SR Analysis of Tissues

Abstract

A human prostate gland has a unique feature of possessing high level accumulation of zinc compared to other organs. In prostate cancer tissue, this unique zinc metabolism is altered resulting in the decrease of zinc level in the epithelial cells [1,2]. Zinc accumulation in glandular cells is relevant to the citrate metabolism in the citric acid cycle (Krebs cycle). The citric acid cycle is a series of biochemical reactions, which involve the energy metabolism in the cells [3]. Via the cycle citrate is oxidized and isomerized into isocitrate by an enzyme, aconitase. Zinc inhibits the activity of aconitase, resulting in inhibition of the citrate oxidation [4]. Citrate is also abundant in a prostate gland, which has the unique function of secretion [5]. A high level of zinc may involve the regulation of citrate oxidation in a prostate gland. In a prostate cancer tissue, citrate is remarkably decreased as well as the level of zinc. The question arises as how the reduction of zinc level involves the progression of malignancy in prostate cancer tissue. As one possibility, Costello et al. have suggested that excessive citrate oxidation result in production of coupled ATP, which is essential for the progression of malignancy [6,7]. On the other hand, a hormone is closely related with the zinc level and malignancy in a prostate tissue. Inhibition of phosphatidylinositol 3-kinase induces cellular apoptosis. Androgen inhibits this pathway, i.e., androgen inhibits apoptosis [8]. Zn²⁺ induces stimulation of phosphoinositide 3-kinase [9], thereby zinc inhibits apoptosis.Apoptosis is a mechanism of programmed death of cell,and deficient apoptosis is related to the progression of malignancy.