Any of us using the relevant RNAi stocks should be aware.
Vissers JH, Manning SA, Kulkarni A, Harvey KF. A Drosophila RNAi library
modulates Hippo pathway-dependent tissue growth. Nat Commun. 2016 Jan 13;7:10368.
From the abstract: "...
Here we investigate an important technical limitation with the widely
used VDRC KK RNAi collection. We find that approximately 25% of VDRC KK
RNAi lines cause false-positive enhancement of the Hippo pathway, owing
to ectopic expression of the Tiptop transcription factor. Of relevance
to the broader Drosophila community, ectopic tiptop (tio) expression can
also cause organ malformations and mask phenotypes such as organ
overgrowth. To enhance the use of the VDRC KK RNAi library, we have
generated a D. melanogaster strain that will allow researchers to test,
in a single cross, whether their genetic screen of interest will be
affected by ectopic tio expression."