Physalin B not only inhibits the ubiquitin-proteasome pathway but also induces incomplete autophagic response in human colon cancer cells in vitro

Abstract

Aim: To investigate the effects of physalin B insolated from Physalis divericata on human colon cancer cells in vitro and its anticancer mechanisms. Methods: Human HCT116 colon cancer cell line was tested. Cell viability and apoptosis were detected, and relevant proteins were measured using Western blot analyses. Autophagosomes were observed in stable GFP-LC3 HCT116 cells. Localization of autophagosomes and lysosomes was evaluated in GFP-LC3/RFP-LAMP1-co-transfected cells. Microtubules and F-actin microfilaments were observed with confocal microscope. Mitochondrial ROS (mito-ROS) was detected with flow cytometry in the cells stained with MitoSox dye. Results: Physalin B inhibited the viability of HCT116 cells with an IC 50 value of 1.35 μmol/L. Treatment of the cells with physalin B (2.5-10 μmol/L) induced apoptosis and the cleavage of PARP and caspase-3. Meanwhile, physalin B treatment induced autophagosome formation, and accumulation of LC3-II and p62, but decreased Beclin 1 protein level. Marked changes of microtubules and F-actin microfilaments were observed in physalin B-treated cells, which led to the blockage of co-localization of autophagosomes and lysosomes. Physalin B treatment dose-dependently increased the phosphorylation of p38, ERK and JNK in the cells, whereas the p38 inhibitor SB202190, ERK inhibitor U0126 or JNK inhibitor SP600125 could partially reduce physalin B-induced PARP cleavage and p62 accumulation. Moreover, physalin B treatment dose-dependently increased mito-ROS production in the cells, whereas the ROS scavenger NAC could reverse physalin B-induced effects, including incomplete autophagic response, accumulation of ubiquitinated proteins, changes of microtubules and F-actin, activation of p38, ERK and JNK, as well as cell death and apoptosis. Conclusion: Physalin B induces mito-ROS, which not only inhibits the ubiquitin-proteasome pathway but also induces incomplete autophagic response in HCT116 cells in vitro.

The Cape Gooseberry Constituent Physalin B Ameliorates Nonalcoholic Steatohepatitis and Attenuates Liver Fibrosis

“…Previous studies have shown that Physalin B induces apoptosis in the human HCT116 colon cancer cell line by inducing autophagosome formation and accumulation of LC3-II and p62, underpinning the finding that Physalin B triggers autophagic cell death [7].…”

ERK: A Double-Edged Sword in Cancer. ERK-Dependent Apoptosis as a Potential Therapeutic Strategy for Cancer

“…ROS-mediated ERK signaling activation may constitute an underlying mechanism functionally connecting apoptosis and autophagy since the NAC treatment canceled both types of cell death associated with several compounds such as Rg5, moursine, physalin B, and derrone. For example, physalin B, a naturally occurring secosteroid, induces mitochondriamediated ROS generation, which leads to the ubiquitin-proteasome pathway inhibition and incomplete non-canonical autophagy response [118]. Autophagosome/lysosome fusion is blocked due to the inhibition of functions of microtubules and F-actin microfilaments, leading to autophagy substrates accumulation which accelerates apoptosis.…”

Apoptotic Pathway as the Therapeutic Target for Anticancer Traditional Chinese Medicines

“…franchetii (Mast). Makino and significantly inhibited cell growth and induced apoptosis by increasing mitochondrial ROS production in human colon cancer HCT-116 cells (Ma Y. M. et al, 2015). Recent studies further showed that Physalin B displayed the ability to inhibit cell proliferation and induce apoptosis in human breast cancer MCF-7 and lung cancer A549 cells (Wang A. et al, 2018; Cao et al, 2019).…”