Genome‑wide CRISPR screening identifies <i>CLDN1</i> as a central node in the anticancer mechanisms of berberine and as a therapeutic target in lung cancer

Berberine (BBR), a natural compound with diverse anticancer properties, exerts potent inhibitory effects on lung cancer cell proliferation. However, its particular molecular targets remain unknown. The present study aimed to identify the key genetic determinants that mediate the cellular response to BBR in lung cancer. To achieve this, genome-wide clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) knockout screening was conducted in A549 cells, followed by functional validation and mechanistic assays. In the study, the genome-wide CRISPR/Cas9 knockout screening in A549 lung cancer cells identified claudin-1 (<i>CLDN1</i>) as a critical modulator of BBR sensitivity. Notably, whilst <i>CLDN1</i> was enriched in the positive selection screen, its knockout markedly increased the sensitivity of A549 cells to BBR, thus leading to enhanced G1-phase arrest and reduced proliferation. These findings suggest that <i>CLDN1</i> could serve a dual role, promoting cellular resistance under selective pressure, while simultaneously demonstrating a therapeutic vulnerability when directly inhibited. Overall, the present study identified <i>CLDN1</i> as a key mediator of the anticancer effects of BBR, thus providing a foundation for its potential development as a therapeutic target to optimize lung cancer therapy.