Beclin1-targeting stapled peptide i7-01s-20 suppresses colorectal cancer by disrupting EGFR/β-catenin axis

Colorectal cancer (CRC) remains a leading cause of cancer-related mortality globally, necessitating novel therapeutic strategies. Beclin1, a crucial regulator of autophagy and endolysosomal trafficking with tumor-suppressive properties, is frequently downregulated in CRC, correlating with poor clinical outcomes. Despite its importance, the precise regulatory mechanisms of Beclin1 in CRC are poorly understood, and effective Beclin1-targeting therapies are scarce. This study investigates the anti-tumor potential and mechanism of i7-01s-20, a previously developed Beclin1-binding stapled peptide, in CRC.

Researchers analyzed Beclin1 and β-catenin expression in public transcriptomic, proteomic, and human CRC patient tissue cohorts. In vitro, they performed functional assays including autophagic flux detection, EGFR degradation assays, dual-luciferase reporter analysis, ubiquitination, and cycloheximide chase tests in CRC cell lines. Beclin1 knockdown rescue experiments verified target dependency. In vivo anti-tumor efficacy was assessed using DLD-1 subcutaneous xenograft tumor models treated with i7-01s-20 at gradient doses, with a scrambled peptide (ScraP) as a negative control. Quantitative DIA proteomics of xenograft tumors profiled global protein alterations.

Beclin1 expression was significantly decreased in human CRC tissues, correlating with advanced tumor stage and unfavorable patient survival. Conversely, β-catenin was highly accumulated in tumors and negatively correlated with Beclin1 at the protein level. In CRC cells, i7-01s-20 potently promoted EGFR endolysosomal degradation, which suppressed its downstream AKT/GSK-3β pathway. The peptide also triggered ubiquitin-mediated proteasomal degradation of β-catenin. Silencing endogenous Beclin1 completely abrogated these effects induced by i7-01s-20. Functionally, i7-01s-20 dose-dependently inhibited CRC cell proliferation and migration in vitro. In vivo, i7-01s-20 treatment significantly suppressed tumor growth in DLD-1 xenograft models. Proteomic analysis confirmed that i7-01s-20 modulated key proteins involved in EGFR and Wnt/β-catenin signaling pathways.

i7-01s-20 treatment significantly suppressed tumor growth in DLD-1 xenograft models by promoting EGFR degradation and triggering ubiquitin-mediated β-catenin degradation.