Targeting ERK1/2-bim signaling cascades by BH3-mimetic ABT-737 as an alternative therapeutic strategy for oral cancer.

To date, many different chemotherapeutic agents have been widely used as common treatments for oral cancers. However, their therapeutic effects have been disappointing, and these agents may have unwanted side effects. Among the many regulatory factors, overexpression of pro-survival Bcl-2 family members may promote resistance to chemotherapeutic drugs in many tumors. The BH3 domain-only proteins effectively antagonize their apoptotic activities. Therefore, there is substantial interest in developing chemotherapeutic drugs that directly target pro-survival Bcl-2 proteins by mimicking the BH3 domain and unleashing pro-apoptotic molecules in tumor cells. Among the numerous available small molecule BH3 mimetics, ABT-737, a potent small molecule that binds to Bcl-2/Bcl-xL with high affinity, has anti-tumor activity in a wide variety of cancer cells. However, the effects of ABT-737 on human oral cancers and the underlying molecular mechanisms have not previously been elucidated. In the present study, we observed that inactivation of the ERK1/2 signaling pathway using ABT-737 dramatically increased the expression of pro-apoptotic protein Bim via transcriptional and/or posttranslational regulation, in a cell type-dependent manner, inducing mitochondria-mediated apoptosis of human oral cancer cells. To the best of our knowledge, this is the first demonstration of the antitumor effects of ABT-737 on human oral cancers.

Negative regulation of adipogenesis by kaempferol, a component of Rhizoma Polygonati falcatum in 3T3-L1 cells.

Rhizoma Polygonati falcatum (RPF) has been used as a traditional herbal medicine in Asia, because of its anti-hyperglycemic, anti-triglycemic, and anti-tumor activity. In this study, we determined the anti-adipogenic potential of RPF extract and its component kaempferol in 3T3-L1 adipocytes, and the underlying molecular mechanism(s) using microarray analysis. Adipocyte differentiation of 3T3-L1 cells was significantly impaired by RPF extract and kaempferol as monitored by Oil Red O staining and quantitative measurement of lipid accumulation. Additionally, the mRNA expression of adipogenesis genes decreased on treatment with kaempferol. The role of kaempferol at the genome-wide level was further assessed by a microarray approach. Our analysis indicated that kaempferol decreased the expression of adipogenic transcription factors (Pparγ, Cebpß, Srebp1, Rxrß, Lxrß, Rorα) and genes involved in triglyceride biosynthesis (Gpd1, Agpat2, Dgat2), while increasing lipolysis-related genes, such as Tnfα, Lsr, and Cel. Finally, co-transfection assays using luciferase reporter gene and reverse transcription-polymerase chain reaction (RT-PCR) analysis using peroxisome proliferator-activated receptor-γ (PPARγ) target genes indicated that kaempferol significantly repressed rosiglitazone-induced PPARγ transcriptional activity. Overall, our data suggests that kaempferol, a major component of RPF, may be beneficial in obesity, by reducing adipogenesis and balancing lipid homeostasis partly through the down-regulation of PPARγ.

Effect of ß-phenylethyl isothiocyanate from cruciferous vegetables on growth inhibition and apoptosis of cervical cancer cells through the induction of death receptors 4 and 5.

Cruciferous vegetables have been shown to have the possibility to protect against multistep carcinogenesis. ß-Phenylethyl isothiocyanate (PEITC) is one component of these vegetables demonstrated to help fight many types of cancer. The present study examined the apoptotic effects of PEITC and its molecular mechanism in human cervical cancer cell lines (HEp-2 and KB). PEITC induced apoptosis to inhibit cell proliferation. According to the protein chip assay, PEITC increased the expression of the death receptors (DR4 and DR5) and cleaved caspase-3 compared to the DMSO treatment group. PEITC also induced caspase-8 and truncated BID. PEITC down-regulated the phosphorylation of extracellular-related kinase (ERK)1/2, whereas neither phospho-c-Jun NH(2)-terminal kinases (JNK) nor phospho-p38 MAPK was changed. The role of ERK in PEITC-induced apoptosis was also investigated using MEK inhibitor (PD98059). PD98059 increased the expression of DR4 and DR5, activated caspase-3, and cleaved PARP. In addition, PEITC decreased the phosphorylation of MEK. Therefore, the apoptotic mechanism of PEITC in cervical cancer cells involves the induction of DR4 and DR5 through the inactivation of ERK and MEK.