How is the mTOR pathway measured?
A research-focused overview of how mTOR pathway activity is assessed across in vitro, animal and clinical models, drawing on transcriptomic, metabolomic, pharmacological and trial-based evidence.
How is the mTOR pathway measured?
The mechanistic target of rapamycin (mTOR) is a serine/threonine protein kinase of the phosphatidylinositol 3-kinase-related kinase family, encoded in humans by the gene MTOR. It is also known as FK506-binding protein 12-rapamycin-associated protein 1 (FRAP1), RAFT1, and RAPT1. The UniProt identifier for the human protein is P42345; the reference sequence is NP_004949.4. The mature protein has a calculated molecular mass of approximately 289 kDa and 2549 amino acids. mTOR exists in two structurally and functionally distinct complexes: mTOR complex 1 (mTORC1), which contains Raptor, and mTOR complex 2 (mTORC2), which contains Rictor. The pathway is most commonly interrogated in the context of the PI3K/AKT/mTOR signalling axis, a central regulator of cell growth, proliferation, metabolism and survival.
Measurement of mTOR pathway activity is not a single assay but a set of approaches that differ by model system, tissue and the specific node of the pathway under investigation. These include transcriptomic profiling of pathway components, targeted quantification of phosphorylated substrates such as p70S6K and 4E-BP1, metabolomic readouts of downstream metabolic effects, and pharmacological perturbation with activators or inhibitors. The sections below summarise how the pathway has been measured in specific research studies.
Research Studies
LL-37 and SQLE-mediated cholesterol synthesis via PTEN/AKT/mTOR in osteosarcoma cells
In an in vitro study using osteosarcoma (OS) cell lines and normal human bone marrow mesenchymal stem cells (hBMSCs), LL-37 (the human cathelicidin peptide) was investigated for its anti-OS activity and underlying mechanisms. The study employed transcriptomic profiling, siRNA-mediated knockdown, and assays for cell viability, clonogenic survival, migration, invasion, cell cycle distribution, cell death and cholesterol metabolism. The findings indicated that LL-37 inhibits osteosarcoma progression by suppressing SQLE-mediated cholesterol synthesis via the PTEN/AKT/mTOR pathway [1]. This work measured mTOR pathway involvement through transcriptomic changes and functional readouts in a human cell line model, not in animals or humans.
Intramuscular fat deposition and mTOR pathway transcripts in Yanbian yellow cattle
An integrated transcriptomics and non-targeted metabolomics study examined intramuscular fat (IMF) deposition in 60 24-month-old Yanbian yellow cattle (n = 30 per group), categorised into high-IMF (HM) and low-IMF (LM) groups. The analysis revealed a dual-layered regulatory framework: an upstream signalling layer comprising PPAR, PI3K-Akt and mTOR pathways, and a downstream metabolic execution layer involving lysine degradation and other metabolic routes [2]. Here, mTOR pathway activity was inferred from transcriptomic data in bovine skeletal muscle tissue, with no direct kinase activity assays reported.
Fingolimod and RhoA/mTOR pathways in kidney transplant fibrosis
A randomised, double-blind, placebo-controlled trial (NCT05285878) is testing whether fingolimod (FTY720) added to standard immunosuppression prevents expansion of the interstitial compartment in de novo kidney transplant recipients. The study hypothesis explicitly states that abrogating the fibrogenic effects of both the RhoA and mTOR pathways with fingolimod will reduce structural damage in transplanted kidneys and possible subsequent transplant failure [4]. In this clinical trial context, mTOR pathway activity is not directly measured as a biochemical endpoint; rather, the trial tests whether a drug with known effects on these pathways alters a histological outcome.
Alpha ketoglutarate and inflammatory responsiveness in colorectal surgery
The RISIS-CR trial (NCT06646809) proposes to identify inflammatory responsiveness in patients prior to colorectal cancer (CRC) surgery and administer prophylactic anti-inflammatory treatment targeted only to those with an excessive pro-inflammatory response. The study rationale notes that geroprotectors reduce inflammation and may reduce postoperative systemic inflammatory response (SIR) and complications after CRC surgery, and that alpha ketoglutarate (AKG) is a geroprotector supplement under investigation [3]. While the trial does not directly measure mTOR pathway activity, AKG is a metabolite that intersects with mTOR signalling, and the trial design illustrates how pathway-adjacent interventions are evaluated in a clinical population.
lncRNA DANCR and the miR-19a-3p/PTEN/AKT/mTOR axis in BMSC osteogenic differentiation
A study investigated the role of long non-coding RNA DANCR in osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and its underlying mechanisms. BMSCs were intervened with sh-DANCR, and the work examined the miR-19a-3p/PTEN/AKT/mTOR pathway [5]. This is an in vitro study using human BMSCs; mTOR pathway activity was assessed through molecular changes in the PTEN/AKT/mTOR axis following DANCR knockdown.
Anlotinib and c-MET/AKT/mTOR signalling in glioma cells
An in vitro study examined the direct antitumor effects of anlotinib in human glioma cells and whether these effects were associated with hepatocyte growth factor receptor (c-MET)/protein kinase B (AKT)/mTOR signalling and altered autophagy-associated protein expression. The study reported that anlotinib inhibits glioma cell proliferation, migration and invasion by suppressing c-MET/AKT/mTOR signalling [6]. Measurement here relied on cell-based assays of proliferation, migration and invasion, combined with protein-level analysis of the pathway.
Pharmacological mTOR activation and trophectoderm differentiation in bovine embryos
A study in bovine embryos examined whether pharmacological activation of the mTOR pathway enhances trophectoderm (TE) differentiation. While in mice the mTOR pathway influences the Hippo pathway and TE-related gene expression, these mechanisms are not fully characterised in bovine embryos. The study reported that pharmacological mTOR pathway activation does not enhance trophectoderm differentiation in bovine embryos [7]. This work used an embryo model and pharmacological tools to probe pathway function, with differentiation outcomes as the measured endpoint.
Mitochondria-enriched BMSC exosomes and PI3K/Akt/mTOR in Parkinson's disease models
A study engineered mitochondrial-enriched small extracellular vesicles (Exo-Mito) from bone marrow mesenchymal stem cells (BMSCs) to address mitochondrial dysfunction and neuroinflammation in Parkinson's disease (PD). The work reported that these exosomes restore microglia-neuron cross-talk via PINK1/parkin and PI3K/Akt/mTOR pathways [8]. This is a preclinical study; mTOR pathway involvement was assessed through molecular signalling changes in disease models, not in human patients.
Comparison of measurement approaches
| Study | Model | mTOR measurement approach | Key pathway node |
|---|---|---|---|
| LL-37 in osteosarcoma [1] | Human OS cell lines and hBMSCs (in vitro) | Transcriptomic profiling, siRNA knockdown, functional assays | PTEN/AKT/mTOR |
| Intramuscular fat in cattle [2] | Yanbian yellow cattle (in vivo) | Integrated transcriptomics and non-targeted metabolomics | PI3K-Akt and mTOR pathways |
| Fingolimod in kidney transplant [4] | Human kidney transplant recipients (clinical trial) | Histological outcome; pathway inferred from drug mechanism | RhoA and mTOR pathways |
| AKG in colorectal surgery [3] | Human CRC surgery patients (clinical trial) | Inflammatory response markers; pathway-adjacent | Not directly measured |
| lncRNA DANCR in BMSCs [5] | Human BMSCs (in vitro) | Molecular changes in PTEN/AKT/mTOR axis | miR-19a-3p/PTEN/AKT/mTOR |
| Anlotinib in glioma [6] | Human glioma cells (in vitro) | Cell proliferation, migration, invasion; protein analysis | c-MET/AKT/mTOR |
| mTOR activation in bovine embryos [7] | Bovine embryos (in vitro) | Pharmacological activation; differentiation outcomes | mTOR pathway |
| Exo-Mito in Parkinson's disease [8] | Preclinical PD models | Molecular signalling changes | PINK1/parkin and PI3K/Akt/mTOR |
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Sources
- [1] LL-37 inhibits osteosarcoma progression by suppressing SQLE-mediated cholesterol synthesis via the PTEN/AKT/mTOR pathway
- [2] Integrated transcriptomics and metabolomics reveal the molecular mechanisms of intramuscular fat deposition in Yanbian yellow cattle
- [3] Reducing Inflammatory Syndrome in Surgery - Colorectal (RISIS-CR) Trial
- [4] Fingolimod for the Abrogation of Interstitial Fibrosis and Tubular Atrophy Following Kidney Transplantation
- [5] Regulatory role of lncRNA DANCR in osteogenic differentiation of bone marrow mesenchymal stem cells through targeting the miR-19a-3p/PTEN/AKT/mTOR pathway
- [6] Anlotinib inhibits glioma cell proliferation, migration, and invasion by suppressing c-MET/AKT/mTOR signaling and altering autophagy-associated protein expression
- [7] Pharmacological mTOR pathway activation does not enhance trophectoderm differentiation in bovine embryos
- [8] Mitochondria-enriched BMSC exosomes restore microglia-neuron cross-talk in Parkinson's disease via PINK1/parkin and PI3K/Akt/mTOR pathways