bims-meluca Biomed News
on Metabolism of non-small cell lung carcinoma
Issue of 2020‒11‒29
eight papers selected by
Cristina Muñoz Pinedo
L’Institut d’Investigació Biomèdica de Bellvitge

  1. J Photochem Photobiol B. 2020 Nov 13. pii: S1011-1344(20)30530-3. [Epub ahead of print]213 112080
      Differential inherent and acquired radioresistance of human lung cancer cells contribute to poor therapeutic outcome and tumor recurrence after radiotherapy. Inherent radioresistance of lung cancer cells is known to be associated with ROSLow cancer stem cells (CSCs). However, mechanism of acquired radioresistance in lung cancer cells is poorly understood. Here, we exposed human lung cancer cells (A549) to a cumulative dose of 40Gy and allowed the radioresistant (RR) survivors to divide and form macroscopic colonies after each fraction of 5Gy dose. The RR subline exhibited enrichment of cytosolic ROSHigh cells without specific increase in mitochondrial ROS levels. We found a concomitant increase in the expression of redox regulatory transcription factor Nrf2 and its dependent antioxidant genes in RR cells and cell cycle delay as compared to parental cells. The treatment of RR cells with Nrf2 inhibitor resulted in decreased clonogenic survival indicating their addiction to Nrf2 for metabolic adaptations under high levels of cytosolic ROS. A causal role of inherent ROS levels in conferring radioresistance was established by sorting ROSHigh and ROSLow populations from parental and RR cells. It was observed that ROSHigh population from both parental and RR cells exhibited radioresistance as observed by clonogenic assay. Interestingly, ROSHigh population of cells exhibited higher levels of cellular thiols in both parental and RR cells. Thus, our observations highlight presence of a novel subpopulation in lung cancer cells, which exhibits radioresistance by maintaining 'oxidative stress' and Nrf2 dependent metabolic adaptations. We also posit Nrf2 pathway as a druggable target for radiosensitization of RR A549 cells.
    Keywords:  Antioxidant; Cancer stem cells; Radiosensitization; Radiotherapy; Thiols
  2. Ann Transl Med. 2020 Sep;8(18): 1169
      Background: Indoleamine 2,3-dioxygenase (IDO), a limiting enzyme in the IDO/kynurenine (Kyn) pathway, converts tryptophan (Trp) into Kyn, and plays a significant role in immune suppression and tumor immune evasion. This study aimed to investigate the association between IDO activity and clinical outcomes in non-small cell lung cancer (NSCLC) patients who underwent radiotherapy (RT).Methods: Serum Kyn and Trp levels were measured in 104 NSCLC patients by high-performance liquid chromatography at baseline, and the following RT. The correlation between IDO activity, as computed by Kyn: Trp ratios and survival was estimated using Kaplan-Meier curves. Cox proportional hazard models are used in the univariate and multivariate analyses.
    Results: Both the Kyn levels and Kyn:Trp ratios were reduced after RT at a biologically equivalent dose (BED) of <70 Gy, while these increased at a BED of ≥70 Gy. Post/pre-Kyn levels were positively correlated with an objective response. Patients with a higher Kyn:Trp ratio pre-RT had the worse median progression-free survival (mPFS, 13.5 vs. 24.5 months, P=0.049). Higher post/pre-Kyn:Trp ratios were correlated with improved median overall survival (mOS, 23.8 months vs. not reached, P=0.032). On the multivariate analysis, pre-RT Kyn:Trp and post/pre-Kyn:Trp ratios remained as independent predictive factors for PFS and OS, respectively.
    Conclusions: It was proved that RT could alter IDO-mediated immune activity and establish strong correlations between IDO activity and survival outcomes in NSCLC patients treated with RT. These present findings suggest that the profiling of IDO activity might allow for the prompt adjustment of RT doses and better predict patient response to RT.
    Keywords:  Indoleamine 2,3-dioxygenase activity (IDO activity); non-small cell lung cancer (NSCLC); prognosis; radiotherapy-induced immune response
  3. Cell Death Dis. 2020 Nov 26. 11(11): 1012
      Nutrient utilization and reshaping of metabolism in cancer cells is a well-known driver of malignant transformation. Less clear is the influence of the local microenvironment on metastasis formation and choice of the final organ to invade. Here we show that the level of the amino acid serine in the cytosol affects the migratory properties of lung adenocarcinoma (LUAD) cells. Inhibition of serine or glycine uptake from the extracellular milieu, as well as knockdown of the cytosolic one-carbon metabolism enzyme serine hydroxymethyltransferase (SHMT1), abolishes migration. Using rescue experiments with a brain extracellular extract, and direct measurements, we demonstrate that cytosolic serine starvation controls cell movement by increasing reactive oxygen species formation and decreasing ATP levels, thereby promoting activation of the AMP sensor kinase (AMPK) by phosphorylation. Activation of AMPK induces remodeling of the cytoskeleton and finally controls cell motility. These results highlight that cytosolic serine metabolism plays a key role in controlling motility, suggesting that cells are able to dynamically exploit the compartmentalization of this metabolism to adapt their metabolic needs to different cell functions (movement vs. proliferation). We propose a model to explain the relevance of serine/glycine metabolism in the preferential colonization of the brain by LUAD cells and suggest that the inhibition of serine/glycine uptake and/or cytosolic SHMT1 might represent a successful strategy to limit the formation of brain metastasis from primary tumors, a major cause of death in these patients.
  4. Cancer Res. 2020 Nov 23. pii: canres.0617.2020. [Epub ahead of print]
      Cancer cells need to generate large amounts of glutathione (GSH) to buffer oxidative stress during tumor development. A rate-limiting step for GSH biosynthesis is cystine uptake via a cystine/glutamate antiporter Xc-. Xc- is a sodium-independent antiporter passively driven by concentration gradients from extracellular cystine and intracellular glutamate across the cell membrane. Increased uptake of cystine via Xc- in cancer cells increases the level of extracellular glutamate, which would subsequently restrain cystine uptake via Xc-. Cancer cells must therefore evolve a mechanism to overcome this negative feedback regulation. In this study, we report that glutamate transporters, in particular SLC1A1, are tightly intertwined with cystine uptake and GSH biosynthesis in lung cancer cells. Dysregulated SLC1A1, a sodium-dependent glutamate carrier, actively recycled extracellular glutamate into cells, which enhanced the efficiency of cystine uptake via Xc- and GSH biosynthesis as measured by stable isotope-assisted metabolomics. Conversely, depletion of glutamate transporter SLC1A1 increased extracellular glutamate, which inhibited cystine uptake, blocked GSH synthesis, and induced oxidative stress-mediated cell death or growth inhibition. Moreover, glutamate transporters were frequently upregulated in tissue samples of non-small cell lung cancer patients. Taken together, active uptake of glutamate via SLC1A1 propels cystine uptake via Xc- for GSH biosynthesis in lung tumorigenesis.
  5. Mol Med Rep. 2021 Jan;pii: 74. [Epub ahead of print]23(1):
      The platelet isoform of phosphofructokinase (PFKP) is a rate‑limiting enzyme involved in glycolysis that serves an important role in various types of cancer. The aim of the present study was to explore the specific regulatory relationship between PFKP and non‑small cell lung cancer (NSCLC) progression. PFKP expression in NSCLC tissues and corresponding adjacent tissues was detected using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and immunohistochemical analysis. PFKP expression in human bronchial epithelial cells (16HBE) and NSCLC cells (H1299, H23 and A549) was also detected using RT‑qPCR. Cell proliferation was detected by Cell Counting Kit‑8 and colony formation assays. Transwell invasion and wound healing assays, and flow cytometry were used to detect cell invasion, migration and apoptosis, respectively. The expression levels of glycolysis‑associated enzymes (hexokinase‑2, lactate dehydrogenase A and glucose transporter‑1), epithelial‑mesenchymal transition‑related proteins (N‑cadherin, vimentin and E‑cadherin) and apoptosis‑related proteins (caspase‑3 and B‑cell lymphoma‑2) were detected by western blotting. Glucose uptake, lactate production and the adenosine trisphosphate/adenosine diphosphate ratio were measured using the corresponding kits. The results of the present study demonstrated that PFKP expression was upregulated in NSCLC tissues and cells, and PFKP expression was related to lymph node metastasis and histological grade. In addition, overexpression of PFKP inhibited cell apoptosis, and promoted proliferation, migration, invasion and glycolysis of H1299 cells, whereas knockdown of PFKP had the opposite effects. In conclusion, PFKP inhibited cell apoptosis, and promoted proliferation, migration, invasion and glycolysis of NSCLC cells; these findings may lay the foundation for novel treatments of NSCLC.
  6. J Immunother Cancer. 2020 Nov;pii: e001392. [Epub ahead of print]8(2):
      BACKGROUND: The immune checkpoint blockade (ICB) targeting programmed cell death-1 (PD-1) and its ligand (PD-L1) has been proved beneficial for numerous types of cancers, including non-small-cell lung cancer (NSCLC). However, a significant number of patients with NSCLC still fail to respond to ICB due to unfavorable tumor microenvironment. To improve the efficacy, the immune-chemotherapy combination with pemetrexed, cis/carboplatin and pembrolizumab (anti-PD-1) has been recently approved as first-line treatment in advanced NSCLCs. While chemotherapeutic agents exert beneficial effects, the underlying antitumor mechanism(s) remains unclear.METHODS: Pemetrexed, cisplatin and other chemotherapeutic agents were tested for the potential to induce PD-L1 expression in NSCLC cells by immunoblotting and flow cytometry. The ability to prime the tumor immune microenvironment was then determined by NSCLC/T cell coculture systems and syngeneic mouse models. Subpopulations of NSCLC cells responding differently to pemetrexed were selected and subjected to RNA-sequencing analysis. The key signaling pathways were identified and validated in vitro and in vivo.
    RESULTS: Pemetrexed induced the transcriptional activation of PD-L1 (encoded by CD274) by inactivating thymidylate synthase (TS) in NSCLC cells and, in turn, activating T-lymphocytes when combined with the anti-PD-1/PD-L1 therapy. Nuclear factor κB (NF-κB) signaling was activated by intracellular reactive oxygen species (ROSs) that were elevated by pemetrexed-mediated TS inactivation. The TS-ROS-NF-κB regulatory axis actively involves in pemetrexed-induced PD-L1 upregulation, whereas when pemetrexed fails to induce PD-L1 expression in NSCLC cells, NF-κB signaling is unregulated. In syngeneic mouse models, the combinatory treatment of pemetrexed with anti-PD-L1 antibody created a more favorable tumor microenvironment for the inhibition of tumor growth.
    CONCLUSIONS: Our findings reveal novel mechanisms showing that pemetrexed upregulates PD-L1 expression and primes a favorable microenvironment for ICB, which provides a mechanistic basis for the combinatory chemoimmunotherapy in NSCLC treatment.
    Keywords:  combination; costimulatory and inhibitory t-cell receptors; drug therapy; immunotherapy; tumor escape; tumor microenvironment
  7. Redox Biol. 2020 Nov 18. pii: S2213-2317(20)31006-5. [Epub ahead of print]38 101801
      The biological functions of N6-methyladenosine (m6A) RNA methylation are mainly dependent on the reader; however, its role in lung tumorigenesis remains unclear. Here, we have demonstrated that the m6A reader YT521-B homology domain containing 2 (YTHDC2) is frequently suppressed in lung adenocarcinoma (LUAD). Downregulation of YTHDC2 was associated with poor clinical outcome of LUAD. YTHDC2 decreased tumorigenesis in a spontaneous LUAD mouse model. Moreover, YTHDC2 exhibited antitumor activity in human LUAD cells. Mechanistically, YTHDC2, via its m6A-recognizing YTH domain, suppressed cystine uptake and blocked the downstream antioxidant program. Administration of cystine downstream antioxidants to pulmonary YTHDC2-overexpressing mice rescued lung tumorigenesis. Furthermore, solute carrier 7A11 (SLC7A11), the catalytic subunit of system XC-, was identified to be the direct target of YTHDC2. YTHDC2 destabilized SLC7A11 mRNA in an m6A-dependent manner because YTHDC2 preferentially bound to m6A-modified SLC7A11 mRNA and thereafter promoted its decay. Clinically, a large proportion of acinar LUAD subtype cases exhibited simultaneous YTHDC2 downregulation and SLC7A11 elevation. Patient-derived xenograft (PDX) mouse models generated from acinar LUAD showed sensitivity to system XC- inhibitors. Collectively, the promotion of cystine uptake via the suppression of YTHDC2 is critical for LUAD tumorigenesis, and blocking this process may benefit future treatment.
    Keywords:  Cystine uptake; Lipid peroxidation; METTL3; System X(C)(−); m(6)A RNA methylation
  8. Cancer Res. 2020 Nov 25. pii: canres.1865.2020. [Epub ahead of print]
      Lung cancer is a prevalent and lethal cancer type that leads to more deaths than the next four major cancer types combined. Metastatic cancer spread is responsible for most cancer deaths but the cellular changes that enable cancer cells to leave the primary tumor and establish inoperable and lethal metastases remain poorly understood. To uncover genes that are specifically required to sustain metastasis survival or growth, we performed a genome-scale pooled lentiviral-shRNA library screen in cells that represent non-metastatic and metastatic states of lung adenocarcinoma. Mitochondrial ribosome and mitochondria-associated genes were identified as top gene sets associated with metastasis-specific lethality. Metastasis-derived cell lines in vitro and metastases analyzed ex vivo from an autochthonous lung cancer mouse model had lower mitochondrial membrane potential and reduced mitochondrial functionality than non-metastatic primary tumors. Electron microscopy of metastases uncovered irregular mitochondria with bridging and loss of normal membrane structure. Consistent with these findings, compounds that inhibit mitochondrial translation or replication had a greater effect on the growth of metastasis-derived cells. Finally, mice with established tumors developed fewer metastases upon treatment with phenformin in vivo. These results suggest that the metastatic cell state in lung adenocarcinoma is associated with a specifically altered mitochondrial functionality that can be therapeutically exploited.