Defining the role(s) of non-classical tumour suppressor Wwox in cellular function using Drosophila melanogaster genetic modelling

Abstract

The WWOX gene has been identified as the gene that spans the FRA16D common chromosomal fragile site (CFS), which is a frequent site of DNA instability in cancer. Perturbation of the WWOX gene has been reported in various cancers, with low WWOX levels correlating with poorer prognosis. Individuals who inherit a non-functional copy of WWOX have also been found to be at greater risk of developing cancer. WWOX has been implicated in various cellular pathways, however the role of WWOX in tumourigenesis is not yet fully defined. There is therefore a need to determine the normal function(s) of WWOX and how perturbation of these roles is likely to contribute to cancer. A model was previously established to examine the cellular function of the Drosophila orthologue, Wwox and to identify novel functional interactors. Loss of Wwox in Drosophila was not found to result in any obvious cellular dysfunction that manifested as a phenotype. The aim of this study was to identify the types of cellular dysfunction brought about by other genes that could be modulated by Wwox. As Wwox has previously been implicated in metabolic processes, particularly aerobic metabolism and redox homeostasis, an RNA interference (RNAi) screen was performed to identify the types of metabolic stress that can be modulated by altered Wwox levels. Wwox was found to regulate cellular homeostasis in cells with mitochondrial dysfunction, with a requirement for the active site of its shortchain dehydrogenase/reductase (SDR) enzyme. Other genetic effectors of the mitochondrial dysfunction were also identified as candidates for further investigation into the pathway(s) in which Wwox participates. The contributions of Wwox to two other models of cellular dysfunction were also examined. Wwox was found to have a role in a Drosophila model of intrinsic tumour suppression. In addition, Wwox was also shown to affect cells with chromosomal instability (CIN), with loss of Wwox resulting in oxidative stress, DNA damage and subsequently apoptosis of CIN cells. This study has identified roles for Wwox in three different novel models of cellular dysfunction. These findings provide further insight into the tumourigenic potential of WWOX and could contribute to the ultimate aim of designing therapeutics for treatment of cancers with low WWOX levels.