Background: Nasopharyngeal carcinoma (NPC) is a malignant tumor
associated with Epstein-Barr virus (EBV) infection. Chemoradiotherapy is the
mainstream treatment for locally advanced NPC, and chemotherapeutic drugs are an
indispensable part of NPC treatment. However, the toxic side-effects of
chemotherapy drugs limit their therapeutic value, and new chemotherapy drugs are
urgently needed for NPC. Silvestrol, an emerging natural plant anticancer
molecule, has shown promising antitumor activity in breast cancer, melanoma,
liver cancer, and other tumor types by promoting apoptosis in cancer cells to a
greater extent than in normal cells. However, the effects of silvestrol on NPC
and its possible molecular mechanisms have yet to be fully explored.
Methods: Cell counting kit-8 (CCK-8), cell scratch, flow cytometry,
5-ethynyl-2-deoxyuridine (EdU), and Western blot (WB) assays were used to
evaluate the effects of silvestrol on the cell viability, cell cycle, apoptosis,
and migration of NPC cells. RNA sequencing (RNA-Seq) was used to study the effect
of extracellular signal-regulated kinase (ERK) inhibitors on the cell
transcriptome, and immunohistochemistry (IHC) to assess protein expression levels
in patient specimens. Results: Silvestrol inhibited cell migration and
DNA replication of NPC cells, while promoting the expression of cleaved
caspase-3, apoptosis, and cell cycle arrest. Furthermore, silvestrol altered the
level of ERK phosphorylation. The ERK-targeted inhibitor LY3214996 attenuated
silvestrol-mediated inhibition of NPC cell proliferation but not migration.
Analysis of RNA-Seq data and WB were used to identify and validate the downstream
regulatory targets of silvestrol. Expression of GADD45A, RAP1A, and hexokinase-II
(HK2) proteins was inhibited by silvestrol and LY3214996. Finally, IHC revealed
that GADD45A, RAP1A, and HK2 protein expression was more abundant in cancer
tissues than in non-tumor tissues. Conclusions: Silvestrol inhibits the
proliferation of NPC cells by targeting ERK phosphorylation. However, the
inhibition of NPC cell migration by silvestrol was independent of the Raf-MEK-ERK
pathway. RAP1A, HK2, and GADD45A may be potential targets for the action of
silvestrol.