Panoramic tumor microenvironment in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is notorious for its resistance to various treatment modalities. The genetic heterogeneity of PDAC, coupled with the presence of a desmoplastic stroma within the tumor microenvironment (TME), contributes to an unfavorable prognosis. The mechanisms and consequences of interactions among different cell types, along with spatial variations influencing cellular function, potentially play a role in the pathogenesis of PDAC. Understanding the diverse compositions of the TME and elucidating the functions of microscopic neighborhoods may contribute to understanding the immune microenvironment status in pancreatic cancer. As we delve into the spatial biology of the microscopic neighborhoods within the TME, aiding in deciphering the factors that orchestrate this intricate ecosystem. This overview delineates the fundamental constituents and the structural arrangement of the PDAC microenvironment, highlighting their impact on cancer cell biology.

Quantitative Proteomics Reveal the Role of Matrine in Regulating Lipid Metabolism.

Hyperlipidemia (HLP) is a prevalent systemic metabolic disorder characterized by disrupted lipid metabolism. Statin drugs have long been the primary choice for managing lipid levels, but intolerance issues have prompted the search for alternative treatments. Matrine, a compound derived from the traditional Chinese medicine Kushen, exhibits anti-inflammatory and lipid-lowering properties. Nevertheless, the mechanism by which matrine modulates lipid metabolism remains poorly understood. Here, we investigated the molecular mechanisms underlying matrine's regulation of lipid metabolism. Employing quantitative proteomics, we discovered that matrine increases the expression of LDL receptor (LDLR) in HepG2 and A549 cells, with subsequent experiments validating its role in enhancing LDL uptake. Notably, in hyperlipidemic hamsters, matrine effectively lowered lipid levels without affecting body weight, which highlights LDLR as a critical target for matrine's impact on HLP. Moreover, matrine's potential inhibitory effects on tumor cell LDL uptake hint at broader applications in cancer research. Additionally, thermal proteome profiling analysis identified lipid metabolism-related proteins that may interact with matrine. Together, our study reveals matrine's capacity to upregulate LDLR expression and highlights its potential in treating HLP. These findings offer insights into matrine's mechanism of action and open new avenues for drug research and lipid metabolism regulation.

Predictive Biomarkers for Immunotherapy in Gastric Cancer: Current Status and Emerging Prospects.

Gastric cancer presents substantial management challenges, and the advent of immunotherapy has ignited renewed hope among patients. Nevertheless, a significant proportion of patients do not respond to immunotherapy, and adverse events associated with immunotherapy also occur on occasion, underscoring the imperative to identify suitable candidates for treatment. Several biomarkers, including programmed death ligand-1 expression, tumor mutation burden, mismatch repair status, Epstein-Barr Virus infection, circulating tumor DNA, and tumor-infiltrating lymphocytes, have demonstrated potential in predicting the effectiveness of immunotherapy in gastric cancer. However, the quest for the optimal predictive biomarker for gastric cancer immunotherapy remains challenging, as each biomarker carries its own limitations. Recently, multi-omics technologies have emerged as promising platforms for discovering novel biomarkers that may help in selecting gastric cancer patients likely to respond to immunotherapy. The identification of reliable predictive biomarkers for immunotherapy in gastric cancer holds the promise of enhancing patient selection and improving treatment outcomes. In this review, we aim to provide an overview of clinically established biomarkers of immunotherapy in gastric cancer. Additionally, we introduce newly reported biomarkers based on multi-omics studies in the context of gastric cancer immunotherapy, thereby contributing to the ongoing efforts to refine patient stratification and treatment strategies.

Zebrafish functional xenograft vasculature platform identifies PF-502 as a durable vasculature normalization drug.

Tumor vasculature often exhibits disorder and inefficiency. Vascular normalization offers potential for alleviating hypoxia and optimizing drug delivery in tumors. However, identifying effective agents is hindered by a lack of robust screening. We aimed to establish a comprehensive method using the zebrafish functional xenograft vasculature platform (zFXVP) to visualize and quantify tumor vasculature changes. Employing zFXVP, we systematically screened compounds, identifying PF-502 as a robust vascular normalization agent. Mechanistic studies showed PF-502 induces endothelial cell-cycle arrest, streamlines vasculature, and activates Notch1 signaling, enhancing stability and hemodynamics. In murine models, PF-502 exhibited pronounced vascular normalization and improved drug delivery at a sub-maximum tolerated dose. These findings highlight zFXVP's utility and suggest PF-502 as a promising adjunctive for vascular normalization in clinical settings.

Computational holographic ghost diffraction.

Since the paradigm shift in 2009 from pseudo-thermal ghost imaging (GI) to computational GI using a spatial light modulator, computational GI has enabled image formation via a single-pixel detector and thus has a cost-effective advantage in some unconventional wave bands. In this Letter, we propose an analogical paradigm known as computational holographic ghost diffraction (CH-GD) to shift ghost diffraction (GD) from classical to computational by using self-interferometer-assisted measurement of field correlation functions rather than intensity correlation functions. More than simply "seeing" the diffraction pattern of an unknown complex volume object with single-point detectors, CH-GD can retrieve the diffracted light field's complex amplitude and can thus digitally refocus to any depth in the optical link. Moreover, CH-GD has the potential to obtain the multimodal information including intensity, phase, depth, polarization, and/or color in a more compact and lensless manner.

Dynamic Distribution of Skin Microorganisms in Donkeys at Different Ages and Various Sites of the Body.

Considerable evidence suggests that the skin microbiota is not only important and complex in humans and other mammals but also critical for maintaining health and skin homeostasis. To date, studies on the skin microorganisms of donkeys are surprisingly rare. To investigate the dynamic changes in commensal microbial communities on the skins of healthy donkeys throughout the growing period, skin and soil samples were collected from 30 healthy Dezhou donkeys (ranging from 1, 6, 12, 24 to 48 months of age) and their corresponding breeding sheds on the farm. All samples were analysed for high-throughput sequencing of the 16S rRNA and ITS to characterize the skin microbiota of healthy donkeys and compare the differences in skin microbiota among donkeys of different ages. There were notable differences in the proportions of various genera (including bacteria and fungi) between dorsal and abdominal skin with increasing age. The comparison of the skin microbial communities among these groups revealed that Staphylococcus was mainly enriched in the early growing stage (1 and 6 months), while the relative abundance of Streptococcus was higher in both the 1- and 48-month-old age groups. Moreover, some bacteria and commensal fungi, such as Staphylococcus and Trichosporon, were found to be positively correlated between the skin and the environment. This is the first study to investigate the dynamic changes in skin microbiota diversity and composition in donkeys of different ages and at different sites of the body. Furthermore, this study provides insights into the dynamic alterations in skin microbes during a donkey's growth and characterizes the profiles of bacterial and fungal communities across a donkey's body regions (dorsal and abdomen).

Predictive biomarkers of colon cancer immunotherapy: Present and future.

Immunotherapy has revolutionized colon cancer treatment. Immune checkpoint inhibitors (ICIs) have shown clinical benefits for colon cancer patients, especially those with high microsatellite instability (MSI-H). In 2020, the US Food and Drug Administration (FDA)-approved ICI pembrolizumab as the first-line treatment for metastatic MSI-H colon cancer patients. Additionally, neoadjuvant immunotherapy has presented efficacy in treating early-stage colon cancer patients. Although MSI has been thought of as an effective predictive biomarker for colon cancer immunotherapy, only a small proportion of colon cancer patients were MSI-H, and certain colon cancer patients with MSI-H presented intrinsic or acquired resistance to immunotherapy. Thus, further search for predictive biomarkers to stratify patients is meaningful in colon cancer immunotherapy. Except for MSI, other biomarkers, such as PD-L1 expression level, tumor mutation burden (TMB), tumor-infiltrating lymphocytes (TILs), certain gut microbiota, ctDNA, and circulating immune cells were also proposed to be correlated with patient survival and ICI efficacy in some colon cancer clinical studies. Moreover, developing new diagnostic techniques helps identify accurate predictive biomarkers for colon cancer immunotherapy. In this review, we outline the reported predictive biomarkers in colon cancer immunotherapy and further discuss the prospects of technological changes for biomarker development in colon cancer immunotherapy.

Nanoparticle-Based Therapeutic Strategies for Enhanced Pancreatic Ductal Adenocarcinoma Immunotherapy.

Immunotherapy has dramatically changed prognosis for patients with malignant tumors. However, as a non-immunogenic tumor, pancreatic ductal adenocarcinoma (PDAC) has a low response to immunotherapy. Factors that contribute to the inefficiency of PDAC immunotherapy include the tumor microenvironment (TME) and its dense stroma, which acts as a barrier for drug delivery and immune cell infiltration. Recent studies have shown that nanoparticle-based therapeutic strategies have more promising applications in improving drug delivery and reversing the immunosuppressive TME for PDAC. Therefore, nanomaterial-based therapeutic approaches are expected to enhance the effectiveness of immunotherapy and improve prognosis of patients with PDAC. Here, we outline the status and dilemma of PDAC immunotherapy, and summarize the latest advances in nanoparticle-based treatment strategies to enhance the efficacy of PDAC immunotherapy.

Quantitative Proteomics Explore the Potential Targets and Action Mechanisms of Hydroxychloroquine.

Hydroxychloroquine (HCQ) is an autophagy inhibitor that has been used for the treatment of many diseases, such as malaria, rheumatoid arthritis, systemic lupus erythematosus, and cancer. Despite the therapeutic advances in these diseases, the underlying mechanisms have not been well determined and hinder the rational use of this drug in the future. Here, we explored the possible mechanisms and identified the potential binding targets of HCQ by performing quantitative proteomics and thermal proteome profiling on MIA PaCa-2 cells. This study revealed that HCQ may exert its functions by targeting some autophagy-related proteins such as ribosyldihydronicotinamide dehydrogenase (NQO2) and transport protein Sec23A (SEC23A), or regulating the expression of galectin-8 (LGALS8), mitogen-activated protein kinase 8 (MAPK8), and so on. Furthermore, HCQ may prevent the progression of pancreatic cancer by regulating the expression of nesprin-2 (SYNE2), protein-S-isoprenylcysteine O-methyltransferase (ICMT), and cotranscriptional regulator FAM172A (FAM172A). Together, these findings not only identified potential binding targets for HCQ but also revealed the non-canonical mechanisms of HCQ that may contribute to pancreatic cancer treatment.

Identification and evaluation of a lipid-lowering small compound in preclinical models and in a Phase I trial.

Developing non-statin-based small compounds to battle the global epidemic of hyperlipidemia remains challenging. Here, we report the discovery of DC371739, an indole-containing tetrahydroisoquinoline compound with promising lipid-lowering effects, both in vitro and in vivo, and with good tolerability in a Phase I clinical trial (NCT04927221). DC371739 significantly reduced the plasma levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides simultaneously in several animal models and showed preliminary positive results in the Phase I trial. Mechanistically, DC371739 acts in a distinct manner from other known lipid-lowering reagents. We show that it physically binds HNF-1α, impeding the transcription of both PCSK9 and ANGPTL3, two genes that are known to contribute to hypercholesterolemia and dyslipidemia. Moreover, the distinct mechanism of action of DC371739 allows its combination with atorvastatin treatment to additively improve dyslipidemia, while providing a potential alternative therapeutic strategy for individuals with statin intolerance.

Quantitative Proteomics Analysis Expands the Roles of Lysine ß-Hydroxybutyrylation Pathway in Response to Environmental ß-Hydroxybutyrate.

Lysine ß-hydroxybutyrylation (Kbhb) is a newly identified protein posttranslational modification (PTM) derived from ß-hydroxybutyrate (BHB), a product of ketone body metabolism in liver. BHB could serve as an energy source and play a role in the suppression of oxidative stress. The plasma concentration of BHB could increase up to 20 mM during starvation and in pathological conditions. Despite the progress, how the cells derived from extrahepatic tissues respond to elevated environmental BHB remains largely unknown. Given that BHB can significantly drive Kbhb, we characterized the BHB-induced lysine ß-hydroxybutyrylome and acetylome by quantitative proteomics. A total of 840 unique Kbhb sites on 429 proteins were identified, with 42 sites on 39 proteins increased by more than 50% in response to BHB. The results showed that the upregulated Kbhb induced by BHB was involved in aminoacyl-tRNA biosynthesis, 2-oxocarboxylic acid metabolism, citrate cycle, glycolysis/gluconeogenesis, and pyruvate metabolism pathways. Moreover, some BHB-induced Kbhb substrates were significantly involved in diseases such as cancer. Taken together, we investigate the dynamics of lysine ß-hydroxybutyrylome and acetylome induced by environmental BHB, which reveals the roles of Kbhb in regulating various biological processes and expands the biological functions of BHB.

A pH-Responsive Zwitterionic Polyurethane Prodrug as Drug Delivery System for Enhanced Cancer Therapy.

Numerous nanocarriers with excellent biocompatibilities have been used to improve cancer therapy. However, nonspecific protein adsorption of nanocarriers may block the modified nanoparticles in tumor cells, which would lead to inefficient cellular internalization. To address this issue, pH-responsive polyurethane prodrug micelles with a zwitterionic segment were designed and prepared. The micelle consisted of a zwitterionic segment as the hydrophilic shell and the drug Adriamycin (DOX) as the hydrophobic inner core. As a pH-responsive antitumor drug delivery system, the prodrug micelles showed high stability in a physiological environment and continuously released the drug under acidic conditions. In addition, the pure polyurethane carrier was demonstrated to be virtually non-cytotoxic by cytotoxicity studies, while the prodrug micelles were more efficient in killing tumor cells compared to PEG-PLGA@DOX. Furthermore, the DOX cellular uptake efficiency of prodrug micelles was proved to be obviously higher than the control group by both flow cytometry and fluorescence microscopy. This is mainly due to the modification of a zwitterionic segment with PU. The simple design of zwitterionic prodrug micelles provides a new strategy for designing novel antitumor drug delivery systems with enhanced cellular uptake rates.

[Research progress of circadian rhythm].

Circadian rhythm disorder is a common society issue caused by jet lag,shift work,sleep disruption and changes in food consumption. Light is the major factor affecting the circadian rhythm system. Disruption of the circadian rhythm system can cause damage to the body,leading to some diseases. Maintaining a normal circadian system is of great importance for good health. Ideal therapeutic effect can not only alleviate symptoms of the diseases,but also recovery the disturbed circadian rhythm to normal. The paper summarizes the modeling methods of animal circadian rhythm disorder,diseases of circadian rhythm abnormality,regulation of circadian clock genes and medicine which are related to circadian rhythm to diseases of circadian rhythm disorder.

Immune Check Point Inhibitors and Immune-Related Adverse Events in Small Cell Lung Cancer.

Small cell lung cancer (SCLC) is a malignant solid tumor. In recent years, although immune check point inhibitors (ICIs) have achieved important advances in the treatment of SCLC, immune-related adverse events (irAEs) have occurred at the same time during the therapeutic period. Some irAEs lead to dose reduction or treatment rejection. The immune microenvironment of SCLC is complicated, therefore, understanding irAEs associated with ICIs is of great importance and necessity for the clinical management of SCLC. However, the lack of comprehensive understanding of irAEs in patients with SCLC remains remarkable. This review aims to provide an up-to-date overview of ICIs and their associated irAEs in patients with SCLC based on present clinical data.

Comparative evaluation of cardiovascular risks among nine FDA-approved VEGFR-TKIs in patients with solid tumors: a Bayesian network analysis of randomized controlled trials.

PURPOSE: The present meta-analysis study was performed to identify the potential cardiotoxicity risks when using Vascular Endothelial Growth Factor Receptor Tyrosine kinase inhibitors (VEGFR-TKIs) as anticancer drugs in patients with solid tumors. METHODS: Pubmed, Embase, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov databases were searched for the randomized controlled trials. We have included 45 randomized controlled trials (RCTs) associated with nine VEGFR-TKIs Food and Drug Administration (FDA)-approved drugs used to treat patients with solid tumors. To evaluate the trials' risk of bias, Cochrane Risk of Bias Tool was assessed. A direct comparison was assessed by RevMan5.3 software, calculating the odds ratio (OR) and 95% confidence interval (CI). Heterogeneity was tested by the I2 statistic and Chi-square test for P value. Bayesian network meta-analysis was performed using Stata 15.0 and GeMTC 0.14.3 software, calculated OR along with corresponding 95% credible interval (CrI). The model's convergence was evaluated by the potential scale reduced factor (PSRF). Consistency between direct and indirect comparisons was assessed by the "node-splitting" method. RESULTS: In this network meta-analysis, a total of 20,027 patients from 45 randomized controlled trials and associated with nine FDA-approved VEGFR-TKIs (axitinib, cabozantinib, lenvatinib, nintedanib, pazopanib, regorafenib, sorafenib, sunitinib, vandetanib), were enrolled. Findings indicated that lenvatinib had the most significant probability of provoking all grades cardiovascular incident and hypertension, followed by vandetanib, cabozantinib, axitinib, pazopanib, sorafenib, sunitinib, regorafenib and nintedanib. The nine agent's severe cardiovascular and severe hypertension risk was probably similar. The ranking probability of cardiac toxicity shows that vandetanib ranked most likely to have the highest risk for cardiotoxicity among all the VEGFR-TKIs reviewed, followed by pazopanib, axitinib, sorafenib, sunitinib. In contrast, regorafenib and nintedanib did not exhibit an increased risk of cardiac damage. CONCLUSIONS: The association between the nine VEGFR-TKIs with potential cardiotoxicity occurrence was reviewed. Both the regorafenib and nintedanib did not display detectable signs of cardiotoxic damage. In contrast, lenvatinib and vandetanib are ranked to have the most severe cardiotoxicity side impacts. These results may provide information for clinical practice guidelines, implementing strategies in selecting the adequate VEGFR-TKIs, and understanding the cardiovascular toxicity inflicted by the VEGFR-TKIs. PROSPERO IDENTIFIER: CRD 42,020,167,307.

Photo-Responsive Polymersomes as Drug Delivery System for Potential Medical Applications.

Due to a strong retardation effect of o-nitrobenzyl ester on polymerization, it is still a great challenge to prepare amphiphilic block copolymers for polymersomes with a o-nitrobenzyl ester-based hydrophobic block. Herein, we present one such solution to prepare amphiphilic block copolymers with pure poly (o-nitrobenzyl acrylate) (PNBA) as the hydrophobic block and poly (N,N'-dimethylacrylamide) (PDMA) as the hydrophilic block using bulk reversible addition-fragmentation chain transfer (RAFT) polymerization of o-nitrobenzyl acrylate using a PDMA macro-RAFT agent. The developed amphiphilic block copolymers have a suitable hydrophobic/hydrophilic ratio and can self-assemble into photoresponsive polymersomes for co-loading hydrophobic and hydrophilic cargos into hydrophobic membranes and aqueous compartments of the polymersomes. The polymersomes demonstrate a clear photo-responsive characteristic. Exposure to light irradiation at 365 nm can trigger a photocleavage reaction of o-nitrobenzyl groups, which results in dissociation of the polymersomes with simultaneous co-release of hydrophilic and hydrophobic cargoes on demand. Therefore, these polymersomes have great potential as a smart drug delivery nanocarrier for controllable loading and releasing of hydrophilic and hydrophobic drug molecules. Moreover, taking advantage of the conditional releasing of hydrophilic and hydrophobic drugs, the drug delivery system has potential use in medical applications such as cancer therapy.

Synergies of Antiangiogenic Therapy and Immune Checkpoint Blockade in Renal Cell Carcinoma: From Theoretical Background to Clinical Reality.

The hallmarks of renal cell carcinoma (RCC) are angiogenesis and immunogenic tumor microenvironment. Over the past decades, treatment options for metastatic RCC (mRCC) have been expanding, from the inhibition of vessel formation via antiangiogenic agents (AAs) to the stimulation of immune system by immune checkpoint inhibitors (ICIs). Since 2005, the introduction of antiangiogenic agents targeting vascular endothelial growth factor (VEGF), its receptors (VEGFRs), and mammalian target of rapamycin (mTOR) pathway have experienced moderate success in the therapeutics of mRCC, but patient outcomes remain suboptimal. Recently, the development of ICIs targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and the programmed death-1/programmed death ligand 1 (PD-1/PD-L1) pathways has dramatically changed the treatment landscape of mRCC. Expressly, the combination of ipilimumab and nivolumab has been confirmed to improve clinical outcomes and approved as a standard care for intermediate- or poor-risk mRCC patients. Nevertheless, innate or adaptive drug resistance is observed within both treatment approaches, limiting overall clinical benefit. This phenomenon will underscore the urgent need for new combinational therapy strategies with different mechanisms of action, which can improve efficacy in an extended patient population without severe toxic effects. In 2019, as the results of two critical phase III trials came to light, FDA approved axitinib plus avelumab, or pembrolizumab as first-line standard management for mRCC, which cements the combination of AAs plus ICIs and advances the mRCC treatment field. This review summarizes current evidence on the interplay and synergies between AAs and immunomodulating drugs in mRCC, focusing on the theoretical background and the status of current clinical development.

On the nonlinear temperature dependence of elastic constants and wave velocities for solid media with applications to geologic materials.

Temperature-induced variations of elastic moduli in solid media are generally characterized by a strong nonlinear dependence on temperature associated with complex deformations under thermal treatments. Conventional thermoelasticity with third-order elastic constants for the one-order temperature dependence has been extensively studied for crystals, but encountering problems of divergent and limited velocity variations for rocks as a polycrystal mixture, especially at high temperatures. The extension of the theory beyond high-order elastic constants to solid media is addressed in this article to describe the nonlinear temperature dependence of both elastic constants and wave velocities. The total strain is divided into the background component associated with temperature variations and the infinitesimal component induced by propagating waves. A third-order temperature dependence of velocity variations is formulated by taking into account fourth-order elastic constants. Applications to solid rocks (sandstone, granite, and olivine) demonstrate an accurate description of temperature-induced variations, especially for high temperatures. Unlike crystals, the synthetic averaging elastic constants for a solid rock (as a polycrystal mixture) change less than 10% with temperatures. The thermal sensitivity of P-wave velocities is much more than that of S-wave velocities over the vast majority of temperatures examined.

[Comprehensive analysis of the aberrantly expressed profiles of lncRNAs, miRNAs and the regulation network of the associated ceRNAs in clear cell renal cell carcinoma].

To evaluate the differential expression profiles of the lncRNAs, miRNAs, mRNAs and ceRNAs, and their implication in the prognosis in clear cell renal cell carcinoma (CCRCC), the large sample genomics analysis technologies were used in this study. The RNA and miRNA sequencing data of CCRCC were obtained from The Cancer Genome Atlas (TCGA) database, and R software was used for gene expression analysis and survival analysis. Cytoscape software was used to construct the ceRNA network. The results showed that a total of 1 570 lncRNAs, 54 miRNAs, and 17 mRNAs were differentially expressed in CCRCC, and most of their expression levels were up-regulated (false discovery rate < 0.01 and absolute log fold change > 2). The ceRNA regulatory network showed the interaction between 89 differentially expressed lncRNAs and 9 differentially expressed miRNAs. Further survival analysis revealed that 38 lncRNAs (including COL18A1-AS1, TCL6, LINC00475, UCA1, WT1-AS, HOTTIP, PVT1, etc.) and 2 miRNAs (including miR-21 and miR-155) were correlated with the overall survival time of CCRCC ( P < 0.05). Together, this study provided us several new evidences for the targeted therapy and prognosis assessment of CCRCC.

The MEK inhibitors enhance the efficacy of sorafenib against hepatocellular carcinoma cells through reducing p-ERK rebound.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most common malignant tumours worldwide and has a poor prognosis. Sorafenib, the only targeted therapeutic agent for HCC, is a multiple kinase inhibitor with targets including RAF and VEGFR-2/3 that display a very limited ability to extend the survival of patients with advanced metastatic HCC for approximately three months. MEK inhibitors including trametinib and selumetinib have shown promising efficacy in combination with sorafenib in clinical trials. However, the mechanisms about the combined effect of these drugs remain unclear. METHODS: Two HCC cell lines (Bel7402 and SMMC7721) were used in the experiments. The protein expression of HCC cell lines was quantified via western blotting. Cell viability was examined by cell counting kit-8 and colony formation assays. Drug interactions between sorafenib and trametinib/selumetinib were determined by the combination index (CI) value. RESULTS: In this study, we found that short-term sorafenib treatment could inhibit the downstream RAF effectors phosphorylated (p)-MEK and p-ERK in Bel7402 and SMMC7721 cells, while long-term sorafenib treatment could induce a rebound of p-MEK and p-ERK expression in these two human HCC cell lines. We then tested the effect of sorafenib combined with two different FDA-approved MEK inhibitors, trametinib and selumetinib, in the two cell lines. Western blot analysis showed that trametinib/selumetinib could abolish the ERK activation caused by long-term sorafenib treatment. Cell counting kit-8 and colony formation assays indicated that the use of sorafenib or trametinib/selumetinib alone produced a minor effect on the proliferation of these HCC cell lines, while the combination therapies induced strong growth inhibition. CI assays using CompuSyn software indicated that the combined therapies could produce a synergistic effect in these two cell lines. In addition, mechanistic studies revealed that the combination therapies could synergistically reduce the expression of proliferation-related proteins, including cyclin D1 and c-Myc. CONCLUSIONS: Taken together, our study showed that the rebound of p-ERK induced by long-term sorafenib treatment might limit the benefit of sorafenib monotherapy, and the MEK inhibitors trametinib and selumetinib could enhance the efficacy of sorafenib in HCC cells.