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Abstract
BPTF Enhances Chemotherapy Induced Cytotoxicity
Valentina Posada, Depts. of Biology, Chemistry, & Religious Studies, with Dr. Joseph Landry, Dept. of Human Molecular Genetics
New chemotherapies and immunotherapy treatments have greatly improved the outcomes of many cancers. However, for Triple Negative Breast Cancer (TNBC), existing therapies are not very effective long term as the disease becomes resistant and has low immunogenicity. Here we show the early development of a new way to treat the disease by combining existing chemotherapies with depletion of the Nucleosome Remodeling Factor (NURF). NURF is an ATP-dependent chromatin remodeling complex that is over-expressed in cancers and has shown to inhibit the anti-tumor immune response. The largest and essential subunit of the complex, BPTF is required for function. BPTF shRNA-mediated knockdown (KD) was done as a way to deplete cells of NURF. Our first aim was to determine if BPTF-KD cells showed enhanced sensitization to chemotherapies most prominently Doxorubicin. The results from completing this aim showed sensitization to several chemotherapies which correlated with enhanced therapy-induced autophagy. Our second aim was then to investigate the role of autophagy in the sensitization of BPTF-KD cells to chemotherapies. Autophagy is a process by which cells undergoing stress consume their cellular components. This process is mediated in part by the ATG5 protein. ATG5 KD was done through lentivirus transfection, and in turn, functional blockade of autophagy was achieved as confirmed by Western blotting. Results showed that BPTF-KD cells did not have enhanced sensitivity to Doxorubicin through the blockade of autophagy, which suggested a non-protective role in autophagy, while the BPTF-WT cells that had autophagy blocked did show an enhanced sensitization, suggesting a cytoprotective role. Aims were then tested in vivo to determine the role of autophagy in BPTF-KD cells in vivo. BPTF-KD and ATG5-KD 4T1 cells were transplanted into mice and tumor volume over time was measured. Syngeneic mouse models showed that the BPTF-KD tumors had significantly smaller tumor volumes than the control when treated with Doxorubicin, and therefore showed sensitization to Doxorubicin. Results for the ATG5 KD mice show tumors growing better in the WT while growing worse in the KD1/ KD2 mice suggesting that autophagy is required for sensitization of BPTF-KD tumors to Doxorubicin in vivo. The third aim of the project was to determine the possible immune-modulatory consequences of treating BPTF KD cells with chemotherapies. Natural Killer (NK) cells were depleted in mice to see if there would be a change in the sensitization to therapies. Results showed that once we depleted NK cells in mice with a mAb-depletion strategy, the sensitization to Doxorubicin was lost. Furthermore, a metabolomics screening was conducted and reductions in prostaglandin E2 (PGE2) were discovered in the therapy treated BPTF-KD cells. PGE2 is a well know immune suppressive metabolite produced by tumor cells to suppress the anti-tumor immune response. Further results showed PGE2 reductions when autophagy was blocked by ATG5 KD in the BPTF-KD cells. This result could explain the improvements in tumor growth within the mice since PGE2 is a known NK cell inhibitor. Together, these results suggest that NURF could be a therapeutic target for enhancing clinical outcomes in Triple Negative Breast Cancer Patients.
Publication Date
2020
Faculty Advisor/Mentor
Joseph Landry, Ph.D.
Sponsorship
Virginia Commonwealth University. Undergraduate Research Opportunities Program
Is Part Of
VCU Undergraduate Research Posters
Rights
© The Author(s)