bims-istrec Biomed News
on Integrated stress response in cancer
Issue of 2022‒07‒24
ten papers selected by
the Vincenzo Ciminale lab
Istituto Oncologico Veneto

  1. Br J Pharmacol. 2022 Jul 19.
      BACKGROUND AND PURPOSE: Endoplasmic reticulum (ER) stress triggers an adaptive response in tumors which fosters their cell survival and resilience to stress. Activation of the ER stress response, through its PERK branch, promotes phosphorylation of the α-subunit of the translation initiation factor eIF2alpha, repressing general protein translation and selectively augmenting the translation of ATF4 with the downstream CHOP transcription factor and the protein disulfide oxidase ERO1.EXPERIMENTAL APPROACH: Here we show that ISRIB, a small molecule that inhibits the action of the phosphorylated α-subunit of eIF2, activating protein translation, synergistically interacts with the genetic deficiency of protein disulfide oxidase ERO1, enfeebling breast tumor growth and spread.
    KEY RESULTS: ISRIB represses the CHOP signal but, surprisingly, it does not inhibit ERO1. Mechanistically ISRIB increases the ER protein load with a marked perturbing effect on ERO1-deficient triple-negative breast cancer cells, which display impaired proteostasis and have adapted to living with a low client protein load in hypoxia, while ERO1 deficiency also impairs VEGF-dependent angiogenesis. ERO1-deficient triple-negative breast cancer xenografts have an augmented ER stress response and its PERK branch. ISRIB acts synergistically with ERO1 deficiency, inhibiting the growth of triple-negative breast cancer xenografts by impairing proliferation and angiogenesis, while it is not so effective on the xenograft counterparts with ERO1.
    CONCLUSIONS AND IMPLICATIONS: These results demonstrate that ISRIB together with ERO1 deficiency synergistically shatter the PERK-dependent adaptive ER stress response by restarting protein synthesis in the setting of impaired proteostasis, finally promoting tumor cytotoxicity. Therefore, our findings suggest two surprising features in breast tumors: ERO1 is not regulated via CHOP under hypoxic conditions, and ISRIB offers a therapeutic option to efficiently inhibit tumor progression in those tumors with limited ERO1 and high PERK, and thus impaired proteostasis.
    Keywords:  ERO1 alpha; Endoplasmic reticulum Stress; ISRIB (Integrated Stress Response Inhibitor); PERK pathway; UPR (unfolded protein response); breast cancer
  2. EJHaem. 2021 Nov;2(4): 818-822
      Loss of endoplasmic reticulum (ER) homeostasis leads to ER stress, thus prolonged activation can lead to apoptosis. Herein, artesunate (ART) induced ER stress in leukaemia cells, resulting in eIF2α phosphorylation, activation of transcription factor 4, subsequent CHOP upregulation and XBP1 splicing. Furthermore, in vitro cyclin/CDKs reduction induced G1-phase arrest. An in vivo xenograft model showed a consistent pattern of ART in reducing tumour burden, supporting roles in the UPR pathway, which we speculate could lead to apoptosis by NOXA activation. Moreover, ART were capable of increasing the survival of mice. Taken together, our data indicate that ART may represent an interesting weapon to fight leukaemia.
    Keywords:  acute leukaemia; artemisinin; artesunate; endoplasmic reticulum stress
  3. Front Oncol. 2022 ;12 767479
      Regions of hypoxia are common in solid tumors and drive changes in gene expression that increase risk of cancer metastasis. Tumor cells must respond to the stress of hypoxia by activating genes to modify cell metabolism and antioxidant response to improve survival. The goal of the current study was to determine the effect of hypoxia on cell metabolism and markers of oxidative stress in metastatic (metM-Wntlung) compared with nonmetastatic (M-Wnt) murine mammary cancer cell lines. We show that hypoxia induced a greater suppression of glutamine to glutamate conversion in metastatic cells (13% in metastatic cells compared to 7% in nonmetastatic cells). We also show that hypoxia increased expression of genes involved in antioxidant response in metastatic compared to nonmetastatic cells, including glutamate cysteine ligase catalytic and modifier subunits and malic enzyme 1. Interestingly, hypoxia increased the mRNA level of the transaminase glutamic pyruvic transaminase 2 (Gpt2, 7.7-fold) only in metM-Wntlung cells. The change in Gpt2 expression was accompanied by transcriptional (4.2-fold) and translational (6.5-fold) induction of the integrated stress response effector protein activating transcription factor 4 (ATF4). Genetic depletion ATF4 demonstrated importance of this molecule for survival of hypoxic metastatic cells in detached conditions. These findings indicate that more aggressive, metastatic cancer cells utilize hypoxia for metabolic reprogramming and induction of antioxidant defense, including activation of ATF4, for survival in detached conditions.
    Keywords:  ATF4 activating transcription factor 4; breast cancer; cell stress; hypoxia; integrated stress response (ISR); metastasis
  4. Front Oncol. 2022 ;12 930923
      Gliomas are a group of the most aggressive primary central nervous system tumors with limited treatment options. The abnormal expression of long non-coding RNA (lncRNA) is related to the prognosis of glioma. However, the role of endoplasmic reticulum (ER) stress-associated lncRNAs in glioma prognosis has not been reported. In this paper, we obtained ER stress-related lncRNAs by co-expression analysis, and then a risk signature composed of 6 ER stress-related lncRNAs was constructed using Cox regression analysis. Glioma samples in The Cancer Genome Atlas (TCGA) were separated into high- and low-risk groups based on the median risk score. Compared with the low-risk group, patients in the high-risk group had shorter survival times. Additionally, we verified the predictive ability of these candidate lncRNAs in the testing set. Three glioma patient subgroups (cluster 1/2/3) were identified by consensus clustering. We further analysed the abundance of immune-infiltrating cells and the expression levels of immune checkpoint molecules in both three subgroups and two risk groups, respectively. Immunotherapy and anticancer drug response prediction showed that ER stress-related lncRNA risk signature positively correlates with responding to immune checkpoints and chemosensitivity. Functional analysis showed that these gene sets are enriched in the malignant process of tumors. Finally, LINC00519 was chosen for functional experiments. The silence of LINC00519 restrained the migration and invasion of glioma cells. Hence, those results indicated that ER stress-related lncRNA risk signature could be a potential treatment target and a prognosis biomarker for glioma patients.
    Keywords:  endoplasmic reticulum stress; glioma; immune; lncRNA; prognosis; risk signature
  5. Thorac Cancer. 2022 Jul 21.
      BACKGROUND: Pazopanib is an approved multitarget anticancer agent for soft tissue sarcoma (STS) and renal cell carcinoma (RCC), which is also under clinical investigation for other malignancies, including small cell lung cancer (SCLC). However, the potential anti-SCLC mechanisms of pazopanib remain unclear.METHODS: Cell viability was evaluated by CCK-8, apoptotic cell detection was conducted using annexin V/PI staining followed by flow cytometry, and Western blot analysis was used to detect the apoptotic-related molecules and ER-stress pathway effectors. The intracellular reactive oxygen species (ROS) level was determined by DCFH-HA staining followed by flow cytometry. An NCI-H446 xenograft model was established to evaluate pazopanib on tumor suppression in vivo. Immunohistochemistry (IHC) was used to assess the proliferative activity of xenograft in NCI-H446 cell-bearing NOD-SCID mice.
    RESULTS: Pazopanib dose- and time-dependently inhibited SCLC cell proliferation induced significant apoptosis in SCLC cell lines, increased cleaved-caspase3 and Bax, and decreased Bcl-2. Moreover, the PERK-related ER-stress pathway was potently activated by pazopanib treatment, inhibiting ER-stress by salubrinal significantly reversing pazopanib-mediated apoptosis in SCLC cell lines. Furthermore, pazopanib-induced intracellular ROS levels increased, while inhibiting ROS by NAC significantly reversed pazopanib-induced apoptosis in SCLC cells. In addition, pazopanib significantly suppressed NCI-H446 xenograft growth and decreased Ki67 positive cells in the tumor.
    CONCLUSION: Our findings indicate that pazopanib induces SCLC cell apoptosis through the ER-stress process via upregulation of ROS levels. Further investigation of relevant biomarkers to accurately select patients for benefit from pazopanib should be further investigated.
    Keywords:  Pazopanib; apoptosis; endoplasmic reticulum stress (ER-stress); reactive oxygen species (ROS); small cell lung cancer (SCLC)
  6. EMBO Mol Med. 2022 Jul 21. e15855
      FBXW7 is one of the most frequently mutated tumor suppressors, deficiency of which has been associated with resistance to some anticancer therapies. Through bioinformatics and genome-wide CRISPR screens, we here reveal that FBXW7 deficiency leads to multidrug resistance (MDR). Proteomic analyses found an upregulation of mitochondrial factors as a hallmark of FBXW7 deficiency, which has been previously linked to chemotherapy resistance. Despite this increased expression of mitochondrial factors, functional analyses revealed that mitochondria are under stress, and genetic or chemical targeting of mitochondria is preferentially toxic for FBXW7-deficient cells. Mechanistically, the toxicity of therapies targeting mitochondrial translation such as the antibiotic tigecycline relates to the activation of the integrated stress response (ISR) in a GCN2 kinase-dependent manner. Furthermore, the discovery of additional drugs that are toxic for FBXW7-deficient cells showed that all of them unexpectedly activate a GCN2-dependent ISR regardless of their accepted mechanism of action. Our study reveals that while one of the most frequent mutations in cancer reduces the sensitivity to the vast majority of available therapies, it renders cells vulnerable to ISR-activating drugs.
    Keywords:  FBXW7; GCN2; ISR; drug resistance; mitochondria
  7. Front Oncol. 2022 ;12 836087
      Background: Chronic inflammation contributes to approximately 20% of cancers; the underlying mechanisms are still elusive. Here, using an animal model of colitis to colon-cancerous transformation, we demonstrated that endoplasmic reticulum (ER) stress couples with metabolic reprogramming to promote a malignant transformation of chronic inflammation.Methods: The animal model for chronic colitis to colon-cancerous transformation was established in C57BL/6N mice by azoxymethane (AOM) and dextran sodium sulfate (DSS) treatments. The differential proteins in control and AOM/DSS-treated colon mucosa were determined using proteomic analysis; the kinetics of metabolic modifications were monitored by mitochondrial oxygen flux, extracellular acidification, and targeted metabolomics; the molecule linker between ER stress and metabolic modifications were identified by coimmunoprecipitation, KEGG pathway analysis, and the subcutaneous tumor model using gene-specific knockdown colon cancer cells. Tissue array analysis were used to evaluate the differential protein in cancer and cancer-adjacent tissues.
    Results: AOM/DSS treatment induced 38 tumors in 10 mice at the 14th week with the mean tumor size 9.35 ± 3.87 mm2, which was significantly decreased to 5.85 ± 0.95 mm2 by the ER stress inhibitor 4-phenylbutyric acid (4PBA). Seven differential proteins were determined from control (1,067 ± 48) and AOM/DSS-treated mucosa (1,077 ± 59); the level of ER protein PDIA2 (protein disulfide isomerase-associated 2) was increased over 7-fold in response to AOM/DSS treatment. PDIA2 interacted with 420 proteins that were involved in 8 signaling pathways, in particular with 53 proteins in metabolic pathways. PDIA2 translocated from ER to mitochondria and interacted with the components of complexes I and II to inhibit oxophosphorylation but increase glycolysis. Knockdown PDIA2 in colon cancer cells restored the metabolic imbalance and significantly repressed tumor growth in the xenograft animal model. 4PBA therapy inhibited the AOM/DSS-mediated overexpression of PDIA2 and metabolic modifications and suppressed colon cancer growth. In clinic, PDIA2 was overexpressed in colon cancer tissues rather than cancer-adjacent tissues and was related with the late stages and lymph node metastasis of colon cancer.
    Conclusions: Persistent ER stress reprograms the metabolism to promote the malignant transformation of chronic colitis; PDIA2 serves as a molecule linker between ER stress and metabolic reprogramming. The inhibition of ER stress restores metabolic homeostasis and attenuates the cancerous transformation of chronic inflammation.
    Keywords:  PDIA2; chronic colitis; colon cancer; endoplasmic reticulum stress; malignant transformation; metabolic reprogramming
  8. Redox Biol. 2022 Jul 14. pii: S2213-2317(22)00179-3. [Epub ahead of print]55 102407
      Iron is a mineral essential for blood production and a variety of critical cellular functions. Altered iron metabolism has been increasingly observed in many diseases and disorders, but a comprehensive and mechanistic understanding of the cellular impact of impaired iron metabolism is still lacking. We examined the effects of iron overload or iron deficiency on cellular stress responses and autophagy which collectively regulate cell homeostasis and survival. Acute iron loading led to increased mitochondrial ROS (mtROS) production and damage, lipid peroxidation, impaired autophagic flux, and ferroptosis. Iron-induced mtROS overproduction is the mechanism of increased lipid peroxidation, impaired autophagy, and the induction of ferroptosis. Iron excess-induced ferroptosis was cell-type dependent and regulated by activating transcription factor 4 (ATF4). Upregulation of ATF4 mitigated iron-induced autophagic dysfunction and ferroptosis, whereas silencing of ATF4 expression impaired autophagy and resulted in increased mtROS production and ferroptosis. Employing autophagy-deficient hepatocytes and different autophagy inhibitors, we further showed that autophagic impairment sensitized cells to iron-induced ferroptosis. In contrast, iron deficiency activated the endoplasmic reticulum (ER) stress response, decreased autophagy, and induced apoptosis. Decreased autophagy associated with iron deficiency was due to ER stress, as reduction of ER stress by 4-phenylbutyric acid (4-PBA) improved autophagic flux. The mechanism of decreased autophagy in iron deficiency is a disruption in lysosomal biogenesis due to impaired posttranslational maturation of lysosomal membrane proteins. In conclusion, iron excess and iron deficiency cause different forms of cell stress and death in part through the common mechanism of impaired autophagic function.
    Keywords:  ATF4; ER stress; Ferroptosis; Lipid peroxidation; Mitochondria
  9. Cell Death Dis. 2022 Jul 21. 13(7): 636
      The efficacy of apatinib has been confirmed in the treatment of solid tumors, including non-small-cell lung cancer (NSCLC). However, the direct functional mechanisms of tumor lethality mediated by apatinib and the precise mechanisms of drug resistance are largely unknown. In this study, we demonstrated that apatinib could reprogram glutamine metabolism in human NSCLC via a mechanism involved in amino acid metabolic imbalances. Apatinib repressed the expression of GLS1, the initial and rate-limiting enzyme of glutamine catabolism. However, the broken metabolic balance led to the activation of the amino acid response (AAR) pathway, known as the GCN2/eIF2α/ATF4 pathway. Moreover, activation of ATF4 was responsible for the induction of SLC1A5 and ASNS, which promoted the consumption and metabolization of glutamine. Interestingly, the combination of apatinib and ATF4 silencing abolished glutamine metabolism in NSCLC cells. Moreover, knockdown of ATF4 enhanced the antitumor effect of apatinib both in vitro and in vivo. In summary, this study showed that apatinib could reprogram glutamine metabolism through the activation of the AAR pathway in human NSCLC cells and indicated that targeting ATF4 is a potential therapeutic strategy for relieving apatinib resistance.
  10. Bioorg Chem. 2022 Jul 09. pii: S0045-2068(22)00419-9. [Epub ahead of print]127 106013
      In the present study, six new cucurbitane type compounds, including three triterpenoids hemsleyacins P-R (6-7, 13) and three cucurbitane-type triterpenoid glycosides hemsleyaosides L-N (15-17), along with seventeen known cucurbitacin analogues were separated from the root tuber of Hemsleya penxianensis and elucidated based on NMR and HRESIMS. Then, 23 analogues of three types, namely, polyhydroxy-type (I) (1-7), monohydroxy-type (II) (8-13), and glycosides-type (III) (14-23), were assessed for their antitumor activity and structure-activity relationship analysis (SAR). We determined temozolomide (TMZ)-resistant GBM cell was the most sensitive to the tested compounds, and found hemsleyaoside N (HDN) displayed the best antineoplastic potency. Furthermore, we confirmed the anti-glioma activity of HDN in patient-derived recurrent GBM strains, GBM organoid (GBO) and orthotopic nude mouse models. Investigations exploring the mechanism made clear that HDN induced synchronous activation of UPR and MAPK signaling, which triggered deadly ER stress and apoptosis. Taken together, the potent antitumor activity of HDN warrants further comprehensive evaluation as a novel anti-glioma agent.
    Keywords:  Chemotherapy resistance; Cucurbitane triterpenoids; Glioblastoma; Hemsleyaoside N