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PLX3397 inhibits the accumulation of intra‐tumoral macrophages and improves bromodomain and extra‐terminal inhibitor efficacy in melanoma
Author(s) -
Erkes Dan A.,
Rosenbaum Sheera R.,
Field Conroy O.,
Chervoneva Inna,
Villanueva Jessie,
Aplin Andrew E.
Publication year - 2020
Publication title -
pigment cell and melanoma research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.618
H-Index - 105
eISSN - 1755-148X
pISSN - 1755-1471
DOI - 10.1111/pcmr.12845
Subject(s) - bromodomain , melanoma , cancer research , medicine , in vivo , macrophage , cd8 , bet inhibitor , immune system , cell , chemistry , immunology , in vitro , epigenetics , biology , biochemistry , microbiology and biotechnology , gene
Bromodomain and extra‐terminal inhibitors (BETi) delay tumor growth, in part, through tumor cell intrinsic alterations and initiation of anti‐tumor CD8+ T‐cell responses. By contrast, BETi effects on pro‐tumoral immune responses remain unclear. Here, we show that the next‐generation BETi, PLX51107, delayed tumor growth to differing degrees in Braf V600E melanoma syngeneic mouse models. These differential responses were associated with the influx of tumor‐associated macrophages during BETi treatment. Tumors that were poorly responsive to PLX51107 showed increased influx of colony‐stimulating factor‐1 receptor (CSF‐1R)‐positive tumor‐associated macrophages. We depleted CSF‐1R+ tumor‐associated macrophages with the CSF‐1R inhibitor, PLX3397, in combination with PLX51107. Treatment with PLX3397 enhanced the efficacy of PLX51107 in poorly responsive Braf V600E syngeneic melanomas in vivo. These findings suggest that tumor‐associated macrophage accumulation limits BETi efficacy and that co‐treatment with PLX3397 can improve response to PLX51107, offering a potential novel combination therapy for metastatic melanoma patients.