Small deletions but not methylation underlie CDKN2A/p16 loss of expression in conventional osteosarcoma.
Conventional osteosarcoma is characterized by rapid growth, high local aggressiveness, and metastasizing potential. Patients developing lung metastases experience poor prognosis despite extensive chemotherapy regimens and surgical interventions. Previously we identified a subgroup of osteosarcoma patients with loss of CDKN2A/p16 protein expression in the primary tumor biopsies which was significantly predictive of a very poor prognosis. Here we aimed to identify the underlying mechanism(s) of this protein loss in relation to osteosarcoma behavior. The CDKN2A locus was analyzed in osteosarcoma cases with total loss of CDKN2A/p16 expression and in cases with high protein expression using melting curve analysis-methylation assay (MCA-Meth), fluorescent in situ hybridization (FISH), multiplex ligation-dependent probe amplification (MLPA), and mutation analysis. All cases with complete CDKN2A/p16 protein loss showed homozygous deletions at the CDKN2A locus. In none of the cases hyper methylation of the promoter region was seen which was confirmed by sequencing this region. Taken together we show that large or smaller deletions of the CDKN2A locus are evident in patient samples and underlie the CDKN2A/p16 protein expression loss while promoter methylation does not appear to be a mechanism of this expression loss. Genomic loss of CDKN2A instead of promoter methylation might be a plausible explanation for the rapid proliferation and high aggressiveness of osteosarcoma by simultaneous impairment CDKN2A/p14(ARF) function.
Mohseny
Alexander B
AB
Department of Pathology, Leiden University Medical Center, Leiden, The Netherlands.
Tieken
Chris
C
van der Velden
Pieter A
PA
Szuhai
Karoly
K
de Andrea
Carlos
C
Hogendoorn
Pancras C W
PC
Cleton-Jansen
Anne-Marie
AM
D001483:Base Sequence; D001859:Bone Neoplasms / Q000235:genetics*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D015870:Gene Expression; D016147:Genes, Tumor Suppressor; D019942:Genes, p16; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D012516:Osteosarcoma / Q000235:genetics*; D011379:Prognosis; D011401:Promoter Regions, Genetic; D017384:Sequence Deletion
D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm