Mesothelin, Stereocilin, and Otoancorin are predicted to have superhelical structures with ARM-type repeats

Metastasis of cervical cancer indicated by elevation of serum CA125 produced by mediastinal lymph nodes: a case report

BACKGROUND

In patient assessment for recurrence of neoplasia, a biomarker that shows an elevated serum value before the first treatment is a candidate for follow-up examination. The biomarker squamous cell carcinoma antigen is usually utilized for follow-up of squamous cell cancer of the cervix.

CASE PRESENTATION

We herein report a 30-year-old Japanese woman of postoperative metastasis of cervical squamous cell cancer to the mediastinal and supraclavicular lymph nodes as indicated by an elevated serum cancer antigen 125 concentration and not by the squamous cell carcinoma antigen value. After chemoradiotherapy and chemotherapy, the serum cancer antigen 125 concentration decreased to a normal value. Squamous cell carcinoma antigen was found to be distributed in both the squamous cell cancer tissue of the cervix and the supraclavicular lymph node metastatic tissue. By contrast, cancer antigen 125 was distributed in the supraclavicular lymph node metastatic tissue but not in the original squamous cell cancer tissue of the cervix.

CONCLUSION

In this case, metastasis of cervical cancer to the mediastinal and supraclavicular lymph nodes was shown by the biomarker cancer antigen 125, which was not present in the original neoplasia.

Isolation, characterization, and cloning of thermostable pullulanase from Geobacillus stearothermophilus ADM-11

This study aimed to identify thermo-stable pullulanase-producing bacteria in soil samples of potato fields and food-producing companies. Pullulan agar medium was used to screen 17 bacterial strains, which were incubated at 65 °C. The isolate with the maximum activity (375U/ml) was selected and recognized as Geobacillus stearothermophilus ADM-11 by morphological, biochemical characterization, and 16S rRNA gene sequencing. The pullulanase production required optimum pH of 7 and temperature of 75 °C, respectively. The electrophoresis of purified pullulanase on SDS-polyacrylamide gel revealed 83 kDa of a molecular weight that is active at 70 °C and pH 7.0. It was also stable at 90 °C but its activity was decreased by 10 % at 100 °C. The action of pullulanase was increased and stabilized by Ca+2 among the metal ions. Beta and gamma-cyclodextrins inhibited enzyme activity while ethylenediaminetetraacetate (EDTA) and phenylmethylsulfonyl fluoride (PMSF) have no significant effect on pullulanase activity. A full-length pullulanase gene was amplified from G. stearothermophilus ADM-11 using genomic DNA 2.1 kb of PCR product which was then purified and ligated in the cloning vector pTZ57R using the TA cloning technique. Colony PCR confirmed cloning on the positive clones after the pullulanase gene had been ligated and subjected to restriction digestion. It revealed 74 % similarity with the reported pullulanase gene from Geobacillus sp. 44C. The thermostability of pullulanase and its ability to degrade raw pullulan may therefore have wide-scale applications in starch processing, the detergent business, and new biotechnological applications.

Biology of Mesothelin and Clinical Implications: A Review of Existing Literature

Since its discovery in 1992, mesothelin (MSLN) has generated significant interest as a therapeutic target. A number of characteristics make it ideal for this purpose. First, it is not expressed on the parenchyma of any vital organs. Second, it is differentially expressed on a number of cancer types that have relatively poor prognosis and lack effective systemic options. Third, it is expressed on the cell membrane making it accessible to large molecule targeted therapies. However, unlike other drug targets that have been exploited for therapeutic benefit, the precise function of MSLN, why it is expressed in certain cancers, and its biological role have not been clearly elucidated. Here the existing literature on the cellular function and expression patterns of MSLN across tumor types is reviewed in order to gain further understanding of this intriguing molecule. In doing so, we conclude that there remains significant ambiguity surrounding its function and role in cellular and tumor biology. Furthermore, the expression of MSLN and its relation of prognosis seems to depend on the type of tumor. Finally, the unified mechanism by which MSLN acts as a protein that conveys tumor aggressiveness remains elusive. What is clear is that there is much yet to be discovered in this realm and doing so may have large implications for treatment of otherwise lethal malignancies.

RNAseq profiling of blood from patients with coronary artery disease: Signature of a T cell imbalance

Background

Cardiovascular disease had a global prevalence of 523 million cases and 18.6 million deaths in 2019. The current standard for diagnosing coronary artery disease (CAD) is coronary angiography either by invasive catheterization (ICA) or computed tomography (CTA). Prior studies employed single-molecule, amplification-independent RNA sequencing of whole blood to identify an RNA signature in patients with angiographically confirmed CAD. The present studies employed Illumina RNAseq and network co-expression analysis to identify systematic changes underlying CAD.

Methods

Whole blood RNA was depleted of ribosomal RNA (rRNA) and analyzed by Illumina total RNA sequencing (RNAseq) to identify transcripts associated with CAD in 177 patients presenting for elective invasive coronary catheterization. The resulting transcript counts were compared between groups to identify differentially expressed genes (DEGs) and to identify patterns of changes through whole genome co-expression network analysis (WGCNA).

Results

The correlation between Illumina amplified RNAseq and the prior SeqLL unamplified RNAseq was quite strong (r = 0.87), but there was only 9 % overlap in the DEGs identified. Consistent with the prior RNAseq, the majority (93 %) of DEGs were down-regulated ~1.7-fold in patients with moderate to severe CAD (>20 % stenosis). DEGs were predominantly related to T cells, consistent with known reductions in Tregs in CAD. Network analysis did not identify pre-existing modules with a strong association with CAD, but patterns of T cell dysregulation were evident. DEGs were enriched for transcripts associated with ciliary and synaptic transcripts, consistent with changes in the immune synapse of developing T cells.

Conclusions

These studies confirm and extend a novel mRNA signature of a Treg-like defect in CAD. The pattern of changes is consistent with stress-related changes in the maturation of T and Treg cells, possibly due to changes in the immune synapse.

Effects of Two Natural Bisbenzylisoquinolines, Curine and Guattegaumerine, Extracted from Isolona hexaloba on Rhodamine Efflux by Abcb1b from Rat Glycocholic-Acid-Resistant Hepatocarcinoma Cells

To develop new therapeutic molecules, it is essential to understand the biological effects and targets of clinically relevant compounds. In this article, we describe the extraction and characterization of two alkaloids from the roots of Isolona hexaloba—curine and guattegaumerine. The effect of these alkaloids on the multidrug efflux pump ABCB1 (MDR1/P-Glycoprotein) and their antiproliferative properties were studied. Compared to verapamil, a widely used inhibitor of P-gp, curine and guattegaumerine were found to be weak inhibitors of MDR1/P-Glycoprotein. The highest inhibition of efflux produced by verapamil disappeared in the presence of curine or guattegaumerine as competitors, and the most pronounced effect was achieved with curine. Altogether, this work has provided new insights into the biological effects of these alkaloids on the rat Mdr1b P-gp efflux mechanism and would be beneficial in the design of potent P-gp inhibitors.

Mesothelin: An Immunotherapeutic Target beyond Solid Tumors

Simple Summary

This review summarizes the current knowledge on mesothelin’s function, its role in cancer, and opportunities for immunotherapeutic targeting of mesothelin. Immunotherapies including monoclonal antibodies, antibody–drug conjugates, chimeric antigen receptor T and NK-cells, targeted alpha therapies, and bispecific T cell engaging molecules are reviewed. We show future directions for mesothelin targeting in hematological malignancies, including acute myeloid leukemia.

Abstract

Modern targeted cancer therapies rely on the overexpression of tumor associated antigens with very little to no expression in normal cell types. Mesothelin is a glycosylphosphatidylinositol-anchored cell surface protein that has been identified in many different tumor types, including lung adenocarcinomas, ovarian carcinomas, and most recently in hematological malignancies, including acute myeloid leukemia (AML). Although the function of mesothelin is widely unknown, interactions with MUC16/CA125 indicate that mesothelin plays a role in the regulation of proliferation, growth, and adhesion signaling. Most research on mesothelin currently focuses on utilizing mesothelin to design targeted cancer therapies such as monoclonal antibodies, antibody–drug conjugates, chimeric antigen receptor T and NK cells, bispecific T cell engaging molecules, and targeted alpha therapies, amongst others. Both in vitro and in vivo studies using different immunotherapeutic modalities in mesothelin-positive AML models highlight the potential impact of this approach as a unique opportunity to treat hard-to-cure AML.

Investigating binding dynamics of trans resveratrol to HSA for an efficient displacement of aflatoxin B1 using spectroscopy and molecular simulation

Resveratrol is a polyphenol belonging to the class stilbenes. The active and stable form of resveratrol is trans-resveratrol. This polyphenol is bestowed with numerous biological properties. Aflatoxin B₁ is a hepato-carcinogen and mutagen that is produced by Aspergillus species. In this study, the interaction of trans-resveratrol with HSA followed by competitive dislodging of AFB₁ from HSA by trans-resveratrol has been investigated using spectroscopic studies. The UV-absorption studies revealed ground state complex formation between HSA and trans-resveratrol. Trans-resveratrol binds strongly to HSA with the binding constant of ~ 10⁷ M⁻¹ to a single binding site (n = 1.58), at 298.15 K. The Stern–Volmer quenching constant was calculated as 7.83 × 10⁴ M⁻¹ at 298.15 K, suggesting strong fluorescence quenching ability of trans-resveratrol. Site markers displacement assay projected subdomain IIA as the binding site of trans-resveratrol to HSA. The molecular docking approach envisages the amino acid residues involved in the formation of the binding pocket. As confirmed from the site marker displacement assays, both trans-resveratrol and AFB₁ binds to HSA in the same binding site, subdomain IIA. The study explores the ability of trans-resveratrol to displace AFB₁ from the HSA-AFB₁ complex, thereby affecting the toxicokinetic behavior of AFB₁ associated with AFB₁ exposure.

Unveiling the binding mode of perfluorooctanoic acid to human serum albumin

Perfluorooctanoic acid (PFOA) is a toxic compound that is absorbed and distributed throughout the body by noncovalent binding to serum proteins such as human serum albumin (hSA). Though the interaction between PFOA and hSA has been already assessed using various analytical techniques, a high resolution and detailed analysis of the binding mode is still lacking. We report here the crystal structure of hSA in complex with PFOA and a medium-chain saturated fatty acid (FA). A total of eight distinct binding sites, four occupied by PFOAs and four by FAs, have been identified. In solution binding studies confirmed the 4:1 PFOA-hSA stoichiometry and revealed the presence of one high and three low affinity binding sites. Competition experiments with known hSA-binding drugs allowed locating the high affinity binding site in sub-domain IIIA. The elucidation of the molecular basis of the interaction between PFOA and hSA might provide not only a better assessment of the absorption and elimination mechanisms of these compounds in vivo but also have implications for the development of novel molecular receptors for diagnostic and biotechnological applications.

Insights Into the Role of Mesothelin as a Diagnostic and Therapeutic Target in Ovarian Carcinoma

Ovarian malignancies remain the leading cause of death in female gynecological tumors. More than 70% of patients are diagnosed with advanced stage with extensive metastatic lesions in abdominal cavity due to lack of symptoms in early stage and sensitive diagnostic approaches. Mesothelin (MSLN), a glycosylphosphatidylinositol-anchored membrane glycoprotein, participates in cell adhesion, tumor progression, metastasis, and drug resistance. Despite this, the mechanism is still poorly understood. The differential expression pattern of MSLN in normal and cancer tissues makes it a promising target for diagnosis and therapeutic applications. Several clinical trials are underway to evaluate the safety and efficacy of MSLN-targeted drugs, including CAR T cells, immunotoxin, antibody-drug conjugates, and vaccine. This review is aimed to briefly discuss the characteristics of MSLN and the latest progress in MSLN targeting therapies.

From Malignant Progression to Therapeutic Targeting: Current Insights of Mesothelin in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), accounting for 90% of all pancreatic tumors, is a highly devastating disease with poor prognosis and rising incidence. The lack of available specific diagnostics tests and the limited treatment opportunities contribute to this pejorative issue. Over the last 10 years, a growing interest pointing towards mesothelin (MSLN) as a promising PDAC-associated antigen has emerged. The limited expression of MSLN in normal tissues (peritoneum, pleura and pericardium) and its overexpression in 80 to 90% of PDAC make it an attractive candidate for therapeutic management of PDAC patients. Moreover, its role in malignant progression related to its involvement in tumor cell proliferation and resistance to chemotherapy has highlighted the relevance of its targeting. Hence, several clinical trials are investigating anti-MSLN efficacy in PDAC. In this review, we provide a general overview of the different roles sustained by MSLN during PDAC progression. Finally, we also summarize the different MSLN-targeted therapies that are currently tested in the clinic.

Hair-Bundle Links: Genetics as the Gateway to Function

Up to five distinct cell-surface specializations interconnect the stereocilia and the kinocilium of the mature hair bundle in some species: kinocilial links, tip links, top connectors, shaft connectors, and ankle links. In developing hair bundles, transient lateral links are prominent. Mutations in genes encoding proteins associated with these links cause Usher deafness/blindness syndrome or nonsyndromic (isolated) forms of human hereditary deafness, and mice with constitutive or conditional alleles of these genes have provided considerable insight into the molecular composition and function of the different links. We describe the structure of these links and review evidence showing CDH23 and PCDH15 are components of the tip, kinocilial, and transient-lateral links, that stereocilin (STRC) and protein tyrosine phosphatase (PTPRQ) are associated with top and shaft connectors, respectively, and that USH2A and ADGRV1 are associated with the ankle links. Whereas tip links are required for mechanoelectrical transduction, all link proteins play key roles in the normal development and/or the maintenance of hair bundle structure and function. Recent crystallographic and single-particle analyses of PCDH15 and CDH23 provide insight as to how the structure of tip link may contribute to the elastic element predicted to lie in series with the hair cell's mechanoelectrical transducer channel.

Mesothelin Enhances Tumor Vascularity in Newly Forming Pancreatic Peritoneal Metastases

Over 90% of pancreatic ductal adenocarcinomas (PDAC) express mesothelin (MSLN). Overexpression or knockdown of MSLN has been implicated in PDAC aggressiveness. This activity has been ascribed to MSLN-induced activation of MAPK or NF-κB signaling pathways and to interaction of MSLN with its only known binding partner, MUC16. Here, we used CRISPR/Cas9 gene editing to delete MSLN from PDAC, then restored expression of wild-type (WT) or Y318A mutant MSLN by viral transduction. We found that MSLN KO cells grew in culture and as subcutaneous tumors in mouse xenografts at the same rate as WT cells but formed intraperitoneal metastases poorly. Complementation with WT MSLN restored intraperitoneal growth, whereas complementation with Y318A mutant MSLN, which does not bind MUC16, was ineffective at enhancing growth in both MUC16(+) and MUC16(-) models. Restoration of WT MSLN did enhance growth but did not affect cell-to-cell binding, cell viability in suspension or signaling pathways previously identified as contributing to the protumorigenic effect of MSLN. RNA deep sequencing of tumor cells identified no changes in transcriptional profile that could explain the observed phenotype. Furthermore, no histologic changes in tumor cell proliferation or morphology were observed in mature tumors. Examination of nascent MSLN KO tumors revealed decreased microvascular density as intraperitoneal tumors were forming, followed by decreased proliferation, which resolved by 2 weeks postimplantation. These data support a model whereby MSLN expression by tumor cells contributes to metastatic colonization. IMPLICATIONS: MSLN confers a growth advantage to tumor cells during colonization of peritoneal metastasis. Therapeutic blockade of MSLN might limit peritoneal spread.

Mesothelin as a biomarker for targeted therapy

CAR-T cell therapy targeting CD19 has achieved remarkable success in the treatment of B cell malignancies, while various solid malignancies are still refractory for lack of suitable target. In recent years, a large number of studies have sought to find suitable targets with low “on target, off tumor” concern for the treatment of solid tumors. Mesothelin (MSLN), a tumor-associated antigen broadly overexpressed on various malignant tumor cells, while its expression is generally limited to normal mesothelial cells, is an attractive candidate for targeted therapy. Strategies targeting MSLN, including antibody-based drugs, vaccines and CAR-T therapies, have been assessed in a large number of preclinical investigations and clinical trials. In particular, the development of CAR-T therapy has shown great promise as a treatment for various types of cancers. The safety, efficacy, doses, and pharmacokinetics of relevant strategies have been evaluated in many clinical trials. This review is intended to provide a brief overview of the characteristics of mesothelin and the development of strategies targeting MSLN for solid tumors. Further, we discussed the challenges and proposed potential strategies to improve the efficacy of MSLN targeted immunotherapy.

MUC16 suppresses human and murine innate immune responses

OBJECTIVE

MUC16, the mucin that contains the CA125 epitopes, suppresses the cytolytic responses of human NK cells and inhibits the efficacy of therapeutic antibodies. Here, we provide further evidence of the regulatory role of MUC16 on human and murine NK cells and macrophages.

METHODS

Target cell cytolysis and doublet formation assays were performed to assess effects of MUC16 on human NK cells. The effect of MUC16 on ovarian tumor growth was determined in a mouse model by monitoring survival and ascites formation. Innate immune cells from spleens and peritoneal cavities of mice were isolated and stimulated in vitro with anti-CD40 antibody, lipopolysaccharide and IFN-γ and their ability to cytolyse MUC16 expressing and non-expressing cells was determined.

RESULTS

We confirm that MUC16 inhibits cytolysis by human NK cells as well as the formation of NK-tumor conjugates. Mice implanted with MUC16-knockdown OVCAR-3 show >2-fold increase in survival compared to controls. Murine NK cells and macrophages are more efficient at lysing MUC16-knockdown cells. In vitro cytotoxicity assays with NK cells and macrophages isolated from mice stimulated with anti-CD40 antibody showed 2-3-fold increased activity against the MUC16-knockdown cells as compared to matching target cells expressing this mucin. Finally, knockdown of MUC16 increased the susceptibility of cancer cells to ADCC by murine splenocytes.

CONCLUSIONS

For the first time, we demonstrate the immunoregulatory effects of MUC16 on murine NK cells and macrophages. Our study implies that the immunoregulatory role of MUC16 on murine NK cells and macrophages should be considered when examining the biology of MUC16 in mouse models.

The Impact of Mesothelin in the Ovarian Cancer Tumor Microenvironment

Ovarian cancer is the deadliest gynecological disease among U.S. women. Poor 5-year survival rates (<30%) are due to presentation of most women at diagnosis with advanced stage disease with widely disseminated intraperitoneal metastasis. However, when diagnosed before metastatic propagation the overall 5-year survival rate is >90%. Metastasizing tumor cells grow rapidly and aggressively attach to the mesothelium of all organs within the peritoneal cavity, including the parietal peritoneum and the omentum, producing secondary lesions. In this review, the involvement of mesothelin (MSLN) in the tumor microenvironment is discussed. MSLN, a 40kDa glycoprotein that is overexpressed in many cancers including ovarian and mesotheliomas is suggested to play a role in cell survival, proliferation, tumor progression, and adherence. However, the biological function of MSLN is not fully understood as MSLN knockout mice do not present with an abnormal phenotype. Conversely, MSLN has been shown to bind to the ovarian cancer antigen, CA-125, and thought to play a role in the peritoneal diffusion of ovarian tumor cells. Although the cancer-specific expression of MSLN makes it a potential therapeutic target, more studies are needed to validate the role of MSLN in tumor metastasis.

Structure, Function, and Development of the Tectorial Membrane: An Extracellular Matrix Essential for Hearing

The tectorial membrane is an extracellular matrix that lies over the apical surface of the auditory epithelia in the inner ears of reptiles, birds, and mammals. Recent studies have shown it is composed of a small set of proteins, some of which are only produced at high levels in the ear and many of which are the products of genes that, when mutated, cause nonsyndromic forms of human hereditary deafness. Quite how the proteins of the tectorial membrane are assembled within the lumen of the inner ear to form a structure that is precisely regulated in its size and physical properties along the length of a tonotopically organized hearing organ is a question that remains to be fully answered. In this brief review we will summarize what is known thus far about the structure, protein composition, and function of the tectorial membrane in birds and mammals, describe how the tectorial membrane develops, and discuss major events that have occurred during the evolution of this extracellular matrix.

Molecular Imaging of Mesothelin-Expressing Ovarian Cancer with a Human and Mouse Cross-Reactive Nanobody

Mesothelin is an epithelial marker highly expressed at the cell surface of cancer cells from diverse origins, including ovarian and pancreatic adenocarcinomas and mesotheliomas. Previously, we identified and characterized an antimesothelin nanobody (NbG3a) for in vitro diagnostic applications. The main goal of this research was to establish the potential of NbG3a as a molecular imaging agent. Site-specific biotinylated NbG3a (bNbG3a) was bound to streptavidin-conjugated reagents for in vitro and in vivo assays. Initially, we performed microscale thermophoresis to determine the binding affinity between bNbG3a and human ( K_d = 46 ± 8 nM) or mouse ( K_d = 4.8 ± 0.4 nM) mesothelin protein. The human and mouse cross-reactivity was confirmed by in vivo optical imaging using bNbG3a bound to fluorescent streptavidin. We also localized the binding site of nNbG3a on human mesothelin using overlapping peptide scan. NbG3a recognized an epitope within residues 21-65 of the mature membrane bound form of human mesothelin, which is part of the N-terminal region of mesothelin that is important for interactions between mesothelin on peritoneal cells and CA125 on tumor cells. Next, the bNbG3a in vivo half-life after intravenous injection in healthy mice was estimated by ELISA assay to be 5.3 ± 1.3 min. In tumor-bearing animals, fluorescent bNbG3a accumulated in a subcutaneous ovarian xenograft (A1847) and in two syngeneic, orthotopic ovarian tumors (intraovary and intraperitoneal ID8) within an hour of intravenous injection that peaked by 4 h and persisted up to 48 h. MRI analysis of bNbG3a-targeted streptavidin-labeled iron oxides showed that the MRI signal intensity decreased 1 h after injection for a subcutaneous xenograft model of ovarian cancer for bNbG3a-labeled iron oxides compared to unlabeled iron oxides. The signal intensity differences continued up to the final time point at 24 h post injection. Finally, in vivo immunofluorescence 24 or 48 h after bNbG3a intravenous injection showed bNbG3a diffuse distribution of both xenograft and syngeneic ovarian tumors, with local areas of high concentration throughout A1847 human tumor. The data support the use of NbG3a for continued preclinical development and translation to human applications for cancers that overexpress mesothelin.

Mesothelin Immunotherapy for Cancer: Ready for Prime Time?

Mesothelin is a tumor antigen that is highly expressed in many human cancers, including malignant mesothelioma and pancreatic, ovarian, and lung adenocarcinomas. It is an attractive target for cancer immunotherapy because its normal expression is limited to mesothelial cells, which are dispensable. Several antibody-based therapeutic agents as well as vaccine and T-cell therapies directed at mesothelin are undergoing clinical evaluation. These include antimesothelin immunotoxins (SS1P, RG7787/LMB-100), chimeric antimesothelin antibody (amatuximab), mesothelin-directed antibody drug conjugates (anetumab ravtansine, DMOT4039A, BMS-986148), live attenuated Listeria monocytogenes-expressing mesothelin (CRS-207, JNJ-64041757), and chimeric antigen receptor T-cell therapies. Two antimesothelin agents are currently in multicenter clinical registration trials for malignant mesothelioma: amatuximab in the first-line setting and anetumab ravtansine as second-line therapy. Phase II randomized clinical trials of CRS-207 as a boosting agent and in combination with immune checkpoint inhibition for pancreatic cancer are nearing completion. These ongoing studies will define the utility of mesothelin immunotherapy for treating cancer.

Shape similarity comparison of protein CPK models based on improved L₁-medial skeleton

We propose a new method to analyse the similarity of protein CPK models. In the proposed method we first construct the skeleton of protein models by an improved L1-medial skeleton extraction. The skeleton information is then used to form a local radius descriptor. Finally, the shape similarity of protein models is compared by using the local radius descriptor based on the absolute degree of grey incidence. Experimental results show that the improved L1-medial skeleton of protein models can describe the shapes of the protein models well. The local descriptor based on the skeleton combined with the absolute degree of grey incidence shows satisfactory performance for comparing the shape similarity of protein CPK models.

MUC16 (CA125): tumor biomarker to cancer therapy, a work in progress

Over three decades have passed since the first report on the expression of CA125 by ovarian tumors. Since that time our understanding of ovarian cancer biology has changed significantly to the point that these tumors are now classified based on molecular phenotype and not purely on histological attributes. However, CA125 continues to be, with the recent exception of HE4, the only clinically reliable diagnostic marker for ovarian cancer. Many large-scale clinical trials have been conducted or are underway to determine potential use of serum CA125 levels as a screening modality or to distinguish between benign and malignant pelvic masses. CA125 is a peptide epitope of a 3-5 million Da mucin, MUC16. Here we provide an in-depth review of the literature to highlight the importance of CA125 as a prognostic and diagnostic marker for ovarian cancer. We focus on the increasing body of literature describing the biological role of MUC16 in the progression and metastasis of ovarian tumors. Finally, we consider previous and on-going efforts to develop therapeutic approaches to eradicate ovarian tumors by targeting MUC16. Even though CA125 is a crucial marker for ovarian cancer, the exact structural definition of this antigen continues to be elusive. The importance of MUC16/CA125 in the diagnosis, progression and therapy of ovarian cancer warrants the need for in-depth research on the biochemistry and biology of this mucin. A renewed focus on MUC16 is likely to culminate in novel and more efficient strategies for the detection and treatment of ovarian cancer.

The role of mesothelin in tumor progression and targeted therapy

Mesothelin, a glycosylphosphatidylinositol (GPI) anchored cell surface protein, is a potential target for antibody-based cancer therapy due to its high expression in mesothelioma, ovarian cancer, pancreatic cancer, cholangiocarcinoma and other cancers. The SS1P immunotoxin and MORAb-009 (amatuximab), a chimeric monoclonal antibody, are currently being evaluated in clinical trials. In this review, we discuss the role of mesothelin in cancer progression and provide new insights into mesothelin-targeted cancer therapy. Recent studies highlight three mechanisms by which mesothelin plays a role in cancer progression. First, mesothelin may aid in the peritoneal implantation and metastasis of tumors through its interaction with mucin MUC16 (also known as CA125). Second, mesothelin may promote cancer cell survival and proliferation via the NF-κB signaling pathway. Finally, mesothelin expression promotes resistance to certain chemotherapy drugs such as TNF-α, paclitaxel, and a combination of platinum and cyclophosphamide. However, its cancerspecific expression makes mesothelin a potential target for monoclonal antibody therapy. New human monoclonal antibodies targeting mesothelin have been isolated by phage display technology and may provide opportunities for novel cancer therapy.

The composition and role of cross links in mechanoelectrical transduction in vertebrate sensory hair cells

The key components of acousticolateralis systems (lateral line, hearing and balance) are sensory hair cells. At their apex, these cells have a bundle of specialized cellular protrusions, which are modified actin-containing microvilli, connected together by extracellular filaments called cross links. Stereociliary deflections open nonselective cation channels allowing ions from the extracellular environment into the cell, a process called mechanoelectrical transduction. This produces a receptor potential that causes the release of the excitatory neurotransmitter glutamate onto the terminals of the sensory nerve fibres, which connect to the cell base, causing nerve signals to be sent to the brain. Identification of the cellular mechanisms underlying mechanoelectrical transduction and of some of the proteins involved has been assisted by research into the genetics of deafness, molecular biology and mechanical measurements of function. It is thought that one type of cross link, the tip link, is composed of cadherin 23 and protocadherin 15, and gates the transduction channel when the bundle is deflected. Another type of link, called lateral (or horizontal) links, maintains optimal bundle cohesion and stiffness for transduction. This Commentary summarizes the information currently available about the structure, function and composition of the links and how they might be relevant to human hearing impairment.

A mouse model for human deafness DFNB22 reveals that hearing impairment is due to a loss of inner hair cell stimulation

The gene causative for the human nonsyndromic recessive form of deafness DFNB22 encodes otoancorin, a 120-kDa inner ear-specific protein that is expressed on the surface of the spiral limbus in the cochlea. Gene targeting in ES cells was used to create an EGFP knock-in, otoancorin KO (Otoa(EGFP/EGFP)) mouse. In the Otoa(EGFP/EGFP) mouse, the tectorial membrane (TM), a ribbon-like strip of ECM that is normally anchored by one edge to the spiral limbus and lies over the organ of Corti, retains its general form, and remains in close proximity to the organ of Corti, but is detached from the limbal surface. Measurements of cochlear microphonic potentials, distortion product otoacoustic emissions, and basilar membrane motion indicate that the TM remains functionally attached to the electromotile, sensorimotor outer hair cells of the organ of Corti, and that the amplification and frequency tuning of the basilar membrane responses to sounds are almost normal. The compound action potential masker tuning curves, a measure of the tuning of the sensory inner hair cells, are also sharply tuned, but the thresholds of the compound action potentials, a measure of inner hair cell sensitivity, are significantly elevated. These results indicate that the hearing loss in patients with Otoa mutations is caused by a defect in inner hair cell stimulation, and reveal the limbal attachment of the TM plays a critical role in this process.

Characterization of crystals of an antibody-recognition fragment of the cancer differentiation antigen mesothelin in complex with the therapeutic antibody MORAb-009

The mesothelin-specific monoclonal antibody MORAb-009 is capable of blocking the binding of mesothelin to CA-125 and displays promising anticancer potential. It is currently undergoing clinical trials. In order to understand the basis of the interaction between MORAb-009 and mesothelin at atomic resolution, both the Fab fragment of MORAb-009 and the complex between the Fab and an N-terminal fragment of mesothelin (residues 7-64) were crystallized. The crystals of the Fab diffracted X-rays to 1.75 Å resolution and had the symmetry of space group P4(1)2(1)2, with unit-cell parameters a = b = 140.6, c = 282.0 Å. The crystals of the mesothelin-Fab complex diffracted to 2.6 Å resolution and belonged to the hexagonal space group P6(4), with unit-cell parameters a = b = 146.2, c = 80.9 Å. Structural analyses of these molecules are in progress.

Recognition of mesothelin by the therapeutic antibody MORAb-009: structural and mechanistic insights

Mesothelin is a tumor differentiation antigen that is highly expressed in many epithelial cancers, with limited expression in normal human tissues. Binding of mesothelin on normal mesothelial cells lining the pleura or peritoneum to the tumor-associated cancer antigen 125 (CA-125) can lead to heterotypic cell adhesion and tumor metastasis within the pleural and peritoneal cavities. This binding can be prevented by MORAb-009, a humanized monoclonal antibody against mesothelin currently under clinical trials. We show here that MORAb-009 recognizes a non-linear epitope that is contained in the first 64-residue fragment of the mesothelin. We further demonstrate that the recognition is independent of glycosylation state of the protein but sensitive to the loss of a disulfide bond linking residues Cys-7 and Cys-31. The crystal structure of the complex between the mesothelin N-terminal fragment and Fab of MORAb-009 at 2.6 Å resolution reveals an epitope encompassing multiple secondary structural elements of the mesothelin, including residues from helix α1, the loops linking helices α1 and α2, and between helices α4 and α5. The mesothelin fragment has a compact, right-handed superhelix structure consisting of five short helices and connecting loops. A residue essential for complex formation has been identified as Phe-22, which projects its side chain into a hydrophobic niche formed on the antibody recognition surface upon antigen-antibody contact. The overlapping binding footprints of both the monoclonal antibody and the cancer antigen CA-125 explains the therapeutic effect and provides a basis for further antibody improvement.

Binding of bezafibrate to human serum albumin: insight into the non-covalent interaction of an emerging contaminant with biomacromolecules

In recent years, bezafibrate (BZF) has been frequently detected in environmental media. In order to reveal the toxicity of such an emerging pollutant, its interaction with human serum albumin (HSA) was studied by fluorescence spectrometry, circular dichroism, and equilibrium dialysis. Fluorescence data showed that the fluorescence quenching of HSA by BZF resulted from the formation of HSA-BZF complex. The binding constants were determined to be 3.33 × 10³, 2.84 × 10³ M⁻¹ at 298 and 309.5 K, respectively. The thermodynamic determination indicated that the hydrophobic and electrostatic interaction were the dominant binding force. The conformational investigation showed that the presence of BZF increased the α-helix content of HSA and induced the slight unfolding of the polypeptides of protein. Finally, the equilibrium dialysis showed that 0.56 mM BZF decreased the binding of vitamin B₂ to HSA by 29%.

Inactivation of the MSLNL gene encoding mesothelin-like protein during African great ape evolution

Loss of gene function is implicated in the emergence of novel phenotypes during organism evolution. Here, we report the inactivation of the MSLNL gene encoding mesothelin-like protein in African great ape evolution. Human MSLNL has a nonsense mutation in exon 10 and two polymorphic mutations: a frameshift in exon 3 and a nonsense codon in exon 8. The gorilla gene also shows multiple deleterious mutations, including a premature stop codon, a deletion, and a splice site mutation. Molecular evolutionary analysis indicated relaxed selection pressure on MSLNL in African great ape lineages, which suggested that MSLNL might have become inactivated before the divergence of human, chimpanzee and gorilla. The mouse Mslnl gene is highly expressed in olfactory epithelium and moderately expressed in several other tissues. We propose that the loss of MSLNL may be associated with the evolution of the olfactory system in African great apes including human.

Divalent counterions tether membrane-bound carbohydrates to promote the cohesion of auditory hair bundles

The cell membranes in the hair bundle of an auditory hair cell confront a difficult task as the bundle oscillates in response to sound: for efficient mechanotransduction, all the component stereocilia of the hair bundle must move essentially in unison, shearing at their tips yet maintaining contact without membrane fusion. One mechanism by which this cohesion might occur is counterion-mediated attachment between glycan components of apposed stereociliary membranes. Using capillary electrophoresis, we showed that the stereociliary glycocalyx acts as a negatively charged polymer brush. We found by force-sensing photomicrometry that the stereocilia formed elastic connections with one another to various degrees depending on the surrounding ionic environment and the presence of N-linked sugars. Mg(2+) was a more potent mediator of attachment than was Ca(2+). The forces between stereocilia produced chaotic stick-slip behavior. These results indicate that counterion-mediated interactions in the glycocalyx contribute to the stereociliary coherence that is essential for hearing.

Structural analysis of the cancer-specific promoter in mesothelin and in other genes overexpressed in cancers

Mesothelin (MSLN) may be the most "dramatic" of the tumor markers, being strongly overexpressed in nearly one-third of human malignancies. The biochemical cause is unclear. We previously ascribed this cancer-specific overexpression to an element, Canscript, residing around 50 bp 5' of the transcription start site in cancer (Hucl, T., Brody, J. R., Gallmeier, E., Iacobuzio-Donahue, C. A., Farrance, I. K., and Kern, S. E. (2007) Cancer Res. 67, 9055-9065). Herein, we found a Canscript promoter activity elevated over 100-fold in cancer cells. In addition to a highly conserved TEAD1 (TEA domain family member 1)-binding MCAT motif, nucleotide substitution revealed the consensus core sequence (WCYCCACCC) of an SP1-like motif in Canscript. The unknown transcription factor binding to the SP1-like motif may hold the key for the cancer specificity of Canscript. SP1, GLI1, and RUNX1, -2, and -3 appeared unlikely to be the direct transcription factors acting at the SP1-like motif, but KLF6 had some features of such a candidate. YAP1, a TEAD1-binding protein, appeared necessary, but not sufficient, for Canscript activity; knockdown of YAP1 by small interfering RNAs greatly reduced MSLN levels in MSLN-overexpressing cells, but overexpressing YAP1 in MSLN-negative cells did not induce MSLN expression. Cansript-like sequences were found in other genes up-regulated in pancreatic cancer; reporters driven by the sequences from FXYD3, MUC1, and TIMP1 had activities more than 2 times that of the control. This suggested that the cause of MSLN overexpression might also contribute mechanistically to the overexpression of other tumor markers.

Sliding adhesion confers coherent motion to hair cell stereocilia and parallel gating to transduction channels

When the tip of a hair bundle is deflected by a sensory stimulus, the stereocilia pivot as a unit, producing a shearing displacement between adjacent tips. It is not clear how stereocilia can stick together laterally but still shear. We used dissociated hair cells from the bullfrog saccule and high-speed video imaging to characterize this sliding adhesion. Movement of individual stereocilia was proportional to height, indicating that stereocilia pivot at their basal insertion points. All stereocilia moved by approximately the same angular deflection, and the same motion was observed at 1, 20, and 700 Hz stimulus frequency. Motions were consistent with a geometric model that assumes the stiffness of lateral links holding stereocilia together is >1000 times the pivot stiffness of stereocilia and that these links can slide in the plane of the membrane-in essence, that stereocilia shear without separation. The same motion was observed when bundles were moved perpendicular to the tip links, or when tip links, ankle links, and shaft connectors were cut, ruling out these links as the basis for sliding adhesion. Stereocilia rootlets are angled toward the center of the bundle, tending to push stereocilia tips together for small deflections. However, stereocilia remained cohesive for deflections of up to +/-35 degrees, ruling out rootlet prestressing as the basis for sliding adhesion. These observations suggest that horizontal top connectors mediate a sliding adhesion. They also indicate that all transduction channels of a hair cell are mechanically in parallel, an arrangement that may enhance amplification in the inner ear.

Peritoneal repairing cells: a type of bone marrow derived progenitor cells involved in mesothelial regeneration

The peritoneal mesothelium exhibits a high regenerative ability. Peritoneal regeneration is concomitant with the appearance, in the coelomic cavity, of a free-floating population of cells whose origin and functions are still under discussion. We have isolated and characterized this cell population and we have studied the process of mesothelial regeneration through flow cytometry and confocal microscopy in a murine model lethally irradiated and reconstituted with GFP-expressing bone marrow cells. In unoperated control mice, most free cells positive for mesothelin, a mesothelial marker, are green fluorescent protein (GFP). However, 24 hrs after peritoneal damage, free mesothelin⁺/ GFP⁺ cells appear in peritoneal lavages. Cultured lavage peritoneal cells show colocalization of GFP with mesothelial (mesothelin, cytokeratin) and fibroblastic markers. Immunohistochemical staining of the peritoneal wall also revealed colocalization of GFP with mesothelial markers and with procollagen-1 and smooth muscle α-actin. This was observed in the injured area as well as in the surrounding not-injured peritoneal surfaces. These cells, which we herein call peritoneal repairing cells (PRC), are very abundant 1 week after surgery covering both the damaged peritoneal wall and the surrounding uninjured area. However, they become very scarce 1 month later, when the mesothelium has completely healed. We suggest that PRC constitute a type of monocyte-derived cells, closely related with the tissue-repairing cells known as ‘fibrocytes’ and specifically involved in peritoneal reparation. Thus, our results constitute a synthesis of the different scenarios hitherto proposed about peritoneal regeneration, particularly recruitment of circulating progenitor cells and adhesion of free-floating coelomic cells.