Zn-alpha 2-glycoprotein levels in breast cancer cytosols and correlation with clinical, histological and biochemical parameters

Zn-alpha 2-glycoprotein (Zn-alpha 2-gp), a protein present at high levels in breast cyst fluid, has been measured in 104 breast tumour cytosols by using an immunoenzymatic assay. Concentrations of Zn-alpha 2-gp ranged from 0 to 23.5 micrograms/mg of total soluble protein, with an average value of 2.4 micrograms/mg. There was no significant correlation between Zn-alpha 2-gp and menopausal status, tumour size or lymph node involvement, or between this protein and biochemical parameters such as oestrogen receptor, cathepsin D or pS2 levels. However, there was a significant association between Zn-alpha 2-gp and histological grade of tumours, with higher Zn-alpha 2-gp levels in well-differentiated tumours (mean 4.6 micrograms/mg) than in moderately (1.8 micrograms/mg) or poorly (0.9 micrograms/mg) differentiated tumours. On the basis of these results, we propose that Zn-alpha 2-gp may be considered as a biochemical marker of differentiation in breast cancer.