bims-istrec Biomed News
on Integrated stress response in cancer
Issue of 2022‒03‒13
eleven papers selected by
Vincenzo Ciminale’s Lab
Istituto Oncologico Veneto
  1. IRE-1-Targeting Caged Prodrug with Endoplasmic Reticulum Stress-Inducing and XBP-1S-Inhibiting Activities for Cancer Therapy.
  2. Selective pressure of endocrine therapy activates the integrated stress response through NFκB signaling in a subpopulation of ER positive breast cancer cells.
  3. On the origin of metastases: Induction of pro-metastatic states after impending cell death via ER stress, reprogramming, and a cytokine storm.
  4. Psoralen inhibits the proliferation and promotes apoptosis through endoplasmic reticulum stress in human osteosarcoma cells.
  5. Preclinical studies with ONC201/TIC10 and lurbinectedin as a novel combination therapy in small cell lung cancer (SCLC).
  6. Iodine-125 induced cholangiocarcinoma cell death is enhanced by inhibition of endoplasmic reticulum stress-mediated protective autophagy.
  7. ONC206 has anti-tumorigenic effects in human ovarian cancer cells and in a transgenic mouse model of high-grade serous ovarian cancer.
  8. Bixin Prevents Colorectal Cancer Development through AMPK-Activated Endoplasmic Reticulum Stress.
  9. Methylmercury Induces Mitochondria- and Endoplasmic Reticulum Stress-Dependent Pancreatic β-Cell Apoptosis via an Oxidative Stress-Mediated JNK Signaling Pathway.
  10. Effects of endoplasmic reticulum stress-mediated CREB3L1 on apoptosis of glioma cells.
  11. Flavonoids from Scutellaria barbata D. Don exert antitumor activity in colorectal cancer through inhibited autophagy and promoted apoptosis via ATF4/sestrin2 pathway.
  1. Mol Pharm. 2022 Mar 07.
    IRE-1-Targeting Caged Prodrug with Endoplasmic Reticulum Stress-Inducing and XBP-1S-Inhibiting Activities for Cancer Therapy.
    Andong Shao, Qin Xu, Chang Won Kang, Christopher F Cain, Avery C Lee, Chih-Hang Anthony Tang, Juan R Del Valle, Chih-Chi Andrew Hu.
      Activation of the IRE-1/XBP-1s pathway supports tumor progression. Here, we report a novel prodrug, TC-D-F07, in which a thiol-reactive dinitrobenzenesulfonyl (Dns) cage was installed onto the C8 hydroxyl of the covalent IRE-1 inhibitor D-F07. The electron-withdrawing Dns group in TC-D-F07 stabilizes the neighboring 1,3-dioxane acetal, allowing for stimulus-mediated control of its inhibitory activity. TC-D-F07 exhibits high sensitivity to intracellular thiols. Because tumor cells exhibit higher concentrations of glutathione and cysteine, treatment with TC-D-F07 results in more sustained levels of D-F07 in transformed versus normal cells. In addition, we show that a dinitrophenyl cysteine adduct resulting from cleavage of the Dns group induces endoplasmic reticulum (ER) stress, causing tumor cells to increase the expression of XBP-1s. The accumulated levels of D-F07 and its gradual decomposition into the active IRE-1 inhibitor eventually deprive tumor cells of XBP-1s, leading to more severe apoptosis than those treated with its uncaged analogue.
    Keywords:  ATF4; ATF6; IRE-1; PERK; cancer; endoplasmic reticulum stress; unfolded protein response
    DOI:  https://doi.org/10.1021/acs.molpharmaceut.1c00639
  2. Breast Cancer Res. 2022 Mar 09. 24(1): 19
    Selective pressure of endocrine therapy activates the integrated stress response through NFκB signaling in a subpopulation of ER positive breast cancer cells.
    Svetlana E Semina, Purab Pal, Nidhi S Kansara, Rosemary J Huggins, Elaine T Alarid, Geoffrey L Greene, Jonna Frasor.
      BACKGROUND: While estrogen receptor (ER) positive breast tumors generally respond well to endocrine therapy (ET), up to 40% of patients will experience relapse, either while on endocrine therapy or after ET is completed. We previously demonstrated that the selective pressure of tamoxifen activates the NFκB pathway in ER + patient tumors, breast cancer cell lines, and breast cancer xenograft tumors, and that this activation allows for survival of a subpopulation of NFκB + cells that contribute to cell regrowth and tumor relapse after ET withdrawal. However, the mechanisms contributing to the expansion of an NFκB + cell population on ET are unknown.METHODS: Here, we utilized single-cell RNA sequencing and bioinformatics approaches to characterize the NFκB + cell population and its clinical relevance. Follow-up studies were conducted to validate our findings and assess the function of the integrated stress response pathway in breast cancer cell lines and patient-derived models.
    RESULTS: We found that the NFκB + population that arises in response to ET is a preexisting population is enriched under the selective pressure of ET. Based on the preexisting NFκB + cell population, we developed a gene signature and found that it is predictive of tumor relapse when expressed in primary ER + tumors and is retained in metastatic cell populations. Moreover, we identified that the integrated stress response (ISR), as indicated by increased phosphorylation of eIF2α, occurs in response to ET and contributes to clonogenic growth under the selective pressure of ET.
    CONCLUSIONS: Taken together, our findings suggest that a cell population with active NFκB and ISR signaling can survive and expand under the selective pressure of ET and that targeting this population may be a viable therapeutic strategy to improve patient outcome by eliminating cells that survive ET. Understanding the mechanisms by which breast cancer cells survive the selective pressure of ET may improve relapse rates and overall outcome for patients with ER + breast tumors.
    Keywords:  Breast cancer; Endocrine therapy; Estrogen receptor; Integrated stress response; NFκB
    DOI:  https://doi.org/10.1186/s13058-022-01515-1
  3. Cell Rep. 2022 Mar 08. pii: S2211-1247(22)00223-6. [Epub ahead of print]38(10): 110490
    On the origin of metastases: Induction of pro-metastatic states after impending cell death via ER stress, reprogramming, and a cytokine storm.
    Arwen Conod, Marianna Silvano, Ariel Ruiz I Altaba.
      How metastatic cells arise is unclear. Here, we search for the induction of recently characterized pro-metastatic states as a surrogate for the origin of metastasis. Since cell-death-inducing therapies can paradoxically promote metastasis, we ask if such treatments induce pro-metastatic states in human colon cancer cells. We find that post-near-death cells acquire pro-metastatic states (PAMEs) and form distant metastases in vivo. These PAME ("let's go" in Greek) cells exhibit a multifactorial cytokine storm as well as signs of enhanced endoplasmic reticulum (ER) stress and nuclear reprogramming, requiring CXCL8, INSL4, IL32, PERK-CHOP, and NANOG. PAMEs induce neighboring tumor cells to become PAME-induced migratory cells (PIMs): highly migratory cells that re-enact the storm and enhance PAME migration. Metastases are thus proposed to originate from the induction of pro-metastatic states through intrinsic and extrinsic cues in a pro-metastatic tumoral ecosystem, driven by an impending cell-death experience involving ER stress modulation, metastatic reprogramming, and paracrine recruitment via a cytokine storm.
    Keywords:  ER stress; PAME; apoptosis; colon cancer; cytokine storm; metastasis; metastasis-initiating cells; metastatic reprogramming; primary heterogeneity; regulated cell death
    DOI:  https://doi.org/10.1016/j.celrep.2022.110490
  4. Folia Histochem Cytobiol. 2022 Mar 08.
    Psoralen inhibits the proliferation and promotes apoptosis through endoplasmic reticulum stress in human osteosarcoma cells.
    Shubo Li, Hongqin Tu.
      INTRODUCTION: . Psoralen is a main active component of Psoralea corylifolia Linn. (Leguminosae). Psoralen has been reported to show antitumor effects and activity to accelerate osteoblastic proliferation. Nevertheless, the antitumor mechanism of psoralen in osteosarcoma has never been elucidated. The current study is aimed to investigate the therapeutic function of psoralen in human osteosarcoma cells and its potential regulatory mechanism.MATERIAL AND METHODS: Effects of psoralen (0-70 μg/mL) on the viability of two osteosarcoma cell lines cultured for 48 h was evaluated by MTT assays. The concentration of IC₁₀ (8 μg/mL for MG-63 cells and 9 μg/mL for U2OS cells) was regarded to be a non-cytotoxic dose selected as the working concentration in the subsequent experiments. Effects of psoralen on cell proliferation for 48 h was assessed by colony formation assays. Flow cytometry analyses were performed to measure cell cycle and apoptosis. RT-qPCR and Western blotting were carried out to assess RNA expression and protein levels of endoplasmic reticulum (ER) stress associated factors.
    RESULTS: Psoralen inhibited osteosarcoma cell viability (IC₅₀ 25 μg/mL for MG-63 cells and IC₅₀ 40 μg/mL for U2OS cells) in a dose-dependent manner and growth inhibition rate reached the highest level when cells were treated with 70 μg/mL psoralen. Psoralen induced cell cycle arrest in the G0/G1 phase and promoted apoptosis of both MG-63 and U2OS cells. The treatment of psoralen resulted in an increase in ATF-6 and CHOP protein levels as well as a decrease in Bcl-2 protein level, indicating that cell apoptosis induced by psoralen was associated with ER stress. Treatment with 4-PBA, the ER stress inhibitor, attenuated the ability of psoralen to promote apoptosis of MG-63 and U2OS cells.
    CONCLUSIONS: Psoralen showed growth-inhibitory effects in osteosarcoma cells, and induced apoptosis via the ER stress pathway, which might be a potential drug to suppress the development of osteosarcoma.
    Keywords:  ER stress; Psoralen; apoptosis; cell death; osteosarcoma cells; unfolded protein response
    DOI:  https://doi.org/10.5603/FHC.a2022.0010
  5. Am J Cancer Res. 2022 ;12(2): 729-743
    Preclinical studies with ONC201/TIC10 and lurbinectedin as a novel combination therapy in small cell lung cancer (SCLC).
    Nicholas R Liguori, Ashley Sanchez Sevilla Uruchurtu, Leiqing Zhang, Abbas E Abbas, Young S Lee, Lanlan Zhou, Christopher G Azzoli, Wafik S El-Deiry.
      The American Cancer Society estimates that ~15% of all lung cancers are categorized as small cell lung cancer (SCLC) with an overall five-year survival rate of less than 7%. Due to disease aggressiveness, more other malignancies, the standard of care is based on clinical efficacy rather than helpful biomarkers. Lurbinectedin is a small molecule RNA polymerase II inhibitor that binds the minor groove of DNA to induce double-strand breaks. Lurbinectedin has efficacy towards SCLC cells at sub-nM concentration and received accelerated FDA approval in 2020 for metastatic SCLC that progressed on platinum-based therapy. ONC201/TIC10 is a TRAIL pathway-inducing compound that with demonstrated clinical efficacy in H3K27M-mutated diffuse midline glioma and neuroendocrine tumors, in early phase clinical trials. We hypothesized that combining ONC201 and lurbinectedin may yield synergistic and targeted killing of SCLC cells. SCLC cell lines H1048, H1105, H1882, and H1417 were treated with ONC201 and lurbinectedin and cell viability was determined using a CellTiter-Glo assay using varying drug concentrations. Synergistic growth inhibition of SCLC cells was noted with combination of ONC201 and lurbinectedin. Induction of the integrated stress response mediator ATF4 and CHOP was observed with ONC201 and lurbinectedin along with induction of PARP cleavage indicative of apoptosis in response to cellular stress. Additionally, SCLC lines treated with the combination therapy displayed increased DNA breakage-related proteins such as phosphorylated Chk-1, Wee1 and γ-H2AX. Combination index revealed the most potent synergy occurred at the concentrations of 0.16 μM ONC201 and 0.05 nM lurbinectedin in the H1048 cell line, demonstrating highly efficient and selective killing of these tumor cells in vitro. While these therapies showed potency against the cell lines derived from SCLC patients, it is noteworthy that the combination showed significantly less toxicity to healthy human lung epithelial cells. Future studies could explore the combination of ONC201 and lurbinectedin in SCLC cell lines, SCLC patient-derived organoids, other tumor types, including in vivo studies and clinical translation.
    Keywords:  ONC201; SCLC; TIC10; chemotherapy; genomics; lurbinectedin
  6. Neoplasma. 2022 Mar 10. pii: 211102N1556. [Epub ahead of print]
    Iodine-125 induced cholangiocarcinoma cell death is enhanced by inhibition of endoplasmic reticulum stress-mediated protective autophagy.
    Lei Zou, Wei Chang, Jian-Hua Bai, Wan-Hong Shi, Yun Jin, Jun-Feng Wang, Kun-Hua Wang.
      Cholangiocarcinoma (CCA) is the second most common primary liver malignancy, however, it is difficult to diagnose and treat, and only a few patients with CCA are suitable for surgery. Iodine-125 (I-125) is an effective treatment for cancer, but the molecular mechanisms underlying the effects of I-125 differ among different cancers. This study aimed to explore the effects of I-125 on CCA cell activity and determine the possible mechanisms of action of I-125 in this type of cancer. CCA cell proliferation, cycling, apoptosis, autophagy, and endoplasmic reticulum (ER) stress were determined after irradiation of CCA cells with I-125 seeds. The effects of I-125 on autophagy and ER stress in three CCA cell lines were evaluated using western blotting, while the effects of I-125 on apoptosis and autophagy in QBC939 cells treated with si-Beclin1 or si-PERK, respectively, were assessed using flow cytometry. I-125 suppressed cell viability and induced cell cycle G2/M-phase arrest in three CCA cell lines (QBC939, TFK-1, HuCCT1). I-125 induced apoptosis, autophagy, and ER stress by altering the expression levels of some related proteins in each of the three CCA cell lines. Furthermore, autophagy inhibition (treatment with si-Beclin1) increased expression of apoptosis-related proteins (Cleaved-PARP and Cleaved-caspase-3, Bax/Bcl2) in QBC939 cells irradiated with I-125 seeds, while ER stress inhibition (si-PERK) suppressed the expression of autophagy-related proteins (LC3-I, LC3-II, P62). Therefore, I-125 induces ER stress, thereby activating protective autophagy in CCA cells through the PERK signaling pathway. Combined inhibition of ER stress and autophagy signaling may increase the killing effect of I-125 on cancer cells and serve as a new auxiliary method in I-125 radiotherapy.
    DOI:  https://doi.org/10.4149/neo_2022_211102N1556
  7. Am J Cancer Res. 2022 ;12(2): 521-536
    ONC206 has anti-tumorigenic effects in human ovarian cancer cells and in a transgenic mouse model of high-grade serous ovarian cancer.
    Katherine Tucker, Yajie Yin, Stuart-Allison Staley, Ziyi Zhao, Ziwei Fang, Yali Fan, Xin Zhang, Hongyan Suo, Wenchuan Sun, Varun Vijay Prabhu, Joshua E Allen, Chunxiao Zhou, Victoria L Bae-Jump.
      ONC206, a dopamine receptor D2 (DRD2) antagonist and imipridone, is a chemically modified derivative of ONC201. Recently, ONC206 and other imipridones were identified as activators of the mitochondrial protease ClpP, inducing downstream pathways that allow them to selectively target cancer cells. Clinical trials showed that ONC201, the first in class imipridone, was well tolerated and exhibited tumor regression in some solid tumors. Our goal was to evaluate the effect of ONC206 on cell proliferation and tumor growth in ovarian cancer cell lines and in a transgenic mouse model of high grade serous ovarian cancer (KpB model). ONC206 was more potent than ONC201 in inhibiting cell proliferation, as evidenced by a 10-fold decrease in IC50 for the SKOV3 and OVCAR5 cell lines. This was accompanied by the results that ONC206 significantly inhibited cellular proliferation, induced cell cycle G1 arrest and apoptosis, caused cellular stress, and inhibited adhesion and invasion in vitro. Treatment of obese and non-obese KpB mice with ONC206 elevated Bip and ClpP expression and reduced KI67, BCL-XL and DRD2 expression in the ovarian tumors. Our findings demonstrate that ONC206 has anti-tumorigenic effects in ovarian cancer as previously demonstrated by ONC201 but appears to be as well tolerated and more potent. Thus, ONC206 deserves further evaluation in clinical trials.
    Keywords:  ONC206; adhesion/invasion; apoptosis; cell proliferation; ovarian cancer
  8. Biomed Res Int. 2022 ;2022 9329151
    Bixin Prevents Colorectal Cancer Development through AMPK-Activated Endoplasmic Reticulum Stress.
    Yunfeng Qiu, Changfeng Li, Bin Zhang.
      Chemicals isolated from natural products have been broadly applied in the treatment of colorectal cancer (CRC). Bixin, an apocarotenoid from the seeds of Bixa orellana, exerts multiple pharmacological properties, including neuroprotective, anti-inflammatory, cardioprotective, and antitumor effects; yet, the therapeutic effects of Bixin on CRC are still unknown. Here, we described that Bixin treatment significantly inhibited the proliferation and motility of two CRC cell lines (CaCO2 and SW480) in vitro and in vivo. In addition, Bixin administration has sensitized CRC cells to TNF-related apoptosis-inducing ligand- (TRAIL-) induced cell apoptosis. Moreover, we showed that Bixin treatment initiated the activation of PERK/eIF-2α signal in CaCO2 and SW480 cells, leading to endoplasmic reticulum stress-associated apoptosis. Pharmacological inhibition of AMP-activated protein kinase (AMPK) abrogated the Bixin-induced activation of protein kinase RNA-like endoplasmic reticulum kinase (PERK)/eukaryotic initiation factor 2 alpha (eIF-2α) pathway, as well as reversed the inhibitory effects of Bixin on CRC development. In conclusion, this study indicated that Bixin treatment inhibits the progression of CRC through activating the AMPK/PERK/eIF-2α pathway, providing a novel potential strategy for clinical prevention of CRC.
    DOI:  https://doi.org/10.1155/2022/9329151
  9. Int J Mol Sci. 2022 Mar 05. pii: 2858. [Epub ahead of print]23(5):
    Methylmercury Induces Mitochondria- and Endoplasmic Reticulum Stress-Dependent Pancreatic β-Cell Apoptosis via an Oxidative Stress-Mediated JNK Signaling Pathway.
    Ching-Yao Yang, Shing-Hwa Liu, Chin-Chuan Su, Kai-Min Fang, Tsung-Yuan Yang, Jui-Ming Liu, Ya-Wen Chen, Kai-Chih Chang, Haw-Ling Chuang, Cheng-Tien Wu, Kuan-I Lee, Chun-Fa Huang.
      Methylmercury (MeHg), a long-lasting organic pollutant, is known to induce cytotoxic effects in mammalian cells. Epidemiological studies have suggested that environmental exposure to MeHg is linked to the development of diabetes mellitus (DM). The exact molecular mechanism of MeHg-induced pancreatic β-cell cytotoxicity is still unclear. Here, we found that MeHg (1-4 μM) significantly decreased insulin secretion and cell viability in pancreatic β-cell-derived RIN-m5F cells. A concomitant elevation of mitochondrial-dependent apoptotic events was observed, including decreased mitochondrial membrane potential and increased proapoptotic (Bax, Bak, p53)/antiapoptotic (Bcl-2) mRNA ratio, cytochrome c release, annexin V-Cy3 binding, caspase-3 activity, and caspase-3/-7/-9 activation. Exposure of RIN-m5F cells to MeHg (2 μM) also induced protein expression of endoplasmic reticulum (ER) stress-related signaling molecules, including C/EBP homologous protein (CHOP), X-box binding protein (XBP-1), and caspase-12. Pretreatment with 4-phenylbutyric acid (4-PBA; an ER stress inhibitor) and specific siRNAs for CHOP and XBP-1 significantly inhibited their expression and caspase-3/-12 activation in MeHg-exposed RIN-mF cells. MeHg could also evoke c-Jun N-terminal kinase (JNK) activation and reactive oxygen species (ROS) generation. Antioxidant N-acetylcysteine (NAC; 1mM) or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox; 100 μM) markedly prevented MeH-induced ROS generation and decreased cell viability in RIN-m5F cells. Furthermore, pretreatment of cells with SP600125 (JNK inhibitor; 10 μM) or NAC (1 mM) or transfection with JNK-specific siRNA obviously attenuated the MeHg-induced JNK phosphorylation, CHOP and XBP-1 protein expression, apoptotic events, and insulin secretion dysfunction. NAC significantly inhibited MeHg-activated JNK signaling, but SP600125 could not effectively reduce MeHg-induced ROS generation. Collectively, these findings demonstrate that the induction of ROS-activated JNK signaling is a crucial mechanism underlying MeHg-induced mitochondria- and ER stress-dependent apoptosis, ultimately leading to β-cell death.
    Keywords:  ER stress; apoptosis; c-Jun N-terminal kinase (JNK); methylmercury; oxidative stress; pancreatic β-cells
    DOI:  https://doi.org/10.3390/ijms23052858
  10. Mol Clin Oncol. 2022 Apr;16(4): 83
    Effects of endoplasmic reticulum stress-mediated CREB3L1 on apoptosis of glioma cells.
    Zhao Yan, Yaxin Hu, Yiwei Zhang, Qian Pu, Liangzhao Chu, Jian Liu.
      The association between endoplasmic reticulum stress (ERS) and apoptosis has been extensively studied. Cyclic adenosine monophosphate responsive element binding protein 3 like 1 (CREB3L1) has an important role in the development of glioma. In the present study, the potential association between ERS-induced apoptosis and CREB3L1 and its clinical implications were investigated. From a total of 30 cases, brain gliomas with different pathological grades surgically resected at the Department of Neurosurgery of the Affiliated Hospital of Guizhou Medical University (Guiyang, China) between January 2018 and January 2019 were collected. The expression of CREB3L1 and ERS-related proteins in gliomas with different degrees of malignancy was detected by immunohistochemistry. Furthermore, U87-MG glioma cells were cultured in vitro and treated with different concentrations of ERS inducer thapsigargin (TG). The Cell Counting Kit-8 (CCK-8) assay was performed to detect changes in cell activity at different incubation times and drug concentrations. Cell apoptosis was detected by Annexin Ⅴ-FITC/propidium iodide double staining and the protein expression levels of CREB3L1 and ERS were detected by western blot analysis. Immunohistochemical analysis suggested that the expression levels of CREB3L1, glucose-regulated protein, 78 kDa (GRP78) and C/EBP-homologous protein (CHOP) in World Health Organization (WHO) grade I glioma were higher than those in WHO grade Ⅱ-Ⅳ (all P<0.01). The results of the CCK-8 assay suggested that the activity of U87-MG glioma cells was significantly decreased after treatment with TG (all P<0.05), and this effect was time- and drug concentration-dependent. Flow cytometric analysis indicated that the apoptotic rate of the cells was increased, which was significant when the concentration of TG was 0.1 µmol/l (P<0.01). Furthermore, the protein expression of CREB3L1, GRP78 and CHOP in glioma cells treated with TG was increased (P<0.05). However, the expression level of Bcl-2 decreased (P<0.05). In conclusion, ERS may reduce the cell proliferative activity and promote apoptosis through mediating CREB3L1 expression. CREB3L1 may be a novel potential target for glioma therapy.
    Keywords:  CREB3L1; U87-MG; apoptosis; endoplasmic reticulum stress; glioma cells; thapsigargin
    DOI:  https://doi.org/10.3892/mco.2022.2516
  11. Phytomedicine. 2022 Feb 18. pii: S0944-7113(22)00085-X. [Epub ahead of print]99 154007
    Flavonoids from Scutellaria barbata D. Don exert antitumor activity in colorectal cancer through inhibited autophagy and promoted apoptosis via ATF4/sestrin2 pathway.
    Lianfang Liu, Tianya Liu, Weiwei Tao, Naikai Liao, Qiuying Yan, Liu Li, Jiani Tan, Weixing Shen, Haibo Cheng, Dongdong Sun.
      PURPOSE: Scutellaria barbata D. Don (SB), mainly containing flavonoids, has been frequently used for cancer treatment. However, little research has investigated the antitumor activity of flavonoids from SB (FSB). The current study aimed to assess the antitumor effect of TFSB and elucidate the probable underlying mechanism in vivo and in vitro.STUDY DESIGN: FSB was prepared, and its chemical composition was characterized by HPLC-MS. Colorectal HCT116 cells were treated with various concentration of FSB. The viability, proliferation, apoptosis, migration, and autophagy of HCT116 cells were studied, as were further confirmed in tumor xenografts.
    METHODS: Cell viability and proliferation were respectively examined by MTT and EdU staining. ROS was determined with DCFH-DA, and cell apoptosis was detected using flow cytometry. Transwell and wound-healing assays were performed to evaluate cell migration. Immunofluorescence was employed to evaluate sestrin2 and ATF4 level. The protein expressions of p-AMPK, p-ULK1, p-mTOR, 4E-BP1, LC3-I/II, cleaved-caspase-3, Bax, and bcl-2 were investigated by western blot. ATF4 was overexpressed in experiments to explore the role of ATF4/sestrin2 pathway in FSB-mediated efficacy.
    RESULTS: FSB clearly reduced the cell viability, promoted ROS generation, and induced apoptosis in HCT116 cells by down-regulated Bcl-2, and increased cleaved-caspase-3 and Bax. Furthermore, FSB significantly inhibited migration of colorectal cells in a dose-dependent manner. Further mechanistic study indicated that FSB upregulated p-mTOR protein level, and reduced p-AMPK, p-ULK1, p-mTOR, p-4E-BP1 and LC3-I/II expression, which were major autophagy-related genes. In addition, FSB could cause downregulation of endogenous mTOR inhibitor sestrin2 and ATF4 expression. Transient overexpression of ATF4 resulted in mTOR and sestrin2 inhibition, and significantly compromised the effects of FSB on apoptosis and autophagy in HCT116 cells.
    CONCLUSION: Our results reveal, for the first time, that FSB exerts antitumor activity through autophagy inhibition and apoptosis induction via ATF4/sestrin2 pathway in colorectal cancer cells. Scutellaria barbata D. Don may have great potential in the application for the prevention and treatment of human colorectal cancer.
    Keywords:  ATF4; Autophagy; Colorectal cancer; Scutellaria barbata D. Don; apoptosis; sestrin2
    DOI:  https://doi.org/10.1016/j.phymed.2022.154007
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