Publications by authors named "Doncho V Zhelev"

Chimeric antigen receptor-T (CAR-T) cells and antibody-drug conjugates (ADCs) are promising therapeutic strategies in oncology. The carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) is overexpressed in tumors including non-small cell lung cancer (NSCLC) and pancreatic ductal adenocarcinoma (PDAC), and is an attractive target for therapies based on CAR-T cell or/and ADCs. We previously developed a highly specific antibody-based CAR-T cells targeting CEACAM5 and the tumoricidal effect of CAR-T cells was proved against neuro-endocrine prostate cancer (NEPC) cells expressing CEACAM5.

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Background: Antibody-drug conjugates (ADCs) that deliver cytotoxic drugs to tumor cells have emerged as an effective and safe anticancer therapy. ADCs may induce immunogenic cell death (ICD) to promote additional endogenous antitumor immune responses. Here, we characterized the immunomodulatory properties of D3-GPC2-PBD, a pyrrolobenzodiazepine (PBD) dimer-bearing ADC that targets glypican 2 (GPC2), a cell surface oncoprotein highly differentially expressed in neuroblastoma.

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Antibody-drug conjugates (ADC) are a targeted cancer therapy that utilize the specificity of antibodies to deliver potent drugs selectively to tumors. Here we define the complex interaction among factors that dictate ADC efficacy in neuroblastoma by testing both a comprehensive panel of ADC payloads in a diverse set of neuroblastoma cell lines and utilizing the glypican 2 (GPC2)-targeting D3-GPC2-PBD ADC to study the role of target antigen density and antibody internalization in ADC efficacy in neuroblastoma. We first find that DNA binding drugs are significantly more cytotoxic to neuroblastomas than payloads that bind tubulin or inhibit DNA topoisomerase 1.

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Glypican 2 (GPC2) is a MYCN-regulated, differentially expressed cell-surface oncoprotein and target for immune-based therapies in neuroblastoma. Here, we build on GPC2's immunotherapeutic attributes by finding that it is also a highly expressed, MYCN-driven oncoprotein on small-cell lung cancers (SCLCs), with significantly enriched expression in both the SCLC and neuroblastoma stem cell compartment.By solving the crystal structure of the D3-GPC2-Fab/GPC2 complex at 3.

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Effective therapies are urgently needed for the SARS-CoV-2/COVID-19 pandemic. We identified panels of fully human monoclonal antibodies (mAbs) from large phage-displayed Fab, scFv, and VH libraries by panning against the receptor binding domain (RBD) of the SARS-CoV-2 spike (S) glycoprotein. A high-affinity Fab was selected from one of the libraries and converted to a full-size antibody, IgG1 ab1, which competed with human ACE2 for binding to RBD.

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We developed an RNA-sequencing-based pipeline to discover differentially expressed cell-surface molecules in neuroblastoma that meet criteria for optimal immunotherapeutic target safety and efficacy. Here, we show that GPC2 is a strong candidate immunotherapeutic target in this childhood cancer. We demonstrate high GPC2 expression in neuroblastoma due to MYCN transcriptional activation and/or somatic gain of the GPC2 locus.

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Sporulation is a critical developmental process in Bacillus spp. that, once initiated, removes the possibility of further growth until germination. Therefore, the threshold conditions triggering sporulation are likely to be subject to evolutionary constraint.

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The formation of pseudopods and lamellae after ligation of chemoattractant sensitive G-protein coupled receptors (GPCRs) is essential for chemotaxis. Here, pseudopod extension was stimulated with chemoattractant delivered from a micropipet. The chemoattractant diffusion and convection mass transport were considered, and it is shown that when the delivery of chemoattractant was limited by diffusion there was a strong chemoattractant gradient along the cell surface.

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Chemoattractant-stimulated pseudopod growth in human neutrophils was used as a model system to study the rate-limiting mechanism of cytoskeleton rearrangement induced by activated G-protein-coupled receptors. Cells were activated with N-formyl-Met-Leu-Phe, and the temperature dependence of the rate of pseudopod extension was measured in the presence of pharmacological inhibitors with known mechanisms of action. Three groups of inhibitors were used: (i) inhibitors sequestering substrates involved in F-actin polymerization (latrunculin A for G-actin and cytochalasin D for actin filament-free barbed ends) or sequestering secondary messengers (PIP-binding peptide for phosphoinositide lipids); (ii) competitively binding inhibitors (Akt-inhibitor for Akt/protein kinase B); and (iii) inhibitors that reduce enzyme activity (wortmannin for phosphoinositide 3-kinase and chelerythrine for protein kinase C).

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Recently we demonstrated the existence of a phosphatidylinositol 3-kinase (PI3K)-independent F-actin polymerization during neutrophil pseudopod extension. Here we examine the use of the PI3K-dependent and PI3K-independent pathways of activation by the N-formyl peptide receptor and the chemokine receptors, and the priming of the 2 pathways by granulocyte-macrophage colony-stimulating factor (GM-CSF) and insulin. The inhibition of PI3K activity with wortmannin showed that rate of pseudopod extension stimulated with N-formyl-Met-Leu-Phe (fMLP was mostly dependent on PI3K, while the rate of interleukin-8 (IL-8)-stimulated pseudopod extension was less dependent on PI3K.

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We characterized the overall rate of F-actin polymerization in the pseudopod region by measuring the rate of extension of single pseudopods stimulated by f-Met-Leu-Phe. The rate of pseudopod extension was measured in the presence of inhibitors for signaling molecules that are known to be involved in motility. Our data show the existence of 2 distinct signaling pathways of actin polymerization in the pseudopod region: a phosphoinositide 3-kinase gamma (PI3Kgamma)-dependent and -independent pathway.

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The neutrophil has developed into one of the most efficient vertebrate motile cells. It migrates through tissues, where it encounters multiple chemoattractant signals with complex spatial and temporal characteristics. The directional movement of the neutrophil is signaled by the binding of chemoattractants and chemokines to G-protein-coupled receptors expressed on the plasma membrane.

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