Detection of prostate-specific antigen immunoreactivity in breast tumors

Abstract

Prostate-specific antigen (PSA) is a glycoprotein produced by the epithelial cells of the prostate. PSA is currently used in clinical practice to facilitate diagnosis and monitoring of prostate carcinoma. The prostate is an organ that possesses androgen, estrogen, and progesterone receptors, and in this respect is similar to the breast. We postulated that breast tumors might also have the ability to produce PSA. We performed these studies on a collection of 525 tumor specimens collected for routine biochemical determination of estrogen and progesterone receptors. Using a highly sensitive immunofluorometric procedure, we measured the p53 tumor suppressor gene product and PSA. Twenty nine percent of the breast tumor extracts contained detectable levels of PSA immunoreactivity (> 0.05 microgram/L). The immunoreactive PSA content was associated with estrogen and/or progesterone receptor-positive tumors (P < 0.002). No association was found between PSA immunoreactivity and levels of the p53 tumor suppressor gene product (P = 0.37). High performance liquid chromatography and Western blot analysis revealed that the PSA immunoreactivity in the tumor had a molecular weight of 30 kDa, similar to that of seminal PSA. Immunoreactive PSA-positive tumors were associated with younger women (P = 0.012) and earlier disease stage (P = 0.064). We postulate that PSA immunoreactivity may be an additional marker of steroid hormone receptor-ligand action.

Immunohistochemical localization of prostate-specific antigen in benign and malignant breast tissues

“…Our series of 27 breast tissues was selected from a large series of breast tumours previously used to study PSA expression by immunofluorometric analysis (Diamandis et al, 1994). The single criterion that we have used for selection was PSA content by immunofluorometry; 12 cases were negative for PSA, while the remainder were positive for PSA (PSA 2 2.5 ng mg-' total cytosolic protein).…”

“…Normal female breast also produces PSA , and during pregnancy PSA is secreted in human milk . PSA has been demonstrated using highly sensitive immunofluorometric procedures in approximately 30% of female breast tumours (Diamandis et al, 1994;Yu et al, 1994a, b), although specific histological types were not mentioned. As this technique does not allow for localization of the signal, heterogeneity of tumorous and non-tumorous breast tissue cannot be assessed.…”

“…Twenty-seven female breast tissues were chosen from a group that had been previously assayed for PSA immunofluorometrically (Diamandis et al, 1994). Representative slides were requested from the various hospitals which had supplied the initial tissues.…”

“…Breast tumour tissue obtained at surgery was pulverized and cytosolic fractions prepared as described previously (Diamandis et al, 1994). PSA in breast tumour cytosols was assayed using an immunofluorometric procedure (Yu and Diamandis, 1993).…”

“…PSA was originally described as being produced exclusively by prostatic tissue and is widely used as a tumour marker for patients with prostatic carcinoma (Armbruster, 1993). Although it is extremely uncommon to detect PSA in tumours other than those of prostatic origin, current studies have reported findings of PSA in 30% of female breast tumours using immunofluorometry (Diamandis et al, 1994;Yu et al, 1994a, b). Receptors for progestin, oestrogen and androgen have been exhibited in breast tumours, and studies have shown that the presence of PSA is associated with these receptors (Yu et al, 1994b).…”