TY - JOUR
T1 - Inactivation of p16INK4a (inhibitor of cyclin-dependent kinase 4A) immortalizes primary human keratinocytes by maintaining cells in the stem cell compartment
AU - Maurelli, Riccardo
AU - Zambruno, Giovanna
AU - Guerra, Liliana
AU - Abbruzzese, Claudia
AU - Dimri, Goberdhan
AU - Gellini, Mara
AU - Bondanza, Sergio
AU - Dellambra, Elena
PY - 2006/7
Y1 - 2006/7
N2 - Replicative senescence of human keratinocytes is determined by a progressive decline of clonogenic and dividing cells, and its timing is controlled by clonal evolution (i.e., the transition from stem cells to transient amplifying and postmitotic cells). Progressive increase of p16 INK4a (inhibitor of cyclin-dependent kinase 4A) expression has been shown to correlate with keratinocyte clonal evolution. Thus, the aim of our study is to understand whether p16INK4a accumulation is a triggering mechanism of epidermal clonal evolution or a secondary event. We show that inactivation of p16INK4a, by an antisense strategy, allows primary human keratinocytes to escape replicative senescence. Specifically, p16 INK4a inactivation alone blocks clonal evolution and maintains keratinocytes in the stem cell compartment. Antisense excision is followed by keratinocyte senescence, confirming that persistent p16INK4a inactivation is required for maintenance of clonal evolution block. Immortalization is accompanied by resumption of B-Cell Specific Moloney murine leukemia virus site 1 (Bmi-1) expression and telomerase activity, hallmarks of tissue regenerative capacity. In turn, Bmi-1 expression is necessary to maintain the impairment of clonal evolution induced by p16INK4a inactivation. Finally, p16INK4a down-regulation in transient amplifying keratinocytes does not affect clonal evolution, and cells undergo senescence. Thus, p16INK4a inactivation appears to selectively prevent clonal conversion in cells endowed with a high proliferative potential. These data indicate that p16INK4a regulates keratinocyte clonal evolution and that inactivation of p16INK4a in epidermal stem cells is necessary for maintaining stemness.
AB - Replicative senescence of human keratinocytes is determined by a progressive decline of clonogenic and dividing cells, and its timing is controlled by clonal evolution (i.e., the transition from stem cells to transient amplifying and postmitotic cells). Progressive increase of p16 INK4a (inhibitor of cyclin-dependent kinase 4A) expression has been shown to correlate with keratinocyte clonal evolution. Thus, the aim of our study is to understand whether p16INK4a accumulation is a triggering mechanism of epidermal clonal evolution or a secondary event. We show that inactivation of p16INK4a, by an antisense strategy, allows primary human keratinocytes to escape replicative senescence. Specifically, p16 INK4a inactivation alone blocks clonal evolution and maintains keratinocytes in the stem cell compartment. Antisense excision is followed by keratinocyte senescence, confirming that persistent p16INK4a inactivation is required for maintenance of clonal evolution block. Immortalization is accompanied by resumption of B-Cell Specific Moloney murine leukemia virus site 1 (Bmi-1) expression and telomerase activity, hallmarks of tissue regenerative capacity. In turn, Bmi-1 expression is necessary to maintain the impairment of clonal evolution induced by p16INK4a inactivation. Finally, p16INK4a down-regulation in transient amplifying keratinocytes does not affect clonal evolution, and cells undergo senescence. Thus, p16INK4a inactivation appears to selectively prevent clonal conversion in cells endowed with a high proliferative potential. These data indicate that p16INK4a regulates keratinocyte clonal evolution and that inactivation of p16INK4a in epidermal stem cells is necessary for maintaining stemness.
KW - Bmi-1
KW - Keratinocyte clonal evolution
KW - Keratinocyte senescence
KW - Telomerase
UR - http://www.scopus.com/inward/record.url?scp=33845676619&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33845676619&partnerID=8YFLogxK
U2 - 10.1096/fj.05-4480fje
DO - 10.1096/fj.05-4480fje
M3 - Article
AN - SCOPUS:33845676619
VL - 20
JO - FASEB Journal
JF - FASEB Journal
SN - 0892-6638
IS - 9
ER -