Abstract 692: Uncoupling protein 2 (Ucp2) loss of function enhances mitochondrial ROS and sensitizes PDAC to radiation therapy
Authors: Caggiano Emily G. , Yu Meifang , Acevedo-Diaz Ariana , Taniguchi Cullen M. 
Published: March 2024

Abstract
Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with a dependence on highly active mitochondria to grow and metastasize. Normally mitochondria exist in long networks due to mitochondrial fusion but in PDAC mitochondria are fragmented due to excessive fission. We previously found that forcing PDAC cells to increase mitochondrial fusion suppressed tumor growth and metastasis, leading to improved survival in multiple preclinical models. The tumor suppressive mechanisms of mitochondrial fusion remain unclear, and thus we explored the role of redox homeostasis through uncoupling protein 2 (UCP2), a metabolic protein normally upregulated in PDAC that was downregulated upon forced mitochondrial fusion. We hypothesize that UCP2 mediates the oncogenic effects of mitochondrial fragmentation in PDAC.
Methods: We explored if Ucp2 is necessary and sufficient for inducing tumor suppression upon mitochondrial fusion. The effects of Ucp2 loss or overexpression were characterized by metabolic flux assays, proliferation, mitochondrial ROS (mROS), membrane potential, and morphology measurements. We also examined if Ucp2 recapitulates mitochondrial fusion-induced tumor suppression via pharmacological inhibition and genetic ablation and assessed the impact on mitochondrial health and cell growth. We utilized the LSL-KRASG12D; Trp53R172H/+; Ptf1⍺ Cre (KPC) cell line as our parental line for all genetic manipulations, with a nontargeting (sgGFP) KPC cell line as a control.
Results: Murine PDAC cells with enhanced mitochondrial fusion reduced Ucp2 transcript levels by 70% and was correlated with 3.5-fold increase in mROS, 50% reduction in OXPHOS via oxygen consumption rate assay, and a 4-fold increase in membrane potential compared to controls. Ucp2 re-expression did not rescue these phenotypes, suggesting that Ucp2 alone may not be sufficient for tumor suppression. However, inhibition of Ucp2 in PDAC cells reduced proliferation by 70%, while inducing a 3-fold increase in mROS levels, which was recapitulated with Ucp2 abrogation, thus Ucp2 may be necessary for tumor suppression. Enhanced mROS via Ucp2 inhibition significantly increased radiosensitivity (p-value &lt; 0.0001), suggesting that although it does not recapitulate the mitochondrial fusion phenotype, UCP2 may be a novel target for radiosensitization in PDAC.
Conclusions: Mitochondrial fusion may not suppress tumor growth by altering redox homeostasis via UCP2, but forcing mitochondria to fuse elucidated the impacts of UCP2 downregulation on cell metabolism. Thus, we uncovered that UCP2 may be a novel target for radiosensitization. Further insight into UCP2’s role in redox balance, and how it is disrupted with UCP2 modulation enables development of novel therapeutic combinations with UCP2 inhibition that complement and potentially synergize with existing therapeutic strategies such as radiation.
Citation Format: Emily G. Caggiano, Meifang Yu, Ariana Acevedo-Diaz, Cullen M. Taniguchi. Uncoupling protein 2 (Ucp2) loss of function enhances mitochondrial ROS and sensitizes PDAC to radiation therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 692.