PD-L1 dimerisation induced by biphenyl derivatives mediates anti-breast cancer activity via the non-immune PD-L1–AKT–mTOR/Bcl2 pathway

Recent studies on biphenyl-containing compounds, a type of PD-1/PD-L1 blocker which binds to PD-L1 and induces dimerisation, have focussed on its immune function. Herein, 10 novel biphenyl derivatives were designed and synthesised. The results of the CCK-8 showed that compounds have different anti-tumour activities for tumour cells in the absence of T cells. Particularly, 12j–4 can significantly induce the apoptosis of MDA-MB-231 cells (IC50 = 2.68 ± 0.27 μM). In further studies, 12j–4 has been shown to prevent the phosphorylation of AKT by binding to cytoplasmic PD-L1, which induces apoptosis in MDA-MB-231 cells through non-immune pathways. The inhibition of AKT phosphorylation restores the activity of GSK-3β, ultimately resulting in the degradation of PD-L1. Besides, in vivo study indicated that 12j–4 repressed tumour growth in nude mice. As these biphenyls exert their anti-tumour effects mainly through non-immune pathways, they are worthy of further study as PD-L1 inhibitors.