Functional characterization of the human PRUNE protein: implications in cancer.

D'Angelo, Anna (2004). Functional characterization of the human PRUNE protein: implications in cancer. PhD thesis The Open University.



The functional characterization of H-PRUNE was performed using different approaches, in order to elucidate first the biochemical function of the protein, and then the correlation with other genes and the role in different tumour types.

First, we identified and characterized H-PRUNE phosphodiesterase activity, which is suppressed by dipyridamole. Interestingly, H-PRUNE interacts with NM23-Hl, an anti-metastatic protein involved in different processes as proliferation, differentiation and motility, suggesting us to investigate H-PRUNE possible correlation to tumour development and progression with respect to NM23-H1. Our study has consisted in elucidating H-PRUNE function in three different tumour types, as sarcoma, neuroblastoma, and breast cancer.

Both sarcoma and breast cancer analyses revealed that H-PRUNE, localized into the cytoplasm, acts as a negative regulator of NM23-H1. In fact, both aggressive sarcoma subtypes and metastatic breast cancer showed high protein levels of H-PRUNE and low levels of NM23-H1, indicating its involvement in advanced stages of cancer. Moreover, we demonstrated that both the H-PRUNE phosphodiesterase activity and the H-PRUNE and NM23-H1 complex increase cell motility in the MDA-MB-435 breast cancer cell line. The overview of genes and pathways influenced by H-PRUNE overexpression in the MDA-MB-435 breast cancer cellular model has been performed in order to understand the molecular changes in tumour cells.

Interestingly, we found high levels of H-PRUNE, localized into the nuclear compartment, correlated to high levels of both NM23-H1 and NM23-H2 (an isoform of the NM23 family) in advanced stages of neuroblastoma.

We identified a new function of H-PRUNE as a transcriptional regulator of NM23-H2 and we postulated a transcriptional mechanism of regulation, including activation of NM23-H1 by NM23-H2 and of NM23-H2 by H-PRUNE.

This study evidences H-PRUNE function, as a regulator of NM23-H1 anti-metastatic function by two different mechanisms of action, correlated to the different compartmentalization of H-PRUNE protein.

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