Uridine phosphorylase has a dual role in cancer and is secreted by tumor cells in marginally invasive regions of tumors, especially in those in which TP53 (negative regulator of uridine phosphorylase) is inactivated, and in macrophages in tumor stroma, by a mechanism that includes TNFA and NF-kB, but also by some bacteria, such as Escherichia coli and Parabacteroides distasonis (86). The gene discussed is UPP1; the disease is neoplasm.