Retracted : Nimotuzuma restrains proliferation and induces apoptosis in human osteosarcoma cells by regulation of EGFR/PI3K/AKT signal pathway

Cadmium induces apoptosis and autophagy in swine small intestine by downregulating the PI3K/Akt pathway

Cadmium (Cd) is an environmental contaminant, which is potentially toxic. It is well known that Cd can accumulate in the liver and kidney and cause serious damage. However, few studies have investigated the mechanism of intestinal damage induced by Cd in swine. Here, we established Cd poisoning models in vivo and in vitro to explore the mechanism of intestinal injury induced by Cd in swine. The morphology of intestinal tissue cells was observed by TUNEL staining and electron microscopy, and the morphology of IPEC-J2 cells was observed by flow cytometry, Hoechst staining, and MDC staining. Cell morphological observations revealed that Cd treatment induced ileal apoptosis and autophagy. The effects of Cd on the PI3K/Akt pathway, as well as on apoptosis and autophagy-related protein expression in intestinal cells, were analyzed by western blot (WB) and the expression of mRNA was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The results showed that Cd induced autophagy by increasing the levels of autophagy markers Beclin1, Autophagy-associated gene 5 (ATG5), Autophagy-associated gene 16 (ATG16), and Microtubule-associated protein light chains 3-2 (LC3-II), and by reducing the expression levels of Mechanistic target of rapamycin kinase (mTOR) and Microtubule-associated protein light chains 3-1 (LC3-I). Cell apoptosis was induced by increasing the expression of apoptosis markers Bcl-2 associated X protein (Bax), Cysteinyl aspartate specific proteinase 9 (Caspase9), cleaved Caspase9, Cysteinyl aspartate specific proteinase 3 (Caspase3), and cleaved Caspase3, and by reducing the expression of B cell lymphoma/leukemia 2 (Bcl-2). At the same time, Cd decreased the expression of phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt), and their phosphorylation. We treated IPEC-J2 cells with the PI3K activator 740Y-P and analyzed the morphological changes as well as autophagy and apoptosis-related gene expression. The results showed that 740Y-P could reduce apoptosis and autophagy induced by Cd. In conclusion, our findings suggest that Cd induces intestinal apoptosis and autophagy in swine by inactivating the PI3K/Akt signaling pathway.

Stattic sensitizes osteosarcoma cells to epidermal growth factor receptor inhibitors via blocking the interleukin 6-induced STAT3 pathway

Osteosarcoma (OS), the most common malignant bone tumor with high metastatic potential, frequently affects children and adolescents. Epidermal growth factor receptor (EGFR)-targeted tyrosine kinase inhibitors exhibit encouraging anti-tumor activity for patients with solid tumors, whereas their effects on OS remain controversial. In the present study, we aimed to elucidate the anti-tumor activity of gefitinib for OS, as well as to explore the underlying mechanisms. Gefitinib inhibits cell viability, tumor growth, cell migration, and invasion and promotes cell apoptosis and G1 cycle arrest in OS at a relatively high concentration via suppressing the PI3K/Akt and ERK pathways. However, gefitinib treatment results in the feedback activation of signal transducer and activator of transcription 3 (STAT3) induced by interleukin 6 (IL-6) secretion. Combined treatment with gefitinib and stattic, an inhibitor for STAT3 phosphorylation, engenders more evident inhibitory effects on cell proliferation, migration, and invasion and promotive effects on cell apoptosis and G1 phase arrest in OS, compared with the single exposure to gefitinib or stattic. Western blot analysis demonstrates that stattic treatment in gefitinib-treated OS abrogates the IL-6-induced STAT3 activation and subsequently further restrains the activities of EGFR, Akt, and ERK pathways in tumor cells. This study confirms that the EGFR inhibitor of gefitinib has moderate anti-tumor effects on OS through IL-6 secretion-mediated STAT3 activation. Additional administration of stattic in EGFR-targeted therapies may contribute to improve the efficacy for OS.

Epidermal growth factor receptor promotes tumor progression and contributes to gemcitabine resistance in osteosarcoma

Osteosarcoma (OS) is the most common type of primary malignant tumors that originate in the bone. Resistance to chemotherapy confers a poor prognosis on OS patients. Dysregulation of the epidermal growth factor receptor (EGFR) signaling has been reported in sarcomas. However, the functional contribution of EGFR hyperactivation to the tumor biology and chemoresistance remains largely unexplored in OS. In this study, we aimed to investigate the role of EGFR in OS progression and in the response of OS to gemcitabine treatment. The EGFR expression was found to be upregulated in fibroblastic OS cell lines. EGFR knockdown suppressed OS cell proliferation, migration, and invasion in vitro and tumor formation in vivo. Conversely, EGFR overexpression promoted the growth and motility of OS cells. In terms of mechanism, the levels of phospho-Akt and phospho-ERK were decreased upon EGFR knockdown but increased as a result of EGFR overexpression, implying a possible involvement of PI3K/Akt and ERK pathways in mediating the effects of EGFR on OS cells. Moreover, the level of phospho-EGFR was increased in OS cells when exposed to gemcitabine treatment. A more profound proliferative inhibition and a higher rate of apoptosis were obtained in OS cells via inducing cell cycle arrest at G1 phase upon gemcitabine treatment combined with EGFR knockdown, as compared to gemcitabine alone. On the contrary, EGFR overexpression counteracted the growth-inhibiting and pro-apoptotic effects of gemcitabine in OS cells. The present study suggests that EGFR promotes tumor progression and contributes to gemcitabine resistance in OS.

Proanthocyanidin B2 inhibits proliferation and induces apoptosis of osteosarcoma cells by suppressing the PI3K/AKT pathway

Osteosarcoma (OS) is the most common primary malignant bone tumour in children and adolescents. The long‐term survival rate of OS patients is stubbornly low mainly due to the chemotherapy resistance. We therefore aimed to investigate the antitumoral effects and underlying mechanisms of proanthocyanidin B2 (PB2) on OS cells in the current study. The effect of PB2 on the proliferation and apoptosis of OS cell lines was assessed by CCK‐8, colony formation, and flow cytometry assays. The target gene and protein expression levels were measured by qRT‐PCR and Western blotting. A xenograft mouse model was established to assess the effects of PB2 on OS proliferation and apoptosis in vivo. Results from in vitro experiments showed that PB2 inhibited the proliferation and induced apoptosis of OS cells, and also increased the expression levels of apoptosis‐related proteins. Moreover, PB2 induced OS cell apoptosis through suppressing the PI3K/AKT signalling pathway. The in vivo experiments further confirmed that PB2 could inhibit OS tumour growth and induce its apoptosis. Taken together, these results suggested that PB2 inhibited the proliferation and induced apoptosis of OS cells through the suppression of the PI3K/AKT signalling pathway.

28-Hydroxy-3-oxoolean-12-en-29-oic Acid, a Triterpene Acid from Celastrus Orbiculatus Extract, Inhibits the Migration and Invasion of Human Gastric Cancer Cells In Vitro

Gastric cancer is the fifth most common tumor and has the third-highest mortality rate among various malignant tumors, and the survival rate of patients is low. Celastrus orbiculatus extract has been shown to inhibit the activity of a variety of tumors. This study explored the inhibitory effect of the oleanane-type triterpenoid acid 28-hydroxy-3-oxoolean-12-en-29-oic acid molecule from Celastrus orbiculatus extract on gastric cancer cell invasion and metastasis and determined its mechanism. 28-Hydroxy-3-oxoolean-12-en-29-oic acid was first diluted to various concentrations and then used to treat SGC-7901 and BGC-823 cells. Cell proliferation was assessed by an MTT (thiazole blue) assay. Transwell and wound healing assays were used to assess cell invasion and migration. High-content imaging technology was used to further observe the effects of the drug on cell invasion and migration. Western blotting was used to assess the effects on the expression of matrix metalloproteinases (MMPs) and the effects on epithelial-mesenchymal transition (EMT)-related proteins and phosphorylation-related proteins. We found that 28-Hydroxy-3-oxoolean-12-en-29-oic acid inhibited the migration and invasion of SGC-7901 and BGC-823 gastric cancer cells in a dose-dependent manner. Consequently, 28-hydroxy-3-oxoolean-12-en-29-oic acid decreased the expression of EMT-related proteins and MMPs in gastric cancer cells and reduced protein phosphorylation, inhibiting the migration and invasion of gastric cancer cells.