It is recognized that in a number of different soma-derived human cancers, expression of genes typically restricted to germ cells can become reactivated, and amongst these are components of the PIWI-interacting RNA (piRNA) pathway. This phenomenon of germline gene re-expression has also been shown to occur in brain tumours in flies. Fagegaltier et al. used the model organism Drosophila melanogaster to demonstrate that overexpression of oncogenic RAS in combination with loss of the Hippo tumour suppressor pathway is sufficient to reactivate primary piRNA pathway genes in somatic cells. Inactivation of the piRNA pathway in these transformed somatic cells resulted in loss of transposon repression and a decrease in cell proliferation, two processes associated with oncogenesis. Subsequent work will need to address whether this observation translates to human tumours with RAS activation.
Fagegaltier, D. et al. Oncogenic transformation of Drosophila somatic cells induces a functional piRNA pathway. Genes Dev 30, 1623–1635 (2016)