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 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 2

M2 macrophage–produced cytokines promote signaling activities for disseminative outgrowths from membranous KRS–positive spheroids in 3D gels.

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M2 macrophage–produced cytokines promote signaling activities for dissem...
(A) Diagram indicating cytokine production by macrophages differentiated from THP-1 cells. (B) Vehicle (control) or cytokines that were shown to be produced preferentially by M2 macrophages were administered to KRS-positive and KRS-suppressed spheroids embedded in 3D collagen I gels, before time-lapse imaging for 40 hours (1d:16h:00min). Snap images for the starting and ending points are presented. Spheroid images include yellow fractions to depict the phenotypes (numerator) out of total spheroids (denominator) analyzed. Scale bars: 40 μm. (C–E) HCT116-shControl (P), HCT116-shKRS#2 (#2), or HCT116-KRS-WT (WT) spheroids were treated with cytokines (C); CM from control, THP-1 monocytes, THP-1 differentiated M1 macrophages, or THP-1 differentiated M2 macrophages (D); or GROα or M-CSF (E), as explained in Methods. One day after, whole cell extracts were prepared for immunoblotting. The data shown represent 3 independent experiments. See also Supplemental Figure 3.