Phorbol Esters Rapidly Attenuate Glutamine Uptake and Growth in Human Colon Carcinoma Cells (original) (raw)

Glutamine Transport and Mitochondrial Metabolism in Cancer Cell Growth

Frontiers in Oncology

The concept that cancer is a metabolic disease is now well acknowledged: many cancer cell types rely mostly on glucose and some amino acids, especially glutamine for energy supply. These findings were corroborated by overexpression of plasma membrane nutrient transporters, such as the glucose transporters (GLUTs) and some amino acid transporters such as ASCT2, LAT1, and ATB 0,+ , which became promising targets for pharmacological intervention. On the basis of their sodium-dependent transport modes, ASCT2 and ATB0 + have the capacity to sustain glutamine need of cancer cells; while LAT1, which is sodium independent will have the role of providing cancer cells with some amino acids with plausible signaling roles. According to the metabolic reprogramming of many types of cancer cells, glucose is mainly catabolized by aerobic glycolysis in tumors, while the fate of Glutamine is completed at mitochondrial level where the enzyme Glutaminase converts Glutamine to Glutamate. Glutamine rewiring in cancer cells is heterogeneous. For example, Glutamate is converted to α-Ketoglutarate giving rise to a truncated form of Krebs cycle. This reprogrammed pathway leads to the production of ATP mainly at substrate level and regeneration of reducing equivalents needed for cells growth, redox balance, and metabolic energy. Few studies on hypothetical mitochondrial transporter for Glutamine are reported and indirect evidences suggested its presence. Pharmacological compounds able to inhibit Glutamine metabolism may represent novel drugs for cancer treatments. Interestingly, well acknowledged targets for drugs are the Glutamine transporters of plasma membrane and the key enzyme Glutaminase.

Molecular and functional analysis of glutamine uptake in human hepatoma and liver-derived cells

American journal of physiology. Gastrointestinal and liver physiology, 2002

Human hepatoma cells take up glutamine at rates severalfold faster than the system N-mediated transport rates observed in normal human hepatocytes. Amino acid inhibition, kinetic, Northern blotting, RT-PCR, and restriction enzyme analyses collectively identified the transporter responsible in six human hepatoma cell lines as amino acid transporter B(0) (ATB(0)), the human ortholog of rodent ASCT2. The majority of glutamine uptake in liver fibroblasts and an immortalized human liver epithelial cell line (THLE-5B) was also mediated by ATB(0). The 2.9-kb ATB(0) mRNA was equally expressed in all cell lines, whereas expression of the system A transporters ATA2 and ATA3 was variable. In contrast, the system N isoforms (SN1 and SN2) were expressed only in well-differentiated hepatomas. ATB(0) mRNA was also expressed in cirrhotic liver and adult and pediatric liver cancer biopsies but was not detectable in isolated human hepatocytes or fetal liver. Although the growth of all hepatomas was g...

Key Roles of Glutamine Pathways in Reprogramming the Cancer Metabolism

Oxidative Medicine and Cellular Longevity, 2015

Glutamine (GLN) is commonly known as an important metabolite used for the growth of cancer cells but the effects of its intake in cancer patients are still not clear. However, GLN is the main substrate for DNA and fatty acid synthesis. On the other hand, it reduces the oxidative stress by glutathione synthesis stimulation, stops the process of cancer cachexia, and nourishes the immunological system and the intestine epithelium, as well. The current paper deals with possible positive effects of GLN supplementation and conditions that should be fulfilled to obtain these effects. The analysis of GLN metabolism suggests that the separation of GLN and carbohydrates in the diet can minimize simultaneous supply of ATP (from glucose) and NADPH2(from glutamine) to cancer cells. It should support to a larger extent the organism to fight against the cancer rather than the cancer cells. GLN cannot be considered the effective source of ATP for cancers with the impaired oxidative phosphorylation ...

Glutamine Metabolism in Cancer Cells

Reference Module in Biomedical Sciences, 2018

UDP-glucose ceramide glucosyltransferase (UGCG) is the key enzyme in glycosphingolipid (GSL) metabolism by being the only enzyme that generates glucosylceramide (GlcCer) de novo. Increased UGCG synthesis is associated with pro-cancerous processes such as increased proliferation and multidrug resistance in several cancer types. We investigated the influence of UGCG overexpression on glutamine metabolism in breast cancer cells. We observed adapted glucose and glutamine uptake in a limited energy supply environment following UGCG overexpression. Glutamine is used for reinforced oxidative stress response shown by increased mRNA expression of glutamine metabolizing proteins such as glutathione-disulfide reductase (GSR) resulting in increased reduced glutathione (GSH) level. Augmented glutamine uptake is also used for fueling the tricarboxylic acid (TCA) cycle to maintain the proliferative advantage of UGCG overexpressing cells. Our data reveal a link between GSL and glutamine metabolism in breast cancer cells, which is to our knowledge a novel correlation in the field of sphingolipid research. With about 2.1 million diagnosed cases in 2018, breast cancer is accountable for almost one in four cancer cases among women. Despite extensive research, breast cancer is the leading cause of cancer death in more than 100 countries and the most frequently diagnosed cancer 1. Due to population aging, improved diagnostic methods and environmental changes, the incidence of breast cancer is predicted to increase 2. Furthermore, multidrug resistance (MDR) development leads to cancer therapy failure. UDP-glucose ceramide glucosyltransferase (UGCG) is connected to MDR in several cancer types 3. UGCG is the key enzyme in the glycosphingolipid (GSL) metabolism by transferring UDP-glucose to ceramide resulting in glucosylceramide (GlcCer) production. GlcCer is the precursor for all GSL and our previous studies showed that UGCG overexpression in MCF-7 cells leads to alterations in the composition of glycosphingolipid-enriched microdomains (GEMs) resulting in increased cell proliferation, although nutritional supply was restricted 4. Rapid growth is one cancer cell hallmarks. Since enhanced proliferation entails increased demand for nutrients to serve as building blocks for macromolecules such as proteins, DNA, RNA and lipids, as well as the carbon source for metabolic energy generation, cancer cells have developed mechanisms to increase nutrient uptake. One major energy source for mammalian cells is glucose, which is amongst others an important substrate for protein and lipid synthesis (reviewed in 5). Glucose uptake is accomplished by 14 different glucose transporters (GLUT1-14) (reviewed in 6), whereas GLUT1 is considered as a major transporter of basal glucose uptake and is expressed ubiquitously in human tissue (reviewed in 5). Tumor cells increase their glucose uptake and usage and shuttle glucose to alternative pathways as compared to normal cells (reviewed in 7). The non-essential amino acid glutamine plays a special role in tumor cell metabolism. Although it can be generated endogenously from glucose-derived carbons and amino acid-derived ammonia, glutamine is known to be consumed by some cancer cells in an extensive amount. Glutamine fuels anaplerosis in the tricarboxylic acid (TCA) cycle and nucleotide and fatty acid biosynthesis (reviewed in 7). The TCA cycle in the mitochondria is essential for cell energy metabolism, synthesis of macromolecules and sustaining redox balance (reviewed in 7). Additionally, recent studies have shown that glutamine is also involved in lactate production, chromatin modification, facilitation of the transport of other amino acids and regulation of cell signaling (reviewed in 8). However, Ta et al. showed that lactate is mainly produced from glucose carbons, whereas

The role of the glutamine transporter ASCT2 in antineoplastic therapy

Cancer Chemotherapy and Pharmacology, 2021

Introduction: Cancer cells are metabolically reprogrammed, to support their high proliferative ratio. Cancer cell glucose metabolism plays a very important role in tumor prognosis but, currently, the role of glutamine metabolism in cancer cells has been receiving more attention. In order to supply their high glutamine needs, cancer cells developed an increased expression of membrane transporters that mediate the cellular uptake of this amino acid. ASCT2 (Alanine, Serine, Cysteine Transporter 2) is a Na +dependent transmembrane transporter overexpressed in cancer cells and considered to be the primary transporter for glutamine in these cells. Areas covered: The possibility of inhibiting ASCT2 for antineoplastic therapy is currently under investigation, and inhibition of ASCT2 appears to prevent tumor proliferation by interfering with glutamine entry into the cell. In this article, we will present the pharmacological tools currently known to act on ASCT2, which have been attracting a lot of attention in antineoplastic therapy research. We will also address the impact of ASCT2 inhibition on the prognosis of some cancers. Expert opinion: ASCT2 inhibition seems to be a promising antineoplastic strategy. In addition, combining other anti-tumor therapies with ASCT2 inhibitors appears to be a very effective strategy to treat several cancers. However, more research is needed in this area.

Phorbol esters stimulate the transport of anionic amino acids in cultured human fibroblasts

Biochemical and Biophysical Research Communications, 1990

The effect of phorbol esters on the transport of amino acids has been evaluated in cultured human fibroblasts. The activity of the Na+-dependent system XAG for anionic amino acids is selectively and markedly stimulated by phorbol esters. The effect is maximal whithin 15 min; it is attributable to an increase in transport maximum (Vmax) and not prevented by inhibitors of protein synthesis. The half-maximal stimulation is observed at concentrations of phorbol 12,13-dibutyrate lower than 100 nM. Prolonged incubations in the presence of 1 pM phorbol 12,13-dibutyrate lower the binding of the ligand to its receptor with a loss of the stimulatory effect on transport. The results presented indicate that the stimulation of amino acid transport through system XAG by phorbol esters requires the activation of protein kinase C.

Protein kinase C regulates nutrient uptake and growth in hepatoma cells

Surgery, 1998

Background. Human hepatoma cells extract glutamine at rates severalfold greater than normal hepatocytes through a high-affinity transporter encoded by the ATB 0 gene, which contains two putative phosphorylation sites for protein kinase C (PKC). The studies presented here were undertaken to determine whether System B 0-mediated glutamine uptake regulates hepatoma growth and whether PKC regulates the activity of this transporter. Methods. SK-Hep cells were treated with the PKC activator phorbol 12-myristate 13-acetate (PMA) and the initial-rate transport of glutamine and other nutrients measured at specific times thereafter. Growth rates were monitored during culture ± PMA or an excess of system B 0 substrates relative to glutamine. Results. PMA treatment exerted a rapid (half-life ~ 15 minutes) concentration-dependent inhibition of glutamine uptake rates to 50% of control values via a posttranslational mechanism that decreased transporter maximum velocity. This effect persisted after 24 hours and was abrogated by the PKC inhibitor staurosporine. PMA also significantly decreased amino acid transport System y + and System L activities but not System A. Chronic treatment with PMA (PKC depletion) inhibited SK-Hep growth, as did attenuation of System B 0-mediated glutamine uptake with other B 0 substrates. Conclusions. System B 0-mediated glutamine uptake regulates hepatoma cell growth, whereas PKC influences both processes.

Right on TARGET: glutamine metabolism in cancer

Oncoscience, 2015

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