Characterization and therapeutic potential of MRABP9, a novel lytic bacteriophage infecting multidrug-resistant Acinetobacter baumannii clinical strains.

Acinetobacter baumannii is one of the most important pathogens of healthcare-associated infections. The rising prevalence of multidrug-resistant A. baumannii (MRAB) strains and biofilm formation impact the outcome of conventional treatment. Phage-related therapy is a promising strategy to tame troublesome multidrug-resistant bacteria. Here, we isolated and evaluated a highly efficient lytic phage called MRABP9 from hospital sewage. The phage was a novel species within the genus Friunavirus and exhibited lytic activity against 2 other identified MRAB strains. Genomic analysis revealed it was a safe virulent phage and a pectate lyase domain was identified within its tail spike protein. MRABP9 showed potent bactericidal and anti-biofilm activity against MRAB, significantly delaying the time point of bacterial regrowth in vitro. Phage administration could rescue the mice from acute lethal MRAB infection. Considering its features, MRABP9 has the potential as an efficient candidate for prophylactic and therapeutic use against acute infections caused by MRAB strains.

Redox-responsive polymer micelles co-encapsulating immune checkpoint inhibitors and chemotherapeutic agents for glioblastoma therapy.

Immunotherapy with immune checkpoint blockade (ICB) for glioblastoma (GBM) is promising but its clinical efficacy is seriously challenged by the blood-tumor barrier (BTB) and immunosuppressive tumor microenvironment. Here, anti-programmed death-ligand 1 antibodies (aPD-L1) are loaded into a redox-responsive micelle and the ICB efficacy is further amplified by paclitaxel (PTX)-induced immunogenic cell death (ICD) via a co-encapsulation approach for the reinvigoration of local anti-GBM immune responses. Consequently, the micelles cross the BTB and are retained in the reductive tumor microenvironment without altering the bioactivity of aPD-L1. The ICB efficacy is enhanced by the aPD-L1 and PTX combination with suppression of primary and recurrent GBM, accumulation of cytotoxic T lymphocytes, and induction of long-lasting immunological memory in the orthotopic GBM-bearing mice. The co-encapsulation approach facilitating efficient antibody delivery and combining with chemotherapeutic agent-induced ICD demonstrate that the chemo-immunotherapy might reprogram local immunity to empower immunotherapy against GBM.

NLRC5 Deficiency Reduces LPS-Induced Microglial Activation via Inhibition of NF-κB Signaling and Ameliorates Mice's Depressive-like Behavior.

Microglia are believed to be the key immune effectors of the central immune microenvironment, and their dysregulation is associated with neuroinflammation and mood disorders. Nucleotide-binding oligomerization domain-like receptor family caspase recruitment domain-containing five (NLRC5) is a new member of the Nod-like receptor family. Recently, NLRC5 has been reported to be expressed by microglia. Nonetheless, the exact roles of NLRC5 in microglial activation and its function in depression have not been investigated yet. Herein, we found that reducing NLRC5 decreased lipopolysaccharide (LPS)-induced secretion of pro-inflammatory cytokines (IL-1ß, IL-6, and TNF-α) in primary cultured microglia and microglial cell lines but not in bone marrow-derived macrophages (BMDMs). In more detail, reducing NLRC5 diminished the secretion of LPS-induced cytokines by attenuating IKKα/ß phosphorylation and inhibiting NF-κB signaling. Moreover, the expression of Nlrc5 in the hippocampus of LPS- or chronic unpredictable mild stress (CUMS)-induced depressive mice was increased. In line with the in vitro findings, Nlrc5 deficiency inhibited microglial activation in the mouse hippocampus and improved LPS- or CUMS-induced depressive-like behaviors. In summary, we demonstrated the critical role of NLRC5 in LPS-induced microglial activation and LPS- or CUMS-induced depressive mouse models.

Recruiting T-Cells toward the Brain for Enhanced Glioblastoma Immunotherapeutic Efficacy by Co-Delivery of Cytokines and Immune Checkpoint Antibodies with Macrophage-Membrane-Camouflaged Nanovesicles.

Immunotherapy with immune checkpoint inhibitors (CPIs) shows promising prospects for glioblastoma multiforme (GBM) but with restricted results, mainly attributed to the immunosuppressive tumor microenvironment (TME) and the limited antibody permeability of the blood-tumor barrier (BTB) in GBM. Here, nanovesicles with a macrophage-mimicking membrane are described, that co-deliver chemotactic CXC chemokine ligand 10 (CXCL10), to pre-activate the immune microenvironment, and anti-programmed death ligand 1 antibody (aPD-L1), to interrupt the immune checkpoint, aiming to enhance the effect of GBM immunotherapy. Consequently, the tumor tropism of the macrophage membrane and the receptor-mediated transcytosis of the angiopep-2 peptide allow the nanovesicle to effectively cross the BTB and target the GBM region, with 19.75-fold higher accumulation of antibodies compared to the free aPD-L1 group. The CPI therapeutic efficacy is greatly enhanced by CXCL10-induced T-cells recruitment with significant expansion of CD8+ T-cells and effector memory T-cells, leading to the elimination of tumor, prolonged survival time, and long-term immune memory in orthotopic GBM mice. The nanovesicles, that relieve the tumor immunosuppressive microenvironment by CXCL10 to enhance aPD-L1 efficacy, may present a promising strategy for brain-tumor immunotherapy.

B7 Family Members in Pancreatic Ductal Adenocarcinoma: Attractive Targets for Cancer Immunotherapy.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers, with a five-year survival rate of approximately 5-10%. The immune checkpoint blockade represented by PD-1/PD-L1 inhibitors has been effective in a variety of solid tumors but has had little clinical response in pancreatic cancer patients. The unique suppressive immune microenvironment is the primary reason for this outcome, and it is essential to identify key targets to remodel the immune microenvironment. Some B7 family immune checkpoints, particularly PD-L1, PD-L2, B7-H3, B7-H4, VISTA and HHLA2, have been identified as playing a significant role in the control of tumor immune responses. This paper provides a comprehensive overview of the recent research progress of some members of the B7 family in pancreatic cancer, which revealed that they can be involved in tumor progression through immune-dependent and non-immune-dependent pathways, highlighting the mechanisms of their involvement in tumor immune escape and assessing the prospects of their clinical application. Targeting B7 family immune checkpoints is expected to result in novel immunotherapeutic treatments for patients with pancreatic cancer.

First-principle calculations of the structural, vibrational, mechanical, electronic, and optical properties of ε-O8 under pressure.

The vibrational, mechanical, electronic, and optical properties of the ε-O8 phase in the pressure range of 11.4-70 GPa were studied by the first-principle calculation method. The phonon dispersion curves have a tiny virtual frequency at 60 GPa, which indicates that ε-O8 is dynamically unstable at 60 GPa. However, the 3-BM EOS demonstrates that the unit cell is stable up to 70 GPa. It has been shown that ε-O8 remains ductile within the whole applied pressure range. Concurrently, we calculated the variation of the band gap of ε-O8 in the pressure range of 11.4-70 GPa. The results show that the band gap of ε-O8 decreases with increasing pressure. Notably, the band gap disappears within the range of 50-60 GPa, which reveals that the metallic phase transition occurs within this pressure range.

Chinese endemic medicinal plant Bolbostemma paniculatum (Maxim.) Franquet: A comprehensive review.

Bolbostemma paniculatum (Maxim.) Franquet is a unique species in China with a long history of medicinal use, which has the effects of detoxifying, dissolving lumps and dispersing swellings. And it is commonly used to treat many diseases, such as carbuncle and sore, acute mastitis, mammary cancer, scrofula and subcutaneous nodule traditionally. Modern clinical studies have found that B. paniculatum and its compounds can be used for the treatment of a variety of cancers, mastitis, hyperplasia of mammary glands, chronic lymphadenitis, cervical lymph tuberculosis and surgical wart skin diseases, and the curative effect is positive. At present, a variety of Chinese patent medicines containing B. paniculatum have been exploited and marketed in China for the treatment of cancers, breast diseases and flat warts. This review article comprehensively discussed the traditional application, botany, chemical components, pharmacological activities, and quality control of B. paniculatum, put forward some noteworthy issues and suggestions in current studies, and briefly discussed the possible development potential of this plant as well as future research perspectives. 96 compounds have been isolated from B. paniculatum, including triterpenoids, sterols, alkaloids and other components, of which triterpenoid saponins are the main bioactive components. The crude extracts and monomer compounds of B. paniculatum have a wide range of pharmacological activities, such as anti-tumor, antiviral, anti-inflammatory, immunoregulatory, and so on. Moreover, its anti-tumor mechanism involves many aspects, including inhibiting cell proliferation, promoting cell apoptosis, blocking the cell cycle, interfering with cell invasion and metastasis, suppressing angiogenesis, and regulating autophagy. While there is a lack of systematic and in-depth research on its anti-tumor active components and mechanism of action at the moment; and a tight connection between the chemical composition and pharmacological activity of B. paniculatum has also not been established. Besides, a systematic quality determination standard for B. paniculatum should also be built, in order to carry out further research.

Expression pattern of NLRC5 in the postnatal mouse brain.

Nucleotide oligomerization domain-like receptors (NLRs), belonging to a large family of pattern recognition receptors, participate in the host's first line of defense against invading pathogens. Caspase recruitment domain containing 5 (NLRC5), the largest member in the NLR family, is demonstrated to be involved in the innate immune response and inflammatory diseases far and wide. Recent studies report that NLRC5 is associated with some central nervous system (CNS) diseases. Besides, NLRC5 is a mastery regulator for the expression of MHC class I both in the immune system and the CNS, while MHC class I is expressed and exerts its function in the brain. Therefore, it is necessary to investigate the expression pattern of NLRC5 in the developing and adult CNS. In our study, postnatal brain sections of C57BL/6 J mice are analyzed for the expression of NLRC5 protein by immunofluorescence. In the postnatal stages of developing telencephalon, NLRC5 exhibits a spatial and temporal expression pattern. NLRC5 is time-specifically expressed in subfields of hippocampus and different layers of prefrontal cortex. Moreover, it is shown that NLRC5 is highly cell type specific. It can be expressed in large quantities by neurons and microglia, but rarely expressed by astrocytes. Taken together, our research is important for further understanding the biological characteristics of NLRC5 and its function in the CNS.

Using structural analysis to explore the role of hepatitis B virus mutations in immune escape from liver cancer in Chinese, European and American populations.

Hepatitis B virus (HBV) infection is an important problem threatening human health. After HBV virus invades human body, it may assemble a complete virus particle in the cytoplasm to trigger the immune reaction, especially the interaction between the HBV virus and the host that mediated by CD8+ T cell. We collected the sequences of HBV from the HBVdb database, then screened candidate mutation sites in Chinese, European and American populations based on conservation and physicochemical properties. After that we constructed the three-dimensional structure of Major histocompatibility complex class I (MHC I) -peptide complexes, performed molecular docking, run molecular dynamics to compare the binding free energy, stability, and affinity of MHC I-peptide complexes with the aim to estimate the effect of peptide mutation. The specific HBV virus subtypes of the Chinese, European and American population were studied and the candidate mutation sites were used to predict the mutant peptide antigen. Finally, based on physical and chemical properties and peptide antigen prediction scores, 21 HBV mutation sites were selected. Then combined with specific Human lymphocyte antigen (HLA) subtypes, 11 mutations were found to have a significant negative impact on affinity, stability and binding free energy. Overall, our work found important potential mutations, which provide an evaluation of HBV mutations and a clue of it in immunotherapy. Communicated by Ramaswamy H. Sarma.

Screening HLA-A-restricted T cell epitopes of SARS-CoV-2 and the induction of CD8+ T cell responses in HLA-A transgenic mice.

Since severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-specific T cells have been found to play essential roles in host immune protection and pathology in patients with coronavirus disease 2019 (COVID-19), this study focused on the functional validation of T cell epitopes and the development of vaccines that induce specific T cell responses. A total of 120 CD8+ T cell epitopes from the E, M, N, S, and RdRp proteins were functionally validated. Among these, 110, 15, 6, 14, and 12 epitopes were highly homologous with SARS-CoV, OC43, NL63, HKU1, and 229E, respectively; in addition, four epitopes from the S protein displayed one amino acid that was distinct from the current SARS-CoV-2 variants. Then, 31 epitopes restricted by the HLA-A2 molecule were used to generate peptide cocktail vaccines in combination with Poly(I:C), R848 or poly (lactic-co-glycolic acid) nanoparticles, and these vaccines elicited robust and specific CD8+ T cell responses in HLA-A2/DR1 transgenic mice as well as wild-type mice. In contrast to previous research, this study established a modified DC-peptide-PBL cell coculture system using healthy donor PBMCs to validate the in silico predicted epitopes, provided an epitope library restricted by nine of the most prevalent HLA-A allotypes covering broad Asian populations, and identified the HLA-A restrictions of these validated epitopes using competitive peptide binding experiments with HMy2.CIR cell lines expressing the indicated HLA-A allotype, which initially confirmed the in vivo feasibility of 9- or 10-mer peptide cocktail vaccines against SARS-CoV-2. These data will facilitate the design and development of vaccines that induce antiviral CD8+ T cell responses in COVID-19 patients.

Tight Regulation of Major Histocompatibility Complex I for the Spatial and Temporal Expression in the Hippocampal Neurons.

The expression and function of immune molecules, such as major histocompatibility complex (MHC), within the developing and adult brain have been discovered over the past few years. Studies utilizing classical class I MHC knockout animals suggest that these molecules, in fact, play essential roles in the establishment, function, and modification of synapses in the CNS. Altered neuronal expression of class I MHC, as has been reported in pathological conditions, leads to aberrations in neuronal development and repair. In the hippocampus, cellular and molecular mechanisms that regulate synaptic plasticity have heretofore been extensively studied. It is for this reason that multiple studies directed at better understanding the expression, regulation, and function of class I MHC within the hippocampus have been undertaken. Since several previous reviews have addressed the roles of class I MHC in the formation and function of hippocampal connections, the present review will focus on describing the spatial and temporal expression of class I MHC in developing, healthy adult, and aging hippocampus. Herein, we also review current literatures exploring mechanisms that regulate class I MHC expression in murine hippocampus. With this review, we aim to facilitate a deeper mechanistic understanding into the complex tight regulation of MHC I expression in hippocampus, which are needed as we explore the potential for targeting MHC I for therapeutic intervention in normal aging and in neurodegenerative diseases in the future.

Multifunctional Liposomes Enable Active Targeting and Twinfilin 1 Silencing to Reverse Paclitaxel Resistance in Brain Metastatic Breast Cancer.

Paclitaxel (PTX) is a first-line chemotherapeutic drug for breast cancer, but PTX resistance often occurs in metastatic breast cancer. In addition, due to the poor targeting of chemotherapeutic drugs and the presence of the blood-brain barrier (BBB), it is hard to effectively treat brain metastatic breast cancer using paclitaxel. Thus, it is urgent to develop an effective drug delivery system for the treatment of brain metastatic breast cancer. The current study found that TWF1 gene, an epithelial-mesenchymal transition-associated gene, was overexpressed in brain metastatic breast cancer (231-BR) cells and was associated with the PTX resistance of 231-BR cells. Knockdown of TWF1 by small interference RNA (siRNA) in 231-BR cells could effectively increase the sensitivity of brain metastatic breast cancer cells to paclitaxel. Then, a liposome-based drug delivery system was developed for PTX delivery across BBB, enhancing PTX sensitivity and brain metastases targeting via BRBP1 peptide modification. The results showed that BRBP1-modified liposomes could effectively cross the BBB, specifically accumulate in brain metastases, and effectively interfere TWF1 gene expression in vitro and in vivo, and thus they enhanced proliferation inhibition, cell cycle arrest, and apoptosis induction, thereby inhibiting the formation and growth of brain metastases. In summary, our results indicated that BRBP1-modified and PTX- and TWF1 siRNA-loaded liposomes have the potential for the treatment of brain metastatic breast cancer, which lays the foundation for the development of a new targeted drug delivery system.

MiR34a Regulates Neuronal MHC Class I Molecules and Promotes Primary Hippocampal Neuron Dendritic Growth and Branching.

In the immune system, Major Histocompatibility Complex class I (MHC-I) molecules are located on the surface of most nucleated cells in vertebrates where they mediate immune responses. Accumulating evidence indicates that MHC-I molecules are also expressed in the central nervous system (CNS) where they play important roles that are significantly different from their immune functions. Classical MHC-I molecules are temporally and spatially expressed in the developing and adult CNS, where they participate in the synaptic formation, remodeling and plasticity. Therefore, clarifying the regulation of MHC-I expression is necessary to develop an accurate understanding of its function in the CNS. Here, we show that microRNA 34a (miR34a), a brain enriched noncoding RNA, is temporally expressed in developing hippocampal neurons, and its expression is significantly increased after MHC-I protein abundance is decreased in the hippocampus. Computational algorithms identify putative miR34a target sites in the 3'UTR of MHC-I mRNA, and here we demonstrate direct targeting of miR34a to MHC-I mRNA using a dual-luciferase reporter assay system. MiR34a targeting can decrease constitutive MHC-I expression in both Neuro-2a neuroblastoma cells and primary hippocampal neurons. Finally, miR34a mediated reduction of MHC-I results in increased dendritic growth and branching in cultured hippocampal neurons. Taken together, our findings identify miR34a as a novel regulator of MHC-I for shaping neural morphology in developing hippocampal neurons.

Targeted NIRF/MR dual-mode imaging of breast cancer brain metastasis using BRBP1-functionalized ultra-small iron oxide nanoparticles.

Tumor metastasis to brain is the main clinical manifestation of patients with advanced breast cancer, leading to poor survival prognosis. In order to detect the early incidence of brain metastasis, it is urgent to develop hypersensitive contrast agents for multimode imaging. In this study, PEG-phospholipids coated, a phage play derived peptide, BRBP1 peptide modified ultra-small iron oxide nanoparticles were prepared for targeted NIRF and MR imaging of breast cancer brain metastasis. The nanoparticles showed 10 nm core-shell, high relaxivity values and photon emission efficiency in vitro. The nanoparticles offered a T2 contrast imaging effect and near-infrared fluorescent signal enhancement. Compared with control peptide modified nanoparticles, the MR/NIRF imaging signal of BRBP1-modified nanoparticles in tumor tissue was significantly enhanced, which should be induced by the targeting ability of BRBP1 peptide. These results indicated that BRBP1-SPIO@mPEG (DiR) nanoparticles could be applied as an effective targeted delivery system for diagnosis of breast cancer brain metastasis.

Neuronal NLRC5 regulates MHC class I expression in Neuro-2a cells and also during hippocampal development.

Major histocompatibility Complex class I (MHC I) molecules are ubiquitously expressed, being found in most nucleated cells, where they are central mediators of both the adaptive and innate immune responses. Recent studies have shown that MHC I are also expressed in the developing brain where they participate in synapse elimination and plasticity. Up-regulation of MHC I within the developing brain has been reported, however, the mechanism(s) regulating this developmental up-regulation of neuronal MHC I remains unknown. Here, we show NLR family CARD domain containing 5 (NLRC5), a newly identified member of the NLR family, is widely expressed in hippocampal neurons, and the expression pattern of NLRC5 coincides with increased MHC I mRNA in the developing hippocampus. Using a luciferase assay in Neuro-2a cells we demonstrate that NLRC5 can induce the activation of MHC I and this induction requires the W/S-X-Y motif. Further studies show that transcription factors regulatory factor X (RFX) and CREB1, which bind to X1 and X2 box, are crucial for NLRC5-mediated induction. Moreover immunoprecipitation experiments reveal that NLRC5 interacts with RFX subunits RFX5 and RFXANK. Knockout of Nlrc5 dramatically impairs basal expression of MHC I in mouse hippocampus. Taken together, our findings identify NLRC5 as a key regulator of MHC I up-regulation in the developing hippocampus and suggest an important role for NLRC5 in neurons. Cover Image for this issue: doi: 10.1111/jnc.14729.

Specific, Non-Invasive, and Magnetically Directed Targeting of Magnetic Erythrocytes in Blood Vessels of Mice.

OBJECTIVE: Targeting in vivo has been a spotlight for precise medicine. Multiple strategies have been proposed for this issue. However, the efficiency of solely biochemical strategies currently remains to be improved. It has been thought that external field-guided targeting will be a beneficial supplement for the passive and the active targeting. METHODS: Here, we focused on the magnetic field-guided targeting of magnetized erythrocytes, discovering that a focused magnetic field can direct aggregation of magnetic erythrocytes into a specific region in vivo. RESULTS: The systematic investigation about the aggregates in cerebral vessels showed that the aggregates were isotropic and able to stably exist for six hours. The formation of cellular aggregates can alter echoing characteristic of the blood vessels meaning the vascular wall became more rigid. If the erythrocytes were repeatedly directed into aggregation in an identical region, a stable plaque of erythrocytes can form, which can mimic the process of thrombosis. SIGNIFICANCE: We believe these results will be beneficial to the development of novel engineered strategy for targeted delivery of drugs and modeling of vascular diseases.

MHC Class I Molecules and PirB Shape Neuronal Morphology by Affecting the Dendritic Arborization of Cortical Neurons.

Neuronal MHC class I proteins have been previously reported to regulate synaptic plasticity. Several reports indicate MHC class I proteins are expressed early during development of the nervous system, suggesting they may also play a role in neuronal development. Using cultured cortical neurons, we show MHC class I proteins aggregate at specific sites in neuronal cell bodies, which overlap with the actin cytoskeleton. Knockout of MHC class I in cultured neurons increases total dendritic length and the number of branch points. These effects are abolished by reintroducing MHC class I expression. Similarly, blocking of MHC class I proteins or PirB by an MHCI antibody or a soluble PirB ectodomain respectively, mimics the knock out phenotype of increased dendritic branching. This effect is correlated with decreased phosphorylation of both LIMK and cofilin, suggesting it may be mediated by an induction of cofilin activity. Finally, layer II and III cortical neurons in the sensorimotor region of an MHC class I deficiency mouse model show increased dendritic growth and branching. Altogether, our results suggest MHC class I plays a role in inhibiting or limiting the degree of dendrite arborization during the development of cortical neurons.

Platelet bio-nanobubbles as microvascular recanalization nanoformulation for acute ischemic stroke lesion theranostics.

Since the expected therapeutic results of ischemic stroke are strictly time dependent, early and accurate diagnosis as well as short intervals between diagnosis and treatment are key factors for the survival of stroke patients. In this study, we fabricated platelet (PLT) membrane-derived biomimetic nanobubbles (PNBs) for timely perfusion intervention and ultrasound imaging of acute ischemic stroke. Methods: The PNBs are fabricated by sonication-assisted reassembly of repeatedly freeze-thawed live platelet-derived PLT membrane vesicles (PMVs). The TEM, SEM, EDS and DLS were used to analyze the morphology and physicochemical properties of PNBs. The HPLC and LC-MS/MS were applied to confirm the lipid and protein compositions of PNBs. The in vitro macrophage uptake and platelet aggregation of PNBs were designed to examine the immune escape and thrombotic response characteristics. Furthermore, based on a photothrombotic ischemic stroke mouse model, the biodistribution, stroke microvascular network change, as well as cerebral blood flow of PNBs were studied by using near-infrared fluorescence imaging, multimodal optical imaging, and full-field laser perfusion imager. Finally, we assessed the brain ultrasound imaging of PNBs with a high-resolution micro-imaging system using both B-mode and contrast mode. Results: The natural lipid and protein components isolated from PLT membrane endow the PNBs with accurate lesion-targeting ability. The preferentially accumulated PNBs exhibit microvascular bio-remodeling ability of the stroke lesion, which is critical for recanalization of the obstructed vessels to protect the neural cells around the ischemic region of the stroke. Furthermore, with the increased accumulation of PNBs clusters in the lesion, PNBs in the lesion can be monitored by real-time contrast-enhanced ultrasound imaging to indicate the severity and dynamic development of the stroke. Conclusions: In summary, platelet membrane-based nanobubbles for targeting acute ischemic lesions were developed as microvascular recanalization nanoformulation for acute ischemic stroke lesion theranostics. This biomimetic PNBs theranostic strategy will be valuable for ischemic stroke patients in the future.

Modulation of the gamma-secretase activity as a therapy against human hepatocellular carcinoma.

OBJECTIVE: Hepatocellular carcinoma (HCC) is the fifth most common tumor worldwide. The discovery of new therapies against HCC is highly dependable on finding molecules which play essential roles in cancer development. The objective of this study was to evaluate the activity of gamma secretase (γ-secretase), and the antitumor effects of a γ-secretase inhibitor (GSI) in HCC. METHODS: The expression of presenilin 1 (PS1), a core component of γ-secretase, was examined by Western blot. Activity of γ-secretase was measured by a luciferase-based reporter system, and cancer cells were transfected either with PS1 dominant negative mutant (PS1D385A) or treated with GSI. RESULTS: Expression of PS1 was increased in HCC tissue and several HCC cell lines, which were accompanied by elevated γ-secretase activity. Cell colony formation and cell proliferation were decreased upon treatment with GSI but not with PS1D385A transfection. CONCLUSION: GSIs may be appealing candidates for the development of new therapies against HCC.