3.3. Regulation of cell cycle progression and alteration of apoptosis
induction by TD and LB
To determine whether TD and LB affect to cell cycle progression
and mitochondrial apoptotic events, we analyzed the expression of
the p21 and mitochondria-mediated apoptotic proteins. The
results showed that TD induced a significant expression of p21 at 120 h and bax at 96 h, and reduced the bcl-2 expression at 120 h
in MCF-7 cells (Fig. 4A and C). After treatment with TD, bcl-2 in
MDA-MB-231 cells were down-regulated at 96 h, while the p21,
bax and cytochrome C proteins were up-regulated at 24, 24 and
72 h, respectively (Fig. 4B and D). Moreover, the MCF-7 cells
treatment with LB resulted in a significant suppression of bcl-2 at
24 h, and then the down-regulation continued up to 120 h (Fig. 5A
and C). In addition, cytochrome C in MCF-7 cells was up-regulated
at 72 h. LB also evidently increased the level of p21, bax and
cytochrome C in MDA-MB-231 cells at 24, 24 and 96 h, respectively
(Fig. 5B and D). These observations suggest that TD and LB are
capable of arresting the cell cycle and activating intrinsic apoptotic
pathways in breast cancer cell lines.