Jaridon 6, a new diterpene from Rabdosia rubescens (Hemsl.) Hara, can display anti-gastric cancer resistance by inhibiting SIRT1 and inducing autophagy.

Tumor resistance is the main cause of treatment failure and is associated with many tumor factors. Jaridon 6, a new diterpene extracted from Rabdosia rubescens (Hemsl.) Hara, which has been previously extracted by our research team, has been tested having more obvious advantages in resistant tumor cells. However, its mechanism is unclear. In this study, we studied the effect and the specific mechanism of Jaridon 6 in resistant gastric cancer cells. Cytotoxicity test, colony test, western blotting, and nude test verified the anti-drug resistance ability of Jaridon 6 in the MGC803/PTX and MGC803/5-Fu cells. Jaridon 6 has shown obvious inhibitory effects in the sirtuin 1 (SIRT1) enzyme test. Transmission electron microscopy and immunofluorescence tests further proved the autophagic action of Jaridon 6. Jaridon 6 could inhibit the proliferation of the resistant gastric cancer cell in vivo and in vitro. Jaridon 6 inhibited SIRT1 enzyme and induced autophagy by inhibiting the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway. Thus, it may be considered for treating gastric cancer resistance by individual or combined administration, as an SIRT1 inhibitor and autophagy inducer.

Generation and characterization of a paclitaxel-resistant human gastric carcinoma cell line.

The main aim of this study was to establish a novel paclitaxel (PTX)-resistant human gastric carcinoma cell line and to investigate its biological significance. A cell line, MGC803/PTX, was established by gradually increasing PTX density on the basis of MGC803 over a period of 10 months. In addition, a pair of resistant cell lines (SW620 and SW620/PTX) were added to further explain the resistant mechanism of PTX. The drug resistance index and stability of MGC803/PTX cells were detected using the Cell Counting Kit-8 method. The morphological features were observed using inverted microscopy. Apoptosis was measured by flow cytometry (FCM) and Hoechst 33258 fluorescence staining. The distribution of the cell cycle was determined by FCM, and protein expressions of P-gp, Bcl-2, Bax, and PARP were detected by western blot analysis. When characterizing the resistance in vitro, we found that MGC803/PTX cells were 10.3-fold more resistant to PTX compared with MGC803 cells. In addition, MGC803/PTX cells showed cross-resistance to 5-fluorouracil and adriamycin. FCM and Hoechst 33258 fluorescence staining indicated that MGC803/PTX cells had a significantly lower percentage of apoptotic cells after treatment with PTX compared with MGC803 cells. Other differences between parental cells and resistant cells included morphology, proliferation rate, doubling time, cell cycle distribution, and colony-formation rate. Western blot analysis indicated that P-gp, Bcl-2, and PARP protein were more abundant in MGC803/PTX and SW620/PTX cells compared with MGC803 and SW620 cells, whereas Bax protein levels were lower in resistant cells. Furthermore, MGC803/PTX cells showed obvious resistance to PTX in vivo. To our knowledge, this is the first report on the establishment of a PTX-resistant MGC803 cell line, which is an important tool to explore the resistance of anticancer drugs and to overcome tumor drug resistance.

Gene expression profiling and pathway network analysis of anti-tumor activity by Jaridon 6 in esophageal cancer.

Jaridon 6, a novel ent-kaurene diterpenoid derived from Rabdosia rubescens (Hemsl.) Hara, possesses strong anti-tumor activity in esophageal cancer cells. In this study, we explored the underlying molecular events of the anti-tumor activity of Jaridon 6. Cell viability and apoptosis results obtained by flow cytometry confirmed the tumor inhibitory effect of Jaridon 6 in esophageal cancer cells. A cDNA microarray was performed and the observations were validated using quantitative reverse transcription polymerase chain reaction. The microarray data showed that 151 genes were differentially expressed between the untreated group and the Jaridon 6-treated group, among these were 57 upregulated genes, and 94 downregulated genes (P < 0.01, fold change threshold: 2). These included genes such as Wnt, peroxisome, and genes involved in chemokine signaling pathways. In addition, Western blot analysis demonstrated that Jaridon 6 regulated the expression of Wnt pathway proteins, including reduced levels of Dvl 2, survivin and cyclin D1, and increased levels of p-ß-catenin, and AXIN2 in EC109 and EC9706 esophageal cancer cells. In addition, recombinant murine Wnt3a could change the regulation of Jaridon 6 on Wnt pathway proteins. Immunohistochemical analysis indicated that the anti-tumor activity of Jaridon 6 was closely related to the Wnt signaling pathway in esophageal cancer cells.

Structure-Activity Relationship Studies of ß-Lactam-azide Analogues as Orally Active Antitumor Agents Targeting the Tubulin Colchicine Site.

We have synthesized a series of new ß-lactam-azide derivatives as orally active anti-tumor agents by targeting tubulin colchicine binding site and examined their structure activity relationship (SAR). Among them, compound 28 exhibited the most potent antiproliferative activity against MGC-803 cells with an IC50 value of 0.106 µM by induction of G2/M arrest and apoptosis and inhibition of the epithelial to mesenchymal transition. 28 acted as a novel inhibitor of tubulin polymerization by its binding to the colchicine site. SAR analysis revealed that a hydrogen atom at the C-3 position of the ß-lactam was required for the potent antiproliferative activity of ß-lactam-azide derivatives. Oral administration of compound 28 also effectively inhibited MGC-803 xenograft tumor growth in vivo in nude mice without causing significant loss of body weight. These results suggested that compound 28 is a promising orally active anticancer agent with potential for development of further clinical applications.