Pristimerin Exacerbates Cellular Injury in Conditionally Reprogrammed Patient-Derived Lung Adenocarcinoma Cells by Aggravating Mitochondrial Impairment and Endoplasmic Reticulum Stress through EphB4/CDC42/N-WASP Signaling

Abstract

<jats:p>Lung cancer is the most common and lethal malignant disease for which the development of efficacious chemotherapeutic agents remains an urgent need. Pristimerin (PRIS), a natural bioactive component isolated from various plant species in the Celastraceae and Hippocrateaceae families, has been reported to exhibit outstanding antitumor effects in several types of cells. However, the underlying mechanisms involved remain poorly understood. Here, we reported the novel finding that PRIS significantly suppressed lung cancer growth in conditionally reprogrammed patient-derived lung adenocarcinoma cells (CRLCs). We demonstrated that PRIS inhibited the cell viabilities, migrative and invaded abilities, and capillary structure formation of CRLCs. Furthermore, our results clarified that PRIS induced mitochondrial dysfunction through reactive oxygen species (ROS) generation, activation of caspase-9, caspase-3, and caspase-4, and expression of endoplasmic reticulum (ER) stress-associated proteins. Inhibition of ER stress by 4-PBA (4-phenylbutyric acid, a specific ER stress inhibitor) or CHOP siRNA transfection ameliorated PRIS-induced loss of mitochondrial membrane potential and intrinsic apoptosis. The present study also provides mechanistic evidence that PRIS suppressed the EphB4/CDC42/N-WASP signaling pathway, which is required for mitochondrial-mediated intrinsic apoptosis, activation of ER stress, and stimulation of caspase-4 induced by PRIS, and consequently resulting in suppressed cell viability, migration, and angiogenesis in CRLCs. Taken together, by providing a mechanistic insight into the modulation of ER stress-induced cell death in CRLCs by PRIS, we suggest that PRIS has a strong potential of being a new antitumor therapeutic agent with applications in the fields of human lung adenocarcinoma.</jats:p>

Cellular and Molecular Mechanisms of Pristimerin in Cancer Therapy: Recent Advances

“…In the mitochondrial pathway, cytochrome-c, Apaf-1, and other apoptotic factors are released into cytoplasm due to the elevated mitochondrial permeability (58,59), which is preceded caspase activation and cell apoptosis (53). The translocation of cytochrome-c from mitochondria into cytoplasm has been observed under pristimerin administration in CRLC (19), CML (43), breast cancer (49), HCC (51), glioma (52), prostate cancer (55), cervical cancer (56), and pancreatic cancer (60). Wu et al have shown that pristimerin can induce cytochrome-c release through a direct action on mitochondria (49).…”

“…In CRLCs, pristimerin upregulated the levels of Bax, whereas downregulated the levels of Bcl-2 and BIRC6. As a result, cytochrome-c was released from mitochondria accompanied by the attenuation of MMP, eventually intensifying the pristimerin-induced mitochondrial apoptotic pathway (19). Zhang et al have revealed that in treatment with pristimerin, the decline of XIAP and survivin rather than Bcl-2 and Bcl-xL can be observed in UM cells (30).…”

“…Hitomi et al have found that caspase-4 is primarily activated in ER stress-induced apoptosis and causes the activation of caspase-9 (73). Pristimerin has been reported to induce the cleavage and activation of caspase-4 in CRLCs (19). The knockdown of caspase-9 and caspase-3 did not affect caspase-4 activity, whereas the inhibition of caspase-4 abrogated the activation of caspase-9 and caspase-3 (19), suggesting the critical role of caspase-4 in pristimerin-induced caspase cascade.…”

“…As modulators of the tumor microenvironment, the matrix metalloproteinases (MMPs) play a significant role in carcinoma progression (85). Mounting evidence has shown that pristimerin can downregulate the levels of MMP2 and MMP9, indicating the inhibition of cell migration in H1299 lung cancer cells (29), esophageal squamous cell carcinoma (ESCC) cells ( 86), UM cells (30), and CRLCs (19). Additionally, pristimerin has been found to decrease the expression of vimentin, F-actin, integrinb1, and other cytoskeleton polymers, which are essential in cell migration and adhesion process in H1299 lung cancer cells (29).…”

“…It has been reported that pristimerin exhibits many biological effects, such as insecticidal (11), antiinflammatory (12), anti-angiogenic (13), anti-bacterial (14), antiviral (15), anti-fungal (16) and anti-tumor effects (9). Pristimerin exhibits pharmacological effects against tumors through different targets and signal transduction pathways, including sonic hedgehog (Shh)/glioma-associated oncogene homolog 1 (Gli1) (17), phosphatidylinositol 3-kinase (PI3K)/Akt (18), erythropoietin-producing hepatoma receptor B4 (EphB4)/ CDC42/neural Wiskott-Aldrich syndrome protein (N-WASP) (19), nuclear factor-kappaB (NF-kB) (20), reactive oxygen species (ROS)/mitogen-activated protein kinase (MAPK) (21), Wnt/b-catenin (22), insulin-like growth factor type 1 receptor (IGF-1R) (23), and hypoxia inducible factor 1a (HIF-1a)/ sphingosine kinase 1 (SPHK1) (24)pathways as well as micro RNA (9), proteasome (25) and telomerase (26). Pristimerin suppresses cancer cell proliferation via G1 phase arrest (27), apoptosis (28) and autophagy induction (21).…”