Microcell-Mediated Chromosome Transfer Identifies EPB41L3 as a Functional Suppressor of Epithelial Ovarian Cancers

Abstract

We used a functional complementation approach to identify tumor-suppressor genes and putative therapeutic targets for ovarian cancer. Microcell-mediated transfer of chromosome 18 in the ovarian cancer cell line TOV21 G induced in vitro and in vivo neoplastic suppression. Gene expression microarray profiling in TOV21 +19 hybrids identified 14 candidate genes on chromosome 18 that were significantly overexpressed and therefore associated with neoplastic suppression. Further analysis of messenger RNA and protein expression for these genes in additional ovarian cancer cell lines indicated that EPB41L3 (erythrocyte membrane protein band 4.1-like 3, alternative names DAL-1 and 4.1 B) was a candidate ovarian cancer-suppressor gene. Immunoblot analysis showed that EPB41L3 was activated in TOV21 +18 hybrids, expressed in normal ovarian epithelial cell lines, but was absent in 15 (78%) of 19 ovarian cancer cell lines. Using immunohistochemistry, 66% of 794 invasive ovarian tumors showed no EPB41L3 expression compared with only 24% of benign ovarian tumors and 0% of normal ovarian epithelial tissues. EPB41L3 was extersively methylated it ovarian cancer cell Hires and primary ovarian tumors compared with normal tissues (P = 00004), suggesting this may be the mechanism of gene inactivation it ovarian cancers. Constitutive reexpressior of EPB41L3 it a three-dimensional multicellular spheroid model of ovarian cancer caused significant growth suppressior and induced apoptosis. Transmission and scanning electron microscopy demonstrated many similarities between EPB41L3-expressing cells and chromosome 18 donor-recipient hybrids, suggesting that EPB41L3 is the gene responsible for reoplastic suppression after chromosome 18 transfer. Finally, ar irducible model of EPB41L3 expression it three-dimersioral spheroids confirmed that reexpression of EPB41L3 induces extensive apoptotic cell death it ovarian cancers.