Nutritional optimization for bioprocess production of staphyloxanthin from Staphylococcus aureus with response surface methodology: promising anticancer scaffold targeting EGFR inhibition.

Abstract

Background: Staphyloxanthin (STX) is a secondary metabolite pigment associated with membrane structures, recognized for its significant antioxidant properties. It plays a crucial role in combating reactive oxygen species (ROS), positioning it as a promising and effective alternative in cancer treatment. This study focused on enhancing the production of STX pigment by employing statistical optimization of media components, alongside the evaluation of its safety and anticancer properties.

Results: A total of 59 Staphylococcus aureus isolates were screened and quantitatively estimated for STX production. The best pigment-producing isolate was identified based on molecular phylogenetic analysis as S. aureus A2, with accession number PP197164. A Box-Wilson central composite design was employed to evaluate the intricate interactions among six variables affecting the pigment yield. The most optimal conditions resulted in the highest production of STX of OD₄₅₆ = 0.328, which is approximately 1.5-fold greater than the yield (OD₄₅₆ = 0.215) obtained from OFAT optimization. The final response surface model fitting the data achieved a R² of 0.8748. STX exhibited marked cytotoxicity against the A549 NSCLC cell line with IC50 of 57.3 µg/mL, a safe dose in normal Vero cells. The anticancer activity of STX was predominantly mediated by the apoptotic pathway, as confirmed by confocal microscopy, the annexin V-FITC apoptosis assay, and the overexpression of caspase-3. Moreover, STX disrupted cell cycle at pre-G1 and G0/G1 phases in lung cancer. Intriguingly, STX exhibited its antitumor activity through reducing the EGFR expression. The molecular docking study revealed the potential binding interactions and affinities within the active sites of both wild-type and mutant EGFR.

Conclusion: The bioprocess for optimized production, combined with the biological profiling and low cytotoxicity, substantiates the potential application of STX pigment in combating lung cancer.