Effect of HIPK3 depletion in tamoxifen-resistant EGFR-overexpressing MCF7 breast cancer cells

Overexpression and activation of EGFR in breast cancer can cause resistance to antiestrogen treatmen. Using high-throughput screening, we have identified HIPK3 as a mediator of tamoxifen resistance in MCF7 breast cancer cells. HIPK3 depletion re-sensitized cells to 4-hydroxytamoxifen under EGF-stimulated conditions. In this study, we investigated the transcriptomic responses to HIPK3 depletion, together with EGF stimulation and treatment with estradiol and 4-hydroxytamoxifen. RNA-sequencing demonstrated that depletion of HIPK3 caused increased expression of genes involved in mitotic signaling, oxidative damage, endoplasmatic reticulum stress and apoptosis in EGF, estradiol and tamoxifen treated MCF7 cells. Overall design: We used MCF7 cells overexpressing EGFR to study (EGFR-mediated) tamoxifen resistance. The role of HIPK3 was investigated by performing siRNA knockdown of HIPK3 followed by gene expression profiling using RNAseq in EGFR-overexpressing MCF7 cells. Moreover, we studied the responses to EGF and EGF, estradiol and 4-hydroxytamoxifen treatment in these cells, and how this is affected by HIPK3 knockdown, to understand potential mechanisms of drug resistance and sensitization.