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

Despite proven therapy options for estrogen receptor (ER)-positive breast tumors, a substantial number of ER+ cancer patients exhibit relapse with associated metastasis. Loss of expression of RasGAPs leads to poor outcomes in several cancers, including breast cancer. Mining the TCGA breast cancer RNA-sequencing dataset revealed that low expression of the RasGAP DAB2IP was associated with a significant decrease in relapse-free survival in Luminal A breast cancer patients. Immunostaining demonstrated that DAB2IP loss occurred in grade 2 tumors and higher. Consistent with this, genes upregulated in DAB2IP-low Luminal A tumors were shared with more aggressive tumor subtypes and were associated with proliferation, metastasis, and altered ER signaling. Low DAB2IP expression in ER+ breast cancer cells was associated with increased proliferation, enhanced stemness phenotypes, and activation of IKK, the upstream regulator of the transcription factor NF-kB. Integrating cell-based ChIP-sequencing with motif analysis and TCGA RNA-seq data, we identified a set of candidate NF-kB target genes upregulated with loss of DAB2IP linked with several oncogenic phenotypes, including altered RNA processing. This study provides insight into mechanisms associated with aggressiveness and recurrence within a subset of the typically less aggressive Luminal A breast cancer intrinsic subtype.