Polyphyllin I (PPI) purified from Polyphyllarhizomes displays puissant cytotoxicity in many kinds of
cancers. Several researches investigated its anti-
cancer activity. But novel mechanisms are still worth investigation. This study aimed to explore PPI-induced
endoplasmic reticulum (ER) stress as well as the underlying mechanism in
non-small cell lung cancer (NSCLC).
Cell viability or colony-forming was detected by MTT or
crystal violet respectively.
Cell cycle,
apoptosis,
reactive oxygen species (ROS) and
mitochondrial membrane potential were assessed by
flow cytometry.
Gene and
protein levels were evaluated by qRT-
PCR and
immunoblotting respectively.
Protein interaction was determined by
immunoprecipitation or
immunofluorescence assay.
Gene overexpression or silencing was carried out by
transient transfection with
plasmids or small interfering RNAs. The
Cancer Genome Atlas (TCGA) database was used for
Gene Set Enrichment
Analysis (GSEA),
survival analysis,
gene expression statistics or pathway enrichment assay. PPI inhibited the propagation of NSCLC
cells, increased non-viable apoptotic
cells, arrested
cell cycle at G2/
M phase, induced ROS levels but failed to decrease
mitochondrial membrane potential. High levels of
GRP78 indicates poor
prognosis in NSCLC
patients. PPI selectively suppressed
unfolded protein response (UPR)-induced
GRP78 expression, subsequently protected CHOP from
GRP78-mediated
ubiquitination and degradation. We demonstrated that the
natural product PPI, obtained from traditional
herbal medicine, deserves for further study as a valuable candidate for
lead compound in the
chemotherapy of NSCLC.