Breast cancer markers: comparison between sialyltransferase and human mammary epithelial antigens (HME-Ags) for the detection of human breast tumors grafted in nude mice

Sialyltransferase (CMP-sialic acid:asialofetuin sialyltransferase) and human mammary epithelial antigens (HME-Ags, cell surface antigens specific to human mammary epithelial cells) were determined in plasma of nude mice grafted with breast and non-breast human tumors to assess their possible usefulness as breast cancer markers. The plasma transferase activity was significantly higher (p less than 0.01) in tumor groups relative to the control. However, no significant difference (p less than 0.05) could be found in the transferase level between breast and non-breast tumor groups, showing the enzyme's lack of specificity for breast cancer. Furthermore, the surgical procedure performed on the control normal healthy group (no tumor), resulted in an important increase of the enzyme level, while HME-Ags remained unchanged. HME-Ags were essentially negative in control as well as non-breast tumor groups. After surgical removal of breast tumors, HME-Ags level dropped drastically to the background level (from 122 to less than 30 ng/ml plasma). These data indicate that HME-Ags are more sensitive and specific than sialyltransferase as markers for human breast tumor, and suggest that HME-Ags may be clinically useful in the early detection of breast cancer as well as in the followup of patients with metastatic breast tumor.