STEM-01. PHAGE DISPLAY BIOPANNING IDENTIFIES AMOT REGULATING CELL MOTILITY OF BRAIN METASTATIC STEM-LIKE CELLS

OBJECTIVE Metastatic brain tumors (MBTs) are the most common type of malignant brain tumors. Due to the deviation of MBTs from the parental tumors, the effective therapies for primary tumors often are not useful in brain metastases. Even more new intracranial lesions were developed though the primary lesion was under control. The model of brain metastatic stem-like cells (BMSCs) could partially explain the progression of intracranial lesions. Here we aimed to explore the biological behavior in cell motility of BMSCs and understand the potential mechanisms. METHODS In vitro and in vivo phage display biopanning strategies were used to isolate dodecapeptides that specifically target BMICs by selecting against primary lung cancer cells and normal brain cells. In silico analysis was used to derive specific protein targets in BMICs. Potential targets were narrowed down through analysis in patient databases and verified for their presence in BMIC through RT-PCR. Cell migration and adhesion in BMICs were analyzed using Transwell, scratch, and adhesion assays. Protein expression and cell morphology were detected by immunofluorescence. Immune blot was performed to detect the epithelial-mesenchymal related molecules and explore protein-protein interactions. RESULTS In silico analysis of BMSCs specific peptides revealed Angiomotin (Amot) as a potential target in BMSCs. Amot was found to be overexpressed in BMSCs compared to primary lung cancer cells. Kaplan-Meier analysis demonstrated Amot was negatively correlated with overall survival among lung adenocarcinoma patients. Functionally, knockdown of AMOT in BMSCs decreased the capability of cell migration and adhesion by reduced active Cdc42/Rac1 signals caused by downregulation of E-Cadherin. Amot was found to maintain the E-Cadherin in BMSCs through reducing ubiquitination of E-Cadherin. CONCLUSIONS Amot plays a role in promoting migration and adhesion in BMSCs through preservation of E-cadherin.

BSCI-06. Phage display biopanning identifies Amot regulating cell motility in brain metastasis-initiating cells

Objective Metastatic brain tumors (MBTs) are the most common type of malignant brain tumors. Due to the deviation of MBTs from the parental tumors, the effective therapies for primary tumors often are not working in brain metastases. Even more new intracranial lesions were developed though the primary lesion was controlled. The occurrence of brain metastasis-initiating cells (BMICs) suggested the possibility of its spread intracranially. Here we aimed to explore the biological behavior in cell motility of BMICs and understand the potential mechanisms. Methods In vitro and in vivo phage display biopanning strategies were used to isolate dodecapeptides that specifically target BMICs by selecting against primary lung cancer cells and normal brain cells. In silico analysis was used to derive specific protein targets in BMICs. Potential targets were narrowed down through analysis in patient databases and verified for their presence in BMIC through RT-PCR. Cell migration and adhesion in BMICs were analyzed using Transwell, scratch, and adhesion assays. Protein expression and cell morphology were detected by immunofluorescence. Immune blot was performed to detect the epithelial-mesenchymal related molecules and explore protein-protein interactions. Results In silico analysis of BMICs specific peptides revealed Angiomotin (Amot) as a potential target in BMICs. Amot was found to be overexpressed in BMICs compared to primary lung cancer cells. Kaplan-Meier analysis demonstrated Amot was negatively correlated with overall survival among lung adenocarcinoma patients. Knockdown of AMOT in BMICs decreased the capability of cell migration and adhesion, through the downregulation of E-Cadherin. Amot was found to maintain the E-Cadherin in BMICs through reducing ubiquitination of E-Cadherin. Furthermore, the knockdown of E-Cadherin decreased cell migration and adhesion due to the decrease in cdc42 activity. Conclusions Amot plays a role in promoting migration and adhesion in BMICs through preservation of E-Cadherin.

STEM-14. GLIOBLASTOMA STEM CELL TARGETING CHIMERIC ANTIGEN RECEPTOR T CELLS MODIFIED USING PHAGE DISPLAY ISOLATED PEPTIDES

Glioblastoma (GBM) is the most aggressive primary brain tumor with high mortality rates and resistance to conventional therapy. Their resistance to conventional therapy has been attributed to the presence of cancer stem cells (CSCs), a sub-population of tumor cells capable of self-renewal and tumor initiation. Developing novel strategies to specifically target GSCs may allow more effective therapeutic strategies. Using in vivo phage display biopanning, we have identified several peptides with the potential to selectively target and bind GSCs. We wished to leverage the GSC targeting properties of the peptides to augment therapeutic delivery vehicles for the development of novel targeting strategies. We used a combination of GSC targeting peptides to modify the antigen-binding domain of chimeric antigen receptors, by arranging the peptides in tandem at the N-terminus of the CAR molecule. These tandem peptides were tested for binding to GSCs in vitro and in vivo. The functionality of the CAR-T cells was evaluated by measuring cytokine release in the supernatant after overnight co-culture through ELISA. Apoptosis was evaluated by flow cytometry with Annexin V staining. Two different GSC-targeting peptide CAR-T cells demonstrated specific targeting GSCs. Following co-culture with GSCs, GSC targeting CAR-T cells were activated with release of Interferon gamma and subsequently induced GSCs specific apoptosis. These results demonstrate the use of phage display biopanning to isolate GSC targeting peptides which may be used to develop novel GBM specific cytotoxic therapies.

Phage Displayed Domain Antibodies (dAb) for Detection of Allergenic Pistachio Proteins in Foods

Pistachio nuts (Pistacia vera) have been consumed by past and present-day civilizations because of their organoleptic characteristics and potential health benefits. However, they can also produce moderate to severe IgE-mediated reactions in allergic individuals. In this work, we report the isolation of the first recombinant antibodies against pistachio nut, produced without animal immunization, to be used in immunoassays for detection of allergenic pistachio in food products. Several phage display biopanning strategies were evaluated to screen the human-based domain antibody library (dAb) in search for pistachio-specific probes. The clone producing the PVF4 phage-dAb was finally selected, and it does not cross-react with cashew despite the phylogenetic proximity with pistachio. Western blot and matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-TOF/TOF) analysis demonstrated that this clone recognised a unique band of ∼22 kDa related to the basic subunit of pistachio 11S globulin (allergen Pis v 2). The PVF4 phage-dAb allowed detection of pistachio in a food matrix with a limit of detection (LOD) of 3983 mg kg-1 in an indirect phage-enzyme-linked immunosorbent assay (ELISA). The ELISA method developed was used to assess applicability of the PVF4 phage-dAb for analysis of 77 commercial food products.

STEM-23. METASTATIC BRAIN TUMOR IMAGING THROUGH TARGETED PEPTIDES ISOLATED VIA PHAGE DISPLAY BIOPANNING AGAINST BRAIN METASTASIS-INITIATING CELLS

To effectively target metastatic brain tumors (MBTs), the paradigm of initiating treatment against MBTs following detection on clinical imaging needs to be shifted to an understanding of the mechanisms that drive the formation and maintenance of brain metastasis-initiating cells (BMICs). Targeting this tumor sub-population, which may form as a result of activation of the epithelial-mesenchymal transition, may allow for more effective means of understanding and targeting brain metastases. In order to isolate BMICs, we have harvested cells from patient derived MBTs originating from lung cancer and cultured the cells using stem cell media conditions. We then performed in vitro and in vivo phage display biopanning to isolate 12-amino acid length peptides that specifically target BMICs. Several peptides were isolated from both in vitro and in vivo biopanning strategies. Of the peptides recovered, one peptide, LBM4, demonstrated specific binding to MBT cells over primary lung cancer cells in vitro through flow cytometry analysis and immunocytochemistry. Fluorescent tagged LBM4 intravenously injected into mice harboring intracranial brain metastases demonstrated peptide localization to the tumor within the intracranial cavity visualized with live animal imaging. Peptide imaging of tumor corresponded to MRI imaging confirming that the peptides could serve as an alternative to tumor imaging, with the potential for greater sensitivity resulting from the cellular targeting of MBTs. Our results demonstrate that we can use a combination of in vitro and in vivo phage display biopanning to isolate cell specific targeting peptides. MBT targeting peptides can potentially result in a shifting of the clinical treatment paradigm of brain metastases, through the development of more effective targeted therapeutics aimed at BMICs, as well as improving detection of MBT cells which may result in earlier tumor visualization, as well as delineation of tumor recurrence versus radiation effects.

BSCI-15. METASTATIC BRAIN TUMOR TARGETING PEPTIDES ISOLATED THROUGH PHAGE DISPLAY BIOPANNING AGAINST BRAIN METASTASIS-INITIATING CELLS

To effectively target metastatic brain tumors (MBTs), the paradigm of treating MBTs after visualization on clinical imaging needs to be shifted to an understanding of the mechanisms that drive the formation and maintenance of brain metastasis-initiating cells (BMICs). Targeting this tumor sub-population, which may form as a result from activation of epithelial-mesenchymal transition, may allow for more effective means of isolating and targeting brain metastasis. In order to isolate BMICs, we have harvested cells from patient derived MBTs originating from lung cancer and cultured the cells using serum-free media conditions. In vivo phage display biopanning was used to isolate 12-amino acid length peptides that specifically target BMICs. Of the peptides recovered, one peptide, LBM4, was tested for specificity of binding to MBTs through in vitro and in vivo binding assays. When comparing patient derived metastatic brain tumors cells against brain metastasis cell lines, we found that both types of cells demonstrated similar morphology when grown in serum media conditions, but when grown in serum-free media, both demonstrated a tumor sphere morphology, similar to a stem cell-like state. LBM4 demonstrated specific binding to MBT cells over primary lung cancer cells in vitro through flow cytometry analysis and immunocytochemistry. Fluorescent tagged LBM4 intravenously injected into mice harboring intracranial BM demonstrated peptide localization to the tumor within the intracranial cavity visualized with live animal imaging. In vivo phage display biopanning is an effective tool that is able to isolate cell specific targeting peptides. MBT targeting peptides can potentially result in a shifting of the clinical treatment paradigm of brain metastases, through the development of more effective targeted therapeutics aimed at BMICs, as well as improving detection of MBT cells which may result in earlier tumor visualization as well as delineation of tumor recurrence versus radiation effects.