Department of Pharmacology and Toxicology

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Browsing Department of Pharmacology and Toxicology by Author "Abt, Melissa"

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    HUNK as a key regulator of tumor-associated macrophages in triple negative breast cancer
    (Taylor & Francis, 2024-06-05) Ramos Solis, Nicole; Cannon, Anthony; Dilday, Tinslee; Abt, Melissa; Oblak, Adrian L.; Soloff, Adam C.; Kaplan, Mark H.; Yeh, Elizabeth S.; Pharmacology and Toxicology, School of Medicine
    Triple-negative breast cancer (TNBC) lacks the expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). TNBC tumors are not sensitive to endocrine therapy, and standardized TNBC treatment regimens are lacking. TNBC is a more immunogenic subtype of breast cancer, making it more responsive to immunotherapy intervention. Tumor-associated macrophages (TAMs) constitute one of the most abundant immune cell populations in TNBC tumors and contribute to cancer metastasis. This study examines the role of the protein kinase HUNK in tumor immunity. Gene expression analysis using NanoString's nCounter PanCancer Immune Profiling panel identified that targeting HUNK is associated with changes in the IL-4/IL-4 R cytokine signaling pathway. Experimental analysis shows that HUNK kinase activity regulates IL-4 production in mammary tumor cells, and this regulation is dependent on STAT3. In addition, HUNK-dependent regulation of IL-4 secreted from tumor cells induces polarization of macrophages into an M2-like phenotype associated with TAMs. In return, IL-4 induces cancer metastasis and macrophages to produce epidermal growth factor. These findings delineate a paracrine signaling exchange between tumor cells and TAMs regulated by HUNK and dependent on IL-4/IL-4 R. This highlights the potential of HUNK as a target for reducing TNBC metastasis through modulation of the TAM population.
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    HUNK Phosphorylates Rubicon to Support Autophagy
    (MDPI, 2019-11-19) Zambrano, Joelle N.; Eblen, Scott T.; Abt, Melissa; Rhett, J. Matthew; Muise-Helmericks, Robin; Yeh, Elizabeth S.; Pharmacology and Toxicology, School of Medicine
    Background: Autophagy is a catabolic cellular recycling pathway that is essential for maintaining intracellular homeostasis. Autophagosome formation is achieved via the coordination of the Beclin-1 protein complex. Rubicon is a Beclin-1 associated protein that suppresses autophagy by impairing the activity of the class III PI3K, Vps34. However, very little is known about the molecular mechanisms that regulate Rubicon function. Methods: In this study, co-immunoprecipitation and kinase assays were used to investigate the ability of Hormonally Upregulated Neu-associated Kinase (HUNK) to bind to and phosphorylate Rubicon. LC3B was monitored by immunofluorescence and immunoblotting to determine whether phosphorylation of Rubicon by HUNK controls the autophagy suppressive function of Rubicon. Results: Findings from this study identify Rubicon as a novel substrate of HUNK and show that phosphorylation of Rubicon inhibits its function, promoting autophagy.
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    Identification and characterization of a potent and selective HUNK inhibitor for treatment of HER2+ breast cancer
    (Elsevier, 2024) Dilday, Tinslee; Abt, Melissa; Ramos-Solís, Nicole; Dayal, Neetu; Larocque, Elizabeth; Oblak, Adrian L.; Sintim, Herman O.; Yeh, Elizabeth S.; Pharmacology and Toxicology, School of Medicine
    Human epidermal growth factor receptor 2 (HER2)-targeted agents have proven to be effective, however, the development of resistance to these agents has become an obstacle in treating HER2+ breast cancer. Evidence implicates HUNK as an anti-cancer target for primary and resistant HER2+ breast cancers. In this study, a selective inhibitor of HUNK is characterized alongside a phosphorylation event in a downstream substrate of HUNK as a marker for HUNK activity in HER2+ breast cancer. Rubicon has been established as a substrate of HUNK that is phosphorylated at serine (S) 92. Findings indicate that HUNK-mediated phosphorylation of Rubicon at S92 promotes both autophagy and tumorigenesis in HER2/neu+ breast cancer. HUNK inhibition prevents Rubicon S92 phosphorylation in HER2/neu+ breast cancer models and inhibits tumorigenesis. This study characterizes a downstream phosphorylation event as a measure of HUNK activity and identifies a selective HUNK inhibitor that has meaningful efficacy toward HER2+ breast cancer.
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    Mapping the Anti-Cancer Activity of α-Connexin Carboxyl-Terminal (aCT1) Peptide in Resistant HER2+ Breast Cancer
    (MDPI, 2024-01-19) Baker, Kimberly M.; Abt, Melissa; Doud, Emma H.; Oblak, Adrian L.; Yeh, Elizabeth S.; Pharmacology and Toxicology, School of Medicine
    Connexin 43 (Cx43) is a protein encoded by the GJA1 gene and is a component of cell membrane structures called gap junctions, which facilitate intercellular communication. Prior evidence indicates that elevated GJA1 expression in the HER2-positive (HER2+) subtype of breast cancer is associated with poor prognosis. Prior evidence also suggests that HER2+ breast cancers that have become refractory to HER2-targeted agents have a loss of Cx43 gap junction intercellular communication (GJIC). In this study, a Cx43-targeted agent called alpha-connexin carboxyl-terminal peptide (aCT1) is examined to determine whether GJIC can be rescued in refractory HER2+ breast cancer cells. A proposed mechanism of action for aCT1 is binding to the tight junction protein Zonal Occludens-1 (ZO-1). However, the true scope of activity for aCT1 has not been explored. In this study, mass spectrometry proteomic analysis is used to determine the breadth of aCT1-interacting proteins. The NanoString nCounter Breast Cancer 360 panel is also used to examine the effect of aCT1 on cancer signaling in HER2+ breast cancer cells. Findings from this study show a dynamic range of binding partners for aCT1, many of which regulate gene expression and RNA biology. nCounter analysis shows that a number of pathways are significantly impacted by aCT1, including upregulation of apoptotic factors, leading to the prediction and demonstration that aCT1 can boost the cell death effects of cisplatin and lapatinib in HER2+ breast cancer cells that have become resistant to HER2-targeted agents.