bims-lymeca 2023-08-13 papers

Issue of 2023‒08‒13
three papers selected by
Harilaos Filippakis
University of New England

Nat Cell Biol. 2023 Aug 10.

Malonyl-CoA is a conserved endogenous ATP-competitive mTORC1 inhibitor.

Raffaele Nicastro, Laura Brohée, Josephine Alba, Julian Nüchel, Gianluca Figlia, Stefanie Kipschull, Peter Gollwitzer, Jesus Romero-Pozuelo, Stephanie A Fernandes, Andreas Lamprakis, Stefano Vanni, Aurelio A Teleman, Claudio De Virgilio, Constantinos Demetriades.

Cell growth is regulated by the mammalian/mechanistic target of rapamycin complex 1 (mTORC1), which functions both as a nutrient sensor and a master controller of virtually all biosynthetic pathways. This ensures that cells are metabolically active only when conditions are optimal for growth. Notably, although mTORC1 is known to regulate fatty acid biosynthesis, how and whether the cellular lipid biosynthetic capacity signals back to fine-tune mTORC1 activity remains poorly understood. Here we show that mTORC1 senses the capacity of a cell to synthesise fatty acids by detecting the levels of malonyl-CoA, an intermediate of this biosynthetic pathway. We find that, in both yeast and mammalian cells, this regulation is direct, with malonyl-CoA binding to the mTOR catalytic pocket and acting as a specific ATP-competitive inhibitor. When fatty acid synthase (FASN) is downregulated/inhibited, elevated malonyl-CoA levels are channelled to proximal mTOR molecules that form direct protein-protein interactions with acetyl-CoA carboxylase 1 (ACC1) and FASN. Our findings represent a conserved and unique homeostatic mechanism whereby impaired fatty acid biogenesis leads to reduced mTORC1 activity to coordinately link this metabolic pathway to the overall cellular biosynthetic output. Moreover, they reveal the existence of a physiological metabolite that directly inhibits the activity of a signalling kinase in mammalian cells by competing with ATP for binding.

DOI: https://doi.org/10.1038/s41556-023-01198-6

Cancers (Basel). 2023 Jul 29. pii: 3868. [Epub ahead of print]15(15):

Extracellular Matrix Collagen I Differentially Regulates the Metabolic Plasticity of Pancreatic Ductal Adenocarcinoma Parenchymal Cell and Cancer Stem Cell.

Diana Tavares-Valente, Stefania Cannone, Maria Raffaella Greco, Tiago Miguel Amaral Carvalho, Fátima Baltazar, Odília Queirós, Gennaro Agrimi, Stephan J Reshkin, Rosa Angela Cardone.

Pancreatic ductal adenocarcinoma (PDAC) has a 5-year survival rate of less than 10 percent largely due to the intense fibrotic desmoplastic reaction, characterized by high levels of extracellular matrix (ECM) collagen I that constitutes a niche for a subset of cancer cells, the cancer stem cells (CSCs). Cancer cells undergo a complex metabolic adaptation characterized by changes in metabolic pathways and biosynthetic processes. The use of the 3D organotypic model in this study allowed us to manipulate the ECM constituents and mimic the progression of PDAC from an early tumor to an ever more advanced tumor stage. To understand the role of desmoplasia on the metabolism of PDAC parenchymal (CPC) and CSC populations, we studied their basic metabolic parameters in organotypic cultures of increasing collagen content to mimic in vivo conditions. We further measured the ability of the bioenergetic modulators (BMs), 2-deoxyglucose, dichloroacetate and phenformin, to modify their metabolic dependence and the therapeutic activity of paclitaxel albumin nanoparticles (NAB-PTX). While all the BMs decreased cell viability and increased cell death in all ECM types, a distinct, collagen I-dependent profile was observed in CSCs. As ECM collagen I content increased (e.g., more aggressive conditions), the CSCs switched from glucose to mostly glutamine metabolism. All three BMs synergistically potentiated the cytotoxicity of NAB-PTX in both cell lines, which, in CSCs, was collagen I-dependent and the strongest when treated with phenformin + NAB-PTX. Metabolic disruption in PDAC can be useful both as monotherapy or combined with conventional drugs to more efficiently block tumor growth.

Keywords: bioenergetic modulators; cancer stem cells; chemoresistance; collagen I; glutamine; pancreatic ductal adenocarcinoma; treatment; tumor microenvironment

DOI: https://doi.org/10.3390/cancers15153868

iScience. 2023 Aug 18. 26(8): 107408

Tomatidine targets ATF4-dependent signaling and induces ferroptosis to limit pancreatic cancer progression.

Debasmita Mukherjee, Srija Chakraborty, Lena Bercz, Liliana D'Alesio, Jessica Wedig, Molly A Torok, Timothy Pfau, Hannah Lathrop, Shrina Jasani, Abigail Guenther, Jake McGue, Daniel Adu-Ampratwum, James R Fuchs, Timothy L Frankel, Maciej Pietrzak, Stacey Culp, Anne M Strohecker, Aleksander Skardal, Thomas A Mace.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with high metastasis and therapeutic resistance. Activating transcription factor 4 (ATF4), a master regulator of cellular stress, is exploited by cancer cells to survive. Prior research and data reported provide evidence that high ATF4 expression correlates with worse overall survival in PDAC. Tomatidine, a natural steroidal alkaloid, is associated with inhibition of ATF4 signaling in multiple diseases. Here, we discovered that in vitro and in vivo tomatidine treatment of PDAC cells inhibits tumor growth. Tomatidine inhibited nuclear translocation of ATF4 and reduced the transcriptional binding of ATF4 with downstream promoters. Tomatidine enhanced gemcitabine chemosensitivity in 3D ECM-hydrogels and in vivo. Tomatidine treatment was associated with induction of ferroptosis signaling validated by increased lipid peroxidation, mitochondrial biogenesis, and decreased GPX4 expression in PDAC cells. This study highlights a possible therapeutic approach utilizing a plant-derived metabolite, tomatidine, to target ATF4 activity in PDAC.

Keywords: Cancer; Microenvironment; Therapeutics

DOI: https://doi.org/10.1016/j.isci.2023.107408