Abstract 4715: Regulation of AKT and p38 MAPK by high dose butyrate may influence inflammatory cytokine expression in human U937 leukemia cells.
Authors: Pulliam Stephanie R. , Cooper Roland , Adunyah Samuel E. 
Published: August 2014

Sodium butyrate (NaB) is a sodium salt of butyric acid. It is a HDAC1 inhibitor implicated in many studies as a potential therapy for various forms of cancer. Due to its ability to promote both total and gamma globin during erythroid differentiation, low concentrations (&lt;1.5 mM) of NaB are considered a potential therapy for hemoglobin disorders including sickle cell diseases, leukemia, and β-thalassemia. Previously, high concentrations of NaB (&gt;1.5 mM) have been shown to activate apoptosis in several cancer cell lines including prostate, endometrial, breast and leukemia. Low concentrations of NaB influence multiple signaling pathways that are known mediators of cytokine production. However, it is not known whether high concentrations alter these pathways having the capacity to modulate cytokine expression in cancer cells and alter the cancer microenvironment, which is the purpose of this study. We exposed U937 leukemia cells to NaB at 5 or 10 mM doses for various time points. The culture media of the cells were harvested and analyzed by Human Multi-Analyte Cytokine ELISArray for levels of cytokines and chemotactic properties via migration assay. As evidence of apoptosis, we monitored cells for caspase-3 activation and cell viability. Our results indicate NaB induces differential expression of several inflammatory cytokines within 24 hours. Significant increases were seen in IL-5, -10, and -17A and a significant decrease for TNF-α. In monocytes, the magnitude of cytokine induction is less as compared to the leukemia cells. Moreover, monocyte migration decreased in a concentration-dependent manner to U937 cells’ exposure to NaB. Also, NaB induced at least 2-fold activation of caspase-3 and reduced cell viability by 60%. To elucidate the mechanism of cytokine expression, activation of AKT and p38 MAPK proteins were investigated using 5 mM NaB. Analyses indicate an increase in phosphorylation of p38, but a decrease in AKT activation over a 24-hour time course. This data suggests while promoting apoptosis, NaB has the potential to influence cancer microenvironment by inducing differential expression of cytokines potentially via the AKT and/or p38 MAPK pathways. This effect may influence the biology of normal and cancer cells altering the status of the patient receiving NaB therapy. *Ms Stephanie Pulliam is supported by NHLBI T32 Pre-doctoral training grant # 2 T32 HL007735-16 to Dr. Adunyah and the CTSA award No. UL1TR000445 from the National Center for Advancing Translational Sciences. Additionally, Dr. Adunyah is supported by NCI Cancer Partnership U54 grant # 5 U54 CA163069-02 and NIMHD MeTRC grant # 8 U54 MD007593-04. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Citation Format: Stephanie R. Pulliam, Roland Cooper, Samuel E. Adunyah. Regulation of AKT and p38 MAPK by high dose butyrate may influence inflammatory cytokine expression in human U937 leukemia cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4715. doi:10.1158/1538-7445.AM2013-4715