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Updated: Dec 1, 2025
Study of Protein-protein Interactions in Autophagy Research
Published on: September 9, 2017
Assessing methods to quantitatively validate TGFβ-dependent autophagy
Charles B Trelford1, Gianni M Di Guglielmo2
1Schulich School of Medicine and Dentistry, Western University, Department of Physiology and Pharmacology, London, Ontario, Canada N6A 5B7.
Abstract:
Transforming growth factor beta (TGFβ) promotes tumorigenesis by suppressing immune surveillance and inducing epithelial to mesenchymal transition (EMT). TGFβ may augment tumorigenesis by activating autophagy, which protects cancer cells from chemotherapy and promotes invasive and anti-apoptotic properties. Here, we assess how TGFβ1 modulates autophagy related (ATG) gene expression and ATG protein levels. We also assessed microtubule-associated protein light chain 3 (LC3) lipidation, LC3 puncta formation and autophagosome-lysosome co-localization in non-small cell lung cancer (NSCLC) cell lines. These experimental approaches were validated using pharmacological autophagy inhibitors (chloroquine and spautin-1) and an autophagy activator (MG132). We found that TGFβ1, chloroquine and MG132 had little effect on ATG protein levels but increased LC3 lipidation, LC3 puncta formation and autophagosome-lysosome co-localization. Since similar outcomes were observed using chloroquine and MG132, we concluded that several techniques employed to assess TGFβ-dependent autophagy may not differentiate between the activation of autophagy versus lysosomal inhibition. Thus, NSCLC cell lines stably expressing a GFP-LC3-RFP-LC3ΔG autophagic flux probe were used to assess TGFβ-mediated autophagy. Using this approach, we observed that TGFβ, MG132 and serum starvation increased autophagic flux, whereas chloroquine and spautin-1 decreased autophagic flux. Finally, we demonstrated that ATG5 and ATG7 are critical for TGFβ-dependent autophagy in NSCLC cells. The application of this model will fuel future experiments to characterize TGFβ-dependent autophagy, which is necessary to understand the molecular processes that link, TGFβ, autophagy and tumorigenesis.
Insights
Transforming growth factor beta (TGFβ) activates autophagy in non-small cell lung cancer (NSCLC) cells, promoting tumor growth. ATG5 and ATG7 are crucial for this TGFβ-dependent autophagy, offering potential therapeutic targets.
Area of Science:
- Oncology
- Cell Biology
- Molecular Biology
Background:
- Transforming growth factor beta (TGFβ) is implicated in tumorigenesis by inhibiting immune surveillance and promoting epithelial-mesenchymal transition (EMT).
- TGFβ may enhance tumor progression by activating autophagy, conferring chemoresistance and promoting invasive, anti-apoptotic properties in cancer cells.
Purpose of the Study:
- To investigate how TGFβ1 influences autophagy-related (ATG) gene expression and protein levels in non-small cell lung cancer (NSCLC) cells.
- To evaluate the impact of TGFβ1 on key autophagy markers, including LC3 lipidation, LC3 puncta formation, and autophagosome-lysosome co-localization.
- To elucidate the role of specific ATG proteins in TGFβ-mediated autophagy in NSCLC.
Main Methods:
- Assessed ATG gene expression and protein levels in response to TGFβ1.
- Utilized LC3 lipidation assays, LC3 puncta imaging, and autophagosome-lysosome co-localization studies.
- Employed pharmacological autophagy modulators (chloroquine, spautin-1, MG132) and validated autophagy flux using a GFP-LC3-RFP-LC3ΔG probe in NSCLC cell lines.
- Investigated the necessity of ATG5 and ATG7 for TGFβ-dependent autophagy.
Main Results:
- TGFβ1, chloroquine, and MG132 increased LC3 lipidation and puncta formation, but not ATG protein levels, suggesting potential limitations in differentiating autophagy activation from lysosomal inhibition with these methods alone.
- Autophagic flux analysis revealed that TGFβ1, MG132, and serum starvation enhanced flux, while chloroquine and spautin-1 inhibited it.
- Demonstrated that ATG5 and ATG7 are essential for TGFβ-dependent autophagy in NSCLC cells.
Conclusions:
- Standard autophagy assessment methods may not reliably distinguish between autophagy activation and lysosomal inhibition.
- TGFβ1 actively modulates autophagic flux in NSCLC cells.
- ATG5 and ATG7 play critical roles in TGFβ-driven autophagy, representing potential targets for therapeutic strategies against NSCLC.
