Coamplification of the hst-1 and int-2 genes in human cancers

The hst-1 gene, previously designated the hst gene, was identified as a transforming gene by transfection assays of genomic DNAs from various types of human cancers. We analyzed for alterations of the hst-1 gene in 18 bladder cancers, 23 renal cell carcinomas and 5 esophageal cancers. Although rearrangement of the gene was not detected in any of these samples, amplification of the hst-1 gene was found in 4 samples of tumors, including an invasive bladder cancer, both primary esophageal cancer and its lymph node metastasis, and kidney metastasis of an esophageal cancer. The same degree of amplification of the int-2 gene, the product of which has significant homology with the hst-1-encoded protein, was also observed in all of these DNA samples with amplified hst-1 gene. This result indicates close chromosomal localization of the two genes, which were amplified as one amplification unit.