Kwon et al. BMC Cancer 2010, 10:392 http://www.biomedcentral.com/1471-2407/10/392 to its less cytotoxicity in normal cells (Additional file 1, Figure S1B). To compare cytotoxicity of cinnamon extract with anti-cancer drug (e.g, Doxorubicin), firstly we titrated and decided an optimal concentration of cin- namon extract (CE; 0.5 mg/ml) and Doxorubicin (Dox; 5 μM) [35,36] that does not induce apoptosis in normal cells. Cinnamon extract and Doxorubicin induced com- parable level of apoptosis induction in melanoma cells (CE; 60% and Dox; 70%, respectively) (Additional file 1, Figure S1B). Interestingly, however, compared with cin- namon extract, Doxorubicin showed much higher toxic effect in normal cells (primary mouse lymphocyte) (Additional file 1, Figure S1B). Doxorubicin treatment induced significantly higher levels apoptosis (up to 50%) of normal lymphocyte while cinnamon extract induced marginal effect (about 10%) (Additional file 1, Figure S1B). These results suggest a beneficial effect of cinna- mon extract with less cytotoxicity than conventional anti-cancer drug in normal cells while maintains its anti-tumor effect. However, further studies are needed to elucidate mechanism of action and core active com- pounds of cinnamon extract to induce cancer cell apop- tosis without affecting normal cells. NF B and AP1 play pivotal roles in tumorigenesis [20,21,26]. Interestingly, treatment of cinnamon extract strongly down-regulated the levels and activities of NF B and AP1 both in melanoma cell line (Figure 3) and in mouse melanoma (Figure 5). NF B is a major regulator of cell proliferation and cell survival. It inhibits apoptosis while stimulating cell proliferation, metastasis, angiogenesis and inflammation [26]. Anti-apoptotic activities of NF B is generally mediated by activation of set of genes related with cell survival [27]. Together with NF B, AP1 has also critical roles in tumorigenesis. It stimulates the expression of anti-apoptotic genes, invasive tumor growth, metastasis and angiogenesis [21]. Bcl-2, BcL-xL and survivin are key anti-apoptotic con- ductors and are target genes of NF B and AP1 [25]. Treatment of cinnamon extract significantly down-regu- lated their mRNA expression and protein levels in tumor cell line (Figure 3D and 3E) and melanoma tissue (Figure 5E and 5F) as well. These results suggest that anti-tumor effect of cinnamon extract is linked with the inhibition of NF B and AP1 and their target genes involved in tumor cell survival and proliferation. In this study, we demonstrated the anti-tumor effect of cinna- mon extract in vivo melanoma model. Although cinna- mon extracts increased apoptosis in various cancer cell lines such as lymphoma, cervical cancer and colorectal cancer (Figure 1), in vivo animal studies are necessary to test whether cinnamon extracts have also anti-tumor effects in other types of cancers. In summary, anti- tumor effects of cinnamon extract appear to be Page 9 of 10 mediated by multiple mechanisms. These include inhibi- tion of angiogenesis, potentiating CD8+ T cell cytotoxi- city [22] and apoptosis induction in tumor cells. Collectively, our work suggests the potent anti-tumor effect of cinnamon extract. Conclusions Cinnamon extract potently inhibited various tumor cell growths in vitro and suppressed in vivo melanoma pro- gression. Anti-cancer effect of cinnamon extract is mediated by apoptosis induction and blockade of NF B and AP1. Hence, cinnamon extract could lead to devel- opment of potent anti-tumor agent or complementary and alternative medicines for the treatment of diverse cancers. Additional material Additional file 1: Figure S1. Treatment of cinnamon extract induces cancer cell-specific apoptosis. Tumor specific apoptotic effects of cinnamon by comparing induction of apoptotic population between normal mouse lymphocytes and B16F10 melanoma cells upon treatment of cinnamon extract or Doxorubicin. Additional file 2: Table S1. Cinnamon treatment induced cell cycle alteration in tumor cells. After treatment of cinnamon extract for indicated times (0, 48 and 72 hrs), cell cycle analysis of each sample was performed by propidium iodide staining. Additional file 3: Figure S2. Treatment of cinnamon induces apoptosis in adenocarcinoma cell. Effects of cinnamon extract treatment into Caco2 cells (human epithelial colorectal adenocarcinoma cell line) by checking alteration of apoptotic population. Additional file 4: Figure S3. Oral administration of cinnamon extract induced cell death in tumor tissues. In vivo tumor specific apoptosis by cinnamon treatment was confirmed by checking the structural changes of nucleus in tumor tissue. Acknowledgements This work was supported by grants from the BioGreen 21 Program, Rural Development Administration (PJ007054), the Regional Technology Innovation Program of the MOCIE (RTI05-01-01) and by a Systems Biology Infrastructure Establishment Grant provided by GIST in 2010. Author details 1School of Life Sciences and Immune Synapse Research Center, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Puk-ku, Gwangju 500-712, Republic of Korea. 2Korea Institute of Oriental Medicine, Daejeon 305-811, Republic of Korea. 3Global leader program, Bugil Academy, Cheonan, Gyeonggido 330-941, Republic of Korea. 4Chosun University School of Medicine, Gwangju 501-759, Republic of Korea. Authors’ contributions HKK mainly performed this study. JSH, JSS, CGL, AS, JHR, WKJ and CRI helped some of experiments. BSK, SHL and ZYP contributed analytic tools. HKK and SHI designed the experiments and wrote the paper. All authors have read and approved the final manuscript. Competing interests The authors declare that they have no competing interests. Received: 10 December 2009 Accepted: 24 July 2010 Published: 24 July 2010