Doxorubicin induces a reversible senescence-like state in the EPC fish cell line.

Cellular senescence is generally defined as a stable and typically irreversible cell cycle arrest triggered by diverse stresses, including DNA damage. However, fish-derived cells exhibit intrinsic resistance to stable senescence, and the extent to which this resistance can be overcome remains unclear. Here, we studied the effects of the DNA-damaging chemotherapeutic agent doxorubicin (DOX) in the fish cell line Epithelioma papulosum cyprini (EPC). DOX treatment induced multiple senescence-associated phenotypes in EPC cells, including morphological changes, senescence-associated β-galactosidase (SA-β-gal) activity, and the secretion of senescence-associated secretory phenotype (SASP) factors. Despite these changes, EPC cells did not undergo irreversible proliferative arrest and were able to resume proliferation in a condition-dependent manner, even after prolonged DOX exposure. Furthermore, these responses in EPC cells were not stably maintained but instead exhibited dynamic regulation across phenotypic, proliferative, and transcriptional states. Together, these findings demonstrate that DOX-induced DNA damage results in a transient and reversible senescence-like state in EPC cells, highlighting fundamental differences between teleost and mammalian senescence programs.