Bcl-2, cytochrome C and bax play a major role in determining
whether cells will undergo apoptosis. This study’s results revealed
that TD and LB stimulate apoptosis through down-regulated bcl-2,
and up-regulated bax and cytochrome C expression. However, in this
study, the cytochrome C level did not increase with TD treatment,
and LBdidnot change the level ofbaxin MCF-7cells. Thisimpliesthat
TD and LB may act differently on molecules involved in the apoptosis
pathway in different types of cancercells. Likewise, luteolin has been
reported to directly decrease the expression of the bcl-2 protein [35].
One study reported that genistein, with a structure similar to TD,
inhibited cell growth and induced cell apoptosis via the induction of
bax and down-regulation of bcl-2 in MDA-MB-231 cell lines [33].
Haidara and colleagues reported that casticin, a
flavonoid, can
directly down-regulate the anti-apoptotic protein bcl-2, making
apoptotic death possible [17]. Moreover, apigenin and luteolin have
been reported to significantly increase the level of pro-apoptotic
cytosolic cytochrome C [18].
Our
findings suggest that TD and LB exert growth-inhibitory
effects on MCF-7, MDA-MB-231 and MDA-MB-468 cells. Moreover,
TD and LB induced cell cycle arrest through the regulation of p21,
and triggered apoptosis via mitochondrial pathways by inhibiting
bcl-2 expression, inducing bax expression and the cytochrome C
release in human breast cancer cells (Fig. 6). These results provide
further support for TD and LB as novel chemotherapeutic agents for
breast cancer treatment. Further investigation, binding or target
molecule and in vivo studies in animal models, would provide more
evidence concerning the anti-cancer effects and possible further
therapeutic value of TD and LB.