T.-T.H., Y.-F.K., D.M.O., J.M. animal model, the use of LLC-LT cells expressing luciferase allowed bioluminescence-based detection of tumor cells experiments. LLC-LT cells were inoculated into the right hind paw of C57BL/6 mice. ACEE (0.5 and 1%) was orally administered five times per week. Primary tumors were resected on day 15, and mice were sacrificed on day 45. (B) Representative images of primary tumors for the vehicle control and ACEE-treated groups. (C) Volume (mm3) of FR 167653 free base developing LLC paw tumors in vehicle and ACEE-treated mice was assessed by using a digital caliper on day 3, 6, 9, 12 and 15. Data are presented as means??SEM (n?=?5 in each group). **showed that ACEE treatment significantly reduced photon counts from the body surface of mice (Fig.?5A,B). Moreover, ACEE administered at 0.5 and 1% significantly reduced the Rabbit Polyclonal to MB number of lung metastatic nodules compared with the control group (Fig.?5C,D). As expected, ACEE treatment (1%) starting on day 2 produced higher?anti-metastatic?activity than treatment starting on day 15 (Fig.?5ACD).?The number and size of micrometastatic nodules per field was also significantly lower in ACEE-treated groups compared with the control group, as assessed in H&E-stained lung tissues (Fig.?5E). These results reveal that ACEE produces antitumor and anti-metastatic effects in animals. Open in a separate window Physique 5 ACEE inhibits lung metastasis of LLC cells on day 45. (C) Lung metastatic nodules were visualized to show the inhibitory effects of ACEE on LLC tumor. White arrowheads indicate metastatic nodules. (D) Number of lung metastatic nodules formed by LLC cells in each group. (E) Representative lung tissue sections were stained with H&E. Tumor tissues are marked with T. Scale bar?=?200 m. Data are presented as means??SEM (n?=?5). **by inducing cleavage of caspase-3 and by reducing P-STAT3 level. Immunohistochemistry staining was used to examine cleaved caspase-3 and P-STAT3 levels in mouse tumor tissues. Representative images of LLC cells that stained positive for cleaved caspase-3 or P-STAT3 in tumor sections obtained from control vehicle and ACEE-treated mice on day 45. Scale bar?=?100 m. Discussion Numerous studies have shown that this JAK2/STAT3 signaling pathway, which regulates many cellular processes including FR 167653 free base proliferation, survival, metastasis and angiogenesis, is usually constitutively activated in various tumor cell lines and primary tumors3,5. The JAK2/STAT3 signaling pathway therefore represents a potential target for cancer therapy21. In the present study, we observed that ACEE induces apoptosis in lung cancer cells and reduces tumor growth and metastasis in an animal model of allograft tumor in mice. Notably, ACEE significantly reduces the expression of JAK2 and P-STAT3 in LLC cells, in addition to reducing P-STAT3 level in murine allograft tumors. These results suggest that ACEE may suppress tumor growth by inhibiting the JAK2/STAT3 signaling pathway. Several anti-apoptosis proteins such as survivin and Bcl-2, which are known to be crucial for tumor survival, represent targets of the transcription factor STAT3 and are down-regulated as a consequence of STAT3 inhibition22. In cancer cells, constitutively activated STAT3 may inhibit p53 expression by binding to the p53 promoter20, thereby preventing p53-mediated apoptosis and contributing to cell survival. As a pro-apoptotic transcription factor, the p53 protein also down-regulates Bcl-2 and up-regulates Bax, thereby affecting the Bcl-2/Bax ratio and favoring apoptosis23. In the present study, we observed that ACEE treatment reduces expression of the STAT3-modulated anti-apoptotic proteins Bcl-2 and survivin in LLC cells, in addition to increasing expression FR 167653 free base of the pro-apoptotic proteins Bax and p53. ACEE also induced cleavage of apoptosis markers such as caspase-3 and PARP in LLC cells. A previous study reported that antrocin, a sesquiterpene lactone isolated from mycelium effectively inhibits tumor growth and metastasis by inducing apoptosis in lung cancer cells and LLC tumor allografts in mice. The anti-cancer effects of ACEE in lung cancer cells are mediated at least in part by down-regulation of the JAK2/STAT3 signaling pathway. These results suggest that ACEE represents a potential candidate FR 167653 free base for lung cancer treatment and the isolation of anticancer compounds. Methods Chemical reagents Cell culture media and chemical reagents including Dulbeccos altered Eagles medium (DMEM), minimum essential medium (MEM), Opti-MEM, Roswell Park Memorial Institute (RPMI) 1640, sodium pyruvate, and antibiotics were obtained commercially (Life Technologies, Grand Island, NY, USA). Fetal bovine serum (FBS) was used according to the manufacturers instructions (HyClone, Logan, UT, USA). Commercial antibodies were used to detect Src, phosphorylated-Src (Tyr416),.