e15570 Background: We have previously discovered a relationship between the low expression of protein tyrosine phosphatase, receptor type O (PTPRO) in tumor-infiltrating T cells and immunosuppression. The aim of the present study was to investigate the relationship between decreased PTPRO and increased programmed death ligand 1 (PD-L1) in both the peripheral monocytes and tumor-infiltrating macrophages of human breast cancer (BC). Methods: The expression and correlation of all the indices were explored in monocytes and tumor infiltrating macrophages within both human and mice BC. The mechanic regulations were studied by using both in vitro and in vivo studies. Results: We found a significant decrease in PTPRO in BC peripheral monocytes that was associated with increased PD-L1 expression in peripheral monocytes and tumor-associated macrophages (TAMs) in BC. Monocyte PD-L1 and PTPRO therefore could serve as valuable prognostic indicators for post-surgery patients with BC and were associated with increased T cell exhaustion (Tim3+ T cells). A depletion of PTPRO promoted PD-L1 secretion in both monocytes and macrophages through the JAK2/STAT1 and JAK2/STAT3/c-MYC pathways. Increased IL-6 expression was associated with activation of JAK2/STAT3/c-MYC and with decreased PTPRO expression through the STAT3/c-MYC/miR-25-3p axis. Monocytes and TAMs showed significantly increased miR-25-3p expression, which could target the 3' untranslated region of PTPRO. The miR-25-3p expression positively correlated with serum IL-6 levels, but inversely correlated with PTPRO in BC monocytes. IL-6/STAT3/c-MYC activation enhanced in vitro miR-25-3p transcription and decreased PTPRO, while further promoting PD-L1 secretion. Adoptive cell transfer of c-MYC/miR-25-3p–modified monocytes promoted tumor growth by downregulating PTPRO and causing a PD-L1–induced immunosuppression in breast tumor model. Conclusions: Increased serum IL-6 downregulated PTPRO expression in BC monocytes and macrophages by activating STAT3/c-MYC/miR-25-3p and by further enhancing PD-L1 expression through JAK2/STAT1 and JAK2/STAT3/c-MYC signaling.
Loss of protein tyrosine phosphatase, non-receptor type 2 is associated with activation of AKT and tamoxifen resistance in breast cancer