LMP student seminars: 2 December

Each week during term time, MSc and PhD candidates in the Department of Laboratory Medicine and Pathobiology present their research.

Anyone is welcome. No need to register.

Location: Medical Sciences Building, rooms 4171 or 4279, see below.

As part of the core research curriculum, students taking LMP1001/2/3: Graduate Seminars in Laboratory Medicine and Pathobiology will present their projects. Please see abstracts below.

2. Cancer, Development and Aging

Location: MSB 4171

Zackary Rousseau

• Title: Novel Cancer Therapy: Targeting Integrin β3 PSI Domain to Simultaneously Impede Cancer Metastasis and Cancer-Associated Thrombosis
• Supervisor: Dr. Heyu Ni

Bailey Organ

• Title: Tumor hypoxia and the risk of metastasis in high-risk localized ups/mfs
• Supervisor: Dr Rebecca Gladdy & Dr. David Shultz

1. Brain and Neuroscience

Location: MSB 4279

Nareh Tahmasian

• Title: Restoring cell-cell communication networks to enhance cognition and reduce inflammation in Alzheimer’s disease
• Supervisor: Dr. JoAnne McLaurin

Fiona Cui

• Title: Investigating the role of brain pericyte glucose-dependent insulinotropic polypeptide receptor (GIPR) signalling in metabolism and neuroinflammation
• Supervisor: Dr. Daniel Drucker

Abstracts

Zackary Rousseau: Novel Cancer Therapy: Targeting Integrin β3 PSI Domain to Simultaneously Impede Cancer Metastasis and Cancer-Associated Thrombosis

Background: Widespread metastases and Cancer-Associated Thrombosis (CAT) represent the two leading causes of death for cancer patients. Platelets are prominent contributors to tumor metastasis and CAT via synergistic, bidirectional communication. A common denominator on cancer cells and platelets is integrin β3; present primarily in the form of ⍺Vβ3 and ⍺IIbβ3 on tumor cells and platelets, respectively. The PSI domain of subunit β3 demonstrates endogenous thiol-isomerase activity contributing to integrin activation and function. However, the role of integrin β3 PSI domain activity in tumour metastasis and CAT has never been explored.

Methods/Results: In this study, we discovered that inhibiting integrin β3 PSI domain with monoclonal antibody PSI E1 reduced spontaneous pulmonary metastasis of cell line 4T1 in orthotopic models of wild type (WT) and thrombocytopenic BALB/c mice, but not β3-/- mice, determined through quantification of metastatic area from HE stains of cryosectioned lung tissue. Additionally, there was decreased metastasis in the untreated 4T1 thrombocytopenia and β3-/- mice compared to WT, suggesting platelet-mediated and possibly platelet-independent effects. Treatment did not abate primary tumor growth in either of these models. Macroscopic observation of lungs retrieved from WT mice bearing 4T1 tumours appeared to have thrombotic events, which was supported by histological staining of fibrin and erythrocytes, that were reduced in the PSI E1-treated cohort. Furthermore, anti-PSI-treated mice exhibited reduced vessel occlusion. Immunofluorescence staining and 3D reconstruction of platelet aggregates in lung cryosections from mice 1 hour after injection with labeled cancer cells revealed a higher ratio of single platelets to platelet aggregates in anti-PSI-treated mice. Importantly, anti-integrin β3 PSI treatment inhibited cancer cell-induced platelet fibrinogen binding, which suggests disruption of a classical mediator for cancer-platelet interaction and a necessary element of CAT.

Conclusions: Inhibiting the PSI Domain of Integrin β3 impairs cancer metastasis and cancer-associated thrombosis possibly through inhibiting cancer-platelet crosstalk.

Bailey Organ: Tumor hypoxia and the risk of metastasis in high-risk localized ups/mfs

Hypoxia activates genetic programs that correlate with more aggressive clinical phenotypes, specifically metastasis. Undifferentiated Pleomorphic sarcomas (UPS) and Myxofibrosarcoma (MFS) are genetically complex, adult sarcomas that have high rates of distant metastasis (DM). Our group has demonstrated using FAZA/PET MRI imaging, that tumour hypoxia correlates with increased DM risk in high-risk localized UPS/MFS. This study therefore aims to delineate the mechanisms by which hypoxia contributes to metastasis in this clinical context. Samples were collected from 20 patients with high-risk UPS/MFS enrolled onto our Phase 2 Clinical Trial (NCT03418818) at Princess Margaret Cancer Centre and Mount Sinai Hospitals, in which pimonidazole (PIMO) was administered 16-20 hours prior to surgery to allow for differentiation of hypoxic (PIMO+) and normoxic (PIMO-) cells from primary tumors. Furthermore, primary patient derived cell lines (MFS, n=4 and UPS n=3) were cultured under hypoxic (0.2% O2) and normoxic (18% O2) conditions for 72 hours, after which bulk RNA sequencing was performed to characterize hypoxic signatures. Additionally, DNA methylation was performed on hypoxic vs. non-hypoxic cells by generating single cell suspensions from primary tumor samples. These samples were freshly dissociated and sorted into PIMO+ and PIMO- cells. DNA was then extracted and analyzed using the Illumina Infinium Methylation EPIC array. Furthermore, to assess differential gene expression in patient tumors based on PIMO staining, we used spatial transcriptomic analyses of FFPE sections using the 10x Genomics Visuim platform. Analysis included the ChAMP package for differential methylation and the EdgeR package for differential gene expression from bulk RNA-seq. For the spatial transcriptomic analysis, samples were analyzed in Python using functions from the Scanpy and Squidpy packages. Analysis of UPS/MFS (n=7) cell lines exposed to hypoxic conditions identified pathways related to development, and demethylase activity DNA methylation analysis revealed differences between hypoxic and normoxic cells, with these differences primarily observed in pathways related to development. These pathways include embryonic skeletal system development, embryonic organ development and skeleton morphogenesis. Spatial transcriptomic analysis differentiated between PIMO-positive and PIMO-negative regions using a distinctive gene signature, including several genes known to be associated with hypoxia such SPP1, FCGR2B, and TREMI.

Nareh Tahmasian: Restoring cell-cell communication networks to enhance cognition and reduce inflammation in Alzheimer’s disease

Alzheimer’s disease (AD) is a devastating neurodegenerative disease estimated to affect over 55 million people worldwide. It is characterized by a progressive loss of neurons leading to deterioration of memory and cognitive ability. An innovative strategy has recently emerged to replace lost neurons by converting another type of brain cell, astrocytes, into neurons. This involves injecting a virus carrying specific ‘reprogramming’ transcription factor genes, driven by the astrocyte GFAP promoter. Promisingly, preliminary work in our laboratory suggests that this approach improves learning and memory in a rat model of AD. We hypothesize that these newly formed neurons not only replace lost ones but also communicate with nearby cells to promote protection and repair. Despite the critical role of cell-cell communication networks in tissue homeostasis and pathogenesis, our knowledge of how these networks are altered in AD is limited. Here, we utilized single-cell RNA-sequencing technology to characterize AD-associated changes to cell-cell communication in the hippocampus in human AD and a rat model of AD. We observed significant changes in neuron-neuron and neuron-endothelial cell signaling, such as an increase in midkine signaling, which is known to modulate neuroinflammation and neurite outgrowth. Next, we used spatial transcriptomics (Visium platform) to show that astrocyte-to-neuron conversion in the AD rat hippocampus significantly altered cell-cell communication networks, including reversing many of these AD-associated signaling patterns, such as midkine signaling. Altering these communication networks may be part of the underlying mechanism for the beneficial effects of astrocyte-to-neuron conversion. Thus, this work not only elucidates some of the cascading molecular effects of astrocyte-to-neuron conversion, but also highlights pathways that can be directly enhanced or inhibited to potentially achieve protective or regenerative effects.

Fiona Cui: Investigating the role of brain pericyte glucose-dependent insulinotropic polypeptide receptor (GIPR) signalling in metabolism and neuroinflammationn

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretin hormones critical for glucose homeostasis, promoting insulin secretion via their respective receptors, GLP-1R and GIPR, on pancreatic islet cells. While GLP-1R agonists (GLP-1RAs) have shown neuroprotective effects in neuroinflammation, a key feature of neurodegenerative diseases like Parkinson’s and Alzheimer’s, the role of GIPR signaling in the brain remains poorly understood. Both receptors are expressed in the brain— while GLP-1Rs are primarily neuronal, GIPRs are mainly found in non-neuronal cells, such as brain pericytes. These pericytes, which interact with endothelial and glial cells to maintain blood-brain barrier (BBB) integrity, may be central to resolving neuroinflammation. To explore this, we are investigating the role of GIPR signaling in neuroinflammation using a lipopolysaccharide (LPS)-induced inflammation model in C57BL/6J mice. By modulating GIPR signaling pharmacologically, we observe time- and region-dependent changes in neuroinflammatory gene expression and microglial activation. Additionally, a brain pericyte-specific GIPR knockout mouse model is being developed to assess the impact of GIPR loss on both metabolic and neuroinflammatory responses. Following confirmation of GIPR knockout, metabolic phenotyping and BBB function analyses will be conducted, alongside a similar LPS protocol, to elucidate the role of GIPR signaling in brain pericytes and its potential therapeutic implications in neurodegenerative diseases.

Contact

No need to register.

Contact lmp.grad@utoronto.ca with any questions