Abstract
A number of primary human breast carcinomas exhibit amplification of the chromosome 11 region containing the intโ2/fgfโ3 protoโoncogene, and progression of breast cancer has been correlated with intโ2 amplification or with certain restriction fragment length polymorphisms (RFLPs) of the intโ2 gene. Using the polymerase chain reaction (PCR), we obtained the intโ2 coding sequences from six primary tumors, four of which exhibited amplification of the intโ2 gene and one of which exhibited amplification of the neu gene. The majority of these tumors (five of six) were aggressive, as judged by their early recurrence, metastasis, or both. Nucleotide sequencing of PCR products revealed that previously described BamHl and Pstl RFLPs of the intโ2 gene, as well as a new polymorphism at position 9154, were located within the intron between the second and third exons. A seventh tumor was used to localize one of the Pstl RFLPs 5 bp from the spliceโacceptor site of the third exon. However, none of the tumor DNAs analyzed showed differences in the intโ2 protein coding regions when compared with normal placenta DNA. These results imply that aggressive human breast cancers encode an unaltered form of the intโ2 protein. ยฉ 1992 WileyโLiss, Inc.