Parathyroid hormone-related protein (PTHrP) in breast cancer and benign breast tissue

Parathyroid hormone-related protein (PTHrP) 1–86 was quantified by immunoassay in extracts of 132 breast cancers, 27 samples of normal breast tissue and four fibroadenomas. PTHrP 1–86, was detected in 68% of primary tumours (range 40–302 000 fmol/g), 33% of normal breast tissues (range 100–1800 fmol/g), and all four fibroadenomas (range 110–11600 fmol/g). PTHrP displayed molecular heterogeneity on gel filtration chromatography, and 1–86, 1–34 and 37–67 immunoreactivity eluted as 25–27 kDa together with a peak of 19–21 kDA containing only 37–67 activity. Tumour PTHrP 1–86 levels correlated inversely with age ( P < 0.05) and were higher in premenopausal women ( P = 0.05). The proportion of tumours containing PTHrP was higher in axillary node positive premenopausal women ( P < 0.05). These data suggest that oestrogen may regulate expression of PTHrP in breast cancer and that production of PTHrP may be linked to development of axillary node metastases.