Understanding the regulatory programs enabling cancer stem cells (CSCs) to self-renew and drive tumorigenicity could identify new treatments. Through comparative chromatin state and gene expression analyses in CSCs vs. non-CSCs, we identified FOXK2 as a highly expressed stemness-specific transcription factor (TF). Its genetic depletion diminished stemness features and reduced tumor initiation capacity. Our mechanistic studies highlight that FOXK2 directly regulates IRE1α (ERN1 gene) expression, a key sensor protein for the unfolded protein response (UPR). Chromatin immunoprecipitation (ChIP)-sequencing revealed that FOXK2 binds to an intronic regulatory element of ERN1. Blocking FOXK2 from binding to this enhancer by using a catalytically inactive CRISPR/Cas9 (dCas9) diminished IRE1α transcription. At the molecular level, FOXK2-driven upregulation of IRE1α led to alternative XBP1 splicing and activation of stemness pathways, while genetic or pharmacological blockade of this sensor of the UPR inhibited CSCs. We also identified that H3K79 methyltransferase DOT1L (disruptor of telomeric silencing-1-like) is a critical factor for self-renewal and tumor initiation capabilities of ovarian CSCs. We found that DOT1L is upregulated in ovarian CSCs and tumors from mice which received carboplatin treatment. DOT1L-knockdown by shRNA or inhibition by the small molecule inhibitor (DOT1Li) EPZ5676 reduced ALDH+ ovarian CSCs, impaired tumor initiation capability, and downregulated expression of stemness-associated genes. RNA-seq analysis revealed β-catenin as a target of DOT1L, and ChIP assay demonstrated enrichment of H3K79Me3 at the β-catenin promoter. Collectively, these data establish a new function for FOXK2 and DOT1L as key transcriptional regulators of CSCs, providing insight into potentially targetable new pathways.

Creator

• Zhang, Yaqi

DOI

• https://doi.org/10.21985/n2-79pp-4613

Subject

• Cellular biology

Language

• en

Alternate Identifier

• etdadmin_upload_925103
• http://dissertations.umi.com/northwestern:16199

Date created

• 2022-01-01

Resource type

• Dissertation

Rights statement

• In Copyright