Maspin, a Serpin with Tumor-Suppressing Activity in Human Mammary Epithelial Cells

TLDR

A serpin‑family protein encoded by a candidate tumor suppressor gene has been implicated in human breast cancer. Maspin is expressed in normal mammary epithelium but is largely absent in most mammary carcinoma cell lines. Introducing maspin into MDA‑M‑B‑435 cells did not affect in‑vitro growth yet markedly reduced tumor formation, metastasis, and invasion, and its loss is most frequent in advanced breast cancers, confirming maspin’s tumor‑suppressive role.

Abstract

A gene encoding a protein related to the serpin family of protease inhibitors was identified as a candidate tumor suppressor gene that may play a role in human breast cancer. The gene product, called maspin, is expressed in normal mammary epithelial cells but not in most mammary carcinoma cell lines. Transfection of MDA-MB-435 mammary carcinoma cells with the maspin gene did not alter the cells' growth properties in vitro, but reduced the cells' ability to induce tumors and metastasize in nude mice and to invade through a basement membrane matrix in vitro. Analysis of human breast cancer specimens revealed that loss of maspin expression occurred most frequently in advanced cancers. These results support the hypothesis that maspin functions as a tumor suppressor.