TENASCIN IN BREAST-CANCER DEVELOPMENT - IS EPITHELIAL TENASCIN A MARKER FOR POOR-PROGNOSIS

(1) In mouse mammary gland development, immunoreactive tenascin (TN) i s expressed in the dense mesenchyme surrounding the epithelial compone nt of 14-day embryos, endbuds at puberty, and tumors. (2) Cells that p roduce TN are myofibroblastic and are characterized by nuclear invagin ations, rough endoplasmic reticulum, and pinocytotic vesicles. These c ells are not normally present in the stroma of mammary glands but pres ent in cancer stroma, originating probably from fibroblasts differenti ated under the influence of TGF-beta 1 stimulation. (3) Breast cancer cells are capable of synthesing TN under certain conditions. TN-non-pr oducing MCF7 cells can produce TN when co-cultured with embryonic fibr oblasts or with their conditioned medium. (4) Nine primary human breas t cancers were examined for TN expression by in situ hybridization. TN mRNA was expressed in all nine cases in the stroma and in four cases in carcinoma cells as well, (5) Immunohistochemistry for TN was perfor med in human breast cancers, and it was found that the five-year survi val after surgery was markedly lower in the group whose cancer cells w ere negative for TN. TN expression in cancer cells appears to indicate poor prognosis.