Combined evaluation of NGF and p75NGFR expression is a biomarker for predicting prognosis in human invasive ductal breast carcinoma.

Nerve growth factor (NGF) is a member of the neurotrophin family and is essential for the differentiation and maintenance of neural cells. Recently, it has been reported that NGF is involved in the growth of breast cancer. On the other hand, two types of NGF receptors have been identified, a low-affinity receptor, p75NGFR, and a high-affinity receptor, TrkA. NGF-p75NGFR interaction is known to play an important role in apoptosis, whereas NGF-TrkA interaction is responsible for the survival of neural cells. We examined the relationship between clinicopathological factors, Ki-67 index, apoptotic index and the immunohistochemical expression of NGF, TrkA and p75NGFR in 71 invasive ductal breast carcinoma (IDBC) specimens. Our data indicate that positive Ki-67 expression (a labeling index exceeding 30%) correlates significantly with the positive expression of NGF (p=0.0091). Moreover, the apoptotic index was found to correlate with a strong expression of p75NGFR. Furthermore, patients who were NGF positive and p75NGFR negative had significantly poorer disease-free survival rates (p=0.0165). In contrast, those who were NGF negative and p75NGFR positive had significantly more favorable outcomes (p=0.0191). These findings suggest that a combined evaluation of NGF and p75NGFR expression is a predictive factor in the prognosis of IDBC patients.