Journal
CELL COMMUNICATION AND SIGNALING
Volume 13, Issue -, Pages -Publisher
BMC
DOI: 10.1186/s12964-015-0093-y
Keywords
Immune checkpoint PD-L1; Bone marrow derived cells; Tumor microenvironment; CD11b; Chemotherapy resistance
Categories
Funding
- National Cancer Institute [RO1 CA120895]
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Background: Expression of programmed cell death ligand 1 (PD-L1) is an important process by which tumor cells suppress antitumor immunity in the tumor microenvironment. Bone marrow (BM)-derived immune cells are an important component of the tumor microenvironment. However, the link between PD-L1 induction on tumor cells and communication with BM cells is unknown. Results: This study demonstrates that BM cells have a direct effect in inducing PD-L1 expression on tumor cells, which contributes to the tumor cells' drug resistance. This novel discovery was revealed using a co-incubation system with BM cells and tumor cells. BM cells from wild-type C57BL6 mice and the immune-deficient mouse strains B-cell(-/-), CD28(-/-), perforin(-/-), and Rag2(-/-) but not CD11b(-/-) dramatically increased the expression of tumor cell surface PD-L1. This PD-L1 induction was dependent on CD11b-positive BM cells through direct contact with tumor cells. Furthermore, p38 signaling was activated in tumor cells after co-incubation with BM cells, whereas the expression of PD-L1 was remarkably decreased after co-culture of cells treated with a p38 inhibitor. The increase in PD-L1 induced by BM cell co-culture protected tumor cells from drug-induced apoptosis. Conclusions: PD-L1 expression is increased on tumor cells by direct contact with BM-derived CD11b-positive cells through the p38 signaling pathway. PD-L1 may play an important role in drug resistance, which often causes failure of the antitumor response.
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