Normal Cell Surface Research Articles

PS059 Prevalence of Essential Hypertension and Assessment of Cardiac Risk in Pakistani Adults – The Reveal Study

We recently identified a peptide-peptoid hybrid, PPS1, which recognizes lipids that have an overall negative charge, such as phosphatidylserine (PS), phosphatidylglycerol (PG), phosphatidic acid (PA), and phosphatidylinositol (PI), but that does not bind to neutral lipids, such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), and sphingomyelin (SM). The simple dimeric version of PPS1, PPS1D1, displayed strong cytotoxicity to cancer cells over normal cells in vitro and tumor burden in vivo. In this study, we comprehensively characterized the direct binding and activity of PPS1 on PS, PG, and PA using liposome-based assays and lung cancer cell lines that express these negatively charged lipids. First, the fluorescence polarization (FP) binding studies of fluoresceinated-PPS1 (PPS1-FITC) to PS-, PG-, and PA-containing PC-liposomes showed that the binding of PPS1 to PC-liposomes increased as concentrations of these lipids increased. In terms of activity, PPS1D1 induced the release of calcein from large, unilamellar PC-liposomes containing 15–30% PS, PG, and PA. PPS1D1 had no activity when the liposomes were composed of 100% PC. This effect was higher at 30% lipids than 15%, and the EC50 for PG and PA were higher than that of PS, indicating that PPS1D1 is more specific towards PS. PPS1D1 binds to and induces significant cytotoxicity in lung cancer cell lines H1693, HCC95, and H1395, which express negatively charged lipids, but had no effect on normal HBEC30KT cells, which has mostly PC in the outer layer. In addition, a series of previously developed PPS1D1 derivatives, which retain or lose activity, were tested with these liposome-based assays, and the data were equivalent to previous observations. This study provides comprehensive binding and activity validations of a unique peptide-peptoid hybrid, PPS1, on negatively charged lipids PS, PA, and PG that are elevated on cancer cell surfaces relative to normal human cell surfaces.

A Germline Variant in the PANX1 Gene Has Reduced Channel Function and Is Associated with Multisystem Dysfunction

Pannexin1 (PANX1) is probably best understood as an ATP release channel involved in paracrine signaling. Given its ubiquitous expression, PANX1 pathogenic variants would be expected to lead to disorders involving multiple organ systems. Using whole exome sequencing, we discovered the first patient with a homozygous PANX1 variant (c.650G→A) resulting in an arginine to histidine substitution at position 217 (p.Arg217His). The 17-year-old female has intellectual disability, sensorineural hearing loss requiring bilateral cochlear implants, skeletal defects, including kyphoscoliosis, and primary ovarian failure. Her consanguineous parents are each heterozygous for this variant but are not affected by the multiorgan syndromes noted in the proband. Expression of the p.Arg217His mutant in HeLa, N2A, HEK293T, and Ad293 cells revealed normal PANX1 glycosylation and cell surface trafficking. Dye uptake, ATP release, and electrophysiological measurements revealed p.Arg217His to be a loss-of-function variant. Co-expression of the mutant with wild-type PANX1 suggested the mutant was not dominant-negative to PANX1 channel function. Collectively, we demonstrate a PANX1 missense change associated with human disease in the first report of a "PANX1-related disorder."

SLRP1ng Up Glucose: LRP1 Regulates Hepatic Insulin Responses

sLRP1ng Up Glucose: LRP1 Regulates Hepatic Insulin Responses

Boronic acid recognition based-gold nanoparticle-labeling strategy for the assay of sialic acid expression on cancer cell surface by inductively coupled plasma mass spectrometry.

Sialic acids are special sugars widely expressed at the termini of glycan chains on the cell surface, and their expression level on the cancer cell surface is much higher than on the normal cell surface. Herein, we reported an inductively coupled plasma mass spectrometry (ICP-MS) based method with elemental tags for the analysis of sialic acids on the cancer cell surface. The method is based on the selective recognition of sialic acids by biotinylated phenylboronic acid (biotin-APBA) at physiological pH and signal enhancement of gold nanoparticles (AuNPs) in ICP-MS when AuNPs were used as elemental tags labeled on biotin-APBA. A specificity test reveals that the proposed method has high specificity towards cancer cells. Taking HepG2 and MCF-7 cells as two model cancer cells, competitive experiments were performed to estimate the expression level of sialic acids on the cancer cell surface, and it was found that the average numbers of sialic acids expressed on the single MCF-7 and HepG2 cell surface were 7.0 × 10(9) and 5.4 × 10(9), respectively. With sialic acid as the biomarker for cancer cells, the method was further used for cell detection. The limits of detection in terms of cell number for HepG2 and MCF-7 cells were 120 and 64, respectively. And the relative standard deviations for nine replicate determinations of ca. 1000 HepG2 and MCF-7 cells were 9.6% and 8.9%, respectively. The linear ranges for HepG2 cells and MCF-7 cells were 300-10,000 and 170-11,000, respectively. The proposed approach is sensitive as well as selective for the analysis of sialic acids on the cancer cell surface, and is potentially applicable for the study of tumor malignancy and metastasis, which is helpful for biological research and clinical diagnostics.

IFITM3 (CD225) Links the B Cell Antigen CD19 to PI3K-AKT Signaling in Human ALL Cells

Background & Hypothesis: IFITM3 (Interferon-induced transmembrane protein 3) also known as CD225/Leu-13 was identified as interferon-inducible molecule in the context of viral infection. IFITM3 encodes a surface receptor, basally expressed on the plasma membrane, that is associated with known B cell co-receptors including CD19, CD81 and CD21. Recent immunotherapy approaches based on CD19-specific engineered chimeric antigen receptors (CART19) have achieved spectacular successes in eliminating pre-B ALL cells based on surface expression of CD19 (Grupp et al., 2013). However, in some cases, CART19 treatment was followed by ALL relapse developing from clones that lacked CD19 surface expression. Therefore, we studied factors that regulate CD19 surface expression on human pre-B ALL cells.Results: Studying IFITM3 mRNA levels in ALL cells at the time of diagnosis in clinical trials for childhood (COG P9906) and adult ALL (ECOG E2993), we found that higher than median expression levels of IFITM3 predicted shorter overall and relapse-free survival (P=0.014). In addition, patients with higher than median IFITM3 mRNA levels at the time of diagnosis were significantly more likely to experience ALL relapse and had a higher risk of a positive MRD status at the end of induction chemotherapy.To study the function of Ifitm3 in a model for human pre-B ALL, pre-B cells from Ifitm3-/- mice were transformed with BCR-ABL1. Strikingly, deletion of IFITM3 resulted in loss of CD19 expression on the surface of normal and leukemic pre-B cells. Besides loss of surface expression, loss of Ifitm3 also caused impaired phosphorylation of CD19-Y513, which mediates downstream activation of PI3K-AKT signaling in both B cell progenitors and pre-B ALL cells. These changes were paralleled by G0/1 cell cycle arrest (P<0.001), loss of colony formation capacity (P=0.0004) and activation of checkpoint molecules p53 and p21, reduction of BCL2 and BCLXL levels and increased propensity to apoptosis. Reconstitution of IFITM3 reversed these changes.Conversely, forced expression of IFITM3 in patient-derived pre-B ALL cells increased phosphorylation of CD19-Y513 together with downstream SRC, SYK, PI3K signaling. Although human IFITM1 has known as a component of B cell receptor complex, co-immunoprecipitation experiments revealed that the cytoplasmic tail of IFITM3 interacts with CD19, LYN, SYK, PI3K p110δ and AKT. In addition, agonistic antibodies against IFITM3/CD225 trigger CD19/PI3K-AKT signaling, which caused massively increased proliferation of pre-B ALL cells. Interestingly, agonistic antibodies against CD19 had no effect on the proliferation of pre-B ALL cells despite their ability to activate CD19/PI3K-AKT signaling. These findings indicate a specific role of IFITM3 in regulating CD19/PI3K-AKT signaling in malignant pre-B ALL cells compared to their normal pre-B cell counterparts.Conclusion: These findings identify novel role of the IFITM3 (CD255) surface receptor in regulating CD19 phosphorylation and CD19-Y513 mediated PI3K-AKT signaling in pre-B ALL cells. IFITM3 is a central mediator of CD19 surface trafficking and mediates the proliferation and survival signaling via PI3K-AKT in normal pre-B cells and various subtypes of human pre-B ALL. DisclosuresNo relevant conflicts of interest to declare.

Human papillomavirus capsids preferentially bind and infect tumor cells.

We previously determined that human papillomavirus (HPV) virus-like particles (VLPs) and pseudovirions (PsV) did not, respectively, bind to or infect intact epithelium of the cervicovaginal tract. However, they strongly bound heparan sulfate proteoglycans (HSPG) on the basement membrane of disrupted epithelium and infected the keratinocytes that subsequently entered the disrupted site. We here report that HPV capsids (VLP and PsV) have the same restricted tropism for a wide variety of disrupted epithelial and mesothelial tissues, whereas intact tissues remain resistant to binding. However, the HPV capsids directly bind and infect most tumor-derived cell lines in vitro and have analogous tumor-specific properties in vivo, after local or intravenous injection, using orthotopic models for human ovarian and lung cancer, respectively. The pseudovirions also specifically infected implanted primary human ovarian tumors. Heparin and ι-carrageenan blocked binding and infection of all tumor lines tested, implying that tumor cell binding is HSPG-dependent. A survey using a panel of modified heparins indicates that N-sulfation and, to a lesser degree, O-6 sulfation of the surface HSPG on the tumors are important for HPV binding. Therefore, it appears that tumor cells consistently evolve HSPG modification patterns that mimic the pattern normally found on the basement membrane but not on the apical surfaces of normal epithelial or mesothelial cells. Consequently, appropriately modified HPV VLPs and/or PsV could be useful reagents to detect and potentially treat a remarkably broad spectrum of cancers.

OP0010 Plasma concentrations of angiopoietin-1, angiopoietin-2, and Tie-2 in gastric cancer

Background Angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) have both been identified as ligands for Tie-2, a receptor expressed on endothelial cells. They play critical roles in angiogenesis, in concert with vascular endothelial growth factor (VEGF). Ang-1 binding to Tie-2 maintains and stabilises mature vessels by promoting interactions between endothelial cells and the surrounding extracellular matrix. However, Ang-2 shows context-dependent proangiogenic and antiangiogenic activities. Despite histopathological data reporting differences in the expression of members of the Ang family on the surface of various normal and tumour cells, data for these growth factors in plasma from cancer patients, including gastric cancer, remain scarce. The aims of the present study were to measure the plasma concentrations of Ang-1, Ang-2, and Tie-2 in gastric cancer patients, and to assess the correlation between the concentrations of these factors and the stage of the tumour. Methods The study cohort consisted of 50 patients (33 male, 17 female) with gastric cancer, ranging in age from 38 to 74 years (mean age 55.3 ± 12.4 years), and 50 sex- and age-matched healthy controls. Determinations of Ang-1, Ang-2, and Tie-2 were done with enzyme-linked immunosorbent assay (ELISA). Findings Concentrations of Ang-2 and Tie-2 were significantly higher in patients with gastric cancer than controls, while concentrations of Ang-1 were not significantly different between the groups. Concentrations of Ang-1, Ang-2, and Tie-2 were not significantly different in gastric cancer patients when analysed by different stages of disease. Interpretation Ang-2 and Tie-2 plasma concentrations might be useful tumour markers in gastric cancer.

G551D-CFTR needs more bound actin than wild-type CFTR to maintain its presence in plasma membranes.

Cystic Fibrosis is due to mutations in the CFTR gene. The missense mutation G551D (approx. 5% of cases) encodes a CFTR chloride channel with normal cell surface expression but with an altered chloride channel activity, leading to a severe phenotype. Our aim was to identify specific interacting proteins of G551D-CFTR which could explain the channel defect. Wild-type CFTR (Wt-CFTR) was co-immunoprecipitated from stably transfected HeLa cells and resolved by 2D gel electrophoresis. Among the detected spots, one was expressed at a high level. Mass Spectrometry revealed that it corresponded to actin which is known to be involved in the CFTR's channel function. To assess whether actin could be involved in the altered G551D-CFTR function, its basal expression was studied. Because actin expression was the same in wt- and in G551D-CFTR expressing cells, its interaction with both wt- and G551D-CFTR was studied by co-immunoprecipitation, and we found that a higher amount of actin was bound onto G551D-CFTR than onto Wt-CFTR. The role of actin upon wt- and G551D-CFTR function was further studied by patch-clamp experiments after cytochalasin D treatment of the cells. We found a decrease of the very weak currents in G551D-CFTR expressing cells. Because a higher amount of actin is bound onto G551D-CFTR than onto Wt-CFTR, it is likely to be not involved in the mutated CFTR's defect. Nevertheless, because actin is necessary to maintain the very weak global currents observed in G551D-CFTR expressing HeLa cells, we conclude that more actin is necessary to maintain G551D-CFTR in the plasma membrane than for Wt-CFTR.

The atypical N-glycosylation motif, Asn-Cys-Cys, in human GPR109A is required for normal cell surface expression and intracellular signaling.

Asparagine-linked glycosylation (N-glycosylation) is necessary for the proper folding of secreted and membrane proteins, including GPCRs. Thus, many GPCRs possess the N-glycosylation motif Asn-X-Ser/Thr at their N-termini and/or extracellular loops. We found that human GPR109A (hGPR109A) has an N-glycosylation site at Asn(17) in the N-terminal atypical motif, Asn(17)-Cys(18)-Cys(19). Why does hGPR109A require the atypical motif, rather than the typical sequence? Here we show that Asn(17)-Cys(18)-Cys(19) sequence of hGPR109A possesses 2 biologic roles. First, Asn(17)-X-Cys(19) contributed to hGPR109A N-glycosylation by acting as an atypical motif. This modification is required for the normal surface expression of hGPR109A, as evidenced by the reduced surface expression of the nonglycosylated mutants, hGPR109A/N17A, and the finding that hGPR109A/C19S and hGPR109A/C19T, which are N-glycosylated at Asn(17), exhibited expression similar to the wild-type receptor. Second, the X-Cys(18)-Cys(19) dicysteine is indispensable for hGPR109A function. Substitution of Cys(18) or Cys(19) residue to Ala impaired Gi-mediated signaling via hGPR109A. We propose the disulfide bond formations of these residues with other Cys existed in the extracellular loops for the proper folding. Together, these results suggest that the atypical motif Asn(17)-Cys(18)-Cys(19) is crucial for the normal surface trafficking and function of hGPR109A.

IFITM3 (CD225) Regulates CD19 Surface Expression and CD19-Mediated Activation of PI3K Signaling in Pre-B Acute Lymphoblastic Leukemia Cells

Background & Hypothesis:IFITM3 (Interferon-induced transmembrane protein 3) also known as CD225/Leu-13 was identified as interferon-inducible molecule in the context of viral infection. IFITM3 encodes a surface receptor, basally expressed on the plasma membrane, that is associated with known B cell co-receptors including CD19, CD81 and CD21 on mouse and human B cells. However, besides its interaction with CD19, specific functions of Ifitm3 in normal B cells development and, potentially leukemogenesis, are not known. Recent approaches based on CD19-specific chimeric antigen receptors (CAR) have achieved spectacular successes in eliminating pre-B ALL cells based on surface expression of CD19 (e.g. Grupp et al., N Engl J Med 2013). However, in some cases, CD19 CAR treatment was followed by ALL relapse developing from a clone that lacked CD19 surface expression. Therefore, we studied factors that can potentially regulate CD19 surface on normal and leukemic pre-B cells.Results: Studying IFITM3 mRNA levels in ALL cells at the time of diagnosis in clinical trials for childhood (COG P9906) and adult ALL (ECOG E2993), we found that higher than median expression levels of IFITM3 predicted shorter overall and relapse-free survival (P=0.014). In addition, patients with higher than median IFITM3 mRNA levels at the time of diagnosis were significantly more likely to experience ALL relapse and had a higher risk of a positive MRD status at the end of induction chemotherapy. To study the function of Ifitm3 in a model for human pre-B ALL, pre-B cells from Ifitm3-/- mice were transformed with BCR-ABL1. Strikingly, deletion of IFITM3 resulted in near-complete loss of CD19 expression on the surface of normal and leukemic pre-B cells. Besides loss of surface expression, loss of Ifitm3 also caused impaired phosphorylation of CD19-Y513, which mediates downstream activation of PI3K-AKT signaling in both B cell progenitors and pre-B ALL cells. Reconstitution of IFITM3 in patient-derived pre-B ALL cells rescued both CD19 expression and increased phosphorylation of CD19-Y513 together with downstream SRC, SYK, PI3K signaling. Co-immunoprecipitation experiments revealed that the cytoplasmic tail of IFITM3 interacts with CD19, LYN, SYK, PI3K p110δ and AKT, pointing to a central role of IFITM3 in regulating CD19/PI3K-AKT signaling in pre-B cells and pre-B ALL.Deletion of Ifitm3 also resulted in significant cell cycle arrest in the G0/G1 phase (P<0.001) and increased protein levels of p53 and p21 compared to wild-type pre-B ALL cells. Moreover, treatment with low dose adriamycin (25 ng ml-1) for induction of modest DNA damage significantly induced cellular senescence in Ifitm3-/- but not wild-type pre-B ALL cells. Consistent with Ifitm3-mediated proliferative defects of Ph+ ALL cells, Ifitm3-/- Ph+ ALL cells exhibited reduced self-renewal capacity (P=0.0004) decreased colony in colony forming assay compared to wild-type cells. Furthermore, Ifitm3 deficient B cell progenitors also showed significant inhibition of proliferation with inhibition of phosphorylation of Stat5Y694and c-Myc expression.4-hydroxytamoxifen (4-OHT)-inducible activation of CD19 rescued proliferative defects in Ifitm3 deficient B cell progenitors with release from G0/G1 cell cycle arrest associated with upregulation of phosphorylation of Stat5 Y694 and c-Myc expression. In addition, we found that CD19 positively regulates the surface expression of IL7R in B cell progenitors. Interestingly, CD19low population in Ifitm3 deficient B cell progenitors showed lower surface expression of IL7R compared to CD19high population. In contrast to B cell progenitors, forced expression of CD19 did not increase the proliferation of wild-type Ph+ ALL cells. Surprisingly, upregulation of CD19 induced apoptosis in Ifitm3-deficient Ph+ ALL cells with significant inhibition of BCR-ABL1 activity, phosphorylation of Stat5Y694and Bcl2 expression.Conclusion: These findings identify novel role of IFITM3 in regulating CD19 surface expression and CD19-Y513 mediated PI3K-AKT signaling in pre-B cells and pre-B ALL. Preliminary experiment showed that agonistic antibodies against IFITM3/CD225 increased CD19/PI3K-AKT signaling and proliferation in pre-B ALL cells and future studies will elucidate whether blocking antibodies (e.g. decoy Fc-fusion molecules) will have useful effects in targeting CD19/PI3K-AKT signaling in human pre-B ALL. DisclosuresNo relevant conflicts of interest to declare.

The Predominant Activation of Alternative Signaling Pathways Explains the Differential Propensity of Different c-Mpl Gain-of-Function Mutations to Promote Myeloproliferative Malignancies

Thrombopoiesis is tightly regulated by the binding of thrombopoietin (THPO) to its receptor c-Mpl that leads to the clearance of THPO from the plasma thus establishing a negative feedback loop. Several mutations in the c-Mpl receptor gene have been linked to a gain-of-function resulting in thrombocytosis. We focused on a comparison of gain-of-function mutation in the extracellular part of the c-Mpl receptor, where ligand binding and receptor dimerization occur, with the S505N, W515K and W515L mutations in the transmembrane and juxtamembrane region, respectively. Interestingly, the latter mutations are known to also promote myeloproliferative malignancies and AML, whereas the P106L mutation causes hereditary thrombocytosis without a known predisposition to hematologic malignancies.We have now performed functional analyses of these gain-of-function mutations to address the question of how the different propensity to induce malignancy can be explained. We first analyzed the post-translational processing of the normal and the P106L mutated receptor in comparison to the receptors carrying the S505N, W515K and W515L mutations in transfected HeLa and BA/F3 cells. The normal and the S505N, W515K and W515L mutated c-Mpl receptors were properly glycosylated during their transport through the Golgi apparatus, whereas the P106L mutated receptor did not enter the Golgi and was not fully glycosylated. The plasma membrane expression, assayed by confocal microscopy and FACS, of the S515N, W515K and W515L mutated receptors was comparable to the normal receptor, whereas the P106L mutated receptor was not detectable on the cell surface. Functional analyses of the THPO/c-Mpl signaling pathways in THPO stimulated c-Mpl transfected BA/F3 cells showed activation of the ERK1/2 pathway in all mutants but only weaker activation of the PI3K/m-TOR and Stat3/5 signaling pathways for the P106L mutant. By contrast, cells transfected with the normal receptor gene and the S505N, W515K and W515L c-Mpl mutants showed predominant up-regulation of the PI3K/m-TOR and Stat3/5 pathways.These results show that (1) the activation of c-Mpl by THPO does not absolutely require surface expression of the receptor (2) different c-Mpl gain-of-function mutations activate separable downstream pathways and (3) the predominant activation of the PI3K/m-TOR and Stat3/5 pathways correlates with the propensity to induce hematopoietic malignancy.Further, it is interesting to note that the c-Mpl P106L gain-of-function mutant is known to cause 10 to 20-fold elevated thrombopoietin (THPO) plasma levels in patients and is shown here not to be properly glycosylated and transported to the cell surface. By contrast, patients with the other gain-of-function mutations analyzed here show normal or even reduced THPO plasma concentrations and normal post-translational processing and cell surface expression.In conclusion, we propose that c-Mpl gain-of-function mutations exert their effect by predominantly activating either the PI3K/m-TOR and Stat3/5 or the ERK signaling pathways and that the predominant activation of PI3K/m-TOR and Stat3/5 correlates with the propensity to induce malignancy. Furthermore, THPO clearance and maintenance of the negative feedback loop regulating THPO plasma levels, but not signaling activity of the c-Mpl receptor necessarily require proper glycosylation, intracellular trafficking and cell surface expression. DisclosuresNo relevant conflicts of interest to declare.

Specific MUC1 Splice Variants Are Correlated With Tumor Progression in Esophageal Cancer

Mucin 1 (MUC1) is a complex glycoprotein expressed on the apical surface of normal glandular epithelial cells. It plays a role in a number of biologic processes, and its overexpression is associated with various malignancies. A growing body of literature suggests that MUC1 is a potential diagnostic and therapeutic marker. Increasing numbers of variants are being identified for the MUC1 gene, but their role in carcinogenesis is unclear. Alternative splicing and a specific region on a variable number of tandem repeats are characteristic features of MUC1. However, the underlying mechanisms, overall prevalence, and the function of various MUC1 isoforms are not well characterized. In the present study, mRNA expression of nine variants of the MUC1 gene (A-D, X-Z, REP, SEC) was evaluated in normal and tumor tissues obtained from 50 patients with esophageal squamous cell carcinoma (ESCC). Associations between expression of various isoforms of MUC1 and important clinicopathologic factors were studied. Specific MUC1 splice variants (i.e., MUC1/C, D, and Z) are correlated with tumor progression in ESCC, whereas MUC1/B-previously suggested as a "normal" variant in some other cancers-has protective effects and is associated with more favorable tumor behavior and better prognosis. Specific isoforms of ESCC are associated with prognosis. Further characterization of different isoforms of MUC1 and their biologic effects is needed to explore their diagnostic and prognostic potential in clinical practice.

Altered Agonist Sensitivity of a Mutant V2 Receptor Suggests a Novel Therapeutic Strategy for Nephrogenic Diabetes Insipidus

Loss-of-function mutations of the type 2 vasopressin receptor (V2R) in kidney can lead to nephrogenic diabetes insipidus (NDI). We studied a previously described, but uncharacterized, mutation of the V2R (N321K missense mutation) of a patient with NDI. The properties of the mutant receptor were evaluated. We constructed a highly sensitive Epac-based bioluminescence resonance energy transfer biosensor to perform real-time cAMP measurements after agonist stimulation of transiently transfected HEK293 cells with V2Rs. β-Arrestin binding of the activated receptors was examined with luciferase-tagged β-arrestin and mVenus-tagged V2Rs using the bioluminescence resonance energy transfer technique. Cell surface expression levels of hemagglutinin-tagged receptors were determined with flow cytometry using anti-hemagglutinin-Alexa 488 antibodies. Cellular localization examinations were implemented with fluorescent tagged receptors visualized with confocal laser scanning microscopy. The effect of various vasopressin analogs on the type 1 vasopressin receptor (V1R) was tested on mouse arteries by wire myography. The N321K mutant V2R showed normal cell surface expression, but the potency of arginine vasopressin for cAMP generation was low, whereas the clinically used desmopressin was not efficient. The β-arrestin binding and internalization properties of the mutant receptor were also different than those for the wild type. The function of the mutant receptor can be rescued with administration of the V2R agonist Val(4)-desmopressin, which had no detectable side effects on V1R in the effective cAMP generating concentrations. Based on these findings we propose a therapeutic strategy for patients with NDI carrying the N321K mutation, as our in vivo experiments suggest that Val(4)-desmopressin could rescue the function of the N321K-V2R without significant side effects on the V1R.

Mechanisms of antitumor and immune-enhancing activities of MUC1/sec, a secreted form of mucin-1

Mucin 1 (MUC1) is a polymorphic type 1 transmembrane protein found on the apical surface of normal cells lining the lumen of ducts and glands. Mucins are thought to provide mucosal protection from environmental exposures and carcinogens. An altered form of the MUC1 glycoprotein, which is hypoglycosylated, is expressed in several types of human cancers. In our laboratory, we have found that transfection of a murine mammary tumor cell line with a human secreted isoform of MUC1 rendered these DA-3 cells (DA-3/sec) incapable of growing in intact BALB/c mice. In contrast, implantation of DA-3 cells transfected with the human transmembrane isoform of MUC1 (DA-3/TM), resulted in tumor formation and ultimately death of the animals, similar to the DA-3 parental line. Importantly, inoculation of the DA-3/sec cells in immunodeficient nude mice resulted in tumor formation, indicating that the MUC1/sec molecule's antitumor activity is immunologically controlled. In this review, we summarize the studies we have performed to elucidate possible mechanisms for the immune-mediated antitumor effect of MUC1/sec and/or a unique peptide present in this mucin. Understanding these mechanisms may provide new immunotherapeutic approaches that could be used to target different types of cancer.

Abstract 049: Functional Characterization of KCNQ1 Channel Subunit With an A590T Mutation

Background: KCNQ1 encodes the alpha subunit of the voltage-gated K + channel that mediates the cardiac slow delayed rectifier K + current (I Ks ). A mutation, A590T, in KCNQ1 was incidentally identified in a 40 years old female. She had a mild QTc prolongation in electrocardiogram but has never experienced any cardiac events. A590 is located in the C-terminal domain forming a coiled-coil structure, which has been suggested as a pivotal component for subunit tetramerization and channel trafficking to the cell surface. The previously reported mutations around A590 result in markedly reduced cell surface expression and loss of functional channel. We, for the first time, examined whether and how the A590T mutation affects the I Ks channel function. Methods: To assess the trafficking and channel function of KCNQ1(A590T) mutant subunit, we performed immunostaining, immunoblotting, and voltage-clamp measurements in HEK-293T cells transfected with wild-type or the A590T mutant KCNQ1 or their mixture (WT, A590T, and A590T/WT cells, respectively). Results: The density of a depolarization-activated current in the A590T cells was smaller than that in the WT cells. The threshold, half-maximal activation, and saturating voltages of the depolarization-activated current in the A590T cells were more positive than those in the WT cells. The immunoreactivity against KCNQ1 subunit on the cell surface in the A590T cells is lower than in WT cells. The A590T/WT cells had a similar density of the depolarization-activated current and a similar level of immunoreactivity against the channel subunit to the WT cells. Furthermore, the immunoblotting detected subunit oligomers in the membrane fraction of the A590T cells while their densities were lower than those of the WT cells. Conclusion: Although the A590T mutant subunit can form oligomers for itself, this subunit is not efficiently trafficked to the cell surface without the aid of the WT subunit. Thus, homozygous inheritance of the mutant KCNQ1 might be pathogenic. By contrast, the cells expressing both the mutant and wild-type KCNQ1 subunit had normal I Ks and cell surface expression, indicating that the heterozygous inheritance of the mutant KCNQ1 might not cause severe cardiac diseases.

P-0042 - Pharmacokinetics of Erlotinib and Its Main Metabolite Osi420 in Advanced Pancreatic Cancer Patients When Combined with Escalating Doses of Capecitabine

Background: Erlotinib selectively inhibits the intracellular phosphorylation of human EGFR-Type 1, expressed on the cell surface of normal and cancer cells. In Europe, it is approved for the treatment of locally advanced/metastatic pancreatic cancer. We investigated the pharmacokinetics of erlotinib in a phase I trial of a combination regimen with capecitabine (CCB) and bevacizumab (BVC) against inoperable pancreatic cancer.

What role can bispecific antibodies play in cancer targeting? A hypothesis

Monoclonal antibodies (mAbs) are currently among the best remedies in the treatment of cancer disorders. Almost 12 anti-cancer therapeutic mAbs have been approved for clinical applications. Although mAbs have been found to target specific antigens, numerous impediments are emerged in cancer therapy by mAbs because of expression of a low level of the same antigens on the surface of normal cells. To exterminate tumor cells specifically, the current paper puts forward a novel strategy to target cancer cells more selectively by bispecific monoclonal antibody (bsmAb), which has an affinity against the tumor-specific antigens. Translocations in genes and chromosomes are known triggers for the development of human cancers. The mutations in gene profile could create novel tumor-specific proteins and receptors which could be detected using bsmAbs.

Abstract 454: ADAM proteases shed UL-16-binding protein 2 in human lung cancer cell lines.

Abstract NKG2D is an activating receptor that is expressed in immune effector cells, and the ligands for which are expressed in transformed cells. NKG2D-NKG2D ligand system might play an essential role in the tumor immunity of host cells. We have previously reported that a member of NKG2D ligand family, UL-16-binding protein 2 (ULBP2), is predominantly expressed on the surface of lung cancer cells, and is shed and solubilized into the sera of the lung cancer patients. In addition, we showed that the soluble form of ULBP2 (sULBP2) aggravates the cytotoxicity of host immune effector cells. Therefore, shedding of ULBP2 from the surface of cancer cells might be a critical component of the immune escape mechanisms employed in lung cancer. In this study, we investigated the mechanism of ULBP2 shedding from the cell surfaces in human lung cancer cell lines. First, we compared the amount of ULBP2 expression on the surface of normal cells and that in the culture medium of various lung cancer cell lines. We observed a significant correlation among non-small-cell lung cancer (NSCLC) cell lines (r=0.835, P&amp;lt;0.01), but not small-cell lung cancer (SCLC) cell lines (r=-0.154). These observations suggest that the ULBP2 shed in the culture medium is proportional to the level of its cell surface expression by NSCLC cell lines, but this does not apply in case of SCLC cell lines. Next, we examined the expression levels and activation status of A Disintegrin and Metalloproteinase (ADAM) families in the cell lines as candidates that execute the shedding of ULBP2 proteases. We found that ADAM17 was abundantly expressed and activated in NSCLC cell lines, but not in SCLC cell lines. Finally, we directly confirmed the shedding of ULBP2 by the enzyme ADAM metallopeptidase domain 17 (ADAM17) by using gene silencing and overexpression of ADAM17 in NSCLC and SCLC cell lines, respectively. Our data indicated that the expression of ADAM17 is a crucial determining factor in the heterogeneous shedding of ULBP2, which is observed in the lung cancer cell lines. ULBP2 shedding, and the resultant sULBP2 formation, is one of the determining factors of host tumor cell immunity; hence, developing a form of intervention to act on the shedding step by using ADAM protease inhibitors would be a promising and novel immunomodulatory therapy. Citation Format: Kosuke Yamaguchi, Hiroki Hikumi, Shinji Matsumaga, Miyako Takata, Naoki Kinoshita, Kiyoshi Hashimoto, Masaki Nakamoto, Jun Kurai, Masanari Watanabe, Akira Yamasaki, Tadashi Igishi, Naoto Burioka, Eiji Shimizu. ADAM proteases shed UL-16-binding protein 2 in human lung cancer cell lines. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 454. doi:10.1158/1538-7445.AM2013-454

Homozygosity for killer immunoglobin-like receptor haplotype A predicts complete molecular response to treatment with tyrosine kinase inhibitors in chronic myeloid leukemia patients

Several recent reports suggest a possible role for killer immunoglobulin-like receptors (KIR) in the onset of chronic myeloid leukemia (CML) and response to therapy with tyrosine kinase inhibitors (TKIs). To explore this hypothesis, we studied KIRs and their human leukocyte antigen class I ligands in 59 consecutive patients with chronic-phase CML (mean age, 53 years; range, 23-81 years) and a group of 121 healthy control participants belonging to the same ethnic group as the patients. The 2-year cumulative incidence of complete molecular response, obtained after a median of 27 months (range, 4-52 months), was 51.2%. An increased frequency of the activating receptor KIR2DS1 (pm = 0.05) and a reduced frequency of the KIR-ligand combination KIR2DS2/2DL2 absent/C1 present (pm = 0.001) were significantly associated with CML. Moreover, KIR repertoires in patients appeared to influence response to TKI therapy. Homozygosity for KIR haplotype A (pm = 0.01), a decreased frequency of the inhibitory KIR gene KIR2DL2 (pm = 0.02), and low numbers of inhibitory KIR genes (pm = 0.05) were all significantly associated with achievement of complete molecular remission. These data suggest that a decrease in properly stimulated and activated NK cells might contribute to the occurrence of CML and indicate homozygosity for KIR haplotype A as a promising immunogenetic marker of complete molecular response that could help clinicians decide whether to withdraw treatment in patients with CML.

Detection of carbohydrates on the surface of cancer and normal cells by topography and recognition imaging

Galactose was detected and localized on the surface of cancer and normal cells by topography and recognition imaging at the single molecular level. There are more galactoses on cancer cells than on normal cells. The stability of galactose-lectin on cancer cells is much lower than that on normal cells.