Anti-myc Antibody Research Articles

A quantitative comparison of antibodies against epitope tags for immunofluorescence detection.

Epitope tags recognized by specific antibodies have been widely used over the last few decades, notably to localize tagged proteins within cells by immunofluorescence. The diversity of tags and antibodies usually prevents a side-by-side comparison of the efficiency with which each antibody recognizes its cognate tag. We expressed chimeric proteins, each composed of an invariant domain (IL2Ra) associated with a specific epitope tag. Double immunofluorescence allowed us to quantify in parallel the reference signal generated by the anti-IL2Ra antibody and the signal generated by the anti-epitope tag antibody. Since all antibodies used in this study were recombinant antibodies fused to the same mouse Fc domain, the generated signals were directly comparable. Three groups of tags/antibodies were revealed: 'good' antibodies generated high signals even when used at a low concentration (50 ng·mL-1 ), 'fair' antibodies generated a high signal only at high concentrations (5000 ng·mL-1 ), and 'mediocre' antibodies generated positive but weak signals. Except for an anti-myc antibody, similar results were obtained when cells were fixed in paraformaldehyde or methanol. These results provide a side-by-side quantitative evaluation of different tag/antibody pairs. This information will be useful to optimize the choice of epitope tags and to choose optimal antibodies.

Novel Peptide-Based Plectin-1 CAR T-Cells Target Specifically Pancreatic Cancer Cells

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is one of the most devastating cancers, and therapies to treat this malignancy have not evolved rapidly to fulfill the need of affected patients. PDAC, like many solid malignancies, is considered a “cold immunological tumor” where the lack of targetable tumor-associated antigens has hampered the development of successful immunotherapies. Despite newer treatment approaches, PDAC patients with advanced disease have a dismal prognosis. Therefore, there is an urgent need to develop new therapies. Plectin-1 is a high molecular weight protein (∼500 kDa) that participates in cytoskeleton network organization linking intermediate filaments to microtubules and microfilaments. Plectin-1 is aberrantly expressed in the PDAC cellular membrane, contributes to PDAC pathogenesis, and confers a poor prognosis. Plectin-1-targeting peptides (PTP) in mice and humans have been successfully explored for their use in PDAC imaging and targeted payload delivery (small molecules, radioisotopes, and chemotherapy). We sought to take advantage of the specific binding of PTP and develop a peptide-based plectin-1 chimeric antigen receptor (CAR), and test T-cell transduced with this construct in vitro against PDAC cell lines. Methods: Using in silico tools, we optimized different pepto-CAR constructs and selected one that showed the highest levels of cytotoxicity against plectin-1-expressing PDAC cell lines. A myc tag was incorporated in the hinge region for flow cytometry or western blot detection. The intracellular signaling domain of these CAR sequences included 4-1BB and the zeta chain of the CD3 molecule ( Figure 1A). Plasmids containing the CAR sequence were packaged on lentivirus particles using HEK293T cells. Purified plectin-1 CAR lentiviruses were used to transduce T-cells derived from human peripheral blood T-cells obtained and purified from healthy donor whole blood. The expanded CAR T-cells were used for cytotoxic experiments against different cell lines. Results: Expression of plectin-1 CAR was confirmed by flow cytometry using an anti-myc tag antibody ( Figure 1B). Plectin-1 expression was analyzed in different pancreatic cancer cell lines, and the BxPC-3 cells showed the highest expression level ( Figure 1B). Using a luciferase-based assay, we plated 50,000 BxPC-3 cells per well in duplicates with different effector-to-target (E:T) ratios. After 24 hours, luciferin was added, and the plate was read using a luminometer. As a negative control for effector cells, we use T-cells without a CAR ( Figure 1B), and for the target cells, we use the plectin-1 negative lung cancer cell line A549 ( Figure 1B). Plectin-1 CAR T-cells effectively killed BxPC-3 cells at different E:T ratios in a specific manner compared with controls using unmodified T-cells. Furthermore, no cytotoxicity was observed against plectin-1 negative A549 cells ( Figure 1A). Conclusion: Our results show that a novel peptide-based CAR construct design against plectin-1 can induce specific cytotoxicity on plectin-1 expressing PDAC cell line BxPC-3. Furthermore, these data demonstrate the feasibility of using a CAR with a peptide-based antigen binding domain instead of the traditional antibody-derived scFv. This novel peptide-based CAR design offers alternatives for cellular therapy bioengineering. Moreover, our results can significantly impact immune-oncology therapeutic applications, particularly in challenging diseases like pancreatic cancer. Figure 1 . A) In the above section, the Plectin-1 CAR construct is depicted. Cytotoxicity of unmodified T-cells and Plectin-1 CAR T-cells against BxPC-3 and A549 is shown below. B) Expression of Plectin-1 CAR in unmodified T-cells and Plectin-1 CAR T-cells is shown on the left. The expression of plectin-1 antigen on the surface of BxPC-3 cells and A549 cells is shown on the right. PTP: plectin-1 targeting peptide.

Development of a medium throughput whole-cell microtiter plate Thr286 autophosphorylation assay for CaMKIIα using ELISA

Ca2+/calmodulin-dependent protein kinase II alpha (CaMKIIα) is a multifunctional Ser/Thr kinase involved in several neuronal signaling pathways including synaptic plasticity. CaMKIIα autonomous activity is highly dependent on Thr286 autophosphorylation (pThr286), which is widely used as a readout for its enzymatic activity. To readily characterise compounds and potential drug candidates targeting CaMKIIα, a simple, generic cell-based assay for quantification of pThr286 levels is needed. In this study, we present a cell-based assay using an adapted ELISA as a suitable and higher throughput alternative to Western blotting. In this 96-well plate-based assay, we use whole HEK293T cells recombinantly expressing CaMKIIα and apply a phospho-specific antibody to detect pThr286 levels by chemiluminescence. In parallel, total CaMKIIα expression levels are detected by fluorescence using an Alexa488-conjugated anti-myc antibody targeting a C-terminal myc-tag. By multiplexing chemiluminescence and fluorescence, phosphorylation levels are normalised to CaMKIIα total expression within each well. The specificity of the assay was confirmed using a phosphodead mutant (T286A) of CaMKIIα. By applying Ca2+ or known CaMKIIα inhibitors (KN93, tatCN21 and AS100105) and obtaining concentration-response curves, we demonstrate high sensitivity and validity of the assay. Lastly, we demonstrate the versatility of the assay by determining autophosphorylation levels in CaMKIIα patient-related mutations, known to possess altered pThr286 responses (E109D, E183V and H282R). The established assay for CaMKIIα is a reproducible, easily implemented, and facile ELISA-based assay that allows for reliable quantification of pThr286 levels.

Homeobox 27, a Homeodomain Transcription Factor, Confers Tolerances to CMV by Associating with Cucumber Mosaic Virus 2b Protein.

Transcription factors (TFs) play an important role in plant development; however, their role during viral infection largely remains unknown. The present study was designed to uncover the role transcription factors play in Cucumber mosaic virus (CMV) infection. During the screening of an Arabidopsis thaliana (Col-0) transcription factor library, using the CMV 2b protein as bait in the yeast two-hybrid system, the 2b protein interacted with Homeobox protein 27 (HB27). HB27 belongs to the zinc finger homeodomain family and is known to have a regulatory role in flower development, and responses to biotic and abiotic stress. The interaction between CMV 2b and HB27 proteins was further validated using in planta (bimolecular fluorescence complementation assay) and in vitro far-Western blotting (FWB) methods. In the bimolecular fluorescence complementation assay, these proteins reconstituted YFP fluorescence in the nucleus and the cytoplasmic region as small fluorescent dots. In FWB, positive interaction was detected using bait anti-MYC antibody on the target HB27-HA protein. During CMV infection, upregulation (~3-fold) of the HB27 transcript was observed at 14 days post-infection (dpi) in A. thaliana plants, and expression declined to the same as healthy plants at 21 dpi. To understand the role of the HB27 protein during CMV infection, virus accumulation was determined in HB27-overexpressing (HB27 OE) and knockout mutants. In HB27-overexpressing lines, infected plants developed mild symptoms, accumulating a lower virus titer at 21 dpi compared to wild-type plants. Additionally, knockout HB27 mutants had more severe symptoms and a higher viral accumulation than wild-type plants. These results indicate that HB27 plays an important role in the regulation of plant defense against plant virus infection.

Abstract 1535: Novel lncRNA ENSG00000254887 is a key factor for MYC-driven cell proliferation

Abstract Long non-coding RNAs (lncRNAs) are widely expressed, and many of them are involved in gene regulation. In a CRISPRi study, we looked for lncRNAs required for MYC-driven proliferation in human lymphoid cells and found a novel lncRNA, ENSG00000254887, among the top candidates. In the genome, ENSG00000254887 is head-to-head with a coding gene, POU2F2. To our knowledge, ENSG00000254887 has not been described in the literature yet. We aim to characterize the importance of ENSG00000254887 in cancer development and its mechanisms of action. We performed a ChIP analysis to confirm the direct interaction of MYC with ENSG00000254887 in Ramos cells, a Burkitt’s lymphoma cell line. To knock down the expression, we generated a library of single guide RNAs (sgRNAs) covering the whole length of ENSG00000254887. We transduced Cas9-expressing Ramos cells with this library and cultured them for 14 days. We then measured the differential depletion of guides using next generation sequencing. To validate these results, we performed CRISPR growth competition assays with individual GFP-expressing sgRNA constructs, and the cell growth was measured by flow cytometry. We corroborated the importance of ENSG00000254887-regulated expression by two additional approaches: downregulation by small-hairpin RNA (shRNA) and upregulation by expression of an ectopic copy of the gene. We have been able to retrieve the genomic sequence of ENSG00000254887 using an anti-MYC antibody, thus confirming the presence of binding sites for this transcription factor. Using CRISPR, we have mapped several sites along the ENSG00000254887 sequence where Cas9-introduced changes lead to loss of function and reduce the ability of the cells to proliferate. We selected three of the most efficient sgRNAs used for CRISPR for further analysis and observed that they induced a reduction in the expression of both ENSG00000254887 and the nearby coding gene, POU2F2. This significant result was validated using shRNA targeting the sequence of the lncRNA. On the contrary, the overexpression of ENSG00000254887 from an inducible ectopic copy has no effect on the expression of POU2F2. In conclusion, the expression of ENSG00000254887 is critical for MYC-driven cell proliferation and can be altered through Cas9-introduced changes. A downregulation of this lncRNA is always accompanied by a reduction in the expression of the nearby coding gene, POU2F2. The absence of any effect on POU2F2 when we overexpress ENSG00000254887 from an ectopic copy indicates that this lncRNA might be acting in cis. However, further research is needed to explain this fact and establish the molecular mechanisms. Acknowledgments: This work was supported by the National Cancer Institute of the National Institutes of Health under award R35 CA197582 (PKV). Citation Format: Daniel García-Caballero, Jonathan R. Hart, Peter K. Vogt. Novel lncRNA ENSG00000254887 is a key factor for MYC-driven cell proliferation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1535.

Identification, functional characterization and expression pattern of myeloid differentiation factor 88 (MyD88) in Nibea albiflora

Myeloid differentiation factor 88 (MyD88), composed of an N-terminal death domain and a C-terminal Toll/interleukin (IL)-IR homology domain, is a key connector protein in the TLR signal transduction pathway. In this study a novel isoform of MyD88 in Nibea albiflora (named as NaMyD88) was identified and functionally characterized (GenBank accession no. MN384261.1). Its complete cDNA sequence was 1672 bp and contained an open reading frame of 879 bp encoding 292 amino acid residues, which was similar to its teleost fish counterparts in the length. The theoretical molecular mass was 33.63 kDa and the isoelectric point was 5.24. BLASTp analysis suggested that the deduced amino acids sequence of NaMyD88 shared high identity to the known MyD88, for instance, 94.77% identity with Collichthys lucidus. Sequence analysis showed that NaMyD88 protein was consistent with MyD88 protein of other species at three conserved domains, N-terminal DD, short middle domain and C-terminal TIR, and the TIR domain contained three highly conserved motifs: Box1, Box2, and Box3. NaMyD88 and red fluorescent protein (Dsred) were fused and expressed in the cytoplasm of the epithelioma papulosum cyprini (EPC cells). The NaTLR9-TIR-EGFP fusion protein, which was obtained in our previous studies, showed green fluorescence and mainly distributed in the cytoplasm. After co-transfection, NaMyD88-Dsred and NaTLR9-TIR-EGFP obviously overlapped and displayed orange-yellow color. The results showed that the homologous MyD88-Dsred could interact with NaTLR9-TIR-EGFP. Based on this result pcMV-NaMyD88-TIR-Myc plasmids and the pcDNA3.1-NaTLR9-TIR-flag were constructed and co-transfected into 293T cells for the immunoprecipitation test. According to Western blot, the protein eluted by Flag-beads could be detected by anti-Flag-tag antibody and anti-Myc tag antibody respectively, while the protein without NaTLR9-TIR could not be found, which further proved that TLR and MyD88 could interact each other. The prokaryotic plasmid of MyD88-TIR domain was constructed, expressed in BL21 (DE3) and purified by Ni-NAT super flow resin conforming to the expected molecular weight of 27 kDa with the corresponding active sites for its conferring protein-protein interaction functions. Real-time fluorescence quantitative PCR showed that NaMyD88 could be expressed in intestine, stomach, liver, kidney, gill, heart and spleen, with the highest in the kidney, and it was up-regulated after being infected with Polyinosinic:polycytidylic acid - Poly (I:C) and Pseudomonas plecoglossicida, which showed that NaMyD88 was involved in the immune response of N.albiflora. These data afforded a basis for understanding the role of NaMyD88 in the TLR signaling pathway of N.albiflora.

Abstract MP29: A Cloned Anti-aminopeptidase N Scfv Antibody Blocks Enzymatic Activity And Rescues A Low Sodium Phenotype In Proximal Tubule Cells Isolated From Inverse Salt Sensitive Participants

Inverse Salt Sensitivity (ISS), defined as the paradoxical increase in blood pressure of individuals on a low sodium diet compared to a high sodium diet, may be associated with the increase in mortality and morbidity found in individuals on a low sodium diet. Our group has previously found that urine derived human renal proximal tubule cells (RPTC) isolated from ISS participants express higher Aminopeptidase N (APN) protein than cells isolated from salt resistant (SR) participants. An anti-Aminopeptidase N (APN) hybridoma was used construct a single chain variable fragment (scFv) into a bacterial expression system. The purified anti-APN scFv bound to live human renal proximal tubule cells, detected using an Alexa594 directly labelled anti-myc monoclonal antibody by immunofluorescent confocal microscopy. The anti-APN scFv was then tested to determine if it blocks APN enzymatic activity. We have previously shown that under low sodium conditions the amount of reduced-glutathione as determined by live cell fluorescence staining with the redox sensitive dye, monochlorobimane (mBCl), is decreased only in ISS cells under low sodium conditions at the two-hour time point. We hypothesized that the decreased mBCl signal may be due to the increased APN expression and activity altering the Ang II/Ang III ratio and reducing the Ang III activation of the AT 2 R. Low sodium reduced the mBCl signal in ISS (-29.2±4.3%, ISS vs SR, N=3 per group, p<0.05) and the addition of the anti-APN scFv at 1 ug/ml completely blocked the mBCl signal back to levels found in SR in normal salt conditions. In order to verify that the full rescue of this ISS specific response is due to enhanced Ang III – AT 2 R signaling, we next tried to block the effect of the anti-APN scFv by the addition of the AT 2 R antagonist, PD123319 (PD, 1 uM). Addition of PD alone to the ISS LS RPTCs did not significantly alter the mBCl signal, but when PD and anti-APN scFv are added to the LS treated ISS cells, there is complete reversal of the effect of anti-APN scFv alone (-38.1±3.9%, ISS anti-APN scFv + PD vs ISS anti-APN scFv, N=3 per group, p<0.05). The anti-APN scFv has potential therapeutic value by reducing APN enzymatic activity in ISS individuals and inducing the protective AT 2 R arm of the renin angiotensin system in low sodium conditions.

1147-P: Pseudo Insulin Resistance: Palmitate Inactivates Insulin Signaling but Stimulates Basal Glucose Uptake in 3T3-L1 Adipocytes

Increased levels of circulating free fatty acids (FFA) is the major risk factor for type 2 diabetes in obesity. While the long-term effects of increased FFA on adipose tissue likely involve latent inflammation, the short-term effects on insulin-sensitive adipocytes are less clear. We treated fully differentiated 3T3-L1 adipocytes with increased concentrations (0.3-1 mM) of a typical FFA, palmitate, for 2 days, and measured insulin stimulation of 2-deoxyglucose (2-DG) uptake. The insulin cascade and AMPK activities, Glut-1 and Glut-4 levels were measured by western blots (WB). Glut-4 translocation was measured either by WB after cell membrane fractionation, or by fluorescence analysis after lentiviral transduction of adipocytes with Glut-4 construct containing C-terminal mCherry and outer Myc epitope insertion in the Glut-4 extracellular loop. While fluorescence of mCherry reported the total Glut-4, that of anti-Myc antibody revealed Glut-4 exposed on the plasma membrane. Palmitate dose dependently increased basal 2-DG uptake, whereas insulin-stimulated uptake and Glut-4 translocation to the plasma membrane were significantly reduced only by high (1 mM) palmitate. High palmitate did not alter Glut-1 and Glut-4 expression, but reduced IRS phosphorylation (Tyr612) and completely ceased that of Akt (Thr308/Ser473) and AS160 (Ser318) in the absence or presence of insulin, as well as phosphorylation of ACC (Ser-79) by AMPK. These results suggest that the short-term effects of palmitate on adipocytes are associated with “pseudo” insulin resistance, i.e., an increased basal glucose uptake likely due to the “pull” mechanism for increased triglyceride turnover, and the loss of insulin stimulation possibly due to fill-up of fat depots. Disclosure N. Podkuychenko: None. S. Michurina: None. I. Stafeev: None. A. Y. Khapchaev: None. V. P. Shirinsky: None. A. V. Vorotnikov: None. Funding Russian Foundation for Basic Research (20-015-00471)

High MYC Protein Expression in MDS Is Associated with Early Transformation to AML

Acute myeloid leukemia (AML) with myelodysplasia-related changes (AML-MRC) is shown to be associated with dismal clinical outcomes and there remains a pressing need for new therapeutic strategies to improve survival outcomes. It is also important to identify targetable markers that could predict an earlier AML transformation from preexisting MDS. Our recent studies demonstrated that high expression level of MYC oncoprotein is associated inferior survival outcome in AML-MRC patients and that MYC plays an oncogenic role by epigenetic regulation of hydroxylation of 5-methylcytosine. However, the role of MYC in MDS to AML progression remain to be answered. Here, we investigated MYC protein expression levels in bone marrow (BM) specimens of patients with preexisting MDS and their subsequent AML-MRC specimens to determine whether increased MYC expression is associated with early AML progression. We retrospectively identified 32 patients with histologically confirmed AML-MRC evolving from MDS and evaluated MYC protein levels in BM biopsy specimens at the time of initial MDS diagnosis and at the time of disease transformation to AML-MRC, respectively. Clinical data including age at diagnosis, gender, CBC with differential count, cytogenetics, somatic mutations common in myeloid disease, blasts count, and IPSS were extracted at the time of MDS and AML-MRC diagnosis. MYC expression was assessed by immunohistochemistry on 4-5µm tissue sections. Deparaffinized slides were stained with anti-MYC antibody (clone Y69, Roche Diagnostics) using a Ventana Benchmark automated system. MYC expression was scored independently by two hematopathologists and categorized as low vs. high as previously described. The cut-off for high MYC expression is ≥5% positive cells. The MDS-to-AML progression free survival (PFS) and overall survival (OS) were calculated from the date of MDS diagnosis and outcomes were estimated with the Kaplan-Meier method and compared using the log-rank test. All statistical analyses were performed using SPSS v24.0. Among 32 patients, 69% (n=22) and 31% (n=10) patients had low and high MYC expression at MDS diagnosis (Table 1). The median age was 67.9 (33.5-78.7) and 61.1 (38.9-73.4) and the % of MYC positive blasts were 1% (range, 0-4.5) and 17.5% (range, 5-27.5) in low and high MYC groups, respectively, at the time of MDS diagnosis. There was no statistical difference in BM blast counts between low vs. high MYC groups (median 5% vs. 7.5%, p=0.4951). IPSS risk assessment in a total of 26 patients (19 in low MYC and 7 in high MYC) showed that 9% (n=2), 27% (n=6), 32% (n=7), and 18% (n=4) in low MYC group and 0% (n=0), 20% (n=2), 20% (n=2), and 30% (n=3) in high MYC groups had low, intermediate-I, intermediate-II, and high risk at the time of MDS diagnosis (Table 1). A total of 84% (86% [n=19] in low MYC and 80% [n=8] in high MYC) patients received treatments for MDS; ESA in 16% (n=5), hypomethylating agents in 81% (n=26), and Revlimid in 16% (n=5) (Table 1). Allogeneic stem cell transplant (allo-SCT) was performed in 12.5% (n=4) patients (n=3, low MYC; n=1, high MYC). Following AML progression, a total of 91% (n=29) patients received treatment for AML including induction chemotherapy (n=18), hypomethylating agents (n=7), and other therapies including trial (n=4) (Table 1). In the univariate analyses, patients with low MYC expression had significantly longer MDS-to-AML PFS (median 15.8 vs. 7.25 months, HR=0.1745, 95%CI=0.0591-0.5157, p=0.0016) (Figure 1), however, there was no OS difference between two groups (4.32 vs. 2.35 years, HR=0.5131, 95%CI=0.1064-2.475, p=0.6909). In a multivariate Cox model (adjusting for IPSS, age, front-line therapy, gender, allo-SCT, and MYC level), high MYC expression (HR=3.939, 95%CI=1.107-14.012, p=0.034) and IPSS risk (HR=1.903, 95%CI=1.139-3.181, p=0.014) were significant factor for MDS-to-AML PFS. In conclusion, high MYC expression at the MDS stage was associated with shorter time to AML progression, indicating that MYC plays an oncogenic role in MDS to AML transformation. Although our findings need further validation by prospective studies with greater sample size, our results support a combination treatment of hypomethylating agents with novel agents targeting MYC or/and its downstream pathways and warrant further study to identify underlying mechanisms of MYC-driven MDS to AML progression. Disclosures Talati: Pfizer: Honoraria; Astellas: Speakers Bureau; Jazz: Speakers Bureau; BMS: Honoraria; AbbVie: Honoraria. Kuykendall:Blueprint Medicines: Research Funding; BMS: Research Funding; Incyte: Research Funding; Novartis: Research Funding. Padron:Novartis: Honoraria; Incyte: Research Funding; Kura: Research Funding; BMS: Research Funding. Komrokji:JAZZ: Honoraria, Speakers Bureau; BMS: Honoraria, Speakers Bureau; Novartis: Honoraria; Incyte: Honoraria; Acceleron: Honoraria; Geron: Honoraria; AbbVie: Honoraria; Agios: Honoraria, Speakers Bureau. Lancet:Abbvie: Consultancy; Agios Pharmaceuticals: Consultancy, Honoraria; Astellas Pharma: Consultancy; Celgene: Consultancy, Research Funding; Daiichi Sankyo: Consultancy; ElevateBio Management: Consultancy; Jazz Pharmaceuticals: Consultancy; Pfizer: Consultancy. Sallman:Celgene, Jazz Pharma: Research Funding; Agios, Bristol Myers Squibb, Celyad Oncology, Incyte, Intellia Therapeutics, Kite Pharma, Novartis, Syndax: Consultancy.

LDL receptor-related protein LRP6 senses nutrient levels and regulates Hippo signaling.

Controlled cell growth and proliferation are essential for tissue homeostasis and development. Wnt and Hippo signaling are well known as positive and negative regulators of cell proliferation, respectively. The regulation of Hippo signaling by the Wnt pathway has been shown, but how and which components of Wnt signaling are involved in the activation of Hippo signaling during nutrient starvation are unknown. Here, we report that a reduction in the level of low-density lipoprotein receptor-related protein 6 (LRP6) during nutrient starvation induces phosphorylation and cytoplasmic localization of YAP, inhibiting YAP-dependent transcription. Phosphorylation of YAP via loss of LRP6 is mediated by large tumor suppressor kinases 1/2 (LATS1/2) and Merlin. We found that O-GlcNAcylation of LRP6 was reduced, and the overall amount of LRP6 was decreased via endocytosis-mediated lysosomal degradation during nutrient starvation. Merlin binds to LRP6; when LRP6 is less O-GlcNAcylated, Merlin dissociates from it and becomes capable of interacting with LATS1 to induce phosphorylation of YAP. Our data suggest that LRP6 has unexpected roles as a nutrient sensor and Hippo signaling regulator.

MYC expression has limited utility in the distinction of undifferentiated radiation-associated sarcomas from sporadic sarcomas and sarcomatoid carcinoma.

MYC is a proto-oncogene that is frequently dysregulated in various malignancies, through translocation or amplification. Radiation-associated angiosarcoma frequently shows MYC amplification, and immunohistochemical expression has been shown to be a reliable surrogate marker for amplification, but less is known about MYC expression in other sarcoma types, despite reports of MYC amplification in some undifferentiated/unclassified radiation-associated sarcomas (RASs). Distinguishing putative RAS from non-radiation-associated sarcoma or sarcomatoid carcinoma can be difficult. The aim of this study was to determine the prevalence and potential diagnostic utility of MYC in this context, by evaluating MYC expression in a cohort of RASs, non-radiation-associated sarcomas, and sarcomatoid carcinomas. Three hundred and eighty-five neoplasms were evaluated, including 81 RASs (18 angiosarcomas; 57 undifferentiated sarcomas; three leiomyosarcomas; and three malignant peripheral nerve sheath tumours), 267 non-radiation-associated sarcomas, and 37 sarcomatoid carcinomas. Immunohistochemistry was performed with a monoclonal anti-MYC antibody. Staining in tumour cells was scored on the basis of extent (focal, 1-4%; multifocal, 5-49%; and diffuse, ≥50%) and intensity (strong, moderate, and weak). One hundred percent of radiation-associated angiosarcomas expressed MYC diffusely. Expression was infrequent among other types of RAS (9.5%), and the frequency was similar to that in non-radiation-associated sarcomas (9.7%). MYC expression was more common in sarcomatoid carcinomas, occurring in 43%. The extent and intensity of staining were variable in all groups. MYC expression is infrequent among RASs other than angiosarcoma, and has a similar prevalence in sporadic sarcomas. Given the frequency of expression in sarcomatoid carcinomas, MYC expression outside the context of radiation-associated angiosarcoma is of limited diagnostic utility, and should be interpreted with caution after exclusion of sarcomatoid carcinoma where relevant.

Role of MYC-miR-29-B7-H3 in Medulloblastoma Growth and Angiogenesis.

Medulloblastoma (MB) is the most common embryonal neuroepithelial tumor, with poor patient outcomes and secondary complications. In this study, we investigated the role of the B7 family of immune checkpoint homolog 3 (B7-H3) expression in MB angiogenesis. B7-H3, a co-inhibitory immune checkpoint, is highly expressed and is associated with lower overall survival in MYC+ MB’s. Evidence for a direct transcriptional role of MYC on the B7-H3 gene promoter was confirmed by MYC inhibition and anti-MYC antibody ChIP analysis. Interestingly, MYC inhibition not only downregulated the B7-H3 protein expression, but also rescued miR-29 expression, thus indicating a triangular regulatory relationship between MYC, miR-29, and B7-H3 in Group 3 MB cells. From RNA seq and IPAD assay, we observed a negative feedback loop between miR-29 and MYC that may control B7-H3 expression levels in MB cells. Our studies show that B7-H3 expression levels play a crucial role in promoting MB angiogenesis which can be inhibited by miR-29 overexpression via miR-29-mediated B7-H3 downregulation. The tumor suppressor role of miR-29 is mediated by the activation of JAK/STAT1 signaling that further plays a role in MYC-B7-H3 downregulation in MB. This study highlights B7-H3 as a viable target in MB angiogenesis, and that the expression of miR-29 can inhibit B7-H3 and sensitize MB cells to treatment with MYC-inhibiting drugs.

Multiple charged amino acids of Plasmodium falciparum SURFIN4.1 N-terminal region are important for efficient export to the red blood cell

Plasmodium falciparum, an obligate intracellular protozoan parasite which causes the severe form of human malaria, exports numerous proteins to the infected red blood cell that are important for its survival and of severe pathological effect to its host. These proteins and their export mechanisms are candidates for drug and vaccine development, and among them is the Plasmodium SURFIN family of proteins. Previously we showed that the N-terminal region along with the sequence surrounding the transmembrane domain of SURFIN4.1 is essential for its export to Maurer's clefts in the red blood cell cytoplasm. We proposed that this region is recognized by a machinery responsible for protein translocation across the parasitophorous vacuole membrane surrounding the parasite. To understand the export mechanism further, we utilized a fluorescent protein-tagged mini-SURFIN4.1 consisting of the minimum essential components for export. Alanine scanning of all charged amino acids within the N-terminal region revealed that replacement of 3 glutamic acid and 2 lysine residues significantly impairs the export efficiency of this protein across the parasitophorous vacuole membrane. In addition, N-terminally Myc-tagged mini-SURFIN4.1 and mini-SURFIN4.2 with similar architectures were detected with anti-Myc antibody at Maurer's clefts, indicating that elements required for export to Maurer's clefts are conserved between SURFIN4.1 and SURFIN4.2, and that N-terminal sequences of these SURFIN members are not cleaved during export. Our results implicate a conserved nature of SURFIN export to the red blood cell, particularly an important role of multiple glutamic acid and lysine residues in the SURFIN N-terminal region.

Short-lived AUF1 p42-binding mRNAs of RANKL and BCL6 have two distinct instability elements each.

Regulation of mRNA stability by RNA-protein interactions contributes significantly to quantitative aspects of gene expression. We have identified potential mRNA targets of the AU-rich element binding protein AUF1. Myc-tagged AUF1 p42 was induced in mouse NIH/3T3 cells and RNA-protein complexes isolated using anti-myc tag antibody beads. Bound mRNAs were analyzed with Affymetrix microarrays. We have identified 508 potential target mRNAs that were at least 3-fold enriched compared to control cells without myc-AUF1. 22.3% of the enriched mRNAs had an AU-rich cluster in the ARED Organism database, against 16.3% of non-enriched control mRNAs. The enrichment towards AU-rich elements was also visible by AREScore with an average value of 5.2 in the enriched mRNAs versus 4.2 in the control group. Yet, numerous mRNAs were enriched without a high ARE score. The enrichment of tetrameric and pentameric sequences suggests a broad AUF1 p42-binding spectrum at short U-rich sequences flanked by A or G. Still, some enriched mRNAs were highly unstable, as those of TNFSF11 (known as RANKL), KLF10, HES1, CCNT2, SMAD6, and BCL6. We have mapped some of the instability determinants. HES1 mRNA appeared to have a coding region determinant. Detailed analysis of the RANKL and BCL6 3’UTR revealed for both that full instability required two elements, which are conserved in evolution. In RANKL mRNA both elements are AU-rich and separated by 30 bases, while in BCL6 mRNA one is AU-rich and 60 bases from a non AU-rich element that potentially forms a stem-loop structure.

Restoration of Microrna-126 Expression Reduces Apoptosis in Hepatitis B Virus Infected Hepatocellular Carcinoma Cells

Background and Aim: Hepatocellular carcinoma (HCC) is third leading cause of cancer related mortality worldwide. Chronic hepatitis B (CHB) is one of the reasons for HCC development. India has over 40 million chronic HBV infected individuals, but estimation of HCC is grim. The reasons of the under report may be due to its asymptomatic appearance, late detection in the advanced stages and poor awareness. Extrapolating our previous findings of miR-126 as biomarker for HBV related HCC, here we have elucidated the pathophysiological role of overexpressed miR-126 in hepatocarcinogenesis. Methods: Targets of miR-126 were identified using TargetScan, microRNA.org and miRecords. premiR-126 was cloned, overexpressed in HepG2 cell line and expression of miR-126 and its targets were verified by qRT-PCR and western blot analysis. Trancriptional regulation of miR-126 was decided using ENCODE Chip seq database and verified by ChIP analysis. Cellular apoptosis was determined by Annexin V/PI method. Results: To validate our previous oveservation, miR-126 expression was verified in HBV transfected cell line along with two transactivator proteins HBx and HBc independently. Similar to the data in HCC samples, miR-126 was overexpressed in HBV-DNA transfected cells, but no effect of HBc and HBx was noted. Considering Bioinformatics analysis and ENCODE ChIP-seq data, binding of MYC as major transcription factor for miR-126 was validated by ChIP analysis with anti-MYC antibody and also verified after overexpression of Myc-cDNA. This data correlated with MYC overexpression in HCC samples compared to liver cirrhosis. In silico analysis showed that miR-126 could target several proteins involved in apoptosis and inflammosome pathways (CASP1/CASP3/APAF1/CARD16). Furthermore, apoptosis assay and western blot analysis also showed that miR-126 reduces apoptotic cell death by reducing CASP3 expression. Conclusion: Thus, our data highlights that miR-126 may induce uncontrolled proliferation of cancer cells and inhibition of mir-126 may be an important therapeutic strategy for HBV-related HCC. The authors have none to declare.

Cystatin C-Adiponectin Complex in Plasma Associates with Coronary Plaque Instability.

Aim: Adiponectin (APN) is an adipocyte-derived bioactive molecule with antiatherogenic properties. We previously reported that cystatin C (CysC) abolished the anti-atherogenic effects of APN. We aimed to elucidate the clinical significance of CysC–APN complex in patients with coronary artery disease (CAD).Methods: We enrolled 43 stable CAD male patients to examine the relationship between CysC–APN complex and coronary plaque characteristics. Serum was immunoprecipitated by the anti-APN antibody and immunoblotted by the anti-CysC antibody to demonstrate the presence of CysC–APN complexes in vivo. To confirm their binding in vitro, HEK293T cell lysates overexpressing myc-APN and FLAG-CysC were immunoprecipitated with an anti-myc or anti-FLAG antibody, followed by immunoblotting with an anti-APN or anti-CysC antibody.Results: CysC was identified as a specific co-immunoprecipitant with APN by the anti-APN antibody in human serum. In vitro, FLAG-CysC was co-immunoprecipitated with myc-APN by the antimyc antibody and myc-APN was co-immunoprecipitated with FLAG-CysC by the anti-FLAG antibody. Among CAD patients, serum CysC–APN complex levels negatively correlated with fibrotic components of coronary plaques and positively correlated with either necrotic or lipidic plus necrotic components. Plaque burden negatively correlated with serum APN levels but not serum CysC–APN complex levels. Serum CysC levels had no association with plaque characteristics. In multivariate analysis, CysC–APN complex levels were identified as the strongest negative factor for fibrotic components and the strongest positive factor for both necrotic and lipidic plus necrotic components.Conclusion: Measuring serum CysC–APN complex levels is helpful for evaluating coronary plaque instability in CAD patients.

Abstract 2002: MAX mutations in endometrial cancer are associated with poor patient outcome, altered E-box binding, and increased tumor vascularity

Abstract In contrast to aberrant MYC-signaling, MYC associated factor X (MAX) mutation is not common in many cancers but occurs in a limited number of specific tissue types, where it may be important. We sequenced MAX in 540 endometrioid endometrial cancer (EEC) DNAs. Mutations were seen 5.37% of samples with two hotspots, H28R (n = 12) and R60Q/W (n = 4 R60Q and n = 1 R60W), which accounted for ∼60% of the mutations seen. MAX mutation was associated with reduced recurrence-free survival (RFS) (P = 0.03; HR [95% CI] = 3.798 [1.10-13.0]) and with advanced stage (P = 0.024) and high tumor grade (P = 0.048). The association with reduced RFS remained significant in multivariable analysis (P = 0.05 HR = 2.40 [1.00-5.74]), strongly suggesting MAX mutation contributes to clinical aggressiveness in EEC. Focusing on the H28R hotspot mutation, we performed whole transcriptome expression profiling using AN3CA endometrial cancer cell lines stably expressing exogenous long and short isoforms of flag-tagged MAX-WT and MAX-H28R. Unsupervised hierarchical clustering and principle component analysis proved that the expression profiles for the MAX-H28R long cells were strikingly different than the MAX-H28R short, MAX-WT and unmodified cells. The MAX:DNA interface contains a predicted hydrogen bond between his28 and a guanine residue in the E-box motif. We hypothesized that the his-arg mutation seen in EECs would alter DNA binding, and assessed altered binding via chromatin immunoprecipitation/qPCR (ChIP). MAX-H28R had higher affinity for the NPM1 and CDK4 promoter regions, both of which include E-boxes that are well-established MYC/MAX targets. EMSAs for the same regions confirmed ChIP results, and showed that the supershifted MAX-WT and MAX-H28R complexes had different motilities, consistent with altered confirmation. We showed that an anti-MYC antibody was not able to supershift the EMSA fragment, indicating MYC is not part of the MAX:DNA complex. Co-IP, however, showed MAX-H28R retains MYC binding ability. Based on these findings, we conclude the differences seen in EMSA were with MAX homodimers. RNA-seq revealed differential gene expression in MAX-H28R mutated tumors, and ChIP showed enhanced MAX-H28R affinity for E-boxes in several of the differentially expressed genes. In vivo, MAX-H28R AN3CA xenografts were markedly hemorrhagic compared to MAX-WT. MECA-32 (pan-endothelial marker) staining proved that the MAX-mutant tumors had significantly more vessels per field (2.4-fold increase, P = 0.002). Work is ongoing to test for paracrine factors elaborated by the H28R-mutant AN3CA cells that might contribute to the vascular phenotype. Taken together these data implicate MAX mutation as a novel driver of endometrial tumorigenesis, contributing to tumor aggressiveness through enhanced tumor vascularity and potentially other mechanisms. Citation Format: Christopher J. Walker, Craig Rush, Paola Dama, Maggie Stein, Reena Shakya, Matthew O’Hern, David G. Mutch, David E. Cohn, Paul J. Goodfellow. MAX mutations in endometrial cancer are associated with poor patient outcome, altered E-box binding, and increased tumor vascularity. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2002.

MOAP-1 Mediates Fas-Induced Apoptosis in Liver by Facilitating tBid Recruitment to Mitochondria.

Fas apoptotic signaling regulates diverse physiological processes. Acute activation of Fas signaling triggers massive apoptosis in liver. Upon Fas receptor stimulation, the BH3-only protein Bid is cleaved into the active form, tBid. Subsequent tBid recruitment to mitochondria, which is facilitated by its receptor MTCH2 at the outer mitochondrial membrane (OMM), is a critical step for commitment to apoptosis via the effector proteins Bax or Bak. MOAP-1 is a Bax-binding protein enriched at the OMM. Here, we show that MOAP-1-deficient mice are resistant to Fas-induced hepatocellular apoptosis and lethality. In the absence of MOAP-1, mitochondrial accumulation of tBid is markedly impaired. MOAP-1 binds to MTCH2, and this interaction appears necessary for MTCH2 to engage tBid. These findings reveal a role for MOAP-1 in Fas signaling in the liver by promoting MTCH2-mediated tBid recruitment to mitochondria.

Production of the virus-like particles of nipah virus matrix protein in Pichia pastoris as diagnostic reagents.

The matrix (M) protein of Nipah virus (NiV) is a peripheral protein that plays a vital role in the envelopment of nucleocapsid protein and acts as a bridge between the viral surface and the nucleocapsid proteins. The M protein is also proven to play an important role in production of virus-like particles (VLPs) and is essential for assembly and budding of NiV particles. The recombinant M protein produced in Escherichia coli assembled into VLPs in the absence of the viral surface proteins. However, the E. coli produced VLPs are smaller than the native virus particles. Therefore, the aims of this study were to produce NiV M protein in Pichia pastoris, to examine the structure of the VLPs formed, and to assess the potential of the VLPs as a diagnostic reagent. The M protein was successfully expressed in P. pastoris and was detected with anti-myc antibody using Western blotting. The VLPs formed by the recombinant M protein were purified with sucrose density gradient ultracentrifugation, high-performance liquid chromatography (HPLC), and Immobilized Metal Affinity Chromatography (IMAC). Immunogold staining and transmission electron microscopy confirmed that the M protein assembled into VLPs as large as 200 nm. ELISA revealed that the NiV M protein produced in P. pastoris reacted strongly with positive NiV sera demonstrating its potential as a diagnostic reagent. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1038-1045, 2016.

MYC Immunohistochemistry to Identify MYC-Driven B-Cell Lymphomas in Clinical Practice.

Immunohistochemistry with anti-MYC antibody (MYC IHC) detects MYC protein in fixed samples of aggressive B-cell lymphomas and, according to the number of positive staining tumor nuclei, facilitates tumor subclassification, predicts underlying MYC rearrangements, and stratifies patient outcome. We aimed to determine the performance of MYC IHC in clinical practice. We reviewed MYC IHC performed on control specimens and 256 aggressive B-cell lymphomas and compared clinically reported IHC scores with experts' review. Control tissues showed less than 5% variation in daily IHC staining. Reported and expert IHC scores were well correlated (r = 0.86) with an SD of 14.2%. Reported IHC scores 30% or less and 70% or more were accurate (94.5%) compared with experts in categorizing tumors as "MYC IHC-Low" and "MYC IHC-High," respectively, but scores 40% to 60% were not (60.3%). The mean IHC score among lymphomas with MYC rearrangements was 80%, but with a large range of scores (20%-100%). There was no statistically significant association between IHC score and MYC copy number. Under optimal conditions, clinically reported MYC IHC scores are concordant with expert scores within 15%. MYC IHC does not capture all B-cell lymphomas with MYC rearrangements, however. MYC IHC and MYC fluorescence in situ hybridization are both recommended to identify MYC-driven B-cell lymphomas.