PubMed · 13077012
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A BEUTEL, A TANZER. 1953. [Early changes in bone sarcoma].. https://pubmed.ncbi.nlm.nih.gov/13077012/
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The p53 tumor suppressor is phosphorylated in response to various cellular stress signals, such as DNA damage, leading to its release from MDM2 and consequent stabilization and activation as a transcription factor. In human U2OS cells, treatment with adriamycin causes p53 to be phosphorylated on all six serine residues tested, leading to the dissociation of p53 from MDM2 and transcription of the p21 and mdm2 genes. In contrast, in these cells, IPTG-dependent induction of p14ARF, which sequesters MDM2 away from p53, does not lead to detectable phosphorylation of any of the five N-terminal serine residues tested (6, 9, 15, 20, 37). Only C-terminal serine 392 is phosphorylated. However, the increase of p21 and mdm2 mRNAs was indistinguishable following treatment with adriamycin or induction of p14ARF. By using cDNA arrays to examine global p53-dependent gene expression in response to adriamycin or p14ARF, we found that most genes were regulated similarly by the two treatments. However, a subset of p53-regulated genes whose products have proliferative roles or regulate VEGF activity, newly described here, are repressed by p14ARF much more than by adriamycin. We conclude that the phosphorylation of p53 on N-terminal serine residues is not required for increased transcription of the great majority of p53-responsive genes and that the induction of p53 by p14ARF, with little phosphorylation, leads to substantial repression of genes whose products have roles in proliferation.
153Sm-ethylene diamine tetramethylene phosphonate (EDTMP) is a widely available and extensively tested radiopharmaceutical for systemic radionuclide therapy in patients with symptomatic multiple skeletal metastases. Its use is approved for any secondary bone lesion which has been shown to accumulate (99m)Tc-methylene diphosphonate, including breast carcinoma. The molecule is stable in vitro and upon injection more than 50% of the dose is avidly fixed by lesional and non-lesional bone, with the rest being rapidly eliminated unchanged via the urine. The short half-life (46.3 h), the relatively low-energy beta emissions (E(ave)=233 keV) and the gamma emission (103 keV) make (153)Sm a very attractive radionuclide, allowing therapeutic delivery of short-range electrons at relatively high dose rates with external imaging to corroborate biodistribution and possible dosimetric estimates. For a standard dose of 2,590 MBq/70 kg, the estimated radiation dose to metastases is 86.5 Gy. Critical organs are the bladder wall (2.5 Gy/2,590 MBq) and red marrow (4 Gy/2,590 MBq), with the latter being the critical factor in clinical practice as the dose-limiting factor is marrow radiotoxicity. The therapy has, however, proved safe provided that the platelet count exceeds 100 x 10(9)/l and the white blood cell count exceeds 3.5 x 10(9)/l. Clinical data obtained in fewer than 250 patients, within several studies, lead to the following conclusions: a dose of 37 MBq/kg has a better therapeutic ratio than a dose of 18.5 MBq/kg; the mean pain palliation rate after a single treatment in breast cancer is about 80%; toxicity is generally mild and transitory; and re-treatments are effective and safe provided that haematological values have fully recovered.
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