Ras oncogenes and p53 tumor suppressor gene analysis in cardiac myxomas

Although ras oncogenes and p53 tumor suppressor gene mutations are implicat ed in the development of several human tumors, little is known about their role in the pathogenesis of primary cardiac tumors. Paraffin-embedded tissu e from 19 cardiac myxomas were investigated for the presence of ras oncogen es and p53 tumor suppressor gene abnormalities. Immunohistochemical analysi s was used to identify the accumulation of p21-ras and p53 proteins. A poly merase chain reaction was used to amplify exons 1 and 2 of the ras genes an d exons 5 to 8 of the p53 gene. The PCR products were analyzed by single st rand conformation polymorphism analysis and by direct DNA sequencing. Three of 19 myxomas showed strong positive staining for the ras p21 protein. In contrast, nuclear p53 was not detectable in any of the myxomas. Among the r as p21 immunopositive myxomas, 2 were heterozygous for a missense point mut ation of the K-ras, Gly 12Asp. Further screening of the remaining myxomas s howed no mutation or even silent polymorphism in any exon of the ras and p5 3. The results suggest that although genetic alterations of ras oncogenes a nd p53 are uncommon events in cardiac myxomas, ras mutations may be involve d in the pathogenesis of a subgroup of this type of tumor.