APN has also been described as a cancer-specific biomarker and reported to be involved in the progression of tumour metastasis, angiogenesis and prognosis, as well as protein overexpression in cancer cells, while tissue invasion and metastasis in human prostate cancer could be attenuated by using Zn2+ to inhibit APN biological activity in a dose-dependent manner [95–97]. The gene discussed is ANPEP; the disease is prostate cancer.