RESUMO
The mammalian target of rapamycin (mTOR) pathway is abnormally activated in lung cancer. However, the anti-lung cancer effect of mTOR inhibitors as monotherapy is modest. Here, we identified that ginsenoside Rh2, an active component of Panax ginseng C. A. Mey., enhanced the anti-cancer effect of the mTOR inhibitor everolimus both in vitro and in vivo. Moreover, ginsenoside Rh2 alleviated the hepatic fat accumulation caused by everolimus in xenograft nude mice models. The combination of everolimus and ginsenoside Rh2 (labeled Eve-Rh2) induced caspase-independent cell death and cytoplasmic vacuolation in lung cancer cells, indicating that Eve-Rh2 prevented tumor progression by triggering paraptosis. Eve-Rh2 up-regulated the expression of c-MYC in cancer cells as well as tumor tissues. The increased c-MYC mediated the accumulation of tribbles homolog 3 (TRIB3)/P62+ aggresomes and consequently triggered paraptosis, bypassing the classical c-MYC/MAX pathway. Our study offers a potential effective and safe strategy for the treatment of lung cancer. Moreover, we have identified a new mechanism of TRIB3/P62+ aggresomes-triggered paraptosis and revealed a unique function of c-MYC.
RESUMO
OBJECTIVE Programmed death ligand-1 (PD-L1) and indoleamine 2, 3-dioxygenase 1 (IDO1) are immune checkpoints which can be induced by interferon-γ(IFN-γ) in the tumor microenvironment, leading to immune escape of tumors. Myricetin (MY) is a flavonoid distributed in many edible and medicinal plants. The aim of this study is to clarify the effect and the mechanism of MY on inhibiting IFN-γ-induced PD-L1 and IDO1 in lung cancer cells. METHODS Expressions of PD-L1 and major histocompatibility complex-I (MHC-I) were evaluated by flow cytometry and Western blotting, and the expression of IDO1 was measured by Western blotting. qRT-PCR was used to detect their mRNA levels. The function of T cells was evaluated using a co-culture system consist of lung cancer cells and the Jurkat-PD-1 T cell line that overexpressing PD-1. Molecular docking analysis, Western blotting and immunofluorescence were used for mechanism study. RESULTS MY potently inhibited IFN-γ-induced PD-L1 and IDO1 expression in human lung cancer cells, while didn't show obvious effect on the expression of MHC-I. In addition, MY restored the survival, proliferation, CD69 expression and interleukin-2 (IL-2) secretion of Jurkat-PD-1 T cells suppressed by IFN-γ-treated lung cancer cells in the co-culture system. Mechanistically, IFN-γ up-regulated PD-L1 and IDO1 at the transcriptional level through the JAK-STAT-IRF1 axis, which was targeted and inhibited by MY. CONCLUSION Our research revealed a new insight into the anti-tumor effects of MY which inhibited IFN-γ-induced PD-L1 and IDO1 expression, supporting the potential of MY in anti-tumor immunotherapy.
RESUMO
Nagilactone E (NLE), a natural product with anticancer activities, is isolated from Podocarpus nagi. In this study, we reported that NLE increased programmed death ligand 1 (PD-L1) expressions at both protein and mRNA levels in human lung cancer cells, and enhanced its localization on the cell membrane. Mechanistically, NLE increased the phosphorylation and expression of c-Jun, and promoted the localization of c-Jun in the nucleus, while silencing of c-Jun by small interfering RNA (siRNA) reduced NLE-induced PD-L1. Further study showed that NLE activated the c-Jun N-terminal kinases (JNK), the upstream of c-Jun, and its inhibitor SP600125 reversed the NLE-increased PD-L1. Moreover, NLE-induced PD-L1 increased the binding intensity of PD-1 on the cell surface. In summary, NLE upregulates the expression of PD-L1 in lung cancer cells through the activation of JNK-c-Jun axis, which has the potential to combine with the PD-1/PD-L1 antibody therapies in lung cancer.