ABUNDANT CYSTEINE-RICH PROTEIN-1 IS LOCALIZED IN THE STROMAL COMPARTMENT OF THE HUMAN PROSTATE

The cysteine-rich protein-1 (CRP1) is one of the major proteins of the human prostate. Because of the suspected importance of that protein i n cell proliferation and differentiation, its expression was investiga ted in the prostate, prostatic cancer cells, and other organs of the b ody. At the mRNA level, the highest concentrations of CRP1 were found in the prostate and the colon followed by the brain and the testis. It was virtually absent from the spleen, liver, heart, and kidney. Prost atic cancer cells PC-3, DU-145, and LNCaP also expressed CRP1 mRNA but virtually no protein. CRP1 protein localization in tissues was determ ined by immunohistochemical analysis using polyclonal antibodies devel oped against recombinant CRP1 protein. Strong positive cytoplasmic imm unoreactions were observed only in the stromal compartment of the pros tate and of other smooth muscle-rich tissues without significant stain ing in any secretory epithelium. These results, along with previously reported data of colocalization of CRP1 with stress fibers and adhesio n plaques, suggest that the main function of CRP1 may be structural.