Esculetin (6,7-dihydroxycoumarin), a coumarin compound, is known to inhibit proliferation and induce apoptosis in several types of human cancer cells and is regarded as a promising chemotherapeutic agent. The purpose of the present study was to investigate the anti-proliferative effects of esculetin on two oral squamous cell carcinoma (OSCC) cell lines, HN22 and HSC4, through regulation of specificity protein 1 (Sp1). We examined the apoptotic effects of esculetin were measured by MTS assay, DAPI staining, Annexin V, PI staining, RT-PCR, western blot analysis and immunocytochemistry in HN22 and HSC4 cells. Taken together, the results of the present study indicate that esculetin had anti-proliferative effect on the growth of OSCC cells (HN22 and HSC4) in a dose- and time-dependent manner. The treatment of HN22 and HSC4 cells with esculetin led to a significant reduction in growth and induced apoptosis, followed by the regulation of Sp1 and Sp1 regulatory protein. This indicates that esculetin inhibited cell growth and induced apoptosis by suppressing Sp1 in HN22 and HSC4 cells, suggesting it to be a potent anticancer drug candidate for oral cancer.

β-lapachone (β-lap) is a naturally occurring quinone obtained from the bark of lapacho tree (Tabebuia avellanedae) with anti-proliferative properties against various cancers. The present study investigated the cell proliferation and apoptosis effect of β-lap on two oral squamous cell carcinoma lines (OSCCs). We carried out a series of 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl-2H-tetrazolium (MTS) assays, 4',6-diamidino-2-phenylindole (DAPI) staining, cell cycle analysis, and western blot analysis to characterize β-lap and its underlying signaling pathway. We demonstrated that β-lap-treated cells significantly reduced cell proliferation but increased DNA condensation and increased sub-G1 population in OSCCs. Particularly, β-lap suppresses activation of transcription factor specificity protein 1 (Sp1) followed by apoptosis in a concentration-dependent manner in OSCCs. Furthermore, β-lap modulated protein expression levels of cell cycle regulatory proteins and apoptosis-related proteins that are known as Sp1 target genes, resulting in apoptosis. Our results collectively indicated that β-lap was able to modulate Sp1 transactivation and induce apoptosis through the regulation of cell cycle and apoptosis-related proteins. Therefore, β-lap may be used in cancer prevention and therapies to improve clinical outcome as an anticancer drug candidate.

Preclinical Research Quercetin, found in red onions and red apple skin can induce apoptosis insome malignant cells. However, the apoptotic effect of quercetin in hepatocellular carcinoma HepG2 cells via regulation of specificity protein 1 (Sp1) has not been studied. Here, we demonstrated that quercetin decreased cell growth and induce apoptosis in HepG2 cells via suppression of Sp1 using 3-(4,5-dimethyl-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay, 4',6-diamidino-2-phenylindole (DAPI) staining, Annexin V, and Western blot analysis, an effect that was dose- and time-dependent manner. Treatment of HepG2 cells with quercetin reduced cell growth and induced apoptosis, followed by regulation of Sp1 and Sp1 regulatory protein. Taken together, the results suggest that quercetin can induce apoptotic cell death by regulating cell cycle and suppressing antiapoptotic proteins. Therefore, quercetin may be useful for cancer prevention. Drug Dev Res 76 : 9-16, 2015.

β-lapachone (β-lap), a novel natural quinone derived from the bark of the Pink trumpet tree (Tabebuia avellanedae) has been demonstrated to have anticancer activity. In this study, we investigated whether β-lap exhibits anti-proliferative effects on two human malignant melanoma (HMM) cell lines, G361 and SK-MEL-28. The effects of β-lap on the HMM cell lines were investigated using 3-(4,5-dimethylthiazol-2-yl)‑5-(3-carboxymethoxyphenyl)‑2-(4-sulfophenyl-2H-tetrazolium (MTS) assay, 4',6-diamidino-2-phenylindole (DAPI) staining, Annexin V and Dead cell assay, mitochondrial membrane potential (MMP) assay and western blot analysis. We demonstrated that β-lap significantly induced apoptosis and suppressed cell viability in the HMM cells. Intriguingly, the transcription factor specificity protein 1 (Sp1) was significantly downregulated by β-lap in a dose- and time-dependent manner. Furthermore, β-lap modulated the protein expression level of the Sp1 regulatory genes including cell cycle regulatory proteins and apoptosis-associated proteins. Taken together, our findings indicated that β-lap modulates Sp1 transactivation and induces apoptotic cell death through the regulation of cell cycle- and apoptosis-associated proteins. Thus, β-lap may be used as a promising anticancer drug for cancer prevention and may improve the clinical outcome of patients with cancer.