UNASSIGNED: Breast cancer is the main reason for cancer-related death in women. Britannin is a sesquiterpene lactone compound derived from Inula aucheriana with anti-tumor properties. We aimed to explore the impacts of britannin on apoptosis and autophagy in MCF-7 breast cancer cell line.
UNASSIGNED: The cytotoxic influences of britannin on MCF-7 cells were estimated by the MTT method. The expression levels of apoptosis-associated genes such as CASP3, BCL2, BCL2L1, STAT3, and JAK2 and transcripts of autophagy markers including ATG1, ATG4, ATG5, ATG7, ATG12, BECN1, and MAP1LC3A were quantified using quantitative real time-PCR (qRT-PCR). Western blotting method was used to evaluate the amount of caspase 3, phosphorylated JAK2, phosphorylated STAT3, ATG1, ATG4, ATG5, Beclin1, and LC-III.
UNASSIGNED: Treatment of MCF-7 cells with various concentrations of britannin remarkably hindered the viability of these cells compared to the controls. This compound significantly elevated the expression of pro-apoptotic caspase-3 but did not influence the levels of anti-apoptotic BCL2 and BCL2L1. Britannin decreased the levels of phosphorylated forms of JAK2 and STAT3 proteins causing the blockage of the JAK/STAT pathway. Four autophagy factors expressions, including ATG4, ATG5, Beclin1, and LCIII, were reduced due to the effect of britannin on MCF-7 cells.
UNASSIGNED: Britannin triggered apoptosis in MCF-7 cells by a mechanism that led to the blockade of the JAK/STAT pathway. Moreover, britannin prohibited autophagy in these cancer cells. This may suggest britannin as an agent for the suppression of breast tumors or as an adjutant for the enhancement of anti-breast cancer drugs effect.

Lung cancer is a harmful type of malignancy and the leading cause of cancer-associated mortality. It is therefore imperative to develop novel drugs effective for treating this cancer. The Traditional Chinese Medicine compound Britannin has been previously reported to inhibit the development of certain cancers, such as pancreatic, breast and liver cancer. Moreover, Kruppel-like factor 5 (KLF5) has been identified an on oncogene in lung cancer. In the present study, the possible regulatory effects and underlying mechanism of Britannin in lung cancer were investigated. A549 and 16HBE cells were treated with different concentrations of Britannin. Subsequently, Cell counting kit-8, EdU staining and colony formation assays were used to detect the proliferative ability of these cells. Cell migration was detected by wound healing and Transwell assays, respectively. XF96 extracellular flux analyzer was used to analyze the extent of extracellular acidification and oxygen consumption rate in cells, whereas assay kits were used to detect glucose and lactic acid levels in the cell supernatant. The targeting effect between Britannin and the KLF5 protein was investigated using molecular docking technology. The protein expression levels of KLF5 in cells challenged with Britannin was detected by western blotting. Finally, overexpression of KLF5 in A549 cells was performed before cell proliferation, migration and the glycolysis rate were measured to explore the regulatory effects of Britannin. Britannin was found to inhibit the proliferation, migration and glycolysis of lung cancer cells, during which the protein expression levels of KLF5 were decreased. This suggests that Britannin regulated the expression of KLF5 in A549 cells. Overexpression of KLF5 reversed the inhibitory effects of Britannin on the proliferation, migration and glycolysis in lung cancer cells. In conclusion, these results suggest that Britannin can inhibit cell proliferation, migration and glycolysis by downregulating KLF5 expression in lung cancer cells.

Overactivation of the NLRP3 inflammasomes induces production of pro-inflammatory cytokines and drives pathological processes. Pharmacological inhibition of NLRP3 is an explicit strategy for the treatment of inflammatory diseases. Thus far no drug specifically targeting NLRP3 has been approved by the FDA for clinical use. This study was aimed to discover novel NLRP3 inhibitors that could suppress NLRP3-mediated pyroptosis. We screened 95 natural products from our in-house library for their inhibitory activity on IL-1β secretion in LPS + ATP-challenged BMDMs, found that Britannin exerted the most potent inhibitory effect with an IC50 value of 3.630 µM. We showed that Britannin (1, 5, 10 µM) dose-dependently inhibited secretion of the cleaved Caspase-1 (p20) and the mature IL-1β, and suppressed NLRP3-mediated pyroptosis in both murine and human macrophages. We demonstrated that Britannin specifically inhibited the activation step of NLRP3 inflammasome in BMDMs via interrupting the assembly step, especially the interaction between NLRP3 and NEK7. We revealed that Britannin directly bound to NLRP3 NACHT domain at Arg335 and Gly271. Moreover, Britannin suppressed NLRP3 activation in an ATPase-independent way, suggesting it as a lead compound for design and development of novel NLRP3 inhibitors. In mouse models of MSU-induced gouty arthritis and LPS-induced acute lung injury (ALI), administration of Britannin (20 mg/kg, i.p.) significantly alleviated NLRP3-mediated inflammation; the therapeutic effects of Britannin were dismissed by NLRP3 knockout. In conclusion, Britannin is an effective natural NLRP3 inhibitor and a potential lead compound for the development of drugs targeting NLRP3.

Sesquiterpene lactones (SLs) are abundant in plants and display a large spectrum of bioactivities. The compound britannin (BRT), found in different Inula species, is a pseudoguaianolide-type SL equipped with a typical and highly reactive α-methylene-γ-lactone moiety. The bioproperties of BRT and related pseudoguaianolide SLs, including helenalin, gaillardin, bigelovin and others, have been reviewed. Marked anticancer activities of BRT have been evidenced in vitro and in vivo with different tumor models. Three main mechanisms are implicated: (i) interference with the NFκB/ROS pathway, a mechanism common to many other SL monomers and dimers; (ii) blockade of the Keap1-Nrf2 pathway, with a covalent binding to a cysteine residue of Keap1 via the reactive α-methylene unit of BRT; (iii) a modulation of the c-Myc/HIF-1α signaling axis leading to a downregulation of the PD-1/PD-L1 immune checkpoint and activation of cytotoxic T lymphocytes. The non-specific reactivity of the α-methylene-γ-lactone moiety with the sulfhydryl groups of proteins is discussed. Options to reduce or abolish this reactivity have been proposed. Emphasis is placed on the capacity of BRT to modulate the tumor microenvironment and the immune-modulatory action of the natural product. The present review recapitulates the anticancer effects of BRT, some central concerns with SLs and discusses the implication of the PD1/PD-L1 checkpoint in its antitumor action.

BACKGROUND: Britannin, a Sesquiterpene Lactone isolated from Inula aucheriana, has recently gained attraction in the therapeutic fields due to its anti-tumor properties. This study was designed to evaluate the effect of this agent on Acute Lymphoblastic Leukemia (ALL) cell lines, either as a monotherapy or in combination with Vincristine (VCR).
RESULTS: To determine the anti-leukemic effects of Britannin on ALL-derived cell lines and suggest a mechanism of action for the agent, we used MTT assay, Annexin-V/PI staining, ROS assay, and real-time PCR analysis. Moreover, by using a combination index (CI), we evaluated the synergistic effect of Britannin on Vincristine. We found that unlike normal Peripheral Blood Mononuclear Cells (PBMCs) and L929 cells, Britannin reduced the viability of NALM-6, REH, and JURKAT cells. Among tested cells, NALM-6 cells had the highest sensitivity to Britannin, and this agent was able to induce p21/p27-mediated G1 cell cycle arrest and Reactive Oxygen Specious (ROS)-mediated apoptotic cell death in this cell line. When NALM-6 cells were treated with Nacetyl-L-Cysteine (NAC), a scavenger of ROS, Britannin could induce neither apoptosis nor reduce the survival of the cells suggesting that the cytotoxic effect of Britannin is induced through ROS-dependent manner. Moreover, we found that a low dose of Britannin enhanced the effect of Vincristine in NALM-6 cells by inducing apoptotic cell death via altering the expression of apoptotic-related genes.
CONCLUSIONS: Overall, our results proposed a mechanism for the cytotoxic effect of Britannin, either as a single agent or in combination with Vincristine, in NALM-6 cells.

BACKGROUND: Programmed cell death-ligand 1 (PD-L1) is overexpressed in tumor cells, which causes tumor cells to escape T cell killing, and promotes tumor cell survival, cell proliferation, migration, invasion, and angiogenesis. Britannin is a natural product with anticancer pharmacological effects.
OBJECTIVE: In this work, we studied the anticancer potential of britannin and explored whether britannin mediated its effect by inhibiting the expression of PD-L1 in tumor cells.
METHODS: In vitro, the mechanisms underlying the inhibition of PD-L1 expression by britannin were investigated by MTT assay, homology modeling and molecular docking, RT-PCR, western blotting, co-immunoprecipitation, and immunofluorescence. The changes in tumor killing activity, cell proliferation, cell cycle, migration, invasion, and angiogenesis were analyzed by T cell killing assays, EdU labeling, colony formation, flow cytometry, wound healing, matrigel transwell invasion, and tube formation, respectively. In vivo, the antitumor activity of britannin was evaluated in the HCT116 cell xenograft model.
RESULTS: Britannin reduced the expression of PD-L1 in tumor cells by inhibiting the synthesis of the PD-L1 protein but did not affect the degradation of the PD-L1 protein. Britannin also inhibited HIF-1α expression through the mTOR/P70S6K/4EBP1 pathway and Myc activation through the Ras/RAF/MEK/ERK pathway. Mechanistically, britannin inhibited the expression of PD-L1 by blocking the interaction between HIF-1α and Myc. In addition, britannin could enhance the activity of cytotoxic T lymphocytes and inhibit tumor cell proliferation and angiogenesis by inhibiting PD-L1. Finally, in vivo observations were confirmed by demonstrating the antitumor activity of britannin in a murine xenograft model.
CONCLUSIONS: Britannin inhibits the expression of PD-L1 by blocking the interaction between HIF-1α and Myc. Moreover, britannin stabilizes T cell activity and inhibits proliferation and angiogenesis by inhibiting PD-L1 in cancer. The current work highlights the anti-tumor effect of britannin, providing insights into the development of cancer therapeutics via PD-L1 inhibition.

Britannin (Bri), isolated from Inula aucheriana, is a sesquiterpene lactone (SL), a class of secondary metabolites. Previous studies have suggested the anti-cancer potential of Bri; however, the molecular mechanism remains elusive. The present study investigated the effects of Bri on liver cancer progression. Our findings indicated that Bri significantly suppressed the growth of liver cancer cell lines. Mechanistic researches revealed that Bri induced apoptosis through the extrinsic and intrinsic apoptotic pathways, as evidenced by the increase of Caspase-8, -9 and -3 cleavages. In addition, Bri-triggered autophagy in liver cancer cells, supported by the up-regulation of light chain 3 (LC3) II, p62, autophagy-related 5 (ATG5) and Beclin 1, as well as the occurrence of autophagic vacuoles. Importantly, Bri increased AMPK activation, while decreased the activity of its down-streaming signal, mTOR. Of note, suppression of AMP-activated protein kinase (AMPK) activation using its inhibitor, Compound C, could inhibit both apoptosis and autophagy induced by Bri. Furthermore, Bri was found to induce reactive oxygen species (ROS) generation in hepatic cancer cells. Notably, reducing ROS production by its scavenger, N-acetyl cysteine (NAC), could down-regulate p-AMPK levels, while up-regulate the phosphorylated mechanistic target of rapamycin (p-mTOR) expressions, accompanied with the restored cell viability, as well as the reduced apoptosis and autophagy in Bri-treated liver cancer cells. Finally, Bri inhibited the tumor growth in vivo without side effects. In conclusion, our study illustrated that Bri could induce apoptosis and autophagy by activating AMPK regulated by ROS in liver cancer cells, supplying molecular bases for developing Bri into an effective candidate against liver cancer.

Induction of apoptosis in cancerous cells is considered as a promising treatment option for cancer therapy. The present study was designed to evaluate the anticancer properties of Britannin and its possible mechanisms of action in human pancreatic cancer cells. Apoptosis induction by Britannin was confirmed by annexin V-FITC/PI staining, Hoechst 33258 staining and caspase-3 activity assay in both AsPC-1 and Panc-1 cells. Additionally, by using western blot and Real-time PCR, we observed that Britannin induced apoptosis by decreasing the expression of BCL-2 and increasing the expression of BAX. Moreover, Britannin increased reactive oxygen species (ROS) generation in different intracellular sites of pancreatic cancer cells. Using western blot analysis, we observed that Britannin decreased the phosphorylated AKT and induced the nuclear accumulation of FOXO1 and also up regulation of FOXO-responsive target BIM in both pancreatic cancer cell lines. Taken together, we found that Britannin is able to induce mitochondrial apoptotic pathway through ROS production and modulation of the AKT-FOXO1 signaling axis in AsPC-1 and Panc-1 human pancreatic cancer cells. Our results can help to illuminate the molecular mechanisms underlying Britannin-induced cell death in pancreatic cancer cell lines and may potentially serve as an anticancer agent for the treatment of pancreatic cancer.