Nerve Growth Factor in Breast Cancer Cells Promotes Axonal Growth and Expression of Calcitonin Gene-related Peptide in a Rat Model of Spinal Metastasis

Background/Aim: Bone metastasis commonly causes severe pain. Nerve growth factor (NGF) contributes to pain, and promotes the production of pain-associated neuropeptides, such as calcitonin gene-related peptide (CGRP), from sensory nerve endings. We hypothesized that breast cancer cells have NGF levels that promote axonal growth from dorsal root ganglia (DRGs) neurons, and increase their CGRP production associated with pain from spinal metastases. Materials and Methods: Expression of NGF by the cultured rat breast adenocarcinoma cell line CRL-1666 was determined using an enzyme-linked immunosorbent assay (ELISA). We constructed a rat model of spinal metastasis by implanting CRL-1666 into L6 vertebrae and determined the change in CGRP expression in DRG neurons innervating vertebrae immunohistochemically. Results: NGF was expressed by CRL-1666. When DRG cells were co-cultured with CRL-1666, there were more CGRP-ir neurons and with a greater average length of axon growth than in cultures without CRL-1666 (p<0.05). In the rat model of metastasis, there were more CGRP-ir DRG neurons innervating vertebra treated with CRL-1666 than in vertebrae from sham surgery control rats (p<0.05). Conclusion: NGF from breast cancer may mediate spinal bone pain from metastasis via axonal growth and up regulation of pain-associated neuropeptides.