Safflower Yellow Inhibits Progression of Hepatocellular Carcinoma by Modulating Immunological Tolerance via FAK Pathway

Abstract

Objective: To explore the anti-tumor effect of safflower yellow (SY) against hepatocellular carcinoma (HCC) and the underlying potential mechanism.

Methods: An in vitro model was established by mixing Luc-Hepa1-6 cells and CD3⁺CD8⁺ T cells, followed by adding programmed cell death protein 1 (PD-1) antibody (Anti-mPD-1) with or without SY. The apoptosis was detected by flow cytometry and the level of inflammatory cytokines was determined by enzyme-linked immunosorbent assay. The protein levels of programmed cell death 1 ligand 1 (PD-L1), chemokine ligand (CCL5), C-X-C motif chemokine ligand 10 (CXCL10) were measured by Western blot. An in situ animal model was established in mice followed by treatment with anti-mPD-1 with or without SY. Bioluminescence imaging was monitored with an AniView 100 imaging system. To establish the FAK-overexpressed Luc-Hepa1-6 cells, cells were transfected with adenovirus containing pcDNA3.1-FAK for 48 h.

Results: The fluorescence intensity, apoptotic rate, release of inflammatory cytokines, and CCL5/CXCL10 secretion were dramatically facilitated by anti-mPD-1 (P<0.01), accompanied by an inactivation of PD-1/PD-L1 axis, which were extremely further enhanced by SY (P<0.05 or P<0.01). Increased fluorescence intensity, elevated percentage of CD3⁺CD8⁺ T cells, facilitated release of inflammatory cytokines, inactivated PD-1/PD-L1 axis, and increased CCL5/CXCL10 secretion were observed in Anti-mPD-1 treated mice (P<0.01), which were markedly enhanced by SY (P<0.05 or P<0.01). Furthermore, the enhanced effects of SY on inhibiting tumor cell growth, facilitating apoptosis and inflammatory cytokine releasing, suppressing the PD-1/PD-L1 axis, and inducing the CCL5/CXCL10 secretion in Anti-mPD-1 treated mixture of Luc-Hepa1-6 cells and CD3⁺CD8⁺ T cells were abolished by FAK overexpression (P<0.01).

Conclusion: SY inhibited the progression of HCC by mediating immunological tolerance through inhibiting FAK.

Keywords: Chinese medicine; focal adhesion kinase; hepatocellular carcinoma; programmed cell death protein 1; safflower yellow; tumor microenvironment.