Background: In traditional Chinese medicine (TCM), frankincense and myrrh are the main components of the antitumor drug Xihuang Pill. These compounds show anticancer activity in other biological systems. However, whether frankincense and/or myrrh can inhibit the occurrence of hepatocellular carcinoma (HCC) is unknown, and the potential molecular mechanism(s) has not yet been determined.
Aim: To predict and determine latent anti-HCC therapeutic targets and molecular mechanisms of frankincense and myrrh in vivo.
Methods: In the present study, which was based on the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (http://tcmspw.com/tcmsp.php), Universal Protein database (http://www.uniprot.org), GeneCards: The Human Gene Database (http://www.genecards.org/) and Comparative Toxicogenomics Database (http://www.ctdbase.org/), the efficacy of and mechanism by which frankincense and myrrh act as anti-HCC compounds were predicted. The core prediction targets were screened by molecular docking. In vivo, SMMC-7721 human liver cancer cells were transplanted as xenografts into nude mice to establish a subcutaneous tumor model, and two doses of frankincense plus myrrh or one dose of an EGFR inhibitor was administered to these mice continuously for 14 d. The tumors were collected and evaluated: the tumor volume and growth rate were gauged to evaluate tumor growth; hematoxylin-eosin staining was performed to estimate histopathological changes; immunofluorescence (IF) was performed to detect the expression of CD31, α-SMA and collagen IV; transmission electron microscopy (TEM) was conducted to observe the morphological structure of vascular cells; enzyme-linked immunosorbent assay (ELISA) was performed to measure the levels of secreted HIF-1α and TNF-α; reverse transcription-polymerase chain reaction (RT-qPCR) was performed to measure the mRNA expression of HIF-1α, TNF-α, VEGF and MMP-9; and Western blot (WB) was performed to determine the levels of proteins expressed in the EGFR-mediated PI3K/Akt and MAPK signaling pathways.
Results: The results of the network pharmacology analysis showed that there were 35 active components in the frankincense and myrrh extracts targeting 151 key targets. The molecular docking analysis showed that both boswellic acid and stigmasterol showed strong affinity for the targets, with the greatest affinity for EGFR. Frankincense and myrrh treatment may play a role in the treatment of HCC by regulating hypoxia responses and vascular system-related pathological processes, such as cytokine-receptor binding, and pathways, such as those involving serine/threonine protein kinase complexes and MAPK, HIF-1 and ErbB signaling cascades. The animal experiment results were verified. First, we found that, through frankincense and/or myrrh treatment, the volume of subcutaneously transplanted HCC tumors was significantly reduced, and the pathological morphology was attenuated. Then, IF and TEM showed that frankincense and/or myrrh treatment reduced CD31 and collagen IV expression, increased the coverage of perivascular cells, tightened the connection between cells, and improved the shape of blood vessels. In addition, ELISA, RT-qPCR and WB analyses showed that frankincense and/or myrrh treatment inhibited the levels of hypoxia-inducible factors, inflammatory factors and angiogenesis-related factors, namely, HIF-1α, TNF-α, VEGF and MMP-9. Furthermore, mechanistic experiments illustrated that the effect of frankincense plus myrrh treatment was similar to that of an EGFR inhibitor with regard to controlling EGFR activation, thereby inhibiting the phosphorylation activity of its downstream targets: the PI3K/Akt and MAPK (ERK, p38 and JNK) pathways.
Conclusion: In summary, frankincense and myrrh treatment targets tumor blood vessels to exert anti-HCC effects via EGFR-activated PI3K/Akt and MAPK signaling pathways, highlighting the potential of this dual TCM compound as an anti-HCC candidate.
Keywords: Frankincense; Hepatocellular carcinoma; Multiple signaling pathways; Myrrh; Network pharmacology; Tumor blood vessels.
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