APP and neoplasm: Among all tumor types represented in the Cancer Cell Line Encyclopedia (Barretina et al., 2012), SCLC and neuroblastoma exhibit the lowest expression of multiple MHC-I APP genes, implying broad repression of the MHC-I APP in these neuroendocrine tumors (Figures 1F and S1E) (Restifo et al., 1993, Bernards et al., 1986).