Expression and Signaling Pathways of Nerve Growth Factor (NGF) And Pro-NGF in Breast Cancer: A Systematic Review

Abstract

Breast cancer represents the most frequent cancer and the leading cause of cancer death among women. Thus, the prevention and early diagnosis of breast cancer appears to be of primary urgency as well as the development of new treatments able to improve its prognosis. Nerve Growth Factor (NGF) is a neurotrophic factor that plays a key role in the regulation of neuronal functions thought the binding to the Tropomyosin receptor kinase A (TrkA) and the Nerve Growth Factor receptor or Pan-Neurotrophin Receptor 75 (NGFR/p75NTR). Also, its precursor (pro-NGF) can extert biological activity by forming a trimeric complex with NGFR/p75NTR and sortilin or by binding to TrkA receptors with low affinity. Both in vitro and in vivo studies showed that NGF is synthesized and released by breast cancer cells and has mitogen, antiapoptotic and angiogenic effects on these cells through the activation of different signaling cascades that involve TrkA and NGFR/p75NTR receptors. Conversely, pro-NGF signaling has been related to breast cancer invasion and metastasis. Other studies suggested that NGF and its receptors could represent a good diagnostic and prognostic tool, as well as promising therapeutic targets for breast cancer. Here, we comprehensively summarize and systematically review the current experimental evidence on this topic.