Daurisoline Inhibits ESCC by Inducing G1 Cell Cycle Arrest and Activating ER Stress to Trigger Noxa-Dependent Intrinsic and CHOP-DR5-Dependent Extrinsic Apoptosis via p-eIF2α-ATF4 Axis

Daurisoline inhibits glycolysis of lung cancer by targeting the AKT-HK2 axis

Lung cancer, one of the most prevalent tumors, remains a clinical challenge with a poor five-year survival rate. Daurisoline, a bis-benzylisoquinoline alkaloid derived from the traditional Chinese herb Menispermum dauricum, is known to suppress tumor growth effectively. However, its precise mechanism of action remains unclear. In this study, we demonstrate that Daurisoline targets glycolysis and reduces the protein level of HK2, thereby inhibiting lung cancer progression. Mechanistic investigations reveal that Daurisoline directly binds to AKT and antagonizes the AKT-GSK3β-c-Myc-HK2 signaling axis. Furthermore, in an animal model, we validate the in vivo anti-tumor effect of Daurisoline without any observable side effects. Overall, our findings suggest that Daurisoline holds potential as an anti-tumor agent through its targeting of glycolysis.

Metformin induces apoptosis in TRAIL-resistant colorectal cancer cells

Resistance to chemotherapy drugs, which commonly occurs during the treatment of colorectal cancer (CRC), can lead to tumor recurrence and metastasis, so combinational treatment strategies according to the cancer cell type are urgently needed to overcome drug resistance and increase therapeutic efficiency. To this end, the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a promising anticancer strategy. Some CRC cell lines such as SW620 have low sensitivity to TRAIL, so additional sensitizers are required to make the strategy effective. Therefore, we focused on the apoptotic effect of combinational metformin and TRAIL treatment on TRAIL-resistant SW620 cells. Treatment with TRAIL alone did not induce apoptosis whereas combined treatment with metformin and TRAIL significantly increased it. TRAIL activated caspases through an extrinsic pathway but increased resistance to apoptosis through the protein kinase B or AKT (PKB/AKT)/mammalian target of rapamycin (mTOR) pathway. On the other hand, metformin reduced the inhibitory effect of X-linked inhibitor of apoptosis (XIAP) by blocking the AKT and nuclear factor kappa B (NF-κB) pathways and activated CCAAT-enhancer-binding protein homologous protein (CHOP) via endoplasmic reticulum (ER) stress but without inducing apoptosis. In addition, metformin induced cell-cycle arrest, thereby blocking cell proliferation and growth. These results were also confirmed through an in vivo mouse xenograft CRC model, in which combined treatment with metformin and TRAIL induced tumor cell death, thus demonstrating the anticancer effect of their coadministration. Therefore, cotreatment of metformin and TRAIL could be an effective anticancer treatment strategy for TRAIL-resistant CRC.

Phytochemical-mediated modulation of autophagy and endoplasmic reticulum stress as a cancer therapeutic approach

Autophagy and endoplasmic reticulum (ER) stress are conserved processes that generally promote survival, but can induce cell death when physiological thresholds are crossed. The pro-survival aspects of these processes are exploited by cancer cells for tumor development and progression. Therefore, anticancer drugs targeting autophagy or ER stress to induce cell death and/or block the pro-survival aspects are being investigated extensively. Consistently, several phytochemicals have been reported to exert their anticancer effects by modulating autophagy and/or ER stress. Various phytochemicals (e.g., celastrol, curcumin, emodin, resveratrol, among others) activate the unfolded protein response to induce ER stress-mediated apoptosis through different pathways. Similarly, various phytochemicals induce autophagy through different mechanisms (namely mechanistic target of Rapamycin [mTOR] inhibition). However, phytochemical-induced autophagy can function either as a cytoprotective mechanism or as programmed cell death type II. Interestingly, at times, the same phytochemical (e.g., 6-gingerol, emodin, shikonin, among others) can induce cytoprotective autophagy or programmed cell death type II depending on cellular contexts, such as cancer type. Although there is well-documented mechanistic interplay between autophagy and ER stress, only a one-way modulation was noted with some phytochemicals (carnosol, capsaicin, cryptotanshinone, guangsangon E, kaempferol, and δ-tocotrienol): ER stress-dependent autophagy. Plant extracts are sources of potent phytochemicals and while numerous phytochemicals have been investigated in preclinical and clinical studies, the search for novel phytochemicals with anticancer effects is ongoing from plant extracts used in traditional medicine (e.g., Origanum majorana). Nonetheless, the clinical translation of phytochemicals, a promising avenue for cancer therapeutics, is hindered by several limitations that need to be addressed in future studies.

METTL16 deficiency attenuates apoptosis through translational control of extrinsic death receptor during nutrient deprivation

METTL16 is a well-characterized m6A methyltransferase that has been reported to contribute to tumorigenesis in various types of cancer. However, the effect of METTL16 on tumor progression under restricted nutrient conditions, which commonly occur in tumor microenvironment, has yet to be elucidated. Herein, our study initially reported the inhibitory effect of METTL16 depletion on apoptosis under amino acid starvation conditions. Mechanistically, we determined that the METTL16 knockdown represses the expression of extrinsic death receptors at both transcription and translation levels. Depletion of METTL16 prevented protein synthesis of GCN2, resulting in diminished ATF4 expression in a GCN2-eIF2α-dependent manner. Reduction of ATF4 further declined the expression of apoptotic receptor protein DR5. Meanwhile, METTL16 deficiency directly hampered protein synthesis of FADD and DR5, thereby impairing apoptosis and promoting cancer cell survival. Taken together, our study provides novel evidence for the involvement of METTL16 in regulating cancer progression, suggesting that METTL16 as a potential therapeutic target for cancer treatment.

Tabersonine Enhances Olaparib Sensitivity through FHL1-Mediated Epithelial-Mesenchymal Transition in an Ovarian Tumor

Ovarian cancer (OVC) is one of the most aggressive gynecological malignancies worldwide. Although olaparib treatment has shown favorable outcomes against the treatment of OVC, its effectiveness remains limited in some OVC patients. Investigating new strategies to improve the therapeutic efficacy of olaparib against OVC is imperative. Our study identified tabersonine, a natural indole alkaloid, for its potential to increase the chemosensitivity of olaparib in OVC. The combined treatment of olaparib and tabersonine synergistically inhibited cell proliferation in OVC cells and suppressed tumor growth in A2780 xenografts. The combined treatment effectively suppressed epithelial-mesenchymal transition (EMT) by altering the expression of E-cadherin, N-cadherin, and vimentin and induced DNA damage responses. Integrating quantitative proteomics, FHL1 was identified as a potential regulator to modulate EMT after tabersonine treatment. Increased expression of FHL1 was induced by tabersonine treatment, while downregulation of FHL1 reversed the inhibitory effects of tabersonine on OVC cells by mediating EMT. In vivo findings further reflected that the combined treatment of tabersonine and olaparib significantly inhibited tumor growth and OVC metastasis through upregulation of FHL1. Our findings reveal the role of tabersonine in improving the sensitivity of olaparib in OVC through FHL1-mediated EMT, suggesting that tabersonine holds promise for future application in OVC treatment.

Daurisoline inhibits proliferation, induces apoptosis, and enhances TRAIL sensitivity of breast cancer cells by upregulating DR5

Daurisoline (DS) is an isoquinoline alkaloid that exerts anticancer activities in various cancer cells. However, the underlying mechanisms through which DS affects the survival of breast cancer cells remain poorly understood. Therefore, the present study was undertaken to investigate the potential anticancer effect of DS on breast cancer cells and reveal the mechanism underlying the enhanced tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis by DS. Cell counting kit-8 (CCK-8) and 5-ethynyl-2-deoxyuridine (EdU) assay were used to evaluate the ability of cell proliferation. Flow cytometry was selected to examine the cell cycle distribution. TUNEL assay was used to detect the cell apoptosis. The protein expression was measured by Western blot analysis. DS was found to reduce the cell viability and suppress the proliferation of MCF-7 and MDA-MB-231 cells by causing G1 phase cell cycle arrest. DS could trigger apoptosis by promoting the cleavage of caspase-8 and PARP. The phosphorylation of ERK, JNK, and p38MAPK was upregulated clearly following DS treatment. Notably, SP600125 (JNK inhibitor) pretreatment significantly abrogated DS-induced PARP cleavage. DS inactivated Akt/mTOR and Wnt/β-catenin signaling pathway and upregulated the expression of ER stress-related proteins. Additionally, DS amplified TRAIL-caused viability reduction and apoptosis in breast cancer cells. Mechanismly, DS upregulated the protein level of DR4 and DR5, and knockdown of DR5 attenuated the cotreatment-induced cleavage of PARP. Inhibition of JNK could block DS-induced upregulation of DR5. This study provides valuable insights into the mechanisms of DS inhibiting cell proliferation, triggering apoptosis, and enhancing TRAIL sensitivity of breast cancer cells.

A review on the mechanisms underlying the antitumor effects of natural products by targeting the endoplasmic reticulum stress apoptosis pathway

Cancer poses a substantial risk to human life and wellbeing as a result of its elevated incidence and fatality rates. Endoplasmic reticulum stress (ERS) is an important pathway that regulates cellular homeostasis. When ERS is under- or overexpressed, it activates the protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK)-, inositol-requiring enzyme 1 (IRE1)- and activating transcription Factor 6 (ATF6)-related apoptotic pathways to induce apoptosis. Tumor cells and microenvironment are susceptible to ERS, making the modulation of ERS a potential therapeutic approach for treating tumors. The use of natural products to treat tumors has substantially progressed, with various extracts demonstrating antitumor effects. Nevertheless, there are few reports on the effectiveness of natural products in inducing apoptosis by specifically targeting and regulating the ERS pathway. Further investigation and elaboration of its mechanism of action are still needed. This paper examines the antitumor mechanism of action by which natural products exert antitumor effects from the perspective of ERS regulation to provide a theoretical basis and new research directions for tumor therapy.

Combination therapy with HSP90 inhibitors and piperlongumine promotes ROS-mediated ER stress in colon cancer cells

Colon cancer is a major cause of cancer-related death. Despite recent improvements in the treatment of colon cancer, new strategies to improve the overall survival of patients are urgently needed. Heat shock protein 90 (HSP90) is widely recognized as a promising target for treating various cancers, including colon cancer. However, no HSP90 inhibitor has been approved for clinical use due to limited efficacy. In this study, we evaluated the antitumor activities of HSP90 inhibitors in combination with piperlongumine in colon cancer cells. We show that combination treatment with HSP90 inhibitors and piperlongumine displayed strong synergistic interaction in colon cancer cells. These agents synergize by promoting ER stress, JNK activation, and DNA damage. This process is fueled by oxidative stress, which is caused by the accumulation of reactive oxygen species. These studies nominated piperlongumine as a promising agent for HSP90 inhibitor-based combination therapy against colon cancer.