Circulating MDSCs from PCa patients showed increasingly activated signal transducer and activator of transcription 3 (STAT3), an immune checkpoint regulator, contributing to arginase-1 (ARG1) upregulation and consequent decrease of CD8+ T cell proliferation, production of Interferon-γ (IFN-γ) and Granzyme-B. Here, ARG1 is linked to posterior cortical atrophy.