en Immunology Immunology Original Research: Basic Science in Medicine Original Research: Basic Science in Medicine PSA is a 33-KDa serine protease that is produced predominantly by prostate epithelium. However, it has been shown that about 30-40% of female breast tumors produce PSA and its production is associated with the presence of estrogen and progesterone receptors. We have now developed a new tissue culture system to study PSA production in breast cancer and its association with prognostic factors such as progesterone receptor and c-erbB-2. For this purpose we investigated the ability of PSA production in five different cell lines, including two breast cancer cell lines, SK-Br-3 and MDA-MB-453. The PSA in tissue culture supernatant and cytoplasm of the Sk-Br-3 cell line was detected by western blotting and immunoperoxidase, respectively. Furthermore, we found lower expression of c-erbB-2 in Sk-Br-3 than non-PSA producer breast cancer cell line, MDA-MB- 453. Progesterone receptor was expressed by both PSA-positive and -negative cell lines and only the intensity of staining and the number of positive cells in SkBr- 3 population was higher than MDA-MB-453. According to our findings PSA can be considered as a good prognostic factor in breast cancer and we suggest that these two cell lines are a good in vitro model to study the relationship of different breast cancer prognostic factors and their regulations. Keywords: PSA, c-erbB-2, Progesterone receptor, Breast cancer, SK-Br-3. PSA, c-erbB-2, Progesterone receptor, Breast cancer, SK-Br-3. 41 46 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-230&slc_lang=en&sid=1 E KAMALI SARVESTANI immunol 2@sums.ac.ir 20031947532846004078 20031947532846004078 Yes From the Department of Immunology,Shiraz Medical School, Shiraz University of Medical Sciences, Shiraz, I.R. Iran. A GHADERI 20031947532846004079 20031947532846004079 No B GHARESI-FARD 20031947532846004080 20031947532846004080 No