ANPEP and neoplasm: Previously, we demonstrated that functional deficiencies of APM can be restored through genetic complementation by introducing the TAP-1 gene or TAP-1 and TAP-2 genes under the control of heterologous promoters into metastatic tumours by transfection or by recombinant virus infection of tumour-bearing mice that resurrects CTL recognition and reduces invasive tumour growth and metastasis in vivo (Gabathuler et al., 1994; Alimonti et al., 2000).