Eun-Sun Choi

Effect of β-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. β-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.

Apoptotic effect of tolfenamic acid in androgen receptor-independent prostate cancer cell and xenograft tumor through specificity protein 1

Tolfenamic acid (Tol) is a non‐steroidal anti‐inflammatory drug that was reported to exhibit anticancer activity in pancreatic and colorectal cancer models. This study examined the role of Tol in the death regulation of PC‐3 and DU145 human androgen‐independent prostate cancer cells. The results showed that Tol inhibited cell growth and induced apoptosis, as evidenced by nuclear fragmentation and cleaved caspase 3 and poly(ADP‐ribose) polymerase. Tol suppressed the specificity protein 1 (Sp1) protein in both PC‐3 and DU145 cells. Tol also attenuated Sp1 mRNA and its promoter activity in DU145 cells, but did not alter them in PC‐3 cells, indicating that Tol degrades Sp1 protein in these cells. Tol also downregulated protein levels, mRNA levels and promoter activities of survivin and myeloid cell leukemia‐1, which are downstream targets of Sp1. The expressions of survivin and Mcl‐1 and cancer cell growth were lower in the PC‐3 cells treated with Sp1 interfering RNA and mithramycin A. Moreover, an oral injection of Tol decreased tumor growth and downregulated the Sp1 protein in athymic nude mice bearing DU145 cell xenografts without hepatotoxicity. Overall, Tol downregulates the Sp1 protein to inhibit growth and induce apoptosis in androgen‐refractory prostate cancers, both in vitro and in vivo, that show resistance against many chemotherapeutic agents. (Cancer Sci 2011; 102: 742–748)

Modulation of specificity protein 1 by mithramycin A as a novel therapeutic strategy for cervical cancer

Cervical cancer is the third most common cancer and the third leading cause of death among women. However, the standard treatment for cervical cancer includes cisplatin, which can cause side effects such as hematological damage or renal toxicity. New innovations in cervical cancer treatment focus on developing more effective and better-tolerated therapies such as Sp1-targeting drugs. Previous studies suggested that mithramycin A (Mith) inhibits the growth of various cancers by decreasing Sp1 protein. However, how Sp1 protein is decreased by Mith is not clear. Few studies have investigated the regulation of Sp1 protein by proteasome-dependent degradation as a possible control mechanism for the regulation of Sp1 in cancer cells. Here, we show that Mith decreased Sp1 protein by inducing proteasome-dependent degradation, thereby suppressing cervical cancer growth through a DR5/caspase-8/Bid signaling pathway. We found that prolonged Mith treatment was well tolerated after systemic administration to mice carrying cervical cancer cells. Reduction of body weight was minimal, indicating that Mith was a good therapeutic candidate for treatment of cancers in which Sp1 is involved in promoting and developing disease.

Chemopreventive effect of tolfenamic acid on KB human cervical cancer cells and tumor xenograft by downregulating specificity protein 1.

Earlier studies have shown that tolfenamic acid (Tol) exhibits anticancer activity in several cancer models by inhibiting tumor growth and angiogenesis. However, the chemopreventive effect of Tol on a cervical cancer model and the underlying mechanism of action are unknown. In this study, Tol was found to inhibit cell proliferation by inducing apoptosis without affecting cyclo-oxygenase 2 expression, but ampiroxicam did not. Tol decreases the specificity protein 1 (Sp1) mRNA and its promoter activity in KB cervical cancer cells, and the downregulation of Sp1 protein by affecting several proteins that contain GC-rich sites on their promoters. Studies using small interference RNA and an Sp1-specific inhibitor (mithramycin A) confirmed that the decrease in Sp1 by Tol affects survivin and p27. Tol also inhibited tumor growth and Sp1 protein in athymic nude mice xenografts. These results show that Tol could be a potent anticervical cancer drug that acts by regulating Sp1 protein and its downstream pathways.

The Apoptotic Effect of the Hexane Extract of Rheum undulatum L. in Oral Cancer Cells through the Down-regulation of Specificity Protein 1 and Survivin

The hexane extract of Rheum undulatum L. (HERL) has been shown to have anti-cancer activity in several cancers in vivo and in vitro. However, the anti-cancer activity of HERL and its molecular mechanism in human oral cancer cells has not been explored. Thus, the aim of this study was to elucidate the growth-inhibitory and apoptosis-inducing effects of HERL in HN22 and SCC15 oral cancer cell lines. This study shows that HERL inhibits oral cancer growth, decreases cell viability, and causes apoptotic cell death in HN22 and SCC15 cells, as characterized by morphological changes, nuclear condensation and fragmentation, the cleavage of PARP and the accumulation of cells in the sub-G1 phase. The treatment of oral cancer cells with HERL also resulted in decreased expression of specificity protein (Sp1) and its downstream protein, survivin. Therefore, our results suggest that the regulation of Sp1 and survivin plays a critical role in HERL-induced apoptosis in human oral cancer cells.

Myeloid cell leukemia-1 is a key molecular target for mithramycin A-induced apoptosis in androgen-independent prostate cancer cells and a tumor xenograft animal model.

Mithramycin A (Mith) is a natural polyketide that has been used in multiple areas of research including apoptosis of various cancer cells. Here, we examined the critical role of Mith in apoptosis and its molecular mechanism in DU145 and PC3 prostate cancer cells and tumor xenografts. Mith decreased cell growth and induced apoptosis in DU145 and PC-3 cells. Myeloid cell leukemia-1 (Mcl-1) was over-expressed in both cell lines compared to RWPE1 cells. Mith inhibited Mcl-1 protein expression in both cells, but only altered Mcl-1 mRNA levels in PC-3 cells. We also found that Mith reduced Mcl-1 protein levels through both proteasome-dependent protein degradation and the inhibition of protein synthesis in DU145 cells. Studies using siRNA confirmed that the knockdown of Mcl-1 induced apoptosis. Mith significantly suppressed TPA-induced neoplastic cell transformation through the down-regulation of the Mcl-1 protein in JB6 cells, and suppressed the transforming activity of both cell types. Mith also inhibited tumor growth and Mcl-1 levels, in addition to inducing apoptosis, in athymic nude mice bearing DU145 cell xenografts without affecting five normal organs. Therefore, Mith inhibits cell growth and induces apoptosis by suppressing Mcl-1 in both prostate cancer cells and xenograft tumors, and thus is a potent anticancer drug candidate for prostate cancer.

Methanol extract of Sanguisorba officinalis L. with cytotoxic activity against PC3 human prostate cancer cells

Sanguisorba officinalis is a natural plant that has been traditionally used for the treatment of inflammatory and metabolic diseases. Several studies have reported that its extracts exhibit anticancer, antioxidative and anti-lipid peroxidation activities. However, the effects of this plant on human prostate cancer cells have not yet been investigated. In the present study, we investigated the inhibitory effects and underlying mechanisms of a methanol extract of Sanguisorba officinalis (MESO) in PC3 human prostate cancer cells. MESO significantly decreased cell growth and induced apoptosis through the intrinsic apoptosis pathway. MESO decreased the expression levels of myeloid cell leukemia-1 (Mcl-1), a Bcl‑2‑like anti-apoptotic protein that is highly expressed in various cancer cell lines. Expression levels of the pro-apoptotic protein Bax were increased by MESO whereas those of Bak and Bcl-xL were unchanged. In addition, MESO induced the oligomerization of Bax in the mitochondrial outer membrane. These results suggest that MESO inhibits the growth of prostate cancer cells and induces apoptotic cell death by the downregulation of Mcl-1 protein expression and the oligomerization of Bax. Therefore, MESO has potential as a drug candidate for the treatment of prostate cancer.

In vitro and in vivo growth inhibition of prostate cancer by the small molecule imiquimod.

Prostate cancer is the second leading cause of cancer death in men worldwide. In the present study, we examined in vitro and in vivo antitumor effect of the small molecule imiquimod, also known as a TLR7 agonist, against prostate cancer. Imiquimod inhibited the growth of mouse (TRAMP‑C2) and human (PC-3) prostate cancer cells. Treatment with imiquimod induced cell cycle arrest at the G2/M phase in TRMPA-C2 cells, confirmed by the changes of G2/M checkpoint regulators such as reduction of cyclin B1 expression and increase of phospho-CDC2 and p21 in TRAMP-C2 cells treated with imiquimod. Flow cytometry and western blot analysis revealed that imiquimod induced direct apoptosis in TRAMP-C2 cells via a mitochondrial‑dependent pathway. Intratumoral injection with imiquimod reduced significantly tumor growth and increased apoptotic cells in mice subcutaneously implanted with TRAMP-C2 cells. Our results indicate that imiquimod can be an alternative therapeutic for locally generated prostate cancer.

In vitro apoptotic effects of methanol extracts of Dianthus chinensis and Acalypha australis L. targeting specificity protein 1 in human oral cancer cells

The aims of this study were to evaluate the apoptotic activities and molecular mechanisms of methanol extracts of Dianthus chinensis (MEDC) and Acalypha australis L. (MEAL) in human oral cancer cells.

Inhibition of specificity protein 1 by dibenzylideneacetone, a curcumin analogue, induces apoptosis in mucoepidermoid carcinomas and tumor xenografts through Bim and truncated Bid

OBJECTIVES Dibenzylideneacetone (DBA), a curcumin analogue that has anti-cancer activity in a variety of tumor cells. In this study, we investigated the apoptotic effects of DBA and its molecular mechanism in human mucoepidermoid carcinoma (MEC) cell lines and tumor xenografts. MATERIAL AND METHODS The apoptotic effects and related molecular mechanisms of DBA on MEC cell lines were evaluated using cell viability assay, DAPI staining, Western blot analysis, reverse transcriptase-polymerase chain reaction (RT-PCR) and Dual-luciferase Reporter Assay. The anti-tumor activity using in vivo were determined by Nude mouse xenograft assay and histopathological examination. RESULTS DBA decreased cell viability and induced apoptosis in MEC cells. These events were accompanied by inhibition of specificity protein 1 (Sp1). DBA did not induce major changes in Sp1 mRNA and promoter activity. Furthermore, inhibition of protein synthesis by cycloheximide demonstrated that DBA decreased Sp1 protein stability, but DBA did not attenuate phosphorylation of eIF4E. DBA also increased Bim and truncated Bid (t-Bid) via Sp1. Finally, DBA exhibited significant anti-tumor activity in athymic nude mice xenografts bearing MC-3 cells by regulating Sp1, Bim and t-Bid without any systemic toxicity. CONCLUSION These results elucidate a crucial apoptotic mechanism of DBA and suggest that DBA may be a potent anticancer drug candidate for MEC.