Prostate secretory protein of 94 amino acids (PSP94), also known as β-microseminoprotein or prostatic inhibin-like protein, is a small, nonglycosylated peptide consisting of 94 amino acids with molecular mass 10.7 kDa, and is one of the major secretory proteins of the prostate glands. PSP94 is synthesized as a preprotein of 114 amino acid residues, from which a 20– residue signal peptide is cleaved off to form the mature protein. PSP94 along with PSA (Prostate-specific Antigen) and PAP (Prostate Acid Phosphatase) are the three most abundant proteins in seminal fluid. As with other prostate-secreted proteins, PSP94 can leak into the blood upon benign or malignant prostate epithelial disruption and can be measured within serum. PSP94 is not solely synthesized by the prostate epithelium, as the protein can also be detected in nonreproductive organs such as in the respiratory and gastrointestinal tracts, of which, the gastric mucosa shows particularly high expression. Accordingly, PSP94 can be measured in serum of both men and women, but the serum levels in women were found to be around two-thirds of those measured in men. PSP94 forms high-affinity complexes with two related Cys-rich proteins: PSP94-binding protein in blood plasma and cysteine-rich secretory protein 3 (CRISP-3) in semen. Evidence suggest that PSP94 has systemic functions including growth regulation and induction of apoptosis in prostate cancer cells in vitro and in vivo, and regulation of calcium levels during hypercalcemia secondary to malignancy. Several studies have demonstrated a progressive decrease in PSP94 expression as prostate cancer progresses from a hormone-dependent to a hormone-independent state with complete lack of PSP94 production in highly advanced metastatic prostate cancer. This differential expression could make PSP94 a prognostic clinical marker for prostate cancer and could help distinguish patients with aggressive forms of prostate cancer. A recent study demonstrated a close correlation between PSP94 in serum and seminal plasma, supporting the potential use of PSP94 as a serum marker of prostate secretory function as well. Clusterin (Apolippoprotein J; SP-40,40; TRPM-2; SGP-2; pADHC-9; CLJ; T64; GP III; XIP8) is a highly conserved disulfide-linked secreted heterodimeric glycoprotein of 75–80 kDa but truncated forms targeted to nucleus have also been identified. The protein is constitutively secreted by a number of cell types including epithelial and neuronal cells and is a major protein in physiological fluids including plasma, milk, urine, cerebrospinal fluid and semen. Due to its wide tissue distribution many diverse physiological functions have been attributed to clusterin including sperm maturation, membrane recycling, lipid transportation, tissue remodeling, complement inhibition and cell-cell or cell-substratum interactions. Moreover, it was propose, that clusterin functions is as an extra cellular chaperon that stabilizes stressed proteins in a folding-competent state and protein has also been implicated in programmed cell death. Another defining prominent of clusterin is its induction in many severe physiological disturbances states including kidney degenerative diseases, prostate and vesicle carcinogenesis, ovarian cancer and several neurodegenerative conditions (Alzheimer’s disease). Recent study demonstrate, that serum clusterin level increases significantly in diabetic type II patients and in patients with developing coronary heart disease, or myocardial infarction. These date raise the possibility that elevated clusterin levels in serum may represent a strong indication of vascular damage. In patients with systemic lupus erythematosus (SLE) was found reduced serum clusterin levels that correlated inversely with disease activity. Lowered clusterin levels could be involved in the pathogeneses of SLE on account of decreased protective effects. Another interesting observations obtain in rat model suggest that measurement of
- References to Prostate Cancer Panel