SIRP? Suppresses Response to Therapeutic Antibodies by Nurse Like Cells From Chronic Lymphocytic Leukemia Patients.

ABSTRACT: Targeted antibody therapies improve outcomes for chronic lymphocytic leukemia (CLL) patients. However, resistance often develops. We have previously shown that resistance to therapeutic antibodies, by monocyte derived macrophages (referred to as nurse like cells, NLCs), from CLL patients is characterized by suppression of antibody dependent phagocytosis (ADP). The mechanism(s) contributing to the muted ADP responses remain unresolved. In this regard, an innate immune checkpoint was recently described that uses the CD47:SIRP? axis to suppress phagocytic responses by macrophages. In this study we examine whether the SIRP? axis regulates ADP responses to the anti-CD20 antibody, obinutuzumab, by NLCs. Using siRNA depletion strategies we show that SIRP? is a suppressor of ADP responses. Moreover, we show that this innate immune checkpoint contributes to the resistance phenotype in NLCs derived from CLL patients. Finally, we show that SIRP? suppression is mediated via the phosphatase, Shp1, which in turn suppresses SYK-dependent activation of ADP. Thus, we identify a druggable pathway that could be exploited to enhance sensitivity to existing therapeutic antibodies used in CLL. This is the first study to show that activation of the CD47:SIRP? innate immune checkpoint contributes to ADP resistance in NLCs from CLL patients.

SUBMITTER: Chen YE 

PROVIDER: S-EPMC7859087 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature