Kpenu : Exploring the DNA repair mechanism of the APE1-Ref-1 protein
Exploring the DNA repair mechanism of the APE1/Ref-1 protein
Indiana University School of Medicine
Mark R. Kelley
Pancreatic Ductal Adenocarcinoma (PDAC) is inherently resistant to therapy and can proliferate under conditions of hypoxia and nutrient deprivation. Innovative approaches against new targets are needed. Redox factor-1 (APE1/Ref-1) is a regulator of multiple transcriptional factors involved in cancer cell signaling through its redox signaling activity. Ref-1 redox status is itself regulated by other redox proteins such as peroxiredoxin (PRDX) and thioredoxin (TRX). Studies have demonstrated an interaction of peroxiredoxin-1 (PRDX1) and Ref-1. PRDX1 is a member of a family of peroxidases comprising six isoforms that differ in their H2O2 scavenging, organelle/conditional expressions, and chaperone activity; yet their relationship with Ref-1 is largely unknown.
Using siRNA knock-down of PRDX1 (PRDX1KD) or TRX (TRXKD) in combination with our second-generation Ref-1 inhibitor APX2014, we explored the PRDX-Ref-1-TRX axis in a human patient PDAC cell line, Pa03c. We then engineered CRISPR/Cas9 PRDX1 knock-out cells (PRDX1KO) and tested APX2014.
We found that both PRDX1KD and TRXKD conditions resulted in significant sensitivity to Ref-1 inhibition. PRDX1KO cells were even more sensitive to Ref-1 inhibition compared to the PRDX1KD cells. Ref-1’s second major function as a DNA repair protein apurinic/apyrimidinic endonuclease was not impacted by PRDX1KO. We measured growth and cell-colony formation and confirmed statistical distinctions. Initial studies with PRDX2 knockdown (PRDX2KD) had no increased effect in combination with Ref-1 inhibition.
Our hypothesis is that the activity of Ref-1 and interplaying redox proteins such as PRDX1 in PDAC tumor microenvironment (TME) correlates with resistance to treatment and thus could be a biomarker of response to the currently available standard of care regimens.
Translational/Human Health Impact:
The eventual goal is to select the subset of patients who could benefit most from APX compounds, which are currently in clinical development and could be an important addition to the current arsenal of treatments either in the upfront setting or upon failure.