CAP2 promotes gastric cancer metastasis by mediating the interaction between tumor cells and tumor-associated macrophages
Guohao Zhang, Zhaoxin Gao, Xiangyu Guo, Ranran Ma, Xiaojie Wang, Pan Zhou, Chunlan Li, Zhiyuan Tang, Ruinan Zhao, Peng Gao
Guohao Zhang, Zhaoxin Gao, Xiangyu Guo, Ranran Ma, Xiaojie Wang, Pan Zhou, Chunlan Li, Zhiyuan Tang, Ruinan Zhao, Peng Gao
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Research Article Gastroenterology Oncology

CAP2 promotes gastric cancer metastasis by mediating the interaction between tumor cells and tumor-associated macrophages

Abstract

The metastasis of cancer cells is the main cause of death in patients with gastric cancer (GC). Mounting evidence has demonstrated the vital importance of tumor-associated macrophages in promoting tumor invasion and metastasis; however, the interaction between tumor cells and macrophages in GC is largely unknown. In this study, we demonstrated that cyclase-associated protein 2 (CAP2) was upregulated in GC, especially in cases with lymph node metastasis, and was correlated with a poorer prognosis. The transcription factor JUN directly bound to the promoter region of CAP2 and activated CAP2 transcription. The N-terminal domain of CAP2 bound to the WD5 to WD7 domains of receptor for activated C kinase 1 (RACK1) and induced M2 macrophage polarization by activating the SRC/focal adhesion kinase (FAK)/ERK signaling pathway, which resulted in IL-4 and IL-10 secretion. Polarized M2 macrophages induced premetastatic niche formation and promoted GC metastasis by secreting TGFB1, which created a TGFB1/JUN/CAP2 positive-feedback loop to activate CAP2 expression continuously. Furthermore, we identified salvianolic acid B as an inhibitor of CAP2, which effectively inhibited GC cell invasion capabilities by suppressing the SRC/FAK/ERK signaling pathway. Our data suggest that CAP2, a key molecule mediating the interaction between GC cells and tumor-associated macrophages, may be a promising therapeutic target for suppressing tumor metastasis in GC.

Authors

Guohao Zhang, Zhaoxin Gao, Xiangyu Guo, Ranran Ma, Xiaojie Wang, Pan Zhou, Chunlan Li, Zhiyuan Tang, Ruinan Zhao, Peng Gao

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Figure 4

CAP2 binds to RACK1 and activates the FAK/MEK/ERK axis.

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CAP2 binds to RACK1 and activates the FAK/MEK/ERK axis. (A) Pull-down ex...
(A) Pull-down experiments were performed on lysates from MKN45 cells using GST-CAP2 or GST-tagged proteins, followed by gel electrophoresis. Liquid chromatography–tandem mass spectrometry (LC-MS/MS) was performed on 30- to 70-kDa proteins. (B) Cell lysates were immunoprecipitated with anti-CAP2 or IgG. The co-IP elutions were silver-stained, and all coimmunoprecipitated proteins were analyzed by LC-MS/MS. (C) In vitro binding between RACK1 and GST-CAP2 was analyzed by GST pull-down assays. (D) Co-IP showed that RACK1 was immunoprecipitated by CAP2, rather than ANXA2, MDH2, or GAPDH. (E) Immunofluorescence analysis showed the CAP2/RACK1 colocalization in MKN45 cells. Scale bars: 10 μm; 2 μm (right). (F) Effects of CAP2 on FAK/MEK/ERK signaling pathway in GC cells were detected by Western blot. (G and H) Effects of CAP2 on the binding strength of RACK1/FAK complex were detected by co-IP assays. (I) Effects of CAP2 and RACK1 on FAK/MEK/ERK signaling pathway were detected by Western blot. (J) The migration ability of GC cell lines was determined by Transwell assay. Scale bars: 50 μm (n = 4). **P < 0.01, ***P < 0.001). Data are presented as the mean ± SD. One-way ANOVA with Tukey’s multiple-comparison test (J).