Target Of Rapamycin Axis Research Articles

Kaempferol Promotes Apoptosis and Inhibited Autophagy in A549 Cells via MicroRNA-199/Mammalian Target of Rapamycin Axis

To explore the function of kaempferol on the lung cancer cell A549 and the microRNA-199 variation is the objective of the study. The cell proliferation was detected by cell counting kit-8. The expression of mammalian target of rapamycin, phosphorylated mammalian target of rapamycin, light chain 3-?/?, beclin-1, B-cell lymphoma 2 and B-cell lymphoma 2-associated X protein was showed by Western blot. The microRNA-199 expression was determined by quantitative polymerase chain reaction. The adenocarcinomic human alveolar basal epithelial cells, A549 proliferation was gradually low with the concentration of kaempferol rising. Kaempferol could inhibit the microRNA-199, phosphorylated mammalian target of rapamycin, light chain 3-?/?, beclin-1 and B-cell lymphoma 2-associated X protein expression and promoted B-cell lymphoma 2 expressions. When microRNA-199 inhibited the expression of phosphorylated mammalian target of rapamycin, light chain 3-?/? and beclin-1 in the kaempferol+microRNA-199 inhibitor group was lower than blank group and kaempferol added only group. In the kaempferol+microRNA-199 inhibitor group, the B-cell lymphoma 2 was lower than the blank group and kaempferol added only group. When the mammalian target of rapamycin was inhibited the expression of light chain 3-?/? and beclin-1 was low. The B-cell lymphoma 2 was low and the B-cell lymphoma 2-associated X protein was high in the two groups. The kaempferol promoted the apoptosis and inhibited autophagy in A549 cells via microRNA/mammalian target of rapamycin axis.

MicroRNA-591 Functions as a Tumor Suppressor in Hepatocellular Carcinoma by Lowering Drug Resistance through Inhibition of Far-Upstream Element-Binding Protein 2-Mediated Phosphoinositide 3-Kinase/Akt/Mammalian Target of Rapamycin Axis

MicroRNAs, a group of noncoding regulatory RNAs, are involved in oncogenesis, cell survival, and chemosensitivity. First, microarray-based analysis predicted that far-upstream element-binding protein 2 (FBP2) was upregulated in hepatocellular carcinoma (HCC), which may be regulated by miR-591. In this study, we hypothesize an inhibitory role of miR-591 in HCC via regulating FBP2. Next, reverse transcription quantitative polymerase chain reaction found that FBP2 expressed highly and miR-591 expresses poorly in HCC tissues. Then, the negative correlation between miR-591 and mRNA expression of FBP2 was identified by Pearson’s correlation coefficient, and putative miR-591-binding sites on the 3′-untranslated region of FBP2 was validated using a dual-luciferase reporter gene assay. After the expression of miR-591 and FBP2 was altered in the drug-resistant CD133⁺/CD44⁺ cells, a series of in vitro and in vivo experiments demonstrated that either miR-591 overexpression or FBP2 silencing inhibited the abilities of sphere formation and colony formation, drug resistance, as well as tumorigenicity. It was further observed that miR-591 could suppress FBP2 expression by blocking the phosphoinositide 3-kinase/Akt/mammalian target of rapamycin axis. Above results highlighted an inhibitory effect of miR-591 on the development of HCC by reducing the drug resistance of HCC stem cells. It revealed miR-591 as a new target in the treatment of HCC.

Abstract 4667: A synergistic combination strategy for optimal inhibition of colon cancer stem cells: Simultaneous inhibition of Insulin-like growth factor-1 receptor-AKT-mammalian target of rapamycin axis and the mevalonate-isoprenoid biosynthetic pathway

Abstract Introduction: Targeting cancer stem cells (CSCs) is an attractive new paradigm to achieve long-term remission/cure. The mevalonate-isoprenoid biosynthetic (MIB) pathway is critical in the regulation of colonic CSCs. However, feedback activation of SREBP2 following inhibition of the MIB pathway reduces the efficiency of the latter strategy. We described that Insulin-like growth factor-1 receptor-AKT-mammalian target of rapamycin (InAT) axis inhibits CSCs via inhibition of the MIB pathway at a level distinct from the target of statin - HMGCR, while simultaneously inhibiting SREBP2. Hence, we hypothesized that combining a MIB pathway inhibitor with the InAT axis inhibition will result in optimal inhibition of CSCs. Methods: Four possible combinations with the MIB pathway inhibitors (Simvastatin or zoledronate) and an InAT axis inhibitors (OSI-906) or Everolimus were tested against spheroids from 12 colorectal cancer cells. Synergistic effect of the combinations was determined using Chou Talalay method (Calcusyn). Most promising combinations were examined in an in vivo model of Dual high CSCs (CD133+/CXCR4+) induced xenografts to assess tumor volume, and ex vivo CSC phenotype (spheroid formation and CSC marker expression) in xenograft-derived cells. Results: OSI-906 + Simvastatin, as well as Everolimus + simvastatin, showed a robust synergistic effect (Combination index <0.75) in a majority of colon cancer cells which was independent of mutation in PI3K/mTOR or RAS pathways. In fact, both the combinations showed a significantly higher inhibition of Dual high CSCs-induced xenograft volume as well as ex-vivo spheroid formation (2°→4°) and CSC markers (CD133, DCLK1, LGR etc.) than either agents alone or vehicle controls in two model of colon cancer HCT-116 (MSI high, KRAS mut), HT29 (MSS, KRAS mut). Importantly, Simvastatin treatment failed to inhibit SREBP2 levels. However, InAT axis inhibitors caused a significant inhibition of SREBP2 and the MIB pathway genes. In fact, inhibition of the MIB pathway at the level of isopentenyl-diphosphate delta isomerase 1 (IDI1) was critical for simultaneous inhibition of the MIB pathway and InAT axis to attenuate CSC self-renewal as supplementation with DMAPP, and FPP, but not mevalonate or IPP, reversed the effect of the combination on CSCs. Conclusion: Orally deliverable and combinations of the FDA-approved drugs targeting the MIB pathway and the InAT axis cause optimum inhibition of colonic CSCs through downregulation of SREBP2, achieving maximal inhibition of the MIB pathway. Note: This abstract was not presented at the meeting. Citation Format: Chetna Sharon, Rio Boothello, Alberto Vera, Bhaumik B. Patel. A synergistic combination strategy for optimal inhibition of colon cancer stem cells: Simultaneous inhibition of Insulin-like growth factor-1 receptor-AKT-mammalian target of rapamycin axis and the mevalonate-isoprenoid biosynthetic pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4667.

GRP78 Regulates Apoptosis, Cell Survival and Proliferation in 5-Fluorouracil-resistant SNUC5 Colon Cancer Cells

5-Fluorouracil (5-FU) is an effective anticancer drug. However, the development of drug resistance has limited its chemotherapeutic efficacy. To address this problem, we investigated the expression of glucose-regulated protein (GRP78, 78 kDa) in 5-FU-resistant colorectal cancer (CRC) cells (SNUC5/5FUR). GRP78 was highly expressed in the SNUC5/5FUR cells compared to wild-type SNUC5 cells. In the presence of 5-FU, GRP78 knockdown induced apoptosis via activation of caspase-3 and poly(ADP-ribose)-polymerase 1. GRP78 also inhibited the production of intracellular reactive oxygen species by regulating stress-associated signaling pathways. Furthermore, GRP78 enhanced cell survival and proliferation via activation of the phosphatidylinosito-3-kinase-AKT-mammalian target of rapamycin axis and cell cycle-associated proteins. These effects were blocked upon GRP78 knockdown, which indicates that GRP78 is involved in the development of 5-FU resistance in these CRC cells. Therefore, a combination of chemotherapy and GRP78-specific targeting may counteract 5-FU resistance in CRC cells.

PTEN Down-Regulation Promotes β-Oxidation to Fuel Hypertrophic Liver Growth After Hepatectomy in Mice.

PTEN down-regulation after hepatectomy promotes the burning of TRAS-derived lipids to fuel hypertrophic liver regeneration. Therefore, the anabolic function of PTEN deficiency in resting liver is transformed into catabolic activities upon tissue loss. These findings portray PTEN as a node coordinating liver growth with its energy demands and emphasize the need of lipids for regeneration. (Hepatology 2017;66:908-921).

Plum polyphenols inhibit colorectal aberrant crypt foci formation in rats: potential role of the miR-143/protein kinase B/mammalian target of rapamycin axis

The nutritional prevention of aberrant crypt foci by polyphenols may be a crucial step to dietary cancer prevention. The objective of this study was to determine the underlying mechanisms that contribute to the anti-inflammatory and antitumorigenic properties of plum (Prunus salicina L.) polyphenols, including chlorogenic acid and neochlorogenic acid, in azoxymethane (AOM)-treated rats. The hypothesis was that plum polyphenolics suppress AOM-induced aberrant crypt foci formation through alterations in the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway and relative micro-RNA expressions. Sprague-Dawley rats (n=10/group) received plum beverage (1346mg gallic acid equivalents/L) or a control beverage ad libitum for 10 weeks with subcutaneous injections of AOM (15mg/kg) at weeks 2 and 3. Results show that the consumption of the plum beverage decreased the number of dysplastic aberrant crypt foci by 48% (P<.05) and lowered proliferation of mucosal cells by 24% (P<.05). The plum beverage decreased the activity of glutathione peroxidase, superoxide dismutase, and catalase in mucosal scrapings, as well as the superoxide dismutase activity in serum. The results were accompanied by a down-regulation of proinflammatory enzymes nuclear factor κB, nitric oxide synthase, cyclooxygenase-2, and vascular cell adhesion molecule 1 messenger RNA. Plum inhibited the expression of AKT and mTOR messenger RNA, phosphorylated AKT, mTOR, and hypoxia-inducible factor-1α protein levels, and the ratio of the phosphorylated/total protein expression of mTOR. Also, the plum beverage increased the expression of miR-143, which is involved in the regulation of AKT. These results suggest that plum polyphenols may exhibit a chemopreventive potential against colon carcinogenesis by impacting the AKT/mTOR pathway and miR-143.

Marchantin M: a novel inhibitor of proteasome induces autophagic cell death in prostate cancer cells

We previously reported that marchantin M (Mar) is an active agent to induce apoptosis in human prostate cancer (PCa), but the molecular mechanisms of action remain largely unknown. Here, we demonstrate that Mar potently inhibited chymotrypsin-like and peptidyl-glutamyl peptide-hydrolyzing activities of 20S proteasome both in in vitro and intracellular systems and significantly induced the accumulation of polyubiquitinated proteins in PCa cells. The computational modeling analysis suggested that Mar non-covalently bound to active sites of proteasome β5 and β1 subunits, resulting in a non-competitive inhibition. Proteasome inhibition by Mar subsequently resulted in endoplasmic reticulum (ER) stress, as evidenced by elevated glucose-regulated protein 78 and CHOP, increased phospho-eukaryotic translation initiation factor 2α (eIF2α), splicing of X-box-binding protein-1 and dilation of the ER. However, Mar-mediated cell death was not completely impaired by a pan inhibitor of caspases. Further studies revealed that the Mar-induced cell death was greatly associated with the activation of autophagy, as indicated by the significant induction of microtubule-associated protein-1 light chain-3 beta (LC3B) expression and conversion. Electron microscopic and green fluorescent protein-tagged LC3B analyses further demonstrated the ability of autophagy induction by Mar. Time kinetic studies revealed that Mar induced a rapid and highly sustained processing of LC3B in treated cells and simultaneously decreased the expression of p62/SQSTM1. Pharmacological blockade or knockdown of LC3B and Atg5 attenuated Mar-mediated cell death. The autophagic response triggered by Mar required the activation of RNA-dependent protein kinase-like ER kinase/eIF2α and suppression of the phosphatidylinositol-3 kinase/Akt/mammalian target of rapamycin axis via preventing activation and expression of Akt. Our results identified a novel mechanism for the cytotoxic effect of Mar, which strengthens it as a potential agent in cancer chemotherapy.

Heart Smart Insulin-Like Growth Factor 1

See related article, pp 680–693 The prevalence of obesity, metabolic syndrome, and type 2 diabetes mellitus, and the associated cardiac pathologies are rising to alarming levels. Conventional medical therapies for the prevention and treatment of cardiomyopathy are less effective in patients with these metabolic disorders, and this is attributed, at least in part, to a limited understanding of the cellular and genetic mechanisms responsible for the pathology in the heart. The cause(s) underlying the development of obesity and metabolic syndrome have been attributed to several factors including, but not limited to, consumption of a high-fat diet and are often associated with myocardial contractile and metabolic dysfunction.1 The detrimental effects of high-fat diets on the heart are likely to be multifactorial and include lipotoxicity, abnormal fatty acid metabolism, endothelial dysfunction, impaired calcium handling, mitochondrial dysfunction, and disruption of the insulin signaling pathway. Recent evidence also suggests that a high-fat diet induces epigenetic defects in the heart,2 which could potentially result in an increased risk of cardiac pathologies in offspring. A better understanding of the mechanisms underlying the increased propensity for high-fat diets to induce cardiac dysfunction is necessary to develop treatment strategies. Insulin-like growth factor-1 (IGF-1) plays a role in regulating cell proliferation, differentiation, survival, and metabolism and is produced in many tissues, including the heart. Reduced IGF-1 levels are associated with obesity, cardiovascular disease, atherosclerosis, and diabetes mellitus, whereas elevated IGF-1 has been associated with longevity in humans.3 …

Adaptor Proteins as Targets for Cancer Prevention

This perspective on the report by McCampbell et al. in this issue of the journal (beginning on page 290) addresses the role of insulin receptor substrate (IRS) proteins in cancer progression. The IRS proteins link many cell-surface receptors to signal transduction pathways. Activation of the phosphoinositide-3 kinase/Akt/mammalian target of rapamycin axis normally results in serine phosphorylation and subsequent downregulation of these adaptor proteins. The authors show that changes in the negative feedback regulation of IRS proteins is associated with the progression of endometrial epithelial cells to hyperplasia and cancer. Therefore, understanding the function of adaptor proteins could provide additional strategies for cancer prevention and treatment.