Browsing by Subject "Rapamycin"
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Item Combination Therapy With Rapamycin and Low Dose Imatinib in Pulmonary Hypertension(Frontiers Media, 2021-11-11) Shi, Yinan; Gu, Chenxin; Zhao, Tongtong; Jia, Yangfan; Bao, Changlei; Luo, Ang; Guo, Qiang; Han, Ying; Wang, Jian; Black, Stephen M.; Desai, Ankit A.; Tang, Haiyang; Medicine, School of MedicineRationale: Enhanced proliferation and distal migration of human pulmonary arterial smooth muscle cells (hPASMCs) both contribute to the progressive increases in pulmonary vascular remodeling and resistance in pulmonary arterial hypertension (PAH). Our previous studies revealed that Rictor deletion, to disrupt mTOR Complex 2 (mTORC2), over longer periods result in a paradoxical rise in platelet-derived growth factor receptor (PDGFR) expression in PASMCs. Thus, the purpose of this study was to evaluate the role of combination therapy targeting both mTOR signaling with PDGFR inhibition to attenuate the development and progression of PAH. Methods and Results: Immunoblotting analyses revealed that short-term exposure to rapamycin (6h) significantly reduced phosphorylation of p70S6K (mTORC1-specific) in hPASMCs but had no effect on the phosphorylation of AKT (p-AKT S473, considered mTORC2-specific). In contrast, longer rapamycin exposure (>24 h), resulted in differential AKT (T308) and AKT (S473) phosphorylation with increases in phosphorylation of AKT at T308 and decreased phosphorylation at S473. Phosphorylation of both PDGFRα and PDGFRβ was increased in hPASMCs after treatment with rapamycin for 48 and 72 h. Based on co-immunoprecipitation studies, longer exposure to rapamycin (24-72 h) significantly inhibited the binding of mTOR to Rictor, mechanistically suggesting mTORC2 inhibition by rapamycin. Combined exposure of rapamycin with the PDGFR inhibitor, imatinib significantly reduced the proliferation and migration of hPASMCs compared to either agent alone. Pre-clinical studies validated increased therapeutic efficacy of rapamycin combined with imatinib in attenuating PAH over either drug alone. Specifically, combination therapy further attenuated the development of monocrotaline (MCT)- or Hypoxia/Sugen-induced pulmonary hypertension (PH) in rats as demonstrated by further reductions in the Fulton index, right ventricular systolic pressure (RVSP), pulmonary vascular wall thickness and vessel muscularization, and decreased proliferating cell nuclear antigen (PCNA) staining in PASMCs. Conclusion: Prolonged rapamycin treatment activates PDGFR signaling, in part, via mTORC2 inhibition. Combination therapy with rapamycin and imatinib may be a more effective strategy for the treatment of PAH.Item Global gene expression of histologically normal primary skin cells from BCNS subjects reveals "single-hit" effects that are influenced by rapamycin(Impact Journals, 2019-02-15) Phatak, Amruta; Athar, Mohammad; Crowell, James A.; Leffel, David; Herbert, Brittney-Shea; Bale, Allen E.; Kopelovich, Levy; Department of Medical and Molecular Genetics, Indiana University School of MedicineStudies of dominantly heritable cancers enabled insights about tumor progression. BCNS is a dominantly inherited disorder that is characterized by developmental abnormalities and postnatal neoplasms, principally BCCs. We performed an exploratory gene expression profiling of primary cell cultures derived from clinically unaffected skin biopsies of BCNS gene-carriers (PTCH1 +/-) and normal individuals. PCA and HC of untreated keratinocytes or fibroblasts failed to clearly distinguish BCNS samples from controls. These results are presumably due to the common suppression of canonical HH signaling in vitro. We then used a relaxed threshold (p-value <0.05, no FDR cut-off; FC 1.3) that identified a total of 585 and 857 genes differentially expressed in BCNS keratinocytes and fibroblasts samples, respectively. A GSEA identified pancreatic β cell hallmark and mTOR signaling genes in BCNS keratinocytes, whereas analyses of BCNS fibroblasts identified gene signatures regulating pluripotency of stem cells, including WNT pathway. Significantly, rapamycin treatment (FDR<0.05), affected a total of 1411 and 4959 genes in BCNS keratinocytes and BCNS fibroblasts, respectively. In contrast, rapamycin treatment affected a total of 3214 and 4797 genes in normal keratinocytes and normal fibroblasts, respectively. The differential response of BCNS cells to rapamycin involved 599 and 1463 unique probe sets in keratinocytes and fibroblasts, respectively. An IPA of these genes in the presence of rapamycin pointed to hepatic fibrosis/stellate cell activation, and HIPPO signaling in BCNS keratinocytes, whereas mitochondrial dysfunction and AGRN expression were uniquely enriched in BCNS fibroblasts. The gene expression changes seen here are likely involved in the etiology of BCCs and they may represent biomarkers/targets for early intervention.Item Integration of general amino acid control and TOR regulatory pathways in yeast(2010-05) Staschke, Kirk Alan; Wek, Ronald C.; Edenberg, Howard J.; Roach, Peter J.; Bard, MartinTwo important nutrient sensing and regulatory pathways, the general amino acid control (GAAC) and the target of rapamycin (TOR), participate in the control of yeast growth and metabolism in response to changes in nutrient availability. Starvation for amino acids activates the GAAC through Gcn2p phosphorylation of the translation initiation factor eIF2 and preferential translation of GCN4, a transcription activator. TOR senses nitrogen availability and regulates transcription factors, such as Gln3p. We used microarray analyses to address the integration of the GAAC and TOR pathways in directing the yeast transcriptome during amino acid starvation and rapamycin treatment. We found that the GAAC is a major effector of the TOR pathway, with Gcn4p and Gln3p each inducing a similar number of genes during rapamycin treatment. While Gcn4p activates a common core of 57 genes, the GAAC directs significant variations in the transcriptome during different stresses. In addition to inducing amino acid biosynthetic genes, Gcn4p activates genes required for assimilation of secondary nitrogen sources, such as -amino-butyric acid (GABA). Gcn2p activation upon shifting to secondary nitrogen sources is suggested to occur by means of a dual mechanism. First, Gcn2p is induced by the release of TOR repression through a mechanism involving Sit4p protein phosphatase. Second, this eIF2 kinase is activated by select uncharged tRNAs, which were shown to accumulate during the shift to GABA medium. This study highlights the mechanisms by which the GAAC and TOR pathways are integrated to recognize changing nitrogen availability and direct the transcriptome for optimal growth adaptation.Item Intravitreal sirolimus for persistent, exudative age-related macular degeneration: a Pilot Study(BMC, 2021-02-16) Minturn, Robert J.; Bracha, Peter; Klein, Margaret J.; Chhablani, Jay; Harless, Ashley M.; Maturi, Raj K.; Ophthalmology, School of MedicineBackground and objective: To evaluate the safety and efficacy of intravitreal sirolimus for persistent, exudative age-related macular degeneration (AMD). Methods: This institutional review board approved, registered (NCT02357342), prospective, subject-masked, single center, randomized controlled trial in subjects with persistent, exudative Age-related macular degeneration compared intravitreal sirolimus monotherapy (every 2 months) versus monthly anti-vascular endothelial growth factor (VEGF) over six months. Results: 20 subjects were randomized to each arm of the trial. Upon completion of the trial 20 patients were analyzed in the control (anti-vascular endothelial growth factor) group and 17 patients were analyzed in the treatment (sirolimus) group. On average, subjects had 33 previous anti-VEGF injections prior to entry. The primary end-point, mean central subfield thickness (CST), increased by 20 µm in the anti-vascular endothelial growth factor group and decreased by 40 µm in the sirolimus group (p = 0.03). Visual acuity outcomes were similar between groups. Serious ocular adverse events in the sirolimus group included one subject each with anterior uveitis, central retinal artery occlusion and subretinal hemorrhage. Conclusion: Monotherapy with intravitreal sirolimus for subjects with persistent, exudative age-related macular degeneration appears to have a limited positive anatomic benefit. The presence of adverse events in the experimental group merits further evaluation, potentially as an adjuvant therapy. Trial registration This trial was registered with the clinicaltrials.gov, NCT02357342, and was approved by the institutional review board at Advarra. Funding was provided by an investigator-initiated grant from Santen. Santen played no role in the design or implementation of this study.Item Intravitreal sirolimus with adjunct aflibercept versus aflibercept monotherapy for persistent, exudative age-related macular degeneration: a pilot study(BMC, 2023-01-05) Rowe, Lucas W.; Minturn, Robert J.; Burgett, Lauren A.; Bracha, Peter; Maturi, Raj K.; Ophthalmology, School of MedicineBackground: To determine the safety and efficacy of intravitreal sirolimus and adjunct aflibercept in subjects with persistent, exudative age-related macular degeneration despite previous intravitreal anti-vascular endothelial growth factor (VEGF) treatment. Methods: This institutional review board approved, registered (NCT02732899), prospective, subject-masked, single center, randomized controlled trial in subjects with persistent, exudative age-related macular degeneration compared alternating monthly intravitreal sirolimus and aflibercept (combination) versus aflibercept monotherapy (control) every 2 months over the course of 36 weeks. The primary measure of efficacy in the study was the mean change in central subfield thickness. Results: 20 subjects were enrolled in the study, with 10 subjects assigned to each treatment group. Subjects had an average of 38 previous anti-VEGF injections. Mean central subfield thickness decreased in the combination group by 54.0 μm compared to 0.1 μm in the control group (p = 0.28). Mean visual acuity improved in the combination group by 2.5 ETDRS letters versus 0.8 ETDRS letters in the control group (p = 0.42). There were no serious ocular adverse events in either group; however, there were three serious systemic events in the combination group, including hospitalizations due to pancreatitis, pneumonia, and worsening hypertension. Conclusion: There was no statistically significant difference in the mean central subfield thickness change between the combination and control groups. However, intravitreal sirolimus with adjunct aflibercept did appear to have potential anatomical benefits as a treatment for persistent, exudative age-related macular degeneration and requires further investigation with a larger cohort to better understand the potential risks and benefits.Item Loss of mTORC1 signalling impairs β-cell homeostasis and insulin processing(Nature Communication Group, 2017-07-12) Blandino-Rosano, Manuel; Barbaresso, Rebecca; Jimenez-Palomares, Margarita; Bozadjieva, Nadejda; Werneck-de-Castro, Joao Pedro; Hatanaka, Masayuki; Mirmira, Raghavendra G.; Sonenberg, Nahum; Liu, Ming; Rüegg, Markus A.; Hall, Michael N.; Bernal-Mizrachi, Ernesto; Pediatrics, School of MedicineDeregulation of mTOR complex 1 (mTORC1) signalling increases the risk for metabolic diseases, including type 2 diabetes. Here we show that β-cell-specific loss of mTORC1 causes diabetes and β-cell failure due to defects in proliferation, autophagy, apoptosis and insulin secretion by using mice with conditional (βraKO) and inducible (MIP-βraKOf/f) raptor deletion. Through genetic reconstitution of mTORC1 downstream targets, we identify mTORC1/S6K pathway as the mechanism by which mTORC1 regulates β-cell apoptosis, size and autophagy, whereas mTORC1/4E-BP2-eIF4E pathway regulates β-cell proliferation. Restoration of both pathways partially recovers β-cell mass and hyperglycaemia. This study also demonstrates a central role of mTORC1 in controlling insulin processing by regulating cap-dependent translation of carboxypeptidase E in a 4EBP2/eIF4E-dependent manner. Rapamycin treatment decreases CPE expression and insulin secretion in mice and human islets. We suggest an important role of mTORC1 in β-cells and identify downstream pathways driving β-cell mass, function and insulin processing.Item mTOR regulates Aurora A via enhancing protein stability(2013-12) Fan, Li; Quilliam, Lawrence; Atkinson, Simon; Goebl, Mark G.; Harrington, Maureen A.; Wek, Ronald C.Mammalian target of rapamycin (mTOR) is a key regulator of protein synthesis. Dysregulation of mTOR signaling occurs in many human cancers and its inhibition causes arrest at the G1 cell cycle stage. However, mTOR’s impact on mitosis (M-phase) is less clear. Here, suppressing mTOR activity impacted the G2-M transition and reduced levels of M-phase kinase, Aurora A. mTOR inhibitors did not affect Aurora A mRNA levels. However, translational reporter constructs showed that mRNA containing a short, simple 5’-untranslated region (UTR), rather than a complex structure, is more responsive to mTOR inhibition. mTOR inhibitors decreased Aurora A protein amount whereas blocking proteasomal degradation rescues this phenomenon, revealing that mTOR affects Aurora A protein stability. Inhibition of protein phosphatase, PP2A, a known mTOR substrate and Aurora A partner, restored mTOR-mediated Aurora A abundance. Finally, a non-phosphorylatable Aurora A mutant was more sensitive to destruction in the presence of mTOR inhibitor. These data strongly support the notion that mTOR controls Aurora A destruction by inactivating PP2A and elevating the phosphorylation level of Ser51 in the “activation-box” of Aurora A, which dictates its sensitivity to proteasomal degradation. In summary, this study is the first to demonstrate that mTOR signaling regulates Aurora-A protein expression and stability and provides a better understanding of how mTOR regulates mitotic kinase expression and coordinates cell cycle progression. The involvement of mTOR signaling in the regulation of cell migration by its upstream activator, Rheb, was also examined. Knockdown of Rheb was found to promote F-actin reorganization and was associated with Rac1 activation and increased migration of glioma cells. Suppression of Rheb promoted platelet-derived growth factor receptor (PDGFR) expression. Pharmacological inhibition of PDGFR blocked these events. Therefore, Rheb appears to suppress tumor cell migration by inhibiting expression of growth factor receptors that in turn drive Rac1-mediate actin polymerization.Item mTORC1 contributes to ER stress induced cell death(2012-12) Babcock, Justin Thomas; Quilliam, Lawrence; Atkinson, Simon; Nakshatri, Harikrishna; Wek, Ronald C.Patients with the genetic disorder tuberous sclerosis complex (TSC) suffer from neoplastic growths in multiple organ systems. These growths are the result of inactivating mutations in either the TSC1 or TSC2 tumor suppressor genes, which negatively regulate the activity of mammalian target of rapamycin complex 1(mTORC1). There is currently no cure for this disease; however, my research has found that cells harboring TSC2-inactivating mutations derived from a rat model of TSC are sensitive to apoptosis induced by the clinically approved proteasome inhibitor, bortezomib, in a manner dependent on their high levels of mTORC1 activation. We see that bortezomib induces the unfolded protein response (UPR) in our cell model of TSC, resulting in cell death via apoptosis. The UPR is induced by accumulation of unfolded protein in the endoplasmic reticulum (ER) which activates the three branches of this pathway: Activating transcription factor 6 (ATF6) cleavage, phosphorylation of eukaryotic initiation factor 2α (eIF2α), and the splicing of X-box binding protein1 (XBP1) mRNA. Phosphorylation of eIF2α leads to global inhibition of protein synthesis, preventing more unfolded protein from accumulating in the ER. This phosphorylation also induces the transcription and translation of ATF4 and CCAAT-enhancer binding protein homologous protein (CHOP). Blocking mTORC1 activity in these cells using the mTORC1 inhibitor, rapamycin, prevented the expression of ATF4 and CHOP at both the mRNA and protein level during bortezomib treatment. Rapamycin treatment also reduced apoptosis induced by bortezomib; however, it did not affect bortezomib-induced eIF2α phosphorylation or ATF6 cleavage. These data indicate that rapamycin can repress the induction of UPR-dependent apoptosis by suppressing the transcription of ATF4 and CHOP mRNAs. In addition to these findings, we find that a TSC2-null angiomyolipoma cell line forms vacuoles when treated with the proteasome inhibitor MG-132. We found these vacuoles to be derived from the ER and that rapamycin blocked their formation. Rapamycin also enhanced expansion of the ER during MG-132 stress and restored its degradation by autophagy. Taken together these findings suggest that bortezomib might be used to treat neoplastic growths associated with TSC. However, they also caution against combining specific cell death inducing agents with rapamycin during chemotherapy.Item Nonlinear Population Pharmacokinetics of Sirolimus in Patients With Advanced Cancer(Wiley, 2012-12-05) Wu, K.; Cohen, E. E. W.; House, L. K.; Ramírez, J.; Zhang, W.; Ratain, M. J.; Bies, R. R.; Medicine, School of MedicineSirolimus, the prototypical inhibitor of the mammalian target of rapamycin, has substantial antitumor activity. In this study, sirolimus showed nonlinear pharmacokinetic characteristics over a wide dose range (from 1 to 60 mg/week). The objective of this study was to develop a population pharmacokinetic (PopPK) model to describe the nonlinearity of sirolimus. Whole blood concentration data, obtained from four phase I clinical trials, were analyzed using a nonlinear mixed-effects modeling (NONMEM) approach. The influence of potential covariates was evaluated. Model robustness was assessed using nonparametric bootstrap and visual predictive check approaches. The data were well described by a two-compartment model incorporating a saturable Michaelis-Menten kinetic absorption process. A covariate analysis identified hematocrit as influencing the oral clearance of sirolimus. The visual predictive check indicated that the final pharmacokinetic model adequately predicted observed concentrations. The pharmacokinetics of sirolimus, based on whole blood concentrations, appears to be nonlinear due to saturable absorption.Item The role of acid sphingomyelinase in autophagy(2014-07-11) Justice, Matthew Jose; Petrache, Irina; Blum, Janice Sherry, 1957-; Wek, Ronald C.Autophagy is a conserved cellular process that involves sequestration and degradation of cytosolic contents. The cell can engulf autophagic cargo (lipids, long-lived proteins, protein aggregates, and pathogens) through a double bound membrane called an autophagosome that fuses with a lysosome where hydrolases then degrade these contents. This process is one of the main defenses against starvation and is imperative for newborns at birth. Research on this process has increased exponentially in the last decade since its discovery almost a half a century ago. It has been found that autophagy is an important process in many diseases, continues to be at the forefront of research, and is clearly not fully understood. Our preliminary cell culture data in endothelial and epithelial cells show that a blockade of the de novo ceramide synthesis pathway, during treatment with an autophagy stimulus (cigarette smoke extract exposure), does not result in any reduction in autophagy or autophagic flux. Conversely, when acid sphingomyelinase (ASM) is pharmacologically inhibited, which prevents the generation of ceramide from sphingomyelin in an acidic environment, a profound increase in autophagy is observed. In this work, we hypothesize that (ASM) is an endogenous inhibitor of autophagy. ASM has two forms, a secreted form and a lysosomal form. N-terminal processing in the Golgi determines its cellular fate. In the lysosomal form, the phosphodiesterase is bound in the lysosomal membrane. The pharmacological inhibition mechanism is to release ASM from the membrane and allow other hydrolases to actively degrade the enzyme which, in turn, decreases the activity of ASM. This suggests that either the activity of ASM is a regulator of autophagy or that the presence of ASM, activity aside, is required for the lysosomal nutrient sensing machinery (LYNUS) to function properly. Here, we show that ASM is, in fact, an endogenous inhibitor of autophagy in vitro. The phosphorylation status of P70 S6k, a downstream effector of mammalian target of rapamycin (mTOR), which is part of the LYNUS, shows that dissociation of ASM from the membrane regulates mTOR and disturbs the LYNUS in such a manner as to signal autophagy.