HMGB1 and leiomyosarcoma: High-mobility group box 1 (HMGB1) is a protein released from cells as a result of immunogenic cell death and can be isolated in plasma; HMGB1 was recently studied as a potential biomarker in a Phase 1b clinical trial treating patients with advanced leiomyosarcoma (LMS) with doxorubicin, dacarbazine, and an ICI, nivolumab [36, 37].