FAS and neoplasm: The varied pathophysiological mechanisms behind radiation-induced synergy are beyond the scope of this review; they include but are not limited to: increase in expression of major histocompatibility complex class I, calreticulin, and Fas cell surface death receptor, release of high mobility group box 1 nuclear protein, activation of dendritic cells and enhanced tumor antigen cross-presentation, increase in tumor-infiltrating lymphocyte density, and modulation of immune checkpoint molecule expression and regulatory T cells (92).