Lack of a p16INK4a/ARF locus in fish genome may underlie senescence resistance in the fish cell line, EPC

Abstract

Unlike most mammalian cell lines, fish cell lines are immortal and resistant to cellular senescence. Elevated expression of H-Ras contributes to the induction of senescence in a fish cell line, EPC, but is not sufficient to induce full senescence. Here, we focused on the absence of a p16INK4a/ARF locus in the fish genome, and investigated whether this might be a critical determinant of the resistance of EPC cells to full senescence. We found that transfected EPC cells constitutively overexpressing p16INK4a exhibited large size and flat morphology characteristic of prematurely senescent cells; the cells also showed p53-independent senescence-like growth arrest and senescence-associated β-galactosidase (SA-β-gal) activity. Furthermore, the mRNA levels of proinflammatory senescence-associated secretory phenotype (SASP) factors increased in EPC cells constitutively overexpressing p16INK4a. These results suggest that the lack of p16INK4a in the fish genome may be a critical determinant of senescence resistance in fish cell lines.