Abstract. Recent studies have revealed that 3,3-diindolylmethane (DIM) has antitumor effects in both in vivo and in vitro tumor models. However, the biological function of DIM in human gastric cancer cells is unknown. Genetic and biological studies have confirmed the importance of the novel Hippo tumor-suppressor pathway in regulating cell proliferation, apoptosis, organ size and tumorigenesis in mammals. Thus, the purpose of this study was to investigate the cytotoxic effects of DIM in human gastric cancer cells and to elucidate whether DIM induces cell death by activating the Hippo signaling pathway. Two human gastric cancer cell lines (SNU-1 and SNU-484) were used to investigate the DIM response. DIM significantly inhibited the proliferation of human gastric cancer cells in a dose-dependent manner. The percentage of G1 phase cells increased 24 h following DIM treatment. DIM reduced CDK2, CDK4, CDK6 and cyclin D1 protein levels, while increasing p53 protein levels. DIM induced the levels of cleaved poly(ADP-ribose) polymerase, cleaved-caspase-9, and diminished pro-caspase-3 protein production. In addition, DIM increased pLATS1, Mob1, pMob1, pYAP and Ras association domain family 1 (RASSF1) protein levels and reduced Yap protein production levels. DIM stimulated the binding of RASSF1 with the Mst1/2-LATS1-Mob1 complex, promoting an active Hippo signaling pathway and favoring YAP phosphorylation (pYAP) that inactivates cell proliferation. Furthermore, DIM inhibited the growth of human gastric tumors in a xenograft mouse model. These results indicate that DIM suppresses the growth of gastric cancer cells by activating the Hippo signaling pathway.

Cancer development is a complex process governed by the interaction of several signaling pathways. The Hippo and PI3K/Akt pathways have been shown to play a critical role in controlling tissue growth involved in the regulation of cell proliferation. 3, 3'-diindolylmethane (DIM) is a natural compound that selectively kills cancer cells without causing toxicity to normal cells. This study aims to investigate whether DIM has an effect on the Hippo signaling pathway mediated via the PI3K/Akt signaling pathway in colon cancer cells. Our study provides new insights into the mechanisms of crosstalk between Hippo signaling and the Akt pathway controlling cell proliferation by PI3K inhibitor and DIM treatment in colon cancer cells. DIM strongly potentiates the lethality of LY294002 in HCT116 cells and inhibits proliferation of colon cancer cells via inactivation of Akt and YAP. Thus, DIM has dramatic therapeutic effects when it is combined with the PI3K inhibitor in the treatment of colon cancer cells. These findings highlight the potential usefulness of DIM and can help develop therapeutic strategies for the prevention and treatment of colon cancer.

Despite the fact that paclitaxel and doxorubicin are widely used as chemotherapy agents against several types of cancer, their combined effects on esophageal squamous cell carcinoma (ESCC) have never been fully elucidated. The present study was designed to investigate the biological effects of paclitaxel and doxorubicin in ESCC cells. Combination treatment with paclitaxel and doxorubicin significantly inhibited the proliferation of TE-12 cells in a dose-and time-dependent manner compared to treatment with paclitaxel or doxorubicin alone. FACS analysis showed that the percentage of cells in the G2/M phase was significantly increased at 12 h after treatment with the combination. Increased p-cdc2, p-Wee1 and p53 protein levels were observed, while Akt activation was suppressed by combination treatment with paclitaxel and doxorubicin. In addition, treatment with paclitaxel plus doxorubicin significantly increased apoptosis as indicated by increased cleaved poly(ADP-ribose) polymerase and cleaved caspase-7 and -9 levels. These results suggest that combination treatment with paclitaxel and doxorubicin induced G2/M cell cycle arrest and apoptosis in human ESCC cells by suppressing Akt activity. These findings highlight the potent apoptotic effect of combination therapy with paclitaxel and doxorubicin in ESCC cells and the potential clinical benefits of these two drugs in esophageal cancer.

Multiple genetic and signaling pathway alterations underlie the development of colon cancer. We utilized genome-wide transcriptome analysis to identify important gene expression patterns following treatment with 3,3'-diindolylmethane (DIM), a natural compound derived from cruciferous vegetables, on colon cancer cells. Statistical analyses of gene expression data from DIM treated cells revealed that 692 genes were significantly upregulated, while 731 genes were down-regulated. Putative gene networks showed that several oncogenes (β-catenin, Myc and FOS) were significantly suppressed by DIM treatment. Using clinical data from colon cancer patients, activation of β-catenin was found to be significantly associated with patient prognosis by Kaplan-Meir plot analysis. We validated the mRNA and protein expression levels of c-Myc, β-catenin, and cyclin D1, all of which were significantly suppressed after DIM treatment in DLD-1 and HCT116 cells. System level characterization of our findings suggests for the first time that β-catenin and c-Myc, which are major genes involved in colon carcinogenesis, were significantly downregulated by DIM treatment in colon cancer cells. Therefore, targeting Wnt/β-catenin signaling by DIM may be an attractive strategy for the prevention and treatment of colon cancer.

Human xiphoid process appeared in morphological diversity. The anatomic structure and ossification degree of xiphoid process was well evaluated by MDCT. Our data may be used for diagnosis and surgical treatment of xiphoid process-related diseases.