim to inhibit crucial biological pathways in cancer. As a result, RTKs have emerged as primary targets in anticancer therapeutic development. Over the past two decades, this has led to the synthesis and clinical validation of numerous small molecule tyrosine kinase inhibitors (TKIs), now effectively utilized in treating various cancer types. In this manuscript we aim to provide a comprehensive understanding of the RTKs in the context of cancer. We explored the various alterations and overexpression of specific receptors across different malignancies, with special attention dedicated to the examination of current RTK inhibitors, highlighting their role as potential targeted therapies. By integrating the latest research findings and clinical evidence, we seek to elucidate the pivotal role of RTKs in cancer biology and the therapeutic efficacy of RTK inhibition with promising treatment outcomes.

Discovery of Novel Receptor Tyrosine Kinase-like Orphan Receptor 1 (ROR1) Inhibitors for Cancer Treatment

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncogenic membrane protein in several malignancies and has been considered an attractive target for the treatment of human cancers. In this study, structure-based virtual screening and structure optimization were conducted to identify novel ROR1 inhibitors. Based on hit compound 2, 45 novel ROR1 inhibitors were designed and synthesized, and the detailed structure-activity relationship was investigated. Representative compound 19h potently binds ROR1 with a KD value of 0.10 μM, exhibiting antitumor activity in lung cancer and breast cancer cell lines (IC50: 0.36-1.37 μM). Additionally, a mechanism investigation demonstrated that compound 19h induces the apoptosis of tumor cells. Importantly, compound 19h significantly suppressed tumor growth in a mouse model without obvious toxicity. Overall, this work identified compound 19h as a new ROR1 inhibitor, providing a novel lead compound for the treatment of lung cancer and breast cancer.

Fine tuning of CpG spatial distribution with DNA origami for improved cancer vaccination

Multivalent presentation of ligands often enhances receptor activation and downstream signalling. DNA origami offers a precise nanoscale spacing of ligands, a potentially useful feature for therapeutic nanoparticles. Here we use a square-block DNA origami platform to explore the importance of the spacing of CpG oligonucleotides. CpG engages Toll-like receptors and therefore acts to activate dendritic cells. Through in vitro cell culture studies and in vivo tumour treatment models, we demonstrate that square blocks induce Th1 immune polarization when CpG is spaced at 3.5 nm. We observe that this DNA origami vaccine enhances DC activation, antigen cross-presentation, CD8 T-cell activation, Th1-polarized CD4 activation and natural-killer-cell activation. The vaccine also effectively synergizes with anti-PD-L1 for improved cancer immunotherapy in melanoma and lymphoma models and induces long-term T-cell memory. Our results suggest that DNA origami may serve as a platform for controlling adjuvant spacing and co-delivering antigens in vaccines.

Endoplasmic reticulum-plasma membrane contact gradients direct cell migration

Directed cell migration is driven by the front-back polarization of intracellular signalling1-3. Receptor tyrosine kinases and other inputs activate local signals that trigger membrane protrusions at the front2,4-6. Equally important is a long-range inhibitory mechanism that suppresses signalling at the back to prevent the formation of multiple fronts7-9. However, the identity of this mechanism is unknown. Here we report that endoplasmic reticulum-plasma membrane (ER-PM) contact sites are polarized in single and collectively migrating cells. The increased density of these ER-PM contacts at the back provides the ER-resident PTP1B phosphatase more access to PM substrates, which confines receptor signalling to the front and directs cell migration. Polarization of the ER-PM contacts is due to microtubule-regulated polarization of the ER, with more RTN4-rich curved ER at the front and more CLIMP63-rich flattened ER at the back. The resulting ER curvature gradient leads to small and unstable ER-PM contacts only at the front. These contacts flow backwards and grow to large and stable contacts at the back to form the front-back ER-PM contact gradient. Together, our study suggests that the structural polarity mediated by ER-PM contact gradients polarizes cell signalling, directs cell migration and prolongs cell migration.

Receptor tyrosine kinase-like orphan receptor 1: A novel antitumor target in gastrointestinal cancers

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is a member of the type I receptor tyrosine kinase family. ROR1 is pivotal in embryonic development and cancer, and serves as a biomarker and therapeutic target. It has soluble and membrane-bound subtypes, with the latter highly expressed in tumors. ROR1 is conserved throughout evolution and may play a role in the development of gastrointestinal cancer through multiple signaling pathways and molecular mechanisms. Studies suggest that overexpression of ROR1 may increase tumor invasiveness and metastasis. Additionally, ROR1 may regulate the cell cycle, stem cell characteristics, and interact with other signaling pathways to affect cancer progression. This review explores the structure, expression and role of ROR1 in the development of gastrointestinal cancers. It discusses current antitumor strategies, outlining challenges and prospects for treatment.

Heterogeneous Profile of ROR1 Protein Expression across Tumor Types

The Wnt receptor ROR1 has generated increased interest as a cancer therapeutic target. Research on several therapeutic approaches involving this receptor is ongoing; however, ROR1 tissue expression remains understudied. We performed an immunohistochemistry analysis of ROR1 protein expression in a large cohort of multiple tumor and histologic types. We analyzed 12 anonymized multi-tumor tissue microarrays (TMAs), including mesothelioma, esophageal and upper gastrointestinal carcinomas, and uterine endometrioid carcinoma, among other tumor types. Additionally, we studied 5 different sarcoma types of TMAs and 6 patient-derived xenografts (PDX) TMAs developed from 19 different anatomic sites and tumor histologic types. A total of 1142 patient cases from different histologic types and 140 PDXs placed in TMAs were evaluated. Pathologists assessed the percentage of tumor cells in each case that were positive for ROR1 and the intensity of staining. For determining the prevalence of staining for each tumor type, a case was considered positive if >1% of its tumor cells showed ROR1 staining. Our immunohistochemistry assays revealed a heterogeneous ROR1 expression profile. A high prevalence of ROR1 expression was found in mesothelioma (84.6%), liposarcoma (36.1%), gastrointestinal stromal tumors (33.3%), and uterine endometrioid carcinoma (28.9%). Other histologic types such as breast, lung, renal cell, hepatocellular, urothelial carcinoma, and colon carcinomas; glioblastoma; cholangiocarcinoma; and leiomyosarcoma showed less ROR1 overall expression, ranging between 0.9 and 13%. No ROR1 expression was seen in mesenchymal chondrosarcoma, rhabdomyosarcoma, or gastric adenocarcinoma cases. Overall, ROR1 expression was relatively infrequent and low in most tumor types investigated; however, ROR1 expression was infrequent but high in selected tumor types, such as gastroesophageal GIST, suggesting that ROR1 prescreening may be preferable for those indications. Further, mesothelioma exhibited frequent and high levels of ROR1 expression, which represents a previously unrecognized therapeutic opportunity. These findings can contribute to the development of ROR1-targeted therapies.

Adaptations of membrane trafficking in cancer and tumorigenesis

Membrane trafficking, a fundamental cellular process encompassing the transport of molecules to specific organelles, endocytosis at the plasma membrane and protein secretion, is crucial for cellular homeostasis and signalling. Cancer cells adapt membrane trafficking to enhance their survival and metabolism, and understanding these adaptations is vital for improving patient responses to therapy and identifying therapeutic targets. In this Review, we provide a concise overview of major membrane trafficking pathways and detail adaptations in these pathways, including COPII-dependent endoplasmic reticulum (ER)-to-Golgi vesicle trafficking, COPI-dependent retrograde Golgi-to-ER trafficking and endocytosis, that have been found in cancer. We explore how these adaptations confer growth advantages or resistance to cell death and conclude by discussing the potential for utilising this knowledge in developing new treatment strategies and overcoming drug resistance for cancer patients.

The emerging role of receptor tyrosine kinase phase separation in cancer

Receptor tyrosine kinase (RTK)-mediated signal transduction is fundamental to cell function and drives important cellular outcomes which, when dysregulated, can lead to malignant tumour growth and metastasis. The initiation of signals from plasma membrane-bound RTKs is subjected to multiple regulatory mechanisms that control downstream effector protein recruitment and function. The high propensity of RTKs to condense via liquid-liquid phase separation (LLPS) into membraneless organelles with downstream effector proteins provides a further fundamental mechanism for signal regulation. Herein we highlight how this phenomenon contributes to cancer signalling and consider the potential impact of LLPS on outcomes for cancer patients.

Elucidating the Role of Wildtype and Variant FGFR2 Structural Dynamics in (Dys)Function and Disorder

The fibroblast growth factor receptor 2 (FGFR2) gene is one of the most extensively studied genes with many known mutations implicated in several human disorders, including oncogenic ones. Most FGFR2 disease-associated gene mutations are missense mutations that result in constitutive activation of the FGFR2 protein and downstream molecular pathways. Many tertiary structures of the FGFR2 kinase domain are publicly available in the wildtype and mutated forms and in the inactive and activated state of the receptor. The current literature suggests a molecular brake inhibiting the ATP-binding A loop from adopting the activated state. Mutations relieve this brake, triggering allosteric changes between active and inactive states. However, the existing analysis relies on static structures and fails to account for the intrinsic structural dynamics. In this study, we utilize experimentally resolved structures of the FGFR2 tyrosine kinase domain and machine learning to capture the intrinsic structural dynamics, correlate it with functional regions and disease types, and enrich it with predicted structures of variants with currently no experimentally resolved structures. Our findings demonstrate the value of machine learning-enabled characterizations of structure dynamics in revealing the impact of mutations on (dys)function and disorder in FGFR2.

A dual-functional microfluidic chip for guiding personalized lung cancer medicine: combining EGFR mutation detection and organoid-based drug response test

Many efforts have been paid to advance the effectiveness of personalized medicine for lung cancer patients. Sequencing-based molecular diagnosis of EGFR mutations has been widely used to guide the selection of anti-lung-cancer drugs. Organoid-based assays have also been developed to ex vivo test individual responses to anti-lung-cancer drugs. After addressing several technical difficulties, a new combined strategy, in which anti-cancer medicines are first selected based on molecular diagnosis and then ex vivo tested on organoids, has been realized in a single dual-functional microfluidic chip. A DNA-based nanoruler has been developed to detect the existence of EGFR mutations and shrink the detection period from weeks to hours, compared with sequencing. The employment of the DNA-based nanoruler creates a possibility to purposively test anti-cancer drugs, either EGFR-TKIs or chemotherapy drugs, not both, on limited amounts of organoids. Moreover, a DNA-based nanosensor has been developed to recognize intracellular ATP variation without harming cell viability, realizing in situ monitoring of the whole course growth status of organoids for on-chip drug response test. The dual-functional microfluidic chip was validated by both cell lines and clinical samples from lung cancer patients. Furthermore, based on the dual-functional microfluidic chip, a fully automated system has been developed to span the divide between experimental procedures and therapeutic approaches. This study constitutes a novel way of combining EGFR mutation detection and organoid-based drug response test on an individual patient for guiding personalized lung cancer medicine.

The occurrence and development mechanisms of esophageal stricture: state of the art review

BACKGROUND

Esophageal strictures significantly impair patient quality of life and present a therapeutic challenge, particularly due to the high recurrence post-ESD/EMR. Current treatments manage symptoms rather than addressing the disease's etiology. This review concentrates on the mechanisms of esophageal stricture formation and recurrence, seeking to highlight areas for potential therapeutic intervention.

METHODS

A literature search was conducted through PUBMED using search terms: esophageal stricture, mucosal resection, submucosal dissection. Relevant articles were identified through manual review with reference lists reviewed for additional articles.

RESULTS

Preclinical studies and data from animal studies suggest that the mechanisms that may lead to esophageal stricture include overdifferentiation of fibroblasts, inflammatory response that is not healed in time, impaired epithelial barrier function, and multimethod factors leading to it. Dysfunction of the epithelial barrier may be the initiating mechanism for esophageal stricture. Achieving perfect in-epithelialization by tissue-engineered fabrication of cell patches has been shown to be effective in the treatment and prevention of esophageal strictures.

CONCLUSION

The development of esophageal stricture involves three stages: structural damage to the esophageal epithelial barrier (EEB), chronic inflammation, and severe fibrosis, in which dysfunction or damage to the EEB is the initiating mechanism leading to esophageal stricture. Re-epithelialization is essential for the treatment and prevention of esophageal stricture. This information will help clinicians or scientists to develop effective techniques to treat esophageal stricture in the future.

Detecting Disruption of HER2 Membrane Protein Organization in Cell Membranes with Nanoscale Precision

The spatiotemporal organization of proteins within the cell membrane can affect numerous biological functions, including cell signaling, communication, and transportation. Deviations from normal spatial arrangements have been observed in various diseases, and a better understanding of this process is a key stepping stone to advancing development of clinical interventions. However, given the nanometer length scales involved, detecting these subtle changes has primarily relied on complex super-resolution and single-molecule imaging methods. In this work, we demonstrate an alternative fluorescent imaging strategy for detecting protein organization based on a material that exhibits a unique photophysical behavior known as aggregation-induced emission (AIE). Organic AIE molecules have an increase in emission signal when they are in close proximity, and the molecular motion is restricted. This property simultaneously addresses the high background noise and low detection signal that limit conventional widefield fluorescent imaging. To demonstrate the potential of this approach, the fluorescent molecule sensor is conjugated to a human epidermal growth factor receptor 2 (HER2)-specific antibody and used to investigate the spatiotemporal behavior of HER2 clustering in the membrane of HER2-overexpressing breast cancer cells. Notably, the disruption of HER2 clusters in response to an FDA-approved monoclonal antibody therapeutic (Trastuzumab) is successfully detected using a simple widefield fluorescent microscope. While the sensor demonstrated here is optimized for sensing HER2 clustering, it is an easily adaptable platform. Moreover, given the compatibility with widefield imaging, the system has the potential to be used with high-throughput imaging techniques, accelerating investigations into membrane protein spatiotemporal organization.

Cell Membrane-Anchored DNA Nanoinhibitor for Inhibition of Receptor Tyrosine Kinase Signaling Pathways via Steric Hindrance and Lysosome-Induced Protein Degradation

Receptor tyrosine kinase (RTK) plays a crucial role in cancer progression, and it has been identified as a key drug target for cancer targeted therapy. Although traditional RTK-targeting drugs are effective, there are some limitations that potentially hinder the further development of RTK-targeting drugs. Therefore, it is urgently needed to develop novel, simple, and general RTK-targeting inhibitors with a new mechanism of action for cancer targeted therapy. Here, a cell membrane-anchored RTK-targeting DNA nanoinhibitor is developed to inhibit RTK function. By using a DNA tetrahedron as a framework, RTK-specific aptamers as the recognition elements, and cholesterol as anchoring molecules, this DNA nanoinhibitor could rapidly anchor on the cell membrane and specifically bind to RTK. Compared with traditional RTK-targeting inhibitors, this DNA nanoinhibitor does not need to bind at a limited domain on RTK, which increases the possibilities of developing RTK inhibitors. With the cellular-mesenchymal to epithelial transition factor (c-Met) as a target RTK, the DNA nanoinhibitor can not only induce steric hindrance effects to inhibit c-Met activation but also reduce the c-Met level via lysosome-mediated protein degradation and thus inhibition of c-Met signaling pathways and related cell behaviors. Moreover, the DNA nanoinhibitor is feasible for other RTKs by just replacing aptamers. This work may provide a novel, simple, and general RTK-targeting nanoinhibitor and possess great value in RTK-targeted cancer therapy.

Location, location, location: Protein kinase nanoclustering for optimised signalling output

Protein kinases (PKs) are proteins at the core of cellular signalling and are thereby responsible for most cellular physiological processes and their regulations. As for all intracellular proteins, PKs are subjected to Brownian thermal energy that tends to homogenise their distribution throughout the volume of the cell. To access their substrates and perform their critical functions, PK localisation is therefore tightly regulated in space and time, relying upon a range of clustering mechanisms. These include post-translational modifications, protein-protein and protein-lipid interactions, as well as liquid-liquid phase separation, allowing spatial restriction and ultimately regulating access to their substrates. In this review, we will focus on key mechanisms mediating PK nanoclustering in physiological and pathophysiological processes. We propose that PK nanoclusters act as a cellular quantal unit of signalling output capable of integration and regulation in space and time. We will specifically outline the various super-resolution microscopy approaches currently used to elucidate the composition and mechanisms driving PK nanoscale clustering and explore the pathological consequences of altered kinase clustering in the context of neurodegenerative disorders, inflammation, and cancer.

Targeting Receptor Tyrosine Kinases as a Novel Strategy for the Treatment of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) comprises a group of aggressive and heterogeneous breast carcinoma. Chemotherapy is the mainstay for the treatment of triple-negative tumors. Nevertheless, the success of chemotherapeutic treatments is limited by their toxicity and development of acquired resistance leading to therapeutic failure and tumor relapse. Hence, there is an urgent need to explore novel targeted therapies for TNBC. Receptor tyrosine kinases (RTKs) are a family of transmembrane receptors that are key regulators of intracellular signaling pathways controlling cell proliferation, differentiation, survival, and motility. Aberrant activity and/or expression of several types of RTKs have been strongly connected to tumorigenesis. RTKs are frequently overexpressed and/or deregulated in triple-negative breast tumors and are further associated with tumor progression and reduced survival in patients. Therefore, targeting RTKs could be an appealing therapeutic strategy for the treatment of TNBC. This review summarizes the current evidence regarding the antitumor activity of RTK inhibitors in preclinical models of TNBC. The review also provides insights into the clinical trials evaluating the use of RTK inhibitors for the treatment of patients with TNBC.

Controlled Plasma Membrane Delivery of FGFR1 and Modulation of Signaling by a Novel Regulated Anterograde RTK Transport Pathway

How human FGFR1 localizes to the PM is unknown. Currently, it is assumed that newly synthesized FGFR1 is continuously delivered to the PM. However, evidence indicates that FGFR1 is mostly sequestered in intracellular post-Golgi vesicles (PGVs) under normal conditions. In this report, live-cell imaging and total internal reflection fluorescence microscopy (TIRFM) were employed to study the dynamics of these FGFR1-positive vesicles. We designed recombinant proteins to target different transport components to and from the FGFR1 vesicles. Mouse embryoid bodies (mEBs) were used as a 3D model system to confirm major findings. Briefly, we found that Rab2a, Rab6a, Rab8a, RalA and caveolins are integral components of FGFR1-positive vesicles, representing a novel compartment. While intracellular sequestration prevented FGFR1 activation, serum starvation and hypoxia stimulated PM localization of FGFR1. Under these conditions, FGFR1 C-terminus acts as a scaffold to assemble proteins to (i) inactivate Rab2a and release sequestration, and (ii) assemble Rab6a for localized activation of Rab8a and RalA-exocyst to deliver the receptor to the PM. This novel pathway is named Regulated Anterograde RTK Transport (RART). This is the first instance of RTK regulated through control of PM delivery.

The Prognostic and Functional Impact of Sprouty 2 Expression in Non-small Cell Lung Cancer

OBJECTIVE

We represent Sprouty 2 (Spry2) expression analysis and its association with key driver mutations and clinical features of patients with non-small cell lung cancer as the largest ex vivo data.

METHODS

The strength of Spry2 expression was evaluated using the immunoreactivity score (IRS), which was calculated using the following formula: IRS=(staining intensity score) SI×(percentage of positively stained cells) PP. The median IRS score was defined as the cutoff value. Patients were grouped as "weak immunoreactivity score" (IRS: 0 to 4) or "strong immunoreactivity score" (IRS: ≥4) with respect to the IRS score.

RESULTS

The intensity and percentage of Spry2 staining were significantly lower in tumor tissues than in normal lung tissues ( P <0.0001). Patients' characteristics were similar for both groups, except for smoking status and, brain and lymph node metastasis. Overall survival of patients with a strong immunoreactivity score was significantly lower than those with a weak immunoreactivity score among metastatic patients (6.9 mo vs. 13.6, P =0.023) and adenocarcinoma histology (7.0 mo vs. not reached, P =0.003).

CONCLUSION

Spry2 expression was lower in tumor tissues than in normal lung parenchyma. Increased expression of Spry2 is associated with poor prognosis. There were no significant associations between epidermal growth factor receptor, anaplastic lymphoma kinase, or c-ros oncogene 1 rearrangement and Spry2 expression. Despite the absence of KRAS mutational analysis, the clinical and epidemiological features of patients suggested that KRAS mutation might be an underlying determinant factor of the functional role of Spry2 in non-small cell lung cancer.

Synthesizing biomaterials in living organisms

Living organisms fabricate biomacromolecules such as DNA, RNA, and proteins by the self-assembly process. The research on the mechanism of biomacromolecule formation also inspires the exploration of in vivo synthesized biomaterials. By elaborate design, artificial building blocks or precursors can self-assemble or polymerize into functional biomaterials within living organisms. In recent decades, these so-called in vivo synthesized biomaterials have achieved extensive applications in cell-fate manipulation, disease theranostics, bioanalysis, cellular surface engineering, and tissue regeneration. In this review, we classify strategies for in vivo synthesis into non-covalent, covalent, and genetic types. The development of these approaches is based on the chemical principles of supramolecular chemistry and synthetic chemistry, biological cues such as enzymes and microenvironments, and the means of synthetic biology. By summarizing the design principles in detail, some insights into the challenges and opportunities in this field are provided to  enlighten further research.

EMP3 sustains oncogenic EGFR/CDK2 signaling by restricting receptor degradation in glioblastoma

Epithelial membrane protein 3 (EMP3) is an N-glycosylated tetraspanin with a putative trafficking function. It is highly expressed in isocitrate dehydrogenase-wild-type glioblastoma (IDH-wt GBM), and its high expression correlates with poor survival. However, the exact trafficking role of EMP3 and how it promotes oncogenic signaling in GBM remain unclear. Here, we show that EMP3 promotes EGFR/CDK2 signaling by regulating the trafficking and enhancing the stability of EGFR. BioID2-based proximity labeling revealed that EMP3 interacts with endocytic proteins involved in the vesicular transport of EGFR. EMP3 knockout (KO) enhances epidermal growth factor (EGF)-induced shuttling of EGFR into RAB7 + late endosomes, thereby promoting EGFR degradation. Increased EGFR degradation is rescued by the RAB7 negative regulator and novel EMP3 interactor TBC1D5. Phosphoproteomic and transcriptomic analyses further showed that EMP3 KO converges into the inhibition of the cyclin-dependent kinase CDK2 and the repression of EGFR-dependent and cell cycle transcriptional programs. Phenotypically, EMP3 KO cells exhibit reduced proliferation rates, blunted mitogenic response to EGF, and increased sensitivity to the pan-kinase inhibitor staurosporine and the EGFR inhibitor osimertinib. Furthermore, EGFR-dependent patient-derived glioblastoma stem cells display a transcriptomic signature consistent with reduced CDK2 activity, as well as increased susceptibility to CDK2 inhibition upon EMP3 knockdown. Lastly, using TCGA data, we showed that GBM tumors with high EMP3 expression have increased total and phosphorylated EGFR levels. Collectively, our findings demonstrate a novel EMP3-dependent mechanism by which EGFR/CDK2 activity is sustained in GBM. Consequently, EMP3's stabilizing effect provides an additional layer of tumor cell resistance against targeted kinase inhibition.

Multivalent protein-drug conjugates - An emerging strategy for the upgraded precision and efficiency of drug delivery to cancer cells

With almost 20 million new cases per year, cancer constitutes one of the most important challenges for public health systems. Unlike traditional chemotherapy, targeted anti-cancer strategies employ sophisticated therapeutics to precisely identify and attack cancer cells, limiting the impact of drugs on healthy cells and thereby minimizing the unwanted side effects of therapy. Protein drug conjugates (PDCs) are a rapidly growing group of targeted therapeutics, composed of a cancer-recognition factor covalently coupled to a cytotoxic drug. Several PDCs, mainly in the form of antibody-drug conjugates (ADCs) that employ monoclonal antibodies as cancer-recognition molecules, are used in the clinic and many PDCs are currently in clinical trials. Highly selective, strong and stable interaction of the PDC with the tumor marker, combined with efficient, rapid endocytosis of the receptor/PDC complex and its subsequent effective delivery to lysosomes, is critical for the efficacy of targeted cancer therapy with PDCs. However, the bivalent architecture of contemporary clinical PDCs is not optimal for tumor receptor recognition or PDCs internalization. In this review, we focus on multivalent PDCs, which represent a rapidly evolving and highly promising therapeutics that overcome most of the limitations of current bivalent PDCs, enhancing the precision and efficiency of drug delivery to cancer cells. We present an expanding set of protein scaffolds used to generate multivalent PDCs that, in addition to folding into well-defined multivalent molecular structures, enable site-specific conjugation of the cytotoxic drug to ensure PDC homogeneity. We provide an overview of the architectures of multivalent PDCs developed to date, emphasizing their efficacy in the targeted treatment of various cancers.

A transient vesicular glue for amplification and temporal regulation of biocatalytic reaction networks

Regulation of enzyme activity and biocatalytic cascades on compartmentalized cellular components is key to the adaptation of cellular processes such as signal transduction and metabolism in response to varying external conditions. Synthetic molecular glues have enabled enzyme inhibition and regulation of protein-protein interactions. So far, all the molecular glue systems based on covalent interactions operated under steady-state conditions. To emulate dynamic biological processes under dissipative conditions, we introduce herein a transient supramolecular glue with a controllable lifetime. The transient system uses multivalent supramolecular interactions between guanidinium group-bearing surfactants and adenosine triphosphate (ATP), resulting in bilayer vesicle structures. Unlike the conventional chemical agents for dissipative assemblies, ATP here plays the dual role of providing a structural component for the assembly as well as presenting active functional groups to "glue" enzymes on the surface. While gluing of the enzymes on the vesicles achieves augmented catalysis, oscillation of ATP concentration allows temporal control of the catalytic activities similar to the dissipative cellular nanoreactors. We further demonstrate temporal upregulation and control of complex biocatalytic reaction networks on the vesicles. Altogether, the temporal activation of biocatalytic cascades on the dissipative vesicular glue presents an adaptable and dynamic system emulating heterogeneous cellular processes, opening up avenues for effective protocell construction and therapeutic interventions.

Oncogenic long noncoding RNA LINC02283 enhances PDGF receptor A-mediated signaling and drives glioblastoma tumorigenesis

BACKGROUND

Long noncoding RNAs (lncRNAs) regulate the etiology of complex diseases and cancers, including glioblastoma (GBM). However, lncRNA-based therapies are limited because the mechanisms of action of many lncRNAs with their binding partners are not completely understood.

METHODS

We used transcriptomic and genomic data to analyze correlations between LINC02283 and PDGFRA (platelet-derived growth factor receptor A). The biological functions of the novel lncRNA were assessed in vivo using patient-derived glioma stem-like cells (GSCs), and orthotopic GBM xenografts. Immunoblotting, qRT-PCR, RNA pull down, crosslinked RNA immunoprecipitation, fluorescence in situ hybridization, and antisense oligo-mediated knockdown were performed to explore the regulation of LINC02283 on PDGFRA signaling. Expression of LINC02283 in clinical samples was assessed using pathologically diagnosed GBM patient samples.

RESULTS

We identified a novel oncogenic lncRNA, LINC02283, that is highly expressed in the PDGFRA mutation-driven cohort of glioma patients and associated with worse prognosis. LINC02283 gene co-amplifies with the PDGFRA locus and shows high correlation with PDGFRA expression. Deprivation of LINC02283 in GSCs with PDGFRA amplification mutation, attenuated tumorigenicity and enhanced survival in orthotopic GBM xenograft models, while overexpression of LINC02283 in GSCs with wild-type PDGFRA, enhances PDGFRA signaling, and decreases survival. Further, LINC02283 interacts with PDGFRA to enhance its signaling and that of its downstream targets AKT and ERK, thus promoting oncogenesis in GBM.

CONCLUSIONS

Our results provide strong evidence of LINC02283 as a regulator of PDGFRA oncogenic activity and GBM malignancy and support the potential of lncRNAs as possible therapeutic targets.

Rapid determination of the presence of EGFR mutations with DNA-based nanocalipers

Selecting 1st-line treatment for lung cancer is currently a binary choice, either chemotherapy or targeted medicine, depending on whether EGFR mutations exist. Next-generation sequencing is fully capable of accurately identifying EGFR mutations and guiding the usage of tyrosine kinase inhibitors, but it is highly expensive. Moreover, as the sequencing is not helpful for patients with wild-type EGFR, the long wait for sequencing may delay the chemotherapy and correspondingly increase the risks of cancer progression. To address this issue, a new method for rapidly determining the presence of EGFR mutations is developed in this study. A series of DNA origami-engineered nanocalipers are designed and constructed to determine the EGFR spatial distribution of either mutated EGFR or wild-type EGFR lung cancer cells. The experimental results on cancer cell lines and 9 clinical tissue samples show that compared with wild-type EGFR cells, mutated EGFR cells have narrower EGFR spacing. Hence, the DNA nanocalipers are demonstrated to be capable of determining the presence of EGFR mutations and shrinking the detection period from weeks to hours, compared with sequencing. For determining EGFR mutation status in 9 clinical samples, DNA nanocalipers show 100% consistency with next-generation sequencing.

KITENIN promotes aerobic glycolysis through PKM2 induction by upregulating the c-Myc/hnRNPs axis in colorectal cancer

PURPOSE

The oncoprotein KAI1 C-terminal interacting tetraspanin (KITENIN; vang-like 1) promotes cell metastasis, invasion, and angiogenesis, resulting in shorter survival times in cancer patients. Here, we aimed to determine the effects of KITENIN on the energy metabolism of human colorectal cancer cells.

EXPERIMENTAL DESIGN

The effects of KITENIN on energy metabolism were evaluated using in vitro assays. The GEPIA web tool was used to extrapolate the clinical relevance of KITENIN in cancer cell metabolism. The bioavailability and effect of the disintegrator of KITENIN complex compounds were evaluated by LC-MS, in vivo animal assay.

RESULTS

KITENIN markedly upregulated the glycolytic proton efflux rate and aerobic glycolysis by increasing the expression of GLUT1, HK2, PKM2, and LDHA. β-catenin, CD44, CyclinD1 and HIF-1A, including c-Myc, were upregulated by KITENIN expression. In addition, KITENIN promoted nuclear PKM2 and PKM2-induced transactivation, which in turn, increased the expression of downstream mediators. This was found to be mediated through an effect of c-Myc on the transcription of hnRNP isoforms and a switch to the M2 isoform of pyruvate kinase, which increased aerobic glycolysis. The disintegration of KITENIN complex by silencing the KITENIN or MYO1D downregulated aerobic glycolysis. The disintegrator of KITENIN complex compound DKC1125 and its optimized form, DKC-C14S, exhibited the inhibition activity of KITENIN-mediated aerobic glycolysis in vitro and in vivo.

CONCLUSIONS

The oncoprotein KITENIN induces PKM2-mediated aerobic glycolysis by upregulating the c-Myc/hnRNPs axis.

Controlled spatial characteristics of ligands on nanoparticles: Determinant of cellular functions

Interactions of various ligands and receptors have been extensively investigated because they regulate a series of signal transduction leading to various functional cellular outcomes. The receptors on cell membrane recognize their specific ligands, resulting in specific binding between ligands and receptors. Accumulating evidence reveals that the receptors recognize the difference on the spatial characteristics of ligands as well as the types of ligands. Thus, control on spatial characteristics of multiple ligands presented on therapeutic nanoparticles is believed to impact the cellular functions. Specifically, the localized and multivalent distribution of ligands on nanoparticles can induce receptor oligomerization and receptor clustering, controlling intensity or direction of signal transduction cascades. Here, we will introduce recent studies on the use of material-based nanotechnology to control spatial characteristics of ligands and their effect on cellular functions. These therapeutic nanoparticles with controlled spatial characteristics of ligands may be a promising strategy for maximized therapeutic outcome.

Spatial Control of Receptor Dimerization Using Programmable DNA Nanobridge

Receptor dimerization is an essential mechanism for the activation of most receptor tyrosine kinases by ligands. Thus, regulating the nanoscale spatial distribution of cell surface receptors is significant for studying both intracellular signaling pathways and cellular behavior. However, there are currently very limited methods for exploring the effects of modulating the spatial distribution of receptors on their function by using simple tools. Herein, we developed an aptamer-based double-stranded DNA bridge acting as "DNA nanobridge", which regulates receptor dimerization by changing the number of bases. On this basis, we confirmed that the different nanoscale arrangements of the receptor can influence receptor function and its downstream signals. Among them, the effect gradually changed from helping to activate to inhibiting as the length of DNA nanobridge increased. Hence, it can not only effectively inhibit receptor function and thus affect cellular behavior but also serve as a fine-tuning tool to get the desired signal activity. Our strategy is promising to provide insight into the action of receptors in cell biology from the perspective of spatial distribution.

ABCA1 transporter promotes the motility of human melanoma cells by modulating their plasma membrane organization

BACKGROUND

Melanoma is one of the most aggressive and deadliest skin tumor. Cholesterol content in melanoma cells is elevated, and a portion of it accumulates into lipid rafts. Therefore, the plasma membrane cholesterol and its lateral organization might be directly linked with tumor development. ATP Binding Cassette A1 (ABCA1) transporter modulates physico-chemical properties of the plasma membrane by modifying cholesterol distribution. Several studies linked the activity of the transporter with a different outcome of tumor progression depending on which type. However, no direct link between human melanoma progression and ABCA1 activity has been reported yet.

METHODS

An immunohistochemical study on the ABCA1 level in 110 patients-derived melanoma tumors was performed to investigate the potential association of the transporter with melanoma stage of progression and prognosis. Furthermore, proliferation, migration and invasion assays, extracellular-matrix degradation assay, immunochemistry on proteins involved in migration processes and a combination of biophysical microscopy analysis of the plasma membrane organization of Hs294T human melanoma wild type, control (scrambled), ABCA1 Knockout (ABCA1 KO) and ABCA1 chemically inactivated cells were used to study the impact of ABCA1 activity on human melanoma metastasis processes.

RESULTS

The immunohistochemical analysis of clinical samples showed that high level of ABCA1 transporter in human melanoma is associated with a poor prognosis. Depletion or inhibition of ABCA1 impacts invasion capacities of aggressive melanoma cells. Loss of ABCA1 activity partially prevented cellular motility by affecting active focal adhesions formation via blocking clustering of phosphorylated focal adhesion kinases and active integrin β3. Moreover, ABCA1 activity regulated the lateral organization of the plasma membrane in melanoma cells. Disrupting this organization, by increasing the content of cholesterol, also blocked active focal adhesion formation.

CONCLUSION

Human melanoma cells reorganize their plasma membrane cholesterol content and organization via ABCA1 activity to promote motility processes and aggressiveness potential. Therefore, ABCA1 may contribute to tumor progression and poor prognosis, suggesting ABCA1 to be a potential metastatic marker in melanoma.

Kremen2 drives the progression of non-small cell lung cancer by preventing SOCS3-mediated degradation of EGFR

BACKGROUND

The transmembrane receptor Kremen2 has been reported to participate in the tumorigenesis and metastasis of gastric cancer. However, the role of Kremen2 in non-small cell lung cancer (NSCLC) and the underlying mechanism remain unclear. This study aimed to explore the biological function and regulatory mechanism of Kremen2 in NSCLC.

METHODS

The correlation between Kremen2 expression and NSCLC was assessed by analyzing the public database and clinical tissue samples. Colony formation and EdU assays were performed to examine cell proliferation. Transwell and wound healing assays were used to observe cell migration ability. Tumor-bearing nude mice and metastatic tumor models were used to detect the in vivo tumorigenic and metastatic abilities of the NSCLC cells. An immunohistochemical assay was used to detect the expression of proliferation-related proteins in tissues. Western blot, immunoprecipitation and immunofluorescence were conducted to elucidate the Kremen2 regulatory mechanisms in NSCLC.

RESULTS

Kremen2 was highly expressed in tumor tissues from NSCLC patients and was positively correlated with a poor patient prognosis. Knockout or knockdown of Kremen2 inhibited cell proliferation and migration ability of NSCLC cells. In vivo knockdown of Kremen2 inhibited the tumorigenicity and number of metastatic nodules of NSCLC cells in nude mice. Mechanistically, Kremen2 interacted with suppressor of cytokine signaling 3 (SOCS3) to maintain the epidermal growth factor receptor (EGFR) protein levels by preventing SOCS3-mediated ubiquitination and degradation of EGFR, which, in turn, promoted activation of the PI3K-AKT and JAK2-STAT3 signaling pathways.

CONCLUSIONS

Our study identified Kremen2 as a candidate oncogene in NSCLC and may provide a potential target for NSCLC treatment.

Biased activation of the receptor tyrosine kinase HER2

HER2 belongs to the ErbB sub-family of receptor tyrosine kinases and regulates cellular proliferation and growth. Different from other ErbB receptors, HER2 has no known ligand. Activation occurs through heterodimerization with other ErbB receptors and their cognate ligands. This suggests several possible activation paths of HER2 with ligand-specific, differential response, which has so far remained unexplored. Using single-molecule tracking and the diffusion profile of HER2 as a proxy for activity, we measured the activation strength and temporal profile in live cells. We found that HER2 is strongly activated by EGFR-targeting ligands EGF and TGFα, yet with a distinguishable temporal fingerprint. The HER4-targeting ligands EREG and NRGβ1 showed weaker activation of HER2, a preference for EREG, and a delayed response to NRGβ1. Our results indicate a selective ligand response of HER2 that may serve as a regulatory element. Our experimental approach is easily transferable to other membrane receptors targeted by multiple ligands.

Targeting receptor tyrosine kinases in ovarian cancer: Genomic dysregulation, clinical evaluation of inhibitors, and potential for combinatorial therapies

Epithelial ovarian cancer (EOC) remains one of the leading causes of cancer-related deaths among women worldwide. Receptor tyrosine kinases (RTKs) have long been sought as therapeutic targets for EOC, as they are frequently hyperactivated in primary tumors and drive disease relapse, progression, and metastasis. More recently, these oncogenic drivers have been implicated in EOC response to poly(ADP-ribose) polymerase (PARP) inhibitors and epigenome-interfering agents. This evidence revives RTKs as promising targets for therapeutic intervention of EOC. This review summarizes recent studies on the role of RTKs in EOC malignancy and the use of their inhibitors for clinical treatment. Our focus is on the ERBB family, c-Met, and VEGFR, as they are linked to drug resistance and targetable using commercially available drugs. The importance of these RTKs and their inhibitors is highlighted by their impact on signal transduction and intratumoral heterogeneity in EOC and successful use as maintenance therapy in the clinic through suppression of the VEGF/VEGFR axis. Finally, the therapeutic potential of RTK inhibitors is discussed in the context of combinatorial targeting via co-inhibiting proliferative and anti-apoptotic pathways, epigenomic/transcriptional programs, and harnessing the efficacy of PARP inhibitors and programmed cell death 1/ligand 1 immune checkpoint therapies.

Ligand-independent receptor clustering modulates transmembrane signaling: a new paradigm

Cell-surface receptors mediate communication between cells and their environment. Lateral membrane organization and dynamic receptor cluster formation are fundamental in signal transduction and cell signaling. However, it is not yet fully understood how receptor clustering modulates a wide variety of physiologically relevant processes. Recent growing evidence indicates that biological responses triggered by membrane receptors can be modulated even in the absence of the natural receptor ligand. We review the most recent findings on how ligand-independent receptor clustering can regulate transmembrane signaling. We discuss the latest technologies to control receptor assembly, such as DNA nanotechnology, optogenetics, and optochemistry, focusing on the biological relevance and unraveling of ligand-independent signaling.

Axl and Vascular Endothelial Growth Factor Receptors Exhibit Variations in Membrane Localization and Heterogeneity Across Monolayer and Spheroid High-Grade Serous Ovarian Cancer Models

Vascular endothelial growth factor receptors (VEGFRs) and Axl are receptor tyrosine kinases (RTK) that are targeted in ovarian cancer therapy. Two-dimensional monolayer culture and three-dimensional spheroids are common models for RTK-targeted drug screening: monolayers are simple and economical while spheroids include several genetic and histological tumor features. RTK membrane localization dictates RTK signaling and drug response, however, it is not characterized in these models. We quantify plasma membrane RTK concentrations and show differential RTK abundance and heterogeneity in monolayers versus spheroids. We show VEGFR1 concentrations on the plasma membrane to be 10 times higher in OVCAR8 spheroids than in monolayers; OVCAR8 spheroids are more heterogeneous than monolayers, exhibiting a bimodal distribution of a low-Axl (6200/cell) and a high-Axl subpopulation (25,000/cell). In addition, plasma membrane Axl concentrations differ by 100 times between chemosensitive (OVCAR3) and chemoresistant (OVCAR8) cells and by 10 times between chemoresistant cell lines (OVCAR5 vs. OVCAR8). These systematic findings can guide ovarian cancer model selection for drug screening.

DNA-Programed Plasmon Rulers Decrypt Single-Receptor Dimerization on Cell Membrane

Decrypting the dynamics of receptor dimerization on cell membranes bears great importance in identifying the mechanisms regulating diverse cellular activities. In this regard, long-term monitoring of single-molecule behavior during receptor dimerization allows deepening insight into the dimerization process and tracking of the behavior of individual receptors, yet this remains to be realized. Herein, real-time observation of the receptor tyrosine kinases family (RTKs) at single-molecule level based on plasmon rulers was achieved for the first time, which enabled precise regulation and dynamic monitoring of the dimerization process by DNA programming with excellent photostability. Additionally, those nanoprobes demonstrated substantial application in the regulation of RTKs protein dimerization/phosphorylation and activation of downstream signaling pathways. The proposed nanoprobes hold considerable potential for elucidating the molecular mechanisms of single-receptor dimerization as well as the conformational transitions upon dimerization, providing a new paradigm for the precise manipulation and monitoring of specific single-receptor crosslink events in biological systems.

Using Micropatterned Supported Lipid Bilayers to Probe the Mechanosensitivity of Signaling Receptors

The ligand-receptor complexes in the cell-cell and cell-ECM interfaces mediate the mechanical coupling of cells to their microenvironment and transduce downstream signals to modulate cell functions. In this chapter I describe a microfabrication strategy to prepare a substrate of spatially segregated supported lipid bilayers and ECM components on which cells can form juxtacrine receptor signaling complexes and integrin adhesions simultaneously. This platform is specifically applicable for microscopically monitoring the signal transduction of each receptor, as well as the modulatory effects of receptor signaling on integrin adhesions and cell behaviors.

The Role of the Adapter Protein Anks1a in the Regulation of Breast Cancer Cell Motility

Epithelial-mesenchymal transition (EMT) is a critical step in tumor progression that leads to the acquisition by cancer cells the capacity for migration using the mesenchymal motility mode regulated by the Rac→WAVE→Arp2/3 signaling pathway. Earlier it was shown that proteins interacting with Rac can regulate mesenchymal migration and thus determine the metastatic potential of the cells. The search for new regulators of cell migration is an important theoretical and practical task. The adaptor protein Anks1a is one of the proteins interacting with Rac, whose expression is altered in many types of tumors. The aim of this study was to find whether Anks1a affects the migration of cancer cells and to identify the mechanism underlying this effect. It was suggested that Anks1a can influence cancer cell migration either as a Rac1 effector or by activating human epidermal growth factor receptor 2 (HER2) exchange. We investigated how upregulation and inhibition of Anks1a expression affected migration of breast cancer cells with different HER2 status. Anks1a was shown to interact with the activated form of Rac1. In the MDA-MB-231 cells (triple negative cancer), which lack HER2, Anks1a accumulated at the active cell edge, which is characterized by enrichment with active Rac1, whereas no such accumulation was observed in the HER2-overexpressing SK-BR-3 cells. Downregulation of the ANKS1a expression with esiRNA had almost no effect on the cancer cell motility, except a slight increase in the average migration rate of MDA-MB-231 cells. Among three cell lines tested, overexpression of Anks1a increased the migration rate of HER2-overexpressng SK-BR-3 cells only. We showed that Anks1a is an effector of activated Rac1, but its influence on the cell migration in this capacity was minimal, at least in the studied breast cancer cells. Anks1a affected the motility of breast cancer cells due to its involvement in the EGF receptor exchange.

Unravelling cell migration: defining movement from the cell surface

Cell motility is essential for life and development. Unfortunately, cell migration is also linked to several pathological processes, such as cancer metastasis. Cells' ability to migrate relies on many actors. Cells change their migratory strategy based on their phenotype and the properties of the surrounding microenvironment. Cell migration is, therefore, an extremely complex phenomenon. Researchers have investigated cell motility for more than a century. Recent discoveries have uncovered some of the mysteries associated with the mechanisms involved in cell migration, such as intracellular signaling and cell mechanics. These findings involve different players, including transmembrane receptors, adhesive complexes, cytoskeletal components , the nucleus, and the extracellular matrix. This review aims to give a global overview of our current understanding of cell migration.

Dynamics and Patterning of 5-Hydroxytryptamine 2 Subtype Receptors in JC Polyomavirus Entry

The organization and dynamics of plasma membrane receptors are a critical link in virus-receptor interactions, which finetune signaling efficiency and determine cellular responses during infection. Characterizing the mechanisms responsible for the active rearrangement and clustering of receptors may aid in developing novel strategies for the therapeutic treatment of viruses. Virus-receptor interactions are poorly understood at the nanoscale, yet they present an attractive target for the design of drugs and for the illumination of viral infection and pathogenesis. This study utilizes super-resolution microscopy and related techniques, which surpass traditional microscopy resolution limitations, to provide both a spatial and temporal assessment of the interactions of human JC polyomavirus (JCPyV) with 5-hydroxytrypamine 2 receptors (5-HT₂Rs) subtypes during viral entry. JCPyV causes asymptomatic kidney infection in the majority of the population and can cause fatal brain disease, and progressive multifocal leukoencephalopathy (PML), in immunocompromised individuals. Using Fluorescence Photoactivation Localization Microscopy (FPALM), the colocalization of JCPyV with 5-HT₂ receptor subtypes (5-HT_2A, 5-HT_2B, and 5-HT_2C) during viral attachment and viral entry was analyzed. JCPyV was found to significantly enhance the clustering of 5-HT₂ receptors during entry. Cluster analysis of infected cells reveals changes in 5-HT₂ receptor cluster attributes, and radial distribution function (RDF) analyses suggest a significant increase in the aggregation of JCPyV particles colocalized with 5-HT₂ receptor clusters in JCPyV-infected samples. These findings provide novel insights into receptor patterning during viral entry and highlight improved technologies for the future development of therapies for JCPyV infection as well as therapies for diseases involving 5-HT₂ receptors.

Kinase perturbations redirect mitochondrial function in cancer

Protein kinases take the center stage in numerous signaling pathways by phosphorylating compartmentalized protein substrates for controlling cell proliferation, cell cycle and metabolism. Kinase dysfunctions have been linked to numerous human diseases such as cancer. This has led to the development of kinase inhibitors which aim to target oncogenic kinase activities. The specificity of the cancer blockers depends on the range of targeted kinases. Therefore, the question arises of how cell-type-specific off-target effects impair the specificities of cancer drugs. Blockade of kinase activities has been shown to converge on the energetic organelle, the mitochondria. In this review, we highlight examples of selected major kinases that impact mitochondrial signaling. Further, we discuss pharmacological strategies to target kinase activities linked to cancer progression and redirecting mitochondrial function. Finally, we propose that cell-based recordings of mitochondrial bioenergetic states might predict off-target or identify specific on-target effects of kinase inhibitors.

Spatially Reprogramed Receptor Organization to Switch Cell Behavior Using a DNA Origami-Templated Aptamer Nanoarray

Receptor oligomerization is a highly complex molecular process that modulates divergent cell signaling. However, there is a lack of molecular tools for systematically interrogating how receptor oligomerization governs the signaling response. Here, we developed a DNA origami-templated aptamer nanoarray (DOTA) that enables precise programming of the oligomerization of receptor tyrosine kinases (RTK) with defined valency, distribution, and stoichiometry at the ligand-receptor interface. The DOTA allows for advanced receptor manipulations by arraying either monomeric aptamer ligands (mALs) that oligamerize receptor monomers to elicit artificial signaling or dimeric aptamer ligands (dALs) that preorganize the receptor dimer to recapitulate natural activation. We demonstrated that the multivalency and nanoscale spacing of receptor oligomerization coordinately influence the activation level of receptor tyrosine kinase signaling. Furthermore, we illustrated that DOTA-modulated receptor oligomerization could function as a signaling switch to promote the transition from epithelia to mesenchymal-like cells, demonstrating robust control over cellular behaviors. Together, we present a versatile all-in-one DNA nanoplatform for the systematical investigation and regulation of receptor-mediated cellular response.

Lipid Metabolism and Homeostasis in Patients with Neuroendocrine Neoplasms: From Risk Factor to Potential Therapeutic Target

Lipid metabolism is known to be involved in tumorigenesis and disease progression in many common cancer types, including colon, lung, breast and prostate, through modifications of lipid synthesis, storage and catabolism. Furthermore, lipid alterations may arise as a consequence of cancer treatment and may have a role in treatment resistance. Neuroendocrine neoplasms (NENs) are a heterogeneous group of malignancies with increasing incidence, whose mechanisms of cancer initiation and progression are far from being fully understood. Alterations of lipid metabolism may be common across various cancer types, but data about NENs are scattered and heterogeneous. Herein, we provide an overview of the relevant literature on lipid metabolism and alterations in NENs. The available evidence both in basic and clinical research about lipid metabolism in NENs, including therapeutic effects on lipid homeostasis, are summarized. Additionally, the potential of targeting the lipid profile in NEN therapy is also discussed, and areas for further research are proposed.

Sphingomyelin synthase 2 is a positive regulator of the CSF1R-STAT3 pathway in pancreatic cancer-associated macrophage

Background: Tumor-associated macrophages (TAMs) are one of the most abundant immune cells in the pancreatic cancer stroma and are related to the poor prognosis of pancreatic ductal adenocarcinoma (PDAC) patients. Therefore, targeting tumor-associated macrophages is a possible strategy for the treatment of pancreatic cancer.

Purpose: We would like to investigate the role of sphingomyelin synthase 2 (SMS2) and the effect of the synthase 2 selective inhibitor YE2 in TAMs and the pancreatic tumor microenvironment. In addition, we also would like to investigate the mechanism by which YE2 attenuates macrophage M2 polarization.

Methods: YE2 was utilized to treat macrophages (in vitro) and mice (in vivo). Western blotting and real-time PCR were used to detect the protein levels and mRNA levels of macrophage M2 polarization markers and their downstream signaling pathways. Sphingomyelin synthase 2 gene knockout (KO) mice and their controls were used to establish a PANC-02 orthotopic pancreatic cancer model, and immune cell infiltration in the tumor tissue was analyzed by immunohistochemistry (IHC).

Results: We found that sphingomyelin synthase 2 mRNA expression is positively correlated with tumor-associated macrophages, the immunosuppressive microenvironment, and poor prognosis in pancreatic ductal adenocarcinoma patients. Sphingomyelin synthase 2 deficiency was confirmed to have an inhibitory effect on the growth of orthotopic PANC-02 tumors in vivo. The deficiency not only reduced the infiltration of tumor-associated macrophages but also regulated other immune components in the tumor microenvironment. In tissue culture, YE2 inhibited M2 polarization in both bone marrow-derived macrophages (BMDMs) and THP-1 macrophages and eliminated the protumor effect of M2 macrophages. In the mouse model, YE2 treatment reduced the infiltration of TAMs and regulated other immune components in the tumor microenvironment, slowing the progression of PANC-02 tumors. In terms of mechanism, we found that the inhibition of sphingomyelin synthase 2 could downregulate the expression of IL4Rα and CSF1R, thereby attenuating M2 polarization.

Conclusion: The sphingomyelin synthase 2 inhibitor YE2 or sphingomyelin synthase 2 deficiency can prevent macrophage M2 polarization in pancreatic cancer, and sphingomyelin synthase 2 could be a new potential target for the treatment of pancreatic cancer.

Non-canonical Regulation of EGFR by the Air Pollutant 9,10-Phenanthrenequinone

9,10-Phenanthrenequinone (9,10-PQ), a polycyclic aromatic hydrocarbon that is present in air pollutants, such as diesel exhaust gas and PM2.5, causes the production of excess reactive oxygen species. 9,10-PQ was recently shown to induce the activation of epidermal growth factor receptor (EGFR) by inhibiting protein tyrosine phosphatase 1B. In the present study, we focused on the non-canonical regulation of EGFR, including negative feedback and internalization. In contrast to previous findings, 9,10-PQ inhibited the constitutive tyrosine phosphorylation of EGFR via the mitogen-activated protein extracellular kinase (MEK)/extracellular signal-regulated kinase (ERK)-mediated phosphorylation of Thr-669 in EGFR-overexpressing A431 and MDA-MB-468 cells. In addition, 9,10-PQ induced the clathrin-mediated endocytosis of EGFR via the p38 phosphorylation of Ser-1015 in HeLa and A549 cells. These results revealed that 9,10-PQ strongly induced the non-canonical regulation of EGFR by activating mitogen-activated protein kinase (MAPK).

Involvement of microRNAs and their potential diagnostic, therapeutic, and prognostic role in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) accounts for 85%-90% of primary liver cancer. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by targeting the 3'UTR of mRNA. Abnormal expression and regulation of miRNAs are involved in the occurrence and progression of HCC, and miRNAs can also play a role in the diagnosis and treatment of HCC as oncogenes or tumor suppressors.

METHODS

In the past decades, a large number of studies have shown that miRNAs play an essential regulatory role in HCC and have potential as biomarkers for HCC. We reviewed the literature to summarize these studies.

RESULTS

By reviewing the literature, we retrospected the roles of miRNAs in the development, diagnosis, treatment, and prognosis of HCC, and put forward prospects for the further research on miRNAs in the precision treatment of HCC.

CONCLUSION

MicroRNAs are important regulators and biomarkers in the occurrence, progression, outcome, and treatment of HCC, and can provide new targets and strategies for improving the therapeutic effect of HCC.

A Multiscale Molecular Dynamic Analysis Reveals the Effect of Sialylation on EGFR Clustering in a CRISPR/Cas9-Derived Model

Bacterial and viral pathogens can modulate the glycosylation of key host proteins to facilitate pathogenesis by using various glycosidases, particularly sialidases. Epidermal growth factor receptor (EGFR) signaling is activated by ligand-induced receptor dimerization and oligomerization. Ligand binding induces conformational changes in EGFR, leading to clusters and aggregation. However, information on the relevance of EGFR clustering in the pattern of glycosylation during bacterial and viral invasion remains unclear. In this study, (1) we established CRISPR/Cas9-mediated GFP knock-in (EGFP-KI) HeLa cells expressing fluorescently tagged EGFR at close to endogenous levels to study EGF-induced EGFR clustering and molecular dynamics; (2) We studied the effect of sialylation on EGF-induced EGFR clustering and localization in live cells using a high content analysis platform and raster image correlation spectroscopy (RICS) coupled with a number and brightness (N&B) analysis; (3) Our data reveal that the removal of cell surface sialic acids by sialidase treatment significantly decreases EGF receptor clustering with reduced fluorescence intensity, number, and area of EGFR-GFP clusters per cell upon EGF stimulation. Sialylation appears to mediate EGF-induced EGFR clustering as demonstrated by the change of EGFR-GFP clusters in the diffusion coefficient and molecular brightness, providing new insights into the role of sialylation in EGF-induced EGFR activation; and (4) We envision that the combination of CRISPR/Cas9-mediated fluorescent tagging of endogenous proteins and fluorescence imaging techniques can be the method of choice for studying the molecular dynamics and interactions of proteins in live cells.

MicroRNA delivery systems in glioma therapy and perspectives: A systematic review

Gliomas are the deadliest of all primary brain tumors, and they constitute a serious global health problem. MicroRNAs (miRNAs) are gene expression regulators associated with glioma pathogenesis. Thus, miRNAs represent potential therapeutic agents for treating gliomas. However, miRNAs have not been established as part of the regular clinical armamentarium. This systemic review evaluates current molecular and pre-clinical studies with the aim of defining the most appealing supramolecular platform for administering therapeutic miRNA to patients with gliomas. An integrated analysis suggested that cationic lipid nanoparticles, functionalized with octa-arginine peptides, represent a potentially specific, practical, non-invasive intervention for treating gliomas. This supramolecular platform allows loading both hydrophilic (miRNA) and hydrophobic (anti-tumor drugs, like temozolomide) molecules. This systemic review is the first to describe miRNA delivery systems targeted to gliomas that integrate several types of molecules as active ingredients. Further experimental validation is warranted to confirm the practical value of miRNA delivery systems.

Synchronous intracellular delivery of EGFR-targeted antibody-drug conjugates by p38-mediated non-canonical endocytosis

Monoclonal antibodies targeting the epidermal growth factor receptor (EGFR), including cetuximab and panitumumab, have been used in clinic settings to treat cancer. They have also recently been applied to antibody–drug conjugates (ADCs); however, their clinical efficacy is limited by several issues, including lower internalization efficiency. The binding of cetuximab to the extracellular domain of EGFR suppresses ligand-induced events; therefore, we focus on ligand-independent non-canonical EGFR endocytosis for the delivery of ADCs into cells. Tumor necrosis factor-α (TNF-α) strongly induces the endocytosis of the cetuximab-EGFR complex within 15 min via the p38 phosphorylation of EGFR in a tyrosine kinase-independent manner. A secondary antibody conjugated with saporin, a ribosome-inactivating protein, also undergoes internalization with the complex and enhances its anti-proliferative activity. Anti-cancer agents, including cisplatin and temozolomide, also induce the p38-mediated internalization. The results of the present study demonstrate that synchronous non-canonical EGFR endocytosis may be a feasible strategy for promoting the therapeutic efficacy of EGFR-targeting ADCs in clinical settings.

Cancer-inducing niche: the force of chronic inflammation

The growth of cancer tissue is thought to be considered driven by a small subpopulation of cells, so-called cancer stem cells (CSCs). CSCs are located at the apex of a hierarchy in a cancer tissue with self-renewal, differentiation and tumorigenic potential that produce the progeny in the tissue. Although CSCs are generally believed to play a critical role in the growth, metastasis, and recurrence of cancers, the origin of CSCs remains to be reconsidered. We hypothesise that, chronic diseases, including obesity and diabetes, establish the cancer-inducing niche (CIN) that drives the undifferentiated/progenitor cells into CSCs, which then develop malignant tumours in vivo. In this context, a CIN could be traced to chronic inflammation that involves long-lasting tissue damage and repair after being exposed to factors such as cytokines and growth factors. This must be distinguished from the cancer microenvironment, which is responsible for cancer maintenance. The concept of a CIN is most important for cancer prevention as well as cancer therapy.

The Potential of Epigallocatechin Gallate (EGCG) in Targeting Autophagy for Cancer Treatment: A Narrative Review

Autophagy is an evolutionarily conserved process for the degradation of redundant or damaged cellular material by means of a lysosome-dependent mechanism, contributing to cell homeostasis and survival. Autophagy plays a multifaceted and context-dependent role in cancer initiation, maintenance, and progression; it has a tumor suppressive role in the absence of disease and is upregulated in cancer cells to meet their elevated metabolic demands. Autophagy represents a promising but challenging target in cancer treatment. Green tea is a widely used beverage with healthy effects on several diseases, including cancer. The bioactive compounds of green tea are mainly catechins, and epigallocatechin-gallate (EGCG) is the most abundant and biologically active among them. In this review, evidence of autophagy modulation and anti-cancer effects induced by EGCG treatment in experimental cancer models is presented. Reviewed articles reveal that EGCG promotes cytotoxic autophagy often through the inactivation of PI3K/Akt/mTOR pathway, resulting in apoptosis induction. EGCG pro-oxidant activity has been postulated to be responsible for its anti-cancer effects. In combination therapy with a chemotherapy drug, EGCG inhibits cell growth and the drug-induced pro-survival autophagy. The selected studies rightly claim EGCG as a valuable agent in cancer chemoprevention.

EGFR inhibition reverses epithelial‑mesenchymal transition, and decreases tamoxifen resistance via Snail and Twist downregulation in breast cancer cells

Tamoxifen resistance remains a major obstacle in the treatment of estrogen receptor (ER)‑positive breast cancer. In recent years, the crucial role of the epithelial‑mesenchymal transition (EMT) process in the development of drug resistance in breast cancer has been underlined. However, the central molecules inducing the EMT process during the development of tamoxifen resistance remain to be elucidated. In the present study, it was demonstrated that tamoxifen‑resistant breast cancer cells underwent EMT and exhibited an enhanced cell motility and invasive behavior. The inhibition of snail family transcriptional repressor 1 (Snail) and twist family BHLH transcription factor 1 (Twist) reversed the EMT phenotype and decreased the tamoxifen resistance, migration and invasion of tamoxifen‑resistant breast cancer cells. In addition, it was observed that the inhibition of epidermal growth factor receptor (EGFR) reversed the EMT phenotype in tamoxifen‑resistant MCF7 (MCF‑7/TR) cells via the downregulation of Snail and Twist. Notably, the EGFR inhibitor, gefitinib, decreased tamoxifen resistance, migration and invasion through the inhibition of Snail and Twist. On the whole, the results of the present study suggest that EGFR may be a promising therapeutic target for tamoxifen‑resistant breast cancer. Moreover, it was suggested that gefitinib may serve as a potent novel therapeutic strategy for breast cancer patients, who have developed tamoxifen resistance.