OBJECTIVE: To study the effects of the overexpression of autophagy-related gene 3 (ATG3) on autophagy and salinomycin-induced apoptosis in breast cancer cells and explore the underlying mechanisms. METHODS: We used the lentivirus approach to establish a breast cancer cell line with stable overexpression of ATG3. Western blotting, immunofluorescence staining and transmission electron microscopy were used to analyze the effect of ATG3 overexpression on autophagy in breast cancer MCF-7 cells. Using the AKT/mTOR agonists SC79 and MHY1485, we analyzed the effect of AKT/mTOR signal pathway activation on ATG3 overexpression-induced autophagy. Western blotting and flow cytometry were used to analyze the effect of autophagy on apoptosis of the ATG3-overexpressing cells treated with salinomycin and 3-MA (an autophagy inhibitor). RESULTS: In ATG3-overexpressing MCF-7 cells, ATG3 overexpression obviously promoted autophagy, inhibited the AKT/mTOR signaling pathway, significantly weakened salinomycin-induced apoptosis ( < 0.01), caused significant reduction of the levels of the pro-apoptotic proteins cleaved-caspase 3 ( < 0.01) and Bax ( < 0.05), and enhanced the expression of the anti-apoptotic protein Bcl-2 ( < 0.05). The inhibition of autophagy obviously weakened the inhibitory effect of ATG3 overexpression on salinomycin-induced apoptosis. CONCLUSIONS ATG3 overexpression promotes autophagy possibly by inhibiting the AKT/mTOR signaling pathway to decrease salinomycin-induced apoptosis in MCF-7 cells, suggesting that autophagy induction might be one of the mechanisms of drug resistance in breast cancer cells.
Acetates ; pharmacology ; Apoptosis ; drug effects ; genetics ; Autophagy ; drug effects ; Autophagy-Related Proteins ; metabolism ; Benzopyrans ; pharmacology ; Breast Neoplasms ; metabolism ; pathology ; Cell Line, Tumor ; Cell Proliferation ; Drug Resistance, Neoplasm ; Female ; Gene Expression Regulation ; Humans ; MCF-7 Cells ; Morpholines ; pharmacology ; Proto-Oncogene Proteins c-akt ; antagonists & inhibitors ; metabolism ; Pyrans ; pharmacology ; TOR Serine-Threonine Kinases ; antagonists & inhibitors ; metabolism ; Triazines ; pharmacology ; Ubiquitin-Conjugating Enzymes ; metabolism

Cancer stem cells (CSCs) have tumor initiation, self-renewal, metastasis and chemo-resistance properties in various tumors including colorectal cancer. Targeting of CSCs may be essential to prevent relapse of tumors after chemotherapy. Phosphatidylinositol-3-kinase (PI3K) and mammalian target of rapamycin (mTOR) signals are central regulators of cell growth, proliferation, differentiation, and apoptosis. These pathways are related to colorectal tumorigenesis. This study focused on PI3K and mTOR pathways by inhibition which initiate differentiation of SW620 derived CSCs and investigated its effect on tumor progression. By using rapamycin, LY294002, and NVP-BEZ235, respectively, PI3K and mTOR signals were blocked independently or dually in colorectal CSCs. Colorectal CSCs gained their differentiation property and lost their stemness properties most significantly in dual-blocked CSCs. After treated with anti-cancer drug (paclitaxel) on the differentiated CSCs cell viability, self-renewal ability and differentiation status were analyzed. As a result dual-blocking group has most enhanced sensitivity for anti-cancer drug. Xenograft tumorigenesis assay by using immunodeficiency mice also shows that dual-inhibited group more effectively increased drug sensitivity and suppressed tumor growth compared to single-inhibited groups. Therefore it could have potent anti-cancer effects that dual-blocking of PI3K and mTOR induces differentiation and improves chemotherapeutic effects on SW620 human colorectal CSCs.
AC133 Antigen/genetics/metabolism ; Animals ; Antineoplastic Agents/pharmacology/therapeutic use ; Cell Differentiation/*drug effects ; Cell Line, Tumor ; Cell Survival/drug effects ; Chromones/pharmacology/therapeutic use ; Colorectal Neoplasms/drug therapy/metabolism/pathology ; Humans ; Imidazoles/pharmacology/therapeutic use ; Male ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Morpholines/pharmacology/therapeutic use ; Neoplastic Stem Cells/cytology/drug effects/metabolism ; Paclitaxel/pharmacology/therapeutic use ; Phosphatidylinositol 3-Kinases/*antagonists & inhibitors/metabolism ; Quinolines/pharmacology/therapeutic use ; SOXB1 Transcription Factors/genetics/metabolism ; Signal Transduction/*drug effects ; Sirolimus/pharmacology/therapeutic use ; TOR Serine-Threonine Kinases/*antagonists & inhibitors/metabolism ; Xenograft Model Antitumor Assays

The phosphatidylinositol 3 kinase (PI3K) pathway is frequently altered in cancer, including ovarian cancer (OC). Unfortunately, despite a sound biological rationale and encouraging activity in preclinical models, trials of first-generation inhibitors of mammalian target of rapamycin (mTOR) in OC have demonstrated negative results. The lack of patient selection as well as resistance to selective mTOR complex-1 (mTORC1) inhibitors could explain the disappointing results thus far. Nonetheless, a number of novel agents are being investigated, including dual mTORC1/mTORC2, Akt, and PI3K inhibitors. Although it is likely that inhibition of the PI3K/Akt/mTOR pathway may have little effect in unselected OC patients, certain histological types, such as clear cell or endometrioid OC with frequent phosphatidylinositol-4,5-biphosphate 3-kinase, catalytic subunit alpha (PIK3CA) and/or phosphatase and tensin homolog (PTEN) alterations, may be particularly suited to this approach. Given the complexity and redundancy of the PI3K signaling network, PI3K pathway inhibition may be most useful in combination with either chemotherapy or other targeted therapies, such as MEK inhibitors, anti-angiogenic therapy, and hormonal therapy, in appropriately selected OC patients. Here, we discuss the relevance of the PI3K pathway in OC and provide an up-to-date review of clinical trials of novel PI3K inhibitors alone or in combination with cytotoxics and novel therapies in OC. In addition, the challenges of drug resistance and predictive biomarkers are addressed.
Antineoplastic Combined Chemotherapy Protocols ; therapeutic use ; Drug Resistance, Neoplasm ; Female ; Humans ; Ovarian Neoplasms ; drug therapy ; Phosphatidylinositol 3-Kinases ; antagonists & inhibitors ; physiology ; Proto-Oncogene Proteins c-akt ; antagonists & inhibitors ; physiology ; Signal Transduction ; drug effects ; TOR Serine-Threonine Kinases ; antagonists & inhibitors ; physiology

p70 ribosomal protein S6 kinase (p70S6K), an important member of AGC family, is a kind of multifunctional Ser/Thr kinases, which plays an important role in mTOR signaling cascade. The p70 ribosomal protein S6 kinase is closely associated with diverse cellular processes such as protein synthesis, mRNA processing, glucose homeostasis, cell growth and apoptosis. Recent studies have highlighted the important role of S6K in cancer, which arose interests of scientific researchers for the design and discovery of anti-cancer agents. Herein, the mechanisms of S6K and available inhibitors are reviewed.
Antineoplastic Agents ; Humans ; Protein Kinase Inhibitors ; chemistry ; Ribosomal Protein S6 Kinases, 70-kDa ; antagonists & inhibitors ; metabolism ; Signal Transduction ; TOR Serine-Threonine Kinases

Humans ; Leukemia ; drug therapy ; Phosphatidylinositol 3-Kinases ; antagonists & inhibitors ; Proto-Oncogene Proteins c-akt ; antagonists & inhibitors ; TOR Serine-Threonine Kinases ; antagonists & inhibitors

OBJECTIVETo explore apoptosis of multiple myeloma (MM) cells and its mechanism by the combined inhibition of mTORC2 signaling pathway and heat shock protein 90.

METHODSThe effects of Rapamycin, 17-AAG and the combination on proliferation of MM cell lines U266 and KM3 were assessed using MTT at different time points (0, 8, 24, 48 hour). Cell apoptosis and cell cycle distribution were measured by flow cytometry. The specific proteins p-AKT (ser473), p-AKT (thr450), p-S6 (S235/236) and AKT were detected by Western blotting.

RESULTSRapamycin, 17- AAG and the combination suppressed the proliferation of MM cell lines U266 and KM3, especially the combination of Rapamycin and 17-AAG synergistically inhibited the proliferation (P<0.05); Rapamycin induced G1 arrest both at 24 and 48 hours, 17-AAG also induced G1 arrest, especially at 48 hours (P<0.01); Rapamycin, 17-AAG alone decreased the expression of AKT and induced MM cell apoptosis to some extent (P<0.01); Chronic rapamycin treatment inhibited mTORC2; Inhibition of both mTORC2 and chaper on pathways degraded AKT and induced MM cell apoptosis, which was significantly higher than that of any single agent (P<0.01).

CONCLUSIONInhibition of both mTORC2 and chaper on pathways decreased the expression of AKT to induce apoptosis of MM cells in vitro.

Apoptosis ; Benzoquinones ; pharmacology ; Cell Cycle ; Cell Division ; Cell Line, Tumor ; drug effects ; HSP90 Heat-Shock Proteins ; metabolism ; Humans ; Lactams, Macrocyclic ; pharmacology ; Mechanistic Target of Rapamycin Complex 2 ; Multiple Myeloma ; pathology ; Multiprotein Complexes ; antagonists & inhibitors ; metabolism ; Proto-Oncogene Proteins c-akt ; metabolism ; Signal Transduction ; Sirolimus ; pharmacology ; TOR Serine-Threonine Kinases ; antagonists & inhibitors ; metabolism

We investigated how the dual inhibition of the molecular mechanism of the mammalian target of the rapamycin (mTOR) downstreams, P70S6 kinase (P70S6K) and eukaryotic initiation factor 4E (eIF4E), can lead to a suppression of the proliferation and progression of urothelial carcinoma (UC) in an orthotopic mouse non-muscle invasive bladder tumor (NMIBT) model. A KU-7-luc cell intravesically instilled orthotopic mouse NMIBC model was monitored using bioluminescence imaging (BLI) in vivo by interfering with different molecular components using rapamycin and siRNA technology. We then analyzed the effects on molecular activation status, cell growth, proliferation, and progression. A high concentration of rapamycin (10 microM) blocked both P70S6K and elF4E phosphorylation and inhibited cell proliferation in the KU-7-luc cells. It also reduced cell viability and proliferation more than the transfection of siRNA against p70S6K or elF4E. The groups with dual p70S6K and elF4E siRNA, and rapamycin reduced tumor volume and lamina propria invasion more than the groups with p70S6K or elF4E siRNA instillation, although all groups reduced photon density compared to the control. These findings suggest that both the mTOR pathway downstream of eIF4E and p70S6K can be successfully inhibited by high dose rapamycin only, and p70S6K and Elf4E dual inhibition is essential to control bladder tumor growth and progression.
Animals ; Cell Line ; Cell Proliferation/drug effects/genetics ; Cell Survival/drug effects ; Disease Progression ; Eukaryotic Initiation Factor-4E/*antagonists & inhibitors/genetics ; Female ; Mice ; Mice, Nude ; Mucous Membrane/pathology ; Phosphorylation/drug effects ; RNA Interference ; RNA, Small Interfering ; Ribosomal Protein S6 Kinases, 70-kDa/*antagonists & inhibitors/genetics ; Signal Transduction/drug effects ; Sirolimus/*pharmacology ; TOR Serine-Threonine Kinases/*antagonists & inhibitors/metabolism ; Urinary Bladder Neoplasms/genetics/*pathology ; Urothelium/pathology

We investigated how the dual inhibition of the molecular mechanism of the mammalian target of the rapamycin (mTOR) downstreams, P70S6 kinase (P70S6K) and eukaryotic initiation factor 4E (eIF4E), can lead to a suppression of the proliferation and progression of urothelial carcinoma (UC) in an orthotopic mouse non-muscle invasive bladder tumor (NMIBT) model. A KU-7-luc cell intravesically instilled orthotopic mouse NMIBC model was monitored using bioluminescence imaging (BLI) in vivo by interfering with different molecular components using rapamycin and siRNA technology. We then analyzed the effects on molecular activation status, cell growth, proliferation, and progression. A high concentration of rapamycin (10 microM) blocked both P70S6K and elF4E phosphorylation and inhibited cell proliferation in the KU-7-luc cells. It also reduced cell viability and proliferation more than the transfection of siRNA against p70S6K or elF4E. The groups with dual p70S6K and elF4E siRNA, and rapamycin reduced tumor volume and lamina propria invasion more than the groups with p70S6K or elF4E siRNA instillation, although all groups reduced photon density compared to the control. These findings suggest that both the mTOR pathway downstream of eIF4E and p70S6K can be successfully inhibited by high dose rapamycin only, and p70S6K and Elf4E dual inhibition is essential to control bladder tumor growth and progression.
Animals ; Cell Line ; Cell Proliferation/drug effects/genetics ; Cell Survival/drug effects ; Disease Progression ; Eukaryotic Initiation Factor-4E/*antagonists & inhibitors/genetics ; Female ; Mice ; Mice, Nude ; Mucous Membrane/pathology ; Phosphorylation/drug effects ; RNA Interference ; RNA, Small Interfering ; Ribosomal Protein S6 Kinases, 70-kDa/*antagonists & inhibitors/genetics ; Signal Transduction/drug effects ; Sirolimus/*pharmacology ; TOR Serine-Threonine Kinases/*antagonists & inhibitors/metabolism ; Urinary Bladder Neoplasms/genetics/*pathology ; Urothelium/pathology

An F-box protein, beta-TrCP recognizes substrate proteins and destabilizes them through ubiquitin-dependent proteolysis. It regulates the stability of diverse proteins and functions as either a tumor suppressor or an oncogene. Although the regulation by beta-TrCP has been widely studied, the regulation of beta-TrCP itself is not well understood yet. In this study, we found that the level of beta-TrCP1 is downregulated by various protein kinase inhibitors in triple-negative breast cancer (TNBC) cells. A PI3K/mTOR inhibitor PI-103 reduced the level of beta-TrCP1 in a wide range of TNBC cells in a proteasome-dependent manner. Concomitantly, the levels of c-Myc and cyclin E were also downregulated by PI-103. PI-103 reduced the phosphorylation of beta-TrCP1 prior to its degradation. In addition, knockdown of beta-TrCP1 inhibited the proliferation of TNBC cells. We further identified that pharmacological inhibition of mTORC2 was sufficient to reduce the beta-TrCP1 and c-Myc levels. These results suggest that mTORC2 regulates the stability of beta-TrCP1 in TNBC cells and targeting beta-TrCP1 is a potential approach to treat human TNBC.
Cell Line, Tumor ; Cell Proliferation ; Cell Survival/drug effects ; Cyclin E/genetics/metabolism ; Dose-Response Relationship, Drug ; Female ; Furans/pharmacology ; Gene Knockdown Techniques ; Humans ; Models, Biological ; Multiprotein Complexes/antagonists & inhibitors ; Phosphatidylinositol 3-Kinases/*antagonists & inhibitors ; Phosphorylation/drug effects ; Protein Kinase Inhibitors/*pharmacology ; Proteolysis/drug effects ; Proto-Oncogene Proteins c-myc/genetics/metabolism ; Pyridines/pharmacology ; Pyrimidines/pharmacology ; TOR Serine-Threonine Kinases/*antagonists & inhibitors ; Triple Negative Breast Neoplasms/genetics/*metabolism ; beta-Transducin Repeat-Containing Proteins/genetics/*metabolism

PURPOSE: To investigate the effects of resveratrol on the expression of hypoxia-inducible factor 1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) in human adult retinal pigment epithelial (ARPE-19) cells, and on experimental choroidal neovascularization (CNV) in mice. MATERIALS AND METHODS: ARPE-19 cells were treated with different concentrations of resveratrol and then incubated under hypoxic conditions with subsequent evaluation of cell viability, expression of HIF-1alpha, and expression of VEGF. The effects of resveratrol on the synthesis and degradation of hypoxia-induced HIF-1alpha were evaluated using inhibitors of the PI3K/Akt/mTOR and the ubiquitin proteasome pathways. In animal studies, CNV lesions were induced in C57BL/6 mice by laser photocoagulation. After 7 days of oral administration of resveratrol or vehicle, which began one day after CNV induction, image analysis was used to measure CNV areas on choroidal flat mounts stained with isolectin IB4. RESULTS: In ARPE-19 cells, resveratrol significantly inhibited HIF-1alpha and VEGF in a dose-dependent manner, by blocking the PI3K/Akt/mTOR signaling pathway and by promoting proteasomal HIF-1alpha degradation. In mice experiments, orally administered resveratrol significantly inhibited CNV growth in a dose-dependent manner. CONCLUSION: Resveratrol may have therapeutic value in the management of diseases involving pathological neovascularization.
Adult ; Animals ; Anoxia/metabolism/physiopathology ; Cell Survival/drug effects ; Choroidal Neovascularization/*metabolism/pathology ; Humans ; Hypoxia-Inducible Factor 1, alpha Subunit/*drug effects/metabolism ; Mice ; Mice, Inbred C57BL ; Phosphatidylinositol 3-Kinases/antagonists & inhibitors/*physiology ; Proteasome Endopeptidase Complex ; Proto-Oncogene Proteins c-akt/antagonists & inhibitors/*physiology ; Retinal Pigment Epithelium/*drug effects/metabolism ; Signal Transduction ; Stilbenes/administration & dosage/*pharmacology ; TOR Serine-Threonine Kinases/antagonists & inhibitors/*physiology ; Ubiquitin ; Vascular Endothelial Growth Factor A/*drug effects/metabolism