Effect of pseudolaric acid B on gastric cancer cells: Inhibition of proliferation and induction of apoptosis

In vitro antimetastatic potential of pseudolaric acid B in HSC-3 human tongue squamous carcinoma cell line

OBJECTIVE

Pseudolaric acid B (PAB) is a novel diterpenoid derived from the traditional Chinese medicinal herb Cortex pseudolaricis that exerts anticancer, anti-inflammatory, and immunomodulatory properties. While the anticancer potential of PAB has been studied, its effects on metastasis have not been well-studied. This study aims to determine the inhibitory effects of PAB on HSC-3 human tongue squamous cell carcinoma (TSCC) cell line.

DESIGN

Cell viability and soft agar colony formation assays were conducted to assess cellular proliferation and in vitro tumorigenic capacity of TSCC cells, respectively. Additionally, wound healing, transwell migration, and invasion assays were conducted to monitor the aggressive behavior of TSCC cells. Furthermore, Western blotting analysis was conducted to reveal the signaling pathways involved in the modulation of epithelial-mesenchymal transition (EMT).

RESULTS

The migratory and invasive capacities of HSC-3 cells were suppressed by PAB irrespective of their proliferation states. PAB's effects on EMT involved upregulation of E-cadherin expression and downregulation of Twist; these were concomitantly accompanied by downregulated phosphorylation of epidermal growth factor receptor (EGFR).

CONCLUSIONS

PAB suppresses human TSCC in vitro by regulating Twist/E-cadherin through the EGFR signaling pathway. PAB may have potential as a candidate antimetastatic drug for TSCC treatment.

Pseudolaric acid B induces endometrial cancer Ishikawa cell apoptosis and inhibits metastasis through AKT-GSK-3β and ERK1/2 signaling pathways

Pseudolaric acid B (PAB) is the most active constituent extracted from the bark of Pseudolarix kaempferi, which has been used as an antifungal remedy in traditional Chinese medicine. It is reported to have cytotoxicity to many tumor cell lines. In this study, we investigated the effects of PAB against human endometrial cancer Ishikawa cells. We found that PAB inhibited Ishikawa cell proliferation, and induced cell apoptosis and G2/M phase arrest through a mechanism involving AKT-GSK-3β and ERK1/2 signaling pathways. PAB also suppressed the Ishikawa cell adhesion, invasion, migration, and colony formation ability by increasing the expression of E-cadherin, Ezrin, and Kiss-1, and decreasing the expression of matrix metalloproteinase-9 and vascular endothelial growth factor. Taken together, these data indicated that PAB can be expected to be a novel treatment agent for endometrial cancer therapy.

Pseudolaric acid B inhibits gastric cancer cell metastasis in vitro and in haematogenous dissemination model through PI3K/AKT, ERK1/2 and mitochondria-mediated apoptosis pathways

Pseudolaric acid B (PAB) is the major bioactive constituent in the root bark of Pseudolarix kaempferi and has been reported to have cytotoxicity against tumor cells. Our in vivo experiments showed that PAB could inhibit gastric cancer cell lung metastasis in a nude mouse haematogenous dissemination model. To evaluate the anti-metastasis mechanism of PAB in gastric cancer cells, cytological experiments were performed. The results showed that PAB could inhibit the adhesion ability to matrigel, migration, invasion and colony formation ability of BGC-823 and MKN-45 cells. Western blot further confirmed that the inhibitory effects of PAB on anti-metastasis may involve regulating the expression of the metastasis-related proteins MMP-9, HIF-1α, VEGF, VEGFR2, E-Cadherin and Ezrin. We obtained further proof that PAB which could be used as a multi-targeted agent to inhibit the PI3K/AKT, ERK1/2 and mitochondria-mediated apoptosis pathways and consequently suppress tumor growth and metastasis. Our experiments suggest that PAB-induced effects may have novel therapeutic applications for the treatment of gastric cancer.

Pseudolaric acid B circumvents multidrug resistance phenotype in human gastric cancer SGC7901/ADR cells by downregulating Cox-2 and P-gp expression

Multidrug resistance (MDR) is a challenging issue in the treatment of gastric cancer. Pseudolaric acid B is a new diterpene acid compound isolated from pseudolarix, which has been found to have anti-tumor activities in recent studies. The purpose of the present study was to evaluate the effects of pseudolaric acid B in an MDR gastric cancer cell line and elucidate the possible underlying mechanisms of action. SGC7901/ADR, a P-glycoprotein (P-gp)-overexpressing cell line, was used to evaluate the efficacy of pseudolaric acid B against MDR phenotypes. The effects of pseudolaric acid B and chemotherapeutic agents on cell proliferation and apoptosis were assessed using the MTT assay and flow cytometry, respectively. Immunocytochemistry and Western blot were used to detect the possible relevant molecules in order to elucidate the underlying mechanism of action. The results showed that pseudolaric acid B inhibited cell proliferation and induced apoptosis in SGC7901/ADR cells. A low dose of pseudolaric acid B (0.5 µmol/L) augmented the inhibitory effects of chemotherapeutic agents on proliferation (p < 0.05). The expression of P-gp and cyclooxygenase 2 (Cox-2) was downregulated with pseudolaric acid B treatment. The present results showed that pseudolaric acid B inhibited cell proliferation, induced apoptosis, circumvented MDR, and increased the sensitivity of chemotherapeutic agents in vitro by downregulating the expression of P-gp and Cox-2.

Chinese medicines induce cell death: the molecular and cellular mechanisms for cancer therapy

Chinese medicines have long history in treating cancer. With the growing scientific evidence of biomedical researches and clinical trials in cancer therapy, they are increasingly accepted as a complementary and alternative treatment. One of the mechanisms is to induce cancer cell death. Aim. To comprehensively review the publications concerning cancer cell death induced by Chinese medicines in recent years and provide insights on anticancer drug discovery from Chinese medicines. Materials and Methods. Chinese medicines (including Chinese medicinal herbs, animal parts, and minerals) were used in the study. The key words including “cancer”, “cell death”, “apoptosis”, “autophagy,” “necrosis,” and “Chinese medicine” were used in retrieval of related information from PubMed and other databases. Results. The cell death induced by Chinese medicines is described as apoptotic, autophagic, or necrotic cell death and other types with an emphasis on their mechanisms of anticancer action. The relationship among different types of cell death induced by Chinese medicines is critically reviewed and discussed. Conclusions. This review summarizes that CMs treatment could induce multiple pathways leading to cancer cell death, in which apoptosis is the dominant type. To apply these preclinical researches to clinic application will be a key issue in the future.

The inhibitory effect of pseudolaric acid B on gastric cancer and multidrug resistance via Cox-2/PKC-α/P-gp pathway

Aim

To investigate the inhibitory effect of pseudolaric acid B on subcutaneous xenografts of human gastric adenocarcinoma and the underlying molecular mechanisms involved in its multidrug resistance.

Methods

Human gastric adenocarcinoma SGC7901 cells and drug-resistant SGC7901/ADR cells were injected into nude mice to establish a subcutaneous xenograft model. The effects of pseudolaric acid B with or without adriamycin treatment were compared by determining the tumor size and weight. Cyclo-oxygenase-2, protein kinaseC-α and P-glycoprotein expression levels were determined by immunohistochemistry and western blot.

Results

Pseudolaric acid B significantly suppressed the tumor growth induced by SGC7901 cells and SGC7901/ADR cells. The combination of pseudolaric acid B and the traditional chemotherapy drug adriamycin exhibited more potent inhibitory effects on the growth of gastric cancer in vivo than treatment with either pseudolaric acid B or adriamycin alone. Protein expression levels of cyclo-oxygenase-2, protein kinaseC-α and P-glycoprotein were inhibited by pseudolaric acid B alone or in combination with adriamycin in SGC7901/ADR cell xenografts.

Conclusion

Pseudolaric acid B has a significant inhibitory effect and an additive inhibitory effect in combination with adriamycin on the growth of gastric cancer in vivo, which reverses the multidrug resistance of gastric neoplasm to chemotherapy drugs by downregulating the Cox-2/PKC-α/P-gp/mdr1 signaling pathway.

Pseudolaric Acid B induces caspase-dependent and caspase-independent apoptosis in u87 glioblastoma cells

Pseudolaric acid B (PLAB) is one of the major bioactive components of Pseudolarix kaempferi. It has been reported to exhibit inhibitory effect on cell proliferation in several types of cancer cells. However, there is no report elucidating its effect on glioma cells and organ toxicity in vivo. In the present study, we found that PLAB inhibited growth of U87 glioblastoma cells in a dose-dependent manner with IC₅₀~10 μM. Flow cytometry analysis showed that apoptotic cell death mediated by PLAB was accompanied with cell cycle arrest at G2/M phase. Using Western blot, we found that PLAB induced G2/M phase arrest by inhibiting tubulin polymerization in U87 cells. Apoptotic cell death was only partially inhibited by pancaspase inhibitor, z-VAD-fmk, which suggested that PLAB-induced apoptosis in U87 cells is partially caspase-independent. Further mechanistic study demonstrated that PLAB induced caspase-dependent apoptosis via upregulation of p53, increased level of proapoptotic protein Bax, decreased level of antiapoptotic protein Bcl-2, release of cytochrome c from mitochondria, activation of caspase-3 and proteolytic cleavage of poly (ADP-ribose) polymerase (PARP) and caspase-independent apoptosis through apoptosis inducing factor (AIF). Furthermore, in vivo toxicity study demonstrated that PLAB did not induce significant structural and biochemical changes in mouse liver and kidneys at a dose of 25 mg/kg. Therefore, PLAB may become a potential lead compound for future development of antiglioma therapy.

Rapid separation and identification of major constituents in Pseudolarix kaempferi by ultra-performance liquid chromatography coupled with electrospray and quadrupole time-of-flight tandem mass spectrometry

A rapid and reliable method based on ultra-performance liquid chromatography (UPLC) coupled with photodiode-array detection (PDA) and electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-Q-TOF-MS/MS) has been developed for separation and identification of major constituents in extracts of root bark of Pseudolarix kaempferi Gordon (PKG). Identification of the constituents was carried out by interpretation of their retention times, UV absorption spectra, MS and MS/MS spectra, as well as the data provided by authentic standards and literatures. A total of 20 components were separated in only 8.0 min on a small particle size C18 column (1.7 microm). These components included nine diterpene acids, seven glycosides and four triterpenoids, among which pseudolaric acid C-O-beta-D-glucopyranoside and pseudolaric acid C2-O-beta-D-glucopyranoside were separated and identified for the first time in this study. Furthermore, the fragmentation patterns of the three types of compounds were elucidated for the first time. This established UPLC-PDA/Q-TOF-MS/MS method is reliable and effective for the separation and identification of the 20 compounds and will be useful for quality control of the crude materials of Pseudolarix kaempferi Gordon and their related preparations.

Induction of G2/M arrest by pseudolaric acid B is mediated by activation of the ATM signaling pathway

AIM

The aim of this study was to investigate the mechanism of pseudolaric acid B (PLAB)-induced cell cycle arrest in human melanoma SK-28 cells.

METHODS

Cell growth inhibition was detected by MTT assay, the cell cycle was analyzed by flow cytometry, and protein expression was examined by Western blot analysis.

RESULTS

PLAB inhibited the growth of human melanoma cells and induced G(2)/M arrest in SK-28 cells, accompanied by an up-regulation of Cdc2 phosphorylation and a subsequent down-regulation of Cdc2 expression. Furthermore, PLAB decreased the expression of Cdc25C phosphatase and increased the expression of Wee1 kinase. Meanwhile, a reduction in Cdc2 activity was partly due to induction of the expression of p21(waf1/cip1) in a p53-dependent manner. In addition, PLAB activated the checkpoint kinase, Chk2, and increased the expression of p53, two major targets of ATM kinase. These effects were inhibited by caffeine, an ATM kinase inhibitor. We also found that PLAB significantly enhanced ATM kinase activity.

CONCLUSION

Taken together, these results suggest that PLAB induced G(2)/M arrest in human melanoma cells via a mechanism involving the activation of ATM, and the effect of PLAB on Cdc2 activity was mediated via interactions with the Chk2-Cdc25C and p53 signalling pathways, two distinct downstream pathways of ATM. PLAB may be a promising chemopreventive agent for treating human melanoma.

Pseudolaric acid B-induced apoptosis through p53-dependent pathway in human gastric carcinoma cells

Pseudolaric acid B (PLAB, 1), a natural diterpenoid compound, was isolated from Pseudolarix kaempferi Gordon. It has shown antifungal, antifertility, and antiangiogenic properties in previous studies. Recently, increasing evidence has confirmed that 1 exhibits antitumor effects in several tumor cell lines, but the underlying mechanism has not been fully elucidated. The aim of this study was to investigate the mechanism of PLAB-induced cell apoptosis in MGC803 cells. The results showed that 1 significantly inhibited the proliferation of MGC803 cells at 0.01-10 microM and the IC(50) value was 0.91 microM for 48 h. PLAB-induced apoptosis in MGC803 cells was confirmed by DNA fragmentation assay and Hoechst33342/PI staining. PLAB-treated MGC803 cells were arrested at G(2) phase, which was associated with a marked increment of the expression of cyclin-dependent kinase inhibitor p21. The induction of p21 appeared to be transcriptionally up-regulated and was p53-dependent. In addition, PLAB induced Fas/APO-1 and caspase-3 expressions that were also correlated with apoptosis. Meanwhile, 1 decreased the mRNA expression of bcl-2, which is an antiapoptosis factor. In conclusion, 1 induced apoptosis through p53-dependent pathway in human gastric carcinoma cells. These findings suggest that 1 may be a novel promising agent for treating human gastric carcinoma.