Biomedical Research

Alpha-, γ-, δ-tocotrienols and γ-tocopherol have been reported to exhibit anti-proliferation ef-fects in several human cancer cells i.e., breast (estrogen-responsive, MDA-MB-435 and estrogen non-responsive, MCF7) and prostate (androgen-sensitive, LNCaP and androgen-resistant, PC-3) via controlling the signal transduction pathways that resulted in an increase in apoptosis. In this study, we tested the effects of γ-tocotrienol, α-tocopherol and α-tocopherol acetate on the prolif-eration and apoptosis in human cervical carcinoma CaSki cells. The cells were treated with dif-ferent doses (0 to 300μM) of γ-tocotrienol, α-tocopherol and α-tocopherol acetate and then the proliferation activity were determined using 5-Bromo-2'-deoxy-uridine (BrdU) detection method. Data obtained show that γ-tocotrienol efficiently inhibited the proliferation activity of CaSki cells by 93.5% to 97.8% (p<0.01, n=4) beginning with a dose of 100μM and above with IC50 value of 75μM, while α-tocopherol inhibited the proliferation activity of CaSki cells at lesser magnitude of 19.7% to 39.4% (p<0.01, n=4) beginning with a dose of 50μM and IC20 value of 300μM. On the contrary, α-tocopherol acetate showed no effect on the cell proliferation. The cells apoptotic activity after treatment with different doses of γ-tocotrienol and α-tocopherol (0 to 500μM) was measured using cellular DNA fragmentation ELISA method. In this assay, treatment with 150μM of γ-tocotrienol and 300μM of α-tocopherol had shown to enhance the maximum apoptotic activity of CaSki cells by 6.8 fold (p<0.01, n=4) and 2.7 fold (p<0.01, n=4), respectively as compared to untreated cultures. At the same doses as above, both compounds in-duced a 50% (p<0.05, n=4) and 40% (p<0.05, n=4) of nuclear apoptotic morphological changes in CaSki cells, respectively as detected using propidium iodide staining. The mechanism of ac-tion involved in γ-tocotrienol and α-tocopherol-induced apoptosis was investigated through Western blot analysis. The exposure of both compounds at 150μM and 300μM, respectively for 0, 1, 2, 3, 4, 5, 6, 12, 18, and 24 hours enhanced the expressions of p53, Bax and Caspase-3, and the activity of Caspase-3. These data suggest that p53, Bax and Caspase-3 are involved in the apoptotic signaling cascade induced by γ-tocotrienol and α-tocopherol.

Author(s): Narimah AH Hasani,Permeen A Yusoff,Khalid BAK,A Ghapor MT, Wan Ngah WZ
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