Expression of LINE‐1 retrotransposons in human breast cancer

Abstract

Background. Several diseases have been linked to the insertion of human LINE‐1 retrotransposons (L1Hs) into structural genes. Recently, the element has been shown to be expressed in a variety of adult and pediatric germ cell cancers, leading to speculation that L1Hs‐induced insertion mutations may play a role in the etiology of some neoplasias. Methods. An L1Hs‐encoded protein (p40) was assayed in breast cancer cell lines by Western blotting and in solid tumors by immunohistochemical staining and Western blotting. Results. L1Hs retrotransposons are expressed in a significant number of human breast cancers: expression was detected in 7 of 8 malignant cell lines and in 9 of 12 primary infiltrating ductal carcinomas. No expression was detected in two nonmalignant breast epithelial cell lines, five malignant B‐ or T‐cell lines, tissue from a normal breast, a primary breast sarcoma, or a primary medullary carcinoma of the breast. Conclusions. These results raise the possibility that L1Hs expression may contribute to the origin or progression of some breast cancers. Copyright © 1994 American Cancer Society