In this study, we investigated the anti-tumor effects and possible mechanisms of fucoxanthin, which has been reported to inhibit tumor proliferation and induce apoptosis in vitro or in vivo. Human gastric adenocarcinoma MGC-803 cells were treated with fucoxanthin (25μM, 50μM or 75μM). Data of flow cytometry revealed that fucoxanthin (50μM or 75μM) increased the ratio of cell in G2/M phase and apoptotic MGC-803 cells varying on a dose-dependent manner. Results from reverse transcriptase-polymerase chain reaction and Western blot showed that treatment with fucoxanthin (50μM or 75μM) significantly decreased the expressions of CyclinB1, survivin and STAT3 in MGC-803 cells in a dose-dependent manner both at the time of 24h and 48h. In addition, immunofluorescence microscopy analysis also revealed the suppressed expressions of CyclinB1 and survivin by fucoxanthin. After pretreatment with AG490 (the inhibitor for JAK/STAT signal pathway), the expressions of p-STAT3 and survivin remained also slightly lower than the vehicle control group. Co-treated with fucoxanthin (75μM) and AG490, the reduction on the expressions of STAT3, p-STAT3 and CyclinB1 by fucoxanthin were attenuated while that of survivin was enhanced. Taken together, fucoxanthin can down-regulate the expressions of CyclinB1 and survivin, inducing cell cycle arrest in G2/M phase, and apoptosis in MGC-803 cells. The reduction of CyclinB1 by fucoxanthin was associated with JAK/STAT signal pathway.
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