SV40 and p53 as team players in childhood lymphoproliferative disorders

Simian virus 40 (SV40) is known to be potently oncogenic and can induce several types of tumours, such as lymphoma. p53 was discovered as a cellular partner of the SV40 large T-antigen, the oncoprotein of this virus. There have not been many studies on SV40 and p53 in lymphomas and the ones that exist, are controversial. A comparison of these two components in lymphoma has not been reported previously. We examined 91 lymphomas [60 B-cell non-Hodgkin's lymphomas (B-NHLs), 19 B-cell acute lymphoblastic leukemias (B-ALLs), 7 B-cell precursor acute lymphoblastic leukemias and 5 T-cell acute lymphoblastic leukemias] for the presence of SV40. Overall, 40 samples from 12 B-NHL/19 B-ALL patients were additionally investigated for p53 mutation in the hot-spot exons 5 to 8. Overall, we found 62/91 lymphomas to be SV40-positive, among them 16/19 B-ALLs and 38/60 B-NHLs. SV40 was absent in 147 of the 149 blood control samples. We found 11 p53 mutations in 19 B-ALL patients: 5 in exon 5 (codons 132, 141, 143, 155 and 181), 4 in exon 7 (codons 236, 238 and 248), 2 in exon 8 (codon 273). In B-NHL patients we found p53-mutations in 9/12 samples: 6 of these in 3 lymph nodes (LNs). One LN harboured 3 different p53 mutations: Exon 5 (codon 132), exon 6 (codon 213) and exon 8 (codon 288). Another LN showed 2 different p53 mutations: Exon 6 (codon 213) and exon 8 (codon 285). Except for 1 nonsense mutation in an LN of a B-NHL patient, all 20 mutations were missense mutations, 2 were homozygous, both found in B-NHL-samples, and one of these (codon 175) is known to cause the global denaturation of p53. All occur in the DNA-binding domain of p53. All specimens showing a p53 mutation, were SV40-positive. p53 mutaions found in LNs of B-NHL patients harbour high SV40 copy numbers. Our data strongly support an important role for SV40, as well as a strong association of SV40 and p53 in childhood lympho-proliferative disorders.