## 4 Anti-Cancer Activities of Tanshinones
### Anti-Proliferation and Pro-Apoptosis
#### 4.1.2 Tanshinone IIA (TIIA)  
As one of the most extensively investigated tanshinones, TIIA's anti-neoplastic activities have been reported in various cancer cells including prostate [132,133], breast [134,135,136,137,138,139,140], colon [141], lung [142,143,144,145], liver [146,147,148,149,150,151,152,153,154], stomach [155,156,157,158,159], pancreas [160], bile duct [161], kidney [162], ovary [163,164,165], cervix [166], nasopharynx [167,168], glioma [169], osteosarcoma [170] and leukemia [171,172,173,174,175], in a broad concentration range from sub-micromolar to high micromolar. Sub-apoptotic concentrations of TIIA could induce G\({}_{0}\)/G\({}_{1}\), S or G\({}_{2}\)/M arrest depending upon the cancer cell types. The induction of cell cycle arrest was associated with up-regulation of P53, P21 and P27, and down-regulation of cyclinD\({}_{1}\), CDK2, CDK4, cdc25 and cdc2 [132,141,146,147,150,155,156,162]. Higher concentrations of TIIA could induce caspase-dependent apoptosis, which was generally associated with increases of P53, P21, Fas, TNF-\(\upalpha\), Bax/Bcl-2 ratio, disruption of mitochondrial membrane potential (MMP), enhancement of cytochrome c release, decreases of survivin, Mcl-1\({}_{\rm L}\), EGFR and LC3-II, and activation of caspase-8, caspase-9 and caspase-3, suggesting the involvements of both intrinsic (Bax/Bcl-2/MMP/cytochrome c release/caspase-9/caspase3) and extrinsic (Fas/TNF-\(\upalpha\)/caspase-8/caspase-3) apoptosis pathways [132,143,144,145,146,147,151,155,162,163,169,170,171]. TIIA was reported to decrease ErbB-2/HER2/Neu in Colo205 colon cancer xenograft tumors in male severe combined immunodeficient (SCID) mice (20 mg/kg of TIIA in corn oil, oral gavage, once per day for 30 days) [141], but not in MCF-7 and MDA-MD-231 breast cancer xenograft tumors in femalenude mice (30 mg/kg of TIIA in Tween 20:ethanol = 1:99, subcutaneous (s.c.) injection, four times per week for four weeks) [137]. The differences in cell types, mouse strains and TIIA treatment solvent vehicles and routes might partially explain the inconsistent results about ErbB-2/HER2/Neu between the two studies. Endoplasmic reticulum (ER) stress-mediated cytotoxicity was reported in TIIA-treated breast cancer BT-20 cells [135]. After exposure to TIIA, ER stress markers including caspase-12 and GADD153 were increased along with decreased Bcl-xL and increased caspase-3 [135]. In addition, increases of reactive oxygen species (ROS) and cellular Ca\({}^{2+}\) concentration might also be involved in TIIA-induced apoptosis in BT-20 breast cancer cells and A549 and H146 lung cancer cells [142,143]. Interference of mitosis might be another possible mechanism of TIIA to suppress cancer cell proliferation. [PERSON] _et al._[176] found that TIIA could arrest cancer cells in mitosis phase (before metaphase-anphase transition) by disrupting the mitotic spindle, and then subsequently elicited mitochondria-dependent apoptosis. Distinct from the existing therapeutic drugs that cause G\({}_{2}\)/M arrest through interfering with the microtubule structure (such as vincristine or taxol), TIIA destroyed the mitotic spindle in mitotic cells rather than the microtubule structure in interphase cells, suggesting a preference of TIIA to kill mitotic cells over interphase cells. Moreover, the _in vivo_ pro-apoptosis activity of TIIA was also established in xenograft tumors including colon (20 mg/kg of TIIA in corn oil, oral) [141] and breast (30 mg/kg of TIIA in Tween 20:ethanol = 1:99, s.c. injection or 30 mg/kg of TIIA, _i.p._ injection, respectively) [137,138]. Several signal transduction pathways including PI3K/AKT, p38 MAPK and AP-1 pathways might be involved in the inhibitory action of TIIA. [PERSON] _et al._[133] reported that TIIA treatment reduced the expression of PI3K p85 subunit and phosphorylation of AKT and mTOR in a concentration-dependent manner.