Universal inactivation of both p16 and p15 but not downstream components is an essential event in the pathogenesis of T-cell acute lymphoblastic leukemia.
p16/p15 regulate the cell cycle pathway by inhibiting the cyclin Ds-CDK4/6 mediated phosphorylation of pRb. We reported previously that in T-cell acute lymphoblastic leukemia (T-ALL), p16 and p15 were frequently (approximately 70%) inactivated at the DNA level by deletion, mutation, or hypermethylation. Therefore, we hypothesize that inactivation of the cell cycle regulatory pathway may be essential in the pathogenesis of T-ALL, and that the remaining T-ALL with a wild-type p16/p15 gene likely harbor inactivation of these genes at RNA or protein levels. Alternatively, the downstream components of the pathway including CDK4/6, cyclin Ds, and pRb may be deregulated. In 124 primary T-ALLs, we found inactivation of the p16 and p15 genes at the DNA level in 79 (64%) and 64 (52%) samples, respectively. Only 9 of the 45 samples with wild-type p16 expressed p16 protein, whereas the remaining 36 lacked p16 expression at the RNA or protein level. In the 60 samples with an intact p15 gene, only 2 expressed p15 mRNA, and the only one analyzed lacked p15 protein. Overall, the abrogation rates for p16 and p15 at DNA/RNA/protein levels were 93% (115 of 124) and 99% (123 of 124), respectively. Although no alterations were evident in cyclin Ds or CDK4/6, pRb was hyperphosphorylated in the majority of samples investigated. These findings strongly support that both p16 and p15 are specific targets in the deregulation of the cell cycle pathway in T-ALL and that the inactivation of these genes is most likely essential in the pathogenesis of this disease.
Omura-Minamisawa
M
M
Department of Pediatrics/Hematology-Oncology, University of California, San Diego 92103, USA.
Diccianni
M B
MB
Batova
A
A
Chang
R C
RC
Bridgeman
L J
LJ
Yu
J
J
Pullen
J
J
Bowman
W P
WP
Yu
A L
AL
D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D018797:Cell Cycle Proteins; D002648:Child; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics* / Q000378:metabolism; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000737:chemistry / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D018807:Polymorphism, Single-Stranded Conformational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D025521:Tumor Suppressor Proteins
C493966:CDKN2B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins