bims-mecami 2023-05-28 papers

Genes Dis. 2023 Mar;10(2): 447-456

The role of autophagy in regulating metabolism in the tumor microenvironment.

Panpan Zhang, Shanshan Cheng, Xiaonan Sheng, Huijuan Dai, Kang He, Yueyao Du.

Autophagy, as a special programmed cell death, is a critical degradative process that eliminates intracellular abnormal proteins or damage organelles to balance cell energy and favor cell metabolism with autophagy-related (ATG) proteins. Autophagy activation is being increasingly recognized as an essential hallmark in tumorigenesis through influencing the metabolism of stromal cells in the tumor microenvironment (TME) which comprises of tumor cells, cancer-associated fibroblasts (CAFs), cancer-associated endothelial cells (CAEs), immune cells and adipocytes. Tumor cells can reuse autophagy-involved recycling to maintain mitochondrial function and energy supply to meet the metabolic demand of their growth and proliferation. However, the mechanism through which autophagy can promote a crosstalk between tumor and stroma cells is not clear. Reprogramed metabolism is one of the main characteristics of TME leading to higher adaptability of tumor cells with diverse mechanisms. The activation of autophagy has expanded our understanding on the interaction between tumor metabolism and TME. The aim of this review is to report recent advances on the metabolic cross-talk between stromal cells and solid tumor cells induced by autophagy in TME and revealed potential therapeutic targets.

Keywords: Autophagy; Metabolism; Therapeutic targets; Tumor; Tumor microenvironment

DOI: https://doi.org/10.1016/j.gendis.2021.10.010

bioRxiv. 2023 May 09. pii: 2023.05.07.539744. [Epub ahead of print]

Anaplerotic nutrient stress drives synergy of angiogenesis inhibitors with therapeutics targeting tumor metabolism.

Tumor angiogenesis is a cancer hallmark, and its therapeutic inhibition has provided meaningful, albeit limited, clinical benefit. While anti-angiogenesis inhibitors deprive the tumor of oxygen and essential nutrients, cancer cells activate metabolic adaptations to diminish therapeutic response. Despite these adaptations, angiogenesis inhibition incurs extensive metabolic stress, prompting us to consider such metabolic stress as an induced vulnerability to therapies targeting cancer metabolism. Metabolomic profiling of angiogenesis-inhibited intracranial xenografts showed universal decrease in tricarboxylic acid cycle intermediates, corroborating a state of anaplerotic nutrient deficit or stress. Accordingly, we show strong synergy between angiogenesis inhibitors (Avastin, Tivozanib) and inhibitors of glycolysis or oxidative phosphorylation through exacerbation of anaplerotic nutrient stress in intracranial orthotopic xenografted gliomas. Our findings were recapitulated in GBM xenografts that do not have genetically predisposed metabolic vulnerabilities at baseline. Thus, our findings cement the central importance of the tricarboxylic acid cycle as the nexus of metabolic vulnerabilities and suggest clinical path hypothesis combining angiogenesis inhibitors with pharmacological cancer interventions targeting tumor metabolism for GBM tumors.

DOI: https://doi.org/10.1101/2023.05.07.539744

Nature. 2023 May 24.

Tumour extracellular vesicles and particles induce liver metabolic dysfunction.

Cancer alters the function of multiple organs beyond those targeted by metastasis1,2. Here we show that inflammation, fatty liver and dysregulated metabolism are hallmarks of systemically affected livers in mouse models and in patients with extrahepatic metastasis. We identified tumour-derived extracellular vesicles and particles (EVPs) as crucial mediators of cancer-induced hepatic reprogramming, which could be reversed by reducing tumour EVP secretion via depletion of Rab27a. All EVP subpopulations, exosomes and principally exomeres, could dysregulate hepatic function. The fatty acid cargo of tumour EVPs-particularly palmitic acid-induced secretion of tumour necrosis factor (TNF) by Kupffer cells, generating a pro-inflammatory microenvironment, suppressing fatty acid metabolism and oxidative phosphorylation, and promoting fatty liver formation. Notably, Kupffer cell ablation or TNF blockade markedly decreased tumour-induced fatty liver generation. Tumour implantation or pre-treatment with tumour EVPs diminished cytochrome P450 gene expression and attenuated drug metabolism in a TNF-dependent manner. We also observed fatty liver and decreased cytochrome P450 expression at diagnosis in tumour-free livers of patients with pancreatic cancer who later developed extrahepatic metastasis, highlighting the clinical relevance of our findings. Notably, tumour EVP education enhanced side effects of chemotherapy, including bone marrow suppression and cardiotoxicity, suggesting that metabolic reprogramming of the liver by tumour-derived EVPs may limit chemotherapy tolerance in patients with cancer. Our results reveal how tumour-derived EVPs dysregulate hepatic function and their targetable potential, alongside TNF inhibition, for preventing fatty liver formation and enhancing the efficacy of chemotherapy.

DOI: https://doi.org/10.1038/s41586-023-06114-4

Front Oncol. 2023 ;13 1175532

Lactate mediated metabolic crosstalk between cancer and immune cells and its therapeutic implications.

Seyedeh Sahar Mortazavi Farsani, Vivek Verma.

Metabolism is central to energy generation and cell signaling in all life forms. Cancer cells rely heavily on glucose metabolism wherein glucose is primarily converted to lactate even in adequate oxygen conditions, a process famously known as "the Warburg effect." In addition to cancer cells, Warburg effect was found to be operational in other cell types, including actively proliferating immune cells. According to current dogma, pyruvate is the end product of glycolysis that is converted into lactate in normal cells, particularly under hypoxic conditions. However, several recent observations suggest that the final product of glycolysis may be lactate, which is produced irrespective of oxygen concentrations. Traditionally, glucose-derived lactate can have three fates: it can be used as a fuel in the TCA cycle or lipid synthesis; it can be converted back into pyruvate in the cytosol that feeds into the mitochondrial TCA; or, at very high concentrations, accumulated lactate in the cytosol may be released from cells that act as an oncometabolite. In immune cells as well, glucose-derived lactate seems to play a major role in metabolism and cell signaling. However, immune cells are much more sensitive to lactate concentrations, as higher lactate levels have been found to inhibit immune cell function. Thus, tumor cell-derived lactate may serve as a major player in deciding the response and resistance to immune cell-directed therapies. In the current review, we will provide a comprehensive overview of the glycolytic process in eukaryotic cells with a special focus on the fate of pyruvate and lactate in tumor and immune cells. We will also review the evidence supporting the idea that lactate, not pyruvate, is the end product of glycolysis. In addition, we will discuss the impact of glucose-lactate-mediated cross-talk between tumor and immune cells on the therapeutic outcomes after immunotherapy.

Keywords: TCA cycle; Warburg effect; cancer; glycolysis; immunotherapy; lactate; metabolism; mitochondria

DOI: https://doi.org/10.3389/fonc.2023.1175532