Sulforaphane suppresses TNF-alpha-mediated activation of NF-kappaB and induces apoptosis through activation of reactive oxygen species-dependent caspase-3

Targeting COX-2 expression by natural compounds: a promising alternative strategy to synthetic COX-2 inhibitors for cancer chemoprevention and therapy

Cyclooxygenase (COX)-2 is a pro-inflammatory immediate early response protein, chronically up-regulated in many pathological conditions. In autoimmune diseases, it is responsible for degenerative effects whereas in cancer, it correlates with poor prognosis. A constitutive expression of COX-2 is triggered since the earliest steps of carcinogenesis. Consequently, strategies aimed at inhibiting COX-2 enzymatic activity have been clinically applied for the treatment of autoimmune disorders; in addition, the same approaches are currently investigated for anti-cancer purposes. However, COX-2 protein inhibitors (i.e., NSAIDs and COXIBs) are not amenable to prolonged administration since they may cause severe side effects, and efforts are underway to identify alternative approaches for chemoprevention/therapy. COX-2 expression is a multi-step process, highly regulated at transcriptional and post-transcriptional levels. Defects in the modulation of one or both of these steps may be found in pathological conditions. Targeting COX-2 expression may therefore represent a promising strategy, by which the same preventive and therapeutic benefits may be gained while avoiding the severe side effects of COX-2 enzymatic inhibition. Naturally occurring compounds derived from plants/organisms represent a huge source of biologically active molecules, that remains largely unexplored. Derived from plants/organisms used in traditional forms of medicine or as dietary supplements, these compounds have been experimentally investigated for their anti-inflammatory and anti-cancer potential. In this review, we will analyze how natural compounds may modulate the multistep regulation of COX-2 gene expression and discuss their potential as a new generation of COX-2 targeting agents alternative to the synthetic COX-2 inhibitors.

Reactive oxygen species-mediated endoplasmic reticulum stress and mitochondrial dysfunction contribute to cirsimaritin-induced apoptosis in human gallbladder carcinoma GBC-SD cells

In this study, the anticancer effect of cirsimaritin, a natural flavonoid, against human gallbladder carcinoma cell line GBC-SD and the underlying mechanisms were investigated. Cirsimaritin inhibited the growth of tumor cells and induced mitochondrial apoptosis in GBC-SD cells. In addition, cirsimaritin triggered endoplasmic reticulum (ER) stress and down-regulated the phosphorylation of Akt, while knock-down of CHOP dramatically abrogated the inactivation of Akt and reversed the pro-apoptotic effect of cirsimaritin. Furthermore, cirsimaritin provoked the generation of reactive oxygen species in GBC-SD cells, while the antioxidant N-acetyl cysteine almost completely blocked the activation of ER stress and apoptosis, suggesting cirsimaritin-induced reactive oxygen species is an early event that triggers ER stress mitochondrial apoptotic pathways in GBC-SD cells.

The role of cyclooxygenase-2 in cell proliferation and cell death in human malignancies

It is well admitted that the link between chronic inflammation and cancer involves cytokines and mediators of inflammatory pathways, which act during the different steps of tumorigenesis. The cyclooxygenases (COXs) are a family of enzymes, which catalyze the rate-limiting step of prostaglandin biosynthesis. This family contains three members: ubiquitously expressed COX-1, which is involved in homeostasis; the inducible COX-2 isoform, which is upregulated during both inflammation and cancer; and COX-3, expressed in brain and spinal cord, whose functions remain to be elucidated. COX-2 was described to modulate cell proliferation and apoptosis mainly in solid tumors, that is, colorectal, breast, and prostate cancers, and, more recently, in hematological malignancies. These findings prompt us to analyze here the effects of a combination of COX-2 inhibitors together with different clinically used therapeutic strategies in order to further improve the efficiency of future anticancer treatments. COX-2 modulation is a promising field investigated by many research groups.

Anti-apoptotic effect of the basic helix-loop-helix (bHLH) transcription factor DEC2 in human breast cancer cells

DEC1 (BHLHB2/Stra13/Sharp2) and DEC2 (BHLHB3/Sharp1) are basic helix-loop-helix (bHLH) transcription factors that are involved in circadian rhythms, differentiation and the responses to hypoxia. We examined whether DEC1 and DEC2 are involved in apoptosis regulation, in human breast cancer MCF-7 cells. We found that siRNA-mediated knockdown of DEC2 resulted in marked enhancement of apoptosis compared with that in control cells transfected with nonspecific siRNA. However, knockdown of DEC1 by siRNA did not affect cell survival. Knockdown of DEC2 affected the expression of mRNA or proteins related to apoptosis, such as Fas, c-Myc, caspase-8, poly (ADP-ribose) polymerase (PARP) and Bax. We also showed that tumor necrosis factor-alpha (TNF-alpha) up-regulates the expression of DEC1 and DEC2. DEC2 over-expression caused by the transfection of an expression vector reduced the amounts of cleaved PARP and caspase-8 induced by TNF-alpha treatment, whereas DEC1 over-expression increased it. Finally, we revealed that treatment with double knockdown against both DEC1 and DEC2 decreased the amounts of cleaved PARP and caspase-8 induced by DEC2 siRNA with or without TNF-alpha. These data indicate that DEC2 has an anti-apoptotic effect, whereas DEC1 has a pro-apoptotic effect, which are involved in the balance of survival of human breast cancer MCF-7 cells.

Sulforaphane induces G2-M arrest and apoptosis in high metastasis cell line of salivary gland adenoid cystic carcinoma

New chemotherapeutic strategy should be investigated to enhance clinical management in salivary gland adenoid cystic carcinoma (ACC). Recently, sulforaphane (SFN), as a natural compound from cruciferous vegetables exhibits a potent anti-cancer activity in various tumor cells, but remains uncertain in ACC cells. The present study examined whether SFN suppresses proliferation and in ACC cells, if so, the possible molecular targets would be further investigated. Cell survives, apoptosis, cell cycle progression and molecular targets were identified by multiple detecting techniques, including trypan blue dye exclusion assay, electron microscopy, AO/EB staining, flow cytometry and immunoblotting in human lung high metastasis cell line of salivary gland adenoid cystic carcinoma (ACC-M). The results showed that 5-20 microM SFN suppressed proliferation and induced apoptosis of ACC-M cells in dose- and time-dependent manners. Cell cycle analysis demonstrated treatment of ACC-M cells with 20 microM SFN resulted in G(2)/M cell cycle arrest, which was associated with a marked decline in protein levels of G(2)/M regulatory proteins including cyclin B1 and cyclin-dependent kinase 1 (Cdk1). In terms of apoptosis, SFN increased the expression of Bax and decreased the level of Bcl-2 and subsequently triggered release of cytochrome c from mitochondria and activation of caspase-3, but Fas level and caspase-8 activity remained unchanged at all time points. Furthermore, levels of nuclear factor-kappaB (NF-kappaB) p65 in both of the cytoplasm and the nucleus have also been markedly suppressed by SFN in a time-dependent manner. Taken together, these results suggest SFN inhibits cell growth via inducing G(2)/M cell arrest and apoptosis in ACC-M cells. These events have been associated with SFN-regulated multiple targets involved in ACC-M cell proliferation. The present study provides an evidence for testing SFN efficacy in vivo and warranting future investigations to exam the clinical potential of SFN in ACC chemotherapy.