No abstract

We have previously performed an unbiased screen to identify genes whose expression is associated with the metastatic phenotype. Secondary screening of these genes using custom microarray chips identified ASAP1, a multidomain adaptor protein with ADP-ribosylation factor-GAP activity, as being potentially involved in tumor progression. Here, we show that at least three different splice forms of ASAP1 are upregulated in rodent tumor models in a manner that correlates with metastatic potential. In human cancers, we found that ASAP1 expression is strongly upregulated in a variety of tumors in comparison with normal tissue and that this expression correlates with poor metastasis-free survival and prognosis in colorectal cancer patients. Using loss and gain of function approaches, we were able to show that ASAP1 promotes metastasis formation in vivo and stimulates tumor cell motility, invasiveness, and adhesiveness in vitro. Furthermore, we show that ASAP1 interacts with the metastasis-promoting protein h-prune and stimulates its phosphodiesterase activity. In addition, ASAP1 binds to the SH3 domains of several proteins, including SLK with which it co-immunoprecipitates. These data support the notion that ASAP1 can contribute to the dissemination of a variety of tumor types and represent a potential target for cancer therapy.

HighlightsGeneral overview of the caspase protein family.Stem cells: fundamental concepts.Caspase roles in embryonic and Induced pluripotent stem cells.Caspase roles in adult stem cells.Pathological consequences of caspase deregulation and therapeutic potential of caspase modulation.

Nm23-H1 has been identified as a metastatic suppressor gene in murine melanoma cell lines. Several functions have been attributed to its activity in cancer, including a histidine kinase activity, DNA repair, and regulation of other proteins involved in metastatic formation. While in breast cancer, NM23-H1 overexpression indicates a benign status through impairing progression of disease, its function is opposite in other cancers; e.g., neuroblastoma. To further understand this dichotomy of function in cancer, we have analyzed its function in prostate cancer, in which the relationship between NM23-H1 expression and prognostic state is today controversial. In vitro, overexpression of NM23-H1 in PC3 cells inhibited their cell motility, while downregulation of NM23-H1 expression in these cells by RNA interference showed enhanced cell motility. Immunohistochemistry analysis performed on 346 prostate cancer tissue samples showed a relationship between high levels of NM23-H1 expression in the nuclei of these tumorigenic cells and elevated Gleason score, with high levels of NM23-H1 cytoplasmic staining related to metastatic stage. This retrospective survival study demonstrates that high levels of NM23-H1 expression in the cytoplasm determine recurrence of prostate-specific antigen levels only in those patients with metastatic disease. Our findings suggest a correlation between high levels of NM23-H1 protein in the cytoplasm of the cells and progression of prostate cancer to metastasis, thus definitively identifying NM23-H1 as a new negative prognostic marker in prostate cancer.

Nm23-H1 (also known as NDPKA) and h-Prune form a protein complex that is part of a little-understood protein network. Modifications of this complex correlate with cancer status. Here, we focus on the role of the Nm23-H1-h-Prune complex in cellular physiology, through an analysis of the balance between the 'bound' and 'non-bound' states of Nm23-H1 and h-Prune, whereby we speculate on the 'read-out' during cell homeostasis under non-balanced conditions. We have analysed the biochemical activities of both Nm23-H1 and h-Prune alone and in combination, focussing on the anti-metastatic activity of Nm23-H1. We have then investigated the cellular mechanisms responsible for the formation of the Nm23-H1-h-Prune complex. To evaluate the importance of the equilibrium between the formation of the Nm23-H1-h-Prune complex and the 'free' levels of Nm23-H1 and h-Prune, we propose a model based on a pro-cancer condition where this equilibrium is negatively affected.