Lung Cancer Cells-Controlled Dkk-1 Production in Brain Metastatic Cascade Drive Microglia to Acquire a Pro-tumorigenic Phenotype.

Abstract

OBJECTIVES:

Organotropism is primarily determined by tumor-derived exosomes. To date, the role of lung cancer cells-derived exosomes underlying the pre-metastatic niche formation is unclear.

MATERIALS AND METHODS:

The animal models of retro-orbital and intra-ventricular injection were constructed to administrate lung cancer cells-derived exosomes. Cytokine array was used to screen the cytokines released from brain endothelium after internalization of lung cancer cells-derived exosomes. The cellular co-culture system was established to mimic microglia-vascular niche contained lung cancer cells-derived exosomes. The levels of Dkk-1 and the activities of microglia were analyzed by qRT-PCR, western blot and immunofluorescence. In vivo selections of highly brain metastatic cells were performed to analyze the direct interaction of lung cancer cells with microglia.

RESULTS:

Animal studies demonstrated that there was a suppressive signal transferred from brain endothelium to microglia after internalization of lung cancer cells-derived exosomes into brain endothelium, which caused an absolutely less M1 phenotypic microglia and a relatively more M2 phenotypic microglia. Further results indicated that lung cancer cells-derived exosomes induced a release of endogenous Dkk-1 from brain endothelium, which rendered microglia to acquire a pro-tumorigenic feature in pre-metastatic niche. Subsequently, the declines of Dkk-1 in metastatic lung cancer cells removed the suppression on microglia and enhanced microglial activation in metastatic niche.

CONCLUSION:

Our findings shed a new light on the synergistic reaction of the different cells in "neurovascular units" toward the metastatic messages from lung cancer cells and provided a potential therapeutic pathway for lung cancer metastasis to brain.

• Authors: Dong-Xue Gan, Yi-Bei Wang, Ming-Yang He, Zi-Yang Chen, Xiao-Xue Qin, Zi-Wei Miao, Yu-Hua Chen, Bo Li
• Journal: Frontiers in cell and developmental biology (Front Cell Dev Biol) Vol. 8 Pg. 591405 ( 2020) ISSN: 2296-634X [Print] Switzerland
• PMID: 33384994 (Publication Type: Journal Article)
• Copyright: Copyright © 2020 Gan, Wang, He, Chen, Qin, Miao, Chen and Li.