Publications by authors named "Mitzi Lewellen"

We evaluated the antitumor effects of remodeling the MC17 mouse sarcoma microenvironment (SME) by targeting urokinase-type plasminogen activator receptor (uPAR)- and epidermal growth factor receptor (EGFR)-expressing cells. Specifically, we used eBAT (a bispecific ligand-targeted toxin directed to EGFR and uPAR), and its mouse counterpart, meBAT, to ablate uPAR- and/or EGFR-expressing cells. We chose the MC17 model because the cells are resistant to eBAT, allowing us to exclusively evaluate the role of uPAR- and EGFR-expressing cells in the SME.

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EGFR-targeted therapies are efficacious, but toxicity is common and can be severe. Urokinase type plasminogen activator receptor (uPAR)-targeted drugs are only emerging, so neither their efficacy nor toxicity is fully established. Recombinant eBAT was created by combining cytokines EGF and uPA on the same single-chain molecule with truncated toxin.

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Article Synopsis
  • Hemangiosarcoma in dogs and angiosarcoma in humans are aggressive sarcomas originating from blood vessel-forming cells, characterized by disorganized vascular spaces and high metastasis rates.
  • The study used dog-in-mouse xenografts to mimic the tumors' properties, observing the complex interaction between donor and host cells, which led to the development of myeloid hyperplasia and lymphoproliferative tumors.
  • Findings suggest that these sarcomas create a supportive microenvironment for hematopoietic (blood cell) growth, indicating a potential role in tumor progression by regulating surrounding stromal and immune responses.
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Angiosarcoma is a highly aggressive cancer of blood vessel-forming cells with few effective treatment options and high patient mortality. It is both rare and heterogenous, making large, well-powered genomic studies nearly impossible. Dogs commonly suffer from a similar cancer, called hemangiosarcoma, with breeds like the golden retriever carrying heritable genetic factors that put them at high risk.

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The potential of mesenchymal stromal cells (MSCs) to inhibit anti-tumor immunity is becoming increasingly well recognized, but the precise steps affected by these cells during the development of an anti-tumor immune response remain incompletely understood. Here, we examined how MSCs affect the steps required to mount an effective anti-tumor immune response following administration of adenovirus Fas ligand (Ad-FasL) in the Lewis lung carcinoma (LL3) model. Administration of bone marrow-derived MSCs with LL3 cells accelerated tumor growth significantly.

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We previously described a population of lymphoid progenitor cells (LPCs) in canine B-cell lymphoma defined by retention of the early progenitor markers CD34 and CD117 and "slow proliferation" molecular signatures that persist in the xenotransplantation setting. We examined whether valspodar, a selective inhibitor of the ATP binding cassette B1 transporter (ABCB1, a.k.

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Nfatc2 and Tob1 are intrinsic negative regulators of T cell activation. Nfatc2-deficient and Tob1-deficient T cells show reduced thresholds of activation; however, whether these factors have independent or overlapping roles in negative regulation of T cell responses has not been previously examined. Here, we show that Nfatc2 knockout (KO) but not Tob1 KO mice have age-associated accumulation of persistently activated T cells in vivo and expansion of the CD44+ memory cell compartment and age-associated lymphocytic infiltrates in visceral organs, without significant changes in numbers of CD4+CD25+Foxp3+ regulatory T cells (Treg).

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