9423

NTN1

netrin 1;NTN1;netrin 1

epididymis tissue protein Li 131P|netrin 1, mouse, homolog of|netrin-1

17p13.1

protein-coding

Netrin-1, an axon navigation cue was proposed to play a crucial role during colorectal tumorigenesis by regulating apoptosis. The netrin-1 receptors DCC and UNC5H were shown to belong to the family of dependence receptors that share the ability to induce apoptosis in the absence of their ligands. Such a trait confers on these receptors a tumor suppressor activity. expression of one of these dependence receptors at the surface of a tumor cell is indeed speculated to render this cell dependent on ligand availability for its survival, hence inhibiting uncontrolled cell proliferation or metastasis. Consequently, it is a selective advantage for a tumor cell to lose this dependence receptor activity, as previously described with losses of DCC and UNC5H expression in human cancers. However, the model predicts that a similar advantage may be obtained by gaining autocrine expression of the ligand. We describe here that, unlike human nonmetastatic breast tumors, a large fraction of metastatic breast cancers overexpress netrin-1. Moreover, we show that netrin-1-expressing mammary metastatic tumor cell lines undergo apoptosis when netrin-1 expression is experimentally decreased or when decoy soluble receptor ectodomains are added. Such treatments prevent metastasis formation both in a syngenic mouse model of lung colonization of a mammary cancer cell line and in a model of spontaneous lung metastasis of xenografted human breast tumor. Thus, netrin-1 expression observed in a large fraction of human metastatic breast tumors confers a selective advantage for tumor cell survival and potentially represents a promising target for alternative anticancer therapeutic strategies.

Acting via its receptor UNC5B, netrin-1, one of the major neuronal guidance cues, plays an important role in angiogenesis, neurogenesis, tissue morphogenesis, embryonic development, cancer, inflammation, and various pathologies. However, its role has not been reported in prostate carcinoma. To investigate the association of netrin-1 and UNC5B expression with prostate carcinoma, several human prostate carcinoma cell lines were cultured and the expression levels of netrin-1 and UNC5B were determined by real-time PCR and Western blot. Calphostin C, (the inhibitor of PKC alpha) and phorbol-12-myristate 13-acetate-PMA (the agonist of PKC alpha) were used to treat the prostate carcinoma cells, and the cell proliferation and invasion abilities were measured by CCK-8 and wound-healing assays. Proliferation of DU145 cells was affected by the recruitment of PMA and calphostin C in a dose-dependent manner. By immunofluorescence, we identified the localization of netrin-1 and UNC5B in prostate carcinoma cell lines (DU145, 22RV1, PC3, PC3M, and RWEP) and found that netrin-1 was highly expressed in the nucleolus but there was no expression of UNC5B. The co-localization expression of PKC alpha and UNC5B was confirmed by the confocal immunofluorescence. Higher netrin-1 and lower UNC5B expression in all prostate carcinoma cell lines indicated that netrin-1 and UNC5B could be used to predict metastasis.