Cancer Therapeutic Resistance: Implication of AcAPE1 Mediated DNA Repair and T-Cell Based Immunotherapy

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Project Summary / Abstract This research proposal is intended to provide predoctoral and postdoctoral training to develop the necessary skills for a career as an independent investigator in cancer biology. The long-term research focus is development of effective cancer therapies through 1) identification of genetic, epigenetic and transcriptomic changes in human cancers before and after therapy, 2) studying the effects of transcriptional changes in tumor cells on therapeutic efficacy, and 3) developing novel combinatorial therapies against human cancers using chemo-immuno- CRISPR/Cas9. The objective of my dissertation research (F99 phase) is to define the role of acetylation of APE1 (AcAPE1) in oncogenesis and chemoresistance, with the goal of establishing AcAPE1 as a novel therapeutic target. APE1 is a ubiquitous multifunctional protein, a key enzyme in Base Excision Repair (BER) pathway, involved in the maintenance of genomic integrity and in the regulation of gene expression. We discovered that multiple Lysine residues (Lys 6, 7, 27, 31, &32) in N-terminal domain of APE1 can be modified by acetylation (AcAPE1), which modulates the transcriptional regulatory function of APE1 and AcAPE1 is essential in cell survival. It remains unclear how N-terminal acetylation of APE1 regulates cell proliferation and survival. Knowledge of functional importance of acetylation of APE1 is critical. We have recently made several discoveries relevant to this concept. First, APE1 is acetylated after binding to the AP sites in the chromatin and the acetylation process occurs only at transcriptionally active gene regions. Importantly, subsequent studies revealed that transcription-coupled acetylation of APE1 plays a key role in the preferential repair of damaged DNA bases or AP sites in transcribed gene regions, via enhancing DNA repair activity of APE1. Moreover, this damage –repair facilitates transcription. Based on these and additional data we hypothesize that AcAPE1 mediated- repair of transcriptionally active regions promotes oncogenesis and facilitates chemo-resistance in tumor cells. As a corollary, we predict that targeting acetylation sites of APE1 in tumor cells will promote chemosensitivity. Our research will utilize different chemotherapeutic drug resistant cancer cell lines to define an oncogenic damage-repair role of AcAPE1 and the effect of AcAPE1 activity on the transcriptional profile. We will also determine the therapeutic activity of acetylation defective APE1 using in vitro and in vivo models. To expand upon the future research direction and to build the foundation for independence, I will pursue postdoctoral training in cancer immunotherapy. The goal of the proposed K00 postdoctoral training is to gain expertise on current T- cell based immunotherapeutic strategies, the mechanisms that promote resistance to such immunotherapy, the molecular biology behind killer T-cell exhaustion, and development of novel combinatorial therapeutics to treat cancer. Ultimately, the proposed F99/K00 training will provide a strong intellectual foundation for R01 funding that will establish my independence and will provide professional training in the skills required to be an effective PI and mentor.