Cucurbitacin B (cucB) is a triterpenoid constituent of Cucurbitaceae vegetables and a promising phytochemical for cancer prevention. However, the mechanism of anti-tumor activity of cucB remains unknown, especially in colon cancers. Here, we demonstrate for the first time that cucB inhibited growth of human colon cancer SW480 cells through a reactive oxygen species (ROS)-dependent mechanism. CucB induced G(2) phase arrest and apoptosis in a dose-dependent manner. At the molecular level, cucB reduced the expression of cyclin B1 and cdc25C proteins and activated caspases in SW480 cells. On the other hand, the state of phosphorylation of signaling transducer and activator of transcription 3 (STAT3) was unchanged. We found that cucB increased intracellular ROS levels, and N-acetylcysteine, a well-known antioxidant, reduced the changes in expression of the molecules, and suppressed both G(2) arrest and apoptosis. These results suggested that cucB induced G(2) arrest and apoptosis through a STAT3-independent but ROS-dependent mechanism in SW480 cells.

Dehydrozingerone (1) is a pungent constituent present in the rhizomes of ginger (Zingiber officinale) and belongs structurally to the vanillyl ketone class. It is a representative of half the chemical structure of curcumin (2), which is an antioxidative yellow pigment obtained from the rhizomes of turmeric (Curcuma longa). Numerous studies have suggested that 2 is a promising phytochemical for the inhibition of malignant tumors, including colon cancer. On the other hand, there have been few studies on the potential antineoplastic properties of 1, and its mode of action based on a molecular mechanism is little known. Therefore, the antiproliferative effects of 1 were evaluated against HT-29 human colon cancer cells, and it was found that 1 dose-dependently inhibited growth at the G2/M phase with up-regulation of p21. Dehydrozingerone additionally led to the accumulation of intracellular ROS, although most radical scavengers could not clearly repress the cell-cycle arrest at the G2/M phase. Furthermore, two synthetic isomers of 1 (iso-dehydrozingerone, 3, and ortho-dehydrozingerone, 4) were also examined. On comparing of their activities, accumulation of intracellular ROS was found to be interrelated with growth-inhibitory effects. These results suggest that analogues of 1 may be potential chemotherapeutic agents for colon cancer.

Methylglyoxal is an essential component in glycolysis and is known to be an inducer of apoptosis. Glyoxalase I (GLO1) metabolizes and inactivates methylglyoxal. GLO1 is known to be overexpressed in cancer cells and causes resistance to anticancer agents. We show for the first time that methylglyoxal treatment or the silencing of GLO1 enhances sensitivity to the promising anticancer agent TRAIL in malignant tumor cells. Methylglyoxal suppressed the expression of antiapoptotic factors, X-linked inhibitor of apoptosis protein (XIAP), survivin, cIAP1, Bcl-2, and Bcl-xL, without affecting TRAIL receptors, DR4 and DR5. Knockdown of XIAP or survivin by siRNA also enhanced TRAIL-induced apoptosis, indicating that downregulation of XIAP and survivin expression by methylglyoxal contributes to the enhancement of TRAIL activity. Furthermore, methylglyoxal decreased NF-kB activity with or without TRAIL treatment. On the other hand, the knockdown of GLO1 by siRNA enhanced TRAIL-induced apoptosis via the downregulation of XIAP and survivin expression. In conclusion, our results strongly suggest that sensitivity to TRAIL is increased by inhibition of the glyoxalase pathway and that the combination of TRAIL with methylglyoxal or glyoxalase inhibitors may be useful for a novel combination chemotherapy. Mol Cancer Ther; 11(10); 2294-300. Ó2012 AACR.

Keloids are fibroproliferative diseases characterized by the accumulation of an extracellular matrix including collagen. Various growth factors, or cytokines, and their receptors are overexpressed in keloids, and they are expected to be therapy targets. Sulforaphane, a dietary isothiocyanate, has recently shown anti-tumor, anti-inflammatory, and anti-fibrotic properties. In this study, we found that sulforaphane inhibited cell growth and reduced collagen at the mRNA and protein levels in keloid fibroblasts. Moreover, sulforaphane markedly suppressed the expression of IL-6 and α-SMA and inhibited Stat3 and Smad3 signaling pathways in keloid fibroblast KF112 cells. Sulforaphane induced G2/M cell-cycle arrest with the induction of p21 in KF112 cells. In addition, sulforaphane inhibited cell growth and suppressed the expression of collagen in keloid fibroblasts under a coculture with peripheral blood mononuclear cells. Furthermore, sulforaphane suppressed IL-6, Stat3, and Smad3 signaling in the coculture system. This study suggests that sulforaphane may be a novel keloid treatment.