CSF1/CSF1R signaling mediates malignant pleural effusion formation
Chrysavgi N. Kosti, Photene C. Vaitsi, Apostolos G. Pappas, Marianthi P. Iliopoulou, Katherina K. Psarra, Sophia F. Magkouta, Ioannis T. Kalomenidis
Chrysavgi N. Kosti, Photene C. Vaitsi, Apostolos G. Pappas, Marianthi P. Iliopoulou, Katherina K. Psarra, Sophia F. Magkouta, Ioannis T. Kalomenidis
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Research Article Angiogenesis Oncology

CSF1/CSF1R signaling mediates malignant pleural effusion formation

Abstract

Malignant pleural effusion (MPE) is an incurable common manifestation of many malignancies. Its formation is orchestrated by complex interactions among tumor cells, inflammatory cells, and the vasculature. Tumor-associated macrophages present the dominant inflammatory population of MPE, and M2 macrophage numbers account for dismal prognosis. M2 polarization is known to be triggered by CSF1/CSF1 receptor (CSF1R) signaling. We hypothesized that CSF1R+ M2 macrophages favor MPE formation and could be therapeutically targeted to limit MPE. We generated mice with CSF1R-deficient macrophages and induced lung and colon adenocarcinoma–associated MPE. We also examined the therapeutic potential of a clinically relevant CSF1R inhibitor (BLZ945) in lung and colon adenocarcinoma–induced experimental MPE. We showed that CSF1R+ macrophages promoted pleural fluid accumulation by enhancing vascular permeability, destabilizing tumor vessels, and favoring immune suppression. We also showed that CSF1R inhibition limited MPE in vivo by reducing vascular permeability and neoangiogenesis and impeding tumor progression. This was because apart from macrophages, CSF1R signals in cancer-associated fibroblasts leading to macrophage inflammatory protein 2 secretion triggered the manifestation of suppressive and angiogenic properties in macrophages upon CXCR2 paracrine activation. Pharmacological targeting of the CSF1/CSF1R axis can therefore be a vital strategy for limiting MPE.

Authors

Chrysavgi N. Kosti, Photene C. Vaitsi, Apostolos G. Pappas, Marianthi P. Iliopoulou, Katherina K. Psarra, Sophia F. Magkouta, Ioannis T. Kalomenidis

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Figure 6

CSF1R inhibition reduces cancer-associated fibroblasts, which stimulates protumor effects of macrophages through the MIP2/CXCR2 axis.

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CSF1R inhibition reduces cancer-associated fibroblasts, which stimulates...
(A and B) CAFs in tumors of vehicle- and CSF1Ri-treated animals were visualized upon FAPA staining. (A) Representative pictures. Scale bar: 50 μm. (B) Results of image analysis. Data presented as mean ± SEM. LLC: n = 4 for both groups. MC38: n = 5 for both groups. *P < 0.05 compared with vehicle by 2-tailed Student’s t test. HPF, high-power field. (C) Activated CAFs isolated from LLC or MC38 tumors were treated with vehicle or 6700 nM CSF1Ri overnight and subsequently loaded with 7 × 104 tumor cells/well; 8 hours later 2 × 105 M1 macrophages/well were added to the tumor cell–CAF cocultures; 24 hours later, tumor cells were counted. (D and E) CD45+CD11b+F4/80+ macrophages were analyzed for IL-10 (D) and IL-12 (E) expression. Data presented as mean ± SEM, 2 independent experiments. LLC: vehicle-treated CAFs n = 5, CSF1Ri-treated CAFs n = 5. MC38: vehicle-treated CAFs n = 7, CSF1Ri-treated CAFs n = 7. *P < 0.05 compared with vehicle-treated CAFs by 2-tailed Student’s t test. (F and G) Isolated CAFs from LLC and MC38 tumors (treated with vehicle or CSF1Ri overnight) were cocultured with macrophages for 48 hours. Macrophages were isolated and mRNA levels of Vegfa (F) and Il6 (G) were quantified by real-time PCR. Data presented as mean ± SEM. n = 7 for both groups, *P < 0.05 compared with indicated group by 2-tailed Student’s t test. (H) Isolated CAFs from LLC or MC38 tumors were treated with vehicle, CSF1Ri, CSF1, or IL-34 or pretreated with CSF1Ri for 2 hours and then CSF1 was added; 24 hours later, MIP2 levels were quantified in supernatants. Results were normalized to total protein. Data presented as mean ± SEM. Vehicle n = 6, CSF1Ri n = 6, CSF1 n = 5, CSF1Ri+CSF1 n = 4, IL-34 n = 5 (3 independent experiments). *P < 0.05 compared with indicated group by 1-way ANOVA (with Tukey’s post hoc test).