Alveolar macrophage secretion of vesicular SOCS3 represents a platform for lung cancer therapeutics
Jennifer M. Speth, Loka R. Penke, Joseph D. Bazzill, Kyung Soo Park, Rafael Gil de Rubio, Daniel J. Schneider, Hideyasu Ouchi, James J. Moon, Venkateshwar G. Keshamouni, Rachel L. Zemans, Vibha N. Lama, Douglas A. Arenberg, Marc Peters-Golden
Jennifer M. Speth, Loka R. Penke, Joseph D. Bazzill, Kyung Soo Park, Rafael Gil de Rubio, Daniel J. Schneider, Hideyasu Ouchi, James J. Moon, Venkateshwar G. Keshamouni, Rachel L. Zemans, Vibha N. Lama, Douglas A. Arenberg, Marc Peters-Golden
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Research Article Immunology Oncology

Alveolar macrophage secretion of vesicular SOCS3 represents a platform for lung cancer therapeutics

Abstract

Lung cancer remains the leading cause of cancer-related death in the United States. Although the alveolar macrophage (AM) comprises the major resident immune cell in the lung, few studies have investigated its role in lung cancer development. We recently discovered a potentially novel mechanism wherein AMs regulate STAT-induced inflammatory responses in neighboring epithelial cells (ECs) via secretion and delivery of suppressors of cytokine signaling 3 (SOCS3) within extracellular vesicles (EVs). Here, we explored the impact of SOCS3 transfer on EC tumorigenesis and the integrity of AM SOCS3 secretion during development of lung cancer. AM-derived EVs containing SOCS3 inhibited STAT3 activation as well as proliferation and survival of lung adenocarcinoma cells. Levels of secreted SOCS3 were diminished in lungs of patients with non–small cell lung cancer and in a mouse model of lung cancer, and the impaired ability of murine AMs to secrete SOCS3 within EVs preceded the development of lung tumors. Loss of this homeostatic brake on tumorigenesis prompted our effort to “rescue” it. Provision of recombinant SOCS3 loaded within synthetic liposomes inhibited proliferation and survival of lung adenocarcinoma cells in vitro as well as malignant transformation of normal ECs. Intratumoral injection of SOCS3 liposomes attenuated tumor growth in a lung cancer xenograft model. This work identifies AM-derived vesicular SOCS3 as an endogenous antitumor mechanism that is disrupted within the tumor microenvironment and whose rescue by synthetic liposomes can be leveraged as a potential therapeutic strategy for lung cancer.

Authors

Jennifer M. Speth, Loka R. Penke, Joseph D. Bazzill, Kyung Soo Park, Rafael Gil de Rubio, Daniel J. Schneider, Hideyasu Ouchi, James J. Moon, Venkateshwar G. Keshamouni, Rachel L. Zemans, Vibha N. Lama, Douglas A. Arenberg, Marc Peters-Golden

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Figure 1

AM-derived EVs inhibit tumor cell function.

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AM-derived EVs inhibit tumor cell function. (A) Normal AECs (L2) or A549...
(A) Normal AECs (L2) or A549 adenocarcinoma cells were incubated with either medium alone (control, C) or PKH26-labeled AM-derived EVs for 1 hour (h); EV uptake was determined by flow cytometry and expressed as mean fluorescence intensity (MFI) (n = 3 separate experiments). (B and C) Cells were pretreated with EVs for 2 h, washed, and stimulated with 10 ng/ml IL-6 for 30 minutes, and lysates were analyzed for pSTAT3 and total STAT3 by WB (n = 3 separate experiments). A representative WB (B) and densitometric analysis of multiple such experiments, represented as relative pSTAT3 protein (C), are shown. (D) A549 cells were incubated with AM EVs for 72 h and subjected to CyQuant cell proliferation assay measuring total cellular DNA (n = 3 separate experiments). (E) A549 cells were treated with FasL (as a positive control) or AM EVs for 24 h, and apoptotic cells were determined by annexin V+ staining via flow cytometry (n = 3–5 replicates). (F) A549 cells were treated with AM EVs or FasL for 72 h, with or without the pan-caspase inhibitor Z-VAD-FMK (Z), and cell proliferation was determined using CyQuant assay (n = 6–14 replicates from 3 separate experiments). Student’s 2-tailed t test was used for comparison of 2 groups (C and D) or 1-way ANOVA with Bonferroni’s post hoc analysis was used for multiple comparisons (E and F); *P < 0.05.