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  1. Article ; Online: Targeting CD20-expressing malignant melanoma cells augments BRAF inhibitor killing.

    Mukhtar, Abdullahi B / Morgan, Huw J / Gibbs, Alex / Davies, Gemma E / Lovatt, Charlotte / Patel, Girish K

    The British journal of dermatology

    2024  Volume 190, Issue 5, Page(s) 729–739

    Abstract: Background: Mutant BRAF targeted therapies remain a standard of care for the treatment of metastatic malignant melanoma (MM); however, high initial response rates are tempered by the persistence of residual MM cells that eventually lead to disease ... ...

    Abstract Background: Mutant BRAF targeted therapies remain a standard of care for the treatment of metastatic malignant melanoma (MM); however, high initial response rates are tempered by the persistence of residual MM cells that eventually lead to disease recurrence and mortality. As MM recurrence during targeted therapy can present with the simultaneous occurrence of multiple tumour nodules at the original body sites, we hypothesized the presence of an intrinsically resistant MM cell subpopulation.
    Objectives: To identify an MM cell subpopulation that is intrinsically resistant to targeted therapy and possibly responsible for MM recurrence.
    Methods: Using melanoma cell lines, we defined culture conditions for the reproducible three-dimensional growth of melanospheres to investigate putative cancer stem cell populations. We undertook RNA sequencing and bioinformatic analysis to characterize cell populations between adherent and nonadherent culture, and cells expressing or not expressing CD20. Furthermore, we defined an in vitro assay to evaluate the killing of melanoma cancer stem cells as a therapeutic test using combination therapies targeting driver mutation and CD20.
    Results: We described the culture conditions that promote MM cells to form melanospheres with a reproducible colony-forming efficiency rate of 0.3-1.3%. RNA sequencing of melanosphere vs. conventional MM cell cultures (n = 6), irrespective of the BRAF mutation status, showed that melanosphere formation was associated with growth and differentiation transcriptional signatures resembling MM tumours. Importantly, melanosphere formation also led to the emergence of a CD20+ MM cell subpopulation, similar to that observed in primary human MM tumours. CD20+ MM cells were resistant to BRAF inhibitor therapy and, consistent with this finding, demonstrated a Forkhead box protein M1 transcriptomic profile (n = 6). Combining BRAF inhibitor and anti-CD20 antibody treatment led to the additional killing of previously resistant CD20+  BRAF mutant MM cells.
    Conclusions: In patients with MM that harbour a CD20+ subpopulation, combined therapy with BRAF inhibitor and anti-CD20 antibody could potentially kill residual MM cells and prevent disease recurrence.
    MeSH term(s) Humans ; Melanoma/pathology ; Proto-Oncogene Proteins B-raf/genetics ; Neoplasm Recurrence, Local ; Protein Kinase Inhibitors/pharmacology ; Mutation ; Cell Line, Tumor
    Chemical Substances Proto-Oncogene Proteins B-raf (EC 2.7.11.1) ; Protein Kinase Inhibitors ; BRAF protein, human (EC 2.7.11.1)
    Language English
    Publishing date 2024-02-04
    Publishing country England
    Document type Journal Article
    ZDB-ID 80076-4
    ISSN 1365-2133 ; 0007-0963
    ISSN (online) 1365-2133
    ISSN 0007-0963
    DOI 10.1093/bjd/ljad502
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: CD200 ectodomain shedding into the tumor microenvironment leads to NK cell dysfunction and apoptosis.

    Morgan, Huw J / Rees, Elise / Lanfredini, Simone / Powell, Kate A / Gore, Jasmine / Gibbs, Alex / Lovatt, Charlotte / Davies, Gemma E / Olivero, Carlotta / Shorning, Boris Y / Tornillo, Giusy / Tonks, Alex / Darley, Richard / Wang, Eddie Cy / Patel, Girish K

    The Journal of clinical investigation

    2022  Volume 132, Issue 21

    Abstract: The basis of immune evasion, a hallmark of cancer, can differ even when cancers arise from one cell type such as in the human skin keratinocyte carcinomas: basal and squamous cell carcinoma. Here we showed that the basal cell carcinoma tumor-initiating ... ...

    Abstract The basis of immune evasion, a hallmark of cancer, can differ even when cancers arise from one cell type such as in the human skin keratinocyte carcinomas: basal and squamous cell carcinoma. Here we showed that the basal cell carcinoma tumor-initiating cell surface protein CD200, through ectodomain shedding, was responsible for the near absence of NK cells within the basal cell carcinoma tumor microenvironment. In situ, CD200 underwent ectodomain shedding by metalloproteinases MMP3 and MMP11, which released biologically active soluble CD200 into the basal cell carcinoma microenvironment. CD200 bound its cognate receptor on NK cells to suppress MAPK pathway signaling that in turn blocked indirect (IFN-γ release) and direct cell killing. In addition, reduced ERK phosphorylation relinquished negative regulation of PPARγ-regulated gene transcription and led to membrane accumulation of the Fas/FADD death receptor and its ligand, FasL, which resulted in activation-induced apoptosis. Blocking CD200 inhibition of MAPK or PPARγ signaling restored NK cell survival and tumor cell killing, with relevance to many cancer types. Our results thus uncover a paradigm for CD200 as a potentially novel and targetable NK cell-specific immune checkpoint, which is responsible for NK cell-associated poor outcomes in many cancers.
    MeSH term(s) Humans ; Tumor Microenvironment ; PPAR gamma ; Killer Cells, Natural ; fas Receptor ; Apoptosis ; Carcinoma, Squamous Cell/genetics ; Carcinoma, Basal Cell
    Chemical Substances PPAR gamma ; fas Receptor
    Language English
    Publishing date 2022-11-01
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3067-3
    ISSN 1558-8238 ; 0021-9738
    ISSN (online) 1558-8238
    ISSN 0021-9738
    DOI 10.1172/JCI150750
    Database MEDical Literature Analysis and Retrieval System OnLINE

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