Alterations of the p53/MDM2 pathway are frequent in OS and usually represent mutually exclusive tumorigenic events. p53 does not appear to be a major determinant of proliferative rate in OS.
To investigate the biological significance of RB and p53 gene inactivations, a wild-type RB or p53 cDNA expression vector regulated by tetracycline was introduced by stable transfection into an osteosarcoma cell line Saos-2, in which both the RB and p53 genes were inactivated.
Here we examine whether wild-type (wt) p53 protein suppresses X-ray-induced mutations using an isopropyl-beta-D-thiogalactopyranoside (IPTG)-regulated p53 expression system in human osteosarcoma Saos-2 cells.
The effect of overexpression of p21waf1 on drug sensitivity was studied in an osteosarcoma cell line (SaOs-2) lacking both p53 and functional retinoblastoma protein using a tetracycline (TC)-inducible expression system. p21waf1 expression was barely detectable in SaOS-2 cells incubated in the presence of TC.
We here demonstrate that the cell cycle was arrested in G2/M phase following supplementation with DZQ of human osteosarcoma Saos-2 cells (lacking both p53 and pRb) and HCT116 cells.
The involvement of p53 in tumour response was investigated in an osteosarcoma cell line, SAOS, which is null for p53 and is highly sensitive to BBR 3464, and in the same cells following introduction of the wild-type p53 gene.
Stable transformants with a mutant or wild type p53 made by introducing cDNA into the human osteosarcoma cell line, Saos-2, which lacks an endogenous p53 were used.
The event-free survival (EFS) was worse in Ewing sarcoma patients with p16INK4 and p14ARF mutation/deletion than in those without the mutation/deletion (P = 0.019), and EFS was worse in osteosarcoma patients with TP53 alterations than in those without TP53 alterations (P = 0.048).
Therefore the cytocidal effect of CDDP and the synergistic antitumor effect of caffeine are enhanced by the introduction of a wild-type p53 gene into a human osteosarcoma cell line null for p53.
This IRES was active in most transiently transfected human and nonhuman cell types, with a higher activity in p53 -/- osteosarcoma and neuroblastoma cell lines.
We show that in hamster (Chinese hamster ovary) or human (osteosarcoma 143) cell lines the replication of both Py and papillomavirus origins was efficiently blocked by p53.
Our results revealed an inactive form of p53 sporadically seen in the samples, a total loss of Rb protein expression, an increased expression of Cdk4, MDM2, c-fos, and c-myc proteins which literature currently reports being the principal alterations found in osteosarcoma.
To address the role of p53 mutations in the development and progression of osteosarcoma, the authors analyzed specimens from 247 patients with primary localized osteosarcomas and 25 patients with osteosarcomas that were metastatic at the time of diagnosis.
The aerosol delivery of PEI-based formulations of p53 or synthetic p53 variant genes represents a promising new strategy for the treatment of established human osteosarcoma lung metastases.
Poly(ADP-ribosyl)ation of p53 by PARP-1 during early apoptosis in osteosarcoma cells also inhibited p53 interaction with its DNA consensus sequence; thus, poly(ADP-ribosyl)ation may represent a novel means for regulating transcriptional activation by p53 in vivo.