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 (UA) possesses various pharmacological activities, such as antitumorigenic and anti-inflammatory effects. In the present study, we investigated the mechanisms underlying the effects of UA against esophageal squamous cell carcinoma (ESCC) (TE-8 cells and TE-12 cells). The cell viability assay showed that UA decreased the viability of ESCC in a dose-dependent manner. In the soft agar colony formation assay, the colony numbers and size were reduced in a dose-dependent manner after UA treatment. UA caused the accumulation of vacuoles and LC3 puncta, a marker of autophagosome, in a dose-dependent manner. Autophagy induction was confirmed by measuring the expression levels of LC3 and p62 protein in ESCC cells. UA increased LC3-II protein levels and decreased p62 levels in ESCC cells. When autophagy was hampered using 3-methyladenine (3-MA), the effect of UA on cell viability was reversed. UA also significantly inhibited protein kinase B (Akt) activation and increased p-Akt expression in a dose-dependent manner in ESCC cells. Accumulated LC3 puncta by UA was reversed after wortmannin treatment. LC3-II protein levels were also decreased after treatment with Akt inhibitor and wortmannin. Moreover, UA treatment increased cellular reactive oxygen species (ROS) levels in ESCC in a time- and dose-dependent manner. Diphenyleneiodonium (an ROS production inhibitor) blocked the ROS and UA induced accumulation of LC3-II levels in ESCC cells, suggesting that UA-induced cell death and autophagy are mediated by ROS. Therefore, our data indicate that UA inhibits the growth of ESCC cells by inducing ROS-dependent autophagy.
Ursolic acid (UA), a pentacyclic triterpenoid extracted from various plants, inhibits cell growth, metastasis, and tumorigenesis in various cancers. Chemotherapy resistance and the side effects of paclitaxel (PTX), a traditional chemotherapy reagent, have limited the curative effect of PTX in esophageal cancer. In this study, we investigate whether UA promotes the anti-tumor effect of PTX and explore the underlying mechanism of their combined effect in esophageal squamous cell carcinoma (ESCC). Combination treatment with UA and PTX inhibited cell proliferation and cell growth more effectively than either treatment alone by inducing more significant apoptosis, as indicated by increased sub-G1 phase distribution and protein levels of cleaved-PARP and cleaved caspase-9. Similar to the cell growth suppressive effect, the combination of UA and PTX significantly inhibited cell migration by targeting uPA, MMP-9, and E-cadherin in ESCC cells. In addition, combination treatment with UA and PTX significantly activated p-GSK-3β and suppressed the activation of Akt and FOXM1 in ESCC cells. Those effects were enhanced by the Akt inhibitor LY2940002 and inverted by the Akt agonist SC79. In an in vivo evaluation of a murine xenograft model of esophageal cancer, combination treatment with UA and PTX suppressed tumor growth significantly better than UA or PTX treatment alone. Thus, UA effectively potentiates the anti-tumor efficacy of PTX by targeting the Akt/FOXM1 cascade since combination treatment shows significantly more anti-tumor potential than PTX alone both in vitro and in vivo. Combination treatment with UA and PTX could be a new strategy for curing esophageal cancer patients.
colorectal cancer (crc) is one of the deadliest malignant tumors worldwide and its prevalence is increasing in South Korea. The efficacy of combined treatment with natural product-derived and chemotherapy agents including curcumin combined with 5-fluorouracil, resveratrol combined with cisplatin and epigallocatechin-3-gallate (EGCG) combined with cisplatin in preventing cancer progression and killing cancer cells has emerged. The akt and Hippo signaling pathways serve a key role in colorectal tumor growth; however, the exact role of the crosstalk between Akt and Hippo signaling pathways in CRC remains poorly elucidated. The combined effect of ua and doX on the cell proliferation, apoptosis, migration and cell cycle of CRC cells were investigated by performing Cell proliferation assay, a soft agar colony formation assay, flow cytometry, wound healing assay and western blotting assay. Subsequently, the expression of AKT and Hippo signaling pathway-associated proteins were also assessed by western blot assay. Moreover, a xenograft nude mouse model was constructed to verify the effects of UA and doX on the tumorigenesis of HcT116 cell in vivo. The present study reported that ursolic acid (UA) strongly enhanced the antitumor action of doxorubicin (DOX) via blocking the akt/glycogen synthase kinase-3β (Gsk3β) signaling pathway and activating tumor-suppressive Hippo signaling (mammalian Ste20-like kinase 1 and 2, salvador family WW domain containing protein 1 and MOB kinase activator 1), thereby downregulating downstream effector yes-associated protein 1 (Yap) and connective tissue growth factor (cTGF) protein expression levels in CRC cells. Furthermore, The PI3K inhibitor LY294002 further suppressed Akt activity and enhance the function of Hippo pathway-associated proteins in DOX + UA treated cells; this effect led to subsequent oncogenic Yap and CTGF inhibition following combined treatment, whereas akt activator Sc79 exerted an opposite effect in cTGF expression. In vivo, treatment with UA combined with DOX markedly suppressed the progression of CRC without any toxic effects on a xenograft mouse model by disrupting Akt signaling and activating the Hippo signaling pathway. These results demonstrated that UA and DOX treatment successfully induced akt/Gsk3β inactivation via Hippo signaling pathway activation to promote Yap degradation, resulting in the inhibition of colorectal tumorigenesis. In conclusion, these findings suggested that combination therapy with UA and DOX may be more effective than DOX alone. UA may be a novel anticancer strategy and could be considered for investigation as a complementary chemotherapy agent in the future.
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