DAB2IP Loss in Luminal A Breast Cancer Leads to NF-kB- Associated Aggressive Oncogenic Phenotypes

Despite proven therapy options for estrogen receptor (ER)-positive tumors, a significant number of patients with these cancers exhibit relapse with associated metastasis. Studies have shown that the loss of expression of RasGAPs leads to aggressive phenotypes and poor outcomes in several cancers including breast cancer. In our study, mining TCGA gene expression profiles of ER-positive breast tumors, we found that low expression of the RasGAP, DAB2IP is associated with a significant decrease in relapse-free survival in patients with Luminal A breast tumors. Immunostaining found that DAB2IP loss occurs in grade 2 tumors and higher. Consistent with this, genes upregulated in low DAB2IP Luminal A tumors are shared with more aggressive tumor subtypes, and are associated with proliferation, metastasis, and enhanced ER-signaling. In addition, cell-based studies reveal that low DAB2IP expression in ER-positive breast cancer cells is associated with increased proliferation, enhanced stemness phenotypes, and activation of IKK, the upstream regulator of the NF-B signaling pathway. Further, integrating cell-based ChIP-seq with motif analysis and TCGA RNA-seq data, we identify a candidate set of NF-B target genes that are upregulated with loss of DAB2IP and are proposed to regulate several oncogenic phenotypes, including altered RNA processing. This study provides new insight into mechanisms associated with aggressiveness and recurrence within a subset of Luminal A breast cancers that are otherwise typically less aggressive.