Glufosinate constrains synchronous and metachronous metastasis by promoting anti-tumor macrophages.

Alessio Menga,Paolo E Porporato,Massimiliano Mazzone,Manuel Ehling,Alessandra Castegna,Rosanna Gissi,Maria Antonietta Di Noia,Carla Riera‐Domingo,Marina Serra,Simona Todisco,Erika M Palmieri,Maria Favia,Ummi Ammarah,Ciro L Pierri

doi:10.15252/emmm.201911210

Abstract

Glutamine synthetase (GS) generates glutamine from glutamate and controls the release of inflammatory mediators. In macrophages, GS activity, driven by IL10, associates to the acquisition of M2‐like functions. Conditional deletion of GS in macrophages inhibits metastasis by boosting the formation of anti‐tumor, M1‐like, tumor‐associated macrophages (TAMs). From this basis, we evaluated the pharmacological potential of GS inhibitors in targeting metastasis, identifying glufosinate as a specific human GS inhibitor. Glufosinate was tested in both cultured macrophages and on mice bearing metastatic lung, skin and breast cancer. We found that glufosinate rewires macrophages toward an M1‐like phenotype both at the primary tumor and metastatic site, countering immunosuppression and promoting vessel sprouting. This was also accompanied to a reduction in cancer cell intravasation and extravasation, leading to synchronous and metachronous metastasis growth inhibition, but no effects on primary tumor growth. Glufosinate treatment was well‐tolerated, without liver and brain toxicity, nor hematopoietic defects. These results identify GS as a druggable enzyme to rewire macrophage functions and highlight the potential of targeting metabolic checkpoints in macrophages to treat cancer metastasis.

Highlights

Glutamine synthetase (GS) generates glutamine from glutamate and controls the release of inflammatory mediators
In the effort to dissect which pathways underline the phenotypic switch in tumor-associated macrophages (TAMs), we have discovered that targeting glutamine synthetase (GS; a.k.a. glutamate ammonia ligase, GLUL, EC 6.3.1.2) in macrophages represents an effective way to reprogram in vitro IL10-stimulated macrophages and TAMs toward a desirable “M1-like function”
Since it is known that M2-like macrophages support cancer cell migration (Joyce & Pollard, 2009), we evaluated the extent of cancer motility through 8 lm-pores in presence of macrophages treated for 24 h with IL10 versus glufosinate/or Methionine sulfoximine (MSO)/IL10

Summary

Introduction

Glutamine synthetase (GS) generates glutamine from glutamate and controls the release of inflammatory mediators. Conditional deletion of GS in macrophages inhibits metastasis by boosting the formation of anti-tumor, M1-like, tumor-associated macrophages (TAMs) From this basis, we evaluated the pharmacological potential of GS inhibitors in targeting metastasis, identifying glufosinate as a specific human GS inhibitor. We found that glufosinate rewires macrophages toward an M1-like phenotype both at the primary tumor and metastatic site, countering immunosuppression and promoting vessel sprouting This was accompanied to a reduction in cancer cell intravasation and extravasation, leading to synchronous and metachronous metastasis growth inhibition, but no effects on primary tumor growth. Glufosinate treatment was welltolerated, without liver and brain toxicity, nor hematopoietic defects These results identify GS as a druggable enzyme to rewire macrophage functions and highlight the potential of targeting metabolic checkpoints in macrophages to treat cancer metastasis

Methods

Results

Conclusion