Quercetin Induces Antiproliferative Activity Against Human Hepatocellular Carcinoma (HepG2) Cells by Suppressing Specificity Protein 1 (Sp1).

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.

ß-lapachone suppresses the proliferation of human malignant melanoma cells by targeting specificity protein 1.

ß-lapachone (ß-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 ß-lap exhibits anti-proliferative effects on two human malignant melanoma (HMM) cell lines, G361 and SK-MEL-28. The effects of ß-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 ß-lap significantly induced apoptosis and suppressed cell viability in the HMM cells. Intriguingly, the transcription factor specificity protein 1 (Sp1) was significantly downregulated by ß-lap in a dose- and time-dependent manner. Furthermore, ß-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 ß-lap modulates Sp1 transactivation and induces apoptotic cell death through the regulation of cell cycle- and apoptosis-associated proteins. Thus, ß-lap may be used as a promising anticancer drug for cancer prevention and may improve the clinical outcome of patients with cancer.

Licochalcone A induces apoptosis in malignant pleural mesothelioma through downregulation of Sp1 and subsequent activation of mitochondria-related apoptotic pathway.

Licochalcone A (LCA) is a natural product derived from the roots of Glycyrrhiza inflata exhibiting a wide range of bioactivities such as antitumor, anti-oxidant and anti-bacterial effects. Malignant pleural mesothelioma (MPM) is an extremely aggressive type of cancer with a poor prognosis because of its rapid progression. However, LCA has not been investigated concerning its effects on MPM. Preliminarily, we observed that LCA negatively modulated not only cell growth, but also specificity protein 1 (Sp1) expression in MSTO-211H and H28 cell lines. It was found that IC50 values of LCA for growth inhibition of MSTO-211H and H28 cells were approximately 26 and 30 µM, respectively. Consistent with downregulation of Sp1, expression of Sp1 regulatory proteins such as Cyclin D1, Mcl-1 and Survivin was substantially diminished. Mechanistically, LCA triggered the mitochondrial apoptotic pathway by affecting the ratio of mitochondrial proapoptotic Bax to anti-apoptotic Bcl-xL. Bid induced loss of mitochondrial membrane potential, eventually leading to multi-caspase activation and increased sub-G1 population. Moreover, nuclear staining with DAPI highlighted nuclear condensation and fragmentation of apoptotic features. Flow cytometry analyses after staining cells with Annexin V and propiodium iodide corroborated LCA-mediated apoptotic cell death of MPM cells. In conclusion, these results present that LCA may be a potential bioactive material to control human MPM cells by apoptosis via the downregulation of Sp1.

Esculetin (6,7-dihydroxycoumarin): a potential cancer chemopreventive agent through suppression of Sp1 in oral squamous cancer cells.

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.

Manumycin A from a new Streptomyces strain induces endoplasmic reticulum stress-mediated cell death through specificity protein 1 signaling in human oral squamous cell carcinoma.

Manumycin A (Manu A) is a natural antibiotic produced by new Streptomyces strain, exhibiting antitumor and anticancer effects. However, the anticancer effects of Manu A on oral squamous cell carcinoma (OSCC) have not been reported. OSCC is an aggressive type of cancer because of its poor prognosis and low survival rate despite advanced medical treatment. We observed that Manu A reduced cell growth and Sp1 protein levels in OSCC cell lines (HN22 and HSC4) in a dose- and time-dependent manner. We also observed downregulation of Sp1 downstream target genes such as p27, p21, Mcl-1 and survivin. Moreover, nuclear staining with DAPI showed that Manu A was able to cause nuclear condensation and further fragmentation. Flow cytometry analyses using Annexin V and propiodium iodide supported Manu A-mediated apoptotic cell death of OSCC cells. Furthermore, Bcl-2 family such as mitochondrial pro­apoptotic Bax, anti-apoptotic Bcl-xl and Bid were regulated by Manu A, triggering the mitochondrial apoptotic pathway. In conclusion, these results indicate that Manu A is a potential to treat human OSCC via cell apoptosis through the downregulation of Sp1.

Downregulation of Sp1 is involved in ß-lapachone-induced cell cycle arrest and apoptosis in oral squamous cell carcinoma.

ß-lapachone (ß-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 ß-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 ß-lap and its underlying signaling pathway. We demonstrated that ß-lap-treated cells significantly reduced cell proliferation but increased DNA condensation and increased sub-G1 population in OSCCs. Particularly, ß-lap suppresses activation of transcription factor specificity protein 1 (Sp1) followed by apoptosis in a concentration-dependent manner in OSCCs. Furthermore, ß-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 ß-lap was able to modulate Sp1 transactivation and induce apoptosis through the regulation of cell cycle and apoptosis-related proteins. Therefore, ß-lap may be used in cancer prevention and therapies to improve clinical outcome as an anticancer drug candidate.

Role of transcription factor Sp1 in the 4-O-methylhonokiol-mediated apoptotic effect on oral squamous cancer cells and xenograft.

Recently, biphenolic components derived from the Magnolia family have been studied for anti-cancer, anti-stress, and anti-inflammatory pharmacological effects. However, the pharmacological mechanism of action of 4-O-methylhonokiol (MH) is not clear in oral cancer. The aim of this study was to investigate the role of MH in apoptosis and its molecular mechanism in oral squamous cell carcinoma (OSCC) cell lines, HN22 and HSC4, as well as tumor xenografts. Here, we demonstrated that MH decreased cell growth and induced apoptosis in HN22 and HSC4 cells through the regulation of specificity protein 1 (Sp1). We employed several experimental techniques such as MTS assay, DAPI staining, PI staining, Annexin-V/7-ADD staining, RT-PCR, western blot analysis, immunocytochemistry, immunohistochemistry, TUNEL assay and in vivo xenograft model analysis. MH inhibited Sp1 protein expression and reduced Sp1 protein levels via both proteasome-dependent protein degradation and inhibition of protein synthesis in HN22 and HSC4 cells; MH did not alter Sp1 mRNA levels. We found that MH directly binds Sp1 by Sepharose 4B pull-down assay and molecular modeling. In addition, treatment with MH or knocking down Sp1 expression suppressed oral cancer cell colony formation. Moreover, MH treatment effectively inhibited tumor growth and Sp1 levels in BALB/c nude mice bearing HN22 cell xenografts. These results indicated that MH inhibited cell growth, colony formation and also induced apoptosis via Sp1 suppression in OSCC cells and xenograft tumors. Thus, MH is a potent anti-cancer drug candidate for oral cancer.

Licochalcone A, a natural chalconoid isolated from Glycyrrhiza inflata root, induces apoptosis via Sp1 and Sp1 regulatory proteins in oral squamous cell carcinoma.

Licochalcone A (LCA), a chalconoid derived from root of Glycyrrhiza inflata, has been known to possess a wide range of biological functions such as antitumor, anti-angiogenesis, antiparasitic, anti-oxidant, antibacterial and anti-inflammatory effects. However, the anticancer effects of LCA on oral squamous cell carcinoma (OSCC) have not been reported. Our data showed that LCA inhibited OSCC cell (HN22 and HSC4) growth in a concentration- and time-dependent manner. Mechanistically, it was mediated via downregulation of specificity protein 1 (Sp1) expression and subsequent regulation of Sp1 downstream proteins such as p27, p21, cyclin D1, Mcl-1 and survivin. Here, we found that LCA caused apoptotic cell death in HSC4 and HN22 cells, as characterized by sub-G1 population, nuclear condensation, Annexin V staining, and multi-caspase activity and apoptotic regulatory proteins such as Bax, Bid, Bcl(-xl), caspase-3 and PARP. Consequently, this study strongly suggests that LCA induces apoptotic cell death of OSCC cells via downregulation of Sp1 expression, prompting its potential use for the treatment of human OSCC.