Acetyl-11-keto-beta-boswellic acid inhibits cell proliferation and growth of oral squamous cell carcinoma via RAB7B-mediated autophagy

Natural products can overcome the limitations of conventional chemotherapy. Acetyl-11-keto-beta-boswellic acid (AKBA) as a natural product extracted from frankincense, exhibited chemotherapeutic activities in different cancers. However, whether AKBA exerts inhibiting effect of oral squamous cell carcinoma (OSCC) cells growth and the mechanism need to be explored. We attempted to investigate the therapeutic effects of AKBA against OSCC and explore the mechanism involved. Here we attempt to disclose the cell-killing effect of AKBA on OSCC cell lines and try to figure out the specifical pathway. The presence of increase autophagosome and the production of mitochondrial reactive oxygen species were confirmed after the application of AKBA on OSCC cells, and RAB7B inhibition enhanced autophagosome accumulation. Though the increase autophagosome was detected induced by AKBA, autophagic flux was inhibited as the failure fusion of autophagosome and lysosome. Cal27 xenografts were established to verify the role of anti-OSCC cells of AKBA in vivo. Based above findings, we speculate that natural product AKBA suppresses OSCC cells growth via RAB7B-mediated autophagy and may serve as a promising strategy for the therapy of OSCC.

Chloroform extract and acetyl-11-keto-beta-boswellic acid from Boswellia dalzielii stem bark induce apoptosis and cell cycle blockage in AW8507 cells

BACKGROUND

Globally, head and neck cancer is the sixth most common cancer. Despite the advancement in treatment, drug resistance remains a major cause for setback. In an earlier work, the authors reported that Boswellia dalzielii (Hutch) stem bark exhibited dose-dependent cytotoxicity in head and neck cancer cells, AW8507. Therefore, the cell death induction effect of Boswellia dalzielii stem bark chloroform extract in head and neck cancer cell line, AW8507, and its derived constituent on cell cycle and apoptosis proteins was further investigated.

METHODS

The cell death induction activity of the Boswellia dalzielii stem bark chloroform fraction (CLBD) in AW8507 was determined using Annexin V-FITC/PI staining in flow cytometry. High-performance liquid chromatography-mass spectrometry was employed for compounds analysis of the CLBD, and reverse virtual screening was used to identify the mechanism of action of the compound, acetyl-11-keto-beta-boswellic acid, that was elucidated in the Boswellia dalzielii chloroform fraction.

RESULTS

The data obtained showed that Boswellia dalzielii stem bark Chloroform extract increased the percentage of cells presenting for early apoptosis from 4.14 to 10.10% in AW8507 cells. High-performance liquid chromatography-mass spectrometry analysis of the chloroform fraction identified acetyl-11-keto-beta-boswellic acid. Reverse virtual screening on selected proteins showed that acetyl-11-keto-beta-boswellic acid is a multi-protein target compound. It binds preferably to phosphorylated-cyclin dependent kinase 1 (p-CDK1) (binding score =  - 9.2 kcal/mol), blocking the activation of cyclin B-CDK1 needed for cell cycle progression at G2/M phase of the cell cycle. Acetyl-11-keto-beta-boswellic acid also binds more tightly with αβ tubulin (binding score = 8.9 kcal/mol) than with the standard drug, docetaxel (binding score = 8.3 kcal/mol).

CONCLUSIONS

The results obtained confirmed the culpability of Boswellia dalzielii-derived acetyl-11-keto-beta-boswellic acid in the obstruction of the cell cycle progression in head and neck cancer cell line, AW8507; and the induction of apoptosis earlier reported for Boswellia dalzielii (Hutch) stem bark. Additional in vitro and/or in vivo studies would be required to validate in silico observations.