Genome-wide maps of XBP1 binding sites in different breast cancer cell lines [ChIP-Seq]

We report the application of ChIP-seq, which combines chromatin immunoprecipitation (ChIP) with massively parallel DNA sequencing, to map genome-wide XBP1 binding sites in different breast cancer cell lines. We showed that HIF1α motif was enriched in XBP1 binding sites in triple negative breast cancer (TNBC) cell lines, but not enriched in ER positive breast cancer cell line. We also demonstrated that different breast cancer cell lines of the same sub-type had similar XBP1 binding sites, whereas different breast cancer sub-types had majorly different XBP1 binding sites. Finally, a model was applied to integrate XBP1 ChIP-seq data with expression data to predict XBP1's direct targets in TNBC cell line; the predicted direct targets were shown to be predictive of patient survival, and the prediction power was specific to TNBC patients. The above evidence indicates that XBP1 performs important functions in TNBC by interacting with HIF1α, and such regulation mechanism is specific to TNBC, which is later proved by follow-up experiments.This study represents the first detailed anaysis of XBP1 binding sites in different breast cancer cell lines.