ANPEP and metastatic malignant neoplasm: Previous work in the field has shown that MHC-I expression can be re-established in metastatic cancer through the use of cytokines such as interferon-γ (IFN-γ) (Jefferies et al., 1993a; Gabathuler et al., 1994; Alimonti et al., 2000; Diedrich et al., 2001; Shankaran et al., 2001) and interleukin-33 (Saranchova et al., 2016) or by genetic complementation with the missing APM components (Gabathuler et al., 1994; Alimonti et al., 2000; Setiadi et al., 2005a; Saranchova et al., 2016).