Principal Investigator: Wael El-Rifai, MD, Ph.D.

This project investigates mechanisms by which APE1-redox function promotes the activation of SOX9 in esophageal adenocarcinoma (EAC) under reflux conditions. Chronic exposure to acidic bile salts induces inflammation and is associated with a dramatic increase in the burden of oxidative stress; believed to be the main driving forces for disruption of cellular signaling mechanisms and the development of EAC. It is unknown how tumorigenic esophageal cells escape the oxidative effects of acidic bile salts reflux and also become resistant to currently used chemotherapeutic agents. Alterations in the redox status of reactive cysteine residues located within the DNA-binding domain of redox-sensitive transcription factors (TFs) can suppress TFs’ DNA binding affinity and transcription activity. Therefore, the cellular redox capacity is paramount in promoting activity of oncogenic transcription factors, protecting tumorigenic cells and promoting their survival and expansion. This project builds upon collective interaction among the three projects generating several novel preliminary findings. We have shown that AP endonuclease 1 (APE1) redox activity was required for the activation of tumorigenic transcription factors such as SOX9 in response to exposure to reflux and chemotherapeutics. As part of scientific integration in this P01, working with Projects 2 and 3, we also found that high levels of reactive isolevuglandins (isoLGs) protein adducts promote the stability of SOX9. As a result of these molecular events, EACs develop intrinsic and acquired resistance to standard chemotherapeutics. Based on our preliminary results, we aim to investigate the role of APE1-redox function in promoting SOX9 activation in EACs. In Aim 1, we will investigate the role of APE1 and isoLG adducts in regulating SOX9 stability and activity. The functional outcome of the APE1-SOX9 network is investigated in Aim 2. The clinical significance and therapeutic potential of targeting APE1 redox activity will be determined in Aim 3. Understanding biology-relevant molecular functions, the focus of this P01 and this project is a key step for developing evidence-based therapeutic approaches that are founded on the biology and molecular underpinning of EAC. Upon completion of our work, we expect to uncover a new paradigm for understanding the biology of EAC to facilitate the development of novel medical treatments for this deadly cancer. 

Principal Investigator: Alexander Zaika, Ph.D.

This project investigates innovative hypotheses explaining how reflux induces carcinogenic alterations in the esophagus through protein adduction with reactive isolevuglandins and aberrant activation of the JAK/STAT signaling pathway. This hypothesis is supported by strong preliminary data generated by animal studies and analyses of human tissue specimens collected from patients with BE and GERD. In aim 1, we will define novel, previously uncharacterized mechanisms regulating the JAK/STAT signaling by protein adduction in conditions of esophageal reflux injury. In aim 2, we will investigate the regulation of protein adducts in the esophageal niche using animal models of EAC and human clinical specimens. The translational experiments include the use of 2-HOBA to inhibit the formation of oncogenic protein adducts and progression to EAC in animal models of Barrett’s tumorigenesis. In Aim 3, we will test various options to inhibit protein adduction in a pro-tumorigenic environment created by chronic gastroesophageal reflux and investigate how it affects esophageal carcinogenesis. Our project is an integral part of the P01 program focused on the mechanistic studies of EAC tumorigenesis while exploring novel cancer chemopreventive and treatment options. This cooperative study will also expand and deepen our understanding of esophageal carcinogenesis by exploring the intersections of the isolevuglandins with APE1-SOX9 and SOX4 signaling networks, examined in Projects 2 and 3.  Our collective studies in this project and the P01 program are expected to lay the groundwork for novel therapeutic applications. 

Principal Investigator: Jianwen Que, M.D., Ph.D. 

This project investigates the role of SOX4 in EAC development, specifically its role in promoting EGFR and ELF3 survival signals. Directly address novel molecular mechanisms that control the transition from stem cells to adenocarcinoma-initiating cells and whose inhibition has the potential to block EAC development. Studies have shown that the malignant transformation of stem/progenitor cells is a critical mechanism that occurs during esophageal cancer initiation. In the case of EAC, we have identified that the novel transitional basal cells (TBCs) located at the esophageal-gastric junction (EGJ) are able to generate Barrett’s esophagus upon Cdx2 overexpression. The preliminary data show that EAC develops at the EGJ following prolonged Cdx2 overexpression and bile acid reflux. The genetic regulatory program that drives stem cell transformation and cancer maintenance. However, remains elusive. We found that the SOX4 transcription factor is highly expressed in mouse EAC models and human EAC biopsies. Decreased levels of SOX4 protein are associated with reduced cancer growth. Using a combination of RNA-Seq, ChIP-Seq, and targeted RNAi screening, we identified EGFR and ELF3 as potential downstream targets mediating SOX4 function in tumor development. The underlying hypothesis: SOX4 is critical for EAC initiation and maintenance and suppressing SOX4-centered signaling can be utilized for therapeutic gains in EAC treatment.

This hypothesis will be investigated with three aims:(1) To determine the role of SOX4 in EAC development; (2) to test the hypothesis that SOX4 transcriptionally regulates EGFR and ELF3 in EAC; and (3) to determine the therapeutic role of SOX4 inhibition in EAC treatment. As a proof of concept, the translation studies in Project 3 include testing FDA-approved drugs that inhibit SOX4 to develop a novel strategy to treat EACs. We will use multiple mouse models (e.g., SOX4 gain- and loss-of-function) combined with organoid and patient-derived xenograft models to address these aims and test two candidate drugs identified through an unbiased screen. Our studies will provide novel insights into the cellular and molecular mechanisms underlying the EAC’s initiation and progression, facilitating the development of novel treatments for deadly EAC.