Epigenetic regulators can modulate the effects of cancer therapeutics. To further these observations, we discovered that the bromodomain PHD finger transcription factor subunit (BPTF) of the nucleosome remodeling factor (NURF) promotes resistance to doxorubicin, etoposide, and paclitaxel in the 4T1 breast tumor cell line. BPTF functions in promoting resistance to doxorubicin and etoposide, but not paclitaxel, and may be selective to cancer cells, as a similar effect was not observed in embryonic stem cells. Sensitization to doxorubicin and etoposide with BPTF knockdown (KD) was associated with increased DNA damage, topoisomerase II (TOP2) crosslinking and autophagy; however, there was only a modest increase in apoptosis and no increase in senescence. Sensitization to doxorubicin was confirmed in vivo with the syngeneic 4T1 breast tumor model using both genetic and pharmacologic inhibition of BPTF. The effects of BPTF inhibition in vivo are autophagy dependent, based on genetic autophagy inhibition. Finally, treatment of 4T1, 66cl4, 4T07, MDA-MB-231, but not ER-positive 67NR and MCF7 breast cancer cells with the selective BPTF bromodomain inhibitor, AU1, recapitulates genetic BPTF inhibition, including in vitro sensitization to doxorubicin, increased TOP2-DNA crosslinks and DNA damage. Taken together, these studies demonstrate that BPTF provides resistance to the antitumor activity of TOP2 poisons, preventing the resolution of TOP2 crosslinking and associated autophagy. These studies suggest that BPTF can be targeted with small-molecule inhibitors to enhance the effectiveness of TOP2-targeted cancer chemotherapeutic drugs. Implications: These studies suggest NURF can be inhibited pharmacologically as a viable strategy to improve chemotherapy effectiveness.

No abstract

No abstract

Dysregulation of the epigenome is implicated in initiation and progression of variety of cancers and their acquired resistance to chemotherapy. As such targeting epigenetic regulators has the potential to modulate cancer cell biology and their sensitivity to chemotherapy and/or radiation. Our studies demonstrates that silencing of the epigenetic regulator Nucleosome Remodeling Factor (NURF) sensitizes breast tumor cells to chemotherapy and enhances the anti-tumor immune response. A screen of a variety of chemotherapeutic agents shows that NURF KD cells are selectively sensitized to Topo II inhibitors, which includes doxorubicin. NURF KD increases DNA damage (gamma H2AX staining) and autophagy (acridine orange staining) in breast tumor cells exposed to doxorubicin (Dox) and enhances growth inhibition as well as suppressing the ability of the cells to recover proliferative capacity. Increased autophagy as well as breast tumor sensitization to doxorubicin were observed using a small molecule inhibitor of NURF, suggesting that NURF can also be targeted pharmacologically. Our studies suggest that enhanced autophagy may be a primary contributor to chemo sensitivity in NURF KD cells. Studies are currently underway to confirm the role of autophagy in chemosensitization in- vitro and enhanced immune response in-vivo using autophagy deficient cells (through ATG silencing). Doxorubicin produces profound DNA damage and promotes immunogenic cell death enhanced by NURF KD. Increased cell autonomous antitumor effects by doxorubicin in concert with increased cell non-autonomous antigenicity could help to achieve tumor regression, reduce metastasis, and possibly promote long term remission in breast cancer. Citation Format: Liliya Tyutyunyk, Joseph Landry, David Gewirtz, Nga Dao. Role of epigenetic remodeling in sensitizing triple-negative breast cancer cells to treatment through enhanced chemotherapy-induced autophagy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1330.

Dysregulation of the epigenome is implicated in initiation and progression of variety of cancers and their acquired resistance to chemotherapy. As such, targeting epigenetic regulators has the potential to modulate tumor cell biology and reestablish tumor cell sensitivity to chemotherapy and/or radiation. Our studies demonstrate that silencing of the epigenetic regulator Nucleosome Remodeling Factor (NURF) sensitizes breast tumor cells to chemotherapy and enhances the anti-tumor immune response. Compared to controls, NURF KD 4T1 breast tumor cells exposed to doxorubicin (Dox) show increased DNA damage (gamma H2AX staining) and autophagy (acridine orange staining) in vitro and enhanced growth inhibition both in vitro and in vivo. NURF KD also sensitizes 4T1 cells to doxorubicin stimulated Natural Killer (NK) cell antitumor activity ex vivo, which is associated with a cytokine/chemokine secreted by doxorubicin exposed NURF KD cells; potential candidates are CCL5, TNFa and CCL2. The importance of NK cells for the enhanced growth control of doxorubicin treated NURF KD cells was confirmed using a mAb depletion approach. Autophagy may be instrumental in NK cell activation and elimination of tumor cell targets by mediating cytokine secretion. Sensitization of NURF KD 4T1 cells to doxorubicin, both increased autophagy and enhanced NK cell activity, were also observed using a small molecule inhibitor of NURF, suggesting that NURF can also be targeted pharmacologically. Our studies suggest that enhanced doxorubicin induced DNA damage and autophagy (cell autonomous effects) and NK cell cytotoxic activity (cell non-autonomous affects) may be primary contributors to immune sensitization in NURF KD cells. Increased cell autonomous antitumor effects by doxorubicin in concert with increased cell non-autonomous immunogenicity could help to achieve tumor regression, reduce metastasis, and possibly promote long term remission in breast cancer. Citation Format: Liliya Tyutyunyk, David A. Gewirtz, Joseph Landry, Nga Dao. Suppression of epigenetic regulator NURF leads to autophagy mediated chemo-and immune sensitization of triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4272.