MicroRNA-34a induces senescence-like growth arrest in human colon cancer cells by modulating the E2F pathway. This study demonstrates that miR-34a is upregulated in response to DNA damage, such as adriamycin, in human colon cancer cells. Introduction of miR-34a into HCT 116 and RKO cells significantly suppressed cell proliferation and induced senescence-like phenotypes, including increased cellular size and senescence-associated β-galactosidase (SA-β-gal) staining. miR-34a also suppressed tumor growth in mice when delivered with atelocollagen. Gene expression analysis revealed that miR-34a downregulated the E2F pathway and upregulated the p53 pathway, leading to cell cycle arrest and senescence. Additionally, miR-34a expression was decreased in 36% of human colon cancer samples compared to normal tissues. These findings suggest that miR-34a functions as a potent tumor suppressor by modulating the E2F signaling pathway, and its downregulation may contribute to colon cancer development. The study highlights the role of miR-34a in cancer progression and provides insights into its potential as a therapeutic target.MicroRNA-34a induces senescence-like growth arrest in human colon cancer cells by modulating the E2F pathway. This study demonstrates that miR-34a is upregulated in response to DNA damage, such as adriamycin, in human colon cancer cells. Introduction of miR-34a into HCT 116 and RKO cells significantly suppressed cell proliferation and induced senescence-like phenotypes, including increased cellular size and senescence-associated β-galactosidase (SA-β-gal) staining. miR-34a also suppressed tumor growth in mice when delivered with atelocollagen. Gene expression analysis revealed that miR-34a downregulated the E2F pathway and upregulated the p53 pathway, leading to cell cycle arrest and senescence. Additionally, miR-34a expression was decreased in 36% of human colon cancer samples compared to normal tissues. These findings suggest that miR-34a functions as a potent tumor suppressor by modulating the E2F signaling pathway, and its downregulation may contribute to colon cancer development. The study highlights the role of miR-34a in cancer progression and provides insights into its potential as a therapeutic target.