Mina Bissell and colleagues have identified a
molecular marker that could detect the early stages
of human breast cancer. A comparison of gene expression
among cells of a human breast cancer progression
series, nonmalignant (S1), premalignant (S2) and
malignant (T4-2) human breast cells, shows that
the expression of a new gene, named "AZ-1,"
abruptly declines as cells become tumorigenic.
Transcripts of AZ-1, obtained using differential
display-PCR, were also not detected in ten other
malignant human breast epithelial cell lines,
whereas they were present in normal human myoepithelial
and luminal epithelial cells. Chromosomal localization
of the AZ-1 gene has been mapped by fluorescence
in situ hybridization (FISH). AZ-1 was low or
absent in 4 primary breast tumors and expressed
in normal breast tissue. Based on the inverse
relationship of its expression level and tumor
phenotype in all of the tumor cell lines and tissues
analyzed, AZ-1 is a potential candidate as a tumor
marker for human breast cancer.