Morusin targets DNA methyltransferase 1 to trigger senescence and sensitizes colorectal cancer to senolytic therapy.

BACKGROUND Inducing tumor cell senescence is regarded as a promising strategy for cancer treatment. However, there is an urgent need for active ingredients that can safely and effectively induce tumor cell senescence and be used in combination with senolytics. Morusin, an isoprenylated flavonoid derived from the Morus alba L. (mulberry), exerts anti-inflammatory, antibacterial, and anti-tumor properties. However, the effect of morusin on colorectal cancer (CRC) remains unclear.

PURPOSE To investigate whether morusin can trigger CRC cell senescence and elucidate its potential mechanisms to offer a potential approach for combination therapy with senolytic agents.

METHODS CCK8, EdU assay, colony-formation, cell cycle analysis, calcein/PI staining assay, and SA-β-Gal staining were conducted to evaluate the suppressive effects of morusin on CRC cells in vitro. Mechanistic investigations were deciphered via molecular docking, network pharmacology, western blot, plasmid construction, cell transfection, molecular interaction assay, biotin affinity pull-down, and ubiquitination analysis. Xenograft mouse models and patient-derived tumor xenograft (PDX) were utilized to evaluate the efficacy of morusin in vivo.

RESULTS We discovered that morusin predisposed CRC cells to cellular senescence. Mechanistically, morusin directly binds to the Q576 site of DNMT1 to facilitate its degradation, subsequently inhibiting the expression of CDK2, and thereby promoting p53 expression. Importantly, morusin exposes the vulnerability of senescent CRC cells to apoptosis resistance, which is selectively eliminated by the senolytic agent ABT263.

CONCLUSION Morusin induces CRC cell senescence via the DNMT1/CDK2/p53 axis, and renders the cells vulnerable to senolytic agents. This study not only broadens the development and utilization of morusin but also provides a novel sequential therapeutic strategy for combating CRC.