Transforming properties of 8p11-12 amplified genes in human breast cancer

Amplification of the 8p11-12 region has been found in about 15% of human breast cancers and is associated with poor prognosis. Earlier, we used genomic analysis of copy number and gene expression to perform a detailed analysis of the 8p11-12 amplicon to identify candidate oncogenes in breast cancer. We identified 21 candidate genes and provided evidence that three genes, namely, LSM-1, TC-1, and BAG4, have transforming properties when overexpressed. In the present study, we systematically investigated the transforming properties of 13 newly identified 8p11-12 candidate oncogenes in vitro. WHSC1L1, DDHD2, and ERLIN2 were most potently transforming oncogenes based on the number of altered phenotypes expressed by the cells. WHSC1L1 contains a PWWP-domain that is a methyl-lysine recognition motif involved in histone code modification and epigenetic regulation of gene expression. Knockdown of WHSC1L1 in 8p11-12-amplified breast cancer cells resulted in profound loss of growth and survival of these cells. Further, we identified several WHSC1L1 target genes, one of which is iroquois homeobox 3 gene (IRX3), a member of the Iroquois homeobox transcription factor family.