Abstract

Lung cancer is the leading cause of cancer deaths in the world. To find a natural product that can be used in chemoprevention of lung cancer are the promising strategy for cancer prevention and therapy. In this study, we explore the contents of α-tocotrienol and γ-tocotrienol, a subgroup of vitamin E, in Thai rice and investigate their mechanisms underlying their anti-cancer activities on the human alveolar epithelial adenocarcinoma A549 cells. The results showed that Thai rice contained both α-tocotrienol and γ-tocotrienol, but the contents were found to be different when compared with rice varieties and areas of cultivation. Furthermore, γ-tocotrienol, but not α-tocotrienol, significantly inhibited A549 cell viability and proliferation in a dose- and time-dependent manner. γ-Tocotrienol treatment induces G0/G1 arrest and apoptosis induction in A549 cells as shown in the appearance of cell blebing, increase of the poly (ADP-ribose) polymerase cleavage, and caspase-3 activation which were the signs of apoptosis. These apoptosis-associated phenomena were mediated via both intrinsic pathway (caspase-9 activation, overexpession of bax protein, and downexpression of bcl-xL protein) and extrinsic pathway (caspase-8 activation). Thus, our findings revealed that Thai rice contains both α-tocotrienol and γ-tocotrienol. Moreover, γ-tocotrienol but not α-tocotrienol has a potential to be the promising chemopreventive agent for human lung cancer.

Key words: α-Tocotrienol, γ-tocotrienol, A549 cell viability and proliferation.