The active components and drug targets of A. crenata
The samples of A. crenata were analyzed by UPLC-Q-TOF/MS. According to the mass spectrum information of the samples, combined with the high-resolution mass database of natural products and related literature, 17 compounds were identified from A. crenata root samples. Nine of the main components (Bergenin, Ardipusilloside I, Ardisicrenoside B, Ardisicrenoside A, Ardisiacrispin A, Ardisiacrispin B, Lauryldiethanolamine, Rapanone, Embinin, Embelin and Norbergenin) were imported into SwissTargetPrediction, BATMAN-TCM and SymMap v2 databases. After deleting duplicates, 273 targets of A. crenata were screened (Figure. 1).
The core targets of A. crenata anti-HNSCC
The key words ‘Head and neck squamous cell carcinoma’ were retrieved in Gene Cards and OMIM database, after removing the duplicate targets, 5,536 HNSCC-related targets were obtained. The targets of A. crenata and diseases were intersected in Venny2.1 (Figure. 2A), and the result showed that there were 163 effective targets of A. crenata anti-HNSCC.
Based on the interaction relationship of the intersected proteins obtained from the STRING database, there are 162 nodes and 2,018 edges in the interaction network diagram, and the average node degree is 24.9. The data was visualized in Cytoscape, The nodes in the PPI network (Figure. 2B) represent all proteins produced by a single protein-coding gene locus, and the edges represent the protein-protein interaction relationship. The size of the node means the Degree value and is proportionate to its pharmacological effect. According to the Degree algorithm of CytoHubba, finally 10 key targets were obtained, including AKT1, GAPDH, TP53, SRC, IL6, CASP3, EGFR, CCND1, STAT3, and ESR1 (Figure. 2C).
GO and KEGG enrichment analysis
GO and KEGG enrichment analysis was conducted in the DAVID database, and GO enrichment obtained a total of 213 items (FDR < 0.01), including 196 biological process (BP), 44 cell composition (CC), and 61 molecular function (MF) items. In the 10 most significant potential targets anti-HNSCC, five targets were related to biological processes, including response to drug, response to xenobiotic stimulus, positive regulation of MAP kinase activity, excitatory postsynaptic potential, positive regulation of cell proliferation; three targets related to cell composition, including integral component of plasma membrane, postsynaptic membrane, plasma membrane; two of them related to molecular functions, which are neurotransmitter receptor activity and identical protein binding (Figure. 3A).
A total of 109 KEGG pathways were enriched (P < 0.01), and the top 20 signal pathways were screened out (Figure. 3B). The results showed that the potential targets of A. crenata anti-HNSCC were enriched in pathways in cancer, prostate cancer, neuroactive ligand-receptor interaction, PI3K-AKT signaling pathway, p53 signaling pathway, EGFR tyrosine kinase inhibitor resistance and endocrine resistance.
Survival analysis and verification of core genes
The significance of expression levels of the key genes in the clinical survival of HNSCC patients was verified in the TISIDB database. After screening (Log-rank P < 0.05), a total of five genes, GAPDH, AKT1, CCND1, SRC, and ESR1, were proved to affect the prognosis and survival of HNSCC patients (Figure. 4A). The protein expression levels of core genes were obtained from TIMER database and compared between normal and HNSCC tissues. The results showed the expressions of GAPDH, AKT1 and SRC were significantly different between normal and HNSCC tissues (Figure. 4B).
Molecular docking analysis
Bergenin, the main active component of A. crenata was selected for molecular docking with the target proteins that affected the prognosis of HNSCC. Molecular docking showed (Figure. 5) that the binding energy of bergenin with GAPDH (5jy6), AKT1 (4ejn), CCND1 (2w96), SRC (4u5j) and ESR1 (6psj) were − 7.7, -8.7, -6.9, -7.7 and − 7.8 kcal/mol, respectively. The results indicated the binding activity of bergenin and the core target was good and the screening results were reliable.
The effect of A. crenata on FaDu cells and PI3K/AKT pathway
The effect of A. crenata water extract on the activity of FaDu cells was detected by CCK-8. compared with the control group, FaDu cells treated with different concentrations of A. crenata water extract (0, 5, 10, 20µg/mL) showed lower cell survival rate, and the effect of A. crenata water extract had concentration and time dependence (Figure. 6A). Western blot analysis showed that compared with the blank control group, different concentrations of A. crenata water extract (0, 5, 10, 20µg/mL) treated FaDu cells could inhibit the protein expression of P-PI3K and P-AKT (P < 0.05), and the inhibitory effect was proportionate to the concentration (Figure. 6B).