Overexpression of cell surface cytokeratin 8 in multidrug-resistant MCF-7/MX cells enhances cell adhesion to the extracellular matrix

Complement Regulatory Protein CD46 Manifests a Unique Role in Promoting the Migration of Bladder Cancer Cells

CD46 is a membrane-bound complement regulatory protein (mCRP) possessing a regulatory role with the complement system. CD46 protects the host cells from damage by complement. Expression of CD46 is also highly maintained in many cancers, including bladder cancers, and thus functions as a receptor for many cancer therapeutic viruses. In this study we report a unique role of CD46 as a progression factor of cancer cells in bladder cancers. Resulting data from a DNA microarray using CD46-altered HT1376 bladder cancers demonstrated a pool of target genes, including complement C3 α chain (C3α), matrix Gla protein (MGP), AFAP-AS1, follicular dendritic cell secreted protein (FDCSP), MAM domain containing 2 (MAMDC2), gamma-aminobutyric acid A receptor pi (GABRP), transforming growth factor, beta-induced (TGFBI), a family of cytochrome P450 (CYP24A1), sialic acid binding Ig-like lectin 6 (SIGLEC6), metallothionein 1E (MT1E), and several members of cytokeratins. Subsequent studies using quantitative RT-PCR and Western blot analyses confirmed CD46-mediated regulation of C3α, MGP, and keratin 13 (KRT13). MGP and KRT13 are known to be involved in cell migration and cancer cell metastasis. A cell migration assay demonstrated that CD46 enhanced migratory potential of bladder cancer cells. Taken all together, this report demonstrated that CD46 is generally overexpressed in bladder cancers and plays a unique role in the promotion of cancer cell migration. Further detailed studies are needed to be performed to clarify the action mechanism of CD46 and its application to cancer therapeutics.

Update of the keratin gene family: evolution, tissue-specific expression patterns, and relevance to clinical disorders

Intermediate filament (IntFil) genes arose during early metazoan evolution, to provide mechanical support for plasma membranes contacting/interacting with other cells and the extracellular matrix. Keratin genes comprise the largest subset of IntFil genes. Whereas the first keratin gene appeared in sponge, and three genes in arthropods, more rapid increases in keratin genes occurred in lungfish and amphibian genomes, concomitant with land animal-sea animal divergence (~ 440 to 410 million years ago). Human, mouse and zebrafish genomes contain 18, 17 and 24 non-keratin IntFil genes, respectively. Human has 27 of 28 type I "acidic" keratin genes clustered at chromosome (Chr) 17q21.2, and all 26 type II "basic" keratin genes clustered at Chr 12q13.13. Mouse has 27 of 28 type I keratin genes clustered on Chr 11, and all 26 type II clustered on Chr 15. Zebrafish has 18 type I keratin genes scattered on five chromosomes, and 3 type II keratin genes on two chromosomes. Types I and II keratin clusters-reflecting evolutionary blooms of keratin genes along one chromosomal segment-are found in all land animal genomes examined, but not fishes; such rapid gene expansions likely reflect sudden requirements for many novel paralogous proteins having divergent functions to enhance species survival following sea-to-land transition. Using data from the Genotype-Tissue Expression (GTEx) project, tissue-specific keratin expression throughout the human body was reconstructed. Clustering of gene expression patterns revealed similarities in tissue-specific expression patterns for previously described "keratin pairs" (i.e., KRT1/KRT10, KRT8/KRT18, KRT5/KRT14, KRT6/KRT16 and KRT6/KRT17 proteins). The ClinVar database currently lists 26 human disease-causing variants within the various domains of keratin proteins.

Cyclophilins A and B oppositely regulate renal tubular epithelial cell phenotype

Restoration of kidney tubular epithelium following sublethal injury sequentially involves partial epithelial–mesenchymal transition (pEMT), proliferation, and further redifferentiation into specialized tubule epithelial cells (TECs). Because the immunosuppressant cyclosporine-A produces pEMT in TECs and inhibits the peptidyl-prolyl isomerase (PPIase) activity of cyclophilin (Cyp) proteins, we hypothesized that cyclophilins could regulate TEC phenotype. Here we demonstrate that in cultured TECs, CypA silencing triggers loss of epithelial features and enhances transforming growth factor β (TGFβ)-induced EMT in association with upregulation of epithelial repressors Slug and Snail. This pro-epithelial action of CypA relies on its PPIase activity. By contrast, CypB emerges as an epithelial repressor, because CypB silencing promotes epithelial differentiation, prevents TGFβ-induced EMT, and induces tubular structures in 3D cultures. In addition, in the kidneys of CypB knockout mice subjected to unilateral ureteral obstruction, inflammatory and pro-fibrotic events were attenuated. CypB silencing/knockout leads to Slug, but not Snail, downregulation. CypB support of Slug expression depends on its endoplasmic reticulum location, where it interacts with calreticulin, a calcium-buffering chaperone related to Slug expression. As CypB silencing reduces ionomycin-induced calcium release and Slug upregulation, we suggest that Slug expression may rely on CypB modulation of calreticulin-dependent calcium signaling. In conclusion, this work uncovers new roles for CypA and CypB in modulating TEC plasticity and identifies CypB as a druggable target potentially relevant in promoting kidney repair.

Morphology-Predicted Large-Scale Transition Number in Circulating Tumor Cells Identifies a Chromosomal Instability Biomarker Associated with Poor Outcome in Castration-Resistant Prostate Cancer

Chromosomal instability (CIN) increases a tumor cell's ability to acquire chromosomal alterations, a mechanism by which tumor cells evolve, adapt, and resist therapeutics. We sought to develop a biomarker of CIN in circulating tumor cells (CTC) that are more likely to reflect the genetic diversity of patient's disease than a single-site biopsy and be assessed rapidly so as to inform treatment management decisions in real time. Large-scale transitions (LST) are genomic alterations defined as chromosomal breakages that generate chromosomal gains or losses of greater than or equal to10 Mb. Here we studied the relationship between the number of LST in an individual CTC determined by direct sequencing and morphologic features of the cells. This relationship was then used to develop a computer vision algorithm that utilizes CTC image features to predict the presence of a high (9 or more) versus low (8 or fewer) LST number in a single cell. As LSTs are a primary functional component of homologous recombination deficient cellular phenotypes, the image-based algorithm was studied prospectively on 10,240 CTCs in 367 blood samples obtained from 294 patients with progressing metastatic castration-resistant prostate cancer taken prior to starting a standard-of-care approved therapy. The resultant computer vision-based biomarker of CIN in CTCs in a pretreatment sample strongly associated with poor overall survival times in patients treated with androgen receptor signaling inhibitors and taxanes. SIGNIFICANCE: A rapidly assessable biomarker of chromosomal instability in CTC is associated with poor outcomes when detected in men with progressing mCRPC.

The Effect of Protein FAM172A on Proliferation in HepG2 Cells and Investigation of the Possible Molecular Mechanism

Background

In our previous study, we found that the FAM172A recombinant protein could promote proliferation of L02 cells. However, the underlying mechanisms are still unknown. The present study was aimed at investigating the effect of FAM172A on proliferation of HepG2 cells and exploring the possible molecular mechanisms and its role in hepatocellular carcinoma (HCC).

Methods

Cell proliferation was measured by MTT assay. Western blot test was carried out to investigate the mechanism. Rabbit antibodies against FAM172A and membrane proteins isolated from lysate of HepG2 cell were coprecipitated and the resultant precipitates were analyzed by mass spectrum.

Results

The MTT assay showed that recombinant protein FAM172A isoform 1 (FAM172A-1) could induce HepG2 cell proliferation at the concentration of 10-100 ng/mL, while protein FAM172A isoform 3 (FAM172A-3) was at the concentration of 80-100 ng/mL. Western blot demonstrated that both FAM172A-1 and FAM172A-3 could activate the mitogen-activated protein kinase/extracellular signal-regulated protein kinase (MAPK/ERK) pathway and the phosphatidylinositol 3-kinase/threonine-protein kinase (PI3K/Akt) pathway. Mass spectrum analysis suggested that there were some membrane proteins interacting with FAM172A. Several candidate interacting proteins might mediate proliferation signals induced by FAM172A recombinant protein, including seven membrane proteins.

Conclusion

In conclusion, FAM172A recombinant protein could induce proliferation of HepG2 cells, in which the MAPK/ERK and PI3K/Akt signaling pathways might be involved. The role of FAM172A in HepG2 cell proliferation also indicated its possible involvement in HCC. The receptor of FAM172A on cells still needs to be exploited.

Single Cell Mass Cytometry of Non-Small Cell Lung Cancer Cells Reveals Complexity of In vivo And Three-Dimensional Models over the Petri-dish

Single cell genomics and proteomics with the combination of innovative three-dimensional (3D) cell culture techniques can open new avenues toward the understanding of intra-tumor heterogeneity. Here, we characterize lung cancer markers using single cell mass cytometry to compare different in vitro cell culturing methods: two-dimensional (2D), carrier-free, or bead-based 3D culturing with in vivo xenografts. Proliferation, viability, and cell cycle phase distribution has been investigated. Gene expression analysis enabled the selection of markers that were overexpressed: TMEM45A, SLC16A3, CD66, SLC2A1, CA9, CD24, or repressed: EGFR either in vivo or in long-term 3D cultures. Additionally, TRA-1-60, pan-keratins, CD326, Galectin-3, and CD274, markers with known clinical significance have been investigated at single cell resolution. The described twelve markers convincingly highlighted a unique pattern reflecting intra-tumor heterogeneity of 3D samples and in vivo A549 lung cancer cells. In 3D systems CA9, CD24, and EGFR showed higher expression than in vivo. Multidimensional single cell proteome profiling revealed that 3D cultures represent a transition from 2D to in vivo conditions by intermediate marker expression of TRA-1-60, TMEM45A, pan-keratin, CD326, MCT4, Gal-3, CD66, GLUT1, and CD274. Therefore, 3D cultures of NSCLC cells bearing more putative cancer targets should be used in drug screening as the preferred technique rather than the Petri-dish.

Highly multiplexed profiling of cell surface proteins on single circulating tumor cells based on antibody and cellular barcoding

Circulating tumor cells (CTCs) are extraordinarily rare in blood samples and represent a real-time "liquid biopsy" of tumors. Although genetic and transcriptional sequencing of single CTCs has been reported, these methods fail to provide phenotypic and functional information of CTCs such as protein levels of surface proteins. Studies of single-cell proteomic assays of CTCs have been rare because of a lack of single-cell proteomic methods to handle and analyze rare cells in a high background of non-target cells with high sensitivity, throughput, and multiplexing capacity. Here, we develop a microchip-assisted single-cell proteomic method for profiling surface proteins of CTCs based on antibody and cellular DNA barcoding strategy. We combine DNA-encoded antibody tags and cell indexes to profile 15 proteins in ~ 100 single rare cells simultaneously, and use high-throughput sequencing as the readout to generate surface protein profiles of CTCs according to their cell indexes and antibody-derived protein barcodes. A 6400-well microchip and the automated puncher are used to rapidly retrieve single CTCs from enriched CTC population with minimal cell loss (~ 10%). This technological platform integrates reliable isolation and proteomic analysis of single CTCs and can be extendable to ~ 100 proteins in hundreds of rare cells with single-cell precision.

Externalized Keratin 8: A Target at the Interface of Microenvironment and Intracellular Signaling in Colorectal Cancer Cells

Accumulating evidence supports the remarkable presence at the membrane surface of cancer cells of proteins, which are normally expressed in the intracellular compartment. Although these proteins, referred to as externalized proteins, represent a highly promising source of accessible and druggable targets for cancer therapy, the mechanisms via which they impact cancer biology remain largely unexplored. The aim of this study was to expose an externalized form of cytokeratin 8 (eK8) as a key player of colorectal tumorigenesis and characterize its mode of action. To achieve this, we generated a unique antagonist monoclonal antibody (D-A10 MAb) targeting an eight-amino-acid-long domain of eK8, which enabled us to ascertain the pro-tumoral activity of eK8 in both KRAS-mutant and wild-type colorectal cancers (CRC). We showed that this pro-tumoral activity involves a bidirectional eK8-dependent control of caspase-mediated apoptosis in vivo and of the plasminogen-induced invasion process in cellulo. Furthermore, we demonstrated that eK8 is anchored at the plasma membrane supporting this dual function. We, therefore, identified eK8 as an innovative therapeutic target in CRC and provided a unique MAb targeting eK8 that displays anti-neoplastic activities that could be useful to treat CRC, including those harboring KRAS mutations.

Cytokeratin-8 in Anaplastic Thyroid Carcinoma: More Than a Simple Structural Cytoskeletal Protein

Anaplastic thyroid carcinoma (ATC) is almost universally fatal. Elevated keratin-8 (KRT8) protein expression is an established diagnostic cancer biomarker in several epithelial cancers (but not ATC). Several keratins, including KRT8, have been suggested to have a role in cell biology beyond that of structural cytoskeletal proteins. Here, we provide evidence that KRT8 plays a direct role in the growth of ATCs. Genomic and transcriptomic analysis of >5000 patients demonstrates that KRT8 mutation and copy number amplification are frequently evident in epithelial-derived cancers. Carcinomas arising from diverse tissues exhibit KRT8 mRNA and protein overexpression when compared to normal tissue levels. Similarly, in a panel of patient-derived ATC cell lines and patient tumors, KRT8 expression shows a similar pattern. sh-RNA-mediated KRT8 knockdown in these cell lines increases apoptosis, whereas forced overexpression of KRT8 confers resistance to apoptosis under peroxide-induced cell stress conditions. We further show that KRT8 protein binds to annexin A2, a protein known to mediate apoptosis as well as the redox pathway.

Establishment of a human primary pancreatic cancer mouse model to examine and investigate gemcitabine resistance

Pancreatic cancer is one of the most fatal types of cancer and is associated with a dismal prognosis. Gemcitabine-based chemotherapy is clinically used for the treatment of advanced pancreatic cancer. However, many forms of pancreatic cancer have acquired resistance to gemcitabine. In order to prevent patients from suffering from the side effects of chemotherapy and to have the chance to receive more effective intervention, assessment of whether the patient pancreatic cancer cells are resistant to gemcitabine before clinical practice is crucial. Recently, patient-derived xenograft (PDX) models have been regarded as a practical approach for preclinical drug resistance test. In the present study, we harvested tumor specimens from 28 pancreatic cancer patients to establish PDX models. The tumor formation rate of the xenografts was 100%, several of which could be re-implanted in nude mice for more than 10 passages. Primary cells were further obtained from the PDX xenografts to determine their morphological features and evaluate their proliferation rate, migration capacity and angiopoietic ability. In addition, the sensitivities of the primary cells and PDX xenografts to gemcitabine were correlated with each other. When compared to the gemcitabine-sensitive cells, the gemcitabine-resistant cells had a higher level of MCF2L expression, suggesting that MCF2L plays an important role in gemcitabine resistance.

Comparative proteomic analysis of melanosis coli with colon cancer

The present study aimed to investigate the proteomic difference between melanosis coli (MC) alone and melanosis coli with colon cancer (MCCC). Protein expression in patients with different diseases was analyzed using two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/TOF-MS). A total of 14 protein differences with a confidence level of >95% were found. There were six differences between MC and normal tissues, in which two proteins exhibited upregulated expression levels and four proteins exhibited downregulated expression levels in MC. Furthermore, one protein was expressed only in MC (P<0.05). In addition, there were differences in the expression of eight proteins between MC and MCCC tissues, in which one protein had an upregulated expression in MC tissues and seven proteins had an upregulated expression in MCCC tissues. Furthermore, two proteins were only expressed in MCCC tissues (P<0.05). Eight proteins were identified using mass spectrometry and database search. In conclusion, comparative proteomics accurately displayed the expression differences in eight proteins between MC, MCCC and normal colon tissues.

Keratin 13 Is Enriched in Prostate Tubule-Initiating Cells and May Identify Primary Prostate Tumors that Metastasize to the Bone

Background

Benign human prostate tubule-initiating cells (TIC) and aggressive prostate cancer display common traits, including tolerance of low androgen levels, resistance to apoptosis, and microenvironment interactions that drive epithelial budding and outgrowth. TIC can be distinguished from epithelial and stromal cells that comprise prostate tissue via cell sorting based upon Epcam, CD44, and CD49f antigenic profiles. Fetal prostate epithelial cells (FC) possess a similar antigenic profile to adult TIC and are capable of inducing tubule formation. To identify the TIC niche in human prostate tissue, differential keratin (KRT) expression was evaluated.

Results

Gene expression data generated from Affymetrix Gene Chip human U133 Plus 2.0 array of sorted adult and fetal epithelial cells revealed KRT13 to be significantly enriched in FC and TIC compared to basal cells (BC) and luminal cells (LC) (p<0.001). Enriched KRT13 expression was confirmed by RT-PCR and cytospin immunostaining. Immunohistochemical analysis of KRT13 expression revealed rare KRT13⁺ epithelia throughout prostatic ducts/acini in adult tissue specimens and differentiated tubules in 24-week recombinant grafts, In contrast, abundant KRT13 expression was observed in developing ducts/acini in fetal prostate and cord-like structures composing 8-week recombinant grafts. Immunostaining of a prostate tissue microarray revealed KRT13⁺ tumor foci in approximately 9% of cases, and this subset displayed significantly shorter time to recurrence (p = 0.031), metastases (p = 0.032), and decreased overall survival (p = 0.004). Diagnostic prostate needle biopsies (PNBX) from untreated patients with concurrent bone metastases (clinical stage M1) displayed KRT13⁺ tumor foci, as did bone metastatic foci.

Conclusions

The expression profile of KRT13 in benign fetal and adult prostate tissue and in recombinant grafts, as well as the frequency of KRT13 expression in primary and metastatic prostate cancer indicates that it may be a marker of a stem/progenitor-like cell state that is co-opted in aggressive tumor cells. KRT13 is enriched in benign stem-like cells that display androgen-resistance, apoptosis-resistance, and branching morphogenesis properties. Collectively our data demonstrate that KRT13 expression is associated with poor prognosis at multiple stages of disease progression and may represent an important biomarker of adverse outcome in patients with prostate cancer.

EpCAM-Independent Enrichment of Circulating Tumor Cells in Metastatic Breast Cancer

Circulating tumor cells (CTCs) are the potential precursors of metastatic disease. Most assays established for the enumeration of CTCs so far-including the gold standard CellSearch-rely on the expression of the cell surface marker epithelial cell adhesion molecule (EpCAM). But, these approaches may not detect CTCs that express no/low levels of EpCAM, e.g. by undergoing epithelial-to-mesenchymal transition (EMT). Here we present an enrichment strategy combining different antibodies specific for surface proteins and extracellular matrix (ECM) components to capture an EpCAMlow/neg cell line and EpCAMneg CTCs from blood samples of breast cancer patients depleted for EpCAM-positive cells. The expression of respective proteins (Trop2, CD49f, c-Met, CK8, CD44, ADAM8, CD146, TEM8, CD47) was verified by immunofluorescence on EpCAMpos (e.g. MCF7, SKBR3) and EpCAMlow/neg (MDA-MB-231) breast cancer cell lines. To test antibodies and ECM proteins (e.g. hyaluronic acid (HA), collagen I, laminin) for capturing EpCAMneg cells, the capture molecules were first spotted in a single- and multi-array format onto aldehyde-coated glass slides. Tumor cell adhesion of EpCAMpos/neg cell lines was then determined and visualized by Coomassie/MitoTracker staining. In consequence, marginal binding of EpCAMlow/neg MDA-MB-231 cells to EpCAM-antibodies could be observed. However, efficient adhesion/capturing of EpCAMlow/neg cells could be achieved via HA and immobilized antibodies against CD49f and Trop2. Optimal capture conditions were then applied to immunomagnetic beads to detect EpCAMneg CTCs from clinical samples. Captured CTCs were verified/quantified by immunofluorescence staining for anti-pan-Cytokeratin (CK)-FITC/anti-CD45 AF647/DAPI. In total, in 20 out of 29 EpCAM-depleted fractions (69%) from 25 metastatic breast cancer patients additional EpCAMneg CTCs could be identified [range of 1-24 CTCs per sample] applying Trop2, CD49f, c-Met, CK8 and/or HA magnetic enrichment. EpCAMneg dual-positive (CKpos/CD45pos) cells could be traced in 28 out of 29 samples [range 1-480]. By single-cell array-based comparative genomic hybridization we were able to demonstrate the malignant nature of one EpCAMneg subpopulation. In conclusion, we established a novel enhanced CTC enrichment strategy to capture EpCAMneg CTCs from clinical blood samples by targeting various cell surface antigens with antibody mixtures and ECM components.

Trypanosoma cruzi Binds to Cytokeratin through Conserved Peptide Motifs Found in the Laminin-G-Like Domain of the gp85/Trans-sialidase Proteins

Background

Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi, is a disease that affects millions of people most of them living in South and Central Americas. There are few treatment options for individuals with Chagas' disease making it important to understand the molecular details of parasite infection, so novel therapeutic alternatives may be developed for these patients. Here, we investigate the interaction between host cell intermediate filament proteins and the T. cruzi gp85 glycoprotein superfamily with hundreds of members that have long been implicated in parasite cell invasion.

Methodology/Principal Findings

An in silico analysis was utilized to identify peptide motifs shared by the gp85 T. cruzi proteins and, using phage display, these selected peptide motifs were screened for their ability to bind to cells. One peptide, named TS9, showed significant cell binding capacity and was selected for further studies. Affinity chromatography, phage display and invasion assays revealed that peptide TS9 binds to cytokeratins and vimentin, and prevents T. cruzi cell infection. Interestingly, peptide TS9 and a previously identified binding site for intermediate filament proteins are disposed in an antiparallel β-sheet fold, present in a conserved laminin-G-like domain shared by all members of the family. Moreover, peptide TS9 overlaps with an immunodominant T cell epitope.

Conclusions/Significance

Taken together, the present study reinforces previous results from our group implicating the gp85 superfamily of glycoproteins and the intermediate filament proteins cytokeratin and vimentin in the parasite infection process. It also suggests an important role in parasite biology for the conserved laminin-G-like domain, present in all members of this large family of cell surface proteins.

Chagas' disease affects millions of people worldwide and is caused by a microorganism called Trypanosoma cruzi. Treatment options for patients with Chagas' disease is still limited to a small number of drugs, all of them very toxic with important side effects that can be debilitating for the health of patients. Understanding the molecular details of how T. cruzi infects humans is an important step toward the development of new drugs for this disease. As part of its life cycle, T. cruzi has to invade cells in order to replicate and produce new parasites. This is a complex event, which involves different proteins produced by both the parasite and the human host cells. Among them, there is a large family of highly polymorphic T. cruzi proteins important to guide the parasite to the target cells. Here we show that notwithstanding their differences, all members of this family share a small region comprised of nine amino acids that is important for cell recognition and infection by the parasite. Exploring these findings may provide researchers with new insights on how to prevent T. cruzi cell invasion and lead to novel therapeutic alternative for this debilitating disease.

Improved efficacy and reduced toxicity of doxorubicin encapsulated in sulfatide-containing nanoliposome in a glioma model

As a glycosphingolipid that can bind to several extracellular matrix proteins, sulfatide has the potential to become an effective targeting agent for tumors overexpressing tenasin-C in their microenvironment. To overcome the dose-limiting toxicity of doxorubicin (DOX), a sulfatide-containing nanoliposome (SCN) encapsulation approach was employed to improve treatment efficacy and reduce side effects of free DOX. This study analysed in vitro characteristics of sulfatide-containing nanoliposomal DOX (SCN-DOX) and assessed its cytotoxicity in vitro, as well as biodistribution, therapeutic efficacy, and systemic toxicity in a human glioblastoma U-118MG xenograft model. SCN-DOX was shown to achieve highest drug to lipid ratio (0.5∶1) and a remarkable in vitro stability. Moreover, DOX encapsulated in SCN was shown to be delivered into the nuclei and displayed prolonged retention over free DOX in U-118MG cells. This simple two-lipid SCN-DOX nanodrug has favourable pharmacokinetic attributes in terms of prolonged circulation time, reduced volume of distribution and enhanced bioavailability in healthy rats. As a result of the improved biodistribution, an enhanced treatment efficacy of SCN-DOX was found in glioma-bearing mice compared to the free drug. Finally, a reduction in the accumulation of DOX in the drug's principal toxicity organs achieved by SCN-DOX led to the diminished systemic toxicity as evident from the plasma biochemical analyses. Thus, SCN has the potential to be an effective and safer nano-carrier for targeted delivery of therapeutic agents to tumors with elevated expression of tenascin-C in their microenvironment.

The RNA/DNA-binding protein PSF relocates to cell membrane and contributes cells' sensitivity to antitumor drug, doxorubicin

Cell surface proteins play an important role in multidrug resistance (MDR). However, the identification involving chemoresistant features for cell surface proteins is a challenge. To identify potential cell membrane markers in hematologic cancer MDR, we used a cell- and antibody-based strategy of subtractive immunization coupled with cell surface comparative screening of leukemia cell lines from sensitive HL60 and resistant HL60/DOX cells. Fifty one antibodies that recognized the cell surface proteins expressed differently between the two cell lines were generated. One of them, the McAb-5D12 not only recognizes its antigen but also block its function. Comparative analysis of immunofluorescence, flow cytometry, and mass spectrum analysis validated that the membrane antigen of McAb-5D12 is a nucleoprotein-polypyrimidine tract binding protein associated splicing factor, PSF. Our results identified that PSF overexpressed on the membrane of sensitive cells compared with resistant cells and its relocation from the nuclear to the cell surface was common in hematological malignancy cell lines and marrow of leukemia patients. Furthermore, we found that cell surface PSF contributed to cell sensitivity by inhibiting cell proliferation. The results represent a novel and potentially useful biomarker for MDR prediction. The strategy enables the correlation of expression levels and functions of cell surface protein with some cell-drug response traits by using antibodies.

Cytokeratin 8 is an epithelial cell receptor for Pet, a cytotoxic serine protease autotransporter of Enterobacteriaceae

The group of proteins known as serine protease autotransporters of Enterobacteriaceae (SPATE) is a growing family of serine proteases secreted to the external milieu by the type V secretion system. Pet toxin and some other SPATE belong to the class 1 cytotoxic SPATE, which have comparable protease strength on fodrin. Pet is internalized and is directed to its intracellular substrate by retrograde transport. However, the epithelial cell receptor for Pet has yet to be identified. We show that Pet has affinity for the epithelial cell surface until the saturation of the binding sites at 100 nM Pet. Affinity column assays and matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) analysis identified a cytokeratin (CK8) which directly binds to Pet, and both proteins colocalized on the cell surface. Interestingly, CK8 is not present in kidney cell lines, which are not susceptible to Pet. Inhibition experiments by using anti-CK8 and ck8 small interfering RNA (siRNA) blocked the cytotoxic effect induced by Pet, while exogenous CK8 expression in kidney cells made them susceptible to Pet intoxication. Recombinant CK8 showed a Pet-binding pattern similar to that seen by using fixed cells. Remarkably, Pet colocalized with CK8 and clathrin at early times (receptor-mediated endocytosis), and subsequently, Pet colocalized with CK8 and Rab5b in the early endosomes. These data support the idea that CK8 is an important receptor for Pet on epithelial cells for starting its cytotoxic effects. These data suggest that therapeutics that block Pet-CK8 interaction may improve outcome of diseases caused by Pet-secreting Enterobacteriaceae such as enteroaggregative Escherichia coli.

Receptor-ligand binding is one mechanism by which cells sense and respond to external cues. Receptors may also be utilized by toxins to mediate their own internalization. Pet toxin is secreted by enteroaggregative Escherichia coli, an organism that causes persistent diarrhea in children, traveler’s diarrhea, and acute and persistent diarrhea in patients with HIV. Pet is a member of the family of serine protease autotransporters of Enterobacteriaceae (SPATE). SPATE in different pathogens are virulence factors, and Pet belongs to the class 1 cytotoxic SPATE, which have comparable protease strength on their biological substrate, fodrin (a cytoskeletal protein important for maintaining cell viability). To cleave fodrin, Pet enters the cells by clathrin-mediated endocytosis. This mechanism includes receptor-mediated endocytosis (a receptor-ligand complex triggers the endocytosis). We show that CK8 is an important receptor for Pet on epithelial cells and that it may be useful for identifying molecules that block the interaction of CK8 with Pet.

Cytokeratin 8-MHC class I interactions: a potential novel immune escape phenotype by a lymph node metastatic carcinoma cell line

Defective human leukocyte antigen (HLA) class I expression in malignant cells facilitates their escape from destruction by CD8(+) cytotoxic T lymphocytes. In this study, a post-translational mechanism of HLA class I abnormality that does not involve defects in the HLA subunits and antigen processing machinery components was identified and characterized. The marked HLA class I downregulation phenotype of a metastatic carcinoma cell line can be readily reversed by trypsin, suggesting a masking effect by serine protease-sensitive HLA class I-interacting factors. Co-immunoprecipitation, combined with LC-tandem mass spectrometry and immunoblotting identified these factors as cytokeratin (CK) 8 and its heterodimeric partners CK18 and CK19. Ectopic CK8/18 or CK8/19 expression in HEK293 cells resulted in surface CK8 expression with an HLA class I downregulation phenotype, while redirecting CK8/18 and CK8/19 to the endoplasmic reticulum (ER) had no such effect. This observation and the failure to constrain CK8/18 and CK8/19 membrane trafficking by an ER-Golgi transport inhibitor suggested an ER-independent route for CK8 access to HLA class I molecules. Monoclonal antibody mapping revealed a potential CK8 blockade of HLA class I-CD8 and -TCR contacts. These findings, along with the emerging role of cell surface CK8 in cancer metastasis, may imply a dual strategy for tumor cell survival in the host.

Three are better than one: plasminogen receptors as cancer theranostic targets

Activation of plasminogen on the cell surface initiates a cascade of protease activity with important implications for several physiological and pathological events. In particular, components of the plasminogen system participate in tumor growth, invasion and metastasis. Plasminogen receptors are in fact expressed on the cell surface of most tumors, and their expression frequently correlates with cancer diagnosis, survival and prognosis. Notably, they can trigger multiple specific immune responses in cancer patients, highlighting their role as tumor-associated antigens. In this review, three of the most characterized plasminogen receptors involved in tumorigenesis, namely Annexin 2 (ANX2), Cytokeratin 8 (CK8) and alpha-Enolase (ENOA), are analyzed to ascertain an overall view of their role in the most common cancers. This analysis emphasizes the possibility of delineating new personalized therapeutic strategies to counteract tumor growth and metastasis by targeting plasminogen receptors, as well as their potential application as cancer predictors.

Proteomic approaches for investigation of therapy resistance in cancer

Resistance to anticancer therapy is a major obstacle for successful management of patients in oncology. Although in the past, various biological mechanisms involved in therapy resistance, in particular multidrug resistance, have been identified, cancer patients did not really benefit. The mechanisms include the enhanced activity of drug extrusion pumps, modulation of cellular death pathways, alteration and repair of target molecules and various other mechanisms. Together they build a complex network mediating an individual therapy-resistant phenotype. The improved description of this multifactorial network should be useful for prediction of treatment response and would allow to design an individual-tailored therapy regiment. Proteome analyzing technologies appear as powerful tools for identifying new factors and protein expression profiles associated with anticancer therapy resistance. In the last years, the application of proteomic techniques identified multiple new factors or protein expression signatures in drug-resistant cell models and cancerous tissues. However, the functional role and the clinical impact of these findings are not yet clarified. So far, none of the proteomic data were useful for the development of improved diagnostic tests, for prediction of individual therapy response or for development of updated chemosensitizers. Here, the previous therapy resistance-related proteome data and future perspectives will be discussed.

Keratins: markers and modulators of liver disease

PURPOSE OF REVIEW

Keratins are a subgroup of intermediate filaments expressed in the epithelia. Keratins emerged as important tissue-protecting genes and keratin variants cause/predispose to development of more than 50 human disorders. Our review focuses on the importance of keratins in context of liver disease.

RECENT FINDINGS

K8/K18 variants are found in approximately 4% of white population and predispose to development and adverse outcome of multiple liver diseases. K8/K18 are major constituents of Mallory-Denk bodies, that is inclusions found in alcoholic and nonalcoholic steatohepatitis (NASH) and dysregulated keratin expression, K8 hyperphosphorylation, misfolding and crosslinking via transglutaminase 2 facilitate aggregate formation. Necrosis-generated and apoptosis-generated keratin serum fragments are emerging as important noninvasive markers of multiple liver diseases, particularly NASH. Keratins are established markers of tumor origin and in hepatocellular carcinoma, K19 expression is associated with poor prognosis.

SUMMARY

Keratins are established tumor markers and are widely used as noninvasive markers of liver injury. In addition, the data that have become available in recent years have greatly advanced our understanding of keratins as modifiers of liver disease development.

Disruption of cytokeratin-8 interaction with F508del-CFTR corrects its functional defect

We have previously reported an increased expression of cytokeratins 8/18 (K8/K18) in cells expressing the F508del mutation of cystic fibrosis transmembrane conductance regulator (CFTR). This is associated with increased colocalization of CFTR and K18 in the vicinity of the endoplasmic reticulum, although this is reversed by treating cells with curcumin, resulting in the rescue of F508del-CFTR. In the present work, we hypothesized that (i) the K8/K18 network may interact physically with CFTR, and that (ii) this interaction may modify CFTR function. CFTR was immunoprecipitated from HeLa cells transfected with either wild-type (WT) CFTR or F508del-CFTR. Precipitates were subjected to 2D-gel electrophoresis and differential spots identified by mass spectrometry. K8 and K18 were found significantly increased in F508del-CFTR precipitates. Using surface plasmon resonance, we demonstrate that K8, but not K18, binds directly and preferentially to the F508del over the WT human NBD1 (nucleotide-binding domain-1). In vivo K8 interaction with F508del-CFTR was confirmed by proximity ligation assay in HeLa cells and in primary cultures of human respiratory epithelial cells. Ablation of K8 expression by siRNA in F508del-expressing HeLa cells led to the recovery of CFTR-dependent iodide efflux. Moreover, F508del-expressing mice topically treated with K8-siRNA showed restored nasal potential difference, equivalent to that of WT mice. These results show that disruption of F508del-CFTR and K8 interaction leads to the correction of the F508del-CFTR processing defect, suggesting a novel potential therapeutic target in CF.

Dinosaurs and ancient civilizations: reflections on the treatment of cancer

Research efforts in the area of palaeopathology have been seen as an avenue to improve our understanding of the pathogenesis of cancer. Answers to questions of whether dinosaurs had cancer, or if cancer plagued ancient civilizations, have captured the imagination as well as the popular media. Evidence for dinosaurian cancer may indicate that cancer may have been with us from the dawn of time. Ancient recorded history suggests that past civilizations attempted to fight cancer with a variety of interventions. When contemplating the issue why a generalized cure for cancer has not been found, it might prove useful to reflect on the relatively limited time that this issue has been an agenda item of governmental attention as well as continued introduction of an every evolving myriad of manmade carcinogens relative to the total time cancer has been present on planet Earth. This article reflects on the history of cancer and the progress made following the initiation of the "era of cancer chemotherapy."

Keratins in health and cancer: more than mere epithelial cell markers

Keratins are the intermediate filament (IF)-forming proteins of epithelial cells. Since their initial characterization almost 30 years ago, the total number of mammalian keratins has increased to 54, including 28 type I and 26 type II keratins. Keratins are obligate heteropolymers and, similarly to other IFs, they contain a dimeric central α-helical rod domain that is flanked by non-helical head and tail domains. The 10-nm keratin filaments participate in the formation of a proteinaceous structural framework within the cellular cytoplasm and, as such, serve an important role in epithelial cell protection from mechanical and non-mechanical stressors, a property extensively substantiated by the discovery of human keratin mutations predisposing to tissue-specific injury and by studies in keratin knockout and transgenic mice. More recently, keratins have also been recognized as regulators of other cellular properties and functions, including apico-basal polarization, motility, cell size, protein synthesis and membrane traffic and signaling. In cancer, keratins are extensively used as diagnostic tumor markers, as epithelial malignancies largely maintain the specific keratin patterns associated with their respective cells of origin, and, in many occasions, full-length or cleaved keratin expression (or lack there of) in tumors and/or peripheral blood carries prognostic significance for cancer patients. Quite intriguingly, several studies have provided evidence for active keratin involvement in cancer cell invasion and metastasis, as well as in treatment responsiveness, and have set the foundation for further exploration of the role of keratins as multifunctional regulators of epithelial tumorigenesis.

Proteome-wide profiling of the MCF10AT breast cancer progression model

Background

Mapping the expression changes during breast cancer development should facilitate basic and translational research that will eventually improve our understanding and clinical management of cancer. However, most studies in this area are challenged by genetic and environmental heterogeneities associated with cancer.

Methodology/Principal Findings

We conducted proteomics of the MCF10AT breast cancer model, which comprises of 4 isogenic xenograft-derived human cell lines that mimic different stages of breast cancer progression, using iTRAQ-based tandem mass spectrometry. Of more than 1200 proteins detected, 98 proteins representing at least 20 molecular function groups including kinases, proteases, adhesion, calcium binding and cytoskeletal proteins were found to display significant expression changes across the MCF10AT model. The number of proteins that showed different expression levels increased as disease progressed from AT1k pre-neoplastic cells to low grade CA1h cancer cells and high grade cancer cells. Bioinformatics revealed that MCF10AT model of breast cancer progression is associated with a major re-programming in metabolism, one of the first identified biochemical hallmarks of tumor cells (the “Warburg effect”). Aberrant expression of 3 novel breast cancer-associated proteins namely AK1, ATOX1 and HIST1H2BM were subsequently validated via immunoblotting of the MCF10AT model and immunohistochemistry of progressive clinical breast cancer lesions.

Conclusion/Significance

The information generated by this study should serve as a useful reference for future basic and translational cancer research. Dysregulation of ATOX1, AK1 and HIST1HB2M could be detected as early as the pre-neoplastic stage. The findings have implications on early detection and stratification of patients for adjuvant therapy.

The War on Cancer rages on

In 1971, the "War on Cancer" was launched by the US government to cure cancer by the 200-year anniversary of the founding of the United States of America, 1976. This article briefly looks back at the progress that has been made in cancer research and compares progress made in other areas of human affliction. While progress has indeed been made, the battle continues to rage on.

Regulation of intestinal epithelial cells transcriptome by enteric glial cells: impact on intestinal epithelial barrier functions

BACKGROUND

Emerging evidences suggest that enteric glial cells (EGC), a major constituent of the enteric nervous system (ENS), are key regulators of intestinal epithelial barrier (IEB) functions. Indeed EGC inhibit intestinal epithelial cells (IEC) proliferation and increase IEB paracellular permeability. However, the role of EGC on other important barrier functions and the signalling pathways involved in their effects are currently unknown. To achieve this goal, we aimed at identifying the impact of EGC upon IEC transcriptome by performing microarray studies.

RESULTS

EGC induced significant changes in gene expression profiling of proliferating IEC after 24 hours of co-culture. 116 genes were identified as differentially expressed (70 up-regulated and 46 down-regulated) in IEC cultured with EGC compared to IEC cultured alone. By performing functional analysis of the 116 identified genes using Ingenuity Pathway Analysis, we showed that EGC induced a significant regulation of genes favoring both cell-to-cell and cell-to-matrix adhesion as well as cell differentiation. Consistently, functional studies showed that EGC induced a significant increase in cell adhesion. EGC also regulated genes involved in cell motility towards an enhancement of cell motility. In addition, EGC profoundly modulated expression of genes involved in cell proliferation and cell survival, although no clear functional trend could be identified. Finally, important genes involved in lipid and protein metabolism of epithelial cells were shown to be differentially regulated by EGC.

CONCLUSION

This study reinforces the emerging concept that EGC have major protective effects upon the IEB. EGC have a profound impact upon IEC transcriptome and induce a shift in IEC phenotype towards increased cell adhesion and cell differentiation. This concept needs to be further validated under both physiological and pathophysiological conditions.

Chemoresistance acquisition induces a global shift of expression of aniogenesis-associated genes and increased pro-angogenic activity in neuroblastoma cells

Background

Chemoresistance acquisition may influence cancer cell biology. Here, bioinformatics analysis of gene expression data was used to identify chemoresistance-associated changes in neuroblastoma biology.

Results

Bioinformatics analysis of gene expression data revealed that expression of angiogenesis-associated genes significantly differs between chemosensitive and chemoresistant neuroblastoma cells. A subsequent systematic analysis of a panel of 14 chemosensitive and chemoresistant neuroblastoma cell lines in vitro and in animal experiments indicated a consistent shift to a more pro-angiogenic phenotype in chemoresistant neuroblastoma cells. The molecular mechanims underlying increased pro-angiogenic activity of neuroblastoma cells are individual and differ between the investigated chemoresistant cell lines. Treatment of animals carrying doxorubicin-resistant neuroblastoma xenografts with doxorubicin, a cytotoxic drug known to exert anti-angiogenic activity, resulted in decreased tumour vessel formation and growth indicating chemoresistance-associated enhanced pro-angiogenic activity to be relevant for tumour progression and to represent a potential therapeutic target.

Conclusion

A bioinformatics approach allowed to identify a relevant chemoresistance-associated shift in neuroblastoma cell biology. The chemoresistance-associated enhanced pro-angiogenic activity observed in neuroblastoma cells is relevant for tumour progression and represents a potential therapeutic target.

Neoplasia: the second decade

This issue marks the end of the 10-year anniversary of Neoplasia where we have seen exciting growth in both number of submitted and published articles in Neoplasia. Neoplasia was first published in 1999. During the past 10 years, Neoplasia has dynamically adapted to the needs of the cancer research community as technologies have advanced. Neoplasia is currently providing access to articles through PubMed Central to continue to facilitate rapid broad-based dissemination of published findings to the scientific community through an Open Access model. This has in part helped Neoplasia to achieve an improved impact factor this past year, demonstrating that the manuscripts published by Neoplasia are of great interest to the overall cancer research community. This past year, Neoplasia received a record number of articles for review and has had a 21% increase in the number of published articles.