Effects of vitamin E derivatives on the proliferation of KG-1 leukemic cells in vitro

Abstract

n nature, vitamin E derivatives can exist in eight different forms which are grouped in two main categories, namely Tocopherols (TP) and Tocotrienols (T3). Each category includes four derivatives which differ in the position of the methyl group, generating alpha, beta, gamma and delta subtypes. Even though all these subtypes possess antioxidant effects, several new studies report that tocotrienols are more potent than tocopherols in promoting cancer cell death. In addition to the known antioxidant effect of beta tocotrienol (β-T3), gamma tocotrienol (γ-T3) appears to have a pro-apoptotic, anti-proliferative, anti-invasive and anti-inflammatory activity in several types of cancer cells. However, the effect of the beta subtype on cancer cells is still not well studied. The present study aims to investigate and compare the effect of beta and gamma tocotrienols on the proliferation of acute myeloid leukemia cells, namely KG-1, in vitro. Cells were grown in Roswell Park Memorial Institute medium (RPMI) under optimal conditions and then treated with different doses of (β-T3) and (γ-T3) separately for 24 hours. XTT cell viability assay, which detects the presence of metabolically active cells, was used to assess cell proliferation. A decrease in proliferation of KG-1 cells was observed upon treatment with both forms of vitamin E derivatives; however, β-T3 was more potent than γ-T3 in promoting cell death with lower IC50 values. In order to determine whether the decrease in cell viability was due to apoptosis induction, Cell Death Elisa was performed to detect the degree of histone complexed DNA fragmentation, which is a hallmark of apoptosis. Cells treated with the beta subtype released more DNA fragments than the gamma form and at lower doses. Since the observed decrease in proliferation could also be due to cell cycle arrest, flow cytometry was used to quantify the number of cells in the various phases of cell cycle upon treatment with vitamin E derivatives: cells were stained with propidium iodide and DNA content quantification was performed using the C-flow software. The results obtained confirm the effect of both forms of vitamin E derivatives in promoting cell cycle arrest. In conclusion, beta and gamma tocotrienols exhibit promising anti-cancer therapeutic effects on KG1 leukemic cells in vitro. However, further studies are needed to determine the underlying molecular pathways involved in cell cycle arrest and apoptosis induction.