Sirivan Athikomkulchai

Chrysin overcomes TRAIL resistance of cancer cells through Mcl-1 downregulation by inhibiting STAT3 phosphorylation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) selectively kills various types of cancer cells without harming normal cells, but TRAIL resistance has been frequently observed in cancer cells. Propolis (bee glue) is a material collected from various plants by honeybees and is a rich source of bioactive compounds, including the natural flavonoid chrysin, which possesses multiple anticancer effects. We investigated the mechanism underlying the TRAIL sensitization effect of chrysin, which is a major constituent of Thai propolis, in human lung and cervical cancer cell lines. Propolis extract and chrysin sensitizes A549 and HeLa human cancer cell lines to TRAIL-induced apoptosis. The TRAIL sensitization effect of chrysin is not mediated by inhibition of TRAIL-induced NF-κB activation or by glutathione depletion. Immunoblot analysis using a panel of anti-apoptotic proteins revealed that chrysin selectively decreases the levels of Mcl-1 protein, by downregulating Mcl-1 gene expression as determined by qRT-PCR. The contribution of Mcl-1 in TRAIL resistance was confirmed by si-Mcl-1 knockdown. Among signaling pathways that regulate Mcl-1 gene expression, only constitutive STAT3 phosphorylation was suppressed by chrysin. The proposed action of chrysin in TRAIL sensitization by inhibiting STAT3 and downregulating Mcl-1 was supported by using a STAT3‑specific inhibitor, cucurbitacin-I, which decreased Mcl-1 levels and enhanced TRAIL-induced cell death, similar to that observed with chrysin treatment. In conclusion, we show the potential of chrysin in overcoming TRAIL resistance of cancer cells and elucidate its mechanism of action.

Antiausterity Agents from Uvaria dac and Their Preferential Cytotoxic Activity against Human Pancreatic Cancer Cell Lines in a Nutrient-Deprived Condition

Human pancreatic cancer cell lines are known for their inherent tolerance to nutrition starvation, which enables them to survive under a hypovascular (austerity) tumor microenvironment. The search for agents that preferentially retard the survival of cancer cells under low nutrition conditions (antiausterity agent) is a novel approach to anticancer drug discovery. In this study, it was found that a dichloromethane extract of the stem of Uvaria dac preferentially inhibited PANC-1 human pancreatic cancer cells survival under nutrition-deprived conditions at a concentration of 10 μg/mL. Workup of this bioactive extract led to the discovery of (+)-grandifloracin (8) as a potent antiausterity agent as evaluated in a panel of four human pancreatic cancer cell lines, PANC-1 (PC(50), 14.5 μM), PSN-1 (PC(50), 32.6 μM), MIA PaCa-2 (PC(50), 17.5 μM), and KLM-1 (32.7 μM). (+)-Grandifloracin (8) has been isolated from a natural source for the first time. Its absolute stereochemistry was established by single-crystal X-ray crystallography and circular dichroism spectroscopic analysis. In addition to this, seven other new highly oxygenated cyclohexene derivatives, named uvaridacanes A (1) and B (2), uvaridacols A-D (3, 4, 6, 7), and uvaridapoxide A (5), were also isolated and structurally characterized.

(+)-Grandifloracin, an antiausterity agent, induces autophagic PANC-1 pancreatic cancer cell death.

Human pancreatic tumors are known to be highly resistant to nutrient starvation, and this prolongs their survival in the hypovascular (austere) tumor microenvironment. Agents that retard this tolerance to nutrient starvation represent a novel antiausterity strategy in anticancer drug discovery. (+)-Grandifloracin (GF), isolated from Uvaria dac, has shown preferential toxicity to PANC-1 human pancreatic cancer cells under nutrient starvation, with a PC50 value of 14.5 μM. However, the underlying mechanism is not clear. In this study, GF was found to preferentially induce PANC-1 cell death in a nutrient-deprived medium via hyperactivation of autophagy, as evidenced by a dramatic upregulation of microtubule-associated protein 1 light chain 3. No change was observed in expression of the caspase-3 and Bcl-2 apoptosis marker proteins. GF was also found to strongly inhibit the activation of Akt, a key regulator of cancer cell survival and proliferation. Because pancreatic tumors are highly resistant to current therapies that induce apoptosis, the alternative cell death mechanism exhibited by GF provides a novel therapeutic insight into antiausterity drug candidates.

Uvaridacols E−H, Highly Oxygenated Antiausterity Agents from Uvaria dac

Chemical investigation of the stems of Uvaria dac yielded four new highly oxygenated cyclohexene derivatives named uvaridacols E-H (1-4). Their structures were established through NMR and circular dichroism spectroscopic analysis. Uvaridacols E (1), F (2), and H (4) displayed weak preferential cytotoxicity against PANC-1 human pancreatic cancer cells under nutrition-deprived conditions in a concentration-dependent manner, without causing toxicity in normal nutrient-rich conditions.

Wound healing activity of Pluchea indica leaf extract in oral mucosal cell line and oral spray formulation containing nanoparticles of the extract

Abstract Context: Pluchea indica (L.) Less (Asteraceae) is an herb used as a traditional medicine for wound healing. The chemical compounds found in Pluchea indica leaves are phenolic acids, flavonoids, anthocyanins and carotenoids. Objective: This study investigates the effect of Pluchea indica leaf ethanol extract and its nanoparticles (NPs) on cytotoxicity, cell survival and migration of human oral squamous carcinoma cell line. Materials and methods: Cell viability was measured using MTT assay to assess the effect of Pluchea indica leaf extract and NPs (1–500 μg/mL) on cytotoxicity and cell survival. The effect of Pluchea indica leaf extract and NPs on cell migration was determined by scratch assay. The % relative migration was calculated after 24, 48 and 72 h of treatment. Results: The sizes of Pluchea indica leaf extract NPs were in a range of nanometers. NPs possessed negative charge with the polydispersity index (PDI) smaller than 0.3. After the treatment for 24, 48 and 72 h, Pluchea indica leaf extract had IC50 value of 443.2, 350.9 and 580.5 μg/mL, respectively, whereas the IC50 value of NPs after the treatment for 24, 48 and 72 h were 177.4, 149.2 and 185.1 μg/mL, respectively. The % relative migration of cells was significantly increased when the cells were treated with 62.5 and 125 μg/mL of the extract and 62.5 μg/mL of NPs. Discussion and Conclusions: NPs increased cytotoxicity of the Pluchea indica leaf extract, increased the migration of cells at low concentration and increased colloidal stability of the extract in an oral spray formulation.

Highly oxygenated antiausterity agents from the leaves of Uvaria dac

From the chloroform extract of the leaves of Uvaria dac, four new highly-oxygenated cyclohexene derivatives named uvaridacols I-L (1-4) were isolated together with nine previously reported compounds (5-13). Their structures were determined based on the extensive NMR spectroscopic data and circular dichroism spectroscopic analysis. Among the new compounds, uvaridacol L (4) displayed strong preferential cytotoxicity in the nutrient deprived medium against five different tested pancreatic cancer cell lines, PANC-1 (PC50, 20.1μM), PSN-1 (PC50, 9.7μM), MIA PaCa-2 (PC50, 29.1μM), Capan-1 (73.0μM) and KLM-1 (25.9μM).

Chrysin Inhibits Lymphangiogenesis in Vitro

The induction of lymphangiogenesis is an important process to promote cancer growth and cancer metastasis via the lymphatic system. Identifying the compounds that can prevent lymphangiogenesis for cancer therapy is urgently required. Chrysin, 5,7-dihydroxyflavone, a natural flavone extracted from Thai propolis, was used to investigate the effect on the lymphangiogenesis process of TR-LE, rat lymphatic endothelial cells. In this study, maximal nontoxic doses of chrysin on TR-LE cells were selected by performing a proliferation assay. The process of lymphangiogenesis in vitro was determined by cord formation assay, adhesion assay and migration assay. Chrysin at a nontoxic dose (25 μM) significantly inhibited cord formation, cell adhesion and migration of TR-LE cells when compared with the control group. We also found that chrysin significantly induced vascular endothelial growth factor C (VEGF-C) mRNA expression and nitric oxide (NO) production in TR-LE cells which was involved in decreasing the cord formation of TR-LE cells. In conclusion, we report for the first time that chrysin inhibited the process of lymphangiogenesis in an in vitro model. This finding may prove to be a natural compound for anti-lymphangiogenesis that could be developed for use in cancer therapy.