ActivatedKRASsignaling triggers malignant pleural effusion

Abstract

Background: EGFR/KRAS axis mutations are frequent in human malignantpleuraleffusions (MPE). Aims: To investigate the relationship between perturbations in the EGFR-KRAS axis and malignant pleural effusion development. Methods: Several mouse and human cancer cell lines were characterized for EGFR/KRAS status and for their MPE competence in appropriate hosts. EGFR/KRAS signalling was modulated in various cell lines via standard molecular techniques. MPE-associated inflammation was monitored by bioluminescence imaging, immunophenotyped by flow cytometry, and modulated by splenectomy and adoptive bone marrow transfer. EGFR/KRAS axis was targeted using gefitinib, deltarasin, and anti-CCL2 antibodies. Results: A causative relationship between Δ Kras and MPEwas established by showing that mouse and human cancer cell lines bearing Δ Kras are MPE competent and that activated Kras is capable of conferring MPE competency to human and mouse cells. Furthermore, Kras dependent downstream paracrine signaling to bone marrow activated a distinct GR1+/CD11B+ myeloid cell population, which is maturing in the spleen and is consequently recruited to the pleural cavity in a cancer-elaborated CCL2-dependent way. Splenectomy partially protects hosts from MPE. The pharmacological manipulation of Δ EGFR/ Δ KRAS axis with Gefitinib (targeting Δ EGFR ) or Deltarasin (targeting Δ KRAS ) and the antibody-mediated neutralization of CCL2 completely annihilate MPE formation and the recruitment of CD11b+/GR1+ cells to the pleura. Conclusions: Our work provides insights to MPE pathobiology and a multitude of strategies to target a currently untreatable terminal human condition. Funding: European Research Council Starting Independent Investigator Grant #260524.