Cordycepin Resensitizes T24R2 Cisplatin-Resistant Human Bladder Cancer Cells to Cisplatin by Inactivating Ets-1 Dependent MDR1 Transcription.

Tumor cell resistance to anti-cancer drugs is a major obstacle in tumor therapy. In this study, we investigated the mechanism of cordycepin-mediated resensitization to cisplatin in T24R2 cells, a T24-derived cell line. Treatment with cordycepin or cisplatin (2 µg/mL) alone failed to induce cell death in T24R2 cells, but combination treatment with these drugs significantly induced apoptosis through mitochondrial pathways, including depolarization of mitochondrial membranes, decrease in anti-apoptotic proteins Bcl-2, Bcl-xL, and Mcl-1, and increase in pro-apoptotic proteins Bak and Bax. High expression levels of MDR1 were the cause of cisplatin resistance in T24R2 cells, and cordycepin significantly reduced MDR1 expression through inhibition of MDR1 promoter activity. MDR1 promoter activity was dependent on transcription factor Ets-1 in T24R2 cells. Although correlation exists between MDR1 and Ets-1 expression in bladder cancer patients, active Ets-1, Thr38 phosphorylated form (pThr38), was critical to induce MDR1 expression. Cordycepin decreased pThr-38 Ets-1 levels and reduced MDR1 transcription, probably through its effects on PI3K signaling, inducing the resensitization of T24R2 cells to cisplatin. The results suggest that cordycepin effectively resensitizes cisplatin-resistant bladder cancer cells to cisplatin, thus serving as a potential strategy for treatment of cancer in patients with resistance to anti-cancer drugs.

NDRG2 Sensitizes Myeloid Leukemia to Arsenic Trioxide via GSK3ß-NDRG2-PP2A Complex Formation.

N-Myc downstream-regulated gene 2 (NDRG2) was characterized as a tumor suppressor, inducing anti-metastatic and anti-proliferative effects in several tumor cells. However, NDRG2 functions on anticancer drug sensitivity, and its molecular mechanisms are yet to be fully investigated. In this study, we investigated the mechanism of NDRG2-induced sensitization to As2O3 in the U937 cell line, which is one of the most frequently used cells in the field of resistance to As2O3. NDRG2-overexpressing U937 cells (U937-NDRG2) showed a higher sensitivity to As2O3 than mock control U937 cell (U937-Mock). The higher sensitivity to As2O3 in U937-NDRG2 was associated with Mcl-1 degradation through glycogen synthase kinase 3ß (GSK3ß) activation. Inhibitory phosphorylation of GSK3ß was significantly reduced in U937-NDRG2, and the reduction was diminished by okadaic acid, a protein phosphatase inhibitor. NDRG2 mediated the interaction between GSK3ß and protein phosphatase 2A (PP2A), inducing dephosphorylation of GSK3ß at S9 by PP2A. Although the C-terminal deletion mutant of NDRG2 (ΔC NDRG2), which could not interact with PP2A, interacted with GSK3ß, the mutant failed to dephosphorylate GSK3ß at S9 and increased sensitivity to As2O3. Our findings suggest that NDRG2 is a kind of adaptor protein mediating the interaction between GSK3ß and PP2A, inducing GSK3ß activation through dephosphorylation at S9 by PP2A, which increases sensitivity to As2O3 in U937 cells.

NDRG2 contributes to cisplatin sensitivity through modulation of BAK-to-Mcl-1 ratio.

The downregulation of N-Myc downstream-regulated gene 2 (NDRG2) is known to be associated with the progression and poor prognosis of several cancers. Sensitivity to anti-cancer may be associated with a good prognosis in cancer patients, and NDRG2, which is induced by p53, sensitizes the cells to chemotherapy. However, the unique function of NDRG2 as an inducer of apoptosis under chemotreatment has not been sufficiently studied. In this study, we investigated the role of NDRG2 in chemo-sensitivity, focusing on cisplatin in U937 histiocytic lymphoma, which has the loss-of-functional mutation in p53. NDRG2 promoted the sensitivity to cisplatin through the modulation of the BAK-to-Mcl-1 ratio. The degradation of Mcl-1 and increase in BAK were mediated by JNK activation and the eIF2α/p-eIF2α pathway, respectively, which depended on PKR activation in NDRG2-overexpressed U937 (U937-NDRG2) cells. NOX5 was highly expressed in U937-NDRG2 cells and contributed to ROS production after cisplatin treatment. ROS scavenging or NOX5-knockdown successfully inhibited the sensitivity of U937-NDRG2 cells to cisplatin. Taken together, these findings indicate that NDRG2 contributed to the increased sensitivity to ciplatin through the modulation of Bak-to-Mcl-1 ratio regulated by NOX5-ROS-PKR pathway; therefore, we suggest that NDRG2 may be a molecular target for improving the efficacy of drug treatment in cancer patients.

Extracellular cystatin SN and cathepsin B prevent cellular senescence by inhibiting abnormal glycogen accumulation.

Cystatin SN (CST1), a known inhibitor of cathepsin B (CatB), has important roles in tumor development. Paradoxically, CatB is a member of the cysteine cathepsin family that acts in cellular processes, such as tumor development and invasion. However, the relationship between CST1 and CatB, and their roles in tumor development are poorly understood. In this study, we observed that the knockdown of CST1 induced the activity of senescence-associated ß-galactosidase, a marker of cellular senescence, and expression of senescence-associated secretory phenotype genes, including interleukin-6 and chemokine (C-C motif) ligand 20, in MDA-MB-231 and SW480 cancer cells. Furthermore, CST1 knockdown decreased extracellular CatB activity, and direct CatB inhibition, using specific inhibitors or shCatB, induced cellular senescence. Reconstitution of CST1 restored CatB activity and inhibited cellular senescence in CST1 knockdown cells. CST1 knockdown or CatB inhibition increased glycogen synthase (GS) kinase 3ß phosphorylation at serine 9, resulting in the activation of GS and the induction of glycogen accumulation associated with cellular senescence. Importantly, CST1 knockdown suppressed cancer cell proliferation, soft agar colony growth and tumor growth in a xenograft model. These results indicate that CST1-mediated extracellular CatB activity enhances tumor development by preventing cellular senescence. Our findings suggest that antagonists of CST1 or inhibitors of CatB are potential anticancer agents.

Depigmentation of α-melanocyte-stimulating hormone-treated melanoma cells by ß-mangostin is mediated by selective autophagy.

Melanogenesis is a key pathway for the regulation of skin pigmentation and the development of skin-lightening/skin-whitening drugs or cosmetics. In this study, we found that ß-mangostin from seedcases of Garcinia mangostana inhibited α-melanocyte-stimulating hormone (α-MSH)-mediated melanogenesis in B16F10 melanoma cells and a three-dimensional human skin model. ß-Mangostin significantly inhibited the protein level of tyrosinase induced by α-MSH in UPS (ubiquitin proteasome system)-independent and lysosome-dependent manner. The inhibition of autophagy by 3-methyladenine treatment or ATG5 knockdown effectively recovered premelanosome protein as well as tyrosinase degraded by the ß-mangostin treatment. However, rapamycin, a representative non-selective autophagy inducer, triggered autophagy in α-MSH-stimulated cells, which was characterized by a considerable decrease in p62, but it was unable to inhibit melanogenesis. Melanosome-engulfing autophagosomes were observed using transmission electron microscopy. Furthermore, previously formed melanin could be degraded effectively in an autophagy-dependent manner in ß-mangostin-treated cells. Taken together, our results suggest that ß-mangostin inhibits the melanogenesis induced by α-MSH via an autophagy-dependent mechanism, and thus, the depigmentation effect of ß-mangostin may depend on autophagy targeted at the melanosome rather than non-selective autophagy.

Cytotoxic effects of kazinol A derived from Broussonetia papyrifera on human bladder cancer cells, T24 and T24R2.

BACKGROUND: Broussonetia papyrifera (B. papyrifera), also known as paper mulberry, has been used as a traditional medicine for the treatment of several diseases, including ophthalmic disorders and impotency. However, the biological activity of kazinol A (1) among flavonols isolated from B. papyrifera has not been identified. PURPOSE: We identified a candidate metabolite for anti-human bladder cancer treatment from B. papyrifera and investigated the possible molecular mechanisms underlying its cytotoxic effects in T24 and cisplatin-resistant T24R2 human bladder cancer cells. METHODS: T24 and T24R2 cells were treated with five flavonols from B. papyrifera and their cytotoxic effects were determined using MTT assay, cell cycle analysis, mitochondrial membrane potential, and propidium iodide staining. Autophagy rate was calculated by counting LC3-GFP dots in the cells. All related protein expressions were analyzed by immunoblotting. RESULTS: Compound 1 showed relatively higher cytotoxicity in the human bladder cancer cells, T24 and T24R2, rather than other tissues-originated cancer cells. Compound 1 significantly attenuated cell growth through G0/1 arrest mediated by a decrease in cyclin D1 and an increase of p21. Apoptosis and autophagy induced by compound 1 treatment was accompanied by a modulation of the AKT-BAD pathway and AMPK-mTOR pathway, respectively. CONCLUSIONS: Our results suggest that compound 1 induces cytotoxic effects in human bladder cancer cells, including the cisplatin-resistant T24R2. Compound 1 may be a candidate for the development of effective anti-cancer drug on human urinary bladder cancer.

Liposome-encapsulated CpG enhances antitumor activity accompanying the changing of lymphocyte populations in tumor via intratumoral administration.

Although oligodeoxynucleotides containing CpG motifs (CpG-ODN) are potent immune stimulators, the use of natural CpG-ODN--phosphodiester-backbone CpG--has been limited due to its instability by nuclease in vivo. The aim of this study is to investigate the anticancer efficiency of CpG-ODN capsulated using liposome, which enhances the stability of CpG-ODN. We formulated lipoplex, encapsulated natural CpG-ODN from Mycobacterium bovis with liposome, and tested its immune stimulatory activity in vitro and in vivo. The lipoplex induced a systemic innate immune response in vivo and stimulated dendritic cells, but not macrophages, to stimulate proinflammatory cytokines such as tumor necrosis factor alpha and interleukin-6 in vitro. As expected, the lipoplex effectively mediated the prolonged cancer-therapeutic activity against B16 melanoma, which was dependent on natural killer and CD8(+) T cells. The therapeutic activity was observed after only intratumoral administration of lipoplex among several treatment routes. Intratumoral treatment of lipoplex significantly increased the populations of natural killer and CD8(+) T cells and reduced regulatory CD4(+) T cell recruitment, which was correlated with expression profiles of chemokines (CCL1, CCL3, CXCL1, CXCL10, and CCL22). The antitumor therapeutic effect of lipoplex was dependent on the altered lymphocyte population that might be developed by the profile of intratumoral chemokine expression.

Ciglitazone, a peroxisome proliferator-activated receptor gamma ligand, inhibits proliferation and differentiation of th17 cells.

Peroxisome proliferator-activated receptor gamma (PPARγ) was identified as a cell-intrinsic regulator of Th17 cell differentiation. Th17 cells have been associated with several autoimmune diseases, including experimental autoimmune encephalomyelitis (EAE), inflammatory bowel disease (IBD), and collagen-induced arthritis. In this study, we confirmed PPARγ-mediated inhibition of Th17 cell differentiation and cytokine production at an early stage. Treatment with ciglitazone, a PPARγ ligand, reduced both IL-1ß-mediated enhancement of Th17 differentiation and activation of Th17 cells after polarization. For Th17 cell differentiation, we found that ciglitazone-treated cells had a relatively low proliferative activity and produced a lower amount of cytokines, regardless of the presence of IL-1ß. The inhibitory activity of ciglitazone might be due to decrease of CCNB1 expression, which regulates the cell cycle in T cells. Hence, we postulate that a pharmaceutical PPARγ activator might be a potent candidate for treatment of Th17-mediated autoimmune disease patients.

6-Acetonyl-5,6-dihydrosanguinarine (ADS) from Chelidonium majus L. triggers proinflammatory cytokine production via ROS-JNK/ERK-NFκB signaling pathway.

Chelidonium majus L. is an herbal plant that is commonly used in Western phytotherapy and traditional Chinese medicine for diuretic, antitussive, eye-regenerative, anti-osteoporotic, and radioprotective purposes. In this study, we purified 6-acetonyl-5,6-dihydrosanguinarine (ADS) from C. majus and investigated its immune-stimulatory effect. We found that ADS has the potential to induce the inflammatory cytokines TNF-α, IL-6, and IL-8 in macrophages and dendritic cells (DCs), that NFκB activation is a critical mediator of ADS-induced cytokine production, and that the activation of NFκB was dependent on reactive oxygen species (ROS). ADS induced phosphorylation of ERK and JNK, which was also associated with NFκB activation; phosphorylarion and cytokine production were inhibited by ROS scavenger and by specific MAPK inhibitors. Taken together, the results suggest that ADS from C. majus, as a positive immune modulator, induces inflammatory cytokines that might improve immunity, via the ROS-ERK/JNK-NFκB pathway.