Retracted: MicroRNA-99b suppresses human cervical cancer cell activity by inhibiting the PI3K/AKT/mTOR signaling pathway

Cervical cancer is common cancer among women with high morbidity. MicroRNAs (miRs) are involved in the progression and development of cervical cancer. This study aimed to explore the effect of miR-99b-5p (miR-99b) on invasion and migration in cervical cancer through the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) signaling pathway. The microarray-based analysis was used to screen out differentially expressed miRNAs. Expression of miR-99b, PI3K, AKT, mTOR, and ribosomal protein S6 kinase (p70S6K) was determined in both cervical cancer tissues and paracancerous tissues. Next, alteration of miR-99b expression in cervical cancer was conducted to evaluate levels of PI3K, AKT, mTOR, p70S6K matrix metallopeptidase 2, epithelial cell adhesion molecule, and intercellular adhesion molecule 1, as well as the effect of miR-99b on cell proliferation, invasion, migration, cell cycle distribution, and apoptosis. The results demonstrated that miR-99b expression was decreased and levels of PI3K, AKT, mTOR, and p70S6K were elevated in cervical cancer tissues. More important, overexpressed miR-99b repressed the PI3K/AKT/mTOR signaling pathway, inhibited cell proliferation, invasion, and migration, blocked cell cycle entry, and promoted apoptosis in cervical cancer. These results indicate that miR-99b attenuates the migration and invasion of human cervical cancer cells through downregulation of the PI3K/AKT/mTOR signaling pathway, which provides a therapeutic approach for cervical cancer treatment.     

Facile construction of fused benzimidazole-isoquinolinones that induce cell-cycle arrest and apoptosis in colorectal cancer cells

Colorectal cancer (CRC) is one of the most frequent, malignant gastrointestinal tumors, and strategies and effectiveness of current therapy are limited. A series of benzimidazole-isoquinolinone derivatives (BIDs) was synthesized and screened to identify novel scaffolds for CRC. Of the compounds evaluated, 7g exhibited the most promising anti-cancer properties. Employing two CRC cell lines, SW620 and HT29, 7g was found to suppress growth and proliferation of the cell lines at a concentration of ～20?µM. Treatment followed an increase in G₂/M cell cycle arrest, which was attributed to cyclin B1 and cyclin-dependent kinase 1 (CDK1) signaling deficiencies with simultaneous enhancement in p21 and p53 activity. In addition, mitochondrial-mediated apoptosis was induced in CRC cells. Interestingly, 7g decreased phosphorylated AKT, mTOR and 4E-BP1 levels, while promoting the expression/stability of PTEN. Since PTEN controls input into the PI3K/AKT/mTOR pathway, antiproliferative effects can be attributed to PTEN-mediated tumor suppression. Collectively, these results suggest that BIDs exert antitumor activity in CRC by impairing PI3K/AKT/mTOR signaling. Against a small kinase panel, 7g exhibited low affinity at 5?µM suggesting anticancer properties likely stem through a non-kinase mechanism. Because of the novelty of BIDs, the structure can serve as a lead scaffold to design new CRC therapies.     

Retracted: Long noncoding RNA HAGLROS regulates apoptosis and autophagy in colorectal cancer cells via sponging miR-100 to target ATG5 expression

The aim of this study was to explore the relationship between the expression of HOXD antisense growth-associated long noncoding RNA (HAGLROS) and prognosis of patients with colorectal cancer (CRC), as well as the roles and regulatory mechanism of HAGLROS in CRC development. The HAGLROS expression in CRC tissues and cells was detected. The correlation between HAGLROS expression and survival time of CRC patients was investigated. Moreover, HAGLROS was overexpressed and suppressed in HCT-116 cells, followed by detection of cell viability, apoptosis, and the expression of apoptosis-related proteins and autophagy markers. Furthermore, the association between HAGLROS and miR-100 and the potential targets of miR-100 were investigated. Besides, the regulatory relationship between HAGLROS and PI3K/AKT/mTOR pathway was elucidated. The results showed that HAGLROS was highly expressed in CRC tissues and cells. Highly expression of HAGLROS correlated with a shorter survival time of CRC patients. Moreover, knockdown of HAGLROS in HCT-116 cells induced apoptosis by increasing the expression of Bax/Bcl-2 ratio, cleaved-caspase-3, and cleaved-caspase-9, and inhibited autophagy by decreasing the expression of LC3II/LC3I and Beclin-1 and increasing P62 expression. Furthermore, HAGLROS negatively regulated the expression of miR-100, and HAGLROS controlled HCT-116 cell apoptosis and autophagy through negatively regulation of miR-100. Autophagy related 5 (ATG5) was verified as a functional target of miR-100 and miR-100 regulated HCT-116 cell apoptosis and autophagy through targeting ATG5. Besides, HAGLROS overexpression activated phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway. In conclusion, a highly expression of HAGLROS correlated with shorter survival time of CRC patients. Downregulation of HAGLROS may induce apoptosis and inhibit autophagy in CRC cells by regulation of miR-100/ATG5 axis and PI3K/AKT/mTOR pathway.     

microRNA-16-5p suppresses cell proliferation and angiogenesis in colorectal cancer by negatively regulating forkhead box K1 to block the PI3K/Akt/mTOR pathway

MicroRNAs (miRNAs/miRs) have aroused increasing attention in colorectal cancer (CRC) therapy. This study is designed for a detailed analysis of the roles of miR-16-5p and forkhead box K1 (FOXK1) in cell angiogenesis and proliferation during CRC in addition to their underlying mechanisms. CRC tissues and colon cancer cell lines (SW620 and HCT8) were investigated. qRT-PCR and Western blot were utilized to evaluate miR-16-5p and FOXK1 expression. Following gain- and loss-of-function assays on miR-16-5p or FOXK1, the effects of miR-16-5p and FOXK1 were assessed on cell angiogenesis and proliferation in CRC cells. A dual-luciferase reporter assay was employed to evaluate the binding relationship of miR-16-5p and FOXK1. Western blot was used to determine the effects of miR-16-5p and FOXK1 on key molecules of the PI3K/Akt/mTOR pathway. Highly expressed FOXK1 and lowly expressed miR-16-5p were observed in CRC cells and tissues. miR-16-5p overexpression or FOXK1 knockdown reduced CRC cell proliferation and angiogenesis of human umbilical vein endothelial cells co-cultured with the supernatant of CRC cells, whereas miR-16-5p silencing or FOXK1 upregulation caused opposite trends. Additionally, miR-16-5p negatively modulated FOXK1 expression. The blockade of the PI3K/Akt/mTOR pathway was triggered by miR-16-5p overexpression or FOXK1 silencing. In conclusion, miR-16-5p hampers cell angiogenesis and proliferation during CRC by targeting FOXK1 to block the PI3K/Akt/mTOR pathway.Key words: microRNA-16-5p, forkhead box K1, PI3K/Akt/mTOR pathway, colorectal cancer, proliferation, angiogenesis     

Silencing of FOXO6 inhibits the proliferation,invasion, and glycolysis in colorectal cancer cells

Forkhead box class O6 (FOXO6) is an important member of FOXO family, which has been demonstrated to be implicated in tumor development. However, the role of FOXO6 in colorectal cancer (CRC) is still unclear. The study aimed to investigate the potential roles of FOXO6 in the development of CRC. Our results showed that FOXO6 was overexpressed in CRC tissues and cell lines. FOXO6 knockdown inhibited cell proliferation, as well as repressed the migration and invasion of CRC cells. Additionally, we found that FOXO6 knockdown altered cellular metabolism by inhibiting glycolysis and promoting mitochondrial respiration. Furthermore, FOXO6 knockdown inhibited the activation of PI3K/Akt/mTOR pathway in CRC cells. The results herein indicated that FOXO6 knockdown inhibited cell proliferation, migration, invasion, and glycolysis in CRC cells. PI3K/Akt/mTOR pathway was involved in the effects of FOXO6 on CRC cells. These findings suggested that FOXO6 might be a potential target for the CRC therapy.     

HOTAIR/miR-326/FUT6 axis facilitates colorectal cancer progression through regulating fucosylation of CD44 via PI3K/AKT/mTOR pathway

Metastasis is the main cause of death in colorectal cancer (CRC) patients. Aberrant fucosylation, catalyzed by the specific fucosyltransferases (FUTs), is associated with malignant behaviors. Non-conding RNAs, including long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), emerge as key molecules in cancer malignancy. The aim of this study was to investigate HOTAIR/miR-326/FUT6 axis modified fucosylation on sLe^X-CD44 (HCELL), which served as E-selectin ligand during CRC progression. Higher levels of HOTAIR and FUT6 were verified in CRC tissues and cell lines, with a positive correlation. HOTAIR was associated with poor clinical prognosis of CRC. Altered HOTAIR levels influenced proliferation, aggressiveness, apoptosis and tumorigenesis of CRC cells. HOTAIR directly harbored miR-326 binding sites and regulated FUT6 expression. Further results corroborated that HOTAIR/miR-326/FUT6 axis modified α1, 3-fucosylation of CD44, which mediated CRC malignancy. Co-modulation of HOTAIR, miR-326 and FUT6 impacted α1, 3-fucosylated CD44, which further triggered PI3K/AKT/mTOR pathway. HOTAIR also mediated CRC tumorigenesis and liver metastasis in vivo. Thus, our findings indicated that HOTAIR/miR-326/FUT6 axis mediated CRC procession through α1, 3-fucosylated CD44 via PI3K/AKT/mTOR pathway. This work rendered new therapeutic targets for CRC.     

TUFT1 Facilitates Metastasis,Stemness, and Vincristine Resistance in Colorectal Cancer via Activation of PI3K/AKT Pathway

Since the incidence and mortality of colorectal cancer (CRC) are increasing in recent years, the research on the pathogenesis of colorectal cancer has attracted more and more attention. Here, our results confirmed that the mRNA expression level and proteins accumulation of TUFT1 were significantly increased in CRC tissues from late-stage CRC patients (III?+?IV) (p?<?0.001), indicated by qPCR and IHC assay. The TUFT1 expression was positively correlated with tumor stage by analyzing 126 specimens from CRC patients. Next, we found that up-regulation of TUFT1 enhanced the migration and invasion of LoVo cells, whereas the down-regulation of TUFT1 observably weakened the migration and invasion of SW837 cells, indicating that TUFT1 promotes the metastasis of CRC cells. In addition, TUFT1 overexpression increased the number of mammary spheres and vincristine resistance of LoVo cells by sphere formation assay and measuring the IC50 value, suggesting the TUFT1 promotes stemness and the vincristine resistance of CRC cells. Finally, we found that TUFT1 overexpression increased p-AKT in LoVo cells, while down-regulation of TUFT1 decreased the p-AKT levels in SW837 cells. Therefore, we determined that the function of TUFT1 in CRC depends on PI3K/AKT pathway. Taken together, these data demonstrated that TUFI1 facilitates metastasis, stemness, and vincristine resistance of colorectal cancer cells via activation of PI3K/AKT pathway, which might act as a promising therapeutic target for CRC.

     

Inhibition of autophagy enhances apoptosis induced by the PI3K/AKT/mTor inhibitor NVP‐BEZ235 in renal cell carcinoma cells

The PI3K/AKT/mTOR pathway plays a key role in the development of the hypervascular tumor renal cell carcinoma (RCC). NVP‐BEZ235 (NVP), a novel dual PI3K/mTOR inhibitor, showed great antitumor benefit and provided a treatment strategy in RCC. In this study, we test the effect of NVP on survival rate, apoptosis and autophagy in the RCC cell line, 786‐0. We also explore the hypothesis that NVP, in combination with autophagy inhibitors, leads to apoptosis enhancement in 786‐0 cells. The results showed that the PI3K/AKT/mTOR pathway proteins p‐AKT and p‐P70S6K were highly expressed in RCC tissue. We also showed that NVP inhibited cell growth and induced apoptosis and autophagy in RCC cells. The combination treatment of NVP with autophagy inhibitors enhanced the effect of NVP on suppressing 786‐0 growth and induction of apoptosis. This study proposes a novel treatment paradigm where combining PI3K/AKT/mTOR pathway inhibitors and autophagy inhibitors lead to enhanced RCC cell apoptosis. Copyright © 2012 John Wiley & Sons, Ltd.     

LY294002 and Rapamycin promote coxsackievirus-induced cytopathic effect and apoptosis via inhibition of PI3K/AKT/mTOR signaling pathway

Coxsackievirus B3 (CVB3) is a common human pathogen for acute myocarditis, pancreatitis, non-septic meningitis, and encephalitis; it induces a direct cytopathic effect (CPE) and apoptosis on infected cells. The Phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT/PKB)/mammalian target of Rapamycin (mTOR) signaling pathway regulates several cellular processes and it is one of the most important pathways in human networks. However, the effect and mechanism of PI3K/AKT/mTOR signaling pathway in CVB3 infected cells are poorly understood. In this study, we demonstrate that inhibition of PI3K/AKT/mTOR signaling pathway increased CVB3-induced CPE and apoptosis in HeLa cells. The activity of downstream targets of PI3K and mTOR is attenuated after CVB3 infection and inhibitors of PI3K and mTOR made their activity to decrease more significantly. We further show that LY294002 and Rapamycin, the inhibitor of PI3K and mTOR respectively, promote CVB3-induced CPE and apoptosis. Taken together, these data illustrate a new and imperative role for PI3K/AKT/mTOR signaling in CVB3 infection in HeLa cells and suggest an useful approach for the therapy of CVB3 infection.     

PC-1解除S6K对AKT信号通路的负反馈抑制

目的:通过建立过表达PC-1的前列腺癌LNCaP细胞系及敲低PC-1表达的C4-2细胞系,探究PC-1激活AKT信号通路的分子机制。方法:将PC-1基因及针对PC-1的siRNA序列,分别克隆至慢病毒表达载体pCDH-EF1-Myc-MCS-T2A-Puro及干扰载体pSIH1-H1-Puro,包装成慢病毒后分别感染前列腺癌LNCaP及C4-2细胞,通过Western印迹鉴定PC-1过表达及敲低效果,并检测PI3K/AKT/mTOR信号通路相关蛋白S6K、AKT的磷酸化水平。结果:PC-1过表达时,S6K磷酸化水平下降,而AKT的磷酸化水平上升。结论:PC-1可以通过抑制S6K激酶活性,解除其对AKT的负反馈抑制作用,从而激活AKT激酶的活性。     

The Prolyl Peptidases PRCP/PREP Regulate IRS-1 Stability Critical for Rapamycin-induced Feedback Activation of PI3K and AKT

The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT)/mammalian target of rapamycin (mTOR) pathway conveys signals from receptor tyrosine kinases (RTKs) to regulate cell metabolism, proliferation, survival, and motility. Previously we found that prolylcarboxypeptidase (PRCP) regulate proliferation and survival in breast cancer cells. In this study, we found that PRCP and the related family member prolylendopeptidase (PREP) are essential for proliferation and survival of pancreatic cancer cells. Depletion/inhibition of PRCP and PREP-induced serine phosphorylation and degradation of IRS-1, leading to inactivation of the cellular PI3K and AKT. Notably, depletion/inhibition of PRCP/PREP destabilized IRS-1 in the cells treated with rapamycin, blocking the feedback activation PI3K/AKT. Consequently, inhibition of PRCP/PREP enhanced rapamycin-induced cytotoxicity. Thus, we have identified PRCP and PREP as a stabilizer of IRS-1 which is critical for PI3K/AKT/mTOR signaling in pancreatic cancer cells.     

Anhuienoside C inhibits human ovarian cancer cell growth by inducing apoptosis,suppression of cell migration and invasion,and targeting PI3K/AKT/mTOR signaling pathway

The present study was initiated to examine the anticancer effects of Anhuienoside C (AC) against ovarian cancer and postulates the possible molecular mechanism of its action. 3-[4,5-Dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay was implemented for determination of the effects of AC on cell viability of the ovarian cancer OVACAR-3 cell line. To study cellular morphology, phase contrast microscopy was performed. Apoptosis was examined via acridine orange/ethidium bromide used staining assays. Flow cytometry was used to check the different phases of the cell cycle. Cell migration and invasion assays were performed via transwell chamber assay. The effects of AC on expression of phosphoinositide 3-kinases (PI3K), protein kinase B (AKT), and mammalian target of rapamycin (mTOR) protein in ovarian cell were assessed using western blotting assay. The results indicated that the cell proliferation rate lowered in AC-treated OVACAR-3 cells as compared to the untreated controls in a dose-dependent manner. Cell morphology changed substantially by the exposure to AC and remained dose dependent. These morphological changes were indicative of apoptotic cell death. Apoptosis analysis showed dose-dependent increase of apoptosis. The cell migration and invasion of OVACAR-3 cells was reduced to a minimum by AC in a dose-dependent manner. Finally, western blotting assay showed blocking of PI3K/AKT/mTOR signaling pathway with increasing AC doses. Taking all together, AC is a potential ovarian cancer inhibitor. It induces its anti-ovarian cancer effects via induction of apoptosis, delaying cell migration and invasion, and blocking PI3K/AKT/mTOR signaling pathway.

     

Long noncoding RNA H19 promotes chemotherapy resistance in choriocarcinoma cells

Choriocarcinoma (CC) is a trophoblast tumor prone to early distant organ metastases. At present, the main treatment for CC is chemotherapy, but chemotherapy resistance readily occurs and leads to treatment failure. H19 is a long noncoding RNA, and its abnormal expression has been found in various tumors, including CC. H19 is also considered to be related to the drug resistance mechanism of the same cancers. To investigate the role of H19 in drug-resistant CC cells, the following experiments were designed. We used human CC cell line JEG-3 to establish cell lines resistant to methotrexate and 5-fluorouracil (JEG-3/MTX and JEG-3/5-FU) and detected the expression of H19 in JEG-3, JEG-3/MTX, JEG-3/5-FU cells, JEG-3 with MTX, and JEG-3 with 5-FU. We found that the expression of H19 in the JEG-3/MTX and JEG-3/5-FU cells were significantly higher than that in JEG-3 cells. JEG-3 cells were treated with MTX or 5-FU for and quantitative real-time polymerase chain reaction assay revealed that H19 messenger RNA expression increased. Furthermore, after H19 was knocked out, the drug resistance index of the JEG-3/MTX and JEG-3/5-FU cells decreased; the proliferation, migration, and invasion ability diminished significantly; and apoptosis increased significantly. Finally, we detected the total and phosphorylation protein expression of phosphatidylinositol-3-kinase (PI3K), protein kinase B (AKT), and mammalian target of rapamycin (mTOR) in the JEG-3/MTX and JEG-3/5-FU cells. The total protein of PI3K, AKT, and mTOR in the H19 knockout resistant cells showed no significant change relative to those in the H19 non-knockout resistant cells, whereas the phosphorylated proteins of PI3K, AKT, and mTOR were significantly decreased. Phosphorylated proteins of PI3K, AKT, and mTOR in the JEG-3/MTX and JEG-3/5-FU cells were significantly higher than that in JEG-3 cells. After using inhibition of phosphorylated PI3K/AKT/mTOR, the proliferation, migration, and invasion ability of the JEG-3/MTX and JEG-3/5-FU cells diminished significantly; and apoptosis increased significantly. On the basis of the above experiments, we concluded that H19 is related to the drug resistance of CC, and the knockout of H19 can reduce the drug resistance of resistant CC cells; and decrease the proliferative, migratory, and invasive ability; and increase the apoptosis. PI3K/AKT/mTOR pathway might be involved in H19-mediated effects. H19 is expected to be a therapeutic target for the treatment of drug-resistant chorionic carcinoma.     

Design,synthesis, and cytotoxic activities of isaindigotone derivatives as potential anti-gastric cancer agents

A series of novel derivatives of isaindigotone, which comes from the root of isaits indinatca Fort, were synthesised (Compound 1–26). Four human gastrointestinal cancer cells (HCT116, PANC-1, SMMC-7721, and AGS) were employed to evaluate the anti-proliferative activity. Among them, Compound 6 displayed the most effective inhibitory activity on AGS cells with an IC₅₀ (50% inhibitory concentration) value of 2.2 μM. The potential mechanism study suggested that Compound 6 induced apoptosis in AGS cells. The collapse of mitochondrial membrane potential (MMP) in AGS cells was proved. In docking analysis, good affinity interaction between Compound 6 and AKT1 was discovered. Treatment of AGS cells with Compound 6 also resulted in significant suppression of PI3K/AKT/mTOR signal pathway. The collapse of MMP and suppression of PI3K/AKT/mTOR signal pathway may be responsible for induction of apoptosis. This derivative Compound 6 could be useful as an underlying anti-tumour agent for treatment of gastric cancer.     

Signaling through the Phosphatidylinositol 3-Kinase (PI3K)/Mammalian Target of Rapamycin (mTOR) Axis Is Responsible for Aerobic Glycolysis mediated by Glucose Transporter in Epidermal Growth Factor Receptor (EGFR)-mutated Lung Adenocarcinoma

Oncogenic epidermal growth factor receptor (EGFR) signaling plays an important role in regulating global metabolic pathways, including aerobic glycolysis, the pentose phosphate pathway (PPP), and pyrimidine biosynthesis. However, the molecular mechanism by which EGFR signaling regulates cancer cell metabolism is still unclear. To elucidate how EGFR signaling is linked to metabolic activity, we investigated the involvement of the RAS/MEK/ERK and PI3K/AKT/mammalian target of rapamycin (mTOR) pathways on metabolic alteration in lung adenocarcinoma (LAD) cell lines with activating EGFR mutations. Although MEK inhibition did not alter lactate production and the extracellular acidification rate, PI3K/mTOR inhibitors significantly suppressed glycolysis in EGFR-mutant LAD cells. Moreover, a comprehensive metabolomics analysis revealed that the levels of glucose 6-phosphate and 6-phosphogluconate as early metabolites in glycolysis and PPP were decreased after inhibition of the PI3K/AKT/mTOR pathway, suggesting a link between PI3K signaling and the proper function of glucose transporters or hexokinases in glycolysis. Indeed, PI3K/mTOR inhibition effectively suppressed membrane localization of facilitative glucose transporter 1 (GLUT1), which, instead, accumulated in the cytoplasm. Finally, aerobic glycolysis and cell proliferation were down-regulated when GLUT1 gene expression was suppressed by RNAi. Taken together, these results suggest that PI3K/AKT/mTOR signaling is indispensable for the regulation of aerobic glycolysis in EGFR-mutated LAD cells.     

mTOR is a fine tuning molecule in CDK inhibitors-induced distinct cell death mechanisms via PI3K/AKT/mTOR signaling axis in prostate cancer cells

Purvalanol and roscovitine are cyclin dependent kinase (CDK) inhibitors that induce cell cycle arrest and apoptosis in various cancer cells. We further hypothesized that co-treatment of CDK inhibitors with rapamycin, an mTOR inhibitor, would be an effective combinatory strategy for the inhibition of prostate cancer regard to androgen receptor (AR) status due to inhibition of proliferative pathway, PI3K/AKT/mTOR, and induction of cell death mechanisms. Androgen responsive (AR+), PTEN^?/? LNCaP and androgen independent (AR?), PTEN^+/? DU145 prostate cancer cells were exposed to purvalanol (20 µM) and roscovitine (30 µM) with or without rapamycin for 24 h. Cell viability assay, immunoblotting, flow cytometry and fluorescence microscopy was used to define the effect of CDK inhibitors with or without rapamycin on proliferative pathway and cell death mechanisms in LNCaP and DU145 prostate cancer cells. Co-treatment of rapamycin modulated CDK inhibitors-induced cytotoxicity and apoptosis that CDK inhibitors were more potent to induce cell death in AR (+) LNCaP cells than AR (?) DU145 cells. CDK inhibitors in the presence or absence of rapamycin induced cell death via modulating upstream PI3K/AKT/mTOR signaling pathway in LNCaP cells, exclusively only treatment of purvalanol have strong potential to inhibit both upstream and downstream targets of mTOR in LNCaP and DU145 cells. However, co-treatment of rapamycin with CDK inhibitors protects DU145 cells from apoptosis via induction of autophagy mechanism. We confirmed that purvalanol and roscovitine were strong apoptotic and autophagy inducers that based on regulation of PI3K/AKT/mTOR signaling pathway. Co-treatment of rapamycin with purvalanol and roscovitine exerted different effects on cell survival and death mechanisms in LNCaP and DU145 cell due to their AR receptor status. Our studies show that co-treatment of rapamycin with CDK inhibitors inhibit prostate cancer cell viability more effectively than either agent alone, in part, by targeting the mTOR signaling cascade in AR (+) LNCaP cells. In this point, mTOR is a fine-tuning player in purvalanol and roscovitine-induced apoptosis and autophagy via regulation of PI3K/AKT and the downstream targets, which related with cell proliferation.     

ROS accumulation contributes to abamectin‐induced apoptosis and autophagy via the inactivation of PI3K/AKT/mTOR pathway in TM3 Leydig cells

Abamectin (ABA) as one of the worldwide used compounds in agriculture has raised safety concerns on nontarget organism toxicity. However, the study of male reproductive system damage caused by ABA remains unclear. Our aim is to investigate the effect of ABA‐induced cytotoxicity in TM3 Leydig cells and their underlying mechanisms. ABA inhibits TM3 cell viability and proliferation via cell cycle arrested in the G0/G1 phase. In addition, ABA‐induced mitochondrial depolarization leads to an imbalance in Bcl‐2 family expression, causing caspase‐dependent apoptosis in TM3 cells. The increased ratio of cells expression LC3 protein and LC3‐II to LC3‐I indicated the activation of autophagy potentially. Further experiments revealed ABA treatment reduced phosphatidylinositol 3‐kinase (PI3K), protein kinase B (AKT) phosphorylation, and mammalian target of rapamycin (mTOR) phosphorylation. Pretreatment with a PI3K/AKT inhibitor, LY294002, mimicked the ABA‐mediated effects on cytotoxicity. Pretreatment with a PI3K/AKT agonist, insulin‐like growth factor‐1, reversed the effects of ABA. ABA caused the accumulation of intracellular reactive oxygen species (ROS) by increased intensity of the ROS indicator. However, N‐acetylcysteine as ROS scavengers inhibited ABA‐induced apoptosis and autophagy and reversed these ABA‐mediated effects on PI3K/AKT/mTOR pathway. On the basis of the above results, it is suggested that ABA exposure induces apoptosis and autophagy in TM3 cells by ROS accumulation to mediate PI3K/AKT/mTOR signaling pathway suppression.     

Angiogenin interacts with ribonuclease inhibitor regulating PI3K/AKT/mTOR signaling pathway in bladder cancer cells

Angiogenin (ANG), a member of RNase A superfamily, is the only angiogenic factor that possesses ribonucleolytic activity. Recent studies showed that the expression of ANG was elevated in various types of cancers. Accumulating evidence indicates that ANG plays an essential role in cancer progression by stimulating both cancer cell proliferation and tumor angiogenesis. Human ribonuclease inhibitor (RI), a cytoplasmic protein, is constructed almost entirely of leucine rich repeats (LRRs), which are present in a large family of proteins that are distinguished by their display of vast surface areas to foster protein–protein interactions. RI might be involved in unknown biological effects except inhibiting RNase A activity. The experiment demonstrated that RI also could suppress activity of angiogenin (ANG) through closely combining with it in vitro. PI3K/AKT/mTOR signaling pathway exerts a key role in cell growth, survival, proliferation, apoptosis and angiogenesis. We recently reported that up-regulating RI inhibited the growth and induced apoptosis of murine melanoma cells through repression of angiogenin and PI3K/AKT signaling pathway. However, ANG receptors have not yet been identified to date, its related signal transduction pathways are not fully clear and underlying interacting mechanisms between RI and ANG remain largely unknown. Therefore, we hypothesize that RI might combine with intracellular ANG to block its nuclear translocation and regulate PI3K/AKT/mTOR signaling pathway to inhibit biological functions of ANG. Here, we reported for the first time that ANG could interact with RI endogenously and exogenously by using co-immunoprecipitation (Co-IP) and GST pull-down. Furthermore, we observed the colocalization of ANG and RI in cells with immunofluorescence staining under laser confocal microscope. Moreover, through fluorescence resonance energy transfer (FRET) assay, we further confirmed that these two proteins have a physical interaction in living cells. Subsequently, we demonstrated that up-regulating ANG including ANG His37Ala mutant obviously decreased RI expression and activated phosphorylation of key downstream target molecules of PI3K/AKT/mTOR signaling pathway. Finally, up-regulating ANG led to the promotion of tumor angiogenesis, tumorigenesis and metastasis in vivo. Taken together, our data provided a novel mechanism of ANG in regulating PI3K/AKT/mTOR signaling pathway via RI, which suggested a new therapeutic target for cancer therapy.     

G1 cell cycle progression and the expression of G1 cyclins are regulated by PI3K/AKT/mTOR/p70S6K1 signaling in human ovarian cancer cells

Ovarian cancer is one of the most common cancers among women. Recent studies demonstrated that the gene encoding the p110alpha catalytic subunit of phosphatidylinositol 3-kinase (PI3K) is frequently amplified in ovarian cancer cells. PI3K is involved in multiple cellular functions, including proliferation, differentiation, antiapoptosis, tumorigenesis, and angiogenesis. In this study, we demonstrate that the inhibition of PI3K activity by LY-294002 inhibited ovarian cancer cell proliferation and induced G(1) cell cycle arrest. This effect was accompanied by the decreased expression of G(1)-associated proteins, including cyclin D1, cyclin-dependent kinase (CDK) 4, CDC25A, and retinoblastoma phosphorylation at Ser(780), Ser(795), and Ser(807/811). Expression of CDK6 and beta-actin was not affected by LY-294002. Expression of the cyclin kinase inhibitor p16(INK4a) was induced by the PI3K inhibitor, whereas steady-state levels of p21(CIP1/WAF1) were decreased in the same experiment. The inhibition of PI3K activity also inhibited the phosphorylation of AKT and p70S6K1, but not extracellular regulated kinase 1/2. The G(1) cell cycle arrest induced by LY-294002 was restored by the expression of active forms of AKT and p70S6K1 in the cells. Our study shows that PI3K transmits a mitogenic signal through AKT and mammalian target of rapamycin (mTOR) to p70S6K1. The mTOR inhibitor rapamycin had similar inhibitory effects on G(1) cell cycle progression and on the expression of cyclin D1, CDK4, CDC25A, and retinoblastoma phosphorylation. These results indicate that PI3K mediates G(1) progression and cyclin expression through activation of an AKT/mTOR/p70S6K1 signaling pathway in the ovarian cancer cells.