UCP2 and renal cell carcinoma: Similar to the upregulation of UCP-3 by RCC in the present study, other UCPs such as UCP-1, UCP-2, UCP-4 or UCP-5 are reportedly upregulated in a number of aggressive human tumors (leukemia, breast-, colorectal-, ovarian-, bladder-, esophagus-, testicular-, kidney-, pancreatic-, lung-, and prostate cancer) where they are proposed to contribute to the malignant progression of tumors (for review see Ref.