DUSP1 Changes Tumor-Associated Macrophages Gene Profile in the Tumor Microenvironment

Objectives: Inflammation is a key component of the tumor microenvironment (TME) and tumor associated macrophages (TAMs) represent part of the innate immune system responsible for immune surveillance. Cytokines and pro-inflammatory factors derived from TAMs have been shown to have a critical role in the various steps of malignant transformation, including tumor growth, survival, invasion, angiogenesis, and metastasis. We have previously demonstrated that dual-specificity phosphatase-1 (DUSP1), which has been shown to be crucial for negatively regulating innate immune responses, is suppressed in oral cancer, suggesting an important role for DUSP1 as a negative regulator of tumor-promoting inflammation (Cancer Res 15;74(24):7191-7, 2014). The objective of this study was to determine TAM gene expression profile from tumor-bearing wild-type and DUSP1 deficient mice to understand the cellular mechanisms utilized by DUSP1-signaling to instruct TAM recruitment and polarity.

Methods: C57BL/6J syngeneic murine E0771 tumor cells (1x10⁶ cells) were injected into the flanks of wild-type and DUSP1 deficient C57BL/6J mice (12 weeks old; n=3/group). After ~14 days, tumor tissues were harvested and CD11b⁺/F480⁺ mature TAMs were isolated by magnetic cell separation and populations verified by flow cytometry. Additional tumor tissues with harvested for histopathology. To understand how DUSP1 alters TAMs in the TME, multiplex gene expression analysis of 770 genes using Nanostring analysis of the Mouse PanCancer Immune Profiling panel, was performed to quantitate the mRNA expression in wild-type and DUSP1 deficient TAMs from tumor-bearing mice.

Results: DUSP1-deficient tumor-bearing mice had increased inflammatory infiltrate (p<0.05; unpaired Student’s t-test). Nanostring analysis indicated that 38 genes were significantly (at least p<0.05; unpaired Student’s t-test) different including chemokines, cytokines, signaling molecules and macrophage polarity-associated genes.
Conclusions: DUSP1 deficiency alters TAM phenotype, suggesting that MKP-1 could be a viable target to reprogram TAM recruitment and polarity.