Nerve growth factor (NGF) is increased during hepatic regeneration and carcinogenesis, but its role during hepatic metastasis is unknown. A tissue-array collection of metastases from 24 patients who had undergone hepatic excision of colorectal adenocarcinoma metastases was used to investigate NGF and neurotrophin receptor expression by cancer and stromal cells. NGF immunostaining of cancer cells only occurred in 2 out of 24 patients with hepatic metastases, while around 80% of patients had metastases with NGF-expressing stromal cells. Conversely, high affinity TrkA neurotrophin receptor immunoreactivity was mainly concentrated in cancer cells, with low expression occurring in tumor stroma. However, NGF immunostaining of tumor stroma and cancer cell immunostaining with anti-ki67 antibodies did not correlate, suggesting that NGF was not associated to metastatic cell proliferation. Anti-alpha-smooth muscle actin (ASMA) antobodies revealed that majority of metastasis-associated NGF-expressing cells had a myofibroblast phenotype. Interestingly, NGF immunoreactivity was unequivocally localized to desmin-expressing hepatic stellate cells (HSC), a prototypic myofibroblast precursor, and perimetastatic hepatocytes, located at the invasion front of metastases. NGF-expressing hepatocytes had phenotypic features suggesting epithelial-to-mesenchymal transition (snail, vimentin and ASMA overexpression with E-cadherin expression decrease). Consistent with clinical findings, a similar immunostaining pattern was reproduced in the experimental hepatic colonization of C26 and 51b colorectal cells. Moreover, NGF increased by two-fold in the hepatic blood from metastasis-bearing mice and also significantly increased by 2-3-fold in the supernatant of primary cultured HSC given tumor cell-conditioned medium (CM), and hepatocytes given tumor-activated HSC-CM, but not tumor cell-CM. Both NGF secretion and epithelial-to-mesenchymal transition in hepatocytes were TGFbeta-dependent. Recombinant NGF dose-dependently increased chemotactic migration, but not proliferation and adhesion of neurotrophin receptor-expressing cancer cells in vitro. HSC migration-stimulating activity of VEGF and tumor-activated hepatocytes were also NGF-mediated as shown with anti-NGF antibodies. Our results demonstrate that both hepatocyte- and HSC-derived myofibroblasts secrete NGF in the hepatic metastasis microenvironment of human and experimental colorectal carcinoma. The mechanism is TGFbeta-dependent. The migration-stimulating effect of NGF on both cancer and stromal cells suggests its contribution to hepatic metastasis development.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1431.