DIFFERENTIAL EXPRESSION OF HUMAN FERRITIN H-CHAIN GENE IN IMMORTAL HUMAN BREAST EPITHELIAL MCF-10F CELLS

Subtractive hybridization was used to isolate genes expressed uniquely in the immortalized human breast epithelial cell (HBEC) line MCF-10F and not in the mortal HBEC line 5-130, from which MCF-10F cells were d erived. We identified a 233-bp cDNA that was expressed in MCF-10F cell s and not in their mortal counterpart 5-130 cells. Sequence comparison with the CenBank database revealed that the cDNA was identical to the gene encoding human ferritin heavy H chain. Northern blot analysis us ing the isolated cDNA as a probe showed a differentially expressed 1.1 -kb transcript of ferritin H in total RNA from the immortal MCF-10F ce lls, MCF-10F cells treated with the chemical carcinogens 7,12-dimethyl benz[a]anthracene and benzo[a]pyrene, and the breast cancer cell lines MCF-7, HBL-100, T-47D, and BT-20. No ferritin H transcript was detect ed in the mortal line 5-130 or in other primary HBEC cultures. Increas ed levels of mRNA transcript signals were also detected in total RNA f rom breast cancer tissue samples. Tissue with ductal hyperplasia had h igher expression levels than normal adjacent mammary tissue. In situ h ybridization showed high levels of ferritin H transcript in mammary ti ssue areas with ductal hyperplasia, carcinoma in situ, and infiltratin g ductal carcinoma. This is the first report of the differential expre ssion and upregulation of human ferritin H chain gene in immortal HBEC s. It may be an important factor in the process of immortalization, po ssibly an early stage of malignant transformation of HBECs, providing cells with iron necessary for growth and clonal expansion. Also, ferri tin iron, once released, may increase the level of reactive iron, lead ing to an increase in oxygen free-radical generation, oxidative DNA da mage, and mutation. (C) 1997 Wiley-Liss, Inc.