As processing was associated with both ERα and PR in human breast carcinomas, we next studied the relation of fibulin-1 processing in vitro using three ER/PR-positive (MCF-7, T47D and BT-474) and three ER/PR-negative (MDA-MB-231, HS-578-T and SK-BR-3) human breast tumour-derived cell lines. The gene discussed is PGR; the disease is breast carcinoma.