Enhancing Tumor Cell Immunogenicity using Improved Molecules Targeting Chromatin Remodeling

PROJECT SUMMARY Few therapies have yet to achieve durable remission of advanced stage triple negative breast cancer (TNBC). One promising approach to improve clinical outcomes is to combine multiple chemotherapies to stimulate an antitumor response. An underlying premise for this approach is that select chemotherapies enhance

TNBC immunogenicity, thereby stimulating the anti-tumor immune response improving tumor growth control. With this strategy in mind, we have discovered that inhibiting the epigenetic regulator BPTF, of the nucleosome remodeler NURF, either genetically or pharmacologically, is a novel approach for improving TNBC

immunogenicity. In this proposal we now show using two different TNBC tumor models that when BPTF depletion is combined with the DNA methyl transferase inhibitor (DNMTi) Guadecitabine (Guad) we further stimulate tumor cell immunogenicity and dramatically improve tumor growth control in immune competent, but not immune

compromised mice. Genome wide analysis shows that the combination therapy enhances immune stimulatory pathways, with an enrichment for immune stimulatory cytokines. Thus, using a novel combination approach, we hypothesize that BPTF depletion/inhibition will synergize with immune stimulating therapies targeting epigenetic

factors (Guadecitabine) for TNBC treatment improving therapeutic outcomes. In Aim1, will identify the immune reactive effector cells required for the antitumor effects of Guad + BPTF depletion using the mouse E0771 TNBC tumor model. Additional flow cytometry and ex vivo immune cell assays will characterize and further define the immune cells required for these antitumor activities. The BPTF inhibitor

BZ1 + Guad will be used in parallel tumor studies using the E0771 model to determine if it has in vivo activity, and in molecular studies (RNA-Seq and ATAC-Seq) from FACS sorted E0771 tumor cells to determine if it has similar effects to that of BPTF KO. Humanized mouse models and TNBC PDX samples will validate the

translatability of these findings. In Aim2, we will optimize the drug-like properties of our second generation lead BPTF inhibitor. Validating the therapeutic potential for BPTF inhibition has been significantly limited due to a lack of potent inhibitors for BPTF. Our first generation BPTF bromodomain inhibitor, AU1, while effective for initial

validation of BPTF inhibition in cells, and in vivo, its poor physiochemical properties and modest activity in vivo have limited further validation of BPTF as a drug target. Using structure-based design we have now developed a second and highly potent inhibitor series. Here, we focus on optimizing its drug-like properties, using both

established biophysical and cell-based assays to translate our findings to our in vivo model system in Aim 1. The completion of these Aims will deepen our understanding of cancer cell epigenetics, and cancer cell immunogenicity by characterizing the effects of inhibiting the chromatin factor NURF in combination with DNMTi.

Our approach is further designed to enhance antitumor immunity to TNBC by improving therapy induced tumor immunogenicity through a combination epigenetic therapy.