We previously showed that PAX3-FKHR expression in primary human myoblasts, cells that can give rise to RMS, cooperated with loss of p16INK4A to promote extended proliferation.
Expression of the p16INK4A (p16), p15INK4B (p15), and p14ARF genes, located at 9p21, was examined in pediatric neuroblastoma (NB), Ewing's sarcoma (ES), and rhabdomyosarcoma (RMS). p16 expression was absent in 4 of 5 ESs, and 2 of these 4 cases died. p16 expression was reduced or absent in 10 of 12 RMSs, and 4 of these 10 cases died.
Our data indicate that human c-MET and INK4a/ARF, situated at the nexus of pathways regulating myogenic growth and differentiation, represent critical targets in RMS pathogenesis.
To confirm the significance of p16 gene deletion in tumour biology of RMS, a temperature-sensitive p16 mutant (E119G) gene was retrovirally transfected into the human RMS cell line RD, which has homozygous gene deletion of p16 gene.
We looked for homozygous deletions of CDKN2A, CDKN2B (p15INK4B), and CDKN2C (p18) in 12 primary rhabdomyosarcoma (RMS) specimens and in five cell lines established from this cancer type.