A kinase-cGAS cascade to synthesize a therapeutic STING activator.

The introduction of molecular complexity in an atom- and step-efficient manner remains an outstanding goal in modern synthetic chemistry. Artificial biosynthetic pathways are uniquely able to address this challenge by using enzymes to carry out multiple synthetic steps simultaneously or in a one-pot sequence1-3. Conducting biosynthesis ex vivo further broadens its applicability by avoiding cross-talk with cellular metabolism and enabling the redesign of key biosynthetic pathways through the use of non-natural cofactors and synthetic reagents4,5. Here we describe the discovery and construction of an enzymatic cascade to MK-1454, a highly potent stimulator of interferon genes (STING) activator under study as an immuno-oncology therapeutic6,7 (ClinicalTrials.gov study NCT04220866 ). From two non-natural nucleotide monothiophosphates, MK-1454 is assembled diastereoselectively in a one-pot cascade, in which two thiotriphosphate nucleotides are simultaneously generated biocatalytically, followed by coupling and cyclization catalysed by an engineered animal cyclic guanosine-adenosine synthase (cGAS). For the thiotriphosphate synthesis, three kinase enzymes were engineered to develop a non-natural cofactor recycling system in which one thiotriphosphate serves as a cofactor in its own synthesis. This study demonstrates the substantial capacity that currently exists to use biosynthetic approaches to discover and manufacture complex, non-natural molecules.

Holistic analytical characterization and risk assessment of residual host cell protein impurities in an active pharmaceutical ingredient synthesized by biocatalysts.

Host cell proteins (HCPs) are a significant class of process-related impurities commonly associated with the manufacturing of biopharmaceuticals. However, due to the increased use of crude enzymes as biocatalysts for modern organic synthesis, HCPs can also be introduced as a new class of impurities in chemical drugs. In both cases, residual HCPs need to be adequately controlled to ensure product purity, quality, and patient safety. Although a lot of attentions have been focused on defining a universally acceptable limit for such impurities, the risks associated with residual HCPs on product quality, safety, and efficacy often need to be determined on a case-by-case basis taking into consideration the residual HCP profile in the product, the dose, dosage form, administration route, and so forth. Here we describe the unique challenges for residual HCP control presented by the biocatalytic synthesis of an investigational stimulator of interferon genes protein agonist, MK-1454, which is a cyclic dinucleotide synthesized using Escherichia coli cell lysate overexpressing cyclic GMP-AMP synthase as a biocatalyst. In this study, a holistic characterization of residual protein impurities using a variety of analytical tools including nanoscale liquid chromatography coupled to tandem mass spectrometry, together with in silico immunogenicity prediction of identified proteins, facilitated risk assessment and guided process development to achieve adequate removal of residual protein impurities in MK-1454 active pharmaceutical ingredient.

Raman hyperspectral imaging with multivariate analysis for investigating enzyme immobilization.

Directed enzyme evolution has led to significant application of biocatalysis for improved chemical transformations throughout the scientific and industrial communities. Biocatalytic reactions utilizing evolved enzymes immobilized within microporous supports have realized unique advantages, including notably higher enzyme stability, higher enzyme load, enzyme reusability, and efficient product-enzyme separation. To date, limited analytical methodology is available to discern the spatial and chemical distribution of immobilized enzymes, in which techniques for surface visualization, enzyme stability, or activity are instead employed. New analytical tools to investigate enzyme immobilization are therefore needed. In this work, development, application, and evaluation of an analytical methodology to study enzyme immobilization is presented. Specifically, Raman hyperspectral imaging with principal component analysis, a multivariate method, is demonstrated for the first time to investigate evolved enzymes immobilized onto microporous supports for biocatalysis. Herein we demonstrate the ability to spatially and spectrally resolve evolved pantothenate kinase (PanK) immobilized onto two commercially-available, chemically-diverse porous resins. This analytical methodology is able to chemically distinguish evolved enzyme, resin, and chemical species pertinent to immobilization. As such, a new analytical approach to study immobilized biocatalysts is demonstrated, offering potential wide application for analysis of protein or biomolecule immobilization.

A survey on the attitudes of Chinese medical students towards current pathology education.

BACKGROUND: Pathology education provides information on pathology and guides students to become pathologists. Recently, the Ministry of Education of the People's Republic of China required the establishment of the system of 'High-quality Online and Offline Courses', which indicates that online courses will play an important role in higher education. Furthermore, the number of pathologists currently cannot satisfy clinical needs. To solve this health issue and implement the policy from the Ministry of Education, it is necessary to improve the current state of pathology education. First, we need to know students' opinions of the current courses and their professional choices. METHODS: Online questionnaires covering the quality of traditional courses, attitudes towards online courses, and suggestions for optimizing courses were designed and applied. Whether students want to become pathologists and the underlying reasons for this interest are also included in this survey. Participants are medical students from certain colleges in Nanjing. The collected data were assessed by statistical analyses, and p-values less than 0.05 were considered significant. RESULTS: Of the 342 valid responses, 60.94% of undergraduate students showed their interest in pathology courses, and among them, 48.72% expressed that they may become pathologists. However, the corresponding percentage is only 29.59% in the group without interest. To optimize curricula, the top two suggestions are introducing more clinical cases (undergraduate students, 64.45%; graduate students, 79.09%) and making the classes lively and interesting (undergraduate students, 59.77%; graduate students, 62.79%). Approximately 80.00% of students consider online courses to be good supplementary materials to traditional courses, and approximately half prefer an online-offline mixed learning model. Salary, interest, and employment status are the main factors influencing students' professional choices. CONCLUSIONS: Students are generally satisfied with traditional pathology courses, and online courses are good supplementary materials in their opinions. It has been suggested that clinical cases be introduced in classes. It is more likely that students who have an interest in pathology will become pathologists. The data from this survey also show that the main causes of the shortage of pathologists are a lack of engaging work and an unsatisfactory salary.

Impaired DNA double-strand breaks repair by kinesin family member 4A inhibition renders human H1299 non-small-cell lung cancer cells sensitive to cisplatin.

Patients with non-small-cell lung cancer (NSCLC) are routinely treated with the platinum-based chemotherapeutics such as cisplatin. The drug exerts anticancer effects via multiple mechanisms, including DNA double-strand breaks (DSBs). Enhanced DNA DSB repair capacity would be associated with innate or acquired drug resistance. However, despite strong evidence for the role of the chromokinesin kinesin family member 4A (KIF4A) in DSB repair, the relationship between the chromokinesin and cisplatin sensitivity of human NSCLC cells remains unknown. Furthermore, little is known regarding the effect of targeting KIF4A on the function of DSB repair-related proteins in these cells. In the current study, we demonstrated that cisplatin treatment stimulated the expression of KIF4A protein in human NSCLC cells. Depletion of KIF4A by small interfering RNA significantly enhanced cisplatin-induced cell cycle arrest in S and G2/M phases and cytotoxicity in human NSCLC cells. Furthermore, we found that KIF4A inhibition suppressed the ability of cisplatin to induce BRCA2 and Rad51 focus formation and limits the further increase in poly(ADP-ribose) polymerase 1 activity induced by cisplatin treatment in human NSCLC cells. These studies thus identify the chromokinesin KIF4A as a novel modulator of cisplatin sensitivity that is significantly enhanced by the chromokinesin in human NSCLC cells via multiple mechanisms.

In situ analytical characterization and chemical imaging of tablet coatings using laser induced breakdown spectroscopy (LIBS).

Laser induced breakdown spectroscopy (LIBS) has emerged as an innovative tool for quantitative and qualitative elemental analysis in pharmaceutical research. Herein, the potential use of LIBS for rapid characterization of tablet coatings is illustrated, including the investigation of coating thickness, coating uniformity and localized coating contamination. The laser shot number required for penetrating the coating correlates well with coating thickness determined from traditional scanning electron microscopy measurements. Each laser shot represents a 2.58 µm coating thickness. The inter-tablet coating uniformity was directly visualized using LIBS-based 3D chemical imaging, and the intra-tablet coating uniformity was quantitatively investigated. To our knowledge, this is the first report of 3D LIBS-based chemical imaging being utilized for quantitative analysis of pharmaceutical tablet coatings. In addition to elemental information, the accurate location of contaminants on the tablet coating was rapidly identified using 2D imaging. These results pave the way for LIBS to be a valuable technique for the analysis of pharmaceutical tablet coatings.

Alpha B-crystallin promotes the invasion and metastasis of colorectal cancer via epithelial-mesenchymal transition.

Alpha B-crystallin (CRYAB, HSPB5) is a protein that was first discovered in the lens of the eye. It is a member of the small heat-shock protein family (sHsps). CRYAB functions primarily as a molecular chaperone to prevent the aggregation and degradation of damaged unfolded proteins due to cellular damage resulting from heat shock, radiation, oxidative stress, and other insults, thereby promoting cell survival and preventing apoptosis. In recent years, the role of CRYAB in tumorigenesis, tumor invasion, and metastasis has received increasing attention. CRYAB is highly expressed in a variety of cancers, including breast cancer, head and neck cancer, and kidney cancer, and is likely associated with the prognosis of cancer. However, few studies have examined CRYAB in colorectal cancer (CRC). To study the effect of CRYAB on CRC, we transfected the CRC cell line SW480, which expresses high levels of CRYAB, with a lentiviral vector that inhibits CRYAB expression. The messenger RNA (mRNA) and protein expression of CRYAB was examined in the transfected SW480 cells (Si-CRYAB) using quantitative real-time polymerase chain reaction (qPCR) and Western blotting (WB) assays. Moreover, a growth curve was plotted to examine the proliferation of Si-CRYAB cells, and transwell assays were used to examine the migration of Si-CRYAB cells. Apoptosis and the cell cycle were examined in Si-CRYAB cells using flow cytometry (FCM), and the tumorigenic capability of Si-CRYAB cells was assessed in a nude mouse tumor model. Immunohistochemistry (IHC) was employed to examine CRYAB protein expression and the markers of epithelial-mesenchymal transition (EMT), such as E-cadherin, fibronectin, vimentin, and slug, in tumor tissues from nude mice and clinical invasive CRC and hepatic metastasis specimens. The qPCR and WB results showed that CRYAB was downregulated at the protein and mRNA level in Si-CRYAB cells, and the growth curve indicated that the proliferation of Si-CRYAB cells was reduced. Moreover, Si-CRYAB cells exhibited reduced migration capability in the transwell assay as well as increased apoptosis and G1 arrest in the FCM assay. The tumorigenesis study in nude mice showed that Si-CRYAB cells formed smaller tumors, indicating decreased tumorigenic capability. IHC results showed reduced CRYAB expression and lower levels of EMT in Si-CRYAB cells, whereas clinical specimens of invasive CRC and hepatic metastases exhibited elevated CRYAB expression and enhanced levels of EMT. These results demonstrated that CRYAB promoted the invasion and metastasis of CRC tumor cells via EMT.

In-Depth Structure and Function Characterization of Heterogeneous Interchain Cysteine-Conjugated Antibody-Drug Conjugates.

Antibody-drug conjugates (ADCs), integrating high specificity of antigen-targeting antibodies and high potency of cell-killing chemical drugs, have become one of the most rapidly expanding therapeutic biologics in oncology. Although ADCs were widely studied from multiple aspects, overall structural elucidation with comprehensive understanding of variants is scarcely reported. Here, for the first time, we present a holistic and in-depth characterization of an interchain cysteine-conjugated ADC, focusing on conjugation and charge heterogeneity, and in vitro biological activities. Conjugation mapping utilized a bottom-up approach, unraveled positional isomer composition, provided insights into the conjugation process, and elucidated how conjugation affects the physicochemical and biological properties of an ADC. Charge profiling combined bottom-up and top-down approaches to interrogate the origin of charge heterogeneity, its impact on function, and best practice for characterization. Specifically, we pioneered the utilization of capillary isoelectric focusing-mass spectrometry to decode not only critical post-translational modifications but also drug load and positional isomer distribution. The study design provides general guidance for in-depth characterization of ADCs, and the analytical findings in turn benefit the discovery and development of future ADCs.

Loss of fatty acid synthase inhibits the "HER2-PI3K/Akt axis" activity and malignant phenotype of Caco-2 cells.

BACKGROUND: Fatty acid synthase (FASN) is frequently activated and overexpressed in human cancers, and plays a crucial role in the carcinogenesis of various cancers. In this study, our aims were to explore the role of FASN in regulating the "HER2-PI3K/Akt axis" activity and malignant phenotype of colorectal cancer. METHODS: Caco-2 cells with a high expression of both HER2 and FASN were selected for functional characterization. Caco-2 cells were transfected with either the FASN specific RNAi plasmid or the negative control RNAi plasmid, followed by the RT-qPCR and western blot to examine the expression of FASN, HER2, PI3K and Akt. The MTT and colony formation assays were used to assess the proliferation potential. The migration was investigated by the transwell, and the apoptosis and cell cycle were assayed by the flow cytometry. RESULTS: Notably, the expression of FASN, HER2, PI3K and Akt were downregulated upon a silence of FASN. The proliferation was decreased after a downregulation of FASN, which was consistent with an increased apoptosis rate. The migration was also impaired in FASN-silenced cells. CONCLUSION: A downregulation of FASN effectively inhibits the activity of "HER2-PI3K/Akt axis" and alters the malignant phenotype in colorectal cancer cells.

Fatty acid synthase regulates proliferation and migration of colorectal cancer cells via HER2-PI3K/Akt signaling pathway.

Recent evidence suggests that fatty acid synthase mediating de novo fatty acid synthesis plays a crucial role in the carcinogenesis process of various cancers. Moreover, HER2 and related PI3K/Akt signaling pathway, which links intimately with cellular metabolism, influence cancer biological behavior. However, it remains unknown whether malignant phenotype of colorectal cancer cells is regulated by the HER2-PI3K/Akt-FASN signaling pathway. In this study, Caco-2 cells were selected for functional characterization, and treated with ZSTK474, followed by RT-qPCR and Western blot assays examining PI3K, Akt, HER2, and FASN expression. The MTT and colony formation assays were used to assess proliferation. The migration was investigated by transwell, apoptosis, and cell-cycle analysis. We found that the blockade of PI3K/Akt signaling pathway by ZSTK474 treatment led to downregulation of PI3K, Akt, HER2, and FASN expression. The proliferation was decreased upon treatment which was consistent with an increased percentage of G(1) arrested cells instead of apoptosis. The migration of Caco-2 cells was also impaired by ZSTK474 treatment. Inhibition of HER2-PI3K/Akt signaling pathway suppresses FASN expression of Caco-2 cells, and inhibition of FASN expression changes malignant phenotype of Caco-2 cells.

A novel multifunctional nanocomposite C225-conjugated Fe3O4/Ag enhances the sensitivity of nasopharyngeal carcinoma cells to radiotherapy.

Radiotherapy is the major treatment for nasopharyngeal carcinoma, a malignant tumor of epithelial origin. In this process, a tracer with high sensitivity is pivotal for diagnostic imaging in radiotherapy. Here, we designed a novel multifunctional magnetic silver nanocomposite, Fe(3)O(4)/Ag conjugated to an epidermal growth factor receptor-specific antibody (C225), which can be potentially used for synchronous cancer therapy and diagnosis via magnetic resonance imaging. Characteristics of Fe(3)O(4)/Ag/C225 were determined by transmission electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet spectra, and dynamic light scattering. The results demonstrated that Fe(3)O(4)/Ag/C225 nanoparticles were spherical and dispersed well in water. The activity of C225 was preserved ∼80% in the Fe(3)O(4)/Ag/C225 nanoparticles. Futhermore, we tested the cytotoxicity and radiosensitivity of the nanocomposite for human nasopharyngeal carcinoma cell lines (CNEs) in vitro. MTT analysis revealed that Fe(3)O(4)/Ag/C225 could inhibit the proliferation of CNEs in a dose- and time-dependent manner. The clonogenic assay indicated that Fe(3)O(4)/Ag/C225 combined with X-ray treatment could increase the sensitivity of CNEs to irradiation. In a summary, the novel multifunctional nanocomposite Fe(3)O(4)/Ag/C225 might be a potential radiosensitizer for treating malign tumors in the clinic.

Rapid catalyst identification for the synthesis of the pyrimidinone core of HIV integrase inhibitors.

A microscale chemistry improvement engine: a pre-dosed microscale high-throughput experimentation additives platform enables rapid, serendipitous reaction improvement. This platform allowed one chemist to set up 475 experiments and analyze the results using MISER chromatography in a single day, thus resulting in two high-quality catalytic systems for the construction of the title compound 1. Support for a single-electron transfer mechanism was obtained.

Clinicopathological Significance of Mucin 2 Immuno-histochemical Expression in Colorectal Cancer: A Meta-Analysis.

OBJECTIVE: To evaluate the association between mucin 2 (MUC2) expression and clinicopathological characters of colorectal cancer. METHODS: A literature search was performed on December 31, 2010 according to defined selection criteria. We evaluated the correlation between MUC2 (detected by immunohistochemistry) and clinicopathological characters of colorectal cancer. According to the tumor histological type, differentiation, location and TNM staging of colorectal carcinoma, we divided the clinicopathological characteristics into different subgroups. Fixed and random effects models were applied for estimation of the summarized risk ratios (RRs) and 95% confidence intervals (CIs) in different subgroups. Finally, forest plots and funnel plots were created to allow for visual comparison of the results or the effect of publication bias. RESULTS: According with the inclusive criteria, fourteen studies (n=1,558) were eligible for the meta-analysis. We observed a trend towards a correlation of MUC2 higher positivity in mucinous than non-mucinous carcinoma (RR, 2.10; 95% CI, 1.30-3.40; P=0.002) and less positivity in distal than proximal colon (RR, 0.74; 95% CI, 0.64-0.85; P=0.000). There was no statistically significance for the association between MUC2 expression and differentiation or TNM staging of colorectal cancer, but MUC2 overexpression tended to be associated with the presence of T stage tumor (RR, 1.17; P=0.052). CONCLUSION: MUC2 overexpression was associated with the mucinous and proximal colorectal cancer.

Quantitation and speciation of residual protein within active pharmaceutical ingredients using image analysis with SDS-PAGE.

Recent advances in biocatalysis and directed enzyme evolution has led to a variety of enzymatically-driven, elegant processes for active pharmaceutical ingredient (API) production. For biocatalytic processes, quantitation of any residual protein within a given API is of great importance to ensure process robustness and quality, pure pharmaceutical products. Typical analytical methods for analyzing residual enzymes within an API, such as enzyme-linked immunosorbent assays (ELISA), colorimetric assays, and liquid chromatographic techniques, are limited for determining only the concentration of known proteins and require harsh solvents with high API levels for analysis. For the first time, total residual protein content in a small molecule API was quantitated using image analysis applied to SDS-PAGE. Herein, a proposed methodology for residual protein detection, quantitation, and size-based speciation is presented, in which an orthogonal technique is offered to traditional analysis methods, such as ELISA. Results indicate that our application of the analytical methodology is able to reliably quantitate both protein standards and the total residual protein present within a final API, with good agreement as compared to traditional ELISA results. Further, speciation of the residual protein within the API provides key information concerning the individual residual proteins present, including their molecular weight, which can lead to improved process development efforts for residual protein rejection and control. This analytical methodology thus offers an alternative tool for easily identifying, quantitating, and speciating residual protein content in the presence of small molecule APIs, with potential for wide applicability across industry for biocatalytic or directed enzyme evolution efforts within process development.

Suppression of mucin 2 enhances the proliferation and invasion of LS174T human colorectal cancer cells.

Altered expression of MUC2 (mucin 2) is related to tumour development in colorectal cancer. Colorectal mucinous carcinomas are positive for MUC2 expression, whereas MUC2 is down-regulated in non-mucinous adenocarcinomas. In the present study, we down-regulated MUC2 expression by RNAi (RNA interference) and investigated the in vitro and in vivo effects on the proliferation and invasion/migration potential of the LS174T human colorectal cancer cells. The LS174T cell line is a goblet-cell-like colorectal cancer cell line that continuously produces high levels of MUC2. Inhibition of MUC2 expression in vitro by transfection of LS174T cells with the recombinant plasmid pcDNA6.2-GW/EmGFP-miR-MUC2 led to the production of a stably transfected MUC2-RNAi LS174T cell line. The proliferation and invasion/migration of MUC2-RNAi cells in vitro were significantly higher than those in control cells, as assessed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide], colony formation and transwell assays. Subcutaneous injection of MUC2-RNAi LS174T cells into nude mice resulted in the development of subcutaneous tumours visible to the naked eye after 1 week. The growth rate of tumours derived from MUC2-RNAi LS174T cells was greater than that of tumours derived from control cells. Ki67 and matrix metalloproteinase-9 proteins were detected by immunohistochemistry in the xenografts. The expression levels of these proteins were higher in the MUC2-RNAi-derived xenografts than in xenografts derived from control cells. Although the role of MUC2 in colorectal tumorigenesis is not fully understood, these results strongly suggest a relationship between the proliferation and invasion of LS174T cells and the expression of MUC2.

Simultaneous multielement imaging of liver tissue using laser ablation inductively coupled plasma mass spectrometry.

Analysis of the spatial distribution of metals, metalloids, and non-metals in biological tissues is of significant interest in the life sciences, helping to illuminate the function and roles these elements play within various biological pathways. Chemical imaging methods are commonly employed to address biological questions and reveal individual spatial distributions of analytes of interest. Elucidation of these spatial distributions can help determine key elemental and molecular information within the respective biological specimens. However, traditionally utilized imaging methods prove challenging for certain biological tissue analysis, especially with respect to applications that require high spatial resolution or depth profiling. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been shown to be effective for direct elemental analysis of solid materials with high levels of precision. In this work, chemical imaging using LA-ICP-MS has been applied as a powerful analytical methodology for the analysis of liver tissue samples. The proposed analytical methodology successfully produced both qualitative and quantitative information regarding specific elemental distributions within images of thin tissue sections with high levels of sensitivity and spatial resolution. The spatial resolution of the analytical methodology was innovatively enhanced, helping to broaden applicability of this technique to applications requiring significantly high spatial resolutions. This information can be used to further understand the role these elements play within biological systems and impacts dysregulation may have.

Macrocyclic glycopeptide chiral selectors bonded to core-shell particles enables enantiopurity analysis of the entire verubecestat synthetic route.

Verubecestat is an inhibitor of ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) being evaluated in clinical trials for the treatment of Alzheimer's disease. Synthetic route development involves diastereoselective transformations with a need for enantiomeric excess (ee) determination of each intermediate and final active pharmaceutical ingredient (API). The analytical technical package of validated methods relies on enantioselective SFC and RPLC separations using multiple 3 and 5 µm coated polysaccharide-based chiral stationary phases (CSPs) and mobile phases combinations. Evaluation of recently developed chiral columns revealed a single chiral selector (Teicoplanin) bonded to 2.7 µm core-shell particles using H3PO4 in H2O/ACN and triethylammonium acetate: methanol based eluents at different isocratic compositions allowed good enatioseparation of all verubecestat intermediates. EE determination of verubecestat is easily performed on NicoShell, another macrocyclic glycopeptide chiral selector bonded to 2.7 µm superficially porous particles. This approach enables fast and reliable enantiopurity analysis of the entire verubecestat synthetic route using only two chiral columns and mobile phases on a conventional HPLC system, simplifying technical package preparation, method validation and transfer to manufacturing facilities.

Online sensing of palladium in flowing streams.

Rapid palladium (Pd) catalyzed deallylation of an uncoloured reagent within a flowing stream affords a dose dependent colour formation that can be used for convenient online analysis of trace levels of Pd contamination using a modified HPLC instrument. An application to the online sensing of Pd breakthrough from a flow through Pd adsorption cartridge is described. An alternative configuration of the instrumentation allows the rapid (<1 min) and accurate measurement of Pd levels within samples injected via a conventional HPLC autosampler.

Up-regulation of OLR1 expression by TBC1D3 through activation of TNFα/NF-κB pathway promotes the migration of human breast cancer cells.

Metastatic spread of cancer cells is the most life-threatening aspect of breast cancer and involves multiple steps including cell migration. We recently found that the TBC1D3 oncogene promotes the migration of breast cancer cells, and its interaction with CaM enhances the effects of TBC1D3. However, little is known regarding the mechanism by which TBC1D3 induces the migration of cancer cells. Here, we demonstrated that TBC1D3 stimulated the expression of oxidized low density lipoprotein receptor 1 (OLR1), a stimulator of cell migration, in breast cancer cells at the transcriptional level. Depletion of OLR1 by siRNAs or down-regulation of OLR1 expression using pomalidomide, a TNFα inhibitor, significantly decreased TBC1D3-induced migration of these cells. Notably, TBC1D3 overexpression activated NF-κB, a major effector of TNFα signaling, while inhibition of TNFα signaling suppressed the effects of TBC1D3. Consistent with this, NF-κB inhibition using its specific inhibitor caffeic acid phenethyl ester decreased both TBC1D3-induced OLR1 expression and cell migration, suggesting a critical role for TNFα/NF-κB signaling in TBC1D3-induced migration of breast cancer cells. Mechanistically, TBC1D3 induced activation of this signaling pathway on multiple levels, including by increasing the release of TNFα, elevating the transcription of TNFR1, TRAF1, TRAF5 and TRAF6, and decreasing the degradation of TNFR1. In summary, these studies identify the TBC1D3 oncogene as a novel regulator of TNFα/NF-κB signaling that mediates this oncogene-induced migration of human breast cancer cells by up-regulating OLR1.

Calmodulin promotes matrix metalloproteinase 9 production and cell migration by inhibiting the ubiquitination and degradation of TBC1D3 oncoprotein in human breast cancer cells.

The hominoid oncoprotein TBC1D3 enhances growth factor (GF) signaling and GF signaling, conversely, induces the ubiquitination and subsequent degradation of TBC1D3. However, little is known regarding the regulation of this degradation, and the role of TBC1D3 in the progression of tumors has also not been defined. In the present study, we demonstrated that calmodulin (CaM), a ubiquitous cellular calcium sensor, specifically interacted with TBC1D3 in a Ca2+-dependent manner and inhibited GF signaling-induced ubiquitination and degradation of the oncoprotein in both cytoplasm and nucleus of human breast cancer cells. The CaM-interacting site of TBC1D3 was mapped to amino acids 157~171, which comprises two 1-14 hydrophobic motifs and one lysine residue (K166). Deletion of these motifs was shown to abolish interaction between TBC1D3 and CaM. Surprisingly, this deletion mutation caused inability of GF signaling to induce the ubiquitination and subsequent degradation of TBC1D3. In agreement with this, we identified lysine residue 166 within the CaM-interacting motifs of TBC1D3 as the actual site for the GF signaling-induced ubiquitination using mutational analysis. Point mutation of this lysine residue exhibited the same effect on TBC1D3 as the deletion mutant, suggesting that CaM inhibits GF signaling-induced degradation of TBC1D3 by occluding its ubiquitination at K166. Notably, we found that TBC1D3 promoted the expression and activation of MMP-9 and the migration of MCF-7 cells. Furthermore, interaction with CaM considerably enhanced such effect of TBC1D3. Taken together, our work reveals a novel model by which CaM promotes cell migration through inhibiting the ubiquitination and degradation of TBC1D3.