Absence of p53 gene mutations in hepatocarcinomas from a Mediterranean area of Spain. A study of 129 archival tumour samples.

The incidence of p53 gene abnormalities in human hepatocellular carcinoma (HCC) varies in different geographical areas, being higher in regions where hepatitis virus infection and dietary exposure to aflatoxin B1 are the most common aetiological agents. These mutations are less frequently encountered in Europe, although some studies have reported p53 protein overexpression in up to 45% of cases analysed. We have analysed 129 tumour samples of primary malignant hepatic neoplasms recovered from paraffin blocks processed in two pathology laboratories in a Mediterranean area of Spain (Valencia and Gerona). Among 14 cases in which p53 immunohistochemistry expression proved positive, 5 stained in more than 50% of the cell nuclei. By PCR-SSCP analysis we could detect the complete sequence from exon 5 through 8 in 70 cases and part of this region in the remaining cases, but no mutations were found. We found no relationship with the clinical stage, tumour stage or clinical outcome. We conclude that p53 gene alterations are not a major event in the malignant transformation of hepatic cells in this region of the Mediterranean. The variable incidence of p53 gene alterations in other geographical areas may reflect a different genetic background for the aetiology of HCC.

Molecular alterations of the RB1, TP53, and MDM2 genes in primary and xenografted human osteosarcomas.

We report the status of the RB1, TP53, and MDM2 genes in human osteosarcomas and cell lines established from surgical specimens and transplanted into athymic naked mice. By using reverse transcriptase-polymerase chain reaction (RT-PCR) as a prescreening technique and posterior sequencing, we observe new mutations in the RB1 gene, notably a duplication in tandem of exons 3 through 6. TP53 mutations appear in codons most frequently mutated in osteosarcomas. We have not seen MDM2 gene amplification in any reported case. These molecular alterations appear in different osteosarcomas not simultaneously present in the same tumor sample. A link has been described between these three genes in the pathways that control the cell cycle and the tumoral progression, but their functions are probably independent in the development of osteosarcomas. TP53 mutations appear in adult patients, whereas RB1 alterations occur mostly in younger patients.

Cell-to-cell interaction between N-13A ascitic hepatoma cells and normal cells maintained in short-term co-cultures: an optical, transmission and scanning electron microscopical study.

N-13A malignant ascitic hepatoma, induced by 4-dimethylaminoazobenzene in Wistar rats, does not produce distant mestastases when transplanted in vivo. The mixed co-cultures of N-13A tumor cells and several tissue explants of newborn Wistar rats show selective adhesivity between tumoral and hepatic epithelial cells, but not with fibroblast-like cells of nervous tissue, kidney or diaphragm. In short-term co-cultures, N-13A cells in contact with rat hepatocytes prepared by the collagenase perfusion technique, display a selective adherence capacity with the production of abundant microvilli and fingerlike protrusions (microspikes) which are elaborated by the neoplastic cells. Groups of tumoral cells tightly envelop the free surface of the cultured hepatocytes. Tight-junction formations are observed, and immature desmosomes and polydesmosomic systems are also seen between both tumoral and normal cells.