Abstract A67: Jarid1b protects from metformin-induced chemosensitization to cisplatin through p53 downregulation in NSCLC
Authors: Tortelli Tharcisio Citrangulo , Tamura Rodrigo Esaki , Tomitao Michele Tatiana Pereira , Bustos Silvina Odete , Saito Renata de Freitas , Leandrini Sarah Milani de Moraes , Jacomassi Mayara D'Aurea , Ribeiro Ulysses , Strauss Bryan Erik , Chammas Roger 
Published: May 2019

Abstract
Background: Instead of nontransformed cells, tumor cells use the glycolytic pathway as their main energetic source, even when oxygen is fully available. Recently, a new tumor subpopulation that is characterized by the overexpression of the histone demethylase Jarid1b has been found in melanomas and other tumors. Jarid1b-high cells use the mitochondria as the main energy source and are more resistant to chemotherapy. Also, Jarid1b-high cells have downregulation of p53. Changes in the metabolic profile of chemoresistant tumor cells could restore chemosensitization to drugs that induce high levels of oxidative stress, such as cisplatin. A possible strategy to modify the metabolism of tumor cells that uses the mitochondria as the main energy source is to use metformin. Many reports shows that patients who use metformin as treatment for type II diabetes have less incidence of cancer in general. However, many other reports show that metformin is unable to improve cancer treatment when used as an adjuvant therapy. Results from our group show that the use of metformin as a chemosensitizing agent depends on p53 status. When p53 is present, metformin can sensitize cells to cisplatin. Cells that lose p53 expression, like Jarid1b-high cells, or p53 KO cells are resistant to the combination of metformin and cisplatin.
Aim: To evaluate when metformin can be used as a chemosensitizing agent to cisplatin.
Methods: The human NSCLC A549 (p53 WT) and H1299 (p53 KO) and the colon carcinoma cells HCT 116 (p53 WT) and HCT 116 (CRISPR to p53) were used in this study. A549 cells were pretreated with low dose of cisplatin (PT-Pop) to induce Jarid1b overexpression and p53 downregulation.
Results: Metformin sensitized A549 cells to cisplatin, leading to high levels of cell death. On the PT-Pop, metformin was not able to induce chemosensitization to cisplatin due to Jarid1b overexpression and p53 downregulation. Also, on the p53 KO cells H1299, metformin was not able to induce chemosensitization to cisplatin. Jarid1b inhibition during pretreatment with low dose of cisplatin on A549 cells restores p53 expression, allowing metformin to chemosensitize the A549 PT-Pop to cisplatin. Overexpression of p53 on the Jarid1b-high cells in the PT-Pop also restores the ability of metformin to sensitize these cells to cisplatin. Metformin sensitized the p53 WT HCT 116 cells to cisplatin, but not the HCT 116 p53 KO cells. Metformin translocates p53 to the mitochondria in A549 cells and the inhibition of the p53 compartmentalization to the mitochondria protects from metformin-induced chemosensitization to cisplatin. Metformin does not lead to ROS increase on A549 cells that were not pretreated with low dose of cisplatin. Only on PT-Pop, metformin was able to increase ROS levels. In the PT-Pop, where Jarid1b was inhibited by PBIT, metformin was able to increase even more ROS levels on A549 cells. Also, in NSCLC, metformin was able to increase lactate production only on A549 cells that was not pretreated with low dose of cisplatin. In the PT-Pop of A549 cells and in H1299 cells, metformin could not increase lactate production.
Conclusion: Metformin needs the presence of p53 in NSCLC and colon cancer cells to lead to chemosensitization to cisplatin.
Citation Format: Tharcisio Citrangulo Tortelli, Jr., Rodrigo Esaki Tamura, Michele Tatiana Pereira Tomitao, Silvina Odete Bustos, Renata de Freitas Saito, Sarah Milani de Moraes Leandrini, Mayara D'Aurea Jacomassi, Ulysses Ribeiro, Jr., Bryan Erik Strauss, Roger Chammas. Jarid1b protects from metformin-induced chemosensitization to cisplatin through p53 downregulation in NSCLC [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A67.