The novel coronavirus disease (COVID-19) and any future coronavirus outbreaks will require more affordable, effective and safe treatment options to complement current ones such as Paxlovid . Drug repurposing can be a promising approach if we are able to find a rapid, robust and reliable way to down-select and screen candidates using in silico and in vitro approaches. With repurposed drugs, ex vivo models could offer a rigorous route to human clinical trials with less time invested into nonclinical animal ( in vivo ) studies. We have previously shown the value of commercially available ex vivo/3D airway and alveolar tissue models, and this paper takes this further by developing and validating human nasal epithelial model and embryonic stem cells derived cardiomyocyte model. Five shortlisted candidates (fluvoxamine, everolimus, pyrimethamine, aprepitant and sirolimus) were successfully compared with three control drugs (remdesivir, molnupiravir, nirmatrelvir) when tested against key variants of the SARS-CoV-2 virus including Delta and Omicron, and we were able to reconfirm our earlier finding that fluvoxamine can induce antiviral efficacy in combination with other drugs. Scalability of this high-throughput screening approach has been demonstrated using a liquid handling robotic platform for future ‘Disease-X’ outbreaks. ### Competing Interest Statement The authors have declared no competing interest.

Sarbecoviruses such as SARS and SARS-CoV-2 have been responsible for two major outbreaks in humans, the latter resulting in a global pandemic. While sarbecoviruses primarily cause an acute respiratory infection, they have been shown to infect the nervous system. However, mechanisms of sarbecovirus neuroinvasion and neuropathogenesis remain unclear. In this study, we examined the infectivity and trans-synaptic transmission potential of the sarbecoviruses SARS and SARS-CoV-2 in human stem cell–derived neural model systems. We demonstrated limited ability of sarbecoviruses to infect and replicate in human stem cell–derived neurons. Furthermore, we demonstrated an inability of sarbecoviruses to transmit between synaptically connected human stem cell–derived neurons. Finally, we determined an absence of SARS-CoV-2 infection in olfactory neurons in experimentally infected ferrets. Collectively, this study indicates that sarbecoviruses exhibit low potential to infect human stem cell–derived neurons, lack an ability to infect ferret olfactory neurons, and lack an inbuilt molecular mechanism to utilise retrograde axonal trafficking and trans-synaptic transmission to spread within the human nervous system.

The repurposing of licenced drugs for use against COVID-19 is one of the most rapid ways to develop new and alternative therapeutic options to manage the ongoing pandemic. Given circa 7817 licenced compounds available from Compounds Australia that can be screened, this paper demonstrates the utility of commercially available ex vivo/3D airway and alveolar tissue models. These models are a closer representation of in vivo studies than in vitro models, but retain the benefits of rapid in vitro screening for drug efficacy. We demonstrate that several existing drugs appear to show anti-SARS-CoV-2 activity against both SARS-CoV-2 Delta and Omicron Variants of Concern in the airway model. In particular, fluvoxamine, as well as aprepitant, everolimus, and sirolimus, has virus reduction efficacy comparable to the current standard of care (remdesivir, molnupiravir, nirmatrelvir). Whilst these results are encouraging, further testing and efficacy studies are required before clinical use can be considered.

The tumor-suppressor PTPN2 is diminished in a subset of triple-negative breast cancers (TNBCs). Paradoxically, PTPN2-deficiency in tumors or T cells in mice can facilitate T cell recruitment and/or activation to promote antitumor immunity. Here, we explored the therapeutic potential of targeting PTPN2 in tumor cells and T cells. PTPN2-deficiency in TNBC associated with T cell infiltrates and PD-L1 expression, whereas low PTPN2 associated with improved survival. PTPN2 deletion in murine mammary epithelial cells TNBC models, did not promote tumorigenicity but increased STAT-1–dependent T cell recruitment and PD-L1 expression to repress tumor growth and enhance the efficacy of anti-PD-1. Furthermore, the combined deletion of PTPN2 in tumors and T cells facilitated T cell recruitment and activation and further repressed tumor growth or ablated tumors already predominated by exhausted T cells. Thus, PTPN2-targeting in tumors and/or T cells facilitates T cell recruitment and/or alleviates inhibitory constraints on T cells to combat TNBC.

Despite being vaccine preventable, rabies (lyssavirus) still has a significant impact on global mortality, disproportionally affecting children under 15 years of age. This neurotropic virus is deft at avoiding the immune system while travelling through neurons to the brain. Until recently, research efforts into the role of non-coding RNAs in rabies pathogenicity and detection have been hampered by a lack of human in vitro neuronal models. Here, we utilized our previously described human stem cell-derived neural model to investigate the effect of lyssavirus infection on microRNA (miRNA) expression in human neural cells and their secreted exosomes. Conventional differential expression analysis identified 25 cellular and 16 exosomal miRNAs that were significantly altered (FDR adjusted P-value <0.05) in response to different lyssavirus strains. Supervised machine learning algorithms determined 6 cellular miRNAs (miR-99b-5p, miR-346, miR-5701, miR-138-2-3p, miR-651-5p, and miR-7977) were indicative of lyssavirus infection (100% accuracy), with the first four miRNAs having previously established roles in neuronal function, or panic and impulsivity-related behaviors. Another 4-miRNA signatures in exosomes (miR-25-3p, miR-26b-5p, miR-218-5p, miR-598-3p) can independently predict lyssavirus infected cells with >99% accuracy. Identification of these robust lyssavirus miRNA signatures offers further insight into neural lineage responses to infection and provides a foundation for utilizing exosome miRNAs in the development of next-generation molecular diagnostics for rabies.

Rabies is a zoonotic neurological infection caused by lyssavirus that continues to result in devastating loss of human life. Many aspects of rabies pathogenesis in human neurons are not well understood. Lack of appropriate ex-vivo models for studying rabies infection in human neurons has contributed to this knowledge gap. In this study, we utilize advances in stem cell technology to characterize rabies infection in human stem cell-derived neurons. We show key cellular features of rabies infection in our human neural cultures, including upregulation of inflammatory chemokines, lack of neuronal apoptosis, and axonal transmission of viruses in neuronal networks. In addition, we highlight specific differences in cellular pathogenesis between laboratory-adapted and field strain lyssavirus. This study therefore defines the first stem cell-derived ex-vivo model system to study rabies pathogenesis in human neurons. This new model system demonstrates the potential for enabling an increased understanding of molecular mechanisms in human rabies, which could lead to improved control methods.

Abstract Metastatic disease is the major cause of breast cancer–related death and despite many advances, current therapies are rarely curative. Tumor cell migration and invasion require actin cytoskeletal reorganization to endow cells with capacity to disseminate and initiate the formation of secondary tumors. However, it is still unclear how these migratory cells colonize distant tissues to form macrometastases. The E6-associated protein, E6AP, acts both as an E3 ubiquitin-protein ligase and as a coactivator of steroid hormone receptors. We report that E6AP suppresses breast cancer invasiveness, colonization, and metastasis in mice, and in breast cancer patients, loss of E6AP associates with poor prognosis, particularly for basal breast cancer. E6AP regulates actin cytoskeletal remodeling via regulation of Rho GTPases, acting as a negative regulator of ECT2, a GEF required for activation of Rho GTPases. E6AP promotes ubiquitination and proteasomal degradation of ECT2 for which high expression predicts poor prognosis in breast cancer patients. We conclude that E6AP suppresses breast cancer metastasis by regulating actin cytoskeleton remodeling through the control of ECT2 and Rho GTPase activity. These findings establish E6AP as a novel suppressor of metastasis and provide a compelling rationale for inhibition of ECT2 as a therapeutic approach for patients with metastatic breast cancer. Cancer Res; 76(14); 4236–48. ©2016 AACR.

Searchable abstracts of presentations at key conferences in oncology ISSN 2631-4657 (online)

Hypoxia arises frequently in solid tumors and is a poor prognostic factor as it promotes tumor cell proliferation, invasion, angiogenesis, therapy resistance, and metastasis. Notably, there are two described forms of hypoxia present in a growing tumor: chronic hypoxia, caused by abnormal tumor vasculature, and intermittent hypoxia, caused by transient perfusion facilitated by tumor-supplying blood vessels. Here, we demonstrate that intermittent hypoxia, but not chronic hypoxia, endows breast cancer cells with greater metastatic potential. Using an immunocompetent and syngeneic murine model of breast cancer, we show that intermittent hypoxia enhances metastatic seeding and outgrowth in lungs in vivo. Furthermore, exposing mammary tumor cells to intermittent hypoxia promoted clonal diversity, upregulated metastasis-associated gene expression, induced a pro-tumorigenic secretory profile, increased stem-like cell marker expression, and gave rise to tumor-initiating cells at a relatively higher frequency. This work demonstrates that intermittent hypoxia, but not chronic hypoxia, induces a number of genetic, molecular, biochemical, and cellular changes that facilitate tumor cell survival, colonization, and the creation of a permissive microenvironment and thus enhances metastatic growth.

Abstract This abstract was withdrawn by the authors.

Scribble is a highly conserved protein regulator of cell polarity that has been demonstrated to function as a tumor suppressor or, conversely, as an oncogene in a context-dependent manner, and it also controls many physiological processes ranging from immunity to memory. Scribble consists of a leucine-rich repeat domain and four PDZ domains, with the latter being responsible for most of Scribble's complex formation with other proteins. Given the similarities of the Scribble PDZ domain sequences in their binding grooves, it is common for these domains to show overlapping preferences for the same ligand. Yet, Scribble PDZ domains can still exhibit unique binding profiles toward other ligands. This raises the fundamental question as to how these PDZ domains discriminate ligands and exert specificities in Scribble complex formation. To better understand how Scribble PDZ domains direct cell polarity signaling, we investigated here their interactions with the well-characterized Scribble binding partner β-PIX, a guanine nucleotide exchange factor. We report the interaction profiles of all isolated Scribble PDZ domains with a β-PIX peptide. We show that Scribble PDZ1 and PDZ3 are the major interactors with β-PIX and reveal a distinct binding hierarchy in the interactions between the individual Scribble PDZ domains and β-PIX. Furthermore, using crystal structures of PDZ1 and PDZ3 bound to β-PIX, we define the structural basis for Scribble's ability to specifically engage β-PIX via its PDZ domains and provide a mechanistic platform for understanding Scribble-β-PIX–coordinated cellular functions such as directional cell migration.

From 1 Department of Biochemistry & Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia. 2 Cell Cycle & Cancer Genetics Laboratory, Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria 3002, Australia 3 Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, 3002, Australia 4 Department of Biochemistry & Molecular Biology, University of Melbourne, Melbourne, Victoria, 3010, Australia 5 Department of Pathology, University of Melbourne, Melbourne, Victoria, Australia

Erythroid enucleation is the process by which the future red blood cell disposes of its nucleus prior to entering the blood stream. This key event during red blood cell development has been likened to an asymmetric cell division (ACD), by which the enucleating erythroblast divides into two very different daughter cells of alternate molecular composition, a nucleated cell that will be removed by associated macrophages, and the reticulocyte that will mature to the definitive erythrocyte. Here we investigated gene expression of members of the Par, Scribble and Pins/Gpsm2 asymmetric cell division complexes in erythroid cells, and functionally tested their role in erythroid enucleation in vivo and ex vivo. Despite their roles in regulating ACD in other contexts, we found that these polarity regulators are not essential for erythroid enucleation, nor for erythroid development in vivo. Together our results put into question a role for cell polarity and asymmetric cell division in erythroid enucleation.

Women with high mammographic density (MD) are at increased risk of breast cancer (BC) after adjustment for age and body mass index. We have developed a murine biochamber model in which both high MD (HMD) and low MD (LMD) tissue can be propagated. Here, we tested whether cells isolated by collagenase digestion and fluorescence‐activated cell sorting (FACS) from normal breast can be reconstituted in our biochamber model, which would allow cell‐specific manipulations to be tested. Fresh breast tissue was collected from women (n = 7) undergoing prophylactic mastectomy. The tissue underwent collagenase digestion overnight and, in some cases, additional FACS enrichment to obtain mature epithelial, luminal progenitor, mammary stem, and stromal cells. Cells were then transferred bilaterally into biochambers in SCID mice (n = 5–7) and incubated for 6 weeks, before harvesting for histological analyses, and immunohistochemical staining for cytokeratins (CK), vimentin, Ki‐67, murine macrophages, and Cleaved Caspase‐3. Biochambers inoculated with single cells after collagenase digestion or with flow cytometry contained glandular structures of human origin (human vimentin‐positive), which expressed CK‐14 and pan‐CK, and were proliferating (Ki‐67‐positive). Glandular structures from the digested tissues were smaller than those in chambers seeded with finely chopped intact mammary tissue. Mouse macrophage infiltration was higher in the chambers arising from digested tissues. Pooled single cells and FACS fractionated cells were viable in the murine biochambers and formed proliferating glandular organoids of human origin. This is among the first report to demonstrate the success of formed human glandular organoids from isolated primary mammary cells in the murine biochamber model.

Metastatic disease is the major cause of breast cancer related death and despite many advances, current therapies are rarely curative. Tumor cell migration and invasion require actin cytoskeletal reorganisation, to endow cells with capacity to disseminate and initiate the formation of secondary tumors. However, it is still unclear how these migratory cells colonise distant tissues to form macrometastases. The E6-associated protein, E6AP, acts both as an E3 ubiquitin-protein ligase and as a coactivator of steroid hormone receptors. We report that E6AP suppresses breast cancer invasiveness, colonisation and metastasis in mice and in breast cancer patients, loss of E6AP associates with poor prognosis, particularly for with basal breast cancer. E6AP regulates actin cytoskeletal remodelling via regulation of Rho-GTPases, acting as a negative regulator of ECT2, a GEF required for activation of Rho-GTPases. E6AP promotes ubiquitination and proteasomal degradation of ECT2 for which high expression predicts poor prognosis in breast cancer patients. We conclude that E6AP suppresses breast cancer metastasis by regulating actin cytoskeleton remodelling through the control of ECT2 and Rho-GTPase activity. These findings establish E6AP as a novel suppressor of metastasis and provide a compelling rationale for inhibition of ECT2 as a therapeutic approach for patients with metastatic breast cancer. Note: This abstract was not presented at the conference. Citation Format: Mariam Mansour, Sue Haupt, Ai-Leen Chan, Nathan Godde, Alexandra Rizzitelli, Sherene Loi, Franco Caramia, Siddartha Deb, Elena A. Takano, Mark Bishton, Cameron Johnstone, Yarra Levav-Cohen, Yong-Hui Jiang, Alpha S. Yap, Stephen Fox, Ora Bernard, Robin Anderson, Ygal Haupt. The E3-ligase E6AP represses breast cancer metastasis through regulation of ECT2-Rho-GTPases signaling. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr A72.

Metastatic disease is the major cause of breast cancer-related death and despite many advances, current therapies are rarely curative. Tumor cell migration and invasion require actin cytoskeletal reorganization to endow cells with capacity to disseminate and initiate the formation of secondary tumors. However, it is still unclear how these migratory cells colonize distant tissues to form macrometastases. The E6-associated protein, E6AP, acts both as an E3 ubiquitin-protein ligase and as a coactivator of steroid hormone receptors. We report that E6AP suppresses breast cancer invasiveness, colonization, and metastasis in mice, and in breast cancer patients, loss of E6AP associates with poor prognosis, particularly for basal breast cancer. E6AP regulates actin cytoskeletal remodeling via regulation of Rho GTPases, acting as a negative regulator of ECT2, a GEF required for activation of Rho GTPases. E6AP promotes ubiquitination and proteasomal degradation of ECT2 for which high expression predicts poor prognosis in breast cancer patients. We conclude that E6AP suppresses breast cancer metastasis by regulating actin cytoskeleton remodeling through the control of ECT2 and Rho GTPase activity. These findings establish E6AP as a novel suppressor of metastasis and provide a compelling rationale for inhibition of ECT2 as a therapeutic approach for patients with metastatic breast cancer. (C)2016 AACR.

Abstract Hypoxia, the state of low oxygen conditions, occurs frequently in solid tumors and is a poor prognostic factor. The expression of Hif-1α,the main mediator of the hypoxic response pathway, and the subsequent up-regulation of its target genes have been implicated in tumor growth, invasion, angiogenesis, therapy resistance and metastasis. There are two forms of hypoxia present in a growing tumor: chronic hypoxia (caused by limitations in oxygen diffusion from abnormal tumor vasculature) and intermittent hypoxia (caused by the aberrant, repeated and temporary closing and re-opening of blood vessels, leading to fluctuations in oxygen supply). This study investigates the phenotypes endowed by different forms of hypoxia that mediate metastatic potential in a syngeneic mouse model of breast cancer. By exposing murine breast cancer cells to 9 days of 20% O2 (normoxia), 1% O2 (chronic hypoxia) or alternating 24 hour cycles in 20% O2 and 1% O2 (intermittent hypoxia), we observe that intermittent hypoxia produces tumor cells with greater metastatic potential. These treatments produce no difference in primary tumor growth when orthotopically injected into the mammary fat pad of female C57Bl/6 mice. However, intermittent hypoxia-treated cells give rise to a greater number of and larger lung metastases when injected intravenously via the tail-vein of female C57Bl/6 mice. Intermittent hypoxia, but not chronic hypoxia, up-regulated the expression of genes that predict lung metastasis in breast cancer, endowed cells with an enhanced ability for anchorage-independent growth and produced greater clonal diversity. Furthermore, intermittent hypoxia also caused a switch to glycolysis in cells and induced a pro-tumorigenic, immunosuppressive secretory profile in vitro. Finally, intermittent hypoxia up-regulated the expression of mammary stem cell genes, increased expression of stem cell marker Sca-1 as well as CD14, and generated tumor-initiating cells at a higher frequency as evidenced by in vivo limiting dilution assays. This work demonstrates that intermittent hypoxia enhances metastatic seeding and outgrowth by priming cells intrinsically to metastasize, while activating co-operating factors that act extrinsically to form a permissive, immunosuppressive microenvironment. By delineating the contributions of different forms of hypoxia to metastasis, critical molecular mediators can be identified in aid of the development of efficacious therapies that could inhibit, prevent or cure metastatic disease. Citation Format: Anna Chen, Jaclyn Sceneay, Nathan Gödde, Erik Thompson, Patrick Humbert, Andreas Möller. The effects of different types of hypoxia on tumor progression in breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr B48.

Erythroid enucleation is critical for terminal differentiation of red blood cells, and involves extrusion of the nucleus by orthochromatic erythroblasts to produce reticulocytes. Due to the difficulty of synchronizing erythroblasts, the molecular mechanisms underlying the enucleation process remain poorly understood. To elucidate the cellular program governing enucleation, we utilized a novel chemical screening approach whereby orthochromatic cells primed for enucleation were enriched ex vivo and subjected to a functional drug screen using a 324 compound library consisting of structurally diverse, medicinally active and cell permeable drugs. Using this approach, we have confirmed the role of HDACs, proteasomal regulators and MAPK in erythroid enucleation and introduce a new role for Cyclin-dependent kinases, in particular CDK9, in this process. Importantly, we demonstrate that when coupled with imaging analysis, this approach provides a powerful means to identify and characterize rate limiting steps involved in the erythroid enucleation process.

Abstract Cell polarity or cell asymmetry is crucial for the normal biological function of all metazoan cells. Loss of cell polarity disrupts cellular organization that represents one of the hallmarks of cancer progression. Scribble, a member of the core polarity SCRIB module is deregulated in many cancers such as breast cancer, cervical cancer and prostate cancer. Scribble is a member of the LAP family that consists of 16 Leucine Rich Repeats and 4 PSD-95/Discs-large/ZO-1 (PDZ) domains. The PDZ domains (4PDZ) in particular are important in Scribble's interactions with molecules that are involved in many crucial signaling pathways. We hypothesized that Scribble acts as a scaffold protein to orchestrate these interactions. Our aim is to decipher Scribble's mechanism of action through characterization of Scribble interactions with βPIX (PAK-interacting exchange factor beta), which is well establish in exocytosis and neuronal transmission. Herein, we used pull down assay, isothermal titration calorimetry and small angle X-ray scattering to unravel the interaction profile of the region of Scribble encoding for all four PDZ domains. Our study proposes a working model to illustrate how PDZ domains modulate Scribble and βPIX interactions. Citation Format: Krystle YB Lim, Sofia Caria, Colin M. House, Nathan J. Godde, Allison J. Ogden, Patrick O. Humbert, Marc Kvansakul. Cracking the (ultra)structural biology of Scribble to understand its role as a cell polarity regulator and tumor suppressor protein. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C203.