Metabolic adaptations in spontaneously immortalized PGC-1α knock-out mouse embryonic fibroblasts increase their oncogenic potential

Abstract

PGC-1α controls, to a large extent, the capacity of cells to respond to changing nutritional requirements and energetic demands. The key role of metabolic reprogramming in tumor development has highlighted the potential role of PGC-1α in cancer. To investigate how loss of PGC-1α activity in primary cells impacts the oncogenic characteristics of spontaneously immortalized cells, and the mechanisms involved, we used the classic 3T3 protocol to generate spontaneously immortalized mouse embryonic fibroblasts (iMEFs) from wild-type (WT) and PGC-1α knockout (KO) mice and analyzed their oncogenic potential in vivo and in vitro. We found that PGC-1α KO iMEFs formed larger and more proliferative primary tumors than WT counterparts, and fostered the formation of lung metastasis by B16 melanoma cells. These characteristics were associated with the reduced capacity of KO iMEFs to respond to cell contact inhibition, in addition to an increased ability to form colonies in soft agar, an enhanced migratory capacity, and a reduced growth factor dependence. The mechanistic basis of this phenotype is likely associated with the observed higher levels of nuclear β-catenin and c-myc in KO iMEFs. Evaluation of the metabolic adaptations of the immortalized cell lines identified a decrease in oxidative metabolism and an increase in glycolytic flux in KO iMEFs, which were also more dependent on glutamine for their survival. Furthermore, glucose oxidation and tricarboxylic acid cycle forward flux were reduced in KO iMEF, resulting in the induction of compensatory anaplerotic pathways. Indeed, analysis of amino acid and lipid patterns supported the efficient use of tricarboxylic acid cycle intermediates to synthesize lipids and proteins to support elevated cell growth rates. All these characteristics have been observed in aggressive tumors and support a tumor suppressor role for PGC-1α, restraining metabolic adaptations in cancer.

Evaluation of Mitochondrial Function in Blood Samples Shows Distinct Patterns in Subjects with Thyroid Carcinoma from Those with Hyperplasia

“…We next determined the number of proliferating cells in thyroid samples by immunochemical staining with an antibody against Ki67 [30]. As expected, we found significant differences in the number of proliferating cells between peripheral and central tissue samples; however, no significant differences were found in Ki67-positive cells between carcinoma and hyperplasia samples, although there was a trend for a greater number of Ki67positive cells in the former in the two cohorts (Fig.…”

20(s)‑ginseonside‑Rg3 modulation of AMPK/FoxO3 signaling to attenuate mitochondrial dysfunction in a dexamethasone‑injured C2C12 myotube‑based model of skeletal atrophy in vitro

“…Mitochondria function as the main energy-producing organelles in cells, with mitochondrial functional disturbances leading to insufficient energy supply and activation of intracellular signaling pathways that culminates in AMPK activation, apoptosis and/or autophagy ( 50 , 51 ). Notably, intracellular ATP deprivation triggers immediate activation of AMPK, an important energy sensor, that subsequently causes mitochondrial biogenesis (via PGC-1α phosphorylation) or autophagy (via ULK1 phosphorylation) ( 52 ). As demonstrated in previous studies, AMPK participates in muscle atrophy in two ways, by phosphorylating FoxO3 and thereby directly controlling its nuclear translocation ( 53 ) and by participating in AMPK/FoxO3 pathway signaling triggered by mitochondrial fission ( 54 ).…”

The Sall2 transcription factor promotes cell migration regulating focal adhesion turnover and integrin β1 expression

“…Mesenchymal cells move slowly, exhibit multiple protrusions, and depend strongly on integrin-mediated adhesions to the extracellular matrix ( Panková et al, 2010 ; Bear et al, 2014 ). Here, we used immortalized MEFs, which are widely helpful in assessing migratory and invasive capacities ( Birch et al, 2016 ; Prieto et al, 2020 ). These cells are a simple genetic model characterized mainly by the inactivation of p53 and Rb proteins ( Ali and DeCaprio, 2001 ).…”