PC1/3 KD Macrophages Exhibit Resistance to the Inhibitory Effect of IL-10 and a Higher TLR4 Activation Rate, Leading to an Anti-Tumoral Phenotype

Abstract

During tumorigenesis, macrophages are recruited by tumors and orientated towards a pro-tumoral phenotype. One of the main anti-tumoral immunotherapy consists of their re-polarization in an anti-tumoral phenotype. We have demonstrated that the inhibition of proprotein convertase 1/3 combined with TLR4 activation in macrophages is a promising strategy. These macrophages display pro-inflammatory and anti-tumoral phenotypes. A hallmark is a stronger activation of the pro-inflammatory NFKB pathway. We believe that this can be explained by a modification of TLR4 expression at the cell surface or MYD88 cleavage since it exhibits a potential cleavage site for proprotein convertases. We tested these hypotheses through immunofluorescence and Western blot experiments. A proteomics study was also performed to test the sensitivity of these macrophages to IL-10. We demonstrated that these macrophages treated with LPS showed a quicker re-expression of TLR4 at the cell surface. The level of MYD88 was also higher when TLR4 was internalized. Moreover, these macrophages were resistant to the pro-tumoral effect of IL-10 and still produced pro-inflammatory factors. This established that the sensitivity to anti-inflammatory molecules and the length of TLR4 desensitization were reduced in these macrophages. Therefore, during antitumoral immunotherapy, a repeated stimulation of TLR4 may reactivate PC1/3 inhibited macrophages even in an anti-inflammatory environment.

COLEC12 regulates apoptosis of osteosarcoma through Toll‐like receptor 4–activated inflammation

“…28 TLR4 was pivotal promoter of inflammation which related NF-kB and C3 signaling, and then released TNF-α and ILs, which can induce apoptosis of osteosarcoma cells. 10,11,31,32 However, whether the role of COLEC12 for inflammation in osteosarcoma is regulated by TLR4…”

The Role of Proprotein Convertases in the Regulation of the Function of Immune Cells in the Oncoimmune Response

“…This revealed an essential role of PC1/3 in TLR4 trafficking. An over-expression of MYD88 was also observed in PC1/3 KD macrophages treated with LPS ( 36 ) ( Figure 3 ). As a consequence, a longer activation of the NF-κB signaling pathway was observed ( 28 ).…”

“…Following LPS stimulation, PC1/3 trafficked with TLR4 ( 27 ). Of note, PC1/3 knock down led to a quicker recycling of TLR4 at the cell surface ( 36 ) ( Figure 3 ). This revealed an essential role of PC1/3 in TLR4 trafficking.…”

Therapeutic anti-glioma effect of the combined action of PCSK inhibitor with the anti-tumoral factors secreted by Poly (I:C)-stimulated macrophages

“…In this context, it has been demonstrated that Furin and the proprotein convertase 1/3 (PC1/3) are two complementary targets for reinforcing the immune response [23][24][25][26][27][28][29][30]. Furin is critical for the maintenance of peripheral CD4 + Foxp3 + T regulatory cell-dependent immune tolerance and normal CD4 + T helper (Th) cell polarization in vivo [30,31].…”

“…We established that PC1/ 3 KD macrophages secrete high quantities of extracellular vesicles (EVs) [25,27,29] which is even more important when TLR4 or TLR9 pathways are triggered in PC1/3 KD macrophages [27,28]. PC1/3 modulates GRAMD4 levels and thus regulate TLR9 trafficking, to modulate the inflammatory response [29]. Its inhibition reactivates the pro-inflammatory TLR MYD88 NFKB dependent pathway while the anti-inflammatory STAT3 pathway is downregulated [29].…”