Abstract
Flaxseeds have been known for their anti-cancerous effects due to the high abundance of lignans released upon ingestion. The most abundant lignan, secoisolariciresinol diglucoside (SDG), is ingested during the dietary intake of flax, and is then metabolized in the gut into two mammalian lignan derivatives, Enterodiol (END) and Enterolactone (ENL). These lignans were previously reported to possess anti-tumor effects against breast, colon, and lung cancer.
This study aims to investigate the potential anti-cancerous effect of the flaxseed lignans SDG, END and ENL on acute myeloid leukemia cells (AML) in vitro and to decipher the underlying molecular mechanism. AML cell lines, (KG-1 and Monomac-1) and a normal lymphoblastic cell line were cultured and treated with the purified lignans. ENL was found to be the most promising lignan, as it exhibits a significant selective dose- and time-dependent cytotoxic effect in both AML cell lines, contrary to normal cells. The cytotoxic effects observed were attributed to apoptosis induction, as revealed by an increase in Annexin V staining of AML cells with increasing ENL concentrations. The increase in the percentage of cells in the pre-G phase, in addition to cell death ELISA analysis, validated cellular and DNA fragmentation respectively. Analysis of protein expression using western blots confirmed the activation of the intrinsic apoptotic pathway upon ENL treatment. This was also accompanied by an increase in ROS production intracellularly. In conclusion, this study demonstrates that ENL has promising anti-cancer effects in AML cell lines in vitro, by promoting DNA fragmentation and the intrinsic apoptotic pathway, highlighting the protective health benefits of flax seeds in leukemia.
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Key Points
Even though flaxseeds lignans have shown significant potential in the prevention and treatment of various types of cancers, no studies have addressed their potential effects on leukemia. Acute myeloid leukemia (AML), one of the most commonly diagnosed types of acute leukemia in adults results from clonal expansion of myeloid progenitors in the bone marrow or peripheral blood. The main purpose of this study is to determine the effects of flaxseed derivatives on two AML cell lines, namely KG-1 and Monomac-1 cells, and to elucidate the mechanism involved in their activity.
The overall experimental approach of this study allowed the determination and validation of the selective anti-cancerous effect exhibited by the flaxseed lignan, ENL, on AML cells in vitro.
The primary results in this study exhibited that out of the three flax derivatives, ENL was the major compound that showed a dose-dependent and time-dependent anti-proliferative effect on the AML cells used, KG-1 and Monomac-1, with distinct IC50 concentrations of 60 μM and 100 μM respectively at 48 h of ENL treatment. The effects of ENL observed on AML cells lines were similar to the effects observed on prostate cells (same range of effect for the concentration up to 100 μM) and to those observed in breast cancer cells like MDA-MB-231, knowing that lignans are known to be very active against breast cancer cells. Previous studies have shown the antioxidant properties of ENL in lipid and aqueous in vitro models, mainly at low concentrations (100 μM), by linoleic acid peroxidation assay and deoxyribose assay, where a decrease in ROS levels was detected. The overall experimental approach of this study allowed the determination and validation of the selective anti-cancerous effect exhibited by the flaxseed lignan, ENL, on AML cells in vitro. ENL is a gut metabolite of SDG, the main lignan in flaxseeds. The results showed that this cytotoxicity occurs through the apoptotic pathway, specifically the intrinsic pathway. Furthermore, necroptosis induction is a possible pathway that has recently brought attention in research, thus testing the expression of key proteins like MLKL are needed, to confirm whether necroptosis is also activated by flax lignans in AML cells. Even though the results reported in this study clearly demonstrate the health benefits and protective effects of the flax seed lignan ENL in AML, further investigations are needed to confirm its effects in vivo.