As is shown in Fig. 7, the apoptosis pathway mediated by death receptors is the extrinsic pathway. A typical death receptor is Fas. After it binds with Fas-L in the cell membrane,
it can activate Caspase-8 and then make Caspase-3
to be activated. At last, it induces cells to apoptosis. The
mitochondrial pathway is the intrinsic pathway. It is closely
related to Bcl-2 protein family. The members are divided
into promoting apoptosis protein (Bax) and apoptosis suppression
(Bcl-2). The balance between them determines
whether apoptosis can occur.16 The stimulants in the cell,
like hypoxia,17,18 can stimulate the expression of Bcl-2
family. After that, Bax promotes mitochondria to release
Cytochrome C (Cyt-C) while Bcl-2 inhibits it. Then Cyt-C
activates Caspase-9, further activates downstream caspases,
make DNA fragment and induce the cells apoptosis.19
P53 gene dependent regulation pathway is a caspase independent
pathway. This pathway is mainly regulated by
nucleus protein P53. P53 is divided into wild and mutational
types. In our study we detected mt p53. The mechanism of
apoptosis by mt p53 is that it loses the ability to combine
with nucleus specific DNA and can’t bind with P53 binding
protein or weakly.14 At the same time, it can make the
activity of wild P53 be inhibited. Finally, cells undergoes
malignant transformation.