The anti-leukaemic potential of phenolics in combination with chromatin modifying agents on an acute myeloid leukaemia cell line

Abstract

The World Health Organisation (WHO) identified cancer as the leading cause of premature mortality in most developed countries between the ages of 30 and 70 (Bray et al., 2021). Acute Myeloid Leukaemia (AML), defined as an expansion of malignant myeloid precursor cells as a result of a series of genetic and epigenetic alterations leading to differentiation arrest and unbridled cell proliferation, becomes increasingly common with advancing age (Ramos et al., 2018)(Fredly et al., 2013). While this cancer is the most prevalent leukaemia in the adult population, the rate of survival of AML steadily decreases with increasing age (Vakiti & Mewawalla, 2023)(Podoltsev et al., 2017). Differentiation therapy is a current area of active targeted anti-cancer research, especially in leukaemias, where malignant cells are induced to differentiate into more mature cells less likely to grow and divide uncontrollably. Polyphenols, naturally occurring products found in plant-based foods and beverages, are becoming increasingly popular candidates in cancer therapy due to their antiproliferative and differentiative properties on many cell types (Gatt et al., 2021)(Niedzwiecki et al., 2016)(Zhamanbayeva et al., 2016)(Fabiani et al., 2006). Furthermore, chromatin modifying agents (CMAs) have also had a similar impact on differentiation therapy as they act by reversing the epigenetic alterations that limit gene expression and differentiation (Zelent et al., 2005). In this study, the differentiation inducing effect of phenolics identified from Maltese Extra Virgin Olive Oil (EVOO) (Tyrosol, Gallic Acid, and Caffeic Acid) in combination with a CMA pre-treatment (NaBut, TSA, or 5-Aza) on the KG-1a cell line was assessed over a five-day period. The differentiating effects were indicated through the NBT and MTT assays, as well as morphology evaluation and flow cytometry confirmatory tests (cell cycle analysis and identification of CD markers). These tests were also used to assess the anti-proliferative action and induction of cell death via the phenolics combined with CMAs. Chromatin modifiers combined with phenolics such as NaBut/TSA + Tyrosol, NaBut/TSA/5-Aza + Gallic Acid, and NaBut/TSA/5-Aza + Caffeic Acid all resulted in differentiation on Day 3 or Day 5, with NaBut + Gallic Acid and 5-Aza + Caffeic Acid both showing evidence of a granulocytic commitment (CD11b+ CD14-). Most combinations inhibited proliferation via cell death or cell cycle arrest after 5 days. An important result observed was the possible induction of terminal differentiation via NaBut + Caffeic Acid and TSA with either Tyrosol or Caffeic Acid, that provides hope in the search for a cure for some subtypes of AML. However, more studies are necessary to confirm this observation. These results were not achieved when leukaemic cells were exposed to the polyphenols alone. This innovative combinatorial strategy may potentially pave the way for an alternative and safer approach in the way AML is fought against.