Abstract 990: Differential immunoregulatory effects of decitabine on lipid metabolism in doxurobicin versus tamoxifen treated breast cancer cells
Authors: Fouad Mariam , Sayed-Ahmed Mohammed 
Published: July 2021

Abstract
Background: The treatment of hormonal positive breast cancer is still based on hormonal tamoxifen (TAM) based regimens in early stages, while based on chemotherapeutic doxorubicin (DOX) based regimens in late stages. DNA methyl transferase inhibitor (decitabine: DEC) is an epigenetic modulator with synergistic anticancer activity when combined with either TAM or DOX.
Aims: The cytotoxic synergistic combinations of DEC with either DOX or TAM were examined for their effects on immunomodulation and lipid metabolism in hormonal positive breast cancer cells (MCF7).
Material and Methods: Sulphorhodamine-B cytotoxic assay, flow cytometric analysis of cell cycle and apoptosis along with the florescent uptake of Rhodamine123 were adopted for testing the sensitivity of MCF7 cells to the drug combinations. Real time PCR was utilized to measure the genetic expression of immunoregulatory markers (FOXP3, TNFα, IFNγ and IL-6), lipid metabolism regulatory markers (FASN, CPT1, MLYCD, ACCα and AMPK) and apoptosis markers (BAX, BCL2, Caspase-8, AKT, mTOR). Western Blotting was used for the determination of EGFR, CK7, LC3B proteins expressions.
Results: The combination with 500nM DEC caused synergistic 50% growth inhibition of MCF7 cells, in which the concentration required for DOX was reduced from 0.501 µM into 0.264µM, while in TAM, the concentration was reduced from 18µM into 12.4µM. The concentration of 500nM DEC induced the uptake of Rhodamine 123 and the expression of Caspase-8, IFNγ, IL-6 and AMPK in the combination with 20µM TAM or 0.25µM DOX compared with their respective single treatment concentrations. Also, both DEC combinations reduced the expressions of BAX/BCl2, EGFR, CK7, aromatase, LC3B and ACCα, but caused insignificant effect on FASN expression. The combination of 500nM DEC with 20µM TAM demonstrated significant accumulation of cells in the G0/G1 phase of the cell cycle (4.22%), and in the early apoptosis (8.97%), along with the increase of mTOR but decrease of CPT1A, MLYCD, TNFα genes expressions. On the other hand, the combination of 500nM DEC with 0.25µM DOX caused accumulation of 94.73% of cells in the late apoptosis, inhibition of the AKT and FOXP3 expressions, but induction of CPT1A.
Conclusions: Epigenetic modifier (DEC) showed different synergistic immunomodulatory effects on lipid metabolism regulation markers when combined with chemotherapy (DOX) rather than hormonal therapy (TAM) in hormonal positive breast cancer cells. DEC induces extrinsic late apoptosis through the induction of CPT1A- mediated lipid metabolism along with FOXP3 and AKT inhibition in DOX treated cells, while it induces extrinsic early apoptosis through the inhibition of MLYCD, CPT1A and TNFα in TAM treated cells.
Citation Format: Mariam Fouad, Mohammed Sayed-Ahmed. Differential immunoregulatory effects of decitabine on lipid metabolism in doxurobicin versus tamoxifen treated breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 990.