Magnolol as a Radiotherapy Enhancer in Oral Squamous Cell Carcinoma: Targeting the EGFR/NF-κB Pathway and Immune Modulation

Abstract

Oral cancer, particularly oral squamous cell carcinoma (OSCC), often exhibits resistance to standard treatments like surgery, chemotherapy, and radiation therapy (RT). Magnolol, a bioactive compound from the bark of Magnolia officinalis, is recognised for its anti-inflammatory, antioxidant, antimicrobial, and antitumor properties. This study aims to explore magnolol's potential to enhance the therapeutic efficacy of RT in oral cancer models. Using MOC1-bearing animals, we evaluated the combined effect of magnolol and RT. The results showed that magnolol significantly suppressed tumour growth, delayed progression, and reduced tumour weight compared to control groups. Immune profiling revealed that magnolol plus RT promoted positive immune regulation by increasing M1 macrophages, dendritic cells, and activated cytotoxic T cells, while suppressing negative regulators like myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). Immunohistochemical analysis also demonstrated enhanced activation of apoptosis-related pathways including the cleavage of caspase-3, -8, and -9. Furthermore, the combination of magnolol and RT did not induce significant toxicity, as evidenced by stable body weight, normal tissue pathology, and normal liver and kidney function markers. Notably, the phosphorylation levels of EGFR and NF-κB were significantly reduced in the magnolol plus RT group, similar to the effects seen with erlotinib plus RT. In conclusion, these findings highlight magnolol's ability to enhance the efficacy of RT in oral cancer by targeting the EGFR/NF-κB axis, inducing apoptosis, and modulating immune responses, presenting a promising therapeutic strategy for OSCC.

Keywords: EGFR/NF‐κB; immunoregulation; magnolol; oral squamous cell carcinoma; radiotherapy.

FIGURE 1

Treatment efficacy of Magnolol combined with RT on MOC1 bearing tumour. (A) Experimental flow chart for the animal study. (B) Tumour volume was measured every two days. (C) Tumour weight was recorded on day 24, and (D) tumour progression for each group of mice is shown. (E) Images of the extracted tumours are presented (n = 5). (F, G) The IHC staining patterns and corresponding quantification data of cleaved caspase‐3, −8, and −9 from the mouse tumours are presented.

FIGURE 2

No apparent general toxicity was observed in Magnolol combined with RT treatment. (A) Body weight was recorded every two days across all treatment groups. Serum levels of (B) γGT, (C) AST, and (D) ALT, representing liver function, are shown. (E) Serum levels of CREA, representing kidney function, are also presented. Gray area represented as the normal level of different factors. (F) H&E staining on various organs after different treatments are presented.

FIGURE 3

Promoted positive immune regulation was observed in Magnolol combined with RT treatment. (A) M1 macrophages (CD11b⁺/CD86⁺) in bone marrow (BM) and (B) spleen (SP) were analysed by flow cytometry. CTLs (CD8⁺/IFN‐γ⁺) in SP and (C–E) CTLs (CD8⁺/IL‐2⁺, CD8⁺/IFN‐γ⁺, and CD8⁺/IL‐2⁺/IFN‐γ⁺) in tumour‐draining lymph nodes (TDLN) were observed using flow cytometry. (F, G) CTLs (CD8⁺/IL‐2⁺ and CD8⁺/IL‐2⁺/IFN‐γ⁺) in tumour‐infiltrating lymphocytes (TIL) were also assessed by flow cytometry. (H, I, J) CD11c⁺/CD83⁺/MHC‐II⁺ dendritic cells (DCs) in SP, TDLN, and TIL were measured using flow cytometry. (K) The IHC staining patterns and corresponding quantification data of CD86 and CD8 from the mouse tumours are presented.

FIGURE 4

Suppressed negative immune regulation was detected in Magnolol combined with RT treatment. (A) MDSCs (CD11b⁺/Gr‐1⁺) in BM and SP were analysed by flow cytometry. (C, D) Tregs (CD4⁺/CD25⁺/FOXP3⁺) in SP and TIL were measured using flow cytometry. (E–G) The IHC staining patterns and corresponding quantification data of FOXP3, CD206, IDO and VEGF from the mouse tumours are presented.

FIGURE 5

Inactivation of EGFR/NF‐κB axis was observed in Magnolol combined with RT treatment. (A, B) The IHC staining patterns and corresponding quantification data of EGFR (Y1068) and NF‐κB (Ser536) from the mouse tumours are presented.