Induction of apoptosis by ursolic acid through activation of caspases and down-regulation of c-IAPs in human prostate epithelial cells

Application of Amino Acids in the Structural Modification of Natural Products: A Review

Natural products and their derivatives are important sources for drug discovery; however, they usually have poor solubility and low activity and require structural modification. Amino acids are highly soluble in water and have a wide range of activities. The introduction of amino acids into natural products is expected to improve the performance of these products and minimize their adverse effects. Therefore, this review summarizes the application of amino acids in the structural modification of natural products and provides a theoretical basis for the structural modification of natural products in the future. The articles were divided into six types based on the backbone structures of the natural products, and the related applications of amino acids in the structural modification of natural products were discussed in detail.

Activating Hippo Pathway via Rassf1 by Ursolic Acid Suppresses the Tumorigenesis of Gastric Cancer

The Hippo pathway is often dysregulated in many carcinomas, which results in various stages of tumor progression. Ursolic acid (UA), a natural compound that exists in many herbal plants, is known to obstruct cancer progression and exerts anti-carcinogenic effect on a number of human cancers. In this study, we aimed to examine the biological mechanisms of action of UA through the Hippo pathway in gastric cancer cells. MTT assay showed a decreased viability of gastric cancer cells after treatment with UA. Following treatment with UA, colony numbers and the sizes of gastric cancer cells were significantly diminished and apoptosis was observed in SNU484 and SNU638 cells. The invasion and migration rates of gastric cancer cells were suppressed by UA in a dose-dependent manner. To further determine the gene expression patterns that are related to the effects of UA, a microarray analysis was performed. Gene ontology analysis revealed that several genes, such as the Hippo pathway upstream target gene, ras association domain family (RASSF1), and its downstream target genes (MST1, MST2, and LATS1) were significantly upregulated by UA, while the expression of YAP1 gene, together with oncogenes (FOXM1, KRAS, and BATF), were significantly decreased. Similar to the gene expression profiling results, the protein levels of RASSF1, MST1, MST2, LATS1, and p-YAP were increased, whereas those of CTGF were decreased by UA in gastric cancer cells. The p-YAP expression induced in gastric cancer cells by UA was reversed with RASSF1 silencing. In addition, the protein levels in the Hippo pathway were increased in the UA-treated xenograft tumor tissues as compared with that in the control tumor tissues; thus, UA significantly inhibited the tumorigenesis of gastric cancer in vivo in xenograft animals. Collectively, UA diminishes the proliferation and metastasis of gastric cancer via the regulation of Hippo pathway through Rassf1, which suggests that UA can be used as a potential chemopreventive and therapeutic agent for gastric cancer.

Ursolic Acid Induces Apoptosis in Colorectal Cancer Cells Partially via Upregulation of MicroRNA-4500 and Inhibition of JAK2/STAT3 Phosphorylation

Though ursolic acid (UA) isolated from Oldenlandia diffusa was known to exhibit anti-cancer, anti-inflammatory, and anti-obesity effects, the underlying antitumor mechanism of ursolic acid was not fully understood to date. Thus, in the present study, the apoptotic mechanism of ursolic acid was elucidated in HCT116 and HT29 colorectal cancer cells in association with STAT3 and microRNA-4500 (miR-4500) by MTT assay, Terminal deoxynucleotidyl transferase-dT-mediated dUTP nick end labelling (TUNEL) assay, cell cycle analysis, immunofluorescence, and Western blotting. Ursolic acid significantly exerted cytotoxicity, increased TUNEL positive cells and sub-G1 apoptotic portion, induced cleavage of poly (adenosine diphosphate-ribose) polymerase (PARP) and caspase 3 in HCT116 and HT29 cells. Of note, ursolic acid attenuated the expression of anti-apoptotic proteins such as Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) and also blocked nuclear translocation of STAT3 in colorectal cancer cells. Notably, ursolic acid increased the expression level of miR-4500 in HCT116 cells by qRT-PCR analysis and conversely miR-4500 inhibitor reversed cytotoxic, anti-proliferative, and apoptotic effects by increasing TUNEL positive cells, PARP cleavage and inhibiting p-STAT3 in ursolic acid treated colorectal cancer cells. Overall, our findings provide evidence that usolic acid induces apoptosis in colorectal cancer cells partially via upregulation of miR-4500 and inhibition of STAT3 phosphorylation as a potent anti-cancer agent for colorectal cancer therapy.

Ursolic Acid--A Pentacyclic Triterpenoid with a Wide Spectrum of Pharmacological Activities

Ursolic acid (UA) is a natural terpene compound exhibiting many pharmaceutical properties. In this review the current state of knowledge about the health-promoting properties of this widespread, biologically active compound, as well as information about its occurrence and biosynthesis are presented. Particular attention has been paid to the application of ursolic acid as an anti-cancer agent; it is worth noticing that clinical tests suggesting the possibility of practical use of UA have already been conducted. Amongst other pharmacological properties of UA one can mention protective effect on lungs, kidneys, liver and brain, anti-inflammatory properties, anabolic effects on skeletal muscles and the ability to suppress bone density loss leading to osteoporosis. Ursolic acid also exhibits anti-microbial features against numerous strains of bacteria, HIV and HCV viruses and Plasmodium protozoa causing malaria.

Inhibitory effects of asiatic acid and CPT-11 on growth of HT-29 cells

Asiatic acid is a pentacyclic triterpene contained in medicinal plants. The cytotoxic effect of this compound and its augmentative effect on the anticancer drug irinotecan hydrochloride (CPT-11) were investigated in the human colon adenocarcinoma cell line HT-29. Asiatic acid dose-dependently showed cytotoxicity in HT-29 cells. DNA fragmentation, annexin-positive apoptotic cells, and caspase-3 activation were observed in a dose-dependent manner. A caspase-3 inhibitor suppressed the DNA ladder formation in a concentration-dependent manner. Bcl-2 and Bcl-XL proteins were decreased by asiatic acid treatment. These results indicate that asiatic acid induced apoptosis in HT-29 cells via caspase-3 activation. Cytotoxic effects of combined treatment with CPT-11 and asiatic acid on HT-29 cells were further examined. Simultaneous treatment or sequential exposure first to asiatic acid and then to CPT-11 showed an additive effect. Synergism was observed when cells were first exposed to CPT-11 and then to asiatic acid. These results suggest that asiatic acid can be used as an agent for increasing sensitivity of colon cancer cells to treatment with CPT-11 or as an agent for reducing adverse effects of CPT-11.