Biology subjects

Chen, X.

Publications and source records attributed to Chen, X..

At least 1,207 records · Page 67Linked to original sources

bioRxiv2021

Development of Large-Scale Brain Network Dynamics in Children

Functional brain networks require dynamic reconfiguration to support flexible cognitive function. However, the developmental principles shaping brain network dynamics remain poorly understood. Here, we report the longitudinal development of large-scale brain network dynamics during childhood and adolescence, and its connection with gene expression profiles. Using a multilayer network model, we show the temporally varying modular architecture of child brain networks, with higher network switching primarily in the association cortex and lower switching in the primary regions. This topographical profile exhibits progressive maturation, which manifests as reduced modular dynamics, particularly in the transmodal (e.g., default-mode and frontoparietal) and sensorimotor regions. These developmental refinements mediate age-related enhancements of global network segregation and are linked with the expression profiles of genes associated with the enrichment of ion transport and nucleobase-containing compound transport. These results highlight a progressive stabilization of brain dynamics, which expand our understanding of the neural mechanisms that underlie cognitive development.

neuroscience↗

bioRxiv2021

Development and validation of FootNet; a new kinematic algorithm to improve foot-strike and toe-off detection in treadmill running

The accurate detection of foot-strike and toe-off is often critical in the assessment of running biomechanics. The gold standard method for step event detection requires force data which are not always available. Although kinematics-based algorithms can also be used, their accuracy and generalisability are limited, often requiring corrections for speed or foot-strike pattern. The purpose of this study was to develop FootNet, a novel kinematics and deep learning-based algorithm for the detection of step events in treadmill running. Five treadmill running datasets were gathered and processed to obtain segment and joint kinematics, and to identify the contact phase within each gait cycle using force data. The proposed algorithm is based on a long short-term memory recurrent neural network and takes the distal tibia anteroposterior velocity, ankle dorsiflexion/plantar flexion angle and the anteroposterior and vertical velocities of the foot centre of mass as input features to predict the contact phase within a given gait cycle. The chosen model architecture underwent 5-fold cross-validation and the final model was tested in a subset of participants from each dataset (30%). Non-parametric Bland-Altman analyses (bias and [95% limits of agreement]) and root mean squared error (RMSE) were used to compare FootNet against the force data step event detection method. The association between detection errors and running speed, foot-strike angle and incline were also investigated. FootNet outperformed previously published algorithms (foot-strike bias = 0 [-10, 7] ms, RMSE = 5 ms; toe-off bias = 0 [-10, 10] ms, RMSE = 6 ms; and contact time bias = 0 [-15, 15] ms, RMSE = 8 ms) and proved robust to different running speeds, foot-strike angles and inclines. We have made FootNets source code publicly available for step event detection in treadmill running when force data are not available.

bioinformatics↗

bioRxiv2021

Site-specific phosphorylation of PSD-95 dynamically regulates the post-synaptic density as observed by phase separation

Postsynaptic density protein 95 is a key scaffolding protein in the postsynaptic density of excitatory glutamatergic neurons, organizing signaling complexes primarily via its three PSD-95/Discs-large/Zona occludens domains. PSD-95 is regulated by phosphorylation, but technical challenges have limited studies of the molecular details. Here, we genetically introduced site-specific phosphorylations in single, tandem and full-length PSD-95 and generated a total of 11 phosphorylated protein variants. We examined how these phosphorylations affected binding to known interaction partners and the impact on phase separation of PSD-95 complexes, and identified two new phosphorylation sites with opposing effects. Phosphorylation of Ser78 inhibited phase separation with the glutamate receptor subunit GluN2B and the auxiliary protein stargazin, whereas phosphorylation of Ser116 induced phase separation with stargazin only. Thus, by genetically introducing phosphoserine site-specifically and exploring the impact on phase separation, we have provided new insights into the regulation of PSD-95 by phosphorylation and the dynamics of the PSD. Graphical Abstract: Phosphorylation of PSD-95. O_LIIllustration of the interaction between the PDZ domains of PSD-95 and the NMDA receptor (NMDAR) (PDB: 4PE5) at the plasma membrane. PSD-95 interacts with the AMPA receptor (AMPAR) (PDB: 3KG2) through Stargazin (PDB: 5KBU). Using the software Ranch, a model of FL PSD-95 was generated using known structural domains of PSD-95 connected via a fully-flexible linker (PDZ1-2, PDB: 3GSL; PDZ3, PDB: 5JXB; SH3-GK, PDB: 1KJW). C_LIO_LIIllustration of the effect of phosphorylation of PSD-95 on the formation of condensates at the PSD. PSD-95 can phase separate with receptors and intracellular proteins, and phosphorylation is can affect this interaction and lead to alterations, both negative and positive, in the formation of condensates. C_LI

biochemistry↗

bioRxiv2021

RHAMMB-mediated bifunctional nanotherapy targeting Bcl-xL and mitochondria for pancreatic neuroendocrine tumor treatment

The incidence of pancreatic neuroendocrine tumor (PNET) has continued to rise. Due to their indolent feature, PNET patients often present with incurable, metastatic diseases. Novel therapies are urgently needed. We have previously shown that Receptor for Hyaluronic Acid-Mediated Motility isoform B (RHAMMB) and Bcl-xL are upregulated in PNETs and both of them promote PNET metastasis. Because RHAMM protein is undetectable in most adult tissues, we hypothesized that RHAMMB could be a gateway for nanomedicine delivery into PNETs. To test this, we developed RHAMMB-targeting nanoparticle. Inside this nanoparticle, we assembled siRNA against Bcl-xL (siBcl-xL) and mitochondria-fusing peptide KLA. We demonstratsed that RHAMMB-positive PNETs picked up the RHAMMB-targeting nanoparticles. siBcl-xL or KLA alone only killed 30% of PNET cells. In contrast, a synergistic killing effect was achieved with the co-delivery of siBcl-xL and KLA peptide in vitro. Unexpectedly, siBcl-xL induced cell death before reducing Bcl-xL protein levels. The systemically-injected RHAMMB-targeting nanoparticles carrying siBcl-xL and KLA peptide significantly reduced tumor burden in mice bearing RHAMMB-positive PNETs. Together, these findings indicate that the RHAMMB-targeting nanotherapy serves as a promising drug delivery system for PNET and possibly other malignancies upregulating RHAMMB. The combination of siBcl-xL and KLA peptide can be a therapy for PNET treatment.

cancer biology↗

bioRxiv2021

Identification of mutations associated with Macozinone-resistant in Mycobacterium Tuberculosis

Macozinone is identified as a drug candidate and is currently under clinical development for the treatment of tuberculosis, but the mutations conferring resistance to Macozinone remain inadequately characterized. Herein, we investigated the Macozinone -resistance -associated mutations through selecting resistant isolates in vitro. Macozinone-resistant isolates were obtained through induction in vitro. The level of Macozinone -resistant strains was confirmed by MABA test. PCR sequencing analysis was carried out on dprE1 gene. Whole Genome Sequencing was performed to identify mutations associated with Macozinone -resistance. The totals of isolates obtained at Macozinone concentrations of 6.4ng/ml, 25.6ng/ml, 50ng/ml and 100ng/ml were 49, 20, 20 and 4 respectively. Among the 49 strains obtained by 6.4ng/ml Macozinone only one strain had C387S mutation in dprE1. C387S is only occurred in high-level resistant isolates (MIC > 500ng/ml). Meanwhile high-level resistance to Macozinone can occur in strains induced at 6.4ng/ml and the frequency of occurrence is low (1/49, 2.04%). The MIC90 of other strains except the strains carrying C387S mutation is at the same level (11.5ng/ml > MIC90 > 2ng/ml). The G61A or G248A mutations in dprE1 was discovered for the first time. Other gene mutations (rv0678, rrs, mbtF, rv2956, et al) were found in low-level resistant strains. ConclusionsHigh-level resistant isolates can be produced at low concentration of Macozinone. C387S mutation in dprE1 is directly related to high-level resistance. There may be new mechanisms involved in Macozinone-resistance independent of dprE1 mutations.

molecular biology↗

bioRxiv2021

Apoptotic Extracellular Vesicles (ApoEVs) Safeguard Liver Homeostasis and Regeneration via Assembling an ApoEV-Golgi Organelle

Apoptosis is an integral physiological cell death process that occurs frequently and generates a huge number of apoptotic extracellular vesicles (apoEVs). However, whether apoEVs are necessary for maintaining organ homeostasis remains unclear. Here, we show that circulatory apoEVs engraft in liver and undergo specialized internalization by hepatocytes (HCs) based on surface signature of galactose and N-acetylgalactosamine. Furthermore, apoEVs rescue liver injury in apoptotic-deficient Fas mutant and Caspase-3 knockout mice, which is exerted by restoring the featured hepatic ploidy homeostasis. Surprisingly, apoEVs form a chimeric organelle complex with recipient Golgi apparatus via SNARE-mediated membrane interaction, which consequently facilitates microtubule organization and HC cytokinesis. Notably, through Golgi recovery and ploidy transition, apoEVs contribute to liver regeneration and protect against acute hepatic failure. Collectively, these results identify a previously unrecognized role for apoEVs and the specific mechanisms by which they safeguard liver homeostasis, and suggest the potential of apoEV-based therapy for liver disorders.

cell biology↗

bioRxiv2021

DeepMotifSyn: a deep learning approach to synthesize heterodimeric DNA motifs

MotivationThe cooperativity of transcription factors (TFs) is a widespread phenomenon in the gene regulation system. However, the interaction patterns between TF binding motifs remain elusive. The recent high-throughput assays, CAP-SELEX, have identified over 600 composite DNA sites (i.e. heterodimeric motifs) bound by cooperative TF pairs. However, there are over 25,000 inferentially effective heterodimeric TFs in human cell. It is not practically feasible to validate all heterodimeric motifs due to cost and labour. Therefore, it is highly demanding to develop a fast and accurate computational tool for heterodimeric motif synthesis. ResultsWe introduce DeepMotifSyn, a deep-learning-based tool for synthesizing heterodimeric motifs from monomeric motif pairs. Specifically, DeepMotifSyn is composed of heterodimeric motif generator and evaluator. The generator is a U-Net-based neural network that can synthesize heterodimeric motifs from aligned motif pairs. The evaluator is a machine-learning-based model that can score the generated heterodimeric motif candidates based on the motif sequence features. Systematic evaluations on CAP-SELEX data illustrates that DeepMotif-Syn significantly outperforms the current state-of-the-art predictors. In addition, DeepMotifSyn can synthesize multiple heterodimeric motifs with different orientation and spacing settings. Such a feature can address the shortcomings of previous models. We believe Deep-MotifSyn is a more practical and reliable model than current predictors on heterodimeric motif synthesis. Availability and implementationThe software is freely available at https://github.com/JasonLinjc/deepMotifSyn.

bioinformatics↗

bioRxiv2021

Chemoproteomics Enabled Discovery of Selective Probes for NuA4 Factor BRD8

Bromodomain-containing proteins frequently reside in multisubunit chromatin complexes with tissue or cell state-specific compositions. Recent studies have revealed tumor-specific dependencies on the BAF complex bromodomain subunit BRD9 that are a result of recurrent mutations afflicting the structure and composition of associated complex members. To enable the study of ligand engaged complex assemblies, we established a chemoproteomics approach using a functionalized derivative of the BRD9 ligand BI-9564 as an affinity matrix. Unexpectedly, in addition to known interactions with BRD9 and associated BAF complex proteins, we identify a previously unreported interaction with members of the NuA4 complex through the bromodomain-containing subunit BRD8. We apply this finding, alongside homology model guided design, to develop chemical biology approaches for the study of BRD8 inhibition, and to arrive at first-in-class selective and cellularly active probes for BRD8. These tools will empower further pharmacological studies of BRD9 and BRD8 within respective BAF and NuA4 complexes.

biochemistry↗

bioRxiv2021

Time-restricted feeding near dawn entrains long-term behavioral changes through the suprachiasmatic nucleus

The suprachiasmatic nucleus (SCN) is a master circadian pacemaker known to integrate light intensity and seasonal information with peripheral tissues to coordinate daily rhythms of physiology and behavior. However, the contribution of food information to the regulation of the SCN network remains controversial. Here, we identified the effect induced by time-restricted feeding (TRF) at dawn, but not at another time widow, inducing a robust and long-term shift in locomotor behavior and increased wakefulness. Comparing the oscillations of intracellular Ca2+ signals in the SCN GABAergic neurons of freely moving mice, before and after TRF, revealed significant activation of these neurons in dawn-TRF mice. Moreover, RNA-seq profiling in the dawn TRF-induced behavioral changes identified altered expressed genes involved in regulating extracellular exosome, ion transporters, and ECM-receptor interaction, but not core clock genes. Furthermore, injection in the SCN of insulin-like growth factor (IGF2) inhibitor Chromeceptin, targeting the most upregulated gene in extracellular exosome, abolished the after effect induced by ZT0-4 TRF. Finally, GABAergic-neuron-specific disruption of the potassium-chloride cotransporter Kcc2 intensified the dawn TRF-induced after effect, indicating that Kcc2 encodes food intake derived signals that control SCN clock entrainment. Thus, our study functionally links SCN GABAergic neuron activity and central clock entrainment regulation to both hunger- and food-response-related behaviors in mice.

physiology↗

bioRxiv2021

Conserved cell-lineage controlled epigenetic regulation in human and mouse glioblastoma stem cells determines functionally distinct subgroups

There is ample support for developmental regulation of glioblastoma stem cells (GSCs). To examine how cell lineage controls GSC function we have performed a cross-species epigenome analysis of mouse and human GSC cultures. We have analyzed and compared the chromatin-accessibility landscape of nine mouse GSC cultures of defined cell of origin and 60 patient-derived GSC cultures by assay for transposase-accessible chromatin using sequencing (ATAC-seq). This uncovered a variability of both mouse and human GSC cultures that was different from transcriptome analysis and better at predicting functional subgroups. In both species the chromatin accessibility-guided clusters were predominantly determined by distal regulatory element (DRE) regions, displayed contrasting sets of transcription factor binding motifs, and exhibited different functional and drug-response properties. Cross-species analysis of DRE regions in accessible chromatin revealed conserved epigenetic regulation of mouse and human GSCs. Human ATAC-seq data produced three distinct clusters with significant overlap to our previous mouse cell of origin- based stratification, where two of the clusters displayed significantly different patient survival. We conclude that epigenetic regulation of GSCs primarily is dictated by developmental origin which controls key GSC properties and affects therapeutic response.

neuroscience↗

bioRxiv2021

High levels of truncated RHAMM cooperate with dysfunctional p53 to accelerate theprogression of pancreatic cancer

Pancreatic cancer has the lowest survival rate in all types of cancer. Pancreatic cancer patients are often diagnosed at advanced stages. A better therapeutic development for this devastating disease is urgently needed. Receptor for hyaluronan-mediated motility (RHAMM), not expressed in adult pancreas, has been suggested as a prognostic factor and a potential therapeutic target for pancreatic ductal adenocarcinoma (PDAC) and pancreatic neuroendocrine tumor (PNET). In this study, we initially sought to determine whether genetic deletion of RHAMM would slow down pancreatic cancer progression using Rhamm-/- mice. However, we found that Rhamm-/- mice expressed a truncated HMMR{Delta}exon8-16 protein at higher abundance levels than wild-type RHAMM. While HMMR{Delta}exon8-16 did not enable malignant progression of pancreatic intraepithelial neoplasia in p48-Cre; LSL-KRASG12D mice, it accelerated the formation of invasive PDAC and shortened the survival of p48-Cre; LSL-KRASG12D mice with heterozygous p53 knockout. KrasG12D PDAC mice with homozygous p53 knockout mice died around 10 weeks, and the effect of HMMR{Delta}exon8-16 was not apparent in these mice with short-life span. In addition, HMMR{Delta}exon8-16 shortened the survival of PNET-bearing RIP-Tag mice, which had inactivated p53. In our analysis of TCGA dataset, pancreatic cancer patients with mutant TP53 or loss of one copy of TP53 had higher RHAMM expression, which, combined, predicted worse outcomes. Taken together, by collaborating with dysfunctional p53, high levels of HMMR{Delta}exon8- 16 that lacks the centrosome targeting domain and degrons for interaction with the Anaphase-Promoting Complex (APC) accelerated pancreatic cancer progression.

cancer biology↗

bioRxiv2021

A Protein A based Staphylococcus aureus vaccine with improved safety

Exposure to Staphylococcus aureus does not lead to immunity as evidenced by the persistent colonization of one third of the human population. S. aureus immune escape is mediated by factors that preempt complement activation, destroy phagocytes, and modify B and T cell responses. One such factor, Staphylococcal protein A (SpA) encompasses five Immunoglobulin binding domains (IgBDs) that associate with the Fc{gamma} domain to block phagocytosis. IgBDs also associate with the Fab domain of VH3-idiotypic IgM which activates B cells with the resulting secretion of antibodies that cannot bind determinants of S. aureus. SpA crosslinking of VH3-idiotypic IgG and IgE receptors of mast cells and basophils promotes histamine release and anaphylaxis. Previous work demonstrated the safety, immunogenicity, and protective efficacy of SpAKKAA, a variant partially defective for VH3-idiotypic Ig cross-linking, in murine models of S. aureus. Compared to mice (10%), humans produce significantly more VH3-idiotypic B cells (50%), prompting a search for safer SpA variants that may be suitably developed as clinical-grade vaccines for efficacy testing in humans. Here, we report the identification of such variants.

microbiology↗

bioRxiv2021

A glimpse into the diverse cellular immunity against SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific cellular immune response may prove to be essential for long-term immune protection against the novel coronavirus disease 2019 (COVID-19). To assess COVID-19-specific immunity in the population, we synthesized selected peptide pools of SARS-CoV-2 structural and functional proteins, including Spike (S), Membrane (M), Envelope (E), Nucleocapsid (N) and Protease (P) as target antigens. Survey of the T cell precursur frequencies in healthy individuals specific to these viral antigens demonstrated a diverse cellular immunity, including high, medium, low and no responders. This was further confirmed by in vitro induction of anti-SARS-CoV-2 T cell immune responses using dendritic cell (DC)/T cell coculture, which supported the corresponding T cell precursor frequencies in each of the individuals tested. In general, the combination of all five viral antigen pools induced the strongest cellular immune response, yet individual donors responded differently to different viral antigens. Importantly, in vitro restimulation of the T cells with the DC-peptides induced increased anti-viral immune responses in all individuals even in the no responders, suggesting that repeated antigen stimulation could elicit a broad protection in immune naive population. Our analysis recapitulates the critical role of cellular immunity in fighting COVID-19 and the importance of analyzing anti-SARS-CoV-2 T cell response in addition to antibody response in the population. ImportanceFacing the rapid evolving SARS-CoV-2 variants in the world, current emphasis on antibody-producing vaccines needs a quick revisit. The virus-specific cellular immunity may prove to be essential for long-term protection against COVID-19. This study designed a series of antigenic peptides encompassing the conserved and/or essential domains of Spike (S), Membrane (M), envelope (E), Nucleocapsid (N) and Protease (P) as targets to assess Covid-19-specific immunity in the population. The results demonstrated a diverse cellular immunity, including high, medium, low and no responders. This was verified by in vitro generation of anti-SARS-CoV-2 T-cells from these subjects. The study suggested that individuals responded differently to the different viral antigens, and importantly, repeated stimulation could produce virus specific T cells in all individuals, including the no responders. This study illustrates the needs for assessing anti-viral cellular immunity in addition to antibody response in the general population.

microbiology↗

bioRxiv2021

MethReg: estimating the regulatory potential of DNA methylation in gene transcription

Epigenome-wide association studies (EWAS) often detect a large number of differentially methylated sites or regions, many are located in distal regulatory regions. To further prioritize these significant sites, there is a critical need to better understand the functional impact of CpG methylation. Recent studies demonstrated CpG methylation-dependent transcriptional regulation is a widespread phenomenon. Here we present MethReg, an R/Bioconductor package that analyzes matched DNA-methylation and gene-expression data, along with external transcription factor (TF) binding information, to evaluate, prioritize, and annotate CpG sites with high regulatory potential. By simultaneous modeling three key elements that contribute to gene transcription (CpG methylation, target gene expression and TF activity), MethReg identifies TF-target gene associations that are present only in a subset of samples with high (or low) methylation levels at the CpG that influences TF activities, which can be missed in analyses that use all samples. Using real colorectal cancer and Alzheimers disease datasets, we show MethReg significantly enhances our understanding of the regulatory roles of DNA methylation in complex diseases.

bioinformatics↗

bioRxiv2021

PhylEx: Accurate reconstruction of clonal structure via integrated analysis of bulk DNA-seq and single cell RNA-seq data

We propose PhylEx: a clonal-tree reconstruction method that integrates bulk genomics and single-cell transcriptomics data. In addition to the clonal-tree, PhylEx also assigns single-cells to clones, which effectively produce clonal expression profiles, and generates clonal genotypes. By analyzing scRNA-seq integrated with bulk DNA-seq, PhylEx can take advantage of co-occurrences of the mutations found in the cells. In the probabilistic model underlying PhylEx, the raw read counts from scRNA-seq follow a mixture of Beta-Binomial distributions, which accounts for the sparse nature of single-cell gene expression data; the mixture lessens the penalty caused by mutations not observed due to mono-allelic expression. We rigorously evaluated PhylEx on simulated datasets as well as a biological dataset consisting of a previously well-characterized high-grade serous ovarian cancer (HGSOC) cell line. PhylEx outperformed the state-of-the-art methods by a wide margin both when comparing capacity for clonal-tree reconstruction and capacity for correctly clustering mutations. By analyzing HGSOC and HER2+ breast cancer data, we also show that PhylEx clears the way for phylo-phenotypic analysis of cancer, i.e., that the clonal expression profiles, induced by the cell-to-clone assignments, can be exploited in a manner beyond what is possible with only expression-based clustering.

bioinformatics↗

bioRxiv2021

MultiMAP: Dimensionality Reduction and Integration of Multimodal Data

Multimodal data is rapidly growing in many fields of science and engineering, including single-cell biology. We introduce MultiMAP, an approach for dimensionality reduction and integration of multiple datasets. MultiMAP recovers a single manifold on which all of the data resides and then projects the data into a single low-dimensional space so as to preserve the structure of the manifold. It is based on a framework of Riemannian geometry and algebraic topology, and generalizes the popular UMAP algorithm1 to the multimodal setting. MultiMAP can be used for visualization of multimodal data, and as an integration approach that enables joint analyses. MultiMAP has several advantages over existing integration strategies for single-cell data, including that MultiMAP can integrate any number of datasets, leverages features that are not present in all datasets (i.e. datasets can be of different dimensionalities), is not restricted to a linear mapping, can control the influence of each dataset on the embedding, and is extremely scalable to large datasets. We apply MultiMAP to the integration of a variety of single-cell transcriptomics, chromatin accessibility, methylation, and spatial data, and show that it outperforms current approaches in preservation of high-dimensional structure, alignment of datasets, visual separation of clusters, transfer learning, and runtime. On a newly generated single-cell Assay for Transposase-Accessible Chromatin using sequencing (scATAC-seq) and single-cell RNA-seq (scRNA-seq) dataset of the human thymus, we use MultiMAP to integrate cells along a temporal trajectory. This enables the quantitative comparison of transcription factor expression and binding site accessibility over the course of T cell differentiation, revealing patterns of transcription factor kinetics.

bioinformatics↗

bioRxiv2021

Biomolecular recognition of the glycan neoantigen CA19-9 by distinct antibodies

Glycans decorate cell surface, secreted glycoproteins and glycolipids. Altered glycans are often found in cancers. Despite their high diagnostic and therapeutic potentials, glycans are polar and flexible molecules that are quite challenging for the development and design of high-affinity binding antibodies. To understand the mechanisms by which glycan neoantigens are specifically recognized by antibodies, we analyze the biomolecular recognition of a single tumor-associated carbohydrate antigen CA19-9 by two distinct antibodies using X-ray crystallography. Despite the plasticity of glycans and the very different antigen-binding surfaces presented by the antibodies, both structures reveal an essentially identical extended CA19-9 conformer, suggesting that this conformers stability selects the antibodies. Starting from the bound structure of one of the antibodies, we use the AbLIFT computational method to design a variant with seven core mutations that exhibited tenfold improved affinity for CA19-9. The results reveal strategies used by antibodies to specifically recognize glycan antigens and show how automated antibody-optimization methods may be used to enhance the clinical potential of existing antibodies.

molecular biology↗

bioRxiv2021

DARPP-32 promotes ERBB3-mediated resistance to molecular targeted therapy in EGFR-mutated lung adenocarcinoma

While molecular targeted therapies have improved prognoses of advanced stage lung adenocarcinoma expressing oncogenic driver mutations, acquired therapeutic resistance continues to be a major problem. Epidermal growth factor receptor (EGFR) activating mutations are among the most common targetable genetic alterations in lung adenocarcinoma, and EGFR tyrosine kinase inhibitors (TKIs) are recommended first-line therapy for EGFR mutation positive cancer patients. Unfortunately, most patients develop resistance to EGFR TKIs and rapid disease progression occurs. A better mechanistic understanding of therapy refractory cancer progression is necessary to develop new therapeutic approaches to predict and prevent acquired resistance to EGFR TKIs. Here, we identify a new mechanism of ERBB3-mediated resistance to EGFR TKIs in human lung adenocarcinoma. Specifically, we show that dopamine and cyclic AMP-regulated phosphoprotein, Mr 32000 (DARPP-32) physically recruits ERBB3 to EGFR to mediate a switch from EGFR homodimers to EGFR:ERBB3 heterodimers to bypass EGFR TKI-mediated inhibition to potentiate ERBB3-dependent activation of oncogenic AKT and ERK signaling that drives therapy refractory tumor cell survival. In a cohort of paired tumor specimens derived from 30 lung adenocarcinoma patients before and after the development of EGFR TKI refractory disease progression, we reveal that DARPP-32 as well as kinase-activated EGFR and ERBB3 proteins are overexpressed upon acquired EGFR TKI resistance. In vivo studies suggest that ablation of DARPP-32 protein activity sensitizes gefitinib-resistant lung tumor xenografts to EGFR TKI treatment, while DARPP-32 overexpression increases gefitinib-refractory lung cancer progression in gefitinib-sensitive lung tumors orthotopically xenografted into mice. Taken together, our findings introduce a DARPP-32-mediated, ERBB3-dependent mechanism used by lung tumor cells to evade EGFR TKI-induced cell death, potentially paving the way for the development of new therapies to prevent or overcome therapy-refractory lung adenocarcinoma progression.

cancer biology↗