Abstract 1427: Sensitizing HL60 acute myeloid leukemia cells to decitabine with pterostilbene
Authors: Boycott Cayla , Stefanska Barbara 
Published: July 2021

Abstract
Introduction. Decitabine (DAC), is a DNA hypomethylating agent that has been shown to be potent towards leukemia cells at low doses. However, many patients develop resistance to the drug due to dysregulation of genes associated with responsiveness to DAC-induced DNA demethylation. To this regard, it has been reported that downregulation of TET2, one of the demethylating enzymes, increases sensitivity to DAC in acute myeloid leukemia (AML) cells. Remarkably, dietary bioactive compounds such as pterostilbene (PTS), with a stilbenoid ring structure, have previously been shown to mediate changes in gene expression through regulation of the epigenetic machinery in cancer models. Thus, we sought to test the impact of treatment of leukemia cells with PTS to augment expression of genes involved in the responsiveness of low-dose DAC in AML cells.
Methods. HL60, an AML cell line, was either treated in combination with PTS (1.0 µM) and DAC (200 nM) or pre-treated with different concentrations of PTS (0 µM, 0.5 µM, 1.0 µM, 2 µM) for four days followed by DAC treatment (100 nM) for three days. Cell growth was assessed via trypan blue dye exclusion test and comparisons were made between combination treatment and pre-treatment with PTS. qPCR was performed in triplicates for each assay to assess expression of selected genes.
Results. Treatment of HL60 cells with 200 nM DAC alone led to a 60% decrease in cell growth compared to control (treated with ethanol as a vehicle). After the combined treatment with PTS, cell growth decreased by further 27% compared to DAC alone. In order to decipher if this decrease in cell growth was due to the effect of PTS sensitizing cells to DAC, the cells were first pre-treated with PTS for four days and subsequently treated with DAC for three days. Compared to control (ethanol pre-treated cells), growth of cells treated with 100 nM DAC alone was decreased by about 37%, while growth of cells pre-treated with 0.5 µM, 1.0 µM, and 2.0 µM PTS followed by 100 nM DAC exposure was further reduced by 13%, 14.5%, and 30%, respectively. This suggests that PTS-pre-treated cells are more sensitive to DAC. Interestingly, DAC alone at 200 nM led to an increase in expression of TET2 (p&lt;0.01) while PTS at 1.0 µM alone led a decrease (p&lt;0.01) compared to control. However, when PTS and DAC were combined, TET2 levels increased significantly (p&lt;0.01) compared to both control and DAC alone, despite its better ability to inhibit growth. In order to explore this further, we will proceed with investigating the effects of pre-treatment with PTS on TET2 expression in HL60 cells.
Conclusion. Treatment of HL60 cells with PTS results in improved sensitivity of cells to low doses of DAC, possibly due to modulating TET2 expression.
Citation Format: Cayla Boycott, Barbara Stefanska. Sensitizing HL60 acute myeloid leukemia cells to decitabine with pterostilbene [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 1427.