Lysyl-tRNA synthetase–expressing colon spheroids induce M2 macrophage polarization to promote metastasis
Seo Hee Nam, … , Sunghoon Kim, Jung Weon Lee
Seo Hee Nam, … , Sunghoon Kim, Jung Weon Lee
Published November 1, 2018; First published September 6, 2018
Citation Information: J Clin Invest. 2018;128(11):5034-5055. https://doi.org/10.1172/JCI99806.
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Research Article Gastroenterology Oncology

Lysyl-tRNA synthetase–expressing colon spheroids induce M2 macrophage polarization to promote metastasis

Abstract

Lysyl-tRNA synthetase (KRS) functions canonically in cytosolic translational processes. However, KRS is highly expressed in colon cancer, and localizes to distinct cellular compartments upon phosphorylations (i.e., the plasma membranes after T52 phosphorylation and the nucleus after S207 phosphorylation), leading to probably alternative noncanonical functions. It is unknown how other subcellular KRSs crosstalk with environmental cues during cancer progression. Here, we demonstrate that the KRS-dependent metastatic behavior of colon cancer spheroids within 3D gels requires communication between cellular molecules and extracellular soluble factors and neighboring cells. Membranous KRS and nuclear KRS were found to participate in invasive cell dissemination of colon cancer spheroids in 3D gels. Cancer spheroids secreted GAS6 via a KRS-dependent mechanism and caused the M2 polarization of macrophages, which activated the neighboring cells via secretion of FGF2/GROα/M-CSF to promote cancer dissemination under environmental remodeling via fibroblast-mediated laminin production. Analyses of tissues from clinical colon cancer patients and Krs–/+ animal models for cancer metastasis supported the roles of KRS, GAS6, and M2 macrophages in KRS-dependent positive feedback between tumors and environmental factors. Altogether, KRS in colon cancer cells remodels the microenvironment to promote metastasis, which can thus be therapeutically targeted at these bidirectional KRS-dependent communications of cancer spheroids with environmental cues.

Authors

Seo Hee Nam, Doyeun Kim, Doohyung Lee, Hye-Mi Lee, Dae-Geun Song, Jae Woo Jung, Ji Eon Kim, Hye-Jin Kim, Nam Hoon Kwon, Eun-Kyeong Jo, Sunghoon Kim, Jung Weon Lee

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Figure 7

Nuclear KRS causes transcriptional activation of the GAS6 promoter regions by MiTF.

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Nuclear KRS causes transcriptional activation of the GAS6 promoter regio...
(A) Putative MiTF or c-Jun binding sites in the GAS6 promoter region. (B) HCT116 spheroids embedded in 3D collagen I gels for 24 hours (shControl, shKRS#2, and shKRS#2 treated with M2 macrophage-CM) were processed for ChIP analysis. Antibodies against MiTF or c-Jun were used to examine binding to regions (1, 2, and 3) in the GAS6 promoter. (C–E) HCT116 spheroids in 3D collagen I gels were treated with the CM of control THP-1 or M2 macrophages, before analysis of KRS expression following cellular fractionations (C), mRNA levels of KRS or GAS6 (D), and protein levels of GAS6 and other aminoacyl-tRNA synthetases (E). EPRS, glutamyl-prolyl-tRNA synthetase; DRS, aspartyl-tRNA synthetase; LRS, leucyl-tRNA synthetase; MRS, methionyl-tRNA synthetase. The data are presented as the mean ± SD. ***P < 0.001 by 1-way ANOVA with Dunnett tests (D)., The data shown represent 3 different observations. See also Supplemental Figure 6.