PD-1 Targeting, Macrophage Infiltration, and IDO Pathway Activation in Patients With Sarcomas

To the Editor We read with interest the article by Toulmonde and colleagues assessing the efficacy and safety of anti–programmed cell death protein 1 (PD-1) antibody and metronomic cyclophosphamide in patients with advanced soft-tissue sarcomas. We found the rationale of this combination approach interesting and worthy of further investigation, despite their unfavorable clinical data. The choice to measure the PD-1 ligand (PD-L1) as a possible predictive parameter of immunotherapy may partially explain their negative results. In fact, PD-1 expression is clear evidence of lymphocyte activation after recognition of immunogenic, that is, tumor, antigen. Conversely, PD-L1 level may reflect only expression of its production by the tumor or tumor-associated macrophages, which, however, can be activated also and exclusively by necrosis.

https://ift.tt/2lbLPZU