Pyruvate carboxylase promotes thyroid cancer aggressiveness through fatty acid synthesis

Abstract

Background Pyruvate carboxylase (PC) is an important anaplerotic enzyme in the tricarboxylic acid cycle (TCA) in cancer cells. Although PC overexpression has been observed in thyroid cancer (TC), the mechanisms involved in the carcinogenic effects of PC are still unclear. Methods Bioinformatics analysis and clinical specimens were used to analyze the relationship of PC expression with clinicopathological variables in TC. Fatty acid synthesis was monitored by LC/MS, Nile red staining, and triglyceride analysis. Mitochondrial oxygen consumption was evaluated by the Seahorse XF Mito Cell Stress Test. The correlation of PC with FASN and SREBP1c was assessed by qRT-PCR and IHC in 38 human TC tissues. Western blotting was used to evaluate the protein expression of PC, FASN, and SREBP1c and members of the AKT/mTOR and EMT pathways in TC cell lines. Wound-healing, CCK-8, and Transwell assays and a nude mouse xenograft model were used to verify the regulatory effects of PC and SREBP1c on thyroid tumor cell proliferation, migration and invasion. Results We demonstrated that PC increased fatty acid synthesis, which then promoted TC progression and metastasis. Analysis of GEO data showed that the overexpression of PC in papillary thyroid cancer (PTC) was associated with PTC invasion and the fatty acid synthesis pathway. Analysis of clinical tissue specimens from PTC patients revealed that PC was more highly expressed in specimens from PTC patients with lymph node metastasis than in those from patients without metastasis. Multiple genes in the fatty acid synthesis signaling pathway, including FASN and SREBP1c, were downregulated in PC-knockdown TC cells compared to control cells. Lipid levels were also decreased in the PC-knockdown TC cells. Moreover, the ability of cells to grow, invade, and metastasize was also suppressed upon PC knockdown, suggesting that PC-mediated lipogenesis activation increases the aggressiveness of TC cells. In addition, PC was found to activate the AKT/mTOR pathway, thus improving FASN-mediated de novo lipogenesis in TC cells by upregulating SREBP1c expression. Studies in a nude mouse xenograft model showed that PC knockdown decreased tumor weight, but this effect was attenuated by forced expression of SREBP1c. Conclusions Our results demonstrate that PC is strongly involved in the tumor aggressiveness of TC via its stimulation of fatty acid synthesis.

LINC00092 Modulates Oxidative Stress and Glycolysis of Breast Cancer Cells via Pyruvate Carboxylase-Mediated AKT/mTOR Pathway

“…Moreover, PC was discovered to promote BC metastasis [ 59 , 62 ]. Liu et al [ 63 ] reported that PC could activate the AKT/mTOR pathway in thyroid cancer cells. In the last few years, some literatures have reported the regulatory role of lncRNAs in PC expression in cancer cells [ 64 , 65 ].…”

CRISPR Cas9-mediated ablation of pyruvate carboxylase gene in colon cancer cell line HT-29 inhibits growth and migration, induces apoptosis and increases sensitivity to 5-fluorouracil and glutaminase inhibitor

“…Using the HT-29 colon cell line to represent a highly invasive CRC cell line in vivo ( 31 ), we showed that PC KO HT-29 cell lines displayed a marked reduction of proliferation throughout the whole time-course of the assay. This phenotypic defect was similarly reported in PC-deficient cancers such as glioblastoma ( 18 ), MDA-MB-231 breast cancer ( 16 ), non-small cell lung cancer ( 14 ), papilloma thyroid carcinoma ( 19 , 32 ), and ovarian cancer ( 33 ). The marked increase of apoptotic cells and PARP cleavage indicates that apoptosis is at least in part responsible for the growth inhibition of PC KO HT-29 cells.…”

“…The decrease in lipid synthesis can potentially affect these structures, limiting the motility of cancer cells (39, 40). Liu et al (32) have recently reported that the PC knockdown-papillary thyroid cancer lines, PTC1, also showed a marked decrease of cell motility accompanied by reduced fatty acid synthesis and downregulation of expression of FASN but not ACC1. Although the reduction of FASN expression was associated with decreased expression of SREBP1c, a transcriptional regulator of the FASN gene, it is still unclear how depletion of oxaloacetate results in down-regulation of SREBP1c expression in PC knockdown PTC1 cells.…”

The Epithelial–Mesenchymal Transition at the Crossroads between Metabolism and Tumor Progression

“…An increase in FA levels was observed as a further consequence of PC upregulation in PTC associated with tumor progression. In particular, PC induces the Akt/mTOR signaling pathway, thus, upregulating SREBP1c, which, in turn, upregulates FASN and, consequently, lipogenesis and EMT ( Figure 4 ) [ 198 ]. PC ↑ ⇒ SREBPc ↑ ⇒ FASN ↑ ⇒ FAs↑ ⇒ ZEB1, SNAIL ↑ ⇒ EMT …”