# Kukoamine B Inhibits EMT in Lung Adenocarcinoma Cells by Regulating Intracellular PD-L1-Mediated p65 Nuclear Translocation

## TL;DR

This study shows how Kukoamine B, a natural compound, can stop lung cancer cells from spreading by blocking a specific protein interaction.

## Contribution

The study reveals a new role for intracellular PD-L1 in lung cancer progression and introduces Kukoamine B as a potential treatment.

## Key findings

- Intracellular PD-L1 promotes lung cancer progression by interacting with p65 and causing EMT.
- Kukoamine B inhibits PD-L1/p65 interaction, preventing p65 nuclear translocation and EMT.
- Blocking this pathway with Kukoamine B reduces cancer cell proliferation and migration.

## Abstract

This study uncovers a novel, non-immune function of intracellular PD-L1 in driving LUAD progression and identifies a promising therapeutic strategy. We demonstrate that intracellular PD-L1 in LUAD cells directly interacts with phosphorylated p65 (p-p65), promoting p65 nuclear translocation and thereby inducing epithelial–mesenchymal transition (EMT) to enhance LUAD progression. Furthermore, we establish that the natural compound Kukoamine B (KuB) acts as a potent inhibitor of this pathway by competitively disrupting the PD-L1/p65 interaction. This blockade prevents p65 nuclear translocation and effectively suppresses EMT, proliferation, and migration in LUAD cells. Our findings reveal a key intracellular mechanism of PD-L1 in LUAD metastasis and highlight how KuB may serve as a tumor-intrinsic PD-L1-targeting therapeutic.

Cortex Lycii Radicis, a medicinal plant, has been reported to inhibit epithelial–mesenchymal transition (EMT) and exhibit anti-lung cancer properties. Our previous study identified its major compound, Kukoamine B (KuB), as an inhibitor of membrane PD-1/PD-L1 interaction, thereby restoring T-cell function. However, the effect of KuB on EMT and the underlying mechanism thereof remain unknown. Herein, we show that PD-L1 overexpression enhances the proliferation, migration, and EMT of LUAD cells, upregulating N-cadherin and Vimentin, while downregulating E-cadherin. Mechanistically, PD-L1 directly binds phosphorylated p65 (p-p65) and facilitates p65 nuclear translocation, an interaction confirmed by molecular simulations. We found that KuB disrupts the PD-L1/p65 complex, impedes p65 nuclear translocation, and suppresses EMT, proliferation, and migration in LUAD cells. These inhibitory effects were reversed by PD-L1 overexpression. We therefore conclude that KuB suppresses EMT in LUAD by targeting intracellular PD-L1, blocking PD-L1–p65 interaction and nuclear translocation of p65.