A candidate metastasis-associated DNA marker for ductal mammary carcinoma

Background: Molecular genetic markers to identify the 13% lymph node-negative mammary carcinomas that are prone to develop metastases would clearly be of considerable value in indicating those cases in need of early aggressive therapy. Methods: Representational difference analysis was used in an attempt to identify genetic alterations related to breast cancer metastasis by comparing genomic DNA from microdissected normal cells and from metastatic cells of ductal breast carcinoma patients. Results: Representational difference analysis products yielded 10 unique metastasis-associated DNA sequences (MADS), i.e. products apparently lost in metastatic cell DNA. Of these sequences, MADS-IX was found to be lost in the transition from primary to metastasis in two out of five ductal breast carcinoma cases. This sequence was localized on chromosome 10q21 by radiation hybrid mapping and fluorescence in situ hybridization. The PTEN gene, which is also located on chromosome 10q, was detected to be present by PCR in all five cases. On the contrary, a breast carcinoma cell line, HCC-1937, which has homozygous loss of a region encompassing the PTEN gene, showed the presence of MADS-IX. PCR screening of three additional breast carcinoma cell lines with known losses in specific chromosomal regions also showed the presence of MADS-IX. Conclusion: These data suggest that MADS-IX possibly is part of a novel candidate metastasis-associated gene located close to the PTEN gene on chromosome 10q. The first set of PCR screening in five patient samples indicates that it could be used as a molecular marker for ductal mammary metastasis.